CONTROL OF PEELING DURING CHEMICAL DEPOSITION OF THIN FILMS OF Bi₂S₃ BY SURFACE PRETREATMENT WITH FUNCTIONALIZED SILANES

Abstract

Clean glass surfaces have been treated with a series of compounds having the general formula, (CH₃O)₃Si(CH₂)₃X, where X is a selected functional group. Thin films of Bi₂S₃ were then deposited on the treated surfaces. The tendencies of the films to peel were observed as X was varied. The greatest resistance to peeling occurred when X was SH or (CH₂)₁₄CH₃. Scanning electron microscopy showed that Bi₂S₃ films deposited on the surfaces having terminal SH groups had smaller particle size, were more homogeneous in appearance and possessed smaller intercrystalline voids than those deposited on untreated surfaces. The improvement of resistance to peeling after treatment with (CH₃O)₃Si(CH₂)₃SH is explained in terms of the formation of an initial glass-O-Si bond and the subsequent formation of a covalent Bi-S bond to the silane layer bound to the glass. Although the films prepared with X as (CH₂)₁₄CH₃ did not peel readily, they were easily separated from the glass surface by mechanical means.

Key Words:

• Thin films
• silanes
• electron microscopy
• bismuth sulfide