A High Resolution TEM Study of In-Situ Surface Oxidation of Indium III-V Semiconductors
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A HIGH RESOLUTION TEM STUDY OF IN-SITU SURFACE OXIDATION OF INDIUM III-V SEMICONDUCTORS DAVID J. SMITH AND AMANDA K. PETFORD-LONG Center for Solid State Science, Arizona State University, Tempe, AZ 85287. ABSTRACT Electron irradiation of InP, InAs and InSb crystals within the electron microscope causes the crystallization of nearsurface amorphous material and the oxidation of bulk crystalline material. The material most commonly found in both regions is cubic In 2 0,0 although small regions (< 5 nm) of the corresponding In-c 6mpound semiconductors are sometimes recrystalThe observations are consistent with desorption of the lized. anion species due to electron-beam-stimulated processes, with subsequent oxidation of residual In metal. INTRODUCTION Surface oxidation of III-V compound semiconductors occurs during device fabrication and can have an adverse effect on Various techniques, such as Raman device properties [1]. spectroscopy [2], x-ray photoemission spectroscopy [2,31 and Auger and low energy loss spectroscopy [41 have been used to study the surface oxide films produced by thermal oxidation. These oxidation processes have not, however, been studied by although the growth high resolution electron microscopy (HREM), of surface oxide crystals during electron irradiation of InP This paper briefly describes our HREM has been reported [5]. observations of the surface oxidation of several In-compound semiconductors which occurred during extended periods of electron irradiation; a more detailed account of this work can be found elsewhere [6]. EXPERIMENTAL DETAILS Samples of InSb, InAs and InP were separately prepared for electron microscopy by crushing under ethanol, and a drop of the resulting suspension was deposited on a holey carbon The specimens were observed using a JEM-4000EX support film. operated at 400kV, and at 100kV so that any changes in oxidation behavior wi--th incident electron beam energy could be The microscope was equipped with a specimen-tilting studied. cartridge, making it possible to orient small crystals (1-10 microns) so that low-index zone axes, namely [110], [100] and [112], were aligned parallel to the incident beam direction. Lattice fringes recorded on the micrographs were usually measured by the use of the optical diffractogram (ODM) technique (7], using the diffraction spots due to bulk material lattice spacings as an internal calibration, so that the various phases present could easily be identified. RESULTS Irradiation of the three different indium compound semiconductors by the electron beam invariably led to the random development of crystallization throughout the thin (5 -15nm) Mat. Res Soc. Syrp. Proc. Vol 75
1987 Materials Research Society
726
Fig. 1. HREM images of InSb viewed along [100]. a) Soon after initial beam exposure, b) after 3-5 minutes beam exposure, and c) after 20 minutes beam exposure. Surface crystals of In 2 0 3 have developed well-defined boundaries (arrowed in c). The feature marked by crosses in all three images indicates the extent to which the crystalli
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