摘要:

We present photoluminescence studies onCdSxSe1−xsemiconductor doped glasses with gap energies ranging from about 2 to 3 eV (400–600 nm). The investigations were performed by near-resonance as well as temperature-dependent resonance Raman spectroscopy. On the basis of the strongly resonant behavior of the deep trap photoluminescence with the excitonic states of the nanocrystallites, we have demonstrated that—besides the effect of photodarkening—inconsistencies in the experimental results of semiconductor doped glasses presented in literature, could be due to changes in the electronic resonance conditions when experimental parameters are changed. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.366555

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We report on a study of grazing incidence absorption and reflection spectra of NiO in the region of the Ni2pedge. The aim is to evaluate the distortion of the near edge spectrum by the critical angle behavior of individual components within the spectrum. This can be used to improve the separation of multiplets and enhance low spectral weight line shapes like charge transfer satellites. The measured spectra have been compared with calculations using an optical model. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.366153

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Evidence is presented for the formation ofO2−on a porous silicon surface. TheO2−present on a porous silicon surface may contribute to the infrared spectrum of air oxidized surfaces in the range encompassing∼1100–1150 cm−1.The presence ofO2−suggests its possible role as a precursor for oxygen atom formation. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.366154

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The origin of Li deficiency in films grown by laser ablation of single-crystalLiNbO3targets in a buffer gas has been investigated by analyzing the stoichiometry of the deposited films as a function of the following parameters: the distance target-substrate, the nature of the buffer gas (He,O2, and Ar) and the deposition configuration. The results show that significant Li losses are related to scattering processes during the expansion regime which are higher the higher the mass of the gas species. The results show that the Li content of the films can be enhanced by setting the substrate either at distances larger than the plume length or in a configuration in which the substrate is not facing the target. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.366155

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Wet oxidation of AlGaAs to formAl2O3by the reduction ofH+from water to H produces intermediateAs2O3.Reduction ofAs2O3by H to elemental As enables the escape of arsenic from the oxidized film. Further reduction of As toAsH3can provide another volatile As species. Formation of intermediate As is problematic for the use of wet oxidation in metal-insulator-semiconductor applications. The kinetic balance betweenAs2O3formation and As escape can explain the transition between the linear and parabolic time dependence of the wet oxidation of buried AlGaAs layers. The near-total suppression of wet oxidation byO2is attributed to the suppression of volatile product formation through consumption of atomic hydrogen by reaction withO2to formH2Oin preference to the hydrogen reduction ofAs2O3.©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.366156

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Etching reaction of Si(100) is investigated by usingCl2molecular beams with a hyperthermal translational energy up to 3.0 eV. The reaction rate is clearly enhanced by translational energy, and the threshold energy is 2.1 eV. The translational-energy-induced reaction rates are measured as a function of substrate temperature; the results closely fit Arrhenius plots as the sum of two components having activation energies of 2.7 and 1.2 eV. The higher energy, derived from the fit of the high-temperature region, agrees well with the pure thermal reaction, i.e., low-translational-energy reaction. The lower energy, which is observed here, is determined as the activation energy of the translational-energy-induced reaction. This energy is not affected by the translational energy from the threshold to 3.0 eV, whereas the etch rate increases with translational energy. These findings suggest that the translational energy contributes to the formation of a new chlorinated Si surface from which silicon chloride desorbs thermally with lower activation energy than from a chlorinated Si surface formed by a pure-thermal reaction. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.366157

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A simple electrostatic model of the adsorbate–adsorbate interaction of hydrogen atoms at aPd–SiO2interface is presented. The model predicts a hydrogen adsorption isotherm of the Temkin type. It is found that, in practice, an upper limit for the hydrogen response of a Pd-metal-oxide-semiconductor device exists. The value (in V) is equal to the difference of the initial heats of adsorption (in eV) of the interface and the Pd bulk, respectively. Furthermore, a corresponding maximum hydrogen concentration, at the interface, of1×1018 m−2is predicted. The predictions are in good agreement with previously observed experimental data. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.366158

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Polymer electrochemical cells with ion blocking electrodes were reported to emit light under applied voltage. This work analyzes the current-voltage relations, internal electric fields, and point defect distribution in the polymer. The polymer is regarded as a mixed-ionic-electronic conductor. Two relevant defect models are investigated. A good fit is obtained between experimental data and theory which also takes into consideration electrode overpotentials. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.366159

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The complete sets of elastic constants of 4H and 6H silicon carbide single crystals were determined by Brillouin scattering. The elastic constants of 6H SiC areC11=501±4,C33=553±4,C44=163±4,C12=111±5,andC13=52±9 GPa;the corresponding ones of 4H SiC are the same within experimental uncertainties. The compressibility,4.5×10−3 GPa,is about 3–5 times smaller than those reported for polycrystalline SiC materials. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.366100

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We present a systematic study of excitonic and impurity states in semiconducting quantum wells within a fractional-dimensional space approach, in which the Schro¨dinger equation is solved in a noninteger-dimensional space where the interactions are assumed to occur in an isotropic effective environment. In this scheme, the fundamental quantity is the parameterDwhich defines the fractional dimension associated to the effective medium, and to the degree of anisotropy of the interactions. A direct procedure for determining the fractional dimensionality of the isotropic effective space is proposed in which one may obtain a reliable solution for the energies of the actual physical system under consideration. Explicit calculations of the fractional-dimensionalDparameter are made in the case of excitons and impurities in infinite-barrier quantum wells, with exciton and impurity binding energies found in excellent agreement with previous variational results. Calculations are also performed for exciton binding energies in finite-barrier quantum wells with good agreement with recent experimental results. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.366267

出版商:AIP    

年代:1997

数据来源: AIP