Identifying surface intermediates with TPD: Methylchlorosilanes on Cu(001)

Various methylchlorosilane molecules (SiH$_{x}$ Me$_{y}$ Cl$_{z}$ , x+y+z=4) were exposed to a Cu(001) surface. Dissociative adsorption was observed for several hydrogen containing species, at surface temperatures above 160K. The chemistry and thermal stability of the surface bound fragments were then studied as a means for understanding intermediates of the commercially important ``Direct Process,'' namely production of Cl2(CH3)2Si, from Si and CH3Cl, with a Cu catalyst.~ Temperature programmed desorption indicates that methyl groups are readily transferred between absorbed Si-containing species. A large fraction of Cl remains on the surface after observation of typically 2 or 3 distinct TPD features below 450K. By a comparison of~ the product species distributions to the parent species, we are then able to propose key intermediates common to many of the adsorption/desorption mechanisms.