Studies on dislocation etching kinetics of flux-grown YFeO 3 crystals

Abstract

Results of etching (110) and (001) planes of YFeO 3 crystals are presented and discussed in detail. It is shown that boiling H 3PO 4 or H 3PO 4+HNO 3 in the ratio of 1:1 is the dislocation etchant of YFeO 3 crystals. It is established that the latter etchant is best suited for both (110) and (001) planes insofar as the definition of pit and control over etching are concerned. The kinetics of etching are investigated by making a quantitative study of the etch rate at different temperatures and at different concentrations of H 3PO 4. Variations in areal extension and depth of pits with time in H 3PO 4 or H 3PO 4 mixed with HNO 3 are investigated. It is shown that the areal and vertical etch rates increase with increase in temperature on both (110) and (001) planes. Addition of HNO 3 to H 3PO 4 brings down the minimum temperature required for etching (110) and (001) planes. The velocities of dissolution parallel and perpendicular to the surface are measured. The activation energy responsible for the dislocation sites for dissolution parallel and perpendicular to (110) and (001) planes are estimated. The Arrhenius factors for areal ( A' A ) and vertical ( A D ) dissolution are A' A =1.44×10 9 and 3.99×10 7 μm/s, and A D =8.12×10 3 and 1.31×10 4 μm/s for (110) and (001) planes, respectively.