Density functional theory calculations of photoabsorption spectra of organic molecules in the vacuum ultraviolet region

Time-dependent density functional theory (TD-DFT) calculations using the B3LYP hybrid functional were performed to investigate the transparencies of organic molecules in the vacuum ultraviolet (VUV) region. The calculated absorption spectra obtained from the combination of geometry optimization using the 6-311G(d) basis set and subsequent calculation of transition energies and oscillator strengths using the 6-311++G(d, p) basis set without empirical corrections agree well with the observed spectra reported by Brodsky et al. [J. Vac. Sci. & Technol. B 18 (2000) 3396]. This method is helpful to infer transparency of molecules in the VUV region and in particular useful for design of photoresist materials for F-2 lithography (157 nm).