Preparation and Properties of Sapphire by Edge-defined Film-fed Growth (EFG) Method with Different Growth Directions

Abstract

Sapphire, belonging to hexagonal crystal system, is typically anisotropic which makes it direction-sensitive. To research the effects of growth directions on properties of sapphire, c-[0001] seed (c-sapphire) and a-[11-20] seed (a-sapphire) were used to prepare sapphire by edge-defined film-fed growth (EFG) method. The samples were analyzed through lattice integrity, dislocation and corrosion performance by double-crystal XRD, OM, AFM, SEM and EDX. It was shown that the lattice integrities of two growth-direction crystals were both well due to the small FWHM values. While the average densities of dislocation in c-sapphire and a-sapphire were 9.2×103 and 3.9×103 cm-2 respectively, the energy of dislocation in c-sapphire was lower than that in a-sapphire. During Strong Phosphoric Acid (SPA) etching, the surface of c-sapphire basically kept smooth but in a-sapphire there were many point-like corrosion pits where aluminum and oxygen atoms lost by 2:1. Our work means that it will be promising for growing c-[0001] seed sapphire by EFG if aided by parameter optimization.