Abstract
Surface recovery of germanium substrate for infrared spectroscopic studies of Langmuir-Blodgett (LB) films has been investigated by infrared multiple-angle incidence resolution spectroscopy (MAIRS). A Gesubstrate is, in general, repeatedly used for fabrication of LB films for infrared spectroscopic studies. For the recycling process, the substrate covered by LB films is washed by sonication in organic solvents and pure water. This cleaning generally works well for ordinary analytical use, especially for thick samples, such as polymer and liquid materials. Nonetheless, in the present study, the cleaning by sonication only has been found to be inappropriate for the measurements of monolayer-level samples. The infrared MAIRS analysis has revealed that the 5-monolayer cadmium stearate LB film deposited on a fresh Ge substrate has a molecular tilt angle of ca. 13° from the surface normal, while that deposited on a recycled substrate by sonication has an angle of ca. 30°. Infrared MAIRS analysis has experimentally proved that the ideal recovery of the Ge surface can be achieved by cleaning the substrate with chemical rinse with the use of acid solution.
