Analysis of Amorphous-to-crystalline Germanium Stack with Cs-corrected Analytical STEM

Abstract
In recent yeas, various avenues are being explored to increase the efficiency of photovoltiacs devices [1]. In this regard amorphous germanium (a-Ge), a semiconducting material, has excellent optical and electronic properties which make it an excellent candidate for solar cell applications [2]. Moreover a-Ge is a better “selective absorber” than amorphous silicon (a-Si) because the former has lower optical band gap (0. 7 eV) than the latter (1.1 eV) [3]. Given the fact that it has excellent properties, a little attention is paid to its characterization with techniques capable of discerning information at nanometer scale spatial resolutions e.g. with transmission electron microscopy (TEM). Consequently, for a-Ge material, there is dearth of studies showing the structure-property relationships established by using such techaniques. That is why a study, completed by using a TEM of model Titan 80-300 ST from FEI Company in the scanning TEM (STEM) mode, is presented in this paper. The microscope was also equipped with a shperical aberration corrector (Cs-corrector) from CEOS for making a finer probe and Gatan Image Filter (model GIF-Quantum 966) so that Cs-corrected STEM and electron energy loss spectroscopy (EELS) analyses can be used to anlayze these samples. In this study, the [001] oriented crytsalline Ge (c-Ge) samples were grown in a metal organic chemical vapor deposition (MOCVD) system of ASM Epsilon 2000 model. The a-Ge layer, with a target thickess of ~ 30 nanomters was then created via gallium (Ga) implantation (at a dose of ~1016 atoms/cm2) into c-Ge with a 30 keV Ga-beam in a focused ion beam (FIB) system of model Helios 450 from FEI Company. The same FIB system was then utilized later on to prepare [110] oriented cross-section specimen to perform the STEM-EELS analysis of stacks.

Citation
Anjum, D. H., Lee, K. H., Zhou, G., Zhang, Q., Wei, N., Xia, G. (Maggie), … Zhang, X. (2017). Analysis of Amorphous-to-crystalline Germanium Stack with Cs-corrected Analytical STEM. Microscopy and Microanalysis, 23(S1), 1514–1515. doi:10.1017/s1431927617008236

Publisher
Cambridge University Press (CUP)

Conference/Event Name
Microscopy & Microanalysis 2017

DOI
10.1017/s1431927617008236

Additional Links
https://www.cambridge.org/core/product/identifier/S1431927617008236/type/journal_article

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