The band gap energies EG of the lithium compounds have been measured by transmittance and reflectivity measurements as well as measurements of the diffuse reflectivity. At room temperature EG=2.83 eV (LiInSe2), EG=3.56 eV (LiInS2), EG=3.13 eV (LiGaSe2) and EG=3.62 eV (LiGaS2) have been obtained presupposing a direct interband transition. In a first attempt the birefringence of LiInS2 was studied by transmittance measurements. Using infrared and Raman spectroscopy the lattice vibrational properties have been investigated.

A measurement system for ion induced photon emission (IIPE) measurements has been established and optimized for maximum light collection and detection efficiency. This is achieved by a special imaging system and a liquid nitrogen cooled CCD camera as the detector. The performance of the imaging system has been evaluated by ray tracing calculations. In sputter depth profiling, which is the most important application of IIPE, the detection limit does not depend on the available primary ion current. Detection limits are strongly element dependent and reach about 1 ppm for alkali metals in depth profiling. Detection limits for bulk concentrations can be up to three orders of magnitude less than detection limits for depth profiling. Compared to previously published values a significant improvement has been achieved.