Magnetoquantum oscillations and confinement effects in arrays of 270-nm-diameter bismuth nanowires

Abstract

We present a study of the electrical transport properties of 270-nm-diameter bismuth nanowire arrays embedded in an alumina matrix which are capped with layers of bulk Bi to produce a very low contact resistance. The resistance of the Bi nanowires has been measured over a wide range of temperatures (1.8--300 K) and magnetic fields (-8--8 T) for the longitudinal and transverse orientation. At low magnetic fields, the longitudinal magnetoresistance exhibits field-periodic modulations whose periods are consistent with theoretical predictions for the Aharonov-Bohm ``whispering gallery'' modes of electrons with long mean free path. At high magnetic fields, as the carrier cyclotron radius becomes smaller than the wire diameter, we observe Shubnikov--de Haas oscillations associated with both holes and electrons. These represent a detailed study of magnetoquantum oscillations in high-density nanowire arrays. Overall, the hole periods are increased by 5% and the carrier density is decreased by 13% from the values for bulk Bi, which is consistent with recent theoretical estimates of the effect of confinement on the carrier's Fermi surface.