Morphology and etch figures of a Yb:YAl3(BO3)4crystal

Abstract

Yb:YAl3(BO3)4is a good self-frequency-doubling crystal with the point group 32. In this paper, atomic force microscopy (AFM) has been used to observe the etch figures of the three forms (positive trigonal prism {11\overline 20}, negative trigonal prism {2\overline 1\overline 10} and rhombohedron {10\overline 11}) on the crystal morphology of Yb:YAl3(BO3)4. The etch figures display the point group 32 of the Yb:YAl3(BO3)4crystal. To compare the morphology and etch figures of Yb:YAl3(BO3)4with those of quartz, the classic crystal of point group 32, the etch figures of the three forms (hexagonal prism {10\overline 10}, positive rhombohedron {10\overline 11} and negative rhombohedron {01\overline 11}) on quartz were also observed using AFM. It is interesting that Yb:YAl3(BO3)4develops two prismatic forms (related by a positive–negative relationship) and one rhombohedral form, while quartz develops one prismatic form and two rhombohedral forms (also related by a positive–negative relationship). Etch figures of faces or sections with the same indices (or the same crystallographic orientations) in Yb:YAl3(BO3)4and quartz are very similar, although their crystal structures are very different. Besides diffraction methods, etch figures are a useful method for determining the point group of a crystal.