Yoshiaki Matsumae

Formation of ohmic contacts on semiconducting diamond grown by chemical vapour deposition

Abstract The current-voltage (I–V) characteristics and the contact resistance Rc of Au/, Al/ and Mg/chemically vapour deposited semiconducting diamond contacts were measured. The I–V characteristics of Al/ and Mg/p-diamond contacts changed their properties from an ohmic to a rectifying nature as the resistivity of the semiconducting diamonds increased, while the Au/p-diamond contact was ohmic. An Rc of less than 103 Ω cm2 is found to be necessary to obtain the ohmic contacts on semiconducting diamonds regardless of the metal. The rough estimate of the barrier height oB was also discussed using the results of the Rc measurement.

Space charge limited current in semiconducting diamond films

A trap-limited space-charge-limited current (SCLC) in diamond p-i junction diodes is studied. Diodes are prepared by the hot filament chemical vapor deposition method. The SCLC is ascribed to the positive charge due to holes injected from the p-type diamond layer into the intrinsic (i)-type diamond layer. According to the method proposed by Rose [Phys. Rev. 97 (1995) 1538], the existence of trap levels which are distributed exponetially in the energy gap is confirmed. The distribution profile and the concentration of traps per unit energy and cubic centimeter are deduced by examining current-voltage characteristics which are experimentally obtained.

Optimizing the ice crystal scattering database for the GCOM-C/SGLI satellite mission

In this study, the grid system of the complex refractive index in the 1.6-μm (SW3) channel of the Global Change Observation Mission (GCOM-C)/Second Generation Global Imager (SGLI) satellite sensor is investigated. This grid system is separated into twelve patterns according to the step size of the real and imaginary parts of the refractive index. Specifically, the Light Scattering solver Applicable to particles of arbitrary Shape (LISAS)/Geometrical-Optics Approximation (GOA) technique is used to simulate the scattering of light by randomly oriented large hexagonal ice crystals. The difference of radiance with refractive index step size is calculated from developed light scattering database using the radiative transfer (R-STAR) solver. The results indicated that the step size of the real part is a significant factor in the difference of radiance.

New cloud science derived from GCOMC satellite mission

The Global Change Observation Mission (GCOMC)/Second Generation Global Imager (SGLI) is an passive optical radiometer for monitoring climate change, which is scheduled to launch in around 2014 by the Japan Aerospace eXploration Agency (JAXA). The SGLI sensor is an optical sensor capable of multi-channel observation at wavelengths from near-UV to thermal infrared. The SGLI consists of two radiometer instruments, the Visible and Near Infrared Radiometer (VNR) and the Infrared Scanner (IRS). SGLI-VNR is capable of observing polarized and non-polarized radiance. In the GCOMC satellite mission, cloud properties such as the cloud optical thickness, the effective particle radii, and the cloud top temperature will be retrieved from SGLI-VNR data. The International Satellite Cloud Climatology Project (ISCCP) cloud product will be produce and cloud inhomogeneity of the warm water cloud will be discussed. This is one of the new sciences of the GCOM-C satellite mission in terms of cloud sciences. Furthermore, ice crystal scattering database will be developed for ice cloud remote sensing.