摘要:

A theoretical model called the ‘‘multibody model’’ is developed for the composition dependence of the activation energy. The model that is based on the diffusion required of the recrystallization for the solid phase epitaxy does not involve any adjustable parameters and is shown to represent experimental data satisfactorily. For the Si1−xGexalloys that are of diamond structure, the most logical choice is the ‘‘five‐body model’’ involving five atoms. The model is equally applicable to any other binary alloy. ©1996 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.363745

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

High‐quality ceramics based heteroepitaxial structures of oxide‐nitride‐semiconductors, i.e., SrTiO3/TiN/Si(100) have been fabricated byinsitupulsed laser deposition. The dependence of substrate temperature and oxygen partial pressure on the crystalline quality of the SrTiO3films on Si with epitaxial TiN template has been examined. We found that epitaxial growth occurs on TiN/Si(100) above 500 °C, initially at a reduced O2pressure (10−6Torr), and followed by a deposition in the range of 5–10×10−4Torr. X‐ray diffraction (&THgr;, &ohgr;, and &Fgr; scans) and transmission electron microscope (TEM) results revealed an excellent alignment of SrTiO3and TiN films on Si(100) with a cube‐on‐cube epitaxy. Rutherford backscattering and ion channeling results show a channeling minimum yield (&khgr;min) of ∼13% for the SrTiO3films. High‐resolution TEM results on the SrTiO3/TiN interface show that the epitaxial SrTiO3film is separated from the TiN by an uniform 80–90 A˚ crystalline interposing layer presumably of TiNxO1−x(oxy‐nitride). The SrTiO3film fabricated at 700 °C showed a high relative dielectric constant of 312 at the frequency of 1 MHz. The electrical resistivity and the breakdown field of the SrTiO3films were more than 5×1012&OHgr; cm and 6×105V cm−1, respectively. An estimated leakage current density measured at an electric field of 5×105V/cm−1was less than 10−7A/cm2. ©1996 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.363798

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

The mechanical properties of (001)‐, (011)‐, and (111)‐oriented MgO wafers and 1‐&mgr;m‐thick TiN overlayers, grown simultaneously by dc magnetron sputter deposition at 700 °C in a mixed N2and Ar discharge, were investigated using nanoindentation. A combination of x‐ray‐diffraction (XRD) pole figures, high‐resolution XRD analyses, and Auger electron spectroscopy was used to show that all TiN films were single crystals with N/Ti ratios of 1.0±0.05. The nanoindentation measurements were carried out using a three‐sided pyramidal Berkovich diamond indentor tip operated at loads ranging from 0.4 to 40 mN. All three orientations of MgO substrates, as‐received, exhibited identical hardness values as determined using the Oliver and Pharr method. After a 1 h anneal at 800 °C, corresponding to the thermal treatment received prior to film growth, the measured hardness of MgO(001) was 9.0±0.3 GPa. All TiN films displayed a completely elastic response at low loads. Measured hardness values, which decreased with increasing loads, increased in the order (011)<(001)<(111). After a 30 s postdeposition anneal at 1000 °C, however, hardness was found to be independent of load except at displacements >100 nm where substrate effects were apparent. TiN(001) and (111) films had hardnesses of 20±0.8 and 21±1 GPa, respectively, while data obtained from (011) layers exhibited large scatter due to surface roughness effects. Young’s moduli for annealed samples, calculated from the elastic unloading curves, were found to be 307±15 GPa for MgO (001) and 445±38 and 449±28 GPa for TiN (001) and TiN (111), respectively. ©1996 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.363799

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Silver, copper, and mixed silver–copper nanocluster‐doped silica thin layers were prepared by the sol‐gel process. Samples were heat treated in different annealing atmospheres (air, argon, or 5%H2–95%N2) in the temperature range 500–1100 °C. Specimens were characterized by optical absorption spectroscopy, Rutherford backscattering spectrometry, x‐ray diffraction, and transmission electron microscopy. Cluster growth and dissolution, as well as migration of metal atoms towards the sample surface, with a subsequent evaporation, were observed to occur at temperatures that depend on the annealing atmosphere. In the mixed silver–copper system, the formation of Ag–Cu phase‐separated clusters was observed. ©1996 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.363800

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Deep electron traps in ZnSe crystals grown by the vertical gradient freezing method using a sealed molybdenum capsule were studied by isothermal capacitance transient spectroscopy. These crystals have electron concentrations of 1015–1017cm−3in the as‐grown state. Besides the deep traps caused by isolated impurities, two characteristic traps were found. One is the most dominant trap in almost all samples studied, with an apparent activation enthalpy of ∼0.3 eV accompanied by an electron capture barrier of 0.05–0.29 eV. The concentration of this trap is less than 3×1015cm−3. By a deconvolution of its highly broadened spectrum, the nontheoretical emission behavior was recognized as an overlapped emission of a number of different traps with similar emission time constants. That probably corresponds to the difference of the impurity species combined with the native defect in this trap. The other trap has an activation enthalpy of 1.03–1.1 eV and the concentrations of electrons captured by the trap are found to depend logarithmically on the duration of the filling pulse. The origin of this trap is assumed to be an impurity atom associated with extended defects such as dislocations. ©1996 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.363801

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Periodic layer‐by‐layer dielectric structures with full three‐dimensional photonic band gaps have been designed and fabricated. In contrast to previous layer‐by‐layer structures the rods in each successive layer are at an angle of 70.5° to each other, achieved by etching both sides of a silicon wafer. Photonic band‐structure calculations are utilized to optimize the photonic band gap by varying the structural geometry. The structure has been fabricated by double etching Si wafers producing millimeter wave photonic band gaps between 300 and 500 GHz, in excellent agreement with band calculations. Overetching this structure produces a multiply connected geometry and increases both the size and frequency of the photonic band gap, in very good agreement with experimental measurements. This new robust double‐etched structure doubles the frequency possible from a single Si wafer, and can be scaled to produced band gaps at higher frequencies. ©1996 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.363802

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

InxGa1−xAs layers (0≤x≤0.37) doped with carbon (>1020cm−3) were grown on semi‐insulating GaAs substrates by chemical beam epitaxy using carbon tetrabromide (CBr4) as the dopant source. Hall measurements imply that all of the carbon was present as CAsfor values ofxup to 0.15. The C acceptors were passivated by exposing samples to a radio frequency hydrogen plasma for periods of up to 6 h. The nearest‐neighbor bonding configurations of CAswere investigated by studying the nondegenerate antisymmetric hydrogen stretch mode (A−1symmetry) and the symmetricXHmode (A+1symmetry) of the H–CAspairs using IR absorption and Raman scattering, respectively. Observed modes at 2635 and 450 cm−1had been assigned to passivated Ga4CAsclusters. New modes at 2550 and 430 cm−1increased in strength with increasing values ofxand are assigned to passivated InGa3CAsclusters. These results were compared withabinitiolocal density functional theory. Modes due to AlInGaCAsclusters were detected in samples containing grown in Al and In. These results demonstrate that for InGaAs, CBr4is an efficient C doping source since both In–CAsbonds as well as Ga–CAsbonds are formed, whereas there is no evidence for the formation of In–CAsbonds in samples doped with C derived from trimethylgallium or solid sources. ©1996 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.363803

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

The conduction‐band effective masses in InxGa1−xAs with a complete range of composition, and InAlGaAs and InGaAsP alloys covering the complete range of lattice matched to InP have been determined by far‐infrared optically detected cyclotron resonance and magnetophotoconductivity measurements. It is found that the measured effective masses as a function of alloy composition are heavier than the values predicted from the five‐bandk⋅ptheory. We show that this discrepancy can be resolved by including the effect of disorder‐induced potential fluctuations that causes the wave function mixing between conduction and valence bands. We find that the strength of the potential fluctuations can be well described in terms of the Phillips electronegativity difference related to chemical disorder. ©1996 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.363804

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

The effects of valence band anisotropy on longitudinal and transverse high‐field differential mobilities, diffusivities, and thermal noise temperatures were theoretically investigated. The effects were examined for holes in silicon and in several hypothetical materials having systematically varied degrees of valence band anisotropy. The results show a pronounced dependence of thetransversehigh‐field differential mobility and of thelongitudinalhigh‐field noise temperature upon the degree of anisotropy. This suggests that thermal noise measurements may provide an alternative to magnetotransport methods as a valence bandstructure measurement technique. The results also imply that thermal noise in semiconductor devices can be mitigated by choosing a semiconductor with a low degree of valence band anisotropy and, for a given semiconductor, by properly aligning the device layout with respect to the material crystallographic axes. ©1996 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.363805

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Silicon–germanium alloys offer a system where the ratio of the electron impact ionization coefficient (&agr;) and hole impact ionization coefficient (&bgr;) varies from a value larger than unity (in high silicon content alloys), to a value smaller than unity (in high germanium content alloys). We report results for &agr; and &bgr; for this alloy system. The electron results are based on a multivalley nonparabolic band structure. The hole results are based on a six‐bandk&sdot;pmodel for low energies coupled to an eight‐band model for high energies. We find that for the alloy Si0.4Ge0.6, &agr;∼&bgr;. Alloy scattering is found to play an important role in determining the impact ionization coefficient. For compositions around Si0.5Ge0.5, the strong alloy scattering is found to suppress the impact ionization coefficient. ©1996 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.363746

出版商:AIP    

年代:1996

数据来源: AIP