Yuji Kiuchi

Impedance Spectra of p‐Type Porous Si‐Electrolyte Interfaces

Frequency dispersion of the impedance of the p‐type porous Si layer (PSL)/aqueous electrolyte interface has been investigated to characterize its electrical properties. The PSL electrodes are formed on (100) p‐Si substrates (3.5–4.5 Ωcm in resistivity) by anodic treatment in solution. Impedance measurements over a wide frequency ranging from 2 Hz to 100 kHz are carried out as a function of PSL thickness. At low frequencies and low bias voltages, the impedance shows the characteristic behavior expected from the microporous structure. The flatband potential at the rear surface of PSL, determined from Mott‐Schottky plots, shifts to the negative side with increasing PSL thickness. This is presumably related to the ionic adsorption in PSL.

The Current‐Voltage Characteristics of a Photoelectrochemical Cell Using p‐Type Porous Si

Fundamental characteristics of a photoelectrochemical cell using p-type porous-Si layer (PSL) as a semiconductor photoelectrode were measured. The PSL electrode exhibited stable photodiode characteristics. The increase in the PSL thickness was very useful in suppressing the dark current, although it resulted somewhat in reducing the photosensitivity, due to the increase in surface recombination losses of photogenerated carriers.

Photoelectrochemical Behavior of n-Type Porous-Si Electrodes

A prolonged photoanodic operation of n-type Si in aqueous electrolytes was observed with porous-structure Si electrodes. The n-type porous-Si layers (n-PSL) were formed on n-Si substrates (1-2 Ωcm in resistivity) by anodic treatments in an HF solution. The total output charge Q obtainable from a n-PSL photoelectrochemical cell increased in proportion to the n-PSL thickness d. At d = 50 µm, Q reached 12.5 C/cm2; this was four orders of magnitude greater than was obtained from naked n-Si photoanodes. The H2 evolution rate from the Pt counterelectrode was about 60 µmol/2 h at d = 30 µm. The experimental results of the spectral response suggest an increase in the surface state density of the n-PSL surface with increasing d.

Calculations of Image Lag in Vidicon-Type Camera Tubes. I. Beam Discharge Lag and Total Image Lag, Including Photoconductive Lag

Image lag in vidicon-type camera tubes is analyzed, taking scanning processes with a low-velocity electron beam into consideration. As the beam landing characteristics, not only usual form of ib=Ibexp (av) but also newly invented one of ib=Ib/{1+exp (-av)} are employed. The latter shows much better agreement to the measured characteristics than the former, but the difference between them is negligible at the regions where image lags become troublesome. First, by expressing target surface potentials and target output currents in exponential forms, the relationship between them is obtained analytically and presented graphically as the target surface potential curves under steady state conditions. Then, the fundamental expressions for beam discharge lag or capacitive lag are obtained for both rise and decay by applying the above-mentioned relationship to transient cases. Finally, the total image lag, including photoconductive lag, is analyzed. From the results obtained by computer calculation, the general features of image lag and the lower limit of image lag are known.

Characterization of traps at nitrided SiO2/SiC interfaces near the conduction band edge by using Hall effect measurements

The effects of nitridation on the density of traps at SiO2/SiC interfaces near the conduction band edge were qualitatively examined using a simple, newly developed characterization method that utilizes Hall effect measurements and split capacitance–voltage measurements. The results showed a significant reduction in the density of interface traps near the conduction band edge as a result of nitridation, but the interface traps were not completely eliminated by nitridation.

Observation of a Long-Life Photoelectrochemical Conversion with n-Type Porous-Si Photoelectrodes

Application of an n-type porous-Si layer (PSL) as a working electrode of a photoelectrochemical cell was investigated. The introduction of the porous structure produced a drastic improvement in the life of n-Si under photoanodic operation. A linear relationship between the total output charge and the PSL thickness was found. At a PSL thickness of 20 µm, the photoanode remained alive until several C/cm2 charges were passed; this was three orders of magnitude more than was obtained from naked n-Si photoanodes. The H2 evolution rate from Pt counterelectrode was then about 100 µmol/10 h. The prolonged operation is closely related to an enhanced active area.

Electrical and physical characterizations of the effects of oxynitridation and wet oxidation at the interface of SiO2/4H-SiC(0001) and

The effects of oxynitridation and wet oxidation at the interface of SiO2/4H-SiC(0001) and were investigated using both electrical and physical characterization methods. Hall measurements and split capacitance–voltage (C–V) measurements revealed that the difference in field-effect mobility between wet oxide and dry oxynitride interfaces was mainly attributed to the ratio of the mobile electron density to the total induced electron density. The surface states close to the conduction band edge causing a significant trapping of inversion carriers were also evaluated. High-resolution Rutherford backscattering spectroscopy (HR-RBS) analysis and high-resolution elastic recoil detection analysis (HR-ERDA) were employed to show the nanometer-scale compositional profile of the SiC-MOS interfaces for the first time. These analyses, together with cathode luminescence (CL) spectroscopy and transmission electron microscopy (TEM), suggested that the deviations of stoichiometry and roughness at the interface defined the effects of oxynitridation and wet oxidation at the interface of SiO2/4H-SiC(0001) and .

Universal parameter evaluating SiO 2 /SiC interface quality based on scanning nonlinear dielectric microscopy

Oxidized both silicon-face (Si-face) and carbon-face (C-face) wafers with various post-oxidation-annealing conditions were measured by scanning nonlinear dielectric microscopy (SNDM) and method for evaluating SiO2/SiC interface quality using SNDM was investigated. We found that the normalized standard deviation of SNDM image was good parameter to evaluate SiO2/SiC interface of Si and C-face. SNDM measurement does not need electrode fabrication to measure C-V curve, but needs just scan on the oxidized wafer with conductive tip, which is easier and quicker. This technique enables us to quickly examine the effect of variation of process parameters in MOS fabrication and to effectively reduce the time needed for R&D cycle.

Improved PbO-PbS Infrared Vidicon

PbO-PbSターゲットを用いた赤外用ビジコンは一般に残像が多く, 動く物体を撮像するときには障害となっていた.筆者らは, 光導電ターゲットの新しい製作方法によって光応答特性を著しく改善し, 残像の少ない (3フィールド目で10%程度) 赤外用ビジコンを試作することができた.試作管は, 可視光から波長2μくらいまでの光に感度があり, 200℃以上の高温物体をも撮像することができ, 赤外用ビジコンの応用範囲の拡大が期待される.

Characteristics and an Operation Model of an Experimental CdSe-Vidicon

CdSeの蒸着焼結膜をターゲットに使って超高感度ビジコンを試作した.感度は従来の管の数十倍で, 量子効率は1を越している.残像も従来のビジコン程度であるが, 光量の少ないところでは長くなる.このビジコンの動作モデルとして, 光で励起された正孔がターゲット内の空間電荷を軽減するために, 電子がビームからターゲットの中へ多数流れ込んで信号を発生するという考え方を提案し, CdSeビジコンの諸特性の測定結果と比較考察した.また, 1より大きな利得を生ずることから, 自由電子の流れは必ずしもトラップと熱的な平衡を保たないということが推測される.