@Article{strathprints79640,
author = {Gunasekar, Naresh and Edwards, Paul and Martin, Robert and Batten, Tim and Trager-Cowan, Carol and Hourahine, Ben and Starosta, Bohdan and Nouf-Allehiani, M. and Shields, Philip A. and Le Boulbar, Emmanuel D. and Wilkinson, Angus and Vilalta-Clemente, Arantxa},
journal = {Journal of Applied Physics},
title = {Non-destructive imaging of residual strains in {GaN} and their effect on optical and electrical properties using correlative light-electron microscopy},
year = {2022},
issn = {0021-8979},
month = {February},
number = {7},
pages = {075303},
volume = {131},
abstract = {We demonstrate a non-destructive approach to understanding the growth modes of a GaN thin film and simultaneously quantify its residual strains and their effect on optical and electrical properties using correlative scanning electron microscopy techniques and Raman microscopy. Coincident strain maps derived from electron backscatter diffraction, cathodoluminescence and confocal Raman techniques reveal strain variations with similar magnitude and directions, especially in the proximity of dislocations. Correlating confocal Raman imaging with electron channelling contrast imaging suggests that the dislocations organise themselves to form a distinctive pattern as a result of the underlying growth mask, where some of them align along the [0001] growth direction and some are inclined. The methodology presented in this work can be adopted to investigate any heteroepitaxial growth, in particular those using selective masks on the growth substrates, where the morphology influences the subsequent growth.},
doi = {10.1063/5.0080024},
keywords = {SEM, thin films, GaN LED, strain analysis, diffraction and scattering, cathodoluminescence hyperspectral imaging, Physics, Physics and Astronomy(all)},
url = {https://doi.org/10.1063/5.0080024},
}

@Article{strathprints61621,
author = {G. Naresh-Kumar and A. Vilalta-Clemente and H. Jussila and A. Winkelmann and G. Nolze and S. Vespucci and S. Nagarajan and A.J. Wilkinson and C. Trager-Cowan},
title = {Quantitative imaging of anti-phase domains by polarity sensitive orientation mapping using electron backscatter diffraction},
journal = {Scientific Reports},
year = {2017},
volume = {7},
pages = {10916},
month = {August},
abstract = {Advanced structural characterisation techniques which are rapid to use, non-destructive and structurally definitive on the nanoscale are in demand, especially for a detailed understanding of extended-defects and their influence on the properties of materials. We have applied the electron backscatter diffraction (EBSD) technique in a scanning electron microscope to non-destructively characterise and quantify antiphase domains (APDs) in GaP thin films grown on different (001) Si substrates with different offcuts. We were able to image and quantify APDs by relating the asymmetrical intensity distributions observed in the EBSD patterns acquired experimentally and comparing the same with the dynamical electron diffraction simulations. Additionally mean angular error maps were also plotted using automated cross-correlation based approaches to image APDs. Samples grown on substrates with a 4° offcut from the [110] do not show any APDs, whereas samples grown on the exactly oriented substrates contain APDs. The procedures described in our work can be adopted for characterising a wide range of other material systems possessing non-centrosymmetric point groups.},
keywords = {quantitative imaging, orientation mapping, thin films, Physics, Physics and Astronomy(all)},
url = {http://strathprints.strath.ac.uk/61621/}
}

@Article{strathprints60424,
author = {Aimo Winkelmann and Gert Nolze and Stefano Vespucci and Naresh Gunasekar and Carol Trager-Cowan and Arantxa Vilalta-Clemente and Angus J. Wilkinson and Maarten Vos},
title = {Diffraction effects and inelastic electron transport in angle-resolved microscopic imaging applications},
journal = {Journal of Microscopy},
year = {2017},
volume = {267},
number = {3},
pages = {330--346},
month = {March},
abstract = {We analyze the signal formation process for scanning electron microscopic imaging applications on crystalline specimens. In accordance with previous investigations, we find nontrivial effects of incident beam diffraction on the backscattered electron distribution in energy and momentum. Specifically, incident beam diffraction causes angular changes of the backscattered electron distribution which we identify as the dominant mechanism underlying pseudocolor orientation imaging using multiple, angle-resolving detectors. Consequently, diffraction effects of the incident beam and their impact on the subsequent coherent and incoherent electron transport need to be taken into account for an in-depth theoretical modeling of the energy and momentum distribution of electrons backscattered from crystalline sample regions. Our findings have implications for the level of theoretical detail that can be necessary for the interpretation of complex imaging modalities such as electron channeling contrast imaging (ECCI) of defects in crystals. If the solid angle of detection is limited to specific regions of the backscattered electron momentum distribution, the image contrast that is observed in ECCI and similar applications can be strongly affected by incident beam diffraction and topographic effects from the sample surface. As an application, we demonstrate characteristic changes in the resulting images if different properties of the backscattered electron distribution are used for the analysis of a GaN thin film sample containing dislocations.},
keywords = {electron diffraction, electron microscope, cathodoluminescence, Physics, Physics and Astronomy(all)},
url = {http://strathprints.strath.ac.uk/60424/}
}

@Article{strathprints59588,
author = {A. Vilalta-Clemente and G. Naresh-Kumar and M. Nouf-Allehiani and P. Gamarra and M.A. di Forte-Poisson and C. Trager-Cowan and A.J. Wilkinson},
title = {Cross-correlation based high resolution electron backscatter diffraction and electron channelling contrast imaging for strain mapping and dislocation distributions in {InAlN} thin films},
journal = {Acta Materialia},
year = {2017},
volume = {125},
pages = {125--135},
month = {February},
abstract = {We describe the development of cross-correlation based high resolution electron backscatter diffraction (HR-EBSD) and electron channelling contrast imaging (ECCI), in the scanning electron microscope (SEM), to quantitatively map the strain variation and lattice rotation and determine the density and identify dislocations in nitride semiconductor thin films. These techniques can provide quantitative, rapid, non-destructive analysis of the structural properties of materials with a spatial resolution of order of tens of nanometers. HR-EBSD has a sensitivity to changes of strain and rotation of the order of 10?4 and 0.01? respectively, while ECCI can be used to image single dislocations up to a dislocation density of order 1010 cm?2. In the present work, we report the application of the cross-correlation based HR-EBSD approach to determine the tilt, twist, elastic strain and the distribution and type of threading dislocations in InAlN/AlN/GaN high electron mobility transistor (HEMT) structures grown on two different substrates, namely SiC and sapphire. We describe our procedure to estimate the distribution of geometrically necessary dislocations (GND) based on Nye-Kroner analysis and compare them with the direct imaging of threading dislocations (TDs) by ECCI. Combining data from HR-EBSD and ECCI observations allowed the densities of pure edge, mixed and pure screw threading dislocations to be fully separated.},
keywords = {EBSD, ECCI, dislocations, InAIN, HEMTs, electron backscatter diffraction, electron channelling contrast imaging, scanning electron microscope, nitride semiconductor thin films, geometrically necessary dislocations, Physics, Polymers and Plastics, Metals and Alloys, Ceramics and Composites, Electronic, Optical and Magnetic Materials},
url = {http://strathprints.strath.ac.uk/59588/}
}

@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/}
}

@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},
journal = {Physical Review Letters},
title = {Rapid nondestructive analysis of threading dislocations in wurtzite materials using the scanning electron microscope},
year = {2012},
month = {March},
number = {13},
pages = {135503},
volume = {108},
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/},
}

@Article{strathprints44510,
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},
journal = {Microscopy and Microanalysis},
title = {Applications of electron channeling contrast imaging for characterizing nitride semiconductor thin films},
year = {2012},
note = {Extended abstract of a paper presented at Microscopy and Microanalysis 2012 in Phoenix, Arizona, USA, July 29 ? August 2, 2012.},
number = {S2},
pages = {684--685},
volume = {18},
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},
keywords = {semiconductor thin films, electron channeling, nanotechnology, Microbiology, Physics, Biotechnology},
url = {http://strathprints.strath.ac.uk/44510/},
}

@article{strathprints19662,
volume = {230},
number = {3},
month = {June},
author = {C. Trager-Cowan and A. Wilkinson},
title = {Introduction - Journal of Microscopy},
journal = {Journal of Microscopy},
pages = {405--405},
year = {2008},
keywords = {electron backscatter diffraction, diffraction, Physics, Pathology and Forensic Medicine, Histology},
url = {http://strathprints.strath.ac.uk/19662/},
abstract = {This article introduces papers arising from the 14th Conference and Workshop on Electron Backscatter Diffraction(EBSD): its applications and related techniques,which was held between the 26th and 28th of March 2007 in New Lanark,Scotland.}
}

@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/}
}

@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/}
}

@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.}
}

@article{strathprints3087,
volume = {0},
number = {1},
month = {December},
author = {C. Trager-Cowan and F. Sweeney and A.J. Wilkinson and I.M. Watson and P.G. Middleton and K.P. O'Donnell and D. Zubia and S.D. Hersee and S. Einfeldt and D. Hommel},
title = {Determination of the structural and luminescence properties of nitrides using electron backscattered diffraction and photo- and cathodoluminescence},
journal = {Physica Status Solidi C},
pages = {532--536},
year = {2002},
keywords = {luminescence, nitrides, electron backscattered diffraction, cathodoluminescence, nanoscience, Solid state physics. Nanoscience, Condensed Matter Physics},
url = {http://strathprints.strath.ac.uk/3087/},
abstract = {In this paper we describe the use of electron backscattered diffraction (EBSD) for the characterisation of nitride thin films, and report its use in the study of the spatial variation of strain across an epitaxially laterally overgrown GaN (ELOG) thin film. We also discuss the combination of luminescence and EBSD measurements to enable luminescence properties of samples to be directly correlated with their crystallographic properties. We compare photoluminescence spectra and EBSD measurements from a set of GaN thin films grown on off-axis sapphire substrates, revealing the tilt of a GaN thin film grown on a 10? off-axis sapphire substrate to be responsible for the observation of luminescence defect bands in this film. We finally report on the use of EBSD to identify zinc blende regions in a predominantly wurtzite MBE film, with cathodoluminescence used to obtain correlated luminescence spectra.}
}