Electron Backscattered Diffraction Patterns from Cooled Gallium Nitride Thin Films

Abstract

The acquisition of electron backscattered diffraction (EBSD) (or Kikuchi diffraction) patterns in the scanning electron microscope is proving to be a useful technique with which to probe the structural properties of nitride thin films. In this paper we show that if a sample is cooled the patterns improve dramatically, an increase in intensity of the Kikuchi lines and a decrease in the intensity of the diffuse background is observed. Kikuchi lines from higher order planes become visible and the HOLZ rings become better defined. Such cooled patterns yield more information on the sample, particularly on non-centrosymmetric planes, from which the polarity of the nitride thin film under investigation may be deduced.Introduction The acquisition of electron backscattered diffraction (EBSD) (or Kikuchi diffraction) patterns in the scanning electron microscope is a very powerful method for the microstructural characterisation of crystalline materials. EBSD is at present predominantly used in metallurgy for the measurement of texture, i.e., the mapping of the orientation of individual grains in polycrystalline samples [1], and to identify different crystalline phases. However, Wilkinson [2] and Troost et al. [3] applied EBSD to the measurement of strain in SiGe epilayers while Baba-Kishi [4] has used EBSD to investigate crystallographic polarity of non-centrosymmetric structures. These results strongly suggest that EBSD may be a useful technique to apply to the characterisation of nitride thin films.In previous work [5] we have used EBSD to reveal the relative orientation of a nitride thin film with respect to its substrate; determine the tilt of a GaN thin film; detect improved surface quality in As-doped GaN films grown under high As 4 flux; and observe more detail in EBSD patterns from cooled GaN thin films. In this paper we show that EBSD patterns obtained from cooled GaN thin films can provide information on non-centrosymmetric planes, from which the polarity of the nitride thin film under investigation may be deduced.

Electron diffraction methods for the analysis of silicon carbide surfaces and the controlled growth of polytype heterostructures

“…The quality of the crystal is reflected by the sharpness of the patterns. That is why ECP and EBSD have been used for analysis of the quality of epitaxially grown films [83][84][85][86][87] and for the quantification of ion implantation damage [88]. Crystal defects can be imaged by EC because they create a contrast [89].…”

Polarity Determination in EBSD Patterns Using the Hough Transformation

“…These shifts depend on the atomic arrangement within a crystal lattice (Nolze et al, 2015;Winkelmann & Nolze, 2015). In principle, EBSD enables the determination of the polarity of certain axes in a non-centrosymmetric structure as reported for several structures of the zincblende or wurtzite type (Baba-Kishi, 1991, 2002Sweeney et al, 2001;Nolze et al, 2015;Winkelmann & Nolze, 2015;Naresh-Kumar et al, 2017, 2019. The orientation of a polar axis is essential for all material properties directly related to the existence of that polar axis as e.g.…”

Crystallographic analysis of thin specimens

“…Improving EBSD pattern quality and exploring the ultimate spatial resolution of orientation maps have been achieved by cooling a semiconductor specimen (Sweeney et al ., 2001) and by lowering the electron beam voltage (Isabell & Dravid, 1997; Dingley, 2004). In addition, sample thickness dependence of backscatter electron yields has been calculated for two materials (Sogard, 1980).…”