Most near-infrared spectroscopy (NIRS) apparatus fails to isolate cerebral oxygenation from an extracranial contribution although they use different source-detector distances. Nevertheless, the effect of different source-detector distances and change in extracranial blood flow on the NIRS signal has not been identified in humans. This study evaluated the extracranial contribution, as indicated by forehead skin blood flow (SkBF) to changes in the NIRS-determined cerebral oxyhaemoglobin concentration (O2 Hb) by use of a custom-made multidistance probe. Seven males (age 21 ± 1 year) were in a semi-recumbent position, while extracranial blood flow was restricted by application of four different pressures (+20 to +80 mmHg) to the left temporal artery. The O2 Hb was measured at the forehead via a multidistance probe (source-detector distance; 15, 22·5 and 30 mm), and SkBF was determined by laser Doppler. Heart rate and blood pressure were unaffected by application of pressure to the temporal artery, while SkBF gradually decreased (P<0·001), indicating that extracranial blood flow was manipulated without haemodynamic changes. Also, O2 Hb gradually decreased with increasing applied pressure (P<0·05), and the decrease was related to that in SkBF (r = 0·737, P<0·01) independent of the NIRS source to detector distance. These findings suggest that the NIRS-determined cerebral oxyhaemoglobin is affected by change in extracranial blood flow independent of the source-detector distance from 15 to 30 mm. Therefore, new algorithms need to be developed for unbiased NIRS detection of cerebral oxygenation.

The thermal reaction of a vacuum-evaporated Ti film with substrate GaAs has been investigated using Auger electron spectroscopy and x-ray diffractometry. As accumulation and Ga depletion at the Ti/GaAs interface and Ga pileup in front of the As-rich layer have been observed. The As-rich and the Ga-rich layers have been found to be composed of TiAs/Ti5As3 and Ti2Ga3/Ti5Ga4, respectively. It has also been found that the rate of the Ti-GaAs reaction is governed by the interdiffusion process of Ti and As at the interface with an activation energy of 1.70±0.05 eV. The low diffusivity and relatively high Schottky barrier height of the present system facilitate the formation of useful Schottky barrier junctions.

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This paper presents the 45OOV-75OA planar gate IEGT (P-IEGT), which has wide cell width. Increasing gate width, the planar devices achieves the carrier injection enhancement effect. Wide gate structure shows better characteristics for high voltage planar devices than the conventional IGBT. The on-state vloltage drop is 3.8V a t 50Ncm2 ,Tj=25"C. The value is low enough for 4500V rated MOS gate transistor. We achieve turn off capability at Vce(peak)=4000V, Ic=1600A without adding dvjdt snubber a t T~=125 "C . The result shows that P-IEGT has very wide SOA.

A new deposition technique for molybdenum silicide films is presented whereby the films are deposited by magnetron‐d‐c‐reactive sputtering using a Mo target in a silane argon atmosphere. The influence of sputtering conditions upon the film properties was investigated by utilizing mass spectroscopy, Auger electron spectroscopy, and x‐ray diffractometry. Films with various Si/Mo atomic ratios up to 1.9 were obtained by controlling the sputtering power and the silane partial pressure. The crystal structures were found to be continuously transformed from Mo‐rich silicides to Si‐rich ones, including Mo3normalSi , Mo5Si3 , and MoSi2 , with increasing Si/Mo atomic ratio.

An improvement is made on the technique of determining the impurity density in a semiconductor from C-V measurements. It is shown that the average impurity density inside the depletion region plays a major part in precise determination of shallow and deep impurity profiles. Measurements of time variation of the bias voltage with the capacitance unchanged are useful for deep levels, and make it feasible to gain knowledge of their energy levels and density profiles simultaneously. These techniques are successfully applied to n-type VPE GaAs on Cr-doped semi-insulating substrates.

A method is proposed for the determination of deep impurity levels and density profiles from C–V measurements and is demonstrated on GaAs Schottky barrier diodes. The technique involves measurements of the time dependence of the bias voltage instead of the barrier capacitance. The spatial distribution of a deep level is observed to exhibit a peak at the boundary between an epitaxial layer and the semi-insulating substrate. This deep center is located 0.8 eV below the conduction band.

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