SdH oscillations in the contact resistance of bismuth nanowires

Measurements of the magnetoresistance of 30-nm diameter bismuth nanowires where the trigonal crystalline axis is parallel to the wire axis have been carried out for various angles between the nanowires axis and the magnetic field including the longitudinal and transverse orientation for magnetic fields up to 14 T. At high magnetic fields, as the carrierʹs cyclotron radius becomes smaller than the wire diameter, we observe Shubnikov-de Haas resonances from the quantization into Landau levels in the wire interior. The wires display a nearly isotropic short period of 0.025 T−1, consistent with a heavy carrier concentration of 1.5×1018 cm−3, a five-fold increase from the bulk value of 3.0×1017 cm−3. Dresselhausʹs theory of quantum confinement shows that Bi wires should change from semimetallic to semiconducting behavior for diameter smaller than a critical diameter of 50 nm, which is difficult to reconcile with the present measurements. Our results also discussed in terms of a surface-induced surface hole concentration that circumvent the semimetal-to-semiconductor transition, a model that has been introduced to explain transport measurements on thin Bi films.