摘要:

LEED intensity measurements and dynamical calculations have been performed for the nonreconstructed Ir(100) surface. They were compared with each other using the Zanazzi–Jonarfactor for different energy ranges of the spectra, i.e., 100–250, 250–500, and 100–500 eV. It turns out that the surface relaxation is always nearly the same, at least within the error of the fit, Δd/d=−2%±2%. However, it appears that therfactors are definitely lower for the high energy region accompanied by a slight increase of the precision with which Δd/dcan be extracted. The Zanazzi–Jonarfactor of the total energy range cannot be interpreted as a linearly weighted average of those of the subranges.

ISSN:0734-2101    

DOI:10.1116/1.572171

出版商:American Vacuum Society    

年代:1983

数据来源: AIP

摘要:

A fracture stage is designed to permit slow strain‐rate tensile fracture of metallic samples inside the Auger vacuum chamber. The fracture stage consists of two crossheads, one fixed and one moveable. A small electric motor drives the moveable crosshead to separate from the fixed crosshead at a constant rate down to 7×10−4cm/s. Samples remain attached to the sample carousel stage during loading and following fracture, they can be quickly translated and rotated into alignment with the Auger analyzer. Tests on hydrogen charged Inconel 600 result in fracture times of 2–3 min and fracture strains of 4%–6% yielding a fracture surface that is in excess of 75% intergranular. This technique is recommended for grain boundary analysis of ductile austenitic alloys.

ISSN:0734-2101    

DOI:10.1116/1.572172

出版商:American Vacuum Society    

年代:1983

数据来源: AIP

摘要:

The composition of oxide films, formed on stagnant, molten soft solder has been studied. The influence of oxidation time and of solder composition on the oxide films was measured. On clean soft solder SnPb60‐40 a complex oxide film was formed, consisting of a thin outer layer of SnO2, a layer of SnO mixed with metallic lead, and a transition layer to the underlying solder metal. The same type of oxide layer was formed on solder with copper or with nickel. On soft solder contaminated with aluminium, zinc, or phosphorus the contaminants were preferentially oxidized, resulting in an aluminium oxide film, a zinc oxide film, and a mixed phosphorus oxide–tin oxide film, respectively.

ISSN:0734-2101    

DOI:10.1116/1.572173

出版商:American Vacuum Society    

年代:1983

数据来源: AIP

摘要:

The surface topography of the thermal oxides on InP are shown to blister for growth temperatures somewhat above 600 °C. It appears that the oxide softens sufficiently to allow the trapped phosphorus at the interface to expand, thus causing the surface bubbles to form. The size of the bubbles varies considerably across a wafer and they tend to increase in size with temperature. At 780 °C one bubble had a radius of ≊100 μ. AtT≲650 °C the elemental phosphorus at the interface is the source of the P and the underlying substrate remains smooth. Above this temperature the InP substrate provides the P as shown by the pits in the substrate. There appears to be a relationship between the surface roughening and a change in oxide layer composition.

ISSN:0734-2101    

DOI:10.1116/1.572174

出版商:American Vacuum Society    

年代:1983

数据来源: AIP

摘要:

The stability of a Ge(111) surface and its vicinals were studied by LEED for clean and Ag covered conditions. Before deposition the surfaces were macroscopically smooth. After deposition of only a few tenths of a monolayer of Ag and heating to 400 °C, the surface consisted of narrow (544) facet planes and wide (111) terraces. At coverage above 0.7 the (544) facets disappeared and (211) facets started growing. The facets had dimensions in the range of 10 μ, so that they could be observed with an optical microscope. Furthermore, a rotation of ledges into directions with low indices was observed. The results show that the equilibrium shape of a surface is drastically changed by a coverage of a fraction of a monolayer due to the formation of new minima of the surface free energy at peculiar high index vicinal surfaces.

ISSN:0734-2101    

DOI:10.1116/1.572176

出版商:American Vacuum Society    

年代:1983

数据来源: AIP

摘要:

Carbon monoxide adsorption was studied on the Pd(111) surface with submonolayer carbon coverages. It is shown that the carbon monoxide desportion spectrum can be used in the detection of a carbon coverage much below the detectability level of AES. Although the estimation of the absolute carbon coverage is subjected to quite a bit uncertainty it seems that a few percent of a monolayer of carbon manifests clearly in the desorption spectrum at low carbon monoxide coverages. With the aid of CO desorption spectra the temperature dependence of the surface segregation of carbon was investigated at temperatures from 450 to 1300 K with the mean C/Pd atomic ratio in the bulk ranging from 1×10−6to 7×10−6. At any temperature below 835 K carbon does not appear on the surface. At higher temperatures carbon segregates at the surface very quickly and within a temperature range depending on the C/Pd ratio. Carbon that has been segregated on the surface can be easily redissolved even at temperature as low as 450 K. The behavior of carbon is explained in terms of formation and decomposition of the carbon‐rich palladium phase PdC0.13. Some implications for cleaning Pd(111) crystals are also shortly discussed.

ISSN:0734-2101    

DOI:10.1116/1.572177

出版商:American Vacuum Society    

年代:1983

数据来源: AIP

摘要:

Emission characteristics of single‐crystal LaB6cathodes of 〈100〉, 〈110〉, 〈111〉, 〈210〉, 〈310〉, and 〈321〉 orientations, with large tip radius (100 μm), were investigated. In cathodes of small tip radius (less than 10 μm) emission from the conical face is dominant, as it has the small area of the top surface. Cathodes of large tip radius have a large emission area at the top surface, which includes various crystal faces, according to the orientation and the cone angle. It has become clear that it is important to use as the tip axis the orientation having rotational symmetry and a crystal face of low work function at the cathode top to get good beam uniformity. In this respect the 〈100〉 cathode was found to be superior to cathodes of other orientations. Emission characteristics of the 〈100〉 cathode during long‐term operation were investigated. A flat (100) face was formed at the top due to LaB6material consumption, and emission characteristics reflecting this tip shape were measured.

ISSN:0734-2101    

DOI:10.1116/1.572178

出版商:American Vacuum Society    

年代:1983

数据来源: AIP

摘要:

Mode and current paths for a discharge in a vacuum switch placed in a magnetic field were investigated experimentally and analytically to find a possible method for measuring the pressure in the switch. A low‐pressure gas discharge is generated in the switch, and discharge properties show evidence that the arc shield, which is electrically floating, is an essential element. Simulators of the vacuum switch were assembled to determine the effects of the shield on the discharge. Pressure dependence and current distributions in various electric‐field configurations in the simulators were measured and analyzed. The discharge in the vacuum switch is identified as a series discharge of an inverted magnetron and of a magnetron through the shield as a common electrode. The mode for each elemental discharge is the same as that employed by cold‐cathode vacuum gauges. In the inverted magnetron, the current flows from the switch‐contact periphery at positive high voltage radially to the shield. In the magnetron, it flows from the shield end radially to the rod of a switch electrode, which is electrically grounded.

ISSN:0734-2101    

DOI:10.1116/1.572179

出版商:American Vacuum Society    

年代:1983

数据来源: AIP

摘要:

Properties of low pressure gas discharges generated in a vacuum switch placed in a magnetic field were investigated for an approach to a method of measuring pressure. The discharge was identified in a previous paper as a series crossed‐field discharge of an inverted magnetron and of a magnetron. The present experiments reveal discharge–current dependences on pressures, discharge voltages and magnetic‐field strengths. These dependences agree well with those deduced from properties of the two elemental discharges that are applicable to pressure measurement. Discharges were generated in various gas species, and discharge–current dependence on gas species was obtained. The series crossed‐field discharge was proved to be self‐sustaining, and an estimate supports the discharge stability.

ISSN:0734-2101    

DOI:10.1116/1.572180

出版商:American Vacuum Society    

年代:1983

数据来源: AIP

摘要:

This new shutter simply consists of a chopper wheel rotating a mere half‐millimeter away from the skimmer‐shaped diaphragm, which separates the source chamber from the flight tube. The repetition rate can be up to 104pulses per s (width∼60 μs), at an intensity of ∼1019molecules/sr s, whereas existing designs yield ∼1022molecules/sr s, but only at a rate of 1 pulse per 1–10 s. Our design has two main advantages: since there is no gas valve, cumbersome electromechanical devices with large current pulses can be avoided. Second, one is now free to choose the nozzle parameters (e.g.,p0,T0and the throat diameterdn). The beam parameters were determined by means of an electron impact detector featuring a high efficiency ionizer, thus improving the signal‐to‐noise ratio.

ISSN:0734-2101    

DOI:10.1116/1.572181

出版商:American Vacuum Society    

年代:1983

数据来源: AIP