Secondary ion mass spectrometry (SIMS) provides a unique capability for performing threedimensional microchemical characterization with a single instrument. In using SIMS to investigate the composition of solids the sample is sputtered away by ion bombardment. The sputtered particles immediately ejected as ions are characteristic of the sample composition. When separated in a mass spectrometer, these ions can be used in principle for quantitative analysis. The production of these secondary ions, some recently developed ion probe instrumentation, some new analytical techniques, and some new analytical applications are briefly described.

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Research during the last decade has led to the microscopic understanding of the atomic, electronic, and chemical (compositional) structures at semiconductor surfaces and interfaces. First, we present a brief review of LEED (Low energy Electron Diffraction) intensity analyses of the atomic geometry of the (110) surfaces of 3-5 and 2-6 compounds. The dynamical calculation proposes an atomic model of the (110) surface with top twolayer reconstructions for GaAs, InSb, InP, and probably the topmost singlelayer reconstruction for the more ionic ZnTe. Secondly, after a brief description of standard AES analyses of the chemical composition of the surfaces and interfaces, particular attention is focussed on soft Xray photoemission studies on the interface formed by MBE (Molecular Beam Epitaxy) techniques. Thirdly, theoretical band calculations are mentioned based on the LEED atomic model. Finally, to develop a model of the atomic geometry and the initial step of oxidation. we present recent ab initio first principle calculations using a technique of quantum chemistry which has been applied to the GaAs (110) surface.

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Auger electron appearance potential spectroscopy (AEAPS) apparatus for the study of solid state surfaces was constructed and the working conditions were extensively examined for surfaces of the 3d transition metals (Ti∼Ni). For the clean surface of polycrystalline Ti, the spectra of the first and second derivative signals were in good agreement with theoretical results obtained from the unfilled 3d binding state at Fermi energy E_F. The spectra of Ti, Fe and Ni were obtained on both clean and oxidized surfaces at room temperature. The AEAPS and soft Xray appearance potential spectroscopy (SXAPS) spectra were compared on the same Mn and Co clean surfaces. Relative L₃ AEAPS signal strengths were measured for clean 3d transition metal (Ti∼Ni) surfaces.

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It is known that angle-resolved x-ray photoelectron spectroscopy (ARXPS) provides, in addition to ordinary XPS information, quite new information concerning the crystal regularity of the surface layers. This technique was used to characterize the initial crystal growth of gold films evaporated on GaAs (110) surfaces to a thickness about 5-6Å. The angular distribution curve (ADC) of Au 4f photoelectron intensity showed some clear fine structure after the heat treatment for 30 minutes at 350-400°C. Taking the results of chemical state analysis into consideration, it can be concluded that the Au atoms grew epitaxially in an island-like fashion. When the annealing temperature was raised over 450°C, the fine structure of ADC from the Au 4f peak disappeared, implying diffusion of Au atoms into the bulk GaAs crystal. In summary it is shown that ARXPS has quite useful applicability for investigation of the initial crystal growth of very thin films evaporated on semiconductor surfaces.

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An attempt was made to correlate the epitaxial growth of Sn with the fine structure of a vacuum-cleaved KCl substrate surface. Deposition was made on the substrate over a wide range of temperatures, and deposits were examined by optical and electron microscopy. One deposit was formed at room temperature, showing the {100} orientation on the overall substrate surface. The second and the third deposits showed the {100} and the {101} orientations on the higher density step and on the flat surface, respectively. The latter is mainly composed of a component whose orientation is rotated by about 3° from the [010] direction of the substrate. This appears with the increase of the substrate temperature. The respective orientations are discussed with the interaction between these deposits and the fine details of the surface structures.

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A preliminary study of the growth of diamond by vapor deposition has been carried out using diamond powder and labelled methane ¹³13CH₄O. The powder substrate pre-treated with hydrogen was heated to temperatures of 800-990°C in a closed reaction chamber filled with ¹³CH₄O at 1-10 Torr initial pressure. Considering the isotope shift of the Raman lines of diamond and disordered carbon, the following has been noted from the Raman spectra of such powders. Highly disordered carbon is always deposited on the surface of diamond particles treated under the described conditions. A spectrum indicating the presence of a small amount of diamond composed of ¹³C is found with the powder heated in 1 Torr ¹³CH₄O at 800°C for 45hrs. At 10 Torr and 830°C, the deposit appears to consist entirely of disordered carbons; no indication of deposited diamond is found. Surface graphitization of the substrate occurs when heated in 1 Torr ¹³CH₄O at 990°C.

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Difficulties are briefly described in measurements of interface phenomena. The principle of photoacoustic spectroscopy (PAS) is introduced by explaining energy transfer routes. Light absorbed at an interface produces light (fluorescence), chemical species, and heat. PAS utilizes the heat generated after light absorption by detecting the pressure change due to the temperature rise. Therefore, PAS is very insensitive to the elastic scattering of light, which causes serious difficulties in conventional spectroscopic methods applied to inhomogeneous systems, i.e., interfaces. Instrumental features are explained especially for a detection cell. For a gas-solid interface system, a sensitive microphone placed on the wall of a sample chamber is used to detect the heat emitted as sound at an interface. For a liquid-solid interface system, a piezoelectric ceramic is utilzed as a pressure sensor and also as part of the cell for the liquid. Recent results are described for in situ observation of spectral sensitizing dyes at a semiconductor electrode-solution interface and at a semiconductor-gas interface.

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Exoelectrons are emitted from solid surfaces stimulated with light illumination (OSEE, PSEE) or heating (TSEE) after prior damage externally introduced by mechanical treatment or exposure to ionizing radiation. The emission of low-energy electrons is detected by employing a GM counter, electron multiplier or picoammeter. Exoelectron emission (EE) is a complicated phenomenon composed of various physical and chemical processes. Despite uncertainty in the mechanism, EE has been applied successfully in the study of radiation dosimetry, metal deformation and fatigue, and other surface phenomena. Fatigue failure of metals can be predicted by measuring the total emission of PSEE from surfaces, or from the change in intensity of the largest PSEE peak during the fatigue cycle. The EE microscope has proven to be a useful tool for the examination of metal surfaces associated with the generation and extinction of a fresh surface.

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