Magneto transport in Bismuth films with helical defects

Bi, a semimetal in which magneto transport has been extensively studied in thin films and electron localization effects has been reported. Here in this thesis we have probed magneto transport in 300nm thick bismuth thin films with helical defects in the temperature range 1.5K to 20K. The dielectric helical defects were prepared by using a glancing angle vapour deposition technique. The films had a large classical magnetoresistance along with a contribution at the lowest temperatures from WAL (Weak Anti Localization) effects. The magnetoresistance was higher with the film oriented parallel to the magnetic field as compared to when it was oriented perpendicular to magnetic field. This was in contrast to the pristine bismuth film where no WAL was observed and the magnitude of the magnetoresistance was found to be similar for both orientations of the film with respect to the magnetic field. Electrical noise measurements serve as a unique tool for providing information about the dynamics of the solid state system. Noise measurements in case of bismuth films with helical defects showed a large increase in conductance fluctuations around 0.2T (which is the characteristic magnetic scale for WAL in these films) which was not observed in the pristine bismuth film