Gallium nitride (GaN) films grown on sapphire substrates were successfully separated and transferred onto silicon (Si) substrates using the laser lift-off (LLO) process induced by an excimer pulsed laser. The structural and optical properties of the GaN films before and after LLO were characterized by x-ray diffraction, atomic force microscopy and Raman spectroscopy. The influences of the laser scanning speed on the structural and optical properties of thin GaN films before and after LLO have been studied, which demonstrated that the laser scanning speed alters the structural quality of the GaN films. The results show that the quality of GaN films is dependent on the LLO process parameter.

The labial groove-textures of upper central incisors were defined and explored to imitate the elaborate groove-textures for aesthetic restorations. In the current study, 158 upper central incisors were selected from 79 volunteers aged from 19 to 24 and recruited from Sichuan University in Chengdu of China. The length, width, depth, combination and distribution of the horizontal and vertical grooves on the labial surface were investigated by an optical measurement method, based on the Shadow Moiré technology and Temporal Fourier analysis. Vertical grooves were confirmed to be present in 94% of the samples and horizontal grooves in 77%. Perfect symmetry was shown in the vertical grooves of the same tooth, as well as in the homonymous teeth. The majority of horizontal grooves were distributed in the proximity of the cervical fourth and the middle of the crown. Based on the combination and distribution of the grooves, eight basic labial groove-texture types of maxillary central incisors were classified. The subtle morphological characters of natural teeth could be recorded by the new method, and it could also provide the minute groove-texture for dentists and technicians to achieve an aesthetic appearance for a restoration.