摘要:

The chemical vapor growth technique has been used extensively for the preparation and crystal growth of electronic materials either in the bulk form or as thin layers on substrate surfaces. Using the chemical transport technique or the reaction of gaseous compounds containing the constituents of the desired material, electronic materials with thicknesses in a wide range can be prepared at temperatures considerably below their melting points or decomposition temperatures. Furthermore, the impurity concentration and distribution in the product can be controlled to an extent not obtainable by other techniques. The recent progress in the chemical vapor growth of semiconductors, insulators, conductors, magnetic materials, and superconductors is discussed with emphasis on the epitaxial growth of semiconductors.

ISSN:0022-5355    

DOI:10.1116/1.1317938

出版商:American Vacuum Society    

年代:1973

数据来源: AIP

摘要:

An ultra high vacuum epitaxy system is described, including special features such as computer control. The system is capable of preparing sophisticated structures requiring a high degree of precise control. GaAlAs films have been grown and evaluated by various techniques; He-ion backscattering and Raman spectroscopy have been shown to be particularly valuable for periodic structures. A structure with a very narrow period has been made, and its transport properties measured and interpreted by the superlattice mechanism.

ISSN:0022-5355    

DOI:10.1116/1.1317919

出版商:American Vacuum Society    

年代:1973

数据来源: AIP

摘要:

NbN, a binary B-1 structure superconducting compound, has been successfully prepared in thin film form by a high-purity sputtering process [J. R. Gavaler, J. K. Hulm, M. A. Janocko, and C. K. Jones, J. Vac. Sci. Technol. 6, 177 (1969)]. In this paper, we report on the deposition of ternary compounds, based on NbN, using a similar technique. The inclusion of a third element, such as carbon, titanium, or zirconium into the NbN structure was accomplished by sputtering in an argon-nitrogen atmosphere from a two-element target. These targets were made either by hot pressing a powder mixture of the elements into a proper form or by welding together two metal sheets into a single unit. Superconducting transition temperatures of ≳ 17 K have been obtained in both Nb–C–N and Nb–TiN thin films by depositing these films at very high temperatures. However, critical current and field data measured at 4.2 K showed that the use of very high substrate temperatures also caused a deleterious effect on these properties.

ISSN:0022-5355    

DOI:10.1116/1.1317933

出版商:American Vacuum Society    

年代:1973

数据来源: AIP

摘要:

Niobium carbide thin films have been sputter deposited in a reactive argon and methane plasma at substrate temperatures of 700 °C. The background pressure prior to sputtering was typically in the low10−7-Torrrange, the total sputtering pressure was maintained at2×10−3 Torrand the partial pressure ratios of argon and nitrogen were monitored and controlled with a residual gas analyser.Jc–Hcharacteristics were measured by applying a pulsed field and pulsed current method and transition temperatures were determined by recording resistivity versus sample temperature. The structure was studied by x-ray diffraction.Hc2is about 40 kOe and the highestTcis 9.6 K. Several carbide phases and their mixtures were observed and have been correlated to the partial pressure ratios of the plasma.

ISSN:0022-5355    

DOI:10.1116/1.1317942

出版商:American Vacuum Society    

年代:1973

数据来源: AIP

摘要:

A prerequisite for conducting valid corrosion experiments byin situelectron microscopy techniques is not only the achievement of UHV background pressure conditions at the site of the specimen but also the ability to clean the surface of the thin metal substrate specimen before initiation of the corrosive interaction. A miniaturized simple ion gun has been constructed for this purpose. The gun is small enough to be incorporated into an UHV electron microscope specimen chamber with hot stage in such a way as to permit bombardment of the substrate specimen while observing it by transmission electron microscopy TEM. It is shown that the ion beam generated is confined well enough to cause a sputtering removal of substrate material at a rate of approximately 5–10 Å/min and to prevent the sputter deposition of contaminating material from the specimen holder. Thin single crystal Ni (100) film samples were used to demonstrate the applicability of the sputter cleaning technique, to show the removal of ion beam induced radiation damage by annealing, and to evaluate preliminary oxidation tests by selected zone dark-field microscopy.

ISSN:0022-5355    

DOI:10.1116/1.1317948

出版商:American Vacuum Society    

年代:1973

数据来源: AIP

摘要:

The chemisorption of CO on Ni(110) has been studied at temperatures down to −145 °C, by means of LEED, Auger and work function measurements, and flash desorption. Since electron impact caused dissociation of the adsorbed molecules, precautions had to be taken to minimize spurious effects. The LEED patterns showed considerable disorder but could be described approximately by the sequencec(2×2)→(4×2)→c(2×1). These structures suggest that both linear and bridged bonding of CO occurs on Ni(110), and flash desorption revealed two bindings states separated by ∼0.2 eV. The isosteric heat of adsorption for the lower energy state was found to be 1.1 eV. The maximum work function change was 1.6 eV.

ISSN:0022-5355    

DOI:10.1116/1.1317970

出版商:American Vacuum Society    

年代:1973

数据来源: AIP

摘要:

Orbital energy spectra of CO and Hg adsorbed individually and co-adsorbed on Ni (100) have been determined by ion-neutralization spectroscopy (INS) and ultraviolet photoelectron spectroscopy (UPS) at 45 ° incidence. In the case of CO, two orbitals derived from the 5σ and 1π orbitals of free CO are observed 7.8 and 11.1 eV below the Fermi level, respectively, by UPS, with INS revealing only the 7.8-eV orbital since 11.1 eV is outside its accessible range. In the case of Hg, UPS and INS both reveal orbital peaks 7.8 and 9.7 eV belowEF, identified, respectively, with the5d5/2and5d3/2states of Hg. The Hg(6s) orbital is not in evidence in the energy spectra obtained by either method. We have determined energy shifts of the observed orbitals with respect to their positions in the free molecule or atom and have discussed these shifts in terms of the effects of bonding and electric charge shifts in the metal-adsorbate complexes. This work permits a fairly detailed intercomparison of INS and UPS. It also bears on the problem of peak shifts due to interference between bulk and surface photoemission and possible perturbation by the probing ion in the case of ion neutralization.

ISSN:0022-5355    

DOI:10.1116/1.1318036

出版商:American Vacuum Society    

年代:1973

数据来源: AIP

摘要:

A cylindrical mirror electron energy analzyer has been used to study the adsorption and decomposition of CO on an initially clean Pt(111) surface. The observed rate of adsorption and fractional surface coverage as a function of CO exposure are identical to those observed previously in this laboratory by flash filament adsorption technique. This result provides an absolute calibration of the Auger spectrometry system for carbon and oxygen. Beam-induced decomposition of CO was observed at high incident fluxes. The surface oxygen coverage decreased exponentially to zero during electron bombardment, while surface carbon decreased and then levelled off at a finite value. CO adsorption studies on this carbon contaminated surface showed decreasing CO adsorption rate and decreasing saturation coverage with increasing carbon contamination. The adsorption rate approached zero at high carbon concentration.

ISSN:0022-5355    

DOI:10.1116/1.1318038

出版商:American Vacuum Society    

年代:1973

数据来源: AIP

摘要:

The release of ions and excited neutrals by the interaction of low energy electrons with CO on (100) W is studied by a time-of-flight technique. The flight time distributions, approximate threshold energies, adsorption kinetics, and dependence behavior of the desorbed particle currents upon heating and heavy electron bombardment are presented for the excited neutrals,CO+andO+ions in the temperature range 110–600 K. The fact that the binding state producing the excited neutrals is identical with the state releasingCO+ions suggests that the excited neutrals are CO molecules.

ISSN:0022-5355    

DOI:10.1116/1.1318039

出版商:American Vacuum Society    

年代:1973

数据来源: AIP

摘要:

Line shapes of Auger electron spectra have been analyzed in the derivative modedN/dEto obtain evidence of chemisorption bond characteristics of sulfur and nitrogen in two different chemical environments. Sulfur in a monolayer surface structure on nickel,Ni(110)–c(2×2)Sis characterized as having a residuald-band and two (molecular orbital) resonances, as first depicted by ion-neutralization spectroscopy; while sulfur in a cleaved surface (112¯0) of CdS displays only filled band properties with no resolvable resonance structure. Nitrogen adsorbed on Ni(110) is characterized by a residuald-band and two resonances: one at ∼12 eV and the other at ∼25 eV below the vacuum zero. The analysis is consistent with data published earlier on a characteristic energy-loss description of Ni(110)-(disordered)N. Nitrogen adsorbed on Si(111) appears to have similar resonances at 13 eV and 27 eV below the vacuum zero with no other intervening band structure.

ISSN:0022-5355    

DOI:10.1116/1.1318040

出版商:American Vacuum Society    

年代:1973

数据来源: AIP