Quantum size phenomena in single-crystalline bismuth nanostructures

Size-dependent quantization of energy spectrum of conducting electrons in solids leads to oscillating dependence of electronic properties on corresponding dimension(s). In conventional metals with typical energy Fermi E F ~ 1 eV and the charge carrier's effective masses m* of the order of free electron mass m 0, the quantum size phenomena provide noticeable impact only at nanometer scales. Here we experimentally demonstrate that in single-crystalline semimetal bismuth nanostructures the electronic conductivity non-monotonously decreases with reduction of the effective diameter. In samples grown along the particular crystallographic orientation the electronic conductivity abruptly increases at scales of about 50 nm due to metal-to-insulator transition mediated by the quantum confinement effect. The experimental findings are in reasonable agreement with theory predictions. The quantum-size phenomena should be taken into consideration to optimize operation of the next generation of ultra-small quantum nanoelectronic circuits. Upon dimension reduction classic physics tends to degenerate into quantum. In metals the size quantization shows an impact on all electronic properties including conductivity. Now a team led by Prof. K. Arutyunov from Moscow Institute of Electronics and Mathematics and Kapitza Institute for Physical Problems RAS in Russia demonstrates that in single crystalline semimetal bismuth nanorods the resistivity increases in a pronounced manner when the size is below a certain value. Specifically, for samples grown along the particular crystallographic orientation, corresponding to the lowest effective electron mass in bismuth, the electronic conductivity increases abruptly at scales of around 50 nm. These experimental findings are due to metal-to-insulator transition mediated by the quantum confinement and are in reasonable agreement with the theoretical predictions. The revealed phenomena should be taken in consideration in optimizing the next generation of quantum nanoelectronic circuits.