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Notes: Interface states in the Si band gap present at oxide/Si(100) interfaces for ∼3-nm-thick Pt/2.1∼3.6-nm-thick silicon oxide/n-Si(100) metal–oxide–semiconductor devices are investigated by measurements of x-ray photoelectron spectra under biases between the Pt layer and the Si substrate, and their energy distribution is obtained by analyzing the amount of the energy shift of the substrate Si 2p3/2 peak measured as a function of the bias voltage. All the interface states observed using this new technique have discrete energy levels, showing that they are due to defect states. For the oxide layer formed in H2SO4+H2O2, the interface states have three density maxima at ∼0.3, ∼0.5, and ∼0.7 eV above the valence-band maximum (VBM). For the oxide layer produced in HNO3, two density maxima appear at ∼0.3 and ∼0.7 eV above the VBM. The energy distribution for the oxide layer grown in HCl+H2O2 has one peak at ∼0.5 eV. The 0.5 eV interface state is attributed to the isolated Si dangling bond defect. The 0.3 and 0.7 eV interface states are, respectively, due to Si dangling bonds with which Si and oxygen atoms in the silicon oxide layer interact weakly. The oxide layer formed in HCl+H2O2 has the highest-density interface states. The oxide layer produced in HNO3 has the lowest-density interface states and, thus, the final cleaning using HNO3 is recommended for the device fabrication. © 1996 American Institute of Physics.

Notes: Magnetic domain structures of thick and small area (45×45×5 μm3) Fe-M(Zr or Ta)-N films were observed by a scanning Kerr-effect microscope (SKEM). The important factors in controlling the magnetic domains are the magnetostriction and the uniaxial anisotropy. By changing the N content in bcc Fe and the Ar pressure during sputtering, the saturation magnetostriction constant λs and the anisotropy field Hk were controlled in the range of 3×10−6–6×10−6 and 10–130 A/m, respectively. Clear and consecutive changes in the domain structures were observed by varying the film's λs, Hk, and stress σ, and the observed structures agree qualitatively with the structures predicted by theoretical calculations. The wall structure where Bloch-like rotations and the Neel-like rotations are combined was observed by SKEM. The metal in gap heads using different λs and Hk films were fabricated and the output at 20 MHz was measured. A lower Hk is not necessarily better for obtaining a higher output in high-frequency ranges. The head output depends on the film's magnetic domain structure, and the structure can be controlled by changing the λs and Hk. © 1996 American Institute of Physics.

Notes: The mechanism of carrier transport through a thin silicon-oxide layer for 〈spray-deposited indium-tin-oxide (ITO)/silicon-oxide/Si〉 solar cells has been studied by measurements of the dark current density as a function of the thickness of the silicon-oxide layer, together with the observation of transmission electron micrographs. Cross-sectional transmission electron micrography shows that a uniform silicon-oxide layer with the thickness of ∼2 nm is present between ITO and Si when the ITO film is deposited on a flat Si(100) surface at 450 °C. The dark current density under a depletion condition strongly depends on the thickness of the silicon-oxide layer. It is concluded from these results that quantum mechanical tunneling is the dominant mechanism for the charge carrier transport through the silicon-oxide layer. On the other hand, when the ITO film is deposited on a mat-textured Si surface at the same temperature, a nonuniform silicon-oxide layer is formed, with ITO penetrating into the silicon-oxide layer in the top and valley regions of the pyramidal structure. By raising the deposition temperature of the ITO film on the flat Si(100) surface to 500 °C, the silicon-oxide layer becomes also nonuniform. For these diodes with the nonuniform silicon-oxide layer, the carrier transfer probability is less dependent on the thickness of the silicon-oxide layer, leading to the conclusion that minute channels of ITO are present in the silicon-oxide layer and charge carriers transfer through the channels. The photovoltage is decreased by the presence of the minute channels, with its magnitude depending on the density of the channels. The conversion efficiency of the 〈ITO/silicon-oxide/n-Si(100)〉 solar cells is unchanged upon illumination for 1000 h. The good cell stability is attributed to the well-crystallized ITO film which effectively suppresses diffusion of oxygen from the air and to low reactivity of ITO with Si at room temperature. © 1995 American Institute of Physics.

Notes: The performance of 〈indium-tin-oxide (ITO)/silicon oxide/n-Si(100)〉 junction solar cells is improved by immersing Si wafers in a potassium cyanide solution before the ITO deposition. It is found from x-ray photoelectron spectroscopy measurements that about 3% monolayer cyanide (CN−) ions are present on the Si surface after the cyanide treatment. The temperature dependence of the current–voltage curves shows that the band bending in n-Si is increased by the cyanide treatment. The increase in the band bending is attributed to an upward Si band edge shift caused by the presence of CN− ions at the oxide/Si interface and/or in the oxide layer. Conductance–voltage measurements show that the density of trap states considerably decreases after the cyanide treatment. The conductance decrease is attributed to the passivation of interface states by the adsorption of CN− ions on Si dangling bonds. © 1997 American Institute of Physics.

Notes: Zinc oxide (ZnO)/n-Si junction solar cells were fabricated by a spray-pyrolysis method and high short-circuit photocurrent densities and relatively high photovoltages were obtained by adjusting the conditions of the deposition and the post-deposition heat treatment. Consequently, relatively high conversion efficiencies ranging between 6.9% and 8.5% were obtained. The efficiency of the solar cells with ZnO/n-Si structure decreases slowly with time when they are kept in air in the dark because of the increase in the thickness of the silicon oxide layer between Si and the ZnO film. This degradation can be avoided by forming an indium-tin-oxide (ITO) overlayer on the ZnO film, indicating that the silicon oxide layer grows through the reaction of Si with oxygen diffusing from the atmosphere, not with ZnO. The efficiency of the ZnO/n-Si junction solar cells decreases rapidly with the illumination time. Capacitance-voltage measurements show that this degradation is caused by a decrease in the work function of the ZnO film. The decrease in the work function is caused by desorption of O−2 from the grain boundaries of the ZnO films. When incident light contains no ultraviolet (UV) component, this degradation does not occur, indicating that the desorption is caused by the acceptance of holes generated by UV light. © 1995 American Institute of Physics.

Notes: Measurements of x-ray photoelectron spectra are performed for ∼3-nm-thick Pt/∼3.6-nm-thick silicon oxide/n-Si(100) devices under biases between the Pt layer and the Si substrate. It is observed that the oxide Si 2p peak as well as the substrate peaks is shifted upon applying biases. These shifts are caused by a bias-induced change of the potential drop across the oxide layer due to the change in the amount of the interface state charge. The amount of the shift of the oxide Si 2p peak is well correlated to that of the substrate Si 2p3/2 peak. The energy distribution of the interface states is obtained by analyzing the amount of the shift of the substrate Si 2p3/2 peak measured as a function of the bias voltage. The interface state spectrum has one peak near the midgap, and the peak is attributed to isolated Si dangling bond states. © 1996 American Institute of Physics.

Notes: Viscoelastic solids with high viscosity were experimentally studied with the intention of having them deformed under uniform shear stress. A kind of sandwich method was developed for applying a constant shear stress to a specimen, and its deformation was observed optically using heterodyne interferometry with a sensitivity of 10 nm in displacement measurement. Time-dependent deformation data were analyzed on the basis of a mechanical model of anelasticity plus viscosity. Viscosity in the range of 108–1014 Pa⋅s could be determined at temperatures of 20–200 °C. Through a simulation using the finite element method together with an experiment visualizing the deformation, the specimen deformation was shown to be of an almost uniform shear mode. Experiments were performed to determine the temperature dependence of viscosity for several kinds of glasses near their glass transition Tg, and the determined viscosity values were about 107 Pa⋅s at Tg. The viscosity values measured by a rotation disk viscometer were in good agreement with the present data. The viscosity of some glasses was also measured by the beam bending and penetration methods, and values of 109–1012 Pa⋅s at Tg were obtained. The large discrepancy between the two kinds of data was considered. © 1996 American Institute of Physics.

Notes: The mechanism of the formation of hydrogen-induced interface states at the Si/silicon oxide interface for metal–oxide–semiconductor tunneling diodes has been investigated by conductance measurements as well as current–voltage measurements. It is found that the diffusing species through the silicon oxide layer to form the interface states is protons, not hydrogen atoms. A conductance peak due to the interface states is present at the reverse bias voltage of −0.3 V. The density of the interface states increases nearly exponentially with time t after the introduction of hydrogen in the air. The time constant of the interface state density versus time curve increases with the hydrogen concentration, in contrast to usual chemical reactions in which the reaction time constant decreases with an increase in the concentration of reactants. This unusual result can be explained by the mechanism that the interfacial reaction sites located adjacent to the interface states react with protons more easily than the other sites, resulting in the formation of two-dimensional aggregations of the interface states. The bias voltage at the constant forward current density is shifted slowly only when a forward bias is applied throughout the measurements, while such a shift does not occur when a reverse bias voltage is applied during the intervals of the current–voltage measurements. The density of the interface states is high in the presence of hydrogen in the air, but the density decreases markedly after evacuating hydrogen-containing air, indicating that the interface states equilibrate with hydrogen in the air. © 1995 American Institute of Physics.

Notes: The face is composed of complicated anatomical components, presenting unique portions, such as the eyes, nose and mouth in a relatively narrow area. Moreover, the facial skin is densely populated by the pilosebaceous units and sweat glands, and its stratum corneum (SC) is much thinner than that of the trunk and limbs, although it is always exposed to the environment. Among various portions of the facial skin, some are more easily irritated than others by environmental stimuli, or are more often affected by certain dermatoses. However, the functional aspects of the different portions of the facial skin have not been studied in detail under a strictly controlled environment in sufficiently large numbers of subjects covering different age groups. Thus, we conducted studies in winter with various biophysical techniques, such as transepidermal water loss (TEWL), as a parameter for SC barrier function, high-frequency conductance as that for skin surface hydration state, skin surface lipids, pH, blood flow and skin surface temperature on the forehead, mid-portion of the cheek (cheek in short), nasal tip (nose in short), nasolabial fold and chin of 20 healthy Japanese females aged 22–37 years (average 25 years) in a climate chamber adjusted to 21 °C and 50% relative humidity. Thereafter, we studied the influence of ageing on these biophysical parameters by collecting data of TEWL, high-frequency conductance and size of superficial corneocytes on the cheek, nasolabial fold and chin of 303 healthy Japanese female volunteers of different ages. The obtained results showed that the barrier function of the SC was best on the cheek, presenting the lowest TEWL, which was significantly higher on the nasolabial fold and chin than on the cheek. TEWL showed a decrease with age. In contrast, skin hydration state was higher on the nose, but it tended to be lower on the nasolabial fold, showing a mild age-related increase. The corneocytes on the nasolabial fold and chin were smaller than those on the cheek. They revealed a clear increase in size with age. Skin surface lipids were richest on the nose, whereas the superficial pH on the nose was the lowest among the regions tested. The skin temperature was lowest on the cheek than on other areas of the face; although, together with the nose, its blood flow was higher than that of the others. These data indicate great regional differences observable in SC functions on the face. In general, the SC barrier function increases with age, probably because of a decreased epidermal turnover rate as recognized by the increase in corneocyte size. Among the various sites, the skin of the nasolabial fold and chin, whose SC consisted of the smallest corneocytes, showed poorest SC properties in barrier function, suggesting the presence of mild invisible inflammation. It is understandable that this area easily develops not only the complaint of sensitive skin to cosmetics but also dermatitis because of various external agents.