STUDIES ON DISLOCATION ETCHING KINETICS OF FLUX-GROWN YFEO3 CRYSTALS

Results of etching (110) and (001) planes of YFeO3 crystals are presen ted and discussed in detail. It is shown that boiling H3PO4 or H3PO4 HNO3 in the ratio of 1:1 is the dislocation etchant of YFeO3 crystals . It is established that the latter etchant is best suited for both (1 10) and (001) planes insofar as the definition of pit and control over etching are concerned. The kinetics of etching are investigated by ma king a quantitative study of the etch rate at different temperatures a nd at different concentrations of H3PO4. Variations in areal extension and depth of pits with time in H3PO4 or H3PO4 mixed with HNO3 are inv estigated. It is shown that the areal and vertical etch rates increase with increase in temperature on both (110) and (001) planes. Addition of HNO3 to H3PO4 brings down the minimum temperature required for etc hing (110) and (001) planes. The velocities of dissolution parallel an d perpendicular to the surface are measured. The activation energy res ponsible for the dislocation sites for dissolution parallel and perpen dicular to (110) and (001) planes are estimated. The Arrhenius factors for areal (A(A)') and vertical (A(D)) dissolution are A(A)' = 1.44 x 10(9) and 3.99 x 10(7) mum/s, and A(D) = 8.12 x 10(3) and 1.31 x 10(4) mum/s for (110) and (001) planes, respectively.