Materials Science and Engineering B 111 (2004) 156–163 Use of process indices for simplification of the description of vapor deposition systems Yuya Kajikawa ∗ , Suguru Noda, Hiroshi Komiyama Department of Chemical System Engineering, Graduate School of Engineering, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan Received 29 January 2004; accepted 7 April 2004 Abstract Vapor deposition is a complex process, including gas-phase, surface, and solid-phase phenomena. Because of the complexity of chemical and physical processes occurring in vapor deposition processes, it is difficult to form a comprehensive, fundamental understanding of vapor deposition and to control such systems for obtaining desirable structures and performance. To overcome this difficulty, we present a method for simplifying the complex description of such systems. One simplification method is to separate complex systems into multiple elements, and determine which of these are important elements. We call this method abridgement. The abridgement method retains only the dominant processes in a description of the system, and discards the others. Abridgement can be achieved by using process indices to evaluate the relative importance of the elementary processes. We describe the formulation and use of these process indices through examples of the growth of continuous films, initial deposition processes, and the formation of the preferred orientation of polycrystalline films. In this paper, we propose a method for representing complex vapor deposition processes as a set of simpler processes. © 2004 Elsevier B.V. All rights reserved. Keywords: Systems approach; Abridgement; Process index; Elementary process; Chemical vapor deposition; Physical vapor deposition 1. Introduction Materials are traditionally developed through the empiri- cal correlation of operating parameters of a production sys- tem and the resulting properties of the material produced [1]. Such correlations are still important for process devel- opment in materials science and engineering (MSE). How- ever, process development through a systems approach has also gained acceptance [1–3]. The systems approach inte- grates elements of processing, structure, properties, perfor- mance [1,2], and function [3]. Based on the systems ap- proach, the purpose of MSE should be to clarify the relation- ship among processing, structure, and properties to obtain desirable function and performance [1–3]. For example, band gap of nanoparticles is dependent on the size of those particles, and the size depends on processing conditions such as temperature and reactant concentration. To obtain desirable function and performance such as color, we control the band gap determining the color. The band gap is controlled by the size, which is controlled by pro- ∗ Corresponding author. E-mail address: kaji@chemsys.t.u-tokya.ac.jp (Y. Kajikawa). cessing conditions. Based on an understanding of the causal chain between processing, structure, and property, we can create processes to make materials with the desired func- tional and performance. Such a strategy is a basic manner for researchers working in MSE. However, these causal relationships are often difficult to understand because materials processing systems are often complex and composed of many elementary processes. For simplicity, we classify such systems as one of two types: complex and simple systems. Complex systems either con- tain many inter-linked elements or contain multiple elements linked to a target element. It is therefore difficult to achieve a comprehensive understanding of complex systems and to control the behavior of the target element. Simple systems contain few elements that are linked to a target element, such that they can be easily understood and the behavior of the target element can be controlled. Directly analyzing complex systems, without simplifica- tion, is sometimes required because every system cannot always be reduced to a simple system. Computer models are often used for such analysis, because they can provide a comprehensive description of the interaction of the ele- mentary processes. The value of such detailed simulations 0921-5107/$ – see front matter © 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.mseb.2004.04.013