In‐situ observation of AlN formation from Ni‐Al solution using an electromagnetic levitation technique

Abstract

Aluminum nitride is a promising substrate material for AlGaN-based UV-LED. In order to develop a robust growth processing route for AlN single crystals, fundamental studies of solution growth experiments using Ni-Al alloy melts as a new solution system were performed. Al can be stably kept in solution the Ni-Al liquid even at high temperature; in addition, the driving force of the AlN formation reaction from solution can be controlled by solution composition and temperature. To investigate AlN crystal growth behavior we developed an in situ observation system using an electromagnetic levitation technique. AlN formation behavior, including nucleation and growth, was quantitatively analyzed by an image processing pipeline. The nucleation rate of AlN decreased with increasing growth temperature and decreasing aluminum composition. In addition, hexagonal c-axis oriented AlN crystal successfully grew on the levitated Ni-40 mol%Al droplet reacted at low driving force (1960 K), on the other hand, AlN crystal with dendritic morphology appeared on the sample with higher driving force (Ni-50 mol%Al, 1960 K). Thus, the nucleation rate and crystal morphology were dominated by the driving force of the AlN formation reaction. K E Y W O R D S aluminum nitride, crystal growth, nucleation, thermodynamicsThis is an open access article under the terms of the Creat ive Commo ns Attri bution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. How to cite this article: Adachi M, Hamaya S, Yamagata Y, et al. In-situ observation of AlN formation from Ni-Al solution using an electromagnetic levitation technique. J Am Ceram Soc.

Containerless metal single-crystal growth via electromagnetic levitation

“…Adachi et al developed an in-situ observation technique for the AlN formation from a Ni-Al solution using EML. [32] Their high-speed camera was able to capture the dynamics of grain growth resulting in beautiful images. The only, to our knowledge, examples of EML undercooled solidification resulting in single-crystals are the works by Jian et al [33] and Kuribayashi et al [34] They managed to produce 5 mm spherical silicon crystals without a seed for an undercooling region from 5 to 55 K. [33] However, the quality leaves much to be desired, as they describe their result as a "quasi-single crystal with a large grain, except for a small area where twinning and cracking are observed".…”

Composition Dependence of Normal Spectral Emissivity of Liquid Ni–Al Alloys

“…Al could be stably maintained in the Ni-Al solution even at high temperatures; therefore, the moderate driving force of the AlN formation reaction could be controlled by choosing the chemical composition of the solution and growth tempertaure. 1) To design the solution growth technique for AlN, the thermophysical properties of the liquid Ni-Al alloys are needed. In previous work, our group developed a high-temperature thermophysical property measurement system called PROSPECT, [2][3][4][5][6] which uses electromagnetic levitation with a static magnetic field.…”