Low-energy Electron Microscopy (LEEM) Imaging and Diffraction of Ho$_{1-x}$Y$_{x}$MnO$_{3}$(0001)

We have investigated the (0001) surfaces of several hexagonal perovskite alloys Ho$_{1-x}$Y$_{x}$MnO$_{3}$ (x=0-1), by low-energy electron microscopy (LEEM) using both mirror-mode imaging and diffraction (LEED) techniques. We find LEEM structured domains for our (0001) surfaces of single crystals grown by a traveling-solvent-floating zone technique which are likely due to work function variations on a scale of $\sim $100 nm to 5 $\mu $m. The domains are visible up from 500\r{ }C to $\sim $900\r{ }C, giving possible evidence for the expected 180\r{ } ferroelectric domain structure below and above the Curie temperature of $\sim $630 \r{ }C. The domain contrast in LEEM was lower upon cooling and we are exploring several mechanisms for this result. In addition, we observed LEED patterns from $\sim $24 to 1100\r{ }C, with electron energies in the range of 15eV to 50eV. Above 500\r{ }C, 1$\times $1 and 2$\times $2 patterns were obtained for all samples with the sharpest LEED contrast near T $\sim $1000\r{ }C. In some cases a 2$\times $4 surface reconstruction was also evident but with less consistent order. The 2-D lattice constant parameters in (0001) plane are consistent with previous literature values for pure YMnO$_{3}$ (see: Aberdam \textit{et al., Surface Science }\textbf{14, }pp.121-140 (1969)).