Affinity of Polystyrene Films to Hydrogen-Passivated Silicon and Its Relevance to the T g of the Films

• Published in: Macromolecules 2009-10, Vol.42 (19), p.7418-7422
• Main Authors: Fujii, Yoshihisa, Yang, Zhaohui, Leach, Jessica, Atarashi, Hironori, Tanaka, Keiji, Tsui, Ophelia K. C
• Format: Article
• Language: English
• ISSN: 0024-9297; 1520-5835
• DOI: 10.1021/ma901851w

Qualitatively different thickness dependences have been observed in the glass transition temperature, T g, of polystyrene (PS) films supported by hydrogen-passivated silicon (H−Si). It has been suggested that upon annealing at high temperatures in air, the polymer/substrate interface of these films (i.e., PS/Si), though buried underneath the PS layer, might be oxidized, rendering the films a different polymer/substrate interface (i.e., PS/SiO x −Si), which may account for the different thickness dependences of the T g observed. In this experiment, we examine if the buried substrate interface of PS/H−Si films can indeed be oxidized by annealing the films at 150 °C in air. Our result shows that a residual film does form on top of the H−Si surface, but it is a bound layer of PS. X-ray photoelectron spectroscopic (XPS) analyses and independence of the residual film on the initial PS thickness evidence that the H−Si substrate buried underneath a PS film is not oxidized by annealing. We discuss a possible explanation to how the different thickness dependences may be observed in the T g of these films.