Yuichi Aoki

Negative Differential Resistance of CaF 2/CdF 2 Triple-Barrier Resonant-Tunneling Diode on Si(111) Grown by Partially Ionized Beam Epitaxy

Room-temperature negative differential resistance (NDR) of triple-barrier cadmium di-fluoride (CdF2)/calcium di-fluoride (CaF2) heterostructure resonant-tunneling diode (RTD) on a Si(111) substrate has been demonstrated. CdF2/CaF2 multilayered heterostructures were grown on a Si(111) substrate using partially ionized beam epitaxy to obtain atomically flat interfaces. The RTD structures, which consist of triple CaF2 energy barriers and double CdF2 quantum wells, were fabricated by electron beam (EB) lithography and dry etching to avoid thermal and chemical damage to the CdF2 layers. In the current-voltage characteristics of the RTD, NDR was clearly observed even at room temperature and the maximum peak-to-valley (P/V) ratio was about 6.

P6E-3 Surface Acoustic Wave Linear Motor Using Segment-Structured Diamond-Like Carbon Films on Contact Surface

A surface acoustic wave (SAW) linear motor, which is a kind of ultrasonic motors, has many merits such as thin structure, large force, high speed, precise positioning and so on. On the other hand, wear is one of problems in the motor due to friction drive principle. Diamond-like carbon (DLC) films have been recognized as a wear resistant material. In this research, segment structured DLC films are focused to avoid the DLC property of easy damage. Installation of the films to friction surface of the motor is reported. Measurement result of its driving characteristics is also described.

Failure Assessments for Outside-Exposed Photovoltaic Modules

Photovoltaic modules with single-crystalline silicon cells and multi-crystalline silicon cells, which were exposed outside for over nine years from 1992, have been evaluated for their failures. Current–voltage characteristic, electroluminescence, and thermography (dark mode) measurement of the modules were carried out as well as those of each solar cell in the modules. Application of these measurements in combination has been shown to be beneficial for investing the failure positions and failure factors in the modules. A new method of analyzing the positions of interconnection failures in modules was also adopted in the present study that is by using electroluminescence measurement and by connecting wires to the interconnector of each individual solar cell.

Early Failure Detection of Interconnection with Rapid Thermal Cycling in Photovoltaic Modules

To accelerate the degradation with thermal fatigue in crystalline silicon photovoltaic modules, the modules were exposed to dry thermal stress with rapid thermal cycling, and module impedance was monitored in situ during this testing. The spikelike increase in module impedance at a temperature-alteration point was observed in the early stage of this rapid thermal cycling. The pattern of increase in module impedance proceeded step-by-step, from the early stage, via the double-spikelike pattern at two temperature-alteration points (the middle stage), and finally to the successive increases in module impedance in the high-temperature period (the late stage). The nondestructive analyses suggest that the interconnector failures without the defects of photovoltaic cells occurred. From these results, it is suggested that the pattern of increase in module impedance is related to the interconnection degradation of modules, and that the rapid thermal cycling with in situ monitoring of module impedance would be a useful procedure for the earlier detection of interconnection failures in photovoltaic modules.

Tribological Property of Segment-Structured DLC Film Under Oil-Lubrication Condition

Diamond-Like Carbon film (DLC film) shows excellent tribological properties. However, due to its brittleness, conventional DLC coating can not be applied to a tribological coating on soft substrates. To overcome this problem, a segment-structured DLC (S-DLC) coating has been suggested. In this technique, DLC film is divided into small segments by grooves. On the other hand, requirement for tribological application of DLC film under lubricant condition. However, sufficient research efforts have not been devoted toward S-DLC under lubricant condition. In this study, lubricated S-DLC film, which composed of S-DLC with grooves filled with grease, was investigated. Tribological properties of lubricated S-DLC were evaluated for various types of grease and segment shapes. It was shown that excellent tribological properties were obtained by combination of low viscosity grease and S-DLC coating with large size segments and narrow grooves.

Photovoltaic characteristics of a-C:H films prepared by plasma CVD

Summary form only given, as follows. In this study, we investigated photovoltaic characteristics of a-C-H films fabricated by two different deposition methods, one is RF plasma CVD (RF-PCVD) and the other is surface wave plasma CVD (SWPCVD).