Monte Carlo simulation of gas desorption process induced by low-energy ions

The present paper discusses a simulated desorption phenomenon of gas chemisorbed on the surface of a solid target, induced by low-energy ions. The TRIM code is modified by introducing a cover layer of gas atoms chemisorbed on the surface of the solid target in order to simulate the desorption phenomenon. The physics model on the desorption process for the simulation is based on the Winters and Sigmund collision theory. The simulation results show that the desorption yield of gas atoms Y is linear with gas atom coverage density theta on the surface of a solid target, which is consistent with experimental results. According to the linear relation, the ion-induced desorption cross-section LT can be obtained easily. For H-1(1)+ --> O/Ti, H-2(1)+ --> O/Ti and H-3(1)+ O/Ti which usually occur in the interaction between plasma and the first wall in a controlled nuclear fusion device, sigma values obtained from the simulation results are 1.57 x 10(-21), 3.64 x 10(-21) and 5.38 x 10(-21) m(2), respectively, for incident energy of 60 eV and at normal incidence. (C) 2002 Published by Elsevier Science B.V.