Development of Nanosecond Laser Photolysis Apparatus for Ultrathin Polymer Films

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Much attention is being payd to photofunctional thin polymer films. The films have already been used in photoresist, photomemory device, organic photoconductor, thin film for optical components, etc., and they are expected to be the key material of micro devices in the next generation. For the development of novel photofunctional polymer films, photophysical processes and the photochemical intermediates have to be examined in these thin polymer films and the direct observation of these processes is desirable. In this project, a laser photolysis apparatus to study the photo-processes in photofunctional thin polymer films was developed.According to the Lambert-Beer law, the transient absorbance is obtained by the product of molar extinction coefficient, the concentration, and the optical path length. The transient absorption measurements for polymer thin films were difficult due to the short optical path length of the sample films. Therefore, a new multipass sample cell was designed for the measurements of these thin films. This multipass cell improved the system sensitivity almost one order of mugnitude.The main features of the laser photolysis apparatus developed in this research are as follows.1. Wide range of wavelength from 160 nm to 2600 nm.2. Time resolution of 3 ns in UV and visible regions, and of 500 ns in near IR region.3. Easy and accurate transient absorption measurement for thin polymer films.4. The limiting film thickness to measure the transient absorption spectrum was 24 nm.5. Emission decays as well as transient absorption can be measured by changing the optical alignment.6. The operation and data analysis can be controlled and processed by a computer.