Novel SEM-based diffraction method for characterising nitride thin films

SEM imaging of dislocations






Researchers at Strathclyde (Carol Trager-Cowan and Naresh-Kumar) and Oxford (Angus Wilkinson) Universities have been collaborating for some time on the development of novel SEM-based diffraction methods for characterising nitride thin films. Electron channelling contrast imaging (ECCI) has a long association with the Department of Materials at Oxford. Modern FEG SEM instruments and digital imaging capabilities make it possible to fully realise the possibilities identified and pursued in much earlier pioneering work by Profs Hirsch and Booker at Oxford.  The recent Physical Review Letter shows that threading dislocations in GaN films with the hexagonal wurtzite structure can be reliably imaged and characterised as edge, screw, or mixed types using a very simple and unambiguous analysis of the black-white contrast associated with each defect when imaged using controlled diffraction conditions. The innovation offers improved quantification of dislocation densities and speed of analysis – two factors of concern to crystal growers we are working with


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