摘要:

Using a general formulation, which describes the development of pressure during a thermal desorption experiment, a numerical approach has been derived to allow for an exact determination of the desorption rate, the effective binding energies and the preexponential factors from measured spectra independently of the heating rate. With the resulting parameters as input into assumed model rate equations the simultaneous integration of the pressure equation and these rate equations yield a theoretical temperature programmed desorption spectrum, which can be compared with the experiment.

ISSN:0734-2101    

DOI:10.1116/1.578736

出版商:American Vacuum Society    

年代:1993

数据来源: AIP

摘要:

The interfacial chemistry of Fomblin Z25, a commercial perfluoropolyether used as lubricant for space applications, with different metallic surfaces—440 C steel, gold, and aluminum—was studied. Thin layers of Fomblin Z25 were evaporated onto the oxide‐free substrates and the interfacial chemistry studied using x‐ray photoelectron spectroscopy and temperature desorption spectroscopy. The reactions were induced by heating the substrate and by rubbing the substrate with a steel ball. Gold was found to be completely unreactive towards Fomblin at any temperature. Reaction at room temperature was observed only in the case of the aluminum substrate, the most reactive towards Fomblin Z25 of the substrates studied. It was necessary to heat the 440C steel substrate to 190 °C to induce decomposition of the fluid. The degradation of the fluid was indicated by the formation of a debris layer at the interface. This debris layer, composed of inorganic and organic reaction products, when completely formed, passivated the surface from further attack to the Fomblin on top. The tribologically induced reactions on 440C steel formed a debris layer of similar chemical characteristics to the thermally induced layer. In all cases, the degradation reaction resulted in preferential consumption of the difluoroformyl carbon (–OCF2O–).

ISSN:0734-2101    

DOI:10.1116/1.578737

出版商:American Vacuum Society    

年代:1993

数据来源: AIP

摘要:

X‐ray photoelectron spectroscopy has been used to investigate the interaction between Cr and BPDA‐PDA polyimide for Cr coverages up to 18 Å. Detailed core level analysis reveals that the spectral changes induced by Cr deposition are a consequence of both the chemistry and the redistribution of reaction products in the overlayer. Two distinct N bonding configurations are readily resolved; one formed at lowest coverage remains localized at the buried interface, whereas the second becomes intermixed in the overlayer. Uniform overlayer growth is observed above ∼3.5 Å. The data for low Cr coverages are compared to molecular orbital calculations for two model bonding configurations. Agreement between theory and experiment for the C 1score level is better for a model compound with an O atom removed from the polymer backbone than for one where Cr is bound to a benzene ring. However, the quantitative differences suggest that a model should be considered where Cr interacts with carbonyl groups and additional reaction sites.

ISSN:0734-2101    

DOI:10.1116/1.578738

出版商:American Vacuum Society    

年代:1993

数据来源: AIP

摘要:

Pure and mixed targets of Li4SiO4, Li3PO4, and Li2O were sputtered in both argon and argon/oxygen process gases using a 1‐in. diam radio‐frequency planar magnetron source. The appearance of the sputter target, the self‐bias voltage of the target, the film deposition rate, and the optical emission of the plasma were monitored during film growth. The films were analyzed by energy dispersive x‐ray spectrometry, proton induced gamma emission, and atomic spectrometry. Films grown from targets of Li3PO4were found to be near stoichiometric. In contrast, films grown from targets of, or containing, Li4SiO4were lithium deficient due to the decomposition and segregation of Li2O away from the sputtered area on the surface of the target. A similar redistribution of material was observed for Li2O targets as well. Reproducible and homogeneous film compositions with stoichiometric lithium concentrations can best be achieved by codeposition with independently controlled sputter sources onto a rotating substrate.

ISSN:0734-2101    

DOI:10.1116/1.578739

出版商:American Vacuum Society    

年代:1993

数据来源: AIP

摘要:

Using facing targets and off‐axis direct‐current magnetron sputtering, we have prepared high quality YBa2Cu3O7−x(YBCO) superconducting thin films on ZrO2(100) withTc≤90 K (R=0) andJcas high as 1.6×106A/cm2(78 K, zero magnetic field) over an area of 70 mm diameter. Over this large area, the fluctuations ofTcand film thickness are from less than +0.9% to −1.3% and from +6.3% to −10%, respectively. In this article, also discussed are the differences between two sputtering modes used in our experiments, one of which gives larger area of superconducting thin film, higher deposition rate, and better thickness uniformity than the other. It is found that the smoothness and the temperature uniformity of the substrate holder are a of extreme importance for the fabrication of large area superconducting thin films. An electroquartz with little deformation during deposition has turned out to be very successful as the substrate holder in our fabrication.

ISSN:0734-2101    

DOI:10.1116/1.578740

出版商:American Vacuum Society    

年代:1993

数据来源: AIP

摘要:

Chemical composition and optical properties of TiO2films depend on deposition conditions. A detailed investigation has been made on the influence of deposition parameters, such as starting material, substrate temperature, and post deposition heating in air on the chemical composition of TiO2films deposited by electron‐beam evaporation of TiO and TiO2in neutral and ionized oxygen. The chemical composition of the films has been analyzed by x‐ray photoelectron spectroscopy and Auger electron spectroscopy. The composition of TiO2films deposited in neutral oxygen were found to contain lower oxides of titanium in addition to TiO2whereas films prepared in ionized oxygen were found to be stoichiometric TiO2.

ISSN:0734-2101    

DOI:10.1116/1.578741

出版商:American Vacuum Society    

年代:1993

数据来源: AIP

摘要:

In the process of making magnetic mirrors for ring laser gyroscopes a hard multilayer dielectric stack was deposited in the presence of a magnetic field. The thickness of the TiO2layers was nonuniform while the thickness of the SiO2layers was unaffected by the magnetic field. The thickness distribution was determined and the thickness variation of a single layer was measured. Speculations are presented as to the origin of the effect.

ISSN:0734-2101    

DOI:10.1116/1.578742

出版商:American Vacuum Society    

年代:1993

数据来源: AIP

摘要:

Recently, TEOS has been studied as a silicon source of silicon oxide films deposited by plasma chemical vapor deposition (CVD) because the deposited films show good step coverage compared with films deposited from SiH4. In this work, the authors deposited silicon oxide films using TEOS as a silicon source by using a low frequency (50 Hz) plasma CVD. It has been demonstrated in previous articles that low frequency (50 Hz) plasma CVD can deposit high quality silicon nitride films and amorphous carbon films without substrate heating. It is found in the present work that the substrate heating at deposition is required to obtain acceptable electrical properties when silicon oxide films are deposited from a TEOS and oxygen mixture, even by low frequency (50 Hz) plasma CVD. The films deposited at 200 °C from the plasma of a 3% TEOS mixture were found to be high quality insulating films; the resistivity was 1016Ω cm and the breakdown strength 7×106V/cm. Moreover, Auger electron spectrum analysis revealed that carbon atoms were not detected from the films in spite of the presence of carbon atoms in the TEOS molecule. With optical emission spectrum analysis of the TEOS and oxygen mixture plasma, strong emissions from the CO and CO2molecules were observed. It may be concluded that in the plasma carbon atoms react with oxygen atoms to yield the CO and CO2molecules which are stable enough to remain in the gas and thus not be taken into the films.

ISSN:0734-2101    

DOI:10.1116/1.578743

出版商:American Vacuum Society    

年代:1993

数据来源: AIP

摘要:

The optical properties of an electrostatic retarding field lens, which consists of an einzel lens and a retarding field between its exit and the image plane, are analyzed using both analytical and numerical methods. The results show that such a compound lens can be well approximated by a combination of three optical components: the einzel lens, an aperture lens superimposed at its exit, and a uniform field between its exit and the image plane. When the distance between the exit and the image plane is long, and a strong retardation is required for forming a low energy beam, the performance of such a compound lens is dominated by the chromatic aberration of the retarding field. Using this lens and a liquid metal ion source, it is possible to form a low energy (100 eV) focused ion beam with a diameter and current density of 1000 Å and 1 A/cm2, respectively.  

ISSN:0734-2101    

DOI:10.1116/1.578744

出版商:American Vacuum Society    

年代:1993

数据来源: AIP

摘要:

Models of differential electrical networks are introduced as analogs of the pumping action and the leakage effects. A concept of synthetic modified compression ratio is suggested to refine the analysis. The theoretical expectations are verified by the experimental results. The design work of turbomolecular pumps can be simplified by using this method.

ISSN:0734-2101    

DOI:10.1116/1.578745

出版商:American Vacuum Society    

年代:1993

数据来源: AIP