The THM growth technology for 100 mm diameter CdTe single crystals has been intensively developed. In consequence of the optimization of growth conditions, we have succeeded in controlling growth interface shape and growing 100 mm diameter CdTe single crystals with 300 mm in length. Concerning the behavior of Te inclusions in the grown crystal, their size and density were investigated by IR transmission microscopy. The size distribution of Te inclusions was divided into two groups, and the density of them was less than 1 10 5 cm 3 . Charge transport properties of the grown crystal were investigated by using the " -model" spectral fitting method, and were found to be quite uniform all over the wafer. To investigate the homogeneity of radiation detector performances, Ohmic type and Schottky type detectors with 4 mm 4 mm 1 mm were fabricated from the left half and the right half of the 100 mm diameter wafer, respectively. Standard deviations of their energy resolutions for the 122 keV line from 57 Co were less than 6%. This excellent uniformity is essential for the room temperature semiconductor detectors in the major application areas, such as medical imaging, non-destructive inspection and homeland security.

No abstract

The electrooptic characteristics of a twisted nematic (TN) liquid crystal display (LCD) fabricated by doping Ag nanoparticles protected with NLC, 5CB (K-15, Merck) molecules have been investigated, and it is shown that the device exhibits a unique electrooptic response characteristic that is sensitive to the high-frequency components of the operating voltage together with the conventional root-mean-square voltage response. We call this device frequency modulation (FM) TN-LCD. The FM-TN-LCD is switched by switching the frequency of the operating voltage while its amplitude is kept unchanged. As an example, the frequency switched from 20 Hz to 500 Hz or 50 Hz to 2 kHz, and the switching is performed with the time constant of 21 ms for the rising process and 3 ms for the falling process. This device shows a peculiar response to a burst AC square wave, where the decay time is reduced by several times compared to that of an undoped TN-LCD. The mechanism of the FM-TN-LCD is investigated through the study of its dielectric properties.

No abstract

No abstract

Twisted nematic liquid crystal display (TN-LCD) devices, composed of nematic liquid crystal (NLC), doped with silver (Ag) nanoparticles, which are protected with the same NLC molecules of 5CB (Merck, K-15), show electrooptic characteristics that are featured by a frequency modulation and fast response. This device is called FM-TN-LCD. In this paper, we report that the frequency range in the FM-TN-LCD spreading from 40 Hz to an upper limit 2 kHz correlates with that of the dielectric dispersion of the sample cell, which is expressed analytically by the Maxwell–Wagner theory on the heterogeneous dielectric medium, where the dielectric relaxation frequency, and thus the dielectric relaxation time, are primarily governed by the electrical conductivity of the doped Ag nanoparticles.

Twisted nematic liquid crystal display (TN-LCD) devices, composed of nematic liquid crystal (NLC), doped with palladium (Pd) nanoparticles, which are protected with the same NLC molecules of 5CB (Merck, K-15), show electrooptic characteristics that are featured by a frequency modulation and fast response. This device is called FM-TN-LCD. In this paper, we report that the frequency range in the FM-TN-LCD spreading from tens Hz to an upper limit 1 kHz, depending on the concentration of nanoparticles, correlates with that of the dielectric dispersion of the sample cell, which is expressed analytically by the Maxwell–Wagner theory on the heterogeneous dielectric medium, where the dielectric relaxation frequency, and thus the dielectric relaxation time, are primarily governed by the electrical conductivity of the doped nanoparticles of Pd and their concentrations.

Pseudobinary compounds of column III elements and nitrogen are semiconductors widely studied for optoelectronic applications. Ga1- x B x N compounds are considered to be prone to phase separation due to the large difference in bond length between B–N and Ga–N. However if a sufficient amount of boron can be incorporated to Ga1- x B x N compounds, lattice matching with substrates such as SiC, AlN and Ga1- x Al x N may be achieved. We used molecular beam epitaxy to grow Ga1- x B x N films on sapphire c faces with various values of x. Single-phase wurtzite Ga1- x B x N with x up to 4.56% has been obtained.