The uses of MeV and keV ion beams to measure hydrogen atoms in solids and onto the surfaces are described. Experimental results obtained using high energy ion beam scattering in resonance nuclear reaction analysis (RNRA) and elastic recoil detection analysis (ERD) are briefly reviewed. Also, the determination of hydrogen position on a Pt (111) surface at 150 K by using low energy recoil scattering analysis (LERS) is described. The different methods are compared in terms of their advantages and disadvantages for certain analytic characteristics in this report.

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II-VI blue-green laser diodes have attracted much attention for use as lightsources for future optical disc systems. Epitaxial growth of ZnSe-based mterials using a gaseous source is required, because the elements comprising these materials have high vapour pressures. To date, attempts at growth of p-type low-resistivity layers using a gas source have been unsuccessful due to passivation of acceptors by hydrogen in the sources. We describe conditions for growth of p-type ZnSe-based materials by gas source molecular beam epitaxy with a solid source of group II elements, a hydride gas of a group VI element and nitrogen activated by rf plasma. The acceptor concentrations of the grown layers are comparable to those grown by solid source molecular beam epitaxy. Using the low-resistivity p-type layers, pulse oscillation of a ZnCdSe/ZnMgSSe laser diode is attained at 200 K.

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Plasma-surface interactions for poly-Si gate etching have been studied in Cl₂ and Cl₂/O₂ electron cyclotron resonance (ECR) plasmas, through in situ diagnostics of reaction products during etching and numerical simulation for the etched profile evolution. The in situ observation of product species was conducted both in the gas phase and on the substrate surface, by employing Fourier transform infrared (FTIR) absorption spectroscopy. For both Cl₂ and Cl₂/O₂ plasmas, silicon tetrachloride SiCl₄ was the only IR-absorbing etch product species detected in the gas phase, while unsaturated SiCl_x (x= 1-3) as well as SiCl₄ were observed on the surface; moreover, a broad absorption feature due to Si-O vibrations or silicon oxides was found to occur both in the gas phase and on the surface, implying competitive chlorination and oxidation of the surface, and also competitive etching and surface inhibitor deposition. Based on these observations, the surface chemistry was modeled for Cl₂ and Cl₂/O₂ plasma etching of poly-Si, including ion-assisted reaction processes, physical sputtering or desorption of adsorbates by energetic ion bombardment, and passivation layer formation consisting of surface oxidation and inhibitor deposition. Moreover, numerical calculations were performed for the profile evolution during etching, by employing the surface chemistry model proposed and taking into account a variety of neutral transport mechanisms in microstructures that are known from the literature. The etched profiles numerically and experimentally obtained were then compared to unravel competitive mechanisms responsible for the anisotropy and microscopic uniformity in poly-Si gate etching in low-pressure, high-density chlorine-containing plasmas.

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By simultaneous evaporation of lead iodide (PbI₂) and organic ammonium iodide (RNH₃I), highly oriented thin films of perovskite quantum-well (RNH₃) ₂PbI₄ consisting of alternating layers of inorganic semiconductor layers of PbI₄ and organic dielectric layers of RNH₃ were grown on fused quartz substrates at about 10^-4 Pa. The vacuumdeposited layered perovskite films exhibited strong exciton absorption and sharp exciton emission even at room temperature owing to their low-dimensional semiconductor nature. Further, X-ray diffraction measurement revealed that the inorganic and organic layers were oriented parallel to the film plane in the case of these vacuum-deposited films.
In addition, the simple preparation method involving the dual-source vapor deposition was found to be applicable to other layered perovskites and related cubic perovskites such as (RNH₃) ₂PbBr₄, (RNH₃) ₂SnI₄, (CH₃NH₃) PbI₃ and (CH₃NH₃) PbBr₃.

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A new selective-area GaAs growth technique on a nanometer scale is demonstrated by a combination of nitrogen (N) -passivation mask formation, scanning tunneling microscopy (STM) pattern modification, and metalorganic molecular beam epitaxy. GaAs (001) surfaces are passivated with N radicals dissociated from N₂ molecules, and are modified by STM on a nanometer scale. GaAs nanostructures are grown on the surfaces using trimethylgallium and tertiarybutylarsenic. An array of uniform 6-nm-high and 50×50-nm² dots was formed on the STM-modified areas. The advantages of the technique are that size-controlled nanostructures can be fabricated in specific positions and that the nanostructures formed are free from contamination because all processes are performed in a vacuum.

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An in situ investigation of hydrogenated nanocrystalline silicon (nc-Si : H) growth on SiO₂ and other substrates by UV-visible spectroscopic ellipsometry is presented. The deposition studies of nc-Si from SiH₄ highly diluted in H₂ by RF plasma-enhanced chemical vapor deposition (RF PECVD) on various substrates showed that 3-dimensional crosslinking and relaxation of the Si network near the growing surface were essential for the formation of nanocrystalline silicon. The surface roughness during the growth of nc-Si : H strongly influenced on the creation of the crystallite phase and the relaxation of the Si network. Crystallinity was promoted at an earlier stage of growth on a Cr substrate rather thanon SiO₂. We have proposed a SiH₄ gas heating technique to improve the crystallinity at an earlier stage of growth on SiO₂. The crystallinity was enhanced without an increase of surface roughness.

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Negative electron affinity (NEA) of the diamond surface is expected to enable the realization of a stable and efficient electron emitter for microvacuum electronics devices and multiemitter display panels. We have studied the diamond surface by techniques such as photoemission spectroscopy, ion beam analysis, and high-resolution electron microscopy, and established the control of the electron affinity by hydrogenation or oxidation in plasma, or irradiation to vacuum ultraviolet light. The conductivity of the NEA surface should be taken into consideration, as well as the NEA feature itself, in the design of the structure of electron emitter devices with the hydrogenated diamond surface. In this paper, we present studies on diamond surfaces, and the design and characterization of an electron emitter using diamond thin film into which electrons have been injected for emission from the NEA surface.

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