Changes In Surface State Research Articles

Oxygen diffusion and reaction at annealed InSb MOS interfaces

We investigated the effects of heat treatments on the interfacial chemical and electronic properties of InSb metal-oxide-semiconductor (MOS) structures, prepared by wet anodization. Results of in-depth profiling of the heat-treated passivation films, using high-resolution Auger electron spectroscopy (AES), including line-shape analysis and deconvolution techniques, reveal important information on changes in the layers' structure and composition. Among the salient trends, we note that annealing at increasingly elevated temperatures monotonically enhances the extent of O in-diffusion, increases the width of the In-In oxide and Sb-Sb oxide interfaces, and changes their overlap and relative positions. The electrical features observed in the capacitance-voltage ( C-V) curves, such as flat band voltage, hysteresis, and other deviations from the ideal C-V curves, are explained in terms of changes in surface states and charges. The effect of the heat treatments was noted by a marked decrease in the oxide trap and fast interface state densities, whereas the fixed oxide charge density increased. The significant dependence of all the features on the annealing temperatures facilitates the assignment of electrically active species to different spatial positions and oxidation states of In and Sb at the oxide layers and at their interfaces. The electrical properties of these MOS structures are shown to be considerably improved by annealing at relatively low temperatures (below 250°C).

Photoemission from H adsorbed on Ni(111) and Pd(111) surfaces.

The electronic states of H chemisorbed onto the Ni(111) and Pd(111) surfaces are investigated as a function of H concentration using angle-resolved photoelectron spectroscopy and synchrotron radiation as the light source. Exposure of either crystal surface to molecular ${\mathrm{H}}_{2}$ results at low temperature in adsorption of approximately one monolayer of atomic H. This saturation coverage of H is characterized by a H-induced band split off from the bulk bands with 1\ifmmode\times\else\texttimes\fi{}1 dispersion and by dramatic changes in the d-band surface states. As the H concentration is decreased, the split-off state moves upwards towards the bulk bands at all k${\ifmmode\bar\else\textasciimacron\fi{}}_{?}$ until it disappears at a H concentration of \ensuremath{\sim}0.5 [0.3] of the saturation coverage for Ni(111) [for Pd(111)]. In contrast to the behavior of the split-off state the substrate surface states shift continuously with H concentration. We propose that the split-off state results from the attractive H potential but its dispersion is dictated by the substrate symmetry.

The study of slow relaxation of charged centres in insulator–semiconductor structures using fluorescent molecule probes

The insulator charge relaxation and corresponding change of the fast surface state in the semiconductor–oxide system are investigated. The fluorescence of adsorbed dye molecules is used for the differential anlaysis of the electronic and ionic charge relaxation in an insulator. It is found that charge relaxation is accompanied by the following effects: fluorescence decay, spectral shift of fluorescence maximum, and the change of the fluorescence anisotropy coefficient. [Russian Text Ignored].

Removal of colloidal particles in electroflotation

AbstractThe collection mechanism of polystyrene latices of 0.6 μm in diameter in electroflotation has been examined both theoretically and experimentally as extension of our previous work (1980). To avoid the change of surface state of particle bubble, the experiment was conducted under the condition that the concentration of CTAB (cetyl trimethylammonium bromide), cationic surfactant in the solution, is within the 90% of its initial concentration. It is of interest that the theory predicts the collection efficiency to vary as d.

Comparison of Fatigue Processes in 0.45%C Steel Specimens Polished under Different Conditions

Rotating bending fatigue tests were made on specimen which were polished longitudinally or circumferentially with two kinds of silicon carbide papers and then elecro-polished. The fatigue processes were observed successively by the two stage plastic replica method, with special attention given to the starting points of a final fracture . The materials used are a normalized S45C steel, and a quenched and tempered S45C steel. The main results obtained are as follows : (1) Non-propagating micro-cracks are observed on the surfaces of the specimens after 107 cycles of the fatigue limit. (2) The characteristics of a change in surface states due to stress repetitions can be explained in terms of the notch sensitivity of the material and the roughness of the specimen surface.

Comparison of fatigue processes in 0.45% C steel specimens polished under different conditions.

Rotating bending fatigue tests were made on the specimens which were polished longitudinally or circumferentially by two kinds of silicon carbide papers and then electro-polished. The fatigue processes were observed successively by the tow stage plastic replica method, with special attention being given to the starting points of final fracture. The materials used are a normalized S 45 C steel, and a quenched and tempered S 45 C steel. The main results obtained are as follows. (1 Non-propagating micro-cracks are observed on the surfaces of specimens after 107 cycles of fatigue limit. 2) The characteristics of the change in surface states due to stress repetitions can be explained based on the notch sensitivity of the material and the roughness of the specimen surface.

Temperature-Dependent Surface States and Transitions of Si(111)-7×7

uv photoemission and electron-energy-loss measurements of Si(111)-7 \ifmmode\times\else\texttimes\fi{} 7 between $T=15 \mathrm{and} 300$ K reveal significant temperature-dependent changes in the occupied surface states and their transitions which can be associated with electron-phonon coupling at the surface. Several new surface states and transitions are determined at low temperatures, including a highly localized (\ensuremath{\sim}2-meV-wide), half-occupied state that resides within a 100-meV-wide surface-state band gap and determines the Fermi-level position.

Surface Analysis of LaB6 Single Crystal Thermionic Emitters

Surface analysis of heated LaB6 thermionic emitter is made by means of Auger electron spectroscopy. Changes in surface state with changing emitter temperature and ambient oxygen pressure are investigated. The emitter temperature is varied from room temperature to 1700°C, and the oxygen pressure from 1×10-5 Pa to 7×10-3 Pa. With the increase of temperature the emitter surface passes through four states depending on oxygen pressure, before it reaches a clean state. Among them a state is particularly noteworthy that the emitter surface is covered with a layer of lanthanum oxide just before assuming the clean surface state. A surface state diagram is shown. The optimum conditions of emitter temperature and oxygen gas pressure to exhibit high emission properties are described.

The surface pressure dependency of the enzymatic hydrolysis of lipid monolayers enzyme denaturation at the air-water interface

Insoluble monolayers of dioctanoyl lecithin show a change in surface state at pressures near 3.5 dynes/cm, as judged by surface potential-surface concentration measurements and from surface-pressure area data. The phospholipase A 2 of Crotalus atrox venom and one from porcine pancreas show no surface-pressure rate dependency when acting upon a given state of dioctanoyl lecithin monolayer, but the rate changes at the surface state discontinuity. The ratio of the rate constants in the higher and lower pressure regions is 2.1 for the C. atrox enzyme and 1.4 for the pancreatic enzyme. In contrast to this straightforward kinetic behavior, the rates of hydrolysis catalyzed by the honeybee venom enzyme and a second pancreatic phospholipase increase continuously with the surface pressure. The anomalous surface pressure dependency correlates with the tendency of these enzymes to denature at clean air-water interfaces, and with the accumulation of inactive protein at the surface. The rate of enzyme denaturation is proportional to the area not covered by substrate molecules. Inert substances covering the surface prevent denaturation and eliminate surface pressure dependency of the enzymatic rate. Using a kinetic scheme based upon this free area denaturation model, minimum free areas for denaturation of 500 and 900 A 2, and surface denaturation rate constants of 3.9 × 10 5 sec −1 and 1.1 × 10 9 sec −1 are calculated for the pancreatic and bee venom enzymes, respectively. The surface denaturation model is consistent with all pertinent data that have been published for enzymes that act upon lipid monolayers.

Changes in Surface State and Stress Amplitude under Two Strain Levels in Low Cycles Fatigue of Electro-Polished Carbon Steel Specimens

Changes in Surface State and Stress Amplitude under Two Strain Levels in Low Cycles Fatigue of Electro-Polished Carbon Steel Specimens

Electron paramagnetic resonance investigation of the surfaces of Si-Ge alloys

Clean surface of a full range of Si-Ge alloys have been prepared by crushing in ultrahigh vacuum (10−9 Torr) and measured by the electron paramagnetic resonance technique at room temperature and 77 K. From the 92 % Si alloy, a signal was found with properties (g ≑ 2.0063, width about 16 G and height increased by exposure to oxygen) which are similar to the pure Si surface signal. Analysis of this signal provides support for the non-localised character of the surface signal from pure Si. In the case of pure Ge and the other alloys (Si contents:77 %, 55 %, 34 % and 11 %), a broad signal was found (g ≑ 2.015, width about 40 G). This signal increased by at least twenty times on cooling to 77 K from room temperature and was also greatly increased by exposure at 77 K to oxygen, but the latter effect was due to desaturation. The appearance of this signal at Ge concentrations greater than about 10% is correlated with a significant change in the bulk band structure at this concentration, leading to a change in surface states. The temperature behaviour is explained by a change in Fermi level with respect to the surface states.

Change of Electrical Resistivity of Graphite Powder During Heating in Air

The electrical resistivity of the powder of high purity artificial graphite was measured from room temperature up to 600°C. The change of the resistivity during heating in air was classified to several steps; i) between 200° and 300°C, the resistivity decreases slightly with time, ii) between 300° and 330°C, the resistivity decreases abruptly and temporarily, iii) between 340° and 360°C, the resistivity increases slightly, iv) above 400°C, the resistivity decreases abruptly, and v) at about 600°C, the resistivity increases abruptly. From comparison of these changes shown in argon, in vacuo, and at reheating, and with thermogravimetric changes at same C41ditions, these changes of resistivity could be connected with the following changes of surface state, respectively; i) formation of unstable surface oxide (Cf*-+C*(0)), ii) decomposition of unstable surface oxide (C*(0)-Cf), iii) formation of stable surface oxide (Cf-+C(0)), iv) decomposition of stable surface oxide (C(0)→Cl), and v) regeneration of active surface site (Cf-Cf*). Then the contribution of the surface state to the electrical resistivity of graphite powder can be expressed asPc r. P C. (0) Pcf and Pc (o) Pc, where pc, . means the specific resistivity of powder aggregate of the graphite which has Cr* surface state, and so on.

硫化鉱物の界面構造の変化に及ぼす溶存酸素の影響

In order to make clear the mechanism of the improved reaction between xanthate ion and sulphide mineral due to the dissolved oxygen, the change of the electronic state at the mineral surface was examined.The capacitance on the surface of the single crystal of galena and sphalerite was measured to investigate the variation of the flat band potentials by the adsorption of oxygen.The flat band potentials of both galena and shalerite are more noble in a solution containing dissolved oxygen than in a solution free from oxygen.From the results, it is considered that the adsorption of oxygen on mineral surface causes the change in the electronic surface state of the mineral and forms the surface state in which positive charges on the mineral surface are increased relatively according to the acceptance of electrons by oxygen.

Change in Surface States and Incipient Fatigue Cracks in Electro-Polished Low Carbon Steel (Plain and Notched Specimens) under Rotating Bending Stress

Using electro-polished low carbon steel specimens, the change in surface states and the incipient fatigue cracks of plain and notched specimens subjected to rotating bending stress were investigated. The main results obtained are as follows. (1) When the limit stress for macro-crack initiation σw1 is repeated, the amount of slip bands appearing at the root of notch is nearly equal, not only after 107 cycles but also at every cycle ratio, even if the maximum stress ασw1 at the bottom of notch is different in various radii of the notches. (2) In the specimens with various radii of the notches, the limit stress for slip bands initiation σws is almost proportional to the stress σw1, that is, σwsb(0.85∼0.9)σw1. (3) The incipient fatigue cracks, which appear on plain specimens after 107 cycles of the stress σw1, can hardly sustain the tensile stress statically and dynamically.

The Change of Surface States and the Incipient Fatigue Cracks in Electro-polished Low Carbon Steel (Plain and Notched Specimens) Subjected to Rotating Bending Stress

The Change of Surface States and the Incipient Fatigue Cracks in Electro-polished Low Carbon Steel (Plain and Notched Specimens) Subjected to Rotating Bending Stress

The oxidation of CO by O 2 and by NO on supported chromium oxide and other metal oxide catalysts

The oxidation of CO by NO and by O 2 has been studied on a number of supported transition metal oxide catalysts. On supported chromia the oxidation of CO by NO is faster than by O 2; however, with mixtures of NO and O 2 the reaction is selective towards O 2. The application of continuous mass-spectrometer monitoring to the study of surface state changes in chromia catalysts is outlined. The method was extended to determine the oxidation state of the surface in situ during reaction. In the oxidation-reduction cycle involving alternate passage of HeCO and HeO 2 mixtures at 500 °, the majority of the surface atoms undergo a change of oxidation state from Cr 6+ to Cr 2+. The extent of this change diminishes with decreasing temperature. Mixtures of He and NO oxidize the surface of supported chromia to a lesser extent than HeO 2. During the CONO reaction the average surface oxidation state is lower than in the presence of oxygen. A tentative explanation is offered for the selectivity for oxygen over nitric oxide in the oxidation-reduction reactions on commonly employed catalysts.

Surface photovoltage measurements in vapour-deposited CdS

Surface photovoltage has been measured in vapour deposited CdS using metal-insulator-semiconductor structures. The photovoltage was measured using a.c. techniques. The surface potential at thermal equilibrium was studied as a function of the types of insulators used and the various surface treatments given to the CdS films. A depletion region with a surface barrier as high as 200 mV was measured with either vapour deposited CaF 2 or MgF 2 as the overlying insulator. For the CdS-SiO interface, a depletion region was found with a surface potential which varied between 20 and 100 mV, depending on the deposition procedure for the SiO films. The dependence of the photovoltage on light intensity is in good agreement with calculated values neglecting charge changes in the fast surface states, and is therefore at least consistent with previously reported results on fast surface states in vapour deposited CdS. The values of surface potential obtained have been compared to values obtained from field-effect capacitance measurements and good agreement was obtained. The significance of these results as pertains to the thin-film field-effect transistor is discussed.

光沢スズ電気メッキの結晶構造

The states on surface and cross-section of electroplated bright tin deposit and the effects of annealing on its crystal structure were observed with microscope, electron microscope, and X-ray diffractometer. The results were compared with those of other non-bright tin deposits.The results obtained were as follows:1. Bright tin deposit consisted of microcrystals with higher orientation. Grain size of the crystals seemed to be 0.5-0.8μ. The states on its cross-section were observed to be fibre structure combined with band structure.Electrodeposited tin always consisted of β-Sn of tetragonal system, and α-Sn of cubic system was not observed even when it was deposited at 5°C.2. The change of surface state by annealing at 150-200°C for 30min. was observed with microscope. It was partly changed to amorphous state when observed with X-ray. However, no change of surface state and crystal structure by annealing was seen in non-bright deposits. Transition point of 161°C between β-Sn and γ-Sn was not analyzed by the above methods.3. The remarkable change by annealing would be caused by internal stress. It is assumed that stress and grain size after annealing were larger, by which recrystallization was promoted. On the other hand, very little effects of annealing were given on non-bright deposits owing to their rough structure and small stress.

Some characteristics of oxidation reactions of organic compounds on platinum electrodes

The anodic oxidation of various organic substances on a rotating smooth platinum electrode has been studied using potentiostatic and galvanostatic methods. The characteristic shape of the potentiostatic polarization curves and the kinetic inhibition of the oxidation processes have been shown to result from the change in the electrode surface state due to oxygen adsorption. At moderate concentrations, the reaction order with respect to the oxidant is usually fractional, while at high bulk concentrations, the rate becomes independent of the concentration. A hypothesis has been advanced that at all potentials it is the molecules adsorbed on the inhomogenous platinum electrode surface which are oxidized. The kinetic equations and the mechanism of the process of electrochemical oxidation have been considered.

On the Change of Surface States of Germanium by Irradiation

The change in electronic behavior of the Germanium surface caused by γ-ray or electron irradiation has been studied. This change is observed by picturing the field effect patterns of the surface recombination velocity, i, e., S∼E patterns, on the cathod ray oscilloscope. As the result of this experiment, the surface electric charge gradually increases negatively as irradiation progresses. After the irradiation, a complex structure appears in S∼E curves. It is assumed by analyzing these curves that either a new surface level appears or level density increases as a result of the irradiation.