  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
EF~1 eV and the charge carrier's effective masses m* of the order of free
electron mass m0, 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.
