• C. Trager-Cowan, A. Alasmari, W. Avis, J. Bruckbauer, P. R. Edwards, G. Ferenczi, B. Hourahine, A. Kotzai, S. Kraeusel, G. Kusch, R. W. Martin, R. McDermott, N. Gunasekar, M. Nouf-Allehiani, E. Pascal, D. Thomson, S. Vespucci, M. D. Smith, P. J. Parbrook, J. Enslin, F. Mehnke, C. Kuhn, T. Wernicke, M. Kneissl, S. Hagedorn, A. Knauer, S. Walde, M. Weyers, P. Coulon, P. Shields, J. Bai, Y. Gong, L. Jiu, Y. Zhang, R. Smith, T. Wang, and A. Winkelmann, “Structural and luminescence imaging and characterisation of semiconductors in the scanning electron microscope,” Semiconductor Science and Technology, vol. 35, p. 54001, 2020.
    [BibTeX] [Abstract] [Download PDF]

    The scanning electron microscopy techniques of electron backscatter diffraction (EBSD), electron channelling contrast imaging (ECCI) and hyperspectral cathodoluminescence imaging (CL) provide complementary information on the structural and luminescence properties of materials rapidly and non-destructively, with a spatial resolution of tens of nanometres. EBSD provides crystal orientation, crystal phase and strain analysis, whilst ECCI is used to determine the planar distribution of extended defects over a large area of a given sample. CL reveals the influence of crystal structure, composition and strain on intrinsic luminescence and/or reveals defect-related luminescence. Dark features are also observed in CL images where carrier recombination at defects is non-radiative. The combination of these techniques is a powerful approach to clarifying the role of crystallography and extended defects on a materials’ light emission properties. Here we describe the EBSD, ECCI and CL techniques and illustrate their use for investigating the structural and light emitting properties of UV-emitting nitride semiconductor structures. We discuss our investigations of the type, density and distribution of defects in GaN, AlN and AlGaN thin films and also discuss the determination of the polarity of GaN nanowires.

    @Article{strathprints71512,
    author = {Carol Trager-Cowan and Aeshah Alasmari and William Avis and Jochen Bruckbauer and Paul R. Edwards and Gergely Ferenczi and Benjamin Hourahine and Almpes Kotzai and Simon Kraeusel and Gunnar Kusch and Robert W. Martin and Ryan McDermott and Naresh Gunasekar and M. Nouf-Allehiani and Elena Pascal and David Thomson and Stefano Vespucci and Matthew David Smith and Peter J. Parbrook and Johannes Enslin and Frank Mehnke and Christian Kuhn and Tim Wernicke and Michael Kneissl and Sylvia Hagedorn and Arne Knauer and Sebastian Walde and Markus Weyers and Pierre-Marie Coulon and Philip Shields and J. Bai and Y. Gong and Ling Jiu and Y. Zhang and Richard Smith and Tao Wang and Aimo Winkelmann},
    journal = {Semiconductor Science and Technology},
    title = {Structural and luminescence imaging and characterisation of semiconductors in the scanning electron microscope},
    year = {2020},
    month = {February},
    pages = {054001},
    volume = {35},
    abstract = {The scanning electron microscopy techniques of electron backscatter diffraction (EBSD), electron channelling contrast imaging (ECCI) and hyperspectral cathodoluminescence imaging (CL) provide complementary information on the structural and luminescence properties of materials rapidly and non-destructively, with a spatial resolution of tens of nanometres. EBSD provides crystal orientation, crystal phase and strain analysis, whilst ECCI is used to determine the planar distribution of extended defects over a large area of a given sample. CL reveals the influence of crystal structure, composition and strain on intrinsic luminescence and/or reveals defect-related luminescence. Dark features are also observed in CL images where carrier recombination at defects is non-radiative. The combination of these techniques is a powerful approach to clarifying the role of crystallography and extended defects on a materials' light emission properties. Here we describe the EBSD, ECCI and CL techniques and illustrate their use for investigating the structural and light emitting properties of UV-emitting nitride semiconductor structures. We discuss our investigations of the type, density and distribution of defects in GaN, AlN and AlGaN thin films and also discuss the determination of the polarity of GaN nanowires.},
    keywords = {EBSD, nitride, scanning electron microscopy, Physics, Electronic, Optical and Magnetic Materials, Electrical and Electronic Engineering, Condensed Matter Physics},
    url = {https://strathprints.strath.ac.uk/71512/},
    }

  • C. Trager-Cowan, A. Alasmari, W. Avis, J. Bruckbauer, P. R. Edwards, B. Hourahine, S. Kraeusel, G. Kusch, R. Johnston, G. Naresh-Kumar, R. W. Martin, M. Nouf-Allehiani, E. Pascal, L. Spasevski, D. Thomson, S. Vespucci, P. J. Parbrook, M. D. Smith, J. Enslin, F. Mehnke, M. Kneissl, C. Kuhn, T. Wernicke, S. Hagedorn, S. Walde, M. Weyers, P. -M. Coulon, P. A. Shields, Y. Zhang, L. Jiu, Y. P. Gong, R. M. Smith, T. Wang, and A. Winkelmann, “The scanning electron microscope as a flexible tool for investigating the properties of UV-emitting nitride semiconductor thin films,” Photonics Research, vol. 7, iss. 11, p. B73–B82, 2019.
    [BibTeX] [Abstract] [Download PDF]

    In this article we describe the scanning electron microscopy techniques of electron backscatter diffraction (EBSD), electron channelling contrast imaging (ECCI), wavelength dispersive X-ray spectroscopy (WDX) and cathodoluminescence (CL) hyperspectral imaging. We present our recent results on the use of these non-destructive techniques to obtain information on the topography, crystal misorientation, defect distributions, composition, doping and light emission from a range of UV emitting nitride semiconductor structures. We aim to illustrate the developing capability of each of these techniques for understanding the properties of UV emitting nitride semiconductors, and the benefits were appropriate, in combining the techniques.

    @Article{strathprints69913,
    author = {C. Trager-Cowan and A. Alasmari and W. Avis and Jochen Bruckbauer and P. R. Edwards and B. Hourahine and S. Kraeusel and G. Kusch and R. Johnston and G. Naresh-Kumar and R. W. Martin and M. Nouf-Allehiani and E. Pascal and L. Spasevski and D. Thomson and S. Vespucci and P. J. Parbrook and M. D. Smith and J. Enslin and F. Mehnke and M. Kneissl and C. Kuhn and T. Wernicke and S. Hagedorn and S. Walde and M. Weyers and P.-M. Coulon and P. A. Shields and Y. Zhang and L. Jiu and Y. P. Gong and R. M. Smith and T. Wang and A. Winkelmann},
    title = {The scanning electron microscope as a flexible tool for investigating the properties of {UV}-emitting nitride semiconductor thin films},
    journal = {Photonics Research},
    year = {2019},
    volume = {7},
    number = {11},
    pages = {B73--B82},
    month = {September},
    abstract = {In this article we describe the scanning electron microscopy techniques of electron backscatter diffraction (EBSD), electron channelling contrast imaging (ECCI), wavelength dispersive X-ray spectroscopy (WDX) and cathodoluminescence (CL) hyperspectral imaging. We present our recent results on the use of these non-destructive techniques to obtain information on the topography, crystal misorientation, defect distributions, composition, doping and light emission from a range of UV emitting nitride semiconductor structures. We aim to illustrate the developing capability of each of these techniques for understanding the properties of UV emitting nitride semiconductors, and the benefits were appropriate, in combining the techniques.},
    keywords = {scanning electron microscopy, electron backscatter diffraction, non-destructive techniques, UV emitting nitride semiconductors, Physics, Atomic and Molecular Physics, and Optics},
    url = {https://strathprints.strath.ac.uk/69913/},
    }

  • G. Kusch, M. Conroy, H. Li, P. R. Edwards, C. Zhao, B. S. Ooi, J. Pugh, M. J. Cryan, P. J. Parbrook, and R. W. Martin, “Multi-wavelength emission from a single InGaN/GaN nanorod analyzed by cathodoluminescence hyperspectral imaging,” Scientific Reports, vol. 8, p. 1742, 2018.
    [BibTeX] [Abstract] [Download PDF]

    Multiple luminescence peaks emitted by a single InGaN/GaN quantum-well (QW) nanorod, extending from the blue to the red, were analysed by a combination of electron microscope based imaging techniques. Utilizing the capability of cathodoluminescence hyperspectral imaging it was possible to investigate spatial variations in the luminescence properties on a nanoscale. The high optical quality of a single GaN nanorod was demonstrated, evidenced by a narrow band-edge peak and the absence of any luminescence associated with the yellow defect band. Additionally two spatially confined broad luminescence bands were observed, consisting of multiple peaks ranging from 395nm to 480nm and 490nm to 650 nm. The lower energy band originates from broad c-plane QWs located at the apex of the nanorod and the higher energy band from the semipolar QWs on the pyramidal nanorod tip. Comparing the experimentally observed peak positions with peak positions obtained from plane wave modelling and 3D finite difference time domain (FDTD) modelling shows modulation of the nanorod luminescence by cavity modes. By studying the influence of these modes we demonstrate that this can be exploited as an additional parameter in engineering the emission profile of LEDs.

    @Article{strathprints62810,
    author = {Gunnar Kusch and Michele Conroy and Haoning Li and Paul R. Edwards and Chao Zhao and Boon S. Ooi and Jon Pugh and Martin J. Cryan and Peter J. Parbrook and Robert W. Martin},
    title = {Multi-wavelength emission from a single InGaN/GaN nanorod analyzed by cathodoluminescence hyperspectral imaging},
    journal = {Scientific Reports},
    year = {2018},
    volume = {8},
    pages = {1742},
    month = {January},
    abstract = {Multiple luminescence peaks emitted by a single InGaN/GaN quantum-well (QW) nanorod, extending from the blue to the red, were analysed by a combination of electron microscope based imaging techniques. Utilizing the capability of cathodoluminescence hyperspectral imaging it was possible to investigate spatial variations in the luminescence properties on a nanoscale. The high optical quality of a single GaN nanorod was demonstrated, evidenced by a narrow band-edge peak and the absence of any luminescence associated with the yellow defect band. Additionally two spatially confined broad luminescence bands were observed, consisting of multiple peaks ranging from 395nm to 480nm and 490nm to 650 nm. The lower energy band originates from broad c-plane QWs located at the apex of the nanorod and the higher energy band from the semipolar QWs on the pyramidal nanorod tip. Comparing the experimentally observed peak positions with peak positions obtained from plane wave modelling and 3D finite difference time domain (FDTD) modelling shows modulation of the nanorod luminescence by cavity modes. By studying the influence of these modes we demonstrate that this can be exploited as an additional parameter in engineering the emission profile of LEDs.},
    keywords = {luminescence, InGaN/GaN quantum-well, nanorods, hyperspectral imaging, LEDs, Optics. Light, Atomic and Molecular Physics, and Optics},
    url = {https://strathprints.strath.ac.uk/62810/}
    }

  • M. D. Smith, D. Thomson, V. Z. Zubialevich, H. Li, G. Naresh-Kumar, C. Trager-Cowan, and P. J. Parbrook, “Nanoscale fissure formation in AlₓGa₁₋ₓN/GaN heterostructures and their influence on Ohmic contact formation,” Physica Status Solidi A, vol. 214, iss. 1, p. 1600353, 2017.
    [BibTeX] [Abstract] [Download PDF]

    Nanoscale surface fissures on AlₓGa₁₋ₓN/GaN (15 nm/1 ?m) heterostructures grown by metalorganic vapour phase epitaxy (MOVPE) were imaged using tapping-mode atomic force microscopy (AFM) and electron channelling contrast imaging (ECCI). Fissure formation was linked to threading dislocations, and was only observed in samples cooled under H2 and NH3, developing with increasing barrier layer Al content. No strain relaxation was detected regardless of fissure formation up to barrier layer Al composition fractions of x = 0.37. A reduction of measured channel carrier density was found in fissured samples at low temperature. This instability is attributed to shallow trap formation associated with fissure boundaries. For Ti/Al/Ni/Au Ohmic contact formation to high Al content barrier layers, fissures were found to offer conduction routes to the 2DEG that allow for low resistance contacts, with fissure-free samples requiring additional optimisation of the metal stack and anneal conditions to achieve contact resistivity of order those measured in fissured samples. In addition, the effects of fissures were found to be detrimental to thermal stability of sheet and contact resistance, suggesting that fissure formation compromises the integrity of the 2DEG.

    @Article{strathprints59478,
    author = {M. D. Smith and D. Thomson and V. Z. Zubialevich and H. Li and G. Naresh-Kumar and C. Trager-Cowan and P. J. Parbrook},
    title = {Nanoscale fissure formation in {AlₓGa₁₋ₓN/GaN} heterostructures and their influence on {O}hmic contact formation},
    journal = {Physica Status Solidi A},
    year = {2017},
    volume = {214},
    number = {1},
    pages = {1600353},
    month = {January},
    abstract = {Nanoscale surface fissures on AlₓGa₁₋ₓN/GaN (15 nm/1 ?m) heterostructures grown by metalorganic vapour phase epitaxy (MOVPE) were imaged using tapping-mode atomic force microscopy (AFM) and electron channelling contrast imaging (ECCI). Fissure formation was linked to threading dislocations, and was only observed in samples cooled under H2 and NH3, developing with increasing barrier layer Al content. No strain relaxation was detected regardless of fissure formation up to barrier layer Al composition fractions of x = 0.37. A reduction of measured channel carrier density was found in fissured samples at low temperature. This instability is attributed to shallow trap formation associated with fissure boundaries. For Ti/Al/Ni/Au Ohmic contact formation to high Al content barrier layers, fissures were found to offer conduction routes to the 2DEG that allow for low resistance contacts, with fissure-free samples requiring additional optimisation of the metal stack and anneal conditions to achieve contact resistivity of order those measured in fissured samples. In addition, the effects of fissures were found to be detrimental to thermal stability of sheet and contact resistance, suggesting that fissure formation compromises the integrity of the 2DEG.},
    keywords = {nanoscale surface fissures, electron channelling, contrast imaging, AlxGa1?xN/GaN, Physics, Physics and Astronomy(all)},
    url = {http://strathprints.strath.ac.uk/59478/}
    }

  • M. Conroy, H. Li, V. Z. Zubialevich, G. Kusch, M. Schmidt, T. Collins, C. Glynn, R. W. Martin, C. O’Dwyer, J. D. Holmes, P. J. Parbrook, and M. D. Morris, “Self-healing thermal annealing : surface morphological restructuring control of GaN nanorods,” Crystal Growth and Design, vol. 16, iss. 12, p. 6769–6775, 2016.
    [BibTeX] [Abstract] [Download PDF]

    With advances in nanolithography and dry etching, top-down methods of nanostructuring have become a widely used tool for improving the efficiency of optoelectronics. These nano dimensions can offer various benefits to the device performance in terms of light extraction and efficiency, but often at the expense of emission color quality. Broadening of the target emission peak and unwanted yellow luminescence are characteristic defect-related effects due to the ion beam etching damage, particularly for III?N based materials. In this article we focus on GaN based nanorods, showing that through thermal annealing the surface roughness and deformities of the crystal structure can be ?self-healed?. Correlative electron microscopy and atomic force microscopy show the change from spherical nanorods to faceted hexagonal structures, revealing the temperature-dependent surface morphology faceting evolution. The faceted nanorods were shown to be strain- and defect-free by cathodoluminescence hyperspectral imaging, micro-Raman, and transmission electron microscopy (TEM). In-situ TEM thermal annealing experiments allowed for real time observation of dislocation movements and surface restructuring observed in ex-situ annealing TEM sampling. This thermal annealing investigation gives new insight into the redistribution path of GaN material and dislocation movement post growth, allowing for improved understanding and in turn advances in optoelectronic device processing of compound semiconductors.

    @article{strathprints60967,
    volume = {16},
    number = {12},
    month = {December},
    author = {Michelle Conroy and Haoning Li and Vitaly Z. Zubialevich and Gunnar Kusch and Michael Schmidt and Timothy Collins and Colm Glynn and Robert W. Martin and Colm O'Dwyer and Justin D. Holmes and Peter J. Parbrook and Michael D. Morris},
    note = {This document is the Accepted Manuscript version of a Published Work that appeared in final form in Crystal Growth and Design, copyright {\copyright} American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see https://doi.org/10.1021/acs.cgd.6b00756},
    title = {Self-healing thermal annealing : surface morphological restructuring control of GaN nanorods},
    year = {2016},
    journal = {Crystal Growth and Design},
    pages = {6769--6775},
    keywords = {nanolithography, nanostructuring, nanorods, thermal annealing, self-healing, gallium nitride, cathodoluminescence hyperspectral imaging, micro-Raman, Physics, Materials Science(all), Chemistry(all), Condensed Matter Physics},
    url = {http://strathprints.strath.ac.uk/60967/},
    abstract = {With advances in nanolithography and dry etching, top-down methods of nanostructuring have become a widely used tool for improving the efficiency of optoelectronics. These nano dimensions can offer various benefits to the device performance in terms of light extraction and efficiency, but often at the expense of emission color quality. Broadening of the target emission peak and unwanted yellow luminescence are characteristic defect-related effects due to the ion beam etching damage, particularly for III?N based materials. In this article we focus on GaN based nanorods, showing that through thermal annealing the surface roughness and deformities of the crystal structure can be ?self-healed?. Correlative electron microscopy and atomic force microscopy show the change from spherical nanorods to faceted hexagonal structures, revealing the temperature-dependent surface morphology faceting evolution. The faceted nanorods were shown to be strain- and defect-free by cathodoluminescence hyperspectral imaging, micro-Raman, and transmission electron microscopy (TEM). In-situ TEM thermal annealing experiments allowed for real time observation of dislocation movements and surface restructuring observed in ex-situ annealing TEM sampling. This thermal annealing investigation gives new insight into the redistribution path of GaN material and dislocation movement post growth, allowing for improved understanding and in turn advances in optoelectronic device processing of compound semiconductors.}
    }

  • M. Conroy, H. Li, G. Kusch, C. Zhao, B. Ooi, P. R. Edwards, R. W. Martin, J. D. Holmes, and P. J. Parbrook, “Correction: Site controlled red-yellow-green light emitting InGaN quantum discs on nano-tipped GaN rods,” Nanoscale, vol. 8, iss. 27, p. 13521, 2016.
    [BibTeX] [Abstract] [Download PDF]

    Correction for ‘Site controlled red-yellow-green light emitting InGaN quantum discs on nano-tipped GaN rods’ by M. Conroy et al., Nanoscale, 2016, 8 , 11019-11026.

    @Article{strathprints57022,
    author = {M. Conroy and H. Li and G. Kusch and C. Zhao and B. Ooi and P. R. Edwards and R. W. Martin and J. D. Holmes and P. J. Parbrook},
    title = {Correction: {S}ite controlled red-yellow-green light emitting {InGaN} quantum discs on nano-tipped {GaN} rods},
    journal = {Nanoscale},
    year = {2016},
    volume = {8},
    number = {27},
    pages = {13521},
    month = {July},
    abstract = {Correction for 'Site controlled red-yellow-green light emitting InGaN quantum discs on nano-tipped GaN rods' by M. Conroy et al., Nanoscale, 2016, 8 , 11019-11026.},
    keywords = {InGaN quantum discs, nano-tipped GaN rods, nanorods, electron microscopy, energy-dispersive x-ray, cathodoluminescence, Solid state physics. Nanoscience, Materials Science(all)},
    url = {http://strathprints.strath.ac.uk/57022/}
    }

  • M. Conroy, H. Li, G. Kusch, C. Zhao, B. Ooi, P. R. Edwards, R. W. Martin, J. D. Holmes, and P. J. Parbrook, “Site controlled red-yellow-green light emitting InGaN quantum discs on nano-tipped GaN rods,” Nanoscale, vol. 8, iss. 21, p. 11019–11026, 2016.
    [BibTeX] [Abstract] [Download PDF]

    We report a method of growing site controlled InGaN multiple quantum discs (QDs) at uniform wafer scale on coalescence free ultra-high density ({\ensuremath{>}}80\%) nanorod templates by metal organic chemical vapour deposition (MOCVD). The dislocation and coalescence free nature of the GaN space filling nanorod arrays eliminates the well-known emission problems seen in InGaN based visible light sources that these types of crystallographic defects cause. Correlative scanning transmission electron microscopy (STEM), energy-dispersive X-ray (EDX) mapping and cathodoluminescence (CL) hyperspectral imaging illustrates the controlled site selection of the red, yellow and green (RYG) emission at these nano tips. This article reveals that the nanorod tips? broad emission in the RYG visible range is in fact achieved by manipulating the InGaN QD?s confinement dimensions, rather than significantly increasing the In\%. This article details the easily controlled method of manipulating the QDs dimensions producing high crystal quality InGaN without complicated growth conditions needed for strain relaxation and alloy compositional changes seen for bulk planar GaN templates.

    @Article{strathprints56549,
    author = {M. Conroy and H. Li and G. Kusch and C. Zhao and B. Ooi and P. R. Edwards and R. W. Martin and J. D. Holmes and P. J. Parbrook},
    title = {Site controlled red-yellow-green light emitting {InGaN} quantum discs on nano-tipped {GaN} rods},
    journal = {Nanoscale},
    year = {2016},
    volume = {8},
    number = {21},
    pages = {11019--11026},
    month = {May},
    abstract = {We report a method of growing site controlled InGaN multiple quantum discs (QDs) at uniform wafer scale on coalescence free ultra-high density ({\ensuremath{>}}80\%) nanorod templates by metal organic chemical vapour deposition (MOCVD). The dislocation and coalescence free nature of the GaN space filling nanorod arrays eliminates the well-known emission problems seen in InGaN based visible light sources that these types of crystallographic defects cause. Correlative scanning transmission electron microscopy (STEM), energy-dispersive X-ray (EDX) mapping and cathodoluminescence (CL) hyperspectral imaging illustrates the controlled site selection of the red, yellow and green (RYG) emission at these nano tips. This article reveals that the nanorod tips? broad emission in the RYG visible range is in fact achieved by manipulating the InGaN QD?s confinement dimensions, rather than significantly increasing the In\%. This article details the easily controlled method of manipulating the QDs dimensions producing high crystal quality InGaN without complicated growth conditions needed for strain relaxation and alloy compositional changes seen for bulk planar GaN templates.},
    keywords = {InGaN quantum discs, nano-tipped GaN rods, nanorods, electron microscopy, energy-dispersive x-ray, cathodoluminescence, Solid state physics. Nanoscience, Materials Science(all)},
    url = {http://strathprints.strath.ac.uk/56549/}
    }

  • E. Taylor, M. D. Smith, T. C. Sadler, K. Lorenz, H. N. Li, E. Alves, P. J. Parbrook, and R. W. Martin, “Structural and optical properties of Ga auto-incorporated InAlN epilayers,” Journal of Crystal Growth, vol. 408, p. 97–101, 2014.
    [BibTeX] [Abstract] [Download PDF]

    InAlN epilayers deposited on thick GaN buffer layers grown by metalorganic chemical vapour deposition (MOCVD) revealed an auto-incorporation of Ga when analysed by wavelength dispersive x-ray (WDX) spectroscopy and Rutherford backscattering spectrometry (RBS). Samples were grown under similar conditions with the change in reactor flow rate resulting in varying Ga contents of 12-24\%. The increase in flow rate from 8000 to 24 000 sccm suppressed the Ga auto-incorporation which suggests that the likely cause is from residual Ga left behind from previous growth runs. The luminescence properties of the resultant InAlGaN layers were investigated using cathodoluminescence (CL) measurements.

    @Article{strathprints49667,
    author = {E. Taylor and M.D. Smith and T.C. Sadler and K. Lorenz and H.N. Li and E. Alves and P.J. Parbrook and R.W. Martin},
    title = {Structural and optical properties of {Ga} auto-incorporated {InAlN} epilayers},
    journal = {Journal of Crystal Growth},
    year = {2014},
    volume = {408},
    pages = {97--101},
    month = {December},
    abstract = {InAlN epilayers deposited on thick GaN buffer layers grown by metalorganic chemical vapour deposition (MOCVD) revealed an auto-incorporation of Ga when analysed by wavelength dispersive x-ray (WDX) spectroscopy and Rutherford backscattering spectrometry (RBS). Samples were grown under similar conditions with the change in reactor flow rate resulting in varying Ga contents of 12-24\%. The increase in flow rate from 8000 to 24 000 sccm suppressed the Ga auto-incorporation which suggests that the likely cause is from residual Ga left behind from previous growth runs. The luminescence properties of the resultant InAlGaN layers were investigated using cathodoluminescence (CL) measurements.},
    keywords = {metalorganic chemical vapour deposition, wavelength dispersive x-ray, Rutherford backscattering spectrometry, InAlN, InAlGaN, Ga incorporation, MOCVD, Physics, Chemical engineering, Materials Chemistry, Inorganic Chemistry, Condensed Matter Physics},
    url = {http://strathprints.strath.ac.uk/49667/}
    }

  • C. Trager-Cowan, G. Naresh-Kumar, N. Allehiani, S. Kraeusel, B. Hourahine, S. Vespucci, D. Thomson, J. Bruckbauer, G. Kusch, P. R. Edwards, R. W. Martin, C. Mauder, A. P. Day, A. Winkelmann, A. Vilalta-Clemente, A. J. Wilkinson, P. J. Parbrook, M. J. Kappers, M. A. Moram, R. A. Oliver, C. J. Humphreys, P. Shields, L. E. D. Boulbar, D. Maneuski, V. O’Shea, and K. P. Mingard, “Electron channeling contrast imaging of defects in III-nitride semiconductors,” Microscopy and Microanalysis, vol. 20, iss. S3, p. 1024–1025, 2014.
    [BibTeX] [Download PDF]
    @Article{strathprints49409,
    author = {C. Trager-Cowan and G. Naresh-Kumar and N. Allehiani and S. Kraeusel and B. Hourahine and S. Vespucci and D. Thomson and J. Bruckbauer and G. Kusch and P. R. Edwards and R. W. Martin and C. Mauder and A. P. Day and A. Winkelmann and A. Vilalta-Clemente and A. J. Wilkinson and P. J. Parbrook and M. J. Kappers and M. A. Moram and R. A. Oliver and C. J. Humphreys and P. Shields and E. D. Le Boulbar and D. Maneuski and V. O'Shea and K. P. Mingard},
    title = {Electron channeling contrast imaging of defects in {III}-nitride semiconductors},
    journal = {Microscopy and Microanalysis},
    year = {2014},
    volume = {20},
    number = {S3},
    pages = {1024--1025},
    month = {August},
    keywords = {Physics, Instrumentation},
    url = {http://strathprints.strath.ac.uk/49409/}
    }

  • G. Kusch, H. Li, P. R. Edwards, J. Bruckbauer, T. C. Sadler, P. J. Parbrook, and R. W. Martin, “Influence of substrate miscut angle on surface morphology and luminescence properties of AlGaN,” Applied Physics Letters, vol. 104, iss. 9, p. 92114, 2014.
    [BibTeX] [Abstract] [Download PDF]

    The influence of substrate miscut on Al0.5Ga0.5 N layers was investigated using cathodoluminescence (CL) hyperspectral imaging and secondary electron imaging in an environmental scanning electron microscope. The samples were also characterized using atomic force microscopy and high resolution X-ray diffraction. It was found that small changes in substrate miscut have a strong influence on the morphology and luminescence properties of the AlGaN layers. Two different types are resolved. For low miscut angle, a crack-free morphology consisting of randomly sized domains is observed, between which there are notable shifts in the AlGaN near band edge emission energy. For high miscut angle, a morphology with step bunches and compositional inhomogeneities along the step bunches, evidenced by an additional CL peak along the step bunches, are observed.

    @Article{strathprints47137,
    author = {Gunnar Kusch and Haoning Li and Paul R. Edwards and Jochen Bruckbauer and Thomas C. Sadler and Peter J. Parbrook and Robert W. Martin},
    title = {Influence of substrate miscut angle on surface morphology and luminescence properties of AlGaN},
    journal = {Applied Physics Letters},
    year = {2014},
    volume = {104},
    number = {9},
    pages = {092114},
    month = {March},
    abstract = {The influence of substrate miscut on Al0.5Ga0.5 N layers was investigated using cathodoluminescence (CL) hyperspectral imaging and secondary electron imaging in an environmental scanning electron microscope. The samples were also characterized using atomic force microscopy and high resolution X-ray diffraction. It was found that small changes in substrate miscut have a strong influence on the morphology and luminescence properties of the AlGaN layers. Two different types are resolved. For low miscut angle, a crack-free morphology consisting of randomly sized domains is observed, between which there are notable shifts in the AlGaN near band edge emission energy. For high miscut angle, a morphology with step bunches and compositional inhomogeneities along the step bunches, evidenced by an additional CL peak along the step bunches, are observed.},
    keywords = {cathodoluminescence, III-V semiconductors, surface morphology, X-ray diffraction, Physics, Physics and Astronomy(all)},
    url = {http://strathprints.strath.ac.uk/47137/}
    }

  • M. D. Smith, E. Taylor, T. C. Sadler, V. Z. Zubialevich, K. Lorenz, H. N. Li, J. O’Connell, E. Alves, J. D. Holmes, R. W. Martin, and P. J. Parbrook, “Determination of Ga auto-incorporation in nominal InAlN epilayers grown by MOCVD,” Journal of Materials Chemistry. C, vol. 2, iss. 29, p. 5787–5792, 2014.
    [BibTeX] [Abstract] [Download PDF]

    We report on the consistent measurement of gallium incorporation in nominal InAlN layers using various complimentary techniques, underpinned by X-ray diffraction. Nominal InAlN layers with similar growth conditions were prepared, and the change in unintended Ga content in the group III sublattice ranged from similar to 24\% to similar to 12\% when the total reactor flow rate was increased from 8000 to 24 000 standard cubic centimetres per minute. Ultra-thin InAlN/GaN HEMT layers were grown in a clean reactor to minimize Ga auto-incorporation, and measured using X-ray photoelectron spectroscopy and secondary ion mass spectrometry. The implications of Ga incorporation in InAlN layers within optoelectronic and power devices is discussed.

    @article{strathprints51372,
    volume = {2},
    number = {29},
    title = {Determination of Ga auto-incorporation in nominal InAlN epilayers grown by MOCVD},
    author = {M. D. Smith and E. Taylor and T. C. Sadler and V. Z. Zubialevich and K. Lorenz and H. N. Li and J. O'Connell and E. Alves and J. D. Holmes and R. W. Martin and P. J. Parbrook},
    year = {2014},
    pages = {5787--5792},
    journal = {Journal of Materials Chemistry. C},
    keywords = {auto-incorporation, epilayers, gallium, InAlN, GaN, Physical and theoretical chemistry, Solid state physics. Nanoscience, Physical and Theoretical Chemistry},
    url = {http://strathprints.strath.ac.uk/51372/},
    abstract = {We report on the consistent measurement of gallium incorporation in nominal InAlN layers using various complimentary techniques, underpinned by X-ray diffraction. Nominal InAlN layers with similar growth conditions were prepared, and the change in unintended Ga content in the group III sublattice ranged from similar to 24\% to similar to 12\% when the total reactor flow rate was increased from 8000 to 24 000 standard cubic centimetres per minute. Ultra-thin InAlN/GaN HEMT layers were grown in a clean reactor to minimize Ga auto-incorporation, and measured using X-ray photoelectron spectroscopy and secondary ion mass spectrometry. The implications of Ga incorporation in InAlN layers within optoelectronic and power devices is discussed.}
    }

  • S. Schulz, M. A. Caro, L. -T. Tan, P. J. Parbrook, R. W. Martin, and E. P. O’Reilly, “Composition-dependent band gap and band-edge bowing in AIInN : a combined theoretical and experimental study,” Applied Physics Express, vol. 6, iss. 12, p. 121001, 2013.
    [BibTeX] [Abstract] [Download PDF]

    A combined experimental and theoretical study of the band gap of AllnN is presented, which confirms the breakdown of the virtual crystal approximation (VCA) for the conduction and valence band edges. Composition-dependent bowing parameters for these quantities are extracted. Additionally, composition-dependent band offsets for GaN/AllnN systems are provided. We show that local strain and built-in fields affect the band edges significantly, leading to optical polarization switching at a much lower In composition than expected from a VCA approach.

    @Article{strathprints47231,
    author = {S. Schulz and M.A. Caro and L.-T. Tan and P.J. Parbrook and R.W. Martin and E.P. O'Reilly},
    title = {Composition-dependent band gap and band-edge bowing in AIInN : a combined theoretical and experimental study},
    journal = {Applied Physics Express},
    year = {2013},
    volume = {6},
    number = {12},
    pages = {121001},
    month = {December},
    abstract = {A combined experimental and theoretical study of the band gap of AllnN is presented, which confirms the breakdown of the virtual crystal approximation (VCA) for the conduction and valence band edges. Composition-dependent bowing parameters for these quantities are extracted. Additionally, composition-dependent band offsets for GaN/AllnN systems are provided. We show that local strain and built-in fields affect the band edges significantly, leading to optical polarization switching at a much lower In composition than expected from a VCA approach.},
    keywords = {composition-dependent, band gap, band-edge, bowing, AlInN, experimental study, Physics, Physics and Astronomy(all), Engineering(all)},
    url = {http://strathprints.strath.ac.uk/47231/}
    }

  • V. Kachkanov, I. Dobnya, K. O’Donnell, K. Lorenz, S. M. de Sousa Pereira, I. Watson, T. Sadler, H. Li, V. Zubialevich, and P. Parbrook, “Characterisation of III-nitride materials by synchrotron X-ray microdiffraction reciprocal space mapping,” Physica Status Solidi C, vol. 10, iss. 3, p. 481–485, 2013.
    [BibTeX] [Abstract] [Download PDF]

    X-ray Reciprocal Space Mapping (RSM) is a powerful tool to explore the structure of semiconductor materials. However, conventional lab-based RSMs are usually measured in two dimensions (2D) ignoring the third dimension of diffraction-space volume. We report the use of a combination of X-ray microfocusing and state-of-the-art 2D area detectors to study the full volume of diffraction?space while probing III-nitride materials on the microscale.

    @Article{strathprints42828,
    author = {V. Kachkanov and Igor Dobnya and Kevin O'Donnell and Katharina Lorenz and de Sousa Pereira, Sergio Manuel and Ian Watson and Thomas Sadler and Haoning Li and Vitaly Zubialevich and Peter Parbrook},
    title = {Characterisation of III-nitride materials by synchrotron X-ray microdiffraction reciprocal space mapping},
    journal = {Physica Status Solidi C},
    year = {2013},
    volume = {10},
    number = {3},
    pages = {481--485},
    month = {March},
    abstract = {X-ray Reciprocal Space Mapping (RSM) is a powerful tool to explore the structure of semiconductor materials. However, conventional lab-based RSMs are usually measured in two dimensions (2D) ignoring the third dimension of diffraction-space volume. We report the use of a combination of X-ray microfocusing and state-of-the-art 2D area detectors to study the full volume of diffraction?space while probing III-nitride materials on the microscale.},
    keywords = {X-ray microdiffraction, eciprocal space mapping, synchrotron radiation, nitride materials, Physics, Condensed Matter Physics},
    url = {http://strathprints.strath.ac.uk/42828/}
    }

  • G. Naresh-Kumar, B. Hourahine, A. Vilalta-Clemente, P. Ruterana, P. Gamarra, C. Lacam, M. Tordjman, M. A. di Forte-Poisson, P. J. Parbrook, A. P. Day, G. England, and C. Trager-Cowan, “Imaging and identifying defects in nitride semiconductor thin films using a scanning electron microscope,” Physica Status Solidi A, vol. 209, iss. 3, p. 424–426, 2012.
    [BibTeX] [Abstract] [Download PDF]

    We describe the use of electron channelling contrast imaging (ECCI) ? in a field emission scanning electron microscope ? to reveal and identify defects in nitride semiconductor thin films. In ECCI changes in crystallographic orientation, or changes in lattice constant due to local strain, are revealed by changes in grey scale in an image constructed by monitoring the intensity of backscattered electrons as an electron beam is scanned over a suitably oriented sample. Extremely small orientation changes are detectable, enabling small angle tilt and rotation boundaries and dislocations to be imaged. Images with a resolution of tens of nanometres are obtainable with ECCI. In this paper we describe the use of ECCI with TEM to determine threading dislocation densities and types in InAlN/GaN heterostructures grown on SiC and sapphire substrates.

    @article{strathprints35178,
    volume = {209},
    number = {3},
    month = {March},
    author = {G. Naresh-Kumar and Benjamin Hourahine and A. Vilalta-Clemente and P. Ruterana and P. Gamarra and C. Lacam and M. Tordjman and M. A. di Forte-Poisson and P. J. Parbrook and A. P. Day and G. England and Carol Trager-Cowan},
    title = {Imaging and identifying defects in nitride semiconductor thin films using a scanning electron microscope},
    journal = {Physica Status Solidi A},
    pages = {424--426},
    year = {2012},
    keywords = {dislocations, electron channelling , SEM, Solid state physics. Nanoscience, Materials Chemistry, Surfaces, Coatings and Films, Surfaces and Interfaces, Electronic, Optical and Magnetic Materials, Electrical and Electronic Engineering, Condensed Matter Physics},
    url = {http://strathprints.strath.ac.uk/35178/},
    abstract = {We describe the use of electron channelling contrast imaging (ECCI) ? in a field emission scanning electron microscope ? to reveal and identify defects in nitride semiconductor thin films. In ECCI changes in crystallographic orientation, or changes in lattice constant due to local strain, are revealed by changes in grey scale in an image constructed by monitoring the intensity of backscattered electrons as an electron beam is scanned over a suitably oriented sample. Extremely small orientation changes are detectable, enabling small angle tilt and rotation boundaries and dislocations to be imaged. Images with a resolution of tens of nanometres are obtainable with ECCI. In this paper we describe the use of ECCI with TEM to determine threading dislocation densities and types in InAlN/GaN heterostructures grown on SiC and sapphire substrates.}
    }

  • N. Gunasekar, B. Hourahine, P. Edwards, A. P. Day, A. Winkelmann, A. J. Wilkinson, P. J. Parbrook, G. England, and C. Trager-Cowan, “Rapid nondestructive analysis of threading dislocations in wurtzite materials using the scanning electron microscope,” Physical Review Letters, vol. 108, iss. 13, p. 135503, 2012.
    [BibTeX] [Abstract] [Download PDF]

    We describe the use of electron channeling contrast imaging in the scanning electron microscope to rapidly and reliably image and identify threading dislocations (TDs) in materials with the wurtzite crystal structure. In electron channeling contrast imaging, vertical TDs are revealed as spots with black-white contrast. We have developed a simple geometric procedure which exploits the differences observed in the direction of this black-white contrast for screw, edge, and mixed dislocations for two electron channeling contrast images acquired from two symmetrically equivalent crystal planes whose g vectors are at 120? to each other. Our approach allows unambiguous identification of all TDs without the need to compare results with dynamical simulations of channeling contrast.

    @Article{strathprints39229,
    author = {Naresh Gunasekar and Benjamin Hourahine and Paul Edwards and A.P. Day and Aimo Winkelmann and A.J. Wilkinson and P.J. Parbrook and G. England and Carol Trager-Cowan},
    title = {Rapid nondestructive analysis of threading dislocations in wurtzite materials using the scanning electron microscope},
    journal = {Physical Review Letters},
    year = {2012},
    volume = {108},
    number = {13},
    pages = {135503},
    month = {March},
    abstract = {We describe the use of electron channeling contrast imaging in the scanning electron microscope to rapidly and reliably image and identify threading dislocations (TDs) in materials with the wurtzite crystal structure. In electron channeling contrast imaging, vertical TDs are revealed as spots with black-white contrast. We have developed a simple geometric procedure which exploits the differences observed in the direction of this black-white contrast for screw, edge, and mixed dislocations for two electron channeling contrast images acquired from two symmetrically equivalent crystal planes whose g vectors are at 120? to each other. Our approach allows unambiguous identification of all TDs without the need to compare results with dynamical simulations of channeling contrast.},
    keywords = {wurtzite , nondestructive analysis , scanning electron microscope, Solid state physics. Nanoscience, Physics and Astronomy(all)},
    url = {http://strathprints.strath.ac.uk/39229/}
    }

  • C. Trager-Cowan, N. Gunasekar, B. Hourahine, P. Edwards, J. Bruckbauer, R. Martin, C. Mauder, A. Day, G. England, A. Winkelmann, P. Parbrook, and A. Wilkinson, “Applications of electron channeling contrast imaging for characterizing nitride semiconductor thin films,” Microscopy and Microanalysis, vol. 18, iss. S2, p. 684–685, 2012.
    [BibTeX] [Abstract] [Download PDF]

    We are now all familiar with the bright blue, green and white LEDs that light up our electronic appliances; decorate our streets and buildings and illuminate airport runways. However, the ultimate performance of these nitride semiconductor based LEDs is limited by extended defects such as threading dislocations (TDs), partial dislocations (PDs) and stacking faults (SFs). If we want to develop LEDs to be an effective replacement for the light bulb, or have sufficient power to purify water; we need to eliminate these defects as they act as scattering centres for light and charge carriers and give rise to nonradiative recombination and to leakage currents, severely limiting device performance. The capability to rapidly detect and analyze TDs, PDs and SFs, with negligible sample preparation, represents a real step forward in the development of more efficient nitride-based semiconductor devices

    @article{strathprints44510,
    volume = {18},
    number = {S2},
    author = {Carol Trager-Cowan and Naresh Gunasekar and Benjamin Hourahine and Paul Edwards and Jochen Bruckbauer and Robert Martin and Christof Mauder and Austin Day and Gordon England and Aimo Winkelmann and Peter Parbrook and Anjus Wilkinson},
    note = {Extended abstract of a paper presented at Microscopy and Microanalysis 2012 in Phoenix, Arizona, USA, July 29 ? August 2, 2012.},
    title = {Applications of electron channeling contrast imaging for characterizing nitride semiconductor thin films},
    journal = {Microscopy and Microanalysis},
    pages = {684--685},
    year = {2012},
    keywords = {semiconductor thin films , electron channeling, nanotechnology, Microbiology, Physics, Biotechnology},
    url = {http://strathprints.strath.ac.uk/44510/},
    abstract = {We are now all familiar with the bright blue, green and white LEDs that light up our electronic appliances; decorate our streets and buildings and illuminate airport runways. However, the ultimate performance of these nitride semiconductor based LEDs is limited by extended defects such as threading dislocations (TDs), partial dislocations (PDs) and stacking faults (SFs). If we want to develop LEDs to be an effective replacement for the light bulb, or have sufficient power to purify water; we need to eliminate these defects as they act as scattering centres for light and charge carriers and give rise to nonradiative recombination and to leakage currents, severely limiting device performance. The capability to rapidly detect and analyze TDs, PDs and SFs, with negligible sample preparation, represents a real step forward in the development of more efficient nitride-based semiconductor devices}
    }

  • C. Trager-Cowan, F. Sweeney, P. W. Trimby, A. P. Day, A. Gholinia, N. -H. Schmidt, P. J. Parbrook, A. J. Wilkinson, and I. M. Watson, “Electron backscatter diffraction and electron channeling contrast imaging of tilt and dislocations in nitride thin films,” Physical Review B, vol. 75, iss. 8, p. 85301, 2007.
    [BibTeX] [Abstract] [Download PDF]

    In this paper we describe the use of electron backscatter diffraction (EBSD) mapping and electron channeling contrast imaging-in the scanning electron microscope-to study tilt, atomic steps and dislocations in epitaxial GaN thin films. We show results from a series of GaN thin films of increasing thickness and from a just coalesced epitaxial laterally overgrown GaN thin film. From our results we deduce that EBSD may be used to measure orientation changes of the order of 0.02 degrees, in GaN thin films. As EBSD has a spatial resolution of approximate to 20 nm, this means we have a powerful technique with which to quantitatively map surface tilt. We also demonstrate that electron channeling contrast images may be used to image tilt, atomic steps, and threading dislocations in GaN thin films.

    @Article{strathprints31032,
    author = {C. Trager-Cowan and F. Sweeney and P. W. Trimby and A. P. Day and A. Gholinia and N. -H. Schmidt and P. J. Parbrook and A. J. Wilkinson and I. M. Watson},
    title = {Electron backscatter diffraction and electron channeling contrast imaging of tilt and dislocations in nitride thin films},
    journal = {Physical Review B},
    year = {2007},
    volume = {75},
    number = {8},
    pages = {085301},
    month = {February},
    abstract = {In this paper we describe the use of electron backscatter diffraction (EBSD) mapping and electron channeling contrast imaging-in the scanning electron microscope-to study tilt, atomic steps and dislocations in epitaxial GaN thin films. We show results from a series of GaN thin films of increasing thickness and from a just coalesced epitaxial laterally overgrown GaN thin film. From our results we deduce that EBSD may be used to measure orientation changes of the order of 0.02 degrees, in GaN thin films. As EBSD has a spatial resolution of approximate to 20 nm, this means we have a powerful technique with which to quantitatively map surface tilt. We also demonstrate that electron channeling contrast images may be used to image tilt, atomic steps, and threading dislocations in GaN thin films.},
    keywords = {plan-view image, kikuchi diffraction, microscope, rocks, Plasma physics. Ionized gases, Electronic, Optical and Magnetic Materials, Condensed Matter Physics},
    url = {http://strathprints.strath.ac.uk/31032/}
    }

  • A. Winkelmann, C. Trager-Cowan, F. Sweeney, A. P. Day, and P. Parbrook, “Many-Beam Dynamical Simulation of Electron Backscatter Diffraction Patterns,” Ultramicroscopy, vol. 107, iss. 2007, p. 414–421, 2007.
    [BibTeX] [Abstract] [Download PDF]

    We present an approach for the simulation of complete electron backscatter diffraction (EBSD) patterns where the relative intensity distributions in the patterns are accurately reproduced. The Bloch wave theory is applied to describe the electron diffraction process. For the simulation of experimental patterns with a large field of view, a large number of reflecting planes has to be taken into account. This is made possible by the Bethe perturbation of weak reflections. Very good agreement is obtained for simulated and experimental patterns of gallium nitride GaNf0001g at 20 kV electron energy. Experimental features like zone-axis fine structure and higher-order Laue zone rings are accurately reproduced. We discuss the influence of the diffraction of the incident beam in our experiment.

    @article{strathprints3089,
    volume = {107},
    number = {2007},
    title = {Many-Beam Dynamical Simulation of Electron Backscatter Diffraction Patterns},
    author = {Aimo Winkelmann and Carol Trager-Cowan and Francis Sweeney and Austin P. Day and Peter Parbrook},
    year = {2007},
    pages = {414--421},
    journal = {Ultramicroscopy},
    keywords = {electron backscatter diffraction, nanoscience, wave theory, Solid state physics. Nanoscience, Instrumentation, Atomic and Molecular Physics, and Optics, Electronic, Optical and Magnetic Materials},
    url = {http://strathprints.strath.ac.uk/3089/},
    abstract = {We present an approach for the simulation of complete electron backscatter diffraction (EBSD) patterns where the relative intensity distributions in the patterns are accurately reproduced. The Bloch wave theory is applied to describe the electron diffraction process. For the simulation of experimental patterns with a large field of view, a large number of reflecting planes has to be taken into account. This is made possible by the Bethe perturbation of weak reflections. Very good agreement is obtained for simulated and experimental patterns of gallium nitride GaNf0001g at 20 kV electron energy. Experimental features like zone-axis fine structure and higher-order Laue zone rings are accurately reproduced. We discuss the influence of the diffraction of the incident beam in our experiment.}
    }

  • C. Trager-Cowan, F. Sweeney, A. Winkelmann, A. J. Wilkinson, P. W. Trimby, A. P. Day, A. Gholinia, N. H. Schmidt, P. J. Parbrook, and I. M. Watson, “Characterisation of nitride thin films by electron backscatter diffraction and electron channelling contrast imaging,” Materials Science and Technology, vol. 22, iss. 11, p. 1352–1358, 2006.
    [BibTeX] [Abstract] [Download PDF]

    In the present paper the authors describe the use of electron backscatter diffraction (EBSD) mapping and electron channelling contrast imaging (in the scanning electron microscope) to study tilt, strain, atomic steps and dislocations in epitaxial GaN thin films. Results from epitaxial GaN thin films and from a just coalesced epitaxial laterally overgrown GaN thin film are shown. From the results it is deduced that EBSD may be used to measure orientation changes of the order of 0?02? and strain changes of order 2 {$\times$} 10?4 in GaN thin films. It is also demonstrated that channelling contrast in electron channelling contrast images may be used to image tilt, atomic steps and threading dislocations in GaN thin films. In addition the authors will consider the results of the first many-beam dynamical simulations of EBSD patterns from GaN thin films, in which the intensity distributions in the experimental patterns are accurately reproduced.

    @Article{strathprints3084,
    author = {C. Trager-Cowan and F. Sweeney and A. Winkelmann and A.J. Wilkinson and P.W. Trimby and A.P. Day and A. Gholinia and N.H. Schmidt and P.J. Parbrook and I.M. Watson},
    title = {Characterisation of nitride thin films by electron backscatter diffraction and electron channelling contrast imaging},
    journal = {Materials Science and Technology},
    year = {2006},
    volume = {22},
    number = {11},
    pages = {1352--1358},
    month = {November},
    abstract = {In the present paper the authors describe the use of electron backscatter diffraction (EBSD) mapping and electron channelling contrast imaging (in the scanning electron microscope) to study tilt, strain, atomic steps and dislocations in epitaxial GaN thin films. Results from epitaxial GaN thin films and from a just coalesced epitaxial laterally overgrown GaN thin film are shown. From the results it is deduced that EBSD may be used to measure orientation changes of the order of 0?02? and strain changes of order 2 {$\times$} 10?4 in GaN thin films. It is also demonstrated that channelling contrast in electron channelling contrast images may be used to image tilt, atomic steps and threading dislocations in GaN thin films. In addition the authors will consider the results of the first many-beam dynamical simulations of EBSD patterns from GaN thin films, in which the intensity distributions in the experimental patterns are accurately reproduced.},
    keywords = {nitride thin films, electron backscatter diffraction, electron channelling, contrast imaging, nanoscience, Solid state physics. Nanoscience, Mechanics of Materials, Materials Science(all), Mechanical Engineering, Condensed Matter Physics},
    url = {http://strathprints.strath.ac.uk/3084/}
    }

  • C. Trager-Cowan, F. Sweeney, A. J. Wilkinson, P. W. Trimby, A. P. Day, A. Gholinia, N. H. Schmidt, P. J. Parbrook, and I. Watson, “Characterization of nitride thin films by electron backscatter diffraction and electron channeling contrast imaging,” in GaN, AIN, InN and related materials, M. Kuball, T. H. Myers, J. M. Redwing, and T. Mukai, Eds., Warrendale: Materials Research Society, 2006, p. 677–682.
    [BibTeX] [Abstract] [Download PDF]

    In this paper we describe the use of electron backscatter diffraction (EBSD) mapping and electron channeling contrast imaging-in the scanning electron microscope-to study tilt, atomic steps and dislocations in epitaxial GaN thin films. We show results from epitaxial GaN thin films and from a just coalesced epitaxial laterally overgrown GaN thin film. From our results we deduce that EBSD may be used to measure orientation changes of the order of 0.02 degrees, in GaN thin films. As EBSD has a spatial resolution of approximate to 20 rim, this means we have a powerful technique with which to quantitatively map surface tilt. We also demonstrate that channeling contrast in electron channeling contrast images may be used to image tilt, atomic steps and threading dislocations in GaN thin films.

    @incollection{strathprints36883,
    author = {Carol Trager-Cowan and Francis Sweeney and A.J. Wilkinson and P.W. Trimby and A.P. Day and A Gholinia and N.H. Schmidt and P.J. Parbrook and Ian Watson},
    series = {Materials research society symposium proceedings},
    booktitle = {GaN, AIN, InN and related materials},
    editor = {M Kuball and T.H. Myers and J.M. Redwing and T Mukai},
    address = {Warrendale},
    title = {Characterization of nitride thin films by electron backscatter diffraction and electron channeling contrast imaging},
    publisher = {Materials Research Society},
    year = {2006},
    pages = {677--682},
    keywords = {plan-view image, kikuchi diffraction, GAN, dislocations, microscope, strain, rocks, SEM, Physics},
    url = {http://strathprints.strath.ac.uk/36883/},
    abstract = {In this paper we describe the use of electron backscatter diffraction (EBSD) mapping and electron channeling contrast imaging-in the scanning electron microscope-to study tilt, atomic steps and dislocations in epitaxial GaN thin films. We show results from epitaxial GaN thin films and from a just coalesced epitaxial laterally overgrown GaN thin film. From our results we deduce that EBSD may be used to measure orientation changes of the order of 0.02 degrees, in GaN thin films. As EBSD has a spatial resolution of approximate to 20 rim, this means we have a powerful technique with which to quantitatively map surface tilt. We also demonstrate that channeling contrast in electron channeling contrast images may be used to image tilt, atomic steps and threading dislocations in GaN thin films.}
    }