A Basic Monte Carlo Model of Initiated Chemical Vapor Deposition Using Kinetic Theory
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A Basic Monte Carlo Model of Initiated Chemical Vapor Deposition Using Kinetic Theory Hayley R. Osman and Saibal Mitra Missouri State University, Department of Physics, Astronomy, and Materials Science, Springfield, MO 65807, U.S.A. ABSTRACT Initiated Chemical Vapor Deposition (iCVD) is a well-known method for depositing polymers that are used in chemical, biological, and electrical applications. It is a variation of hot filament deposition and can used to produce conformal coatings of polymer films at relatively low reaction temperatures. It is also a solventless technique in which thin polymeric films are deposited by introducing controlled ratios of monomer and initiator gasses into the reaction chamber. Low temperatures in the reaction chamber allow the deposition of polymer films on a wide variety of substrates that include biological substrates. We have simulated the growth of a monolayer of polymer films on two-dimensional surfaces using Monte Carlo simulation. We saw the formation of polymer chains over a time scale on the order of microseconds. We have assumed the substrate to be at room temperature while the reactor pressure close of 800 mTorr. The grid on which we have simulated this polymer growth is represented by a 100x100 matrix, on which a series of specialized functions are executed in each time-step, or iteration. These functions can be divided into three categories: population, translation, and polymerization. The goal of this simulation is to observe the initial growth of the iCVD surface reaction. We have obtained favorable results with the simulation and we are now looking to compare these results with experimental results for initiation growth. INTRODUCTION An attractive method to grow ultra-thin, conformal polymer films is by initiated chemical vapor deposition (iCVD). While CVD is a mature technology, application of iCVD for polymer films is a new development. In this process, polymers are deposited from vapor phase monomers. It was demonstrated that the reaction rates are greatly enhanced and are more controllable upon the introduction of initiator molecules1. Typically, a volatile initiator molecule is mixed with the monomer and activated over a heated filament in a vacuum chamber. iCVD is a one-step film growth method which mimics the free-radical chain growth polymerization. The chemical vapor deposition process has been modeled previously2 to better understand the molecular kinetics of the surface reaction. Successful simulations have been applied to diamond, microwave plasma, and hot filament reactions3,4 using a kinetic Monte Carlo model. These models are beneficial in maximizing reaction probability in order to increase growth rate of thin polymer films. The iCVD reactor in our laboratory is a stainless steel chamber with an array of nickelchrome filaments. The copper electrodes allow the placing of evenly spaced filaments across the substrate (which sits below the filament). This geometry allows for the even distribution of temperature. The filaments are resistively heated and the t
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