Low temperature deposition of high quality single crystalline AlN thin films on sapphire using highly oriented monolayer MoS₂ as a buffer layer

AlN films are commonly deposited on sapphire substrates. However, the growth process usually requires high temperature and multi-steps to improve the film quality, due to the large lattice mismatch between the film and substrate. Here we demonstrate that using monolayer MoS₂ grown on sapphire as a template, single crystalline AlN films with high crystallinity can be obtained at a much lower growth temperature using helicon sputtering system. The x-ray rocking curve of AlN films prepared on MoS₂/sapphire template at 400 °C shows a full width at half maximum of 0.050°, showing a dramatic reduction compared to that of 0.803° for those grown directly on sapphire substrate. The estimated dislocation density of AlN on MoS₂/sapphire is decreased to 7.7x10⁷ cm⁻², which is comparable to that prepared by metal-organic chemical vapor deposition at high temperatures. The small lattice mismatch between MoS₂ and AlN, as well as the polar crystal of monolayer MoS₂ apparently improve the quality of AlN films and facilitate AlN formed at lower temperature.