Experimental observation of ferromagnetism evolution in nanostructured semiconductor InN

Abstract

Recently, undoped semiconductors have been pushed to the frontiers of diluted magnetic semiconductors (DMSs) since no spurious ferromagnetism (FM) signal from metal segregation occurs. However, some aspects still remain untouched in undoped semiconductors nanostructures, including: 1) the evolution of spin moments during the fabrication process; 2) possible intrinsic relationship between the magnetic properties and morphological features, the latter being also dependent on formation process. In this article, we synthesized undoped InN nanostructures and observed a gradual magnetic transition from diamagnetic to FM, and an obvious morphology evolution from tube-shape to wire-shape products with the increase of nitridation time. It is speculated that increasing surface defects such as N vacancies in the morphology transition process are the intrinsic causes for the enhanced FM order with increase of nitridation time. The results provide some useful clues in understanding the true magnetic origin in nanostructured DMSs and reported properties inconsistencies in nanostructured materials.