REFLECTION HIGH-ENERGY ELECTRON-DIFFRACTION STUDY OF THE GROWTH OF NIO AND COO THIN-FILMS BY MOLECULAR-BEAM EPITAXY

NiO thin films have been prepared under UHV conditions by metal evapor ation on both ex-situ and in-situ cleaved MgO(100) using O-2 and NO2 a s oxidants. Changes in the film morphology are monitored with reflecti on high-energy electron diffraction (RHEED). While it is possible to g row films epitaxially using O-2, we find films grown using NO2 to be o f superior quality, Using NO2 as an oxidant, films synthesized between 200 and 450 degrees C grow layer by layer, while an increase in surfa ce disorder is observed in films grown below 200 degrees C. Pronounced RHEED intensity oscillations are observed for 200<T<450 degrees C, al lowing for the measurement of film thickness. We also observe RHEED in tensity oscillations at room temperature when NiO thin films grown at high temperatures are used as a substrate. The general form of the osc illations and associated changes in the RHEED pattern (and thus surfac e morphology) are markedly different at this low temperature We also r eport results of CoO epitaxial growth on MgO(100) using NO2 as an oxid ant.