Stabilization of silicon-based devices in ion-containing media using thin Al2O3 platelets and MoS2 oriented thin films

A simplified analogue to an Ion-Sensitive Field-Effect Transistor (ISFET) was tested in the presence of ions. The gate electrode in an ISFET is an aqueous solution, unlike in a Metal-Oxide Field-Effect Transistor (MOSFET) where the gate is a metal. A problem with the ISFET is that the insulating oxide between the silicon and the solution is slowly penetrated by various ions such as OH^– or Na⁺ causing a change in the characteristics of the device.The application of thin alumina platelets and thin MoS₂ films as a protective insulating layer, when deposited over the insulating silicon oxide, was tested against the penetration of ions. It is shown that there is a significant decrease in the ion penetration through to the silicon oxide layer, depending on the applied bias, when the oxide is covered with thin alumina or MoS2 layers. The effect of different ions and ion concentrations are presented. Suggestions for further improvement are made.     

Effect of a quantizing magnetic field on the capacitance of MOS structures of small-gap semiconductors

An attempt is made to investigate the effect of a quantizing magnetic field on the capacitance of MOS structures of small-gap semiconductors havingn-channel inversion layers under the weak electric-field limit. It is found, takingn-channel InSb as an example, that both the MOS and surface capacitances show spiky oscillations with changing magnetic field. It is further observed that the sharpness and the depths of the spikes increase with increasing magnetic field whereas the depths are found to decrease with increasing thickness of the insulating layer. On leave of absence from the Department of Physics, Patna University, Patna, India     

The effect of photoelectrochemical etching on the performance of CdS based photoelectrochemical cells

A photoelectrochemical etching technique which was formerly used to improve the performance of CdSe¹ and Cd(Se, Te)² based photoelectrochemical cells (PEC's) was further used to improve the short-circuit current and the fill factor of CdS based PEC's. It is suggested that this method can be used to improve photovoltaic cells having CdS as one of their components.     

On the gate capacitance of MOS structures of kane-type semiconductors under magnetic quantization

An attempt is made to formulate the gate capacitance of MOS structures of Kane-type semiconductors under magnetic quantization, without any approximations of weak or strong electric field limits, on the basis of the fourth-order effective mass theory and taking into account the interactions of the conduction, light-hole, heavy-hole, and split-off bands. It is found, taking n-channel Hg_1–x Cd _x Te as an example, that the gate capacitance exhibits spiky oscillations with changing magnetic field, which is in qualitative agreement with experimental observations, reported elsewhere, in MOS structures of the same semiconductor. The corresponding results for n-channel inversion layers on parabolic semiconductors are also obtained from the expressions derived.     

Application of BaF2-B2O3-GeO2-SiO2 glasses to metal-oxide-silicon field-effect transistors

The capacitance and voltage characteristics of field effect transistors passivated by BaF₂-B₂O₃-GeO₂-SiO₂ glasses with various water contents were investigated. As the OH absorption coefficients of the glass increased, adverse effects on the recovery of hysteresisC-V curve shifts was seen. The water content is related to the fluoride content of the BaF₂–B₂O₃–GeO₂–SiO₂ glass. The viscous flow point of the glass was lowered with increasing ionic character obtained from Hannay's equation. The source-drain current and voltage (I-V) characteristics of typical enhancement and depletion mode field effect transistors passivated with these glasses were investigated.     

Viscous How and MOS properties of CaF2-B2O3-GeO2-SiO2 glasses with ionic bonds

The capacitance and voltage (C-V) characteristics of Metal-Oxide-silicon (MOS) capacitors passivated by CaF₂B₂O₃-GeO₂-SiO₂ glasses with OH^– ions, water and fluoride contents were investigated. As the OH^– absorption coefficients of the glass increased, adverse effects on the recovery of hysteresis C-V curve shifts was observed. The content of OH^– ions is closely related to the fluoride content in the CaF2 B₂O₃-GeO₂-SiO₂ glass. The viscous-flow point of the glass was lowered with increasing degree of ionic character obtained from Hannay's equation.     

Ionic character of SrF2-B2O3-GeO2-SiO2 glasses for viscous flow and their applications to MOS capacitors

The capacitance and voltage (C-V) characteristics of metal, oxide, and semiconductors (MOS) capacitors passivated by SrF₂-B₂O₃-GeO₂-SiO₂ glasses with various water and fluoride contents were investigated. As the OH^– absorption coefficient of a glass increased, adverse effects on the recovery of shifts of the hysteresisC-V curve have been observed. The water content of ions is closely related to the fluoride content in the SrF₂-B₂O₃-GeO₂-SiO₂ glass. The viscous-flow transition point of glass was lowered with increasing degree of ionic character obtained from Hannay's equation.     

Double correlation technique (DDLTS) for the analysis of deep level profiles in semiconductors

A very sensitive technique is presented which can be applied to determine deep level profiles in space-charge layers of Schottky barriers orpn-junctions. The method uses an extended transient capacitance technique with correlation similar to Lang's DLTS technique. The extension of DLTS to double correlation DDLTS is necessary to resolve the deep level profile and to exclude the field dependence of the capture cross-section and contact effects. By using a double-pulse capacitance transient and correlation, these undesired effects can be subtracted. Profiles can be determined for deep levels at concentrations 10⁴ times lower than the background doping. Results are reported for epitaxial GaAs which showed one major deep level at 0.18 eV below the conduction band. Near the interface to the substrate, a slight shift in energy from 0.18 to 0.19 eV is observed. A second level at 0.43 eV decays into the epi-layer in the form of a diffusion tail.     

蓝宝石冲击消光晶向效应的第一性原理

蓝宝石的冲击消光现象是高压领域中的研究热点.低压段(86 GPa范围内)的实验研究表明蓝宝石的冲击消光与晶向相关,但在高压段(压力范围:131255 GPa)是否也具有晶向相关性目前尚不清楚.为此,利用第一性原理方法,分别计算了八个不同晶向的蓝宝石理想晶体和含氧离子空位缺陷晶体在高压段的光吸收性质,结果发现:1)蓝宝石在高压段的冲击消光表现出明显的晶向效应,且该效应还随压力增大而增强;一步的数据分析可以看出,在冲击实验采用的波段内,a晶向的消光最弱(透明性最好),c晶向的消光最强与c晶向的消光接近,g晶向的消光要弱于s晶向的消光.鉴于此,如果在高压段开展加窗冲击波实验,建议选择a晶向或m晶向的蓝宝石作为其光学窗口.本文结果不仅有助于深入地认识蓝宝石在极端条件下的光学性质,而且对未来的实验研究有重要的参考作用.     

Two-dimensional spatially ordered Al2O3 systems: Small-angle neutron scattering investigation

The structure of anodized aluminum oxide films has been investigated by the small-angle neutron scattering method. A theoretical solution is obtained for describing neutron scattering from the Al₂O₃ ordered porous structure. Analysis of the neutron-experiment data shows the possibility of obtaining porous membranes with ideally periodic hexagonal packed pores on a large area (～0.5 cm²).     

Structural and Magnetic Properties of the Al2O3/Ge-p/Al2O3/Co System

Technical Physics - The Al2O3/Ge-p/Al2O3/Co system with an Al2O3 buffer layer deposited by ion-plasma sputtering has been experimentally investigated. The dependences of the magnetic properties of...     

Reactions at the interface La0.5Ca0.5MnO3-YSZ/Al2O3 under anodic current

The reaction at the interface of a solid electrolyte cell between air electrode (La_0.5Ca_0.5MnO₃) and YSZ-electrolyte with different Al₂O₃-contents was investigated by electron microscopy (SEM) and x-ray diffraction (XRD). Formation of MnAl₂O₄ was detected in a 5 μm diffusion zone within the electrolyte. MnAl₂O₄ formation can be explained by diffusion of Mn-ions into the electrolyte and subsequent reaction with the α-Al₂O₃ grains during sintering. Cell performance and long-term stability in SOFC operation are not negatively affected by MnAl₂O₄ formation. However a rise in electrode resistance and slow delamination of perovskite oxide electrode were observed after some hours of electrolysis. This reaction is the consequence of oxygen gas pressure at the electrolyte in the MnAl₂O₄ diffusion zone. It is caused by local increase of electronic conductivity by MnAl₂O₄ formation. Long-term stability also for electrolysis conditions has been achieved by an additional intermediate YSZ-layer between air electrode and electrolyte. Paper presented at the 3rd Euroconference on Solid State Ionics, Teulada, Sardinia, Italy, Sept. 15–22, 1996     

An X-ray investigation of the high temperature anomaly in pure V2O3

An X-ray investigation of pure V₂O₃ in the temperature region 300 to 700 K has revealed the presence of more than one phase coexisting from ≈450 to at least 700 K. This observation can be correlated with the high temperature resistivity anomaly and with recent nmr studies on this material.     

A study of lattice defects in solids belonging to Al2O3−B2O3 and Al2O3−SiO2 systems by thermoluminescence experiments

Summary Spectrally resolved thermoluminescent emission has been investigated in solids belonging to Al₂O₃−B₂O₃ and Al₂O₃−SiO₂ systems. These solids, which are characterized by a structure like that of alumino-silicate mullite, contain a high density of oxygen and aluminum or boron lacunae. This fact favours the occurrence of both-sign interstitial ions acting as carrier traps. The results show a close similarity with those obtained when studying, with the same experimental method, the thermoluminescent emission of alumina. The overall analysis of data allows for reliable conclusions on the nature of crystal defects in these materials.     

Investigation of the solid-solid surface adsorption of Eu2O3 on amorphous Al2O3

Solid-solid surface adsorption of Eu₂O₃ on anorphous Al₂O₃ have been investigated by the Mössbauer effect, X-ray diffraction analysis (XRD.) and Laser Raman Spectroscopy (LRS). The results of these studies indicate that the structure of EU₂O₃ dispersed onto the support surface depends on the structure of support and that there is an inductive effect of the support on the structure of the Eu₂O₃.     

V centers in single crystal Al2O3

From optical and thermal bleaching experiments it is concluded that the 400 nm absorption band which appears in Al₂O₃ after γ-irradiation is a composite V band. One of its components is attributed to the V^-_OH center which also is responsible for a localized vibrational band at 3316 cm^-11 analogous to the one observed for the V_OH center in MgO. The irradiation also results in electron trapping at Cr³⁺ impurity ions to produce a band at 227 nm. Annealing at 170°C destroys the V^-_OH center by releasing holes which convert the Cr²⁺ to Cr³⁺ with an attendant thermoluminescence.