Michael E. Coltrin

A Mathematical Model of the Coupled Fluid Mechanics and Chemical Kinetics in a Chemical Vapor Deposition Reactor

The authors describe a numerical model of the coupled gas-phase hydrodynamics and chemical kinetics in a silicon chemical vapor deposition (CVD) reactor. The model, which includes a 20-step elementary reaction mechanism for the thermal decomposition of silane, predicts gas-phase temperature, velocity, and chemical species concentration profiles. It also predicts silicon deposition rates at the heated reactor wall as a function of susceptor temperature, carrier gas, pressure, and flow velocity. The authors find excellent agreement with experimental deposition rates, with no adjustment of parameters. The model indicates that gas-phase chemical kinetic processes are important in describing silicon CVD.

A Mathematical Model of Silicon Chemical Vapor Deposition Further Refinements and the Effects of Thermal Diffusion

Description du modele qui est applique au depot de Si a partir de silane. Le modele predit les domaines de temperature et de vitesse en phase gazeuse

A Mathematical Model of the Fluid Mechanics and Gas‐Phase Chemistry in a Rotating Disk Chemical Vapor Deposition Reactor

We describe a mathematical model of the coupled fluid mechanics and gas-phase chemical kinetics in a rotating-disk chemical vapor deposition reactor. The analysis uses a similarity transformation that reduces the problem to a one-dimensional boundary value problem. The deposition of silicon from silane is used as an example system. We present predictions of deposition rate as a function of susceptor temperature, spin rate, and carrier gas. 12 refs.

SURFACE CHEMKIN-III: A Fortran package for analyzing heterogeneous chemical kinetics at a solid-surface - gas-phase interface

This document is the user`s manual for the SURFACE CHEMKIN-III package. Together with CHEMKIN-III, this software facilitates the formation, solution, and interpretation of problems involving elementary heterogeneous and gas-phase chemical kinetics in the presence of a solid surface. The package consists of two major software components: an Interpreter and a Surface Subroutine Library. The Interpreter is a program that reads a symbolic description of a user-specified chemical reaction mechanism. One output from the Interpreter is a data file that forms a link to the Surface Subroutine Library, which is a collection of about seventy modular Fortran subroutines that may be called from a user`s application code to return information on chemical production rates and thermodynamic properties. This version of SURFACE CHEMKIN-III includes many modifications to allow treatment of multi-fluid plasma systems, for example modeling the reactions of highly energetic ionic species with a surface. Optional rate expressions allow reaction rates to depend upon ion energy rather than a single thermodynamic temperature. In addition, subroutines treat temperature as an array, allowing an application code to define a different temperature for each species. This version of SURFACE CHEMKIN-III allows use of real (non-integer) stoichiometric coefficients; the reaction order with respect to species concentrations can also be specified independent of the reaction`s stoichiometric coefficients. Several different reaction mechanisms can be specified in the Interpreter input file through the new construct of multiple materials.

A model of elementary chemistry and fluid mechanics in the combustion of hydrogen on platinum surfaces

Abstract Using computational methods, we consider the catalyzed combustion of lean hydrogenoxygen mixtures in a stagnation flow over a platinum surface and in a flat-plate boundary layer. The analysis includes elementary chemistry in the gas phase as well as on the surface. The stagnation flow is modeled using a similarity transformation that leads to a one-dimensional boundary-value problem, whereas the flat-plate boundary layer is modeled by the use of the boundary-layer assumption. Predictions of each model are compared with experimental measurements of (a) catalytic ignition and combustion of hydrogenoxygen mixtures at low pressure (100 millitorr) and (b) OH concentration profiles in catalytically supported combustion at atmospheric pressure. The article proposes reaction mechanisms and interprets the catalytic behavior in terms of the chemistry models.

Reactive sticking coefficients for silane and disilane on polycrystalline silicon

Reactive sticking coefficients (RSCs) were measured for silane and disilane on polycrystalline silicon for a wide range of temperature and flux (pressure) conditions. The data were obtained from deposition‐rate measurements using molecular beam scattering and a very low‐pressure cold‐wall reactor. The RSCs have nonlinear Arrhenius temperature dependencies and decrease with increasing flux at low (710 °C) temperatures. Several simple models are proposed to explain these observations. The results are compared with previous studies of the SiH4/Si(s) reaction and low‐pressure chemical vapor deposition‐rate measurements.

Solid-State Lighting: An Integrated Human Factors, Technology, and Economic Perspective

Solid-state lighting is a rapidly evolving technology, now virtually certain to someday displace traditional lighting in applications ranging from the lowest-power spot illuminator to the highest-power area illuminator. Moreover, it has considerable headroom for continued evolution even after this initial displacement. In this paper, we present a high-level overview of solid-state lighting, with an emphasis on white lighting suitable for general illumination. We characterize in detail solid-state lightings past and potential-future evolution using various performance and cost metrics, with special attention paid to inter-relationships between these metrics imposed by human factors, technology, and economic considerations.

Solid-state lighting: an energy-economics perspective

Artificial light has long been a significant factor contributing to the quality and productivity of human life. As a consequence, we are willing to use huge amounts of energy to produce it. Solid-state lighting (SSL) is an emerging technology that promises performance features and efficiencies well beyond those of traditional artificial lighting, accompanied by potentially massive shifts in (a) the consumption of light, (b) the human productivity and energy use associated with that consumption and (c) the semiconductor chip area inventory and turnover required to support that consumption. In this paper, we provide estimates of the baseline magnitudes of these shifts using simple extrapolations of past behaviour into the future. For past behaviour, we use recent studies of historical and contemporary consumption patterns analysed within a simple energy-economics framework (a Cobb‐Douglas production function and profit maximization). For extrapolations into the future, we use recent reviews of believed-achievable long-term performance targets for SSL. We also discuss ways in which the actual magnitudes could differ from the baseline magnitudes of these shifts. These include: changes in human societal demand for light; possible demand for features beyond lumens; and guidelines and regulations aimed at economizing on consumption of light and associated energy. (Some figures in this article are in colour only in the electronic version)

Computational simulation of diamond chemical vapor deposition in premixed C2H2/O2/H2 and CH4O2-strained flames

We have modeled combustion synthesis of CVD diamond in a stagnation-flow reactor under atmospheric conditions. In this configuration a premixed flat flame flows over a flat deposition substrate that lies perpendicular to the flow and parallel to the burner face. Optimal growth conditions occur when the flame is lifted from the burner surface and stabilized at the deposition surface. A similarity transformation for the stagnation flow field reduces the governing equations to a one-dimensional boundary value problem, significantly simplifying the computational task. The simulations include elementary gas-phase and surface chemistry as well as multicomponent molecular transport in the flame gas. Our model shows good qualitative agreement with observed growth parameters for the experimental conditions of Murayama et al. [1], who employed a premixed C2H2/H2/O2 gas mixture. Modeling CH4O2 flame synthesis demonstrates that methane is less effective for diamond growth due to the decreased flame temperature and stability compared with C2H2 combustion.

Understanding nonpolar GaN growth through kinetic Wulff plots

In this paper we provide explanations to the complex growth phenomena of GaN heteroepitaxy on nonpolar orientations using the concept of kinetic Wulff plots (or v-plots). Quantitative mapping of kinetic Wulff plots in polar, semipolar, and nonpolar angles are achieved using a differential measurement technique from selective area growth. An accurate knowledge of the topography of kinetic Wulff plots serves as an important stepping stone toward model-based control of nonpolar GaN growth. Examples are illustrated to correlate growth dynamics based on the kinetic Wulff plots with commonly observed features, including anisotropic nucleation islands, highly striated surfaces, and pentagonal or triangular pits.