4 research outputs found
Electrical transport studies of quench condensed Bi films at the initial stage of film growth: Structural transition and the possible formation of electron droplets
The electrical transport properties of amorphous Bi films prepared by
sequential quench deposition have been studied in situ. A
superconductor-insulator (S-I) transition was observed as the film was made
increasingly thicker, consistent with previous studies. Unexpected behavior was
found at the initial stage of film growth, a regime not explored in detail
prior to the present work. As the temperature was lowered, a positive
temperature coefficient of resistance (dR/dT > 0) emerged, with the resistance
reaching a minimum before the dR/dT became negative again. This behavior was
accompanied by a non-linear and asymmetric I-V characteristic. As the film
became thicker, conventional variable-range hopping (VRH) was recovered. We
attribute the observed crossover in the electrical transport properties to an
amorphous to granular structural transition. The positive dR/dT found in the
amorphous phase of Bi formed at the initial stage of film growth was
qualitatively explained by the formation of metallic droplets within the
electron glass.Comment: 7 pages, 6 figure
Germanium quantum well with two subbands occupied: kinetic properties
Multisubband transport of the p-type Si₀.₄Ge₀.₆/Ge/Si₀.₄Ge₀.₆ heterostructure has been investigated by means of magnetotransport measurements at low temperatures and high magnetic fields. Two frequency Shubnikov–de Haas oscillations indicate occupation of two subbands. This allows us to determine the densities and mobilities of the charge carriers on each subband. Shubnikov–de Haas oscillations reveal two 2D conduction subbands with carrier effective masses of 0.112m₀ and 0.131m₀. The quantum Hall ferromagnetic states which results from the crossing of two Landau levels with opposite spin and different subband was observed in SiGe systems for the first time