Fabrication of PbTiO3 Nanocrystals on Atomically Flat Sapphire Substrates by RF Magnetron Sputtering

Abstract

Recently, there has been great interest in nanosized ferroelectric materials because of the need to produce higher capacity ferroelectric memory devices. Since the characteristics of these memory devices are affected by the dielectric behavior in nanoregions, it is important to produce nanocrystals that are highly uniform both in terms of size and quality. Nanocrystals have been prepared by bottom-up methods, such as initial growth nucleation; however, it is difficult to control growth position and crystal size in these methods. In this study, lead titanate (PbTiO 3 ) nanocrystals were prepared on atomically flat sapphire substrates at a very low deposition rate in order to achieve position and size control. Atomically flat surfaces of sapphire (0001) were formed by annealing at 1000°C and they had a step-terrace structure with a step height of 0.22 nm and a terrace width of 70 nm. A shield plate for reducing the deposition rate was placed in front of the substrate during sputtering. Nanocrystals with a uniform size of about 30 nm were successfully grown on the step-edge of the surface, demonstrating that it is possible to fabricate well-ordered nanocrystal arrays using our shielding technique. The crystals obtained were evaluated by X-ray photoluminescence and Raman spectroscopy, and the results revealed that perovskite PbTiO 3 nanocrystals had been produced.