Epitaxial growth of AlN films on c-sapphire using a multilayer structure has been investigated by metalorganic chemical vapor deposition adopting multiple alternation cycles of low-and high-temperature (LT-HT) growth. It is found that the surface morphology and crystal quality can be greatly improved using three alternation cycles with X-ray diffraction ω-scan full width at half maximum values of 311 and 548 arcsec for the (0002) and (10−12) peaks, respectively, which are induced by the alternation of the three-dimensional (3D) and two-dimensional (2D) growth modes caused by the LT-HT process. The first 3D-2D cycle is found to play a major role in threading dislocation reduction, while the second and third cycles mainly account for tensile stress relaxation. CrystEngCommThis journal is

Growth behaviors of AlN on hexagonal configuration hole-type and truncated-cone-pillar-type nano-patterned sapphire substrates (NPSSs) have been investigated.

In this paper the Rayleigh-Taylor instability (RTI) along the density interfaces of gravity-current fronts is analyzed. Both the location and the spanwise wavenumber of the most unstable mode determined by the local dispersion relation agree with those of the strongest perturbation obtained from numerical simulations, suggesting that the original formation mechanism of lobes and clefts at the current front is RTI. Furthermore, the predictions of the semi-infinite RTI model, i.e. the original dominating spanwise wavenumber of the Boussinesq current substantially depends on the Prandtl number and has a 1/3 scaling law with the Grashof number, are confirmed by the three-dimensional numerical simulations.