| Summary: | 碩士 === 國立中山大學 === 物理學系研究所 === 105 === Superlattices of ZnO/MoO3 have been prepared by atomic layer deposition (ALD) on a-oriented sapphire substrates at 177 oC. The electrical properties were studied via measurement of resistivity as a function of temperature (T) from T=15 K to 300 K and magnetic field (B). The superlattice structures comprise multiple periods of ZnO/MoO3 bilayers that are hoped to incur new physical properties not seen in their pristine form. Data analysis by brute-force data fitting based on thermally activated processes of band conduction resulted largely in four midgap states responsible for the measured functional dependence of resistivity on T and B. Except for the shallowest state that is at 5 meV from the band edge, the other three states consistently follow the linear relation of E(B)=E(0)-mB over the whole studied temperature range, hence demonstrate negative magnetoresistance. The shallowest state, follows a positive B-square dependence in revelation of a cyclotron effect for free carriers moving along a spiraling path. The countering magnetoresistive behaviors make the magnetoresistance exceedingly small and difficult to measure. Analysis of the charge carrier mobilities, according to the simple power law of temperature, suggest that impurity charge scattering and lattice vibration scattering mechanisms are both at play.
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