Structure and surface morphology of MnF2 epitaxial layers grown on grooved and ridged CaF2 (110) surface

摘要

Structural and surface morphology studies of MnF2 epitaxial layers have been performed by x-ray diffraction and atomic force microscopy (AFM). MnF2 layers of different thicknesses (0.12-1.25 mu m) were grown by MBE on Si( 0 0 1) substrates with the deposited CaF2-buffer layer having a < 1 1 0 > orientation and a grooved and ridged surface. X-ray diffraction patterns in the 10 degrees-60 degrees angular range have been measured. Profiles of diffraction peaks in two directions-parallel and normal to the diffraction vector-as well as the intensity distribution around 2 2 0 reciprocal lattice points were obtained. It was found that the metastable orthorhombic phase of alpha-PbO2 type with [ 1 1 0] growth direction dominates in the films; a much smaller portion of the stable rutile type phase was also detected, though it increases with the film thickness. As follows from the x-ray diffraction data, the films have a mosaic block structure. Parameters of the crystallites were determined using the Williamson-Hall analysis of angular width of the diffraction peaks. It was obtained that the crystallites of the orthorhombic phase have an elongated shape oriented along the direction of the CaF2 ridges. The AFM study confirms a regular distribution of the orthorhombic crystallites and shows the appearance of some irregular shaped crystallites on the top of the thick MnF2 films.