Poly(chloro-p-xylylene) thin films are shown to have a changing morphology as a function of deposition temperature from spectroscopic ellipsometry and X-ray diffraction measurements. At lower deposition temperatures, the as-deposited polymer exhibited negative birefringence attributed to the presence of amorphous conformationally disordered polymer chains. As the deposition temperature was increased the polymer chains became more conformationally ordered resulting in an increase in the thin film’s birefringence. At higher deposition temperatures, above the polymer’s Tg evidence of crystallinity was apparent from X-ray diffraction results. The increase in the thin film’s birefringence may be attributed to the thermodynamic driving force for crystallization causing the plane of the phenyl group to orient more perpendicular to the plane of the substrate, evidently the more stable conformation for poly(chloro-p-xylylene). After an inert post-deposition anneal at 2108C for 2 h, the thin films deposited at lower temperatures showed evidence of higher crystal quality than the above Tg deposited films because of a smaller d-spacing. A decrease in the full width half max of the X-ray diffraction peak was attributed to a large increase in the crystallite size, larger for the films deposited at higher temperatures as a result of a greater degree of crystallinity present in those films asdeposited. Further, comparisons are made between the as-deposited and post-deposition annealed samples in terms of stress, crystalline disorder and crystallite size. In addition, from differential scanning calorimetry measurements, the glass transition temperature of poly (chloro-p-xylylene) was 358C–368C and 448C at heating rates of 0.28C/min and 58C/min.
Посилання на статтю:
Morphology of poly(chloro-p-xylylene) CVD thin films / Jay J. Senkevich, Seshu B. Desu // Polymer. – 1999. – N 40. – P. 5751–5759.