Rectangular vacancy island formation and self-depletion in Czochralski-grown PbMoO 4 single crystal during heat treatment

Abstract

Single crystal samples of PbMoO 4 with a 〈100〉 orientation have been investigated by DTA, chemical etching, and thermal treatments at 950°C for various annealing times. Surface morphologies of chemically and thermally etched {;100}; surfaces have been studied in detail in respect of microstructure, etch pit dimension, defect type and density. It is found that both chemical and thermal etching techniques reveal a similar radial defect-distribution pattern on the {;100}; surfaces while DTA shows a small compositional variation along the radial and axial directions. The correlation between two types of etch pits has been addressed. For thermally etched samples, a kinetic study on the rectangular vacancy island (thermal etch pit) formation and self-depletion has been presented. Based on the current work, the formation rate of the vacancy islands can be expressed as D 2 x − D 2 0 = k 0t 1.32 exp( − E a RT ) . Mechanisms regarding the vacancy island formation and self-depletion upon the heat treatment have also been proposed. The current study on the post-growth heat treatment has also identified key processing parameters to improve overall crystal quality.