Yu J E, Jones K S, Park R M
Department of Materials Science and Engineering, University of Florida, Gainesville 32611.
J Electron Microsc Tech. 1991 Jul;18(3):315-24. doi: 10.1002/jemt.1060180314.
Cross-sectional transmission electron microscopy (TEM) sample preparation of ZnSe/GaAs epitaxial films is investigated. Conventional argon ion milling is shown to produce a high density (approximately 5-8 x 10(11)/cm2) of small (diameter approximately 60-80 A) extended defects (stacking faults, microtwins, double positioning twins, etc.). In addition, transmission electron diffraction results indicate a thin ZnO layer can also occasionally form upon ion milling or electron-beam irradiation although the exact conditions for ZnO formation are not well understood. Conventional TEM (amplitude contrast) and high-resolution TEM (phase contrast) imaging in combination with transmission electron diffraction studies were performed to determine the optimum method of removing the ion milling related damage and ZnO layers during sample preparation. HF/HCl, NaOH/H2O, H2SO4/H2O2/H2O and Br2/CH3OH etching mixtures as well as low voltage argon or iodine ion milling were studied. A low energy (2 keV) iodine or argon ion milling step was shown to remove the ZnO layer and reduced the density of the extended defects associated with Ar+ ion milling, but was unsuccessful in removing all of the defects. Auger electron spectroscopy results indicate residual iodine was either left on the surface or implanted beneath the surface during iodine ion milling. Etching the XTEM samples in HF/HCl was shown to be effective in removing the ZnO layer but had little or no effect on the ion milling induced defects. Etching the samples in a 0.5% Br2/CH3OH solution resulted in complete elimination of the ion milling induced extended defects including the residual defects associated with iodine ion milling. In addition the Br2/CH3OH etch produced the best surface morphology. Thus a brief (1-2 seconds) Br2/CH3OH etch after conventional preparation (argon ion milling) of cross-sectional ZnSe/GaAs TEM samples appears to be an inexpensive and superior alternative to iodine ion milling.
研究了ZnSe/GaAs外延膜的横截面透射电子显微镜（TEM）样品制备方法。结果表明，传统的氩离子铣削会产生高密度（约5 - 8×10¹¹/cm²）的小尺寸（直径约60 - 80 Å）扩展缺陷（堆垛层错、微孪晶、双定位孪晶等）。此外，透射电子衍射结果表明，尽管对ZnO形成的确切条件尚不清楚，但在离子铣削或电子束辐照时偶尔也会形成一层薄的ZnO层。采用传统TEM（振幅衬度）和高分辨率TEM（相位衬度）成像，并结合透射电子衍射研究，以确定在样品制备过程中去除与离子铣削相关的损伤和ZnO层的最佳方法。研究了HF/HCl、NaOH/H₂O、H₂SO₄/H₂O₂/H₂O和Br₂/CH₃OH蚀刻混合物以及低电压氩或碘离子铣削。结果表明，低能（2 keV）碘或氩离子铣削步骤可去除ZnO层，并降低与Ar⁺离子铣削相关的扩展缺陷密度，但未能完全去除所有缺陷。俄歇电子能谱结果表明，在碘离子铣削过程中，残余碘要么留在表面，要么注入到表面以下。结果表明，在HF/HCl中蚀刻XTEM样品可有效去除ZnO层，但对离子铣削引起的缺陷影响很小或没有影响。在0.5%的Br₂/CH₃OH溶液中蚀刻样品可完全消除离子铣削引起的扩展缺陷，包括与碘离子铣削相关的残余缺陷。此外，Br₂/CH₃OH蚀刻产生了最佳的表面形貌。因此，在传统制备（氩离子铣削）横截面ZnSe/GaAs TEM样品后进行短暂（1 - 2秒）的Br₂/CH₃OH蚀刻，似乎是一种比碘离子铣削更便宜且更优越的替代方法。
