摘要:

This paper reviews and analyzes the literature on thin carbon layers with emphasis on their use as protective overcoats for thin‐film magnetic media. We discuss carbon as a material, its preparation as a thin film, and review and evaluate various techniques for characterizing its thin‐film properties.

ISSN:0734-2101    

DOI:10.1116/1.574188

出版商:American Vacuum Society    

年代:1987

数据来源: AIP

摘要:

Vibration isolation technology for scanning tunneling microscopy (STM) to suppress the external mechanical perturbation down to a subatomic scale is described. The system is simplified into two subsystems, a tunneling assembly and a supporting table. Each of them has its own mechanical eigenfrequency. The principle of the isolation exists in making the two eigenfrequencies very different from each other. A theory of isolation developed is based on a model of multiply coupled oscillators with damping. Experimental results of the isolation characteristics for the two types of isolators constructed, one consisting of two‐stage coil springs and the other of multiply stacked metal plates with rubber pieces among them, are well explained by the theory. STM images of graphite are obtained by using these isolators combined with various tunneling assemblies. Thereby the basis for design of the isolators is clarified.

ISSN:0734-2101    

DOI:10.1116/1.574189

出版商:American Vacuum Society    

年代:1987

数据来源: AIP

摘要:

We have studied H2O adsorption on the Si(100) surface using photoelectron spectroscopy to record Si valence bands and Si 2pcore level spectra; and photon stimulated desorption to record Si 2pedge total electron yield and H+‐ion yield spectra. We assign the valence‐band H2O induced peaks atEB=6.3 and 11.2 eV to the Si–OH and to the O–H bonds, respectively. The H2O dosed Si 2pcore level spectrum exhibits two H2O induced equal intensity surface peaks with surface core level shifts of +0.25 and +1.00 eV that we assign to surface Si atoms in the Si–H and the Si–OH bonds, respectively. We interpret the features in the Si 2pedge H+‐ion yield spectrum as ion desorption from SiO2at surface defect minority sites. We conclude that H2O adsorbs dissociatively as H and OH radicals on the Si(100) 2×1 surface dimers and that there are defect minority sites on the surface where H2O adsorption causes SiO2formation.

ISSN:0734-2101    

DOI:10.1116/1.574190

出版商:American Vacuum Society    

年代:1987

数据来源: AIP

摘要:

High‐resolution x‐ray photoelectron spectroscopy has been used to study the formation of the aluminum/polyimide (Al/PI) interface at room temperature. Aluminum films up to 80 Å thick were vapor deposited onto cured polyimideinsitu. Our results show that Al is chemically active for coverages below ∼20 Å. Preferential aluminum bonding with PI occurs at carbonyl sites, as evidenced by the rapid attenuation of the carbonyl C 1score level photoemission intensity. In the initial reaction stage (1–2 Å), Al preferentially occupies planar imide rings. These adatoms transfer charge to carbonyl carbon atoms via oxygen and this resonance hybrid state of C–O–Al weakens, but does not break, carbonyl bonds. With increasing Al coverage, the formation of strong Al–O bonds is observed and is attributed to a C–O–Al complex compound. Metallic Al is observed at a nominal coverage of 2 to 5 Å. The Al/PI interface exhibits the attenuation behavior characteristic of cluster growth through both reacted and unreacted regions. Annealing the 80‐Å Al/PI interface at 300 °C results in extended reaction with less selective chemical interaction of Al with PI.

ISSN:0734-2101    

DOI:10.1116/1.574191

出版商:American Vacuum Society    

年代:1987

数据来源: AIP

摘要:

Aninsitufracture state for x‐ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy studies of internal surfaces in polycrystalline materials is described. The system offers the possibility to study both surfaces produced as a result of a fracture, allowing the comparison of physical and compositional features of one surface with those of its conjugate. The notched sample can be cooled to liquid‐nitrogen temperature prior to fraction. By using an electron collimator only photoelectrons from the fractured surface but not from the notch area are observed. The method is illustrated by XPS measurements obtained from fractured surfaces of an AlMgSiPb alloy (transgranular fracture), a Bi‐doped ZnO varistor (intergranular fracture), and polypropylene containing an antioxidant (interspherulitic fracture). The main motivation which led to the development of this fracture stage lies in the possibility to correlate the microstructure and microchemistry of internal surfaces with the relevant macroscopic properties of polycrystalline materials.

ISSN:0734-2101    

DOI:10.1116/1.574192

出版商:American Vacuum Society    

年代:1987

数据来源: AIP

摘要:

The electronic structure of the Ni/Si oxide/Si interface has been investigated using x‐ray photoelectron spectroscopy. This interface represents a more realistic situation encountered in semiconductor device processing technology. Approximately 35 Å of high‐purity Ni was sputter deposited on 〈111〉Si (covered with a thin native oxide layer) at room temperature. A sputter profiling technique was employed to determine the composition and reactivity as a function of depth. The measurements show considerable reactivity at the Ni/Si oxide/Si interface, even at room temperature. The Ni 2p3/2peak exhibits a gradual shift to higher binding energy which indicates that the overlayer cannot be regarded as a single unique nickel silicide phase. The large positive shift of the Ni 2p3/2and the small shift of the corresponding Si 2ppeak suggest that ionicity plays a nominal role in the Ni–Si chemical bond. The valence‐band spectra show a dominant 3d‐derived feature which gradually shifts to higher binding energy. The observed shifts in the Ni levels are attributed to the change in the electronic configuration of Ni in going from Ni‐rich silicide to Si‐rich silicide. A study of the composition as a function of depth shows that the Ni/Si oxide/Si interface is not sharply defined due to the interdiffusion of Ni and Si. Thus, the interface is identified as a graded transition region with composition ranging from Ni‐rich to Si‐rich silicide.

ISSN:0734-2101    

DOI:10.1116/1.574193

出版商:American Vacuum Society    

年代:1987

数据来源: AIP

摘要:

Data are presented obtained from a new design of high‐resolution (70 meV) and high‐sensitivity, fixed isochromat detector for use in inverse photoemission whose peak quantum efficiency is 20% at an energy of 10.08 eV. The detector design is of the Geiger type with a novel combination of a CaF2window and CS2vapor fill. The performance of this detector is compared with others currently being used. It is suggested that this design could provide an inexpensive viable alternative for high‐resolution spectroscopy systems. Inverse photoemission spectra obtained from a CuNi(111) surface in ultrahigh vacuum are presented.

ISSN:0734-2101    

DOI:10.1116/1.574194

出版商:American Vacuum Society    

年代:1987

数据来源: AIP

摘要:

The kinetics of reactions of CF3radicals on various substrate materials has been studied in a gold‐coated, stainless‐steel, very‐low‐pressure photolysis (VLPΦ) cell as a function of temperature and radical concentration. The substrate materials were gold, stainless steel, copper, copper oxide, and silica. The CF3radicals were generated from CF3I by IR‐multiphoton decomposition. The reaction products observed with a mass spectrometer included HF, CO, CO2, COF2, SiF4, and C2F6. Rate constants were obtained as a function of temperature. CF3reacted most rapidly on copper oxide surfaces; the other metal surfaces were less reactive, and the silica surfaces were least reactive. Previous studies from this laboratory that had reported the reaction of CF3on fused silica are reinterpreted as reactions of CF3on the stainless‐steel heater assembly.

ISSN:0734-2101    

DOI:10.1116/1.574195

出版商:American Vacuum Society    

年代:1987

数据来源: AIP

摘要:

The structural and electronic properties of the Cr/Si(111) interface formed at room temperature (RT) are investigated by low‐energy electron diffraction, x‐ray photoelectron spectroscopy and angle resolved ultraviolet photoemission spectroscopy, and work function measurements. The data indicate strong reactive behavior in agreement with a previous study by Franciosietal. The data show intermixing up to ∼25 monolayer (ML) Cr coverage with an overlayer stoichiometry evolving gradually from Si rich to Cr rich phases with increasing Cr coverage. The reacted phases are metastable and definitely different from any known bulk silicide. Above ∼30‐ML Cr coverage, polycrystalline bulk Cr metal is formed. Further insight into the nature of the intermixed layer comes from oxidation studies of the interface as a function of Cr coverage. A progressive shift of the oxidized Cr 3d, Cr 2p3/2, and Si 2plines with Cr coverage in the 0–25 ML range implies different oxidation states for Si and Cr species at various steps of the interface formation, and in turn, indicates a composition gradient normal to the surface. The data also demonstrate that above ∼2‐ML Cr coverage the oxygen uptake of the interface is up to 10 times faster than for definite silicides such as CrSi or CrSi2. The enhanced interface reactivity of the metallic RT grown Si–Cr phases apparently originates in their unique metastable bulk and surface composition and structure.

ISSN:0734-2101    

DOI:10.1116/1.574196

出版商:American Vacuum Society    

年代:1987

数据来源: AIP

摘要:

Platinum additions to aluminide coatings have been reported to be beneficial in both hot corrosion and oxidation environments. The data, however, are somewhat limited and strongly dependent upon structure and test conditions. Therefore, a study of the effects of surface structure under 1100 °C cyclic oxidation conditions of the platinum modified and the unmodified aluminide coatings on the IN‐738 substrate was initiated. During the early stages of this evaluation surface upheavals on the order of 50 μm, often called ‘‘rumpling,’’ were observed for both systems. The degree of rumpling was greater in the platinum modified coatings but was observed to a significant extent with the unmodified coatings as well. The amount of rumpling observed during cyclic testing can be attributed to a number of possible effects including (i) coefficient of thermal expansion mismatch, (ii) thermal gradient across the coated specimen, and (iii) coating mechanical properties. An effect of coating thickness is also observed although it must be noted that for diffusion‐type coatings such as the Pt–Al system, coatings with different thicknesses have different compositions. Therefore, the resulting performance of the coating is a complex interplay of the above‐mentioned variables. Excellent Al2O3adherence is seen for all the platinum modified aluminides tested, even on the highly convoluted surfaces. The role of rumpling in the high temperature protectively is not known but should be given more consideration as a potential high‐temperature degradation mechanism of these coatings.

ISSN:0734-2101    

DOI:10.1116/1.574197

出版商:American Vacuum Society    

年代:1987

数据来源: AIP