Nanoporous, micron-size GaN particles with pores between 40 and 100 nm in diameter have been synthesized on boron nitride (BN) substrates using chemical vapor deposition (CVD) techniques. The synthesis process is based on the direct reaction of gallium atoms and ammonia molecules without the presence of intentional metal catalysts. Scanning electron micrographs reveal the formation of GaN nanoporous morphologies ranging from micron-size particles with hexagonal
pyramidal prismatic shape to hexagonal platelets. The nanopores are only observed on the (0001) basal plane and aligned orderly along the  crystallographic direction. High-Resolution Transmission Electron Microscopy (HRTEM) confirms that the nanoporous particles are, where analyzed, wurtzite GaN single crystal.
Physical vapor transport (PVT) growth of mm-size, polycrystalline ZnO has been demonstrated at temperatures exceeding 1600°C under air at atmospheric pressure. Scanning electron microscopy (SEM) analysis revealed the growth of grains and microcrystals with strong faceted morphologies suggesting near-equilibrium growth conditions. In addition, a temperature-dependent formula for the O<sub>2</sub> sticking coefficient has been developed to predict the maximum growth rate of PVT ZnO. Combining this formula with an existing one-dimensional analytical model for PVT growth of bulk AlN, the value of the growth rate of PVT ZnO as a function of temperature and oxygen vapor partial pressure has been studied. This analysis predicts that growth rates in the order of 1mm/h could be theoretically achieved using the PVT method under non-stoichiometric oxygen-rich vapor pressures and temperatures exceeding 1600°C.