摘要:

An atom‐cluster generator which can be set in the specimen chamber of a transmission electron microscope has been designed and constructed. The generator essentially consists of two vacuum chambers; one is the chamber for differential pumping and the other the cluster source chamber. The former plays an essential role in keeping the column of a microscope in a high vacuum. The latter is kept in a gas atmosphere and nm‐sized metal clusters are produced in this chamber by evaporating a metal element from a tungsten filament. With this apparatus, preliminaryinsitudeposition experiments were carried out, and it was observed that isolated gold clusters, ejected from the atom‐cluster generator, landed sequentially on a substrate.

ISSN:1071-1023    

DOI:10.1116/1.587784

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

A flexible polyimide diaphragm was used in place of the usual cantilever for atomic force microscopy. Images of hard disk surface features are presented demonstrating the practicality of the method.

ISSN:1071-1023    

DOI:10.1116/1.587785

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

The valence‐band offset at the zincblende AlN/GaN (110) interface is calculated self‐consistently by means of the linear muffin‐tin orbital method using up to 5+5 layer supercells. The value obtained isEv(GaN)−Ev(AlN)=0.85 eV corresponding to a type I offset. Assuming interface orientation and polytype effects on the valence‐band maximum to be reasonably small, a type I offset can also be expected for wurtzite interfaces. By means of separate calculations, we also test the validity of two simplified approaches, the self‐consistent dipole approximation (SCD) of Lambrecht, Segall and Andersen and the dielectric midgap energy (DME) model of Cardona and Christensen. We find that the SCD results are in very good agreement and the DME results, in fairly good agreement with the fully self‐consistent results. The interface local densities of states show no indication of interface states in the main gap.

ISSN:1071-1023    

DOI:10.1116/1.587786

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

Angle‐resolved photoemission from both (100) and (111) oriented, natural type IIb diamond was used to study the electronic structure of diamond. A negative electron affinity (NEA) was found on the 2×1 reconstructed diamond (100) surface. Photoemission spectra of NEA surfaces exhibit a distinctive peak due to emission from the conduction band edge. This peak was used as a reference point to correlate spectra of (100) and (111) surfaces with a NEA. A feature at ∼7.5 eV above the conduction band edge appears in the spectra of both the (111) and (100) surfaces. Angle‐resolved photoemission measurements were used to determine the energy dispersion of this feature for various off‐normal angles. The results for the surfaces were correlated, and compared to a calculated band structure. Based on this comparison we attribute this feature to emission from secondary electrons which are collected in a conduction band level at ∼7.5 eV above the conduction band edge.

ISSN:1071-1023    

DOI:10.1116/1.587787

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

In this paper we report the implementation of low resistance ohmic contacts top‐type ZnSSe and ZnMgSSe which involves the injection of holes from heavily doped ZnTe into an adjacent alloy layer(s) via graded band gap regions. Temperature‐dependent Hall effect measurements on nitrogen‐doped Zn(S,Se) and (Zn,Mg)(S,Se) were performed and the activation energy of nitrogen acceptors was obtained. With the use of this graded contact, room‐temperature continuous‐wave laser diode operation has been achieved at a threshold voltage of 5.8 V in a ZnCdSe/ZnSSe/ZnMgSSe separate confinement heterostructure.

ISSN:1071-1023    

DOI:10.1116/1.587788

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

Optical second harmonic generation (SHG) is a highly surface‐sensitive probe for studying crystalline Si surfaces because the inversion symmetry is broken and electric dipole optical SHG processes forbidden in the bulk are allowed. The polarized optical SHG from a perfectly oriented Si surface is inherently anisotropic, varying periodically as the in‐surface projection of the polarization vector of the incident laser is rotated about a normal to the surface. The harmonic contributions to the angular anisotropy from the surface are characteristic of the surface bonding, and are modified by misorientation, chemical termination, as well as thermal treatments. This paper reviews the results of our previously reported optical SHG studies on Si(111) wafers with misorientations of 0°–5°±0.5° in the [112̄] direction for Si–H or Si–O terminated surfaces. Azimuthal anisotropy data are compared with an empirical model for the SHG intensity that is based on (i) the nonlinear response of anharmonic oscillators, and (ii) a phenomenological theory of azimuthal anisotropies expected for different surface orientations. This model is used as a framework for estimating ’’effective‘‘ resonance energies from single wavelength experiments, and in particular, for providing insights into the microscopic mechanisms that can contribute to the changes in these resonance energies with respect to different processing conditions. For example, important differences between thermally grown and plasma‐oxidized interfaces are identified, and correlations between SHG and electrical performance of the Si–SiO2interfaces are discussed.

ISSN:1071-1023    

DOI:10.1116/1.587789

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

The H‐termination process on a Si(100) surface and the oxidation‐inhibiting effects were investigated quantitatively by x‐ray photoelectron spectroscopy using synchrotron radiation. The H‐terminated Si(100) surface has two hydrogen‐adsorption components (monohydride and dihydride). This article reports on the oxidation‐inhibiting effects of each phase. The H termination of Si(100) surfaces (flat and tilted by 10°) was performed by supplying H atoms that were generated by the exposure of H2gas to a heated tungsten filament. After that, the surface was exposed to O2gas (1000 L) at room temperature. The magnitude change of two H‐adsorption components in the Si 2pspectra and their peak shifts show a two‐stage hydrogen adsorption process on the Si(100) surface. Oxidation of the monohydride phase (2×1‐H) is reduced to less than 1/3 of that of a clean Si(100) surface, while that of the dihydride phase (1×1‐2H) is reduced to below 1/9. Oxidation occurs more easily for the monohydride phase than for the dihydride phase. Further, the H‐terminated Si(100) surface tilted by 10° was not more oxidized than the flat Si(100) surface. This suggests that atomic steps have little effect on oxidation.

ISSN:1071-1023    

DOI:10.1116/1.587790

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

X‐ray photoelectron spectroscopy (XPS) and Si K‐edge x‐ray absorption near‐edge spectroscopy (XANES) have been used to characterize 0.5–20 nm thick SiO2films on Si(100). In XPS measurements, the chemical shift of the Si(‐O) 2ppeak increases with oxide thickness. However, by neutralizing the surface with low‐energy electrons, and using the C 1sas a reference, a chemical shift of 3.9±0.1 eV is found for neutralized oxide films, and the energy difference between the O 1sand Si(‐O) 2pis independent of oxide thickness. XANES measurements confirm an invariant chemical shift with oxide thickness, the SiKedge from SiO2being 1845.50±0.05 eV for all samples. XPS and XANES data then clearly show that any change in chemical shift of the Si(‐O) 2pwith oxide thickness is mainly due to a surface charging rather than microscopic strain induced by the molar volume mismatch between the oxide and the substrate, as has been previously believed.  

ISSN:1071-1023    

DOI:10.1116/1.587791

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

Device‐quality thin silicon oxynitride films were successfully prepared by combining remote plasma‐enhanced chemical‐vapor deposition and rapid thermal annealing techniques. The physical, chemical, and electrical properties of the films are determined by the relative flow rates of the N‐atom and O‐atom source gases, NH3and N2O, respectively. Analysis of metal–insulator–semiconductor devices indicated the fixed charges in the dielectric (Qf) and the interface defect state densities (Dit), as determined from the analysis of conventional capacitance–voltage (C–V) measurements, were significantly reduced following post‐deposition rapid thermal annealing. The approximate compositions of the films were obtained by on‐line Auger electron spectroscopy, and the local bonding arrangements were determined by Fourier transform infrared spectroscopy. Correlations between the local bonding structures in the oxynitride films and the electrically active defective states at the Si–SiOyNzinterface are also discussed.

ISSN:1071-1023    

DOI:10.1116/1.587792

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

The relation between the structural quality of Si:O layers grown by chemical‐vapor deposition at low temperatures (700–750 °C) and electrical properties was determined. Transmission electron microscopy (TEM), secondary‐ion‐mass spectroscopy, and resistivity measurements were used for this study. An oxygen concentration in these layers was in the range of 6×10−19–6×10−20cm−3. TEM studies have shown that amorphous SiOxprecipitates were formed at the lower interface (between the Si buffer and Si:O layer) when silane was used for the layer growth. Slightly smaller precipitates were distributed through the entire layer. In the layers with higher oxygen concentration, high density of stacking faults originated at the same interface and propagated through the entire layer. The Si capping layer grown on top of Si:O was monocrystalline with the density of stacking faults two orders of magnitude lower than in the Si:O layer. For the lower oxygen concentration the stacking faults were not formed and the size of precipitates at the lower interface and in the layer was much smaller. The resistivity of ∼105and ∼106Ω cm was measured in the layers with lower and higher oxygen content, respectively. Only for the Si:O layers grown in the same range of temperatures (700 °C) using dichlorosilane oxygen induced stacking faults were formed at the upper interface (between Si:O and the capping layer). Some small precipitates were formed at the lower interface but no visible precipitates were present in the Si:O layer. These layers were not semi‐insulating. It was concluded that the mechanism to explain semi‐insulating properties might be related to the presence of the SiOxprecipitates or structural defects present in these layers.

ISSN:1071-1023    

DOI:10.1116/1.587793

出版商:American Vacuum Society    

年代:1994

数据来源: AIP