摘要:

The behavior of individual atoms on solids has long been of interest for understanding the physical and chemical properties of surfaces. Now, through the use of the field ion microscope, it is possible to directly image single atoms on metal surfaces and to examine their properties quantitatively. Such studies are reviewed, with special emphasis on: (1) surface structure and its effect on diffusion; (2) the details of the jump process; (3) interactions between atoms leading to cluster formation; and (4) the properties of clusters.

ISSN:0022-5355    

DOI:10.1116/1.570515

出版商:American Vacuum Society    

年代:1980

数据来源: AIP

摘要:

The chemistry of solid–solid interfaces in metals is reviewed in relation to its characterization, theory, and relevance to materials science. The current techniques for measuring interface segregation, AES, STEM with x‐ray analysis, and mass‐resolved field desorption microscopy, are outlined and their advantages discussed. The expression of quantitative measurements from these techniques is unified. The behavior of segregation is discussed for the experimental variables—localization, crystal orientation, chemical system, time, and temperature. The theories to describe segregation in binary and ternary systems are then presented together with the analysis of the kinetics of segregation. The importance of these different aspects arises in a number of segregation sensitive materials properties. These will be described together with remedial procedures that result from the characterizations.

ISSN:0022-5355    

DOI:10.1116/1.570464

出版商:American Vacuum Society    

年代:1980

数据来源: AIP

摘要:

This paper reports a study of grain boundary and free surface segregation in iron alloys. Scanning Auger electron spectroscopy has been used to analyze the extent and spatial distribution of the segregants. It is found that there is a similarity between free surface and grain boundary segregation for vacuum‐melted (vm) and zone‐refined (zr) materials. S and O are the primary segregants to grain boundaries for vm samples, while N is the predominant segregant for zr material. When O and S are the primary segregated elements, a site competition between them is observed on both the free surface and at grain boundaries. On the free surface the site competition is dependent on grain orientation.

ISSN:0022-5355    

DOI:10.1116/1.570406

出版商:American Vacuum Society    

年代:1980

数据来源: AIP

摘要:

The surfaces of four polycrystalline copper samples were examined under UHV conditions by AES: OFHC Cu, 99.99% Cu, 99.9999% Cu, and 0.086 wt. % Ag in OFHC Cu. Surface chemical compositions in the range of 25°–600°C were determined. Sulfur concentrations on the surfaces at various temperatures were also measured as a function of time. In almost all cases the sulfur concentration increased as (time)1/2. This process was interpreted in terms of a model based on diffusion controlled ’’outgassing’’ in which the sulfur segregated to the surface instead of vaporizing. The activation energies for this process for the four samples ranged from 0.18 to 0.31 eV/atom. RHEED data from an OFHC Cu sample indicated that sulfur formed an orthorhombic Cu2S structure on the surface. Around 500°C the Ag–Cu alloy experienced a complex, rapid stage of segregation of sulfur. Above this temperture range the surface sulfur concentration dropped rapidly, reaching zero at 600°C.

ISSN:0022-5355    

DOI:10.1116/1.570418

出版商:American Vacuum Society    

年代:1980

数据来源: AIP

ISSN:0022-5355    

DOI:10.1116/1.570384

出版商:American Vacuum Society    

年代:1980

数据来源: AIP

摘要:

We have observed large matrix effects in the secondary ion emission from alloys when bombarded with an O+2beam. Binary alloys of Ni with Cr, Fe, and Cu were studied. Chromium, which reacted most strongly with oxygen, induced the largest enhancement of the Ni+ionization probability. Iron enhanced the Ni+ionization probability to a lesser extent, whereas copper resulted in a decrease of the Ni+ionization probability. Ni also induced a small enhancement of the ionization probability of Cr. We find a strong correlation of the mean free energy of formation of the metal‐oxide bond with the observed trends in the ionization probabilities. These matrix effects can cause artifacts in the depth profiling of metal film structures where interdiffusion at the interface leads to the formation of alloys or intermetallic compounds. This is indeed observed when interfaces of Ni–Fe and Ni–Cr films are studied by SIMS.

ISSN:0022-5355    

DOI:10.1116/1.570390

出版商:American Vacuum Society    

年代:1980

数据来源: AIP

摘要:

Crater‐edge and conventional depth profiling have been used to characterize epitaxial films of AlxGa1−xAs grown by LPE on GaAs (100) substrates. In order to reduce damage low energy (?500 eV) argon ions were used. From the high energy Auger transitions values ofxwere derived with an accuracy Δx=0.01. Minimum chemical interface widths were observed of 2.5 nm, independent of depth below the surface.

ISSN:0022-5355    

DOI:10.1116/1.570468

出版商:American Vacuum Society    

年代:1980

数据来源: AIP

摘要:

We have used transmission electron microscopy replica techniques in conjunction with Auger sputter profiling (ASP) to study the effect of sputtering on the morphology of SiO2surfaces. 1 keV Ar ions incident 49° from the surface normal induce a ridge and valley structure with the ridges running normal to the ion beam direction. The degree of roughness is proportional to the amount of SiO2removed by sputtering and appears to have no effect on the width of the Si–SiO2interface as seen by ASP.

ISSN:0022-5355    

DOI:10.1116/1.570480

出版商:American Vacuum Society    

年代:1980

数据来源: AIP

ISSN:0022-5355    

DOI:10.1116/1.570488

出版商:American Vacuum Society    

年代:1980

数据来源: AIP

摘要:

The initial oxidation of plutonium metal at 27°C has been studied using AES and XPS. Initially a ’’clean’’ plutonium surface was prepared by prolonged Ar+bombardment followed by 500°C anneal and Ar+bombardment cleaning cycles. Changes occurring in the plutonium Auger electron spectra in the energy range of 40–120 eV and the 4f5/2, 4f7/2(core levels), and valence band XPS peaks were monitored during oxygen exposures of 10 to 1.8×108L. Examination of the 4f7/2level revealed two oxidation states which are attributed to a suboxide an PuO2. The 4f7/2binding energies for the two oxidation states and plutonium metal are 426.1, 424.4, and 422.2 eV, respectively. It was observed that oxidation proceeded in two steps. In the first step there was a rapid reaction of oxygen with the formation of a suboxide. In the second stage, the uptake of oxygen leveled off with conversion of the suboxide to PuO2.

ISSN:0022-5355    

DOI:10.1116/1.570503

出版商:American Vacuum Society    

年代:1980

数据来源: AIP