摘要:

This paper deals with the evolution of a gas-solid interface during growth of amorphous CVD films. The aim of the analysis is to show that a comprehensive gas-solid CVD model may simplify significantly under conditions of two limiting cases: kinetic and diffusion-limited growth. The linear stability behavior of the simplified model was found to be almost identical to that of the original and more comprehensive model. It was found that planar film growth was inherently stable under kinetically controlled deposition conditions, but under diffusion-limited conditions, planar film stability depended on the magnitude of the dimensionless group 9Pe, which represents a Damkdhler number of deposition. Numerical solution of the simplified model showed that an increase in 9pe adversely affected the uniformity of film deposition. Predicted morphological phenomena were found to be very similar to experimental observations (Viljoen,et al,1994).

ISSN:0098-6445    

DOI:10.1080/00986449608936562

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Thin copper films have been deposited by the room temperature reaction of gaseous copper (II) hexa-fluoroacetylacetonate [Cu(hfa)2] with hydrogen atoms produced in a remote discharge tube. The resulting films are conductive and adherent on a wide variety of substrates. Copper atoms have been observed and measured in the gas phase and were found by atomic absorption spectroscopy to have a maximum concentration of approximately 1011atoms/cc in the mixing/reaction zone. The reaction of Cu(hfa)2with oxygen atoms was also studied. The reaction again resulted in the deposition of a film and in addition a green chemiluminescent glow was observed which was identified as due to the gaseous diatomic CuF molecule. Copper atoms were also observed by absorption spectroscopy within this chemiluminescent reaction with oxygen atoms. The copper atom concentration was found to be approximately the same as that found with the H-atom reaction. The copper atom concentrations and the relative emission intensities of CuF were studied as a function of time and position to gain insight into the deposition process.

ISSN:0098-6445    

DOI:10.1080/00986449608936563

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

The effects of low energy plasma processing on the morphological evolution of copper thin films is examined using atomic force microscopy. It is shown that there appears to be a coupling between the shape evolution of the surface morphology of the thin film to the grain size evolution within the internal microstructure of the film. A linear perturbation model based on localized changes in grain boundary curvature due to preferential grain boundary grooving, is developed to couple the microstructural stability of thin films to dynamic effects due to processing parameters. It is suggested that prior grain size gradients existing in the as-deposited nature of the film have a significant effect on the grain size stability based on flow by mean curvature concepts. Based on this approach, a theoretical framework using the formalism of Fokker-Planck equations, to relate the stochastic nature of atomistic processes Such as plasma processing to the physics of grain growth are also proposed.

ISSN:0098-6445    

DOI:10.1080/00986449608936564

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

In recent years, summers in the Northeast, as well as in many other regions of the United States, have reached record high temperatures. These unusually high ambient temperatures have led to the overloading of power transformer coolers, resulting in the inability of the coolers to maintain the top oil temperature of the transformer at an acceptable level. A field-tested solution to this problem is the application of water spray onto the tube bundles of the cooler to enhance the heat transfer. Currently, the standard way of applying water to an overheated transformer cooler is to hose it down. This method has always been implemented without consideration of the spray pattern or quantity or water used, usually resulting in a wastefully high rate of water consumption. An experiment has been setup to determine the performance of a transformer cooler subjected to water spray. This work consisted of the design and implementation of a water spray system to an existing fullscale cooling loop representative of those found on actual transformers. Predictions were also made for the top oil temperature subjected to dry-air cooling and compared with experimental data. The reliability of this model shows that it can be extended for water spray applications. Heat transfer data were obtained for a range of air velocities and water flow rates on this loop. The experimental results show a significant decrease in the top oil temperature of the cooler when water spray is applied to the cooler tubes. However, the enhancement was not as significant for water flow rates above 4 GPM. Distribution of the water spray through the tube bundle were qualitatively made by visual observation.

ISSN:0098-6445    

DOI:10.1080/00986449608936565

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Annealed thin films of Cu/Mg/SiO2are studied as possible conductors for microelectronics. Rutherford backscattering and sheet resistance measurements show that vacuum annealing at 350-400°C results in transport of Mg from the buried layer to the surface of the copper where it reacts with impurities to form a thin surface layer of MgO. Such films are then exceedingly resistant to further oxidation. These films have a resistivity of 2·μω-cm and are adherent to the SiO2substrate. However, at temperatures 450-500°C there is a reaction between Mg and the SiO2substrate releasing free Si into the copper.

ISSN:0098-6445    

DOI:10.1080/00986449608936566

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Conformality limitations and film composition variations inside features for films deposited at low pressures are explained using examples of studies which combine transport and reaction simulations of deposition processes and carefully designed experimental work. In the first example, the use of film profile information to decide between two kinetic models for the deposition of SiO2from TEOS is described. In the second example, composition profiles in sputter deposited Ti-W are explained in terms of titanium re-emission. Combined simulation and experimental studies of film profiles and composition profiles in features is a valuable tool in efforts to arrive at useful kinetic and transport models.

ISSN:0098-6445    

DOI:10.1080/00986449608936567

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

The motivation for this work was based on two hypotheses: subcritical nuclei of sucrose may be generated by secondary nucleation using a fluid shear field acting on the surface of a growing seed crystal in aqueous solutions, and a near-dynamic equilibrium distribution of embryos may be attained. These were supported experimentally. The value of a σ-based model parameter, a, was obtained by describing the system by a Boltzman- like distribution model. The number concentration of subcritical nuclei was well described by the model. Despite differences in experimental method and in the basic nature of the solute, sucrose, the behavior of the system and results were similar to those obtained in the earlier work using aqueous salt solutions [Sung et al. (1973), Jagannathan et al. (1980)].

ISSN:0098-6445    

DOI:10.1080/00986449608936568

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

In the pulp and paper industry, it is often necessary to characterize the drainage capability or a pulp on the paper machines. The industry uses a standard measure called the freeness to represent this and other properties for papermaking pulps.

ISSN:0098-6445    

DOI:10.1080/00986449608936569

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

In this work, the nucleation and film growth of copper on TiN chemically treated with WF6and air-exposed TiN by chemical vapor deposition(CVD) from hexafluoroacetylacetonate copper1trimethyl-vinylsilane, (HFA)Cu(TMVS), was studied. Copper grows as islands of poorly connected grains on air-exposed TiN. In contrast, copper grows as a continuous film with well-connected grains on the surface of WF6-treated TiN. The effect of TiN surface condition has been examined using Auger electron spectros-copy(AES), X-ray photoelectron spectroscopy(XPS) and scanning electron microscopy(SEM). On the basis of our experimental observation, and information in the literature, nucleation reaction mechanisms are proposed for the chemical vapor deposition of copper on the two different TiN samples.

ISSN:0098-6445    

DOI:10.1080/00986449608936570

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

A numerical analysis was performed to investigate the effect of recirculations formed by rectangular or triangular baffles on depolarization of concentration in a flat sheet membrane module. The k- ϵ turbulent model was used to predict the flow field in the flat channel. Control-volume-based finite difference methods were employed to solve for the two-dimensional fluid velocity and solute concentration distributions. We examined rigorously the effect of various parameters including the velocity, diffusivity, permeate flux, baffle size, baffle shape, and interbaffle spacing in an effort to find optimum operating conditions which may provide enhanced mass transfer. The vortices induced by the baffles on the membrane are found to be extremely effective in depolarizing the retained solutes at the membrane surface. The predictions show that baffle configurations and flow conditions have a great influence on depolarization of concentration. To achieve effective concentration depolarization, the baffle height should be greater than 0·5 (h = half the channel height) and the interbaffle spacing around 2h to 3h for the Reynolds number from 1,250 to 25,000. The simulated results indicate that the optimal Reynolds number is around 5,000 to 8,000 in view of both concentration polarization and energy consumption.

ISSN:0098-6445    

DOI:10.1080/00986449608936571

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor