Step Evolution and Growth Rate on {101} Faces of Potassium Dihydrogen Phosphate Crystals Grown at High Supersaturation

Abstract

The surface micromorphology of the {101} faces of potassium dihydrogen phosphate (KDP) crystals grown at different supersaturation conditions is systematically compared using atomic force microscopy. The height and width of the crystals during different growth steps are measured. The pyramidal face growth rate of KDP crystals is tested by a laser polarization interference system. The X-ray rocking curve is used to measure the structural perfection of the {101} face of the KDP crystals. The results show that the growth rate of the {101} face increases with the supersaturation degree, and the rate is faster than that of the {100} face at a low supersaturation degree. Step bunching first increases and then decreases upon increasing the supersaturation, and the step height reaches a maximum value of about 6.0-6.9 nm at 𝝈 = 0.08 and 0.09. The crystal structural perfection is the worst under these conditions. It should be noted that 2D nuclei form on the surface terraces when the supersaturation is about 0.07. Dendrite-like steps may be formed due to the development of these 2D nuclei. This work provides a reference for further researching the step evolution law of other crystalline materials.

In situ Observation of the Growth of KDP Crystal (101) Faces Doped by Na3(PO3)3

“…Potassium dihydrogen phosphate (KH 2 PO 4 , KDP) crystals are an excellent nonlinear optical material used as electro-optic switches and frequency converters in high-power output laser systems such as Inertial Confinement Fusion (ICF) due to their wide transparency, large electro-optical coefficient, low half-wave voltage, and good optical homogeneity. − Research shows that small amounts of impurities coming from raw materials or water may enter the growth lattice, making a significant impact on the growth and quality of KDP. − Particularly, high-valence metal ions, such as Fe 3+ , Cr 3+ , and Al 3+ are liable to enter the prismatic sectors on account of the electrostatic interactions, leading to lattice distortion or structural defects, which affect the stability of solution , and reduce the optical quality of crystals. − Currently, most of the studies have focused on the impact of impurities on (100) faces, while relatively few studies have concentrated on the effects of impurities on (101) faces. (101) faces of KDP crystals are easily influenced by anions due to positive electrical properties .…”