GROWTH MECHANISM OF WHISKERS AND NEEDLE CRYSTALS (PRISMS) OF ALUMINUM NITRIDE

Abstract

Whiskers and needle crystals (prisms) of aluminum nitride (AlN) prepared by the sublimation method were found to grow through the so-called VLS mechanism. Their growth direction coincides with the c-axis. The starting material of AlN was decomposed into aluminum vapor and nitrogen above 2000°C and they were dissolved into a molten agent such as iron. Whiskers and prisms of AlN grew from the molten agent saturated with aluminum and nitrogen between 1550°C and 1700°C. Consequently most of the whiskers and prisms of AlN prepared by the sublimation method were crowned with a globe of such an agent as iron on the top.
Iron, cobalt and manganese are effective agents for the VLS growth mechanism of whiskers and prisms of AlN. Iron is the most effective and typical among them.
In the case of the VLS growth mechanism of AlN, the growth in the direction perpendicular to the c-axis scarcely takes place even after the main growth in the parallel to the c-axis have sufficiently developed.