摘要:

Many synchrotron radiation techniques developed in the past decade use the photoemission process to study surfaces and, in particular, adsorbates. Most of these probe the local surface electronic states. Recently, some photo− emission techniques have evolved into probes of the surface atomic structure as well. These structure−sensitive techniques are photon−polarization− dependent photoemission, adsorbate band structure mapping, surface−EXAFS, and photoelectron diffraction. In this article synchrotron experiments in both categories are discussed, and representative results are given which illus− trate their applications to surface structural problems of fundamemtal interest. We discuss in particular the distinctive advantages of these new surface− sensitive structural probes with respect to other more established techniques.

ISSN:0022-5355    

DOI:10.1116/1.570516

出版商:American Vacuum Society    

年代:1980

数据来源: AIP

摘要:

The adsorption of acetic acid and of propanoic acid on Ag(111) and Pt(111) single crystal surfaces has been studied with LEED. Both acetic acid and propanoic acid formed two‐dimensional structures in two different types of orientation on Ag(111) and propanoic acid apparently formed the same structure on graphite covered Pt(111). Neither acid formed ordered monolayers when adsorbed on clean Pt(111). The similar LEED data and physical properties of the acid molecules suggested similar structures for both acids consisting of closely packed arrays of hydrogen‐bonded dimers.

ISSN:0022-5355    

DOI:10.1116/1.570517

出版商:American Vacuum Society    

年代:1980

数据来源: AIP

摘要:

The SiL2,3VVAuger electron spectrum, produced by electron bombardment, was recorded after progressive Ar+ion bombardments of an initially perfect Si(111) surface. Ion currents of about 1–10 μA at 3 keV were employed. Changes in the shape of the spectrum are observed which can be related to structural changes of the surface, as detected by low energy electron diffraction (LEED). At low ion doses (∠1015–1016cm−2) the main effect is removal of intensity in spectral ranges with origin in the ordered Si(111) 7×7 surface structure. Larger doses (∠1017cm−2) produce a markedly altered Auger spectrum.

ISSN:0022-5355    

DOI:10.1116/1.570518

出版商:American Vacuum Society    

年代:1980

数据来源: AIP

摘要:

Step coverage profile dependences of rf‐diode‐sputtered SiO2films on deposition parameters have been examined by SEM observations. The obtained results are summarized as follows: (1) With decreased spacing between substrate and target, slope of step coverage changes from negative to positive through vertical. (2) Decreasing argon pressure improves step coverage, resulting in a positive slope. (3) Negative dc voltage application to substrate holder makes step coverage negative. On the other hand, step coverage is improved at positive dc voltage. (4) Putting shield ring on substrates, smooth and positive slopes are obtained. The obtained results are successfully explained by shadowing effect of incidence SiO2materials by substrate step.

ISSN:0022-5355    

DOI:10.1116/1.570519

出版商:American Vacuum Society    

年代:1980

数据来源: AIP

摘要:

Plasma reactive sputter etching, sputter etching using Freon (CF4, C2F6, etc.) instead of argon as the etching gas, has been investigated. It has been found that there exists an etching reaction caused by energetic ions (CFn+etc.) different from reactions found in conventional methods. Selective etching of SiO2and Si3N4on Si has been realized by enhancing the etching reaction with the effects of etching table materials (Teflon, carbon) and mixing gas (C2H4, CH4, etc.). Pattern transfer from mask to underlying substance, at least in selective SiO2etching, can be performed uniformly without undercutting and with almost no lateral shift of pattern edges, with higher accuracy than in conventional plasma and sputter etching.

ISSN:0022-5355    

DOI:10.1116/1.570520

出版商:American Vacuum Society    

年代:1980

数据来源: AIP

摘要:

Low energy ion bombardment of a growing film during vapor phase deposition has been shown to be useful in providing additional control over elemental sticking probabilities. In such a deposition mode, the probability of a given atom being incorporated into the lattice of the growing film is given by σ=φ(1−Γ) where φ is the thermal sticking probability and Γ is the elemental sputtering probability. For low energy (<300 eV) ion bombardment of growing III–V compound films, such as GaSb and InSb, ΓIII=ΓVfrom the compound phase with no evidence of preferential sputtering. However, under deposition conditions leading to the growth of two phase films, such as Sb to group III flux ratios much greater than or less than unity, bombardment by ions with greater than the threshold sputtering energy always resulted in the preferential removal of the excess species. Thus for the entire range in growth temperatures (50°–500°C) and V/III flux ratios (<1 to ≳10) used in these experiments, stoichiometric films could always be obtained by adjusting the ion bombardment conditions. Temperature dependent Hall measurements were used to determine Sb vacancy concentrations as low as 1016cm−3in single‐crystal GaSb films grown on (100) GaAs. Finally, ion bombardment during film growth was used to simultaneously alter elemental incorporation probabilities and maintain film stoichiometry in order to grow metastable InSb1−x. pseudobinary alloys with InBi solubilities more than four times larger than the equilibrium value.

ISSN:0022-5355    

DOI:10.1116/1.570521

出版商:American Vacuum Society    

年代:1980

数据来源: AIP

摘要:

We have studied the effect of lattice mismatch on the electron mobilities of InAs films grown on GaAs by MBE. The electron mobilities decrease rapidly with decreasing film thickness in the range of 0.2–2 μm. This is attributed to the high density of dislocations observed in the thinner films. Using a step‐grading growth technique, the dislocation density is reduced with a simultaneous improvement in mobilities.

ISSN:0022-5355    

DOI:10.1116/1.570522

出版商:American Vacuum Society    

年代:1980

数据来源: AIP

摘要:

Desorption properties of Sb on a GaAs(100) surface are investigated by Auger electron spectroscopy (AES). On surfaces covered with an Sb monolayer, two kinds of desorption process were observed with desorption energies of 2.4 and 2.6 eV. The difference in desorption energies is discussed from the viewpoint of elastic strain energy caused by a pseudomorphic structure of Sb.

ISSN:0022-5355    

DOI:10.1116/1.570523

出版商:American Vacuum Society    

年代:1980

数据来源: AIP

摘要:

Evidence is presented that a conducting band is present in the anodic oxide of GaAs that lies about 1.0±0.3 eV below the GaAs conduction band. The energy of the level is determined by a new electrochemical technique that in a sense is the reverse of normal electrochemical voltammetric techniques. In normal voltammetry, an unknown energy level of an ion in solution is determined knowing the energy of the source of electrons, but in our new technique, we intentionally add ions of known energy level in the solution and determine, as the unknown, the energy level of the electron source. The energy of the electron source is the conducting band in the anodic oxide. Other evidence that the oxide has a low energy conducting band includes the observation of rectification processes attributable to a Schottky barrier at the interface and the observation that the capacitance calculated from voltage ramp charging curves had values corresponding to the Helmholtz capacitance.

ISSN:0022-5355    

DOI:10.1116/1.570524

出版商:American Vacuum Society    

年代:1980

数据来源: AIP

摘要:

A numerical integration procedure based on theoretical analysis of the crater geometry removes the edge effects from depth profiles obtained by sputtering with a static and nonuniform ion beam. Parameters characterizing the beam and the detector ensue from the depth profile of a standard sharp interface, e.g., a SiO2film on silicon. These parameters then correct subsequent depth profiles of unknown interfaces sputtered by the same beam. The advantages of this approach are that noaprioriknowledge of th beam current density distribution is required, and the mathematical treatment lends itself to computerization for on‐line data processing. Examples of the correction performed on experiomental depth profiles obtained by sputter‐induced optical emission and secondary ion mass spectrometry techniques illustrate its general applicability.

ISSN:0022-5355    

DOI:10.1116/1.570525

出版商:American Vacuum Society    

年代:1980

数据来源: AIP