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Notes: The spectral and the time dependent piezoelectric photoacoustic (PPA) measurements under the continuous light illumination were carried out at 85 K to investigate nonradiative recombination processes involving EL2 defect levels in carbon concentration controlled and not intentionally doped semi-insulating (SI) GaAs. The decrease of the PPA signal due to the photoquenching effect of EL2 is observed for a short period of illumination in the photon energy region from 1.0 to 1.3 eV. Since almost all of the carbon acceptors are compensated by deep donor EL2 in SI GaAs, electron occupancy of EL2 level can be controlled by changing the carbon acceptor concentration. It is found that the photoquenching becomes drastic with increasing the carbon concentration. After fully photoquenching, the PPA signal increases again through a local minimum by the continuous light illumination and finally exceeds the initial value before illumination until the saturation level is reached. The deep donor level EL6 and its metastable state are proposed. EL6 level donates electrons to compensate a part of carbon acceptors after EL20 to EL2* transition is accomplished. The nonradiative recombination through this level generates the PPA signal. Since the PPA measurement can detect lower concentration of EL6 than that of EL2, the higher sensitivity of the PPA measurements than the optical absorption measurements is pointed out. The usefulness of the PPA technique for studying the nonradiative transition through deep levels in semiconductors is also suggested. © 1997 American Institute of Physics.

Notes: After illuminating a single crystal of yttrium iron garnet grown by a modified floating zone method at 77 K, the complex permeability was measured from 77 to 300 K under low alternating field. As well as the decreasing of permeability and the appearance of a peak in μ‘-T curve, disaccommodation (DA) or the change of permeability with time was found to be induced around 140 and 210 K. As the result of the superposition of disaccommodation, the peak in the μ‘-T curve is observed to be divided. These photoinduced magnetic effects cannot be attributed to a single origin, for only photoinduced DA disappears in the process of warming. The origins are discussed and a model is proposed, taking account of the mobility of oxygen vacancy depending on the charge state and the photoexcited electron.

Notes: A photoinduced decrease in permeability μ' is observed over 90% in a highly pure single crystal of yttrium-iron-garnet (YIG) grown by a floating zone method. Even after the illumination is removed, the influence remains up to 230 K. By annealing under oxygen atmosphere in the preparation stage, the magnitude of the effect is reduced to 40%. On warming after the sample is illuminated by a flash lamp at 77 K, the imaginary part of permeability μ‘ below 10 kHz is found to show the double peaks, activation energies of which are 0.1 and 0.3 eV, respectively. Besides, it has been observed that the dependence of magnitude of each peak on the strength of illumination is different. These features are discussed in terms of one or two electron F-type defects (oxygen vacancy) and photoexcited two levels.

Notes: We have studied the formation of a high-quality SrTiO3 (STO) film on a Si surface which is an appropriate buffer film for fabricating high-Tc superconductor devices on Si by molecular beam epitaxy. The STO films with thicknesses of 1300–6700 Å are grown on a SrO buffer layer with a thickness of 100 Å on Si(001)-2×1 in ∼10−8 Torr. The growth temperatures for the STO films and SrO layer are 500 and 400 °C, respectively. The as-grown STO films are insufficiently oxidized regarding the Ti–O bond which is confirmed by the observation of x-ray photoemission spectroscopy, although in situ reflection high-energy electron diffraction spectroscopy and ex situ x-ray diffraction (XRD) reveal a high-quality crystalline structure. The in situ postannealing for the as-grown STO films is performed at 500–900 °C for 60 min in an oxygen atmosphere of 1×10−6 Torr. The heat treatment promotes the oxidation of STO films and results in a high resistivity of 109–1011 Ω cm and a dielectric constant of 130 at 100 kHz at room temperature. The films consist of large grains with 150–200 nm diameter on the surface in the image of atomic force microscopy. The heat treatment does not prominently affect the crystallinity of STO films in the XRD patterns. © 1999 American Institute of Physics.

Notes: On warming the previously white light illuminated yttrium iron garnet with some deficiency of oxygen with a white light, an imaginary part of permeability μ‘ below 10 kHz has been found to show the triple peaks as a function of temperature, the activation energies of which are 0.095–0.22, 0.50, and 0.81 eV, respectively. Furthermore, the height of each peak depends strongly on the illuminating time of exciting light. These features have been discussed and interpreted based on a modified "two-center'' model.

Notes: Piezoelectric photoacoustic (PA) measurements on liquid-encapsulated-Czochralski-grown n-GaAs were carried out at room temperature. A continuous broad band below 1.35 eV and a peak at 1.383 eV were observed in the PA amplitude spectra. By comparing with the optical-absorption spectra, it is concluded that the broad band is due to the electron transition involving the EL2 deep-lying defect levels. For the observed peak at 1.383 eV, the origin is considered to be dislocation related. The possibility that this peak is an apparent one expected from the proposed models for the PA signal generation is denied.

Notes: Polymerization of C60 clusters epitaxially grown on Si(111)-(7×7) substrates was found to be induced by electron injection from the probe tips of scanning tunneling microscopes (STM) as the sample bias was increased from +4.0 to +5.5 V, exhibiting an evolution behavior characterized by an incubation, a linear growth, and a saturation. The incubation time and the growth rate are dependent greatly on the sample site, which is explained by a model taking into account the pre-existing stress as the driving force of the polymerization and the internal stress built up as a consequence of polymerization producing a stress for backward reactions. © 2000 American Institute of Physics.

Notes: Temporal decay characteristics of dislocation-related luminescence bands (D1–D4) were explored in strain-relieved epitaxial SiGe/Si(100). Close similarity of the decay profiles was observed not only between D1 and D2 bands but also between D3 and D4 bands. The decay transients of the D1 and D2 bands at low temperatures are characterized by long decay times, τ(approximately-greater-than)200 ns, whereas the D3 and D4 bands exhibit even sharper transients with τ〈60 ns. Temperature dependence of "radiative'' lifetimes implies a free-to-bound nature of the D1 and D2 bands, while a bound-to-bound character of the luminescence origins for the D3, D4 bands. © 1996 American Institute of Physics.

Notes: : There have been no reports concerning the efficacy and safety of a 1-week quadruple therapy regimen of omeprazole, amoxycillin, roxithromycin and metronidazole for Helicobacter pylori infections and the impact of primary resistance on the eradication rate.〈section xml:id="abs1-2"〉〈title type="main"〉Methods: One hundred and sixty-nine consecutive patients with peptic ulcer disease as well as gastritis with biopsy-proven H. pylori infection were entered into an open study of omeprazole 20 mg o.m., amoxycillin 500 mg t.d.s., roxithromycin 150 mg b.d., and metronidazole 250 mg t.d.s. Helicobacter pylori status was determined by urease test, histology and culture. Susceptibility to amoxycillin, metronidazole and roxithromycin was determined by the E-test.〈section xml:id="abs1-3"〉〈title type="main"〉Results: H. pylori was eradicated in 155 out of 169 (92%; 95% CI 88–96%) by intention-to-treat analysis, and in 155 out of 163 (95%; 95% CI 92–98%) by per protocol analysis. The prevalence of primary resistance against amoxycillin, roxithromycin and metronidazole was 2 out of 166 (1%), 16 out of 166 (10%) and 27 out of 166 (16%), respectively. H. pylori was eradicated in 25 out of 27 (93%) patients with metronidazole-resistant strains compared with 130 out of 136 (96%) in patients with metronidazole-sensitive strains of H. pylori. It was eradicated in 15 out of 16 (94%) patients with roxithromycin-resistant strains while in 140 out of 147 (95%) patients with roxithromycin-sensitive strains of H. pylori, and in two out of two (100%) patients with amoxycillin-resistant stains compared with 153 out of 161 (95%) in patients with amoxycillin-sensitive strains. H. pylori was eradicated in three out of four (75%) patients with double resistance against metronidazole and roxithromycin compared with 152 out of 159 (96%) patients with sensitive strains to metronidazole and or roxithromycin. None of these differences were statistically significant. Severe side-effects were found in only one out of 169 patients—anaphylaxis due to penicillin.〈section xml:id="abs1-4"〉〈title type="main"〉Conclusions: The 1-week quadruple therapy with omeprazole, amoxycillin, metronidazole and roxithromycin was found to eradicate H. pylori in over 90% of all patients. This regimen was also found to be beneficial for patients with pre-treatment resistant strains to metronidazole, roxithromycin or amoxycillin, and was observed to be safe and well-tolerated.