Oxide-semiconductor based gas sensors have been intensively investigated in order to improve the sensitivity and selectivity of a certain gas. This article reviews the recent research progress of gas sensors having oxide semiconductor as an active layer, in particular detecting for H₂ and volatile organic compounds. The semiconductor material for gas sensors reported in this article includes SnO₂, WO₃, ZnO, In₂O₃, and NiO. The sensitivity of gas sensors having different structures and semiconductors is compared.

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　Research activities on surface activated bonding (SAB) of dissimilar semiconductor materials for targeting advanced energy-harvesting and energy-saving devices are reviewed. The structural and electrical properties of interfaces fabricated using the SAB technologies are examined. The change in the interface characteristics due to annealing after bonding is highlighted. The characteristics of SAB-based hybrid multi-junction solar cells, SiC/Si junctions as prototypes of wide bandgap/narrow bandgap hetero structures, and single-crystal diamond/Si junctions for integrating diamond and Si devices in the future are discussed.

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　Diamond Like Carbon (DLC) films have several unique characteristics, high-hardness, wear resistances, low friction, and good chemical stability. Thus, their applications are widely spread, for example, automotive and mechanical sliding parts, cutting tools, and molding dies.
　In this paper, we describe their deposition processes, film structures, characteristics and mechanical properties, and their applications. Finally, we mention some recent developments and possibilities.

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　Electron emitting tip is widely used in many research fields such as microfabrication, electron microscopy, surface science and so on. There are mainly three types of electron emitter as thermionic, field-emission and Schottky electron emitter. Because of the high stability with large emission current, tungsten 〈100〉 single crystal coated with ZrO₂ is widely used as Schottky electron emitter of an electron microscope. In order to develop a new technique for evaluating electron emitter, we thought that it was possible to observe the surface topographic structures of the electron emitting tip with a scanning probe microscope and succeeded in observing the nanostructure of the electron emitting tip in air. In this study, we have tried to observe tip nanostructure using ultra high vacuum scanning tunneling microscope (UHV-STM), because electron emitter is generally used under UHV condition. Using UHV-STM, high resolution STM images which are related to scanning electron microscope images were acquired. This indicated that UHV-STM could be a plausible tool for electron tip characterization.

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　Average surface hitting number per molecule N_h when it exits vacuum tube has a close relation to pumping delay time. Several N_h were calculated using Monte-Carlo simulation method and Clausing's integral equation method for a cylidrical tube that has a point gas emission source. The results from both methods are in good agreement and the dependence of N_h on the tube length L are explained almost exactly with Clausing's integral equation.

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　We investigated the band-splitting of GaAs thin film by invoking broken inversion symmetry within the bulk region and the lost of 2D symmetry on the surface due to strain in first-principles calculations using density functional theory with spin-orbit interaction. The system is modeled by unreconstructed GaAs(001)-(1×1) slab, and by its strained counterpart arising from As dimerization. For the unstrained system, we found that the valence bands split while the conduction bands remain degenerate. This degeneracy is attributed to the sole contribution of p-state of As atoms found on the surface to this band, where 2D symmetry is preserved. When strain is imposed on this surface, the symmetry is broken and the conduction bands are split. These findings identify the changes in the band structure due to broken symmetry, suggesting their incorporation in the conventional degenerate theoretical description of the GaAs thin films done to date.

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　We developed an outgassing measurement system which can measure by two methods “Switching Between Two Pumping Paths method” and “Throughput method”. As a result of calibrating the two vacuum gauges on the upstream side of the sample flow path and the blank flow path, we obtained the calibration factor of 9.33×10⁻¹ and 9.68×10⁻¹ which the quantitative accuracy (confidence level 95%) is less than 14%. The ultimate pressure after baking at 150℃ for 64 hours reached 5.0×10⁻⁸ Pa. As a result, the detection lower limit of the system was 5×10⁻¹² Pa m³ s⁻¹. For an aluminum alloy sample exposed to an atmosphere of RH 50%, the outgassing rate after 20 hours was on the order of 10⁻⁸ Pa m³ s⁻¹ m⁻².

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