摘要:

A technique has been developed to study the differences in the nucleation and growth of metallic films during their vacuum thermal deposition. The ‘‘P’’ and ‘‘Q’’ resistance arms of a Wheatstone bridge are made equal and arms ‘‘R’’ and ‘‘S’’ are replaced by two substrates having proper contacts, facing the vapor source in the vacuum chamber. During deposition, if nucleation and growth conditions of the films on these substrates are exactly identical, no voltage difference is developed across the junctions ‘‘PQ’’ and ‘‘RS’’ of the bridge throughout the growth of the films. If, however, there is even a minute difference in the nucleation and growth sequence of these films, the critical time at which the films become conductive may be different for both the films which ultimately gives a rectangular pulse‐type signal which is recorded by the X–Y recorder. As the critical thickness at which the metal film becomes suddenly conductive is dependent on a large number of factors, e.g., flux and species of vapor, structure and temperature of the substrate, residual gas pressure and its nature, fields present on or nearby the substrate etc., this technique has potential applications in metallic thin film technology.

ISSN:0734-2101    

DOI:10.1116/1.572032

出版商:American Vacuum Society    

年代:1983

数据来源: AIP

摘要:

Electrical, optical, and structural properties of ultrathin films of Ag, Au, and Al were investigated. MOS solar cells were fabricated with Ag, and Au barrier metals onn‐type and with Al barrier metal onp‐type silicon. The short‐circuit current densityJscwas measured as a function of the average metal layer thicknesstm. The film structure was examined under a transmission electron miscroscope. The optical transmittanceTwas measured as a function of the wavelength λ withtmas a parameter. The transmission electromicrographs indicated that, in the Ag and Au case, the film network structure attained electrical continuity at a lower value oftmthan in the case of Al. Also, in the Ag and Au case, surface covered by the film was lower. Largely due to this, optical transmittance was higher in the Ag and Au case than in the case of Al. TheT(λ) characteristics exhibited strong features in the Ag and Au case but not in the Al case. The profiles ofJsc(tm) were found to be peaked with the maximum occuring around 55 Å for Ag and Au and around 70 Å for Al. Furthermore, the peaks were sharp in the Al case, but were broad in the Ag and Au case. Also, the peak values were larger in the Ag and Au case. The higher rate of degradation of Ag and Au MOS cells than Al MOS cells can be related to the presence of large discontinuity in Ag and Au films.

ISSN:0734-2101    

DOI:10.1116/1.572033

出版商:American Vacuum Society    

年代:1983

数据来源: AIP

摘要:

The production of methane on carbon (papyex) surfaces under sub‐eV atomic hydrogen bombardment has been measured in an ultrahigh vacuum system subjected to special cleaning procedures. These results and previously published methane yield results are compared and their applicability to fusion technology is assessed. A critical analysis of the available data leads to the following conclusions: (i) The inconsistent methane yields spanning four orders of magnitude are most likely due to different experimental procedures. (ii) The monotonically decreasing methane yield as a function of sample temperature, obtained by some groups, is most probably due to the fact that deactivated surfaces were exposed to hydrogen bombardment. (iii) The methane yields which present a maximum at a certain temperature in the range 700–850 K resulted from bombardment of activated surfaces; and (iv) the shift in temperature at which the methane yield maximum occurs in the different studies may be due to temperature nonuniformities over the exposed surfaces and/or different states of activation.

ISSN:0734-2101    

DOI:10.1116/1.572034

出版商:American Vacuum Society    

年代:1983

数据来源: AIP

摘要:

After several hours of discharge cleaning, it has been observed that the decay time of the water‐vapor partial pressure changes from one well defined value to another. A long decay time observed in the later phase can be interpreted as a result of a slow deoxidization rate of chromium oxide, which may dominate the cleaning process in this phase. Optimization of the electron density for the cleaning is discussed, comparing the experimental results on density dependence of the water‐vapor partial pressure with a result based on a zero‐dimensional calculation for particle balance. One of the essential points for effective cleaning is found to be raising the electron density of the plasma high enough that the dissociation loss rate of H2O is as large as the sticking loss rate. A density as high as 1011cm−3is required for a clean surface condition where sticking probability is presumed to be around 0.5.

ISSN:0734-2101    

DOI:10.1116/1.572035

出版商:American Vacuum Society    

年代:1983

数据来源: AIP

摘要:

The recombination rate coefficient of the ISX‐B vacuum vessel wall has been measured by observing the rate of decrease of gas pressure in the vesssel during a glow discharge. A simple analytic expression which relates the rate of change of the pressure to the recombination rate is derived and verified by comparison with a complete numerical simulation. Comparison of the recombination coefficient measured in ISX‐B with previous laboratory measurements shows that the measured value is typical for a stainless steel surface covered with an oxide layer.

ISSN:0734-2101    

DOI:10.1116/1.572036

出版商:American Vacuum Society    

年代:1983

数据来源: AIP

摘要:

Reaction rates for the production of DT from D2+T2mixtures are reported as a function of pressure, initial T2concentration, and concentration of the impurity of CT4. The reactions took place in a specially constructed stainless steel container. The reactions are reproducible and can be explained in terms of the ion–molecule chain model of Thompson and Schaeffer. The presence of T2O as an impurity has no measurable effect at the measured concentration.

ISSN:0734-2101    

DOI:10.1116/1.572037

出版商:American Vacuum Society    

年代:1983

数据来源: AIP

摘要:

Permeation of three hydrogen isotopes, methane, and inert gases were measured for a tetrafluoroethylene (TFE) and a polyethylene (PE) film at room temperature by means of the time‐lag method in order to establish physicochemical properties which determine the solubility and the diffusivity of these gases. It was observed that the diffusion constant of the inert gases changed exponentially with the heat of vaporization, and their solubility constant was an exponential function of the Lennard‐Jones force constant of the gases for both films. On the other hand, hydrogen isotopes and methane deviated from these relations. It is concluded that the dispersive force plays an important role for the solution and the diffusion of the inert gases, whereas chemical interactions between the solute and the solvent play an important role.

ISSN:0734-2101    

DOI:10.1116/1.572038

出版商:American Vacuum Society    

年代:1983

数据来源: AIP

摘要:

A system is described in which plasma/surface treatments can be performed and the substrates can be analyzed by x‐ray photoelectron spectroscopy by transferring them via a load lock into the analytic chamber. Also described are some plasma etching experiments that demonstrate the utility of this apparatus. The system emulates larger systems in which plasma treatments are performed at pressures, voltages, and power densities similar to those employed in large commercial systems.

ISSN:0734-2101    

DOI:10.1116/1.572039

出版商:American Vacuum Society    

年代:1983

数据来源: AIP

摘要:

The design and performance of a new electron spectrometer for high resolution electron energy loss (EELS) analysis of surface vibrations is described. Based on the 127° cylindrical deflection analyzer (CDA), the spectrometer incorporates a two‐stage monochromator, a new lens system with out‐of‐plane focusing, relatively large (60 mm) energy‐dispersing elements, and stringent magnetic field attenuation. Basic spectrometer geometry is compatible with commercial surface analysis systems employing Auger electron spectroscopy (AES), photoelectron spectroscopy (ESCA), low energy electron diffraction (LEED), etc. Performance of the instrument is shown to equal or exceed that of other spectrometers in terms of monochromatic current for a given energy resolution. An overall system resolution of 3.5 meV (28 cm−1) FWHM is routinely achieved at 1.5×10−10A incident current and high signal levels (105–107cps) for elastic beam reflection. A higher resolution of 2.5 meV (20 cm−1) has been obtained but with substantial sacrifice of signal level. Performance of the spectrometer is illustrated for the cases of direct (potential barrier) reflection from a palladium(100) crystal surface and for carbon‐monoxide adsorption.

ISSN:0734-2101    

DOI:10.1116/1.572040

出版商:American Vacuum Society    

年代:1983

数据来源: AIP

摘要:

The chemical compounds present on the surface of CdTe have been investigated after different surface preparations and correlated with the properties of junctions formed by Cr on the CdTe. X‐ray photoelectron spectroscopy (XPS) analysis indicates that four different surface compositions result from five different treatments. Cleaving leaves a stoichiometric surface whereas oxidation in air leads to the formation of TeO2. Bromine‐in‐methanol etch leaves a Te‐enriched surface and chromate etch leaves a surface containing both TeO2and excess Te. Hydrogen heat treatment of an etched CdTe surface restores a stoichiometric cleavedlike surface from that disrupted by the etching process. Effects on the properties of subsequently formed junctions are evidenced by a decrease in the diode saturation current from 2×10−5for a bromine‐etched surface to 2×10−8A/cm2for a cleaved surface.

ISSN:0734-2101    

DOI:10.1116/1.572170

出版商:American Vacuum Society    

年代:1983

数据来源: AIP