Effects of coating cycles on spin-coated indium nitride thin films

Indium nitride (InN) thin films were prepared on aluminium nitride/p-silicon (111) substrates via sol-gel spin coating followed by nitridation. The InN thin films deposited at different coating cycles (10, 20 and 30) were analysed, and the growth mechanism was discussed in depth. The film thickness was enhanced with increasing number of coating cycle. X-ray diffraction showed that the crystalline structure of InN was improved at 20 coating cycles and started to degrade at 30 cycles. The diffusion path of the active nitrogen atoms into the deeper film was limited by the low growth temperature and led to gradual surface saturation. The film deposited at 20 cycles showed densely packed InN grains. Through the proposed approach, an InN optical band gap of 1.71 eV was achieved. It can be deduced that the variation in the number of coating cycles has significantly affected the film properties.