Kiichi Kamimura

Preparation of polycrystalline SiC films for sensors used at high temperature

Abstract Polyerystalline silicon carbide (SiC) films have been prepared by plasma-assisted chemical vapour deposition. Pressure sensors are fabricated using the polycrystalline SiC films as piezoresistive sensing elements to show their applicability for a pressure sensor. The elements are formed by plasma etching. The sensitivity is 2.2 mV/ (kg/cm 2 ), and the non-linearity (deviation from linear relation) is less than 1% of full scale.

Preparation and Piezoresistive Properties of Polycrystalline SnO2 Films

Tin oxide thin films were deposited by dc magnetron sputtering in a gas mixture of Ar and O2 using a target containing antimony. The films were characterized using X-ray diffraction. The films showed preferred orientation in a or plane. The properties of films depended on the substrate temperature and the gas flow ratio of Ar/O2. The piezoresistive properties of these films have been measured using a conventional cantilever method. The gauge factor was measured to be around negative 5–20 at room temperature, which is comparable to the gauge factor of polycrystalline silicon films.

Preparation of carbon nanofibers by hot filament-assisted sputtering

Abstract Crystalline carbon thin films containing carbon nanofibers were obtained by using a hot filament-assisted sputtering system. Pure argon gas was employed as the sputtering gas. The crystal structure of the carbon thin films was investigated by XRD, XPS, TEM and TED. XPS profiles show the compositions of the films, which consisted of over 90% carbon atoms. From the results of observations using TEM and TED, it was revealed that the crystalline carbon films consisted of nanocrystal grains and nanofibers. To determine the valence state (sp 3 , sp 2 and sp hybridization) of the carbon atoms in the films, laser raman spectra were examined and it was found that the films showed three Raman bands at 1581, 1368 and 1979 cm −1 . The first two peaks belong to polycrystalline graphite and the last peak corresponds to carbyne, one of the allotropes of carbon.

Preparation and properties of boron thin films

Abstract Boron thin films were deposited by pyrolysis of decaborane. The substrate was heated up to 1200 °C by infrared irradiation from a halogen lamp. The films were characterized by electron beam diffraction, XPS and electrical measurements. Spots and rings were observed in the electron beam diffraction patterns, which indicates that the films consist of α-rhombohedral boron. The activation energy of the conductivity was 0.1–0.3 eV from R.T. to 500 °C and 1.0–1.4 eV above 500 °C. This demonstrates that infrared radiation is an effective method in obtaining high quality boron films via the pyrolysis of decaborane.

Properties of Schottky Barriers on p-Type Indium Phosphide

Schottky contacts to the p-type InP have been fabricated and their electrical characteristics have been measured. The barrier height more than 0.8 eV are obtained with the contacts to the low work function metal such as Al, In, Sn and Sb. The barrier height is dependent upon the metal work function under the given metals. The surface state density is estimated to be 3.4×1012 cm-2 eV-1 from the barrier height versus the metal work function plot. The open circuit voltage and the energy conversion efficiency of the p-type InP Schottky barrier solar cell are 0.595 V and 8.2% under AM2 condition.

Preparation of a Thin Silicon Nitride Layer by Photo-CVD and Its Application to InP MISFET's

Thin silicon nitride (SiNx) layers have been successfully prepared by photochemical vapor deposition (photo-CVD) technique. Ellipsometric and X-ray photoelectron spectroscopic studies prove that the refractive index and concentration of nitrogen in the layer are strongly dependent on the substrate temperature. The interface state density at the SiNx/InP interface is estimated to be 8×1011 cm-2 eV-1 from the capacitance-voltage characteristics of InP MIS diodes. Using SiNx layer as a gate insulator, InP MISFETs were fabricated on semi-insulating InP substrates.

Y-Ba-Cu-O Thin Films Formed on Alumina Ceramic Substrates Coated with Yttria Stabilized Zirconia Layer

Y–Ba–Cu–O thin films have been deposited by DC magnetron sputtering on alumina ceramic substrate coated with yttria stabilized zirconia layer (YSZ). The YSZ layer acted as the buffer layer between the alumina ceramic substrate and the Y–Ba–Cu–O thin film. The temperatures of superconducting onset and zero resistance were 95 K and 47 K, respectively.

Characterization of Nitride Layer on 6H-SiC Prepared by High-Temperature Nitridation in NH3

The nitride layers were prepared by direct thermal nitridation of 6H-SiC substrates at 1200–1570°C in a NH3 atmosphere. The layer was characterized by using X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and Raman scattering spectroscopy. The thickness of the nitride layers prepared at lower than 1400°C was estimated to be less than 10 nm. The higher nitridation temperature resulted in the formation of a thicker surface layer. XPS measurement showed that the surface layer was composed of N, Si, C and O. Peaks corresponding to α-Si3N4 were detected in the Raman spectra and the XRD patterns of the sample prepared at higher than 1500°C, indicating the crystallization of the nitrided layer.

Contact Resistance of SnO2 Films Determined by the Transmission Line Model Method

The specific contact resistance of SnO2 thin films was estimated by the transmission line model (TLM) method. The values were on the order of 10-6–10-4 Ωm2. The sample was annealed in N2 atmosphere at 200–650° C. The TLM measurement before and after annealing indicated that annealing was not effective in reducing the contact resistance. The high-temperature annealing resulted in the increase in both the specific contact resistance and the sheet resistance of the SnO2 thin film.

Thermoelectric power of polycrystalline Si films prepared by microwave plasma chemical vapour deposition

The thermoelectric properties of silicon (Si) thin films prepared by microwave plasma chemical vapour deposition were studied. For preparation, monosilane (SiH4) was used as the source gas, and phosphine (PH 3 ) and diborane (B 2 H 6 ) were used as the doping gases. X-ray diffraction shows that Si films were polycrystalline and that the average grain size of these films was approximately 100 nm. Measurement of the thermoelectromotive force between Si films and the counter electrodes revealed that the thermoelectric power depends on the flow rate of the doping gas, and that the Si films prepared at the B 2 H 6 /SiH 4 flow rate of 0.05% showed a maximum thermoelectric power of approximately 0.9 mV K -1 .