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

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.