摘要:

The dependence of the microstructures of the {111} surfaces of diamond crystals synthesized in the H2‐CH4‐O2system on the oxygen‐carbon ratio (O/C) has been studied to elucidate the mechanism of the crystal growth. On the {111} surfaces of diamond crystals synthesized in high O/C (≥0.8, in our synthesized conditions), the two‐dimensional nucleation rate is suppressed and the two‐dimensional crystal growth rate is promoted. The Raman spectrum of the diamond crystals synthesized in high O/C shows that the half width at half maximum and the peak position are equivalent to those of natural diamond crystals.

ISSN:0021-8979    

DOI:10.1063/1.352262

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

For closely spaced, nanolithographically defined lines, a thin wall of resist remains to act as the metal line spacer. When exposed to a developer, and then rinsing solution, closely spaced resist walls may become unstable as a result of two effects: (1) internal stresses due to swelling, and (2) lateral surface forces between adjacent walls. In this article we perform a linear stability analysis of a thin polymer wall under the simultaneous action of internal stresses and lateral surface forces. We calculate a stability boundary, and show that internal stresses are necessary for the formation of deformation patterns of finite wavelength. We find that, for slightly subcritical swelling stresses a small lateral force can induce buckling, while, for slightly subcritical surface tractions large internal stresses are necessary to induce instability. The theoretical predictions are in good agreement with experimental data on poly(methyl‐methacrylate) walls produced by electron beam lithography.

ISSN:0021-8979    

DOI:10.1063/1.352240

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

Cross‐sectional observations of YBa2Cu3Oy/La0.7Ca0.3MnOz/YBa2Cu3Oytrilayered films on MgO (100) substrates were performed using transmission electron microscopy. Each layer grows epitaxially with crystal orientations of YBa2Cu3Oy(100)∥ La0.7Ca0.3MnOz(110) ∥ YBa2Cu3Oy(100)∥ MgO(010). The Mn—O—Mn bond is parallel to the Cu—O—Cu bond. A reactant is absent at the interfaces and the La0.7Ca0.3MnOzlayer is continuous until a thickness of about 7 nm.

ISSN:0021-8979    

DOI:10.1063/1.352241

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

A comparative study of reactively‐ion‐sputtered (RIS) and low pressure chemical‐vapor‐deposited (LPCVD) TiN, and sputter‐deposited TaN thin films as diffusion barriers for Cu has been done using Auger electron spectroscopy, Rutherford backscattering spectrometry, x‐ray diffraction, scanning electron microscopy, and sheet resistance measurements. For the RIS TiN and sputtered TaN diffusion barriers, the integrity of the individual layers was preserved and there was no evidence of interdiffusion for samples annealed up to 500 °C in N2–H2ambient for 1 hour. The LPCVD TiN was stable up to 450 °C for 30 minutes only, after which Cu started to diffuse into the TiN layer. The reasons for the higher thermal stability of RIS TiN compared to LPCVD TiN can be deduced from the microstructural differences in the two films, as observed with x‐ray diffraction technique.

ISSN:0021-8979    

DOI:10.1063/1.352242

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

Following Hooge’s suggestion [F. N. Hooge, Phys. Lett. A29, 139 (1969)] that 1/fnoise follows a simple empirical law involving a parameter &agr;H, with the noise caused by mobility fluctuations, we examine the mobility fluctuations produced by dislocations in semiconductors, viz. produced by carrier trapping levels in a linear array. In the present contribution we analyze the fluctuations of trapped carriers, where the trapping is dominated by the cylindrical space charge regions around the dislocations. The corresponding mobility fluctuations are evaluated in Part IV of the series.

ISSN:0021-8979    

DOI:10.1063/1.352243

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

In part III under this title, fluctuations in electron trapping at semiconductor dislocations are analyzed. In this contribution these fluctuations of trapped charge are related to mobility fluctuations and reasonable agreement is found with the Hooge [F. N. Hooge, Phys. Lett. A29, 139 (1969)] expression for 1/fnoise. The calculated noise power is found to be proportional to the dislocation density and varies inversely with the doping levelNDat highND. We conclude from the analysis that the calculated frequency span of 1/fnoise from dislocations will only be wide if the dislocations are random; for aligned, impurity free dislocations a spectrum similar to generation‐recombination noise will be observed. Such behavior is observed experimentally.

ISSN:0021-8979    

DOI:10.1063/1.352217

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

We report on a systematic study of atomic ordering in InGaAsP and InGaAs grown by atmospheric pressure metalorganic chemical vapor deposition. InGaAsP lattice matched to InP, grown in a temperature range of 625–650 °C, reveals atomic ordering on the (111) plane (variant I) and the (11¯1¯) plane (variant II) of the group III sublattice. The extent of atomic ordering increases with decreasing growth temperature and increasing In to Ga ratio. No orderings are observed in InGaAsP grown at 700 °C or in In0.53Ga0.47As lattice matched to InP at all our growth temperatures, in contrast to the commonly believed occurrence of maximum ordering at 1/1 In to Ga ratio. The facts that these conditions differ significantly from the reported conditions for InGaAsP grown by other techniques strongly suggests that the atomic ordering formation is controlled by the surface kinetics and growth environment, i.e., chemistry at the reactive gas‐solid surface, fluid dynamics of the reactive gases, and growth temperature, rather than the composition and growth temperature. A fine structure observed in the superspots associated with the atomic ordering in the electron diffraction pattern indicates a possible superlattice structure formed by alternating variant I and variant II ordered layers. Misfit strain as well as sulfur dopant are shown to have no effect on the atomic ordering. Zinc dopant, however, totally eliminates the atomic ordering and shifts the energy band gap to a larger band gap.

ISSN:0021-8979    

DOI:10.1063/1.352218

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

The correlation deep level transient spectroscopy (DLTS) method is developed for insulator/semiconductor interface studies. Trap transient modeling indicates that the energy range in which the trap transients can contribute to the DLTS signals of the correlation method is about 12 kT, and is much wider than that of the boxcar method (several kT). Moreover, large voltage pulse for saturation will cause the capacitance transient to shift away from the ideal exponential due to the sum of the various emission rates. Hence, the equations for determination of interface trap density suitable for the boxcar method is invalid for the correlation method. For this reason, an equation for determining the interface trap density suitable for the correlation method is derived. The interface trap density determined by this method agrees well with other methods.  

ISSN:0021-8979    

DOI:10.1063/1.352219

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

Predictions of deep levels associated with N vacancies in AlxGa1−xN as functions of alloy compositionxexplain both (i) the dramatic change from naturallyn‐type to semi‐insulating behavior (forx=xc&bartil;0.5) in terms of a shallow‐deep transition for the vacancy’sT2level, and (ii) the major photoluminescence feature in terms of recombination from the vacancy’sA1deep level. Extrinisic photoluminescence data for Zn‐doped AlxGa1−xN are interpreted in terms of a transition from the conduction band to aT2‐symmetric deep level in the lower part of the gap. This level is associated with antisite Zn on a N site, ZnN.  

ISSN:0021-8979    

DOI:10.1063/1.352220

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

Capacitance‐voltage, deep level transient spectroscopy (DLTS), and admittance spectroscopy measurements have been performed to characterize a GaAs quantum well confined either by Ga0.57Al0.43As layers or by two GaAs‐Ga0.54Al0.46As superlattices. Due to a large capacitance decrease at low temperature, the well response cannot be obtained from DLTS measurements. This capacitance step is related to the thermionic emission from the well to the barrier regions. For the case of the enlarged well in the superlattice, the electron emission takes place towards the conduction miniband. In order to deduce the conduction‐band discontinuity, admittance spectroscopy measurements have been applied. The bottom of the superlattice miniband is at 107±10 meV from the GaAs conduction‐band minimum. The corresponding band offset deduced from a theoretical calculation is &Dgr;Ec=410±10 meV=(0.65±0.02) &Dgr;Eg. For the GaAs quantum well in GaAlAs, we measure a conduction‐band discontinuity of 0.35 eV between GaAs and GaAlAs that has its minimum at theXpoint. At the &Ggr; point, the band offset ratio &Dgr;Ec/&Dgr;Egis once more confirmed.

ISSN:0021-8979    

DOI:10.1063/1.352221

出版商:AIP    

年代:1992

数据来源: AIP