Reduced Etch Pit Density of Rutile (TiO₂) Single Crystals by Growth Using a Tilting-Mirror-Type Infrared Heating Image Furnace

Rutile single crystals were grown by the floating zone (FZ) method using a tilting-mirror-type image furnace. The tilting angle (theta) of the mirrors during the growth was changed from 0 to 10 and 20 degrees to examine the effects of theta on crystal quality. The etch pit density (EPD) at the center of the crystals was low compared with that at the periphery. The EPDs at the periphery and center of the crystals grown at theta = 0 degrees were (11-16) x 10(4) and 5 x 10(4) cm(-2) respectively. Both values significantly decreased with an increase in theta. In the crystal grown at theta = 20 degrees the EPDs at the periphery and center were 7.9 x 10(4) and 1.5 x 10(4) cm(-2) respectively. In particular at the center of crystals the EPD for theta = 20 degrees was 30% of that for theta = 0 degrees. This result suggests that the quality of rutile crystals can be improved by tilting the focusing mirrors used in crystal growth.