Direct observation of the semimetal-to-semiconductor transition of individual single-crystalbismuth nanowires grown by on-film formation of nanowires

Abstract

We have systematically investigated the semimetal-to-semiconductor transition ofindividual single-crystalline Bi nanowires. For this work, we developed a technique toreduce the diameter of Bi nanowires grown by our unique on-film formation ofnanowires (OFF-ON) method. Cooling down the substrate temperature during Bifilm deposition by use of liquid nitrogen, film structures with small-sized grainswere obtained. Through thermal annealing of these fine-granular Bi films,single-crystalline Bi nanowires can be produced with minimum diameter of ∼ 20 nm. Elaborative nanofabrication techniques were employed to shape state-of-the-artfour-probe devices based on the individual small diameter Bi nanowires.Diameter-dependent transport measurements on the individual Bi nanowiresrevealed that the semimetal-to-semiconductor transition really occurred at aboutdw = 63 nm. Moreover, band structure calculations supported this occurrence of thesemimetal-to-semiconductor transition.