摘要:

In many integrated circuit fabrication steps, it is important to be able to ensure that there is no native oxide on a silicon surface before the next layer is deposited. For example, when tungsten is deposited by chemical vapor deposition (CVD) by silicon/hydrogen reduction of WF6, attack of the silicon surface can be extensive (i.e., wormholes) if there is a native oxide layer.1Similarly, growing epitaxial silicon on a single‐crystal substrate at a low temperature also depends critically on the removal of such a native oxide. The standard procedure for attempting to remove any surface oxide involves various wet etches, generally concluding with a dip in dilute HF. However, exposing a clean wafer to the atmosphere for even a short time allows some oxide to regrow, since silicon is an extremely reactive material. Accordingly, it would be desireable to develop aninsituprocedure for cleaning of native oxide, and that will be the subject of this brief note.

ISSN:1071-1023    

DOI:10.1116/1.584991

出版商:American Vacuum Society    

年代:1990

数据来源: AIP

ISSN:1071-1023    

DOI:10.1116/1.584992

出版商:American Vacuum Society    

年代:1990

数据来源: AIP

摘要:

The adsorption of Bi and Sb on clean cleaved InP(110) surfaces has been studied with soft x‐ray photoemission spectroscopy at the BESSY synchrotron radiation source in Berlin. Bi and Sb were deposited onto ultrahigh vacuum cleaved InP(110) surfaces at substrate temperatures of 300 K [room temperature (RT)] and 120 K [low temperature (LT)]. In this paper we focus on the evolution of the overlayer emission intensities as a function of coverage. Spectra of the Bi 5dand Sb 4dcore level emission lines were taken from the submonolayer regime up to coverages of approximately 60 and 20 monolayers (ML) of Bi and Sb, respectively. The spectra were then deconvoluted using a core level fitting routine. In all cases, good agreement between the experimental and fitted curves was achieved by introducing two chemically shifted components of the Bi 5dand Sb 4dcore level emission which are interpreted in terms of Bi(Sb)–substrate and Bi(Sb)–Bi(Sb) bonds. However, for RT deposition, the evolution of the Bi 5dand Sb 4dspectra is significantly different in the coverage range below 2 ML. In the Bi case the adatom–substrate component grows first, and only after about 0.5 ML is the Bi–Bi component observed. The two components have equal intensity at about 2 ML. In contrast, the two components in the Sb 4dspectra grow with equal intensity until 1 ML. The spectra for higher coverages for both systems are dominated by the component assigned to adatom–adatom bonds and the overlayer is found to be semimetallic. The LT spectra do not have the easily resolvable features seen in the RT spectra which may indicate that the growth is much more disordered. However, the overlayers at LT are more laminar. In addition, we present the band bending versus coverage behavior for the Bi/p‐InP(110) interface, which is compared to that of Sb/p‐InP(110).

ISSN:1071-1023    

DOI:10.1116/1.584994

出版商:American Vacuum Society    

年代:1990

数据来源: AIP

摘要:

Experiments of the photodissociation of tetramethyltin by synchrotron radiation and the epitaxial atomic layer growth of diamond structured α‐Sn films are reported. We used surface sensitive core and valence band photoemission spectroscopy to study the temperature dependence of the condensation and desorption behavior of tetramethyltin on CdTe(100). A quantitative analysis of the deposition and photodissociation of tetramethyltin including the work function change and the evolution of the substrate Te 4dand overlayer Sn 4dintensities during the overlayer deposition suggests that individual monolayers can be grown by the technique of synchrotron radiation assisted metal organic layer epitaxy. The photofragmentation process does not cause a significant carbon build up in the overlayer film. The photodissociated hydrocarbons seem to recombine and desorb from the surface.

ISSN:1071-1023    

DOI:10.1116/1.584996

出版商:American Vacuum Society    

年代:1990

数据来源: AIP

摘要:

Microscopic distributions of growth rates on GaAs(001) layers next to (111)Aand (111)Bsurfaces were measured in real time during molecular beam epitaxy growth by scanning microprobe reflection high‐energy electron diffraction. The increase in the growth rate on the GaAs(001) surface near the edge of (111)Asurfaces is observed and the decrease in the growth rate on the GaAs(001) surface near the edge of the (111)Bsurfaces is found out. The exponential variation of the growth rate as a function of the distance from the edge, reflects surface diffusion of Ga atoms. The diffusion lengths along the [110] and [1̄10]directions are estimated to be about 1 and 8 μm at 560 °C, respectively.

ISSN:1071-1023    

DOI:10.1116/1.584997

出版商:American Vacuum Society    

年代:1990

数据来源: AIP

摘要:

Low‐energy ion scattering (LEIS) is introduced as a new analytical technique forinsitumolecular‐beam epitaxy (MBE) monitoring. LEIS is highly sensitive to the atomic structure of topmost layers, and offers an idealinsitumonitoring system. We have built a coaxial impact collision LEIS spectrometer, which is combined with a MBE system. Well‐collimated He+ion beams are provided through the ion beam line and scattered by the substrate surface under MBE growth, and detected by a time‐of‐flight energy analyzer. When the incident direction of the primary beam with respect to the substrate crystal is aligned to a major channeling direction, scattering is limited to the topmost layers, and gives us information on the coverage and epitaxial quality. In order to demonstrate the feasibility of LEIS, we have madeinsituanalysis of MBE growth on InP surfaces. During the layer‐by‐layer growth of InAs/AlAs on As‐stabilized InP(111)A surface, we have observed characteristic variation of the 〈111〉 aligned scattering intensity.

ISSN:1071-1023    

DOI:10.1116/1.584998

出版商:American Vacuum Society    

年代:1990

数据来源: AIP

摘要:

Epitaxial ZnSe/epitaxial GaAs interfaces have been grown using molecular beam epitaxy and evaluated by capacitance–voltage measurements and transmission electron microscopy. The GaAs surface stoichiometry was systematically varied prior to the nucleation of ZnSe. A significant reduction of interface state density occurred when the GaAs epilayer surface was As deficient. The resulting interface state densities of as‐grown structures are comparable to values obtained with (Al,Ga)As/GaAs interfaces.

ISSN:1071-1023    

DOI:10.1116/1.584999

出版商:American Vacuum Society    

年代:1990

数据来源: AIP

摘要:

Synchrotron radiation photoemission spectroscopy is used to study the electronic structure and growth mechanisms of Sn on cleaved GaAs(110) surfaces. Detailed core‐level analysis, along with the substrate intensity attenuation and valence‐band information, indicate that Sn forms nondisruptive bilayer patches on cleaved GaAs(110) surface for coverage θ between 0≤θ≤ 1 monolayer (ML). In the 1<θ<2.5 ML coverage range, the bilayer growth atop the substrate is accompanied by the initial growth of Sn‐based structures on top of the bilayer. The bilayer and Sn‐based structures are semiconducting. The substrate is completely covered at ∼2.5 ML. Continued deposition above 2.5 ML results in Sn clusters. A Sn‐induced density of states progressively fill in the region between the valence‐band maximum (VBM) and the Fermi level (EF) with Sn deposition. At coverages above 3 ML, Sn derived states show emission atEF. The electronic structure changes during the interface development leads to the continuous band bending towards midgap. The total amount of band bending at 8 ML is about 0.67 eV.

ISSN:1071-1023    

DOI:10.1116/1.585000

出版商:American Vacuum Society    

年代:1990

数据来源: AIP

摘要:

We report the successful growth of InAs/Ga1−xInxSb strained‐layer superlattices by molecular‐beam epitaxy. The superlattices are grown on thick, strain‐relaxed InAs or GaSb buffer layers on (100)‐oriented GaAs substrates. A short‐period, heavily strained superlattice at the GaAs interface is found to improve the structural quality of the buffer layer. Arsenic incorporation in nominally pure GaSb layers is found to depend strongly on substrate temperature and As‐background pressure. Best strained‐layer superlattice structural quality is achieved for samples grown at fairly low substrate temperatures (<400 °C). Photoluminescence measurements indicate that the energy gaps of the strained‐layer superlattices are smaller than those of InAs/GaSb superlattices with the same layer thicknesses, in agreement with the theoretical predictions of Smith and Mailhiot [J. Appl. Phys.62, 2545 (1987)]. Far‐infrared photoluminescence is observed from a 37/25 Å, InAs/Ga0.75In0.25Sb superlattice, demonstrating that far‐infrared cutoff wavelengths are compatible with short superlattice periods in this material system.

ISSN:1071-1023    

DOI:10.1116/1.584985

出版商:American Vacuum Society    

年代:1990

数据来源: AIP

摘要:

In low‐energy electron diffraction (LEED), we find two different reconstructions of the technologically important InP(001) surface, the well known (4×2) structure and a high temperature (4×2) structure with streaks at the half order spot positions which is interpreted as a disorderedc(8×2) structure. The corresponding electronic structures were investigated by ultraviolet photoelectron spectroscopy (UPS) and x‐ray photoelectron spectroscopy (XPS). For both types of reconstructions, we observe a surface state emission at the valence‐band maximum and a strong fermi‐level pinning. CaF2was deposited onto these surfaces, and the interface formation was studied by LEED, UPS, and XPS. The overlayer grows epitaxially with (001) orientation of its bulk fluorite structure inspite of the large lattice mismatch of 7.5%. The electronic interface scheme with its valence‐band discontinuity was deduced from photoemission measurements as a function of overlayer coverage. Band bending at the interface results fromp‐type defects.

ISSN:1071-1023    

DOI:10.1116/1.584986

出版商:American Vacuum Society    

年代:1990

数据来源: AIP