Magnetotransport Properties of Semi-Metallic Bismuth Thin Films for Flexible Sensor Applications

In this paper we describe characterization of semi-metallic bismuth thin films. We prepared bismuth thin films by a deposition of bismuth through thermal evaporation onto flexible Kapton substrates and annealing at temperatures close to the melting point of Bi. We studied the morphology and transport properties of these films. Immediately after the deposition we observed competition between vanishing of the grain boundaries and elastic strain energy, which stabilized at larger thicknesses leading to the grain size of 140 nm. This effect was accompanied by a continuous decrease of resistivity which, however, was larger than for the bulk bismuth. The film annealing at temperatures close to the melting point of Bi led to a 300% increase of magnetoresistance at room temperature and in the magnetic field of 7 T. The in situ resistance measurements allowed us to determine the permissible temperature at which the annealing does not cause the loss of film continuity.