Molecular alignment of nano-thin film using Raman spectroscopy

Molecular alignment of nano-thin liquid crystal 5CB film confined between highly polished steel ball and quartz disk under shear is studied using Raman spectroscopy. The results show that an acceptable signal-to-noise ratio as high as 20:1 can be obtained under certain experimental conditions. In addition, the intensity of the Raman spectrum reaches its peak (minimum) value when polarization of the laser is parallel (perpendicular) to the direction of shear motion. This indicates that the molecules of liquid crystal 5CB film are oriented along the direction of shear motion. Furthermore, the influence of shear speed on the intensity of Raman spectroscopy of nano-thin liquid crystal 5CB film was investigated, and its film thickness was analyzed based on a relative optical interference intensity technique.