Epitaxial growth of single-crystalline AlN films on tungsten substrates

The authors have grown single-crystalline AlN(0001) films on W(110) substrates with an in-plane alignment AlN[11–20]‖W[001] at temperatures ranging from 450to600°C by pulsed laser deposition. These AlN films have a clear sixfold symmetry without 30° rotational domains. When AlN films are grown at 450°C, the interfacial reaction between AlN and W(110) is fully suppressed and a flat surface with a root-mean-square value as low as 0.20nm for AlN films is obtained. These single-crystalline AlN films grown on W(110) open a good opportunity for the high performance film bulk acoustic wave resonators of the next generation.