Properties of YMnO3 Self-assembled Nanocrystalline Prisms on GaN*

The high-temperature (850 $^{\circ}$C) molecular beam epitaxy deposition of YMnO$_{3}$ on HVPE GaN(0001) resulted in the spontaneous formation of YMnO$_{3}$ nanoprism structures due to Stranski-Krastanow growth mode. Their dimensions ranged from 20 nm to 60 nm in thickness and 50 nm to 500 nm in lateral size. The local dielectric properties of the sample were investigated using scanning surface potential microscopy (SSPM). Remanent hysteresis loops were used to compare the switching properties of the nanoprisms and underlying film. A larger remanence was observed for the prisms, most probably due to the lack of surrounding film areas that would clamp the ferroelectric response. As a result, the remanent polarization increased roughly linearly with increasing prism surface area.