The defect profile induced by F ion implantation (120 keV, 2×1014/cm2) into a Czochralski (Cz)-Si wafer was determined by analysis using a slow positron beam method. It was proved that vacancies were present at ppm concentrations at depths exceeding 1.5μm, far beyond the depth to which F ions were implanted. The induced defects consisted of at least two components which could be correlated with their depth.: Annealing at 300°C extinguished the defects only in the deeper region and annealing at 600°C extinguished those in the ion implanted region. It was, further, confirmed that the use of an improved Monte-Carlo-deduced positron implantation profile was better than that of the Gaussian derivative one in calculating defect profiles.
X-ray absorption near edge structure (XANES) has been applied to the elucidation of electronic structures in conduction-band region of SiOx and SiNx produced by ion implantation in Si (100). The XANES spectra of SiOx at the Si2p edge are similar to those of SiO2 but the spectral structure of intermidiate compound such as SiO is not observed. This fact suggests that the SiOx layer consists of a mixture of Si and SiO2 islands, and the conduction band of SiOx is mainly composed of the orbitals of SiO2. On the other hand, the XANES spectra at the Si2p edge of SiNx gradually change depending on the x-values, and a sharp resonance corresponding to the N-dangling appears at the N1s edge for x>1.0. These observations suggest that SiNx phase prefer randombonding structure rather than a mixture of Si and Si3N4 islands.
An octadecanol monolayer on water was investigated with regard to surface pressure relaxation and area creep at 283 K. Under surface pressure less than 20 mN/m, the relaxation and creep completed within a few ten minutes and the monolayer showed a homogeneous morphology. The monolayer under higher surface pressure continued to relax. FT-IR spectra of monolayer films indicated that an absorption band of the CH2 asymmetric stretching mode shifted to low energy with increasing the surface pressure. Molecules in the monolayers after pressure relaxation and area creep preferred to gauche-and trans-configuration, respectively. The compression and dilatation of the monolayer gave rise to a hysteresis curve in the surface pressure(II)-area(A) relationship and the dynamic viscosity measured by canal method was 2∼3×10-6 Pa. s. m. These could be related with the gauche-traps transformation. The collapses of the monolayer were found at high surface pressure. Homogeneous octadecanol monolayers could be formed after creep at about 20 mN/m.
α-Al2O3 having a high specific surface area of 72m2/g was first prepared by the thermal decomposition of diaspore at 530°C. However, its catalytic activity for isomerization of 1-butene was not recognized at all. On the contrary, γ-Al2O3 showed a conversion rate of ca. 70% despite its lower specific surface area of 55 m2/g compared with that of α-Al2O3. These findings indicate that the difference in the catalytic activity between γ-and α-Al2O3 is attributable not to the specific surface area, but to the coordination number of Al ions. Thus it was proved experimentally for the first time that octahedral Al sites in alumina are inactive for isomerization of 1-butene. A quantum-chemical study using an ab-initio MO method on the surface structure and electronic states of γ-Al2O3 explained satisfactorily the lower activity of octahedral Al sites compared with tetrahedral ones.
We have applied secondary ion mass spectroscopy (SIMS) to the detection of chemical species on outer-most surfaces of polymers. Copper deposited in vacuo on polyvinylalcohol (PVA), polyethyleneterephtalate (PET) and nylon 6, 6' was found, by XPS, to react with the functional groups of the polymers to form Cu-0 (PET), Cu-N (Nylon 6, 6') etc. In static-SIMS spectra of copper-deposited polymers, metallized cluster ions, assigned to [Cu-OC]+, [Cu-OCO]+, [Cu-N]+, were detected. Structures of these cluster ions were dependent on the chemical species, and thus it is suggested that the functional groups of interest could be distinguished from other species on the same surfaces by using this technique.
Thin films of SrCuO2 with a tetragonal structure have been synthesized by molecular beam epitaxy. Two different patterns have been observed by reflection high-energy electron diffraction (RHEED) during the alternating supply of strontium and copper under the flow of NO2. Incommensurate streaks appear during the copper supply. The intensity of the incommensurate streak decreases to zero with the strontium supply. We demonstrate that an exact control of the elemental composition of Sr and Cu can be carried out using in-situ intensity monitoring of the incommensurate streak.
Radioluminography is a new type autoradiography, in which a radioactivity distribution pattern is recorded in a photo-stimurable phosphor layer of an imaging plate, then converted, on a reading unit, to digitalized image data storable in a disk, and finally visualized and quantitatively analyzed by using an analyzing unit. This method was applied to the evaluations of 59Fe and 64Cu adsorption on Si wafer surface and of SC-1 (NH4OH : H2O2 : H2O=1 vol : 1 vol : 5 vol) cleaning efficiency against these adsorbed impurities. The distributions of the adsorbed radioisotopes before and after the cleaning were manifested to be understood at a glance. It was found that radioisotope density in any area at any position on the wafer could be determined with the detection limit of the order of 108 atoms/cm2 and the dynamic range over the order of 104.
In order to improve the sensitivity to NO in air, WO3 based sensor elements were loaded with a small amount (0.004 wt%) of noble metals. Among the various noble metals added, Au and Ru were found to be effective promoters. The addition of Au enhanced the sensitivity to 200 ppm NO in air by about one order of magnitude, making the Au-loaded element attached with Pt electrodes the most sensitive to NO in the temperature range (200∼500°C). Ru-WO3 element also exhibited high NO sensitivity at 250 and 300°C, but the promoting effect of Ru quickly decreased as temperature increased. Such promoting effects were hardly consistent with the catalytic activity of the noble metals for the oxidation of NO to NO2, which were in the order Pt>Ru>Au=0. TPD experiments provided evidence supporting that the enhancement of the oxidative adsorption of NO as NO2 would be a major reason for the promoting effects of Au and Ru.
Real-time Raman scattering measurements are performed during and after 3keV-He+ irradiation at sample temperature from room temperature to 573 K. The time dependence of relative intensity of the disorder-induced peak with respect to the original Raman active E2g2 mode peak shows that thermal relaxation of defects created by irradiation. Fast and slow processes exist in the thermal relaxation, the corresponding activation energies being 0.89±0.10 eV and 1.8±0.3 eV respectively.