Photobleaching process in polysilane films

• Published in: Japanese Journal of Applied Physics 1996-07, Vol.35 (7), p.4096-4100
• Main Authors: HAYASHI, H, KURANDO, T, OKA, K, DOHMARU, T, NAKAYAMA, Y
• Format: Article
• Language: English
• Subjects: Applied sciences; Exact sciences and technology; Organic polymers; Physicochemistry of polymers; Properties and characterization; Structure, morphology and analysis
• ISSN: 0021-4922; 1347-4065
• DOI: 10.1143/jjap.35.4096

The thermally assisted photoscission model has been formulated to explain the photobleaching of polysilane films due to the photoinduced annihilation of σ bonds. In the model, σ bonds are photoexcited and then scissored with thermal assistance, and the photobleaching by means of a prolonged exposure to ultraviolet light leads to the formation of a sponge-like structure. The model predicts that (i) the decay of the photon flux absorbed in the films after t T , defined as the time when the transmittance of the films begins to increase significantly, obeys a power law with an exponent of γ= k T / ε 0 , where ε 0 is the exponential width of the activation-energy distribution and k T is the thermal energy; (ii) t T is inversely proportional to the incident photon flux and obeys a power law against the film thickness with an exponent of 1/γ; and (iii) the temperature dependence of t T provides the cross section of the photoexcitation of σ bonds C r . It has been confirmed that these predictions are fairly consistent with the experimental results. The parameters of ε 0 and C r for the photobleaching of poly(methylphenylsilane) films by 325 nm light have also been estimated to be 28 meV and 1.1×10 -16 cm 2 , respectively.