| Layared delafossite oxide CuCrO2 with wide band(3.2 eV)features dense Cu layers and edge-sharing octahedral CrO6 layers alternately stacking along the c axis,which presents intrinsic P-type conductivity and large resistivity anisotropy.CuCrO2 has large application potential owing to the large enhancement of conductivity by Mg2+ doping,while the doping mechanism needs further research especially the doping effects on the anisotropy.In this thesis,the preparation of CuCr1-xMgxO2(x=0～0.08)polycrystalline bulks and Mg doping effects were more systematically studied.CuCr1-xMgxO2(x=0～0.08)thin films were grown on flat and tilted a-Al2O3(0001)substrates under the optimized process,the interface crystallographic relationship between c-axis oriented films and substrated were characterized,the LIV signals in tilted films were measured and discussed the Mg doping effects on the resisticity anisotropy pc/pab.CuCri.xMgxO2(x=0～0.08)polycrystalline bulks were prepared by conventional solid state reaction method with the optimized sintering process of 1100℃ for 12h.When x≤0.03,The doped Mg mainly substituted Cr sites in the octahedral CrO6 layers and existed as the solid solution phase in CuCrO2 lattice.With the increasing of Mg doping,the carrier concentration increased,resulting in a increasing conductivity which reached its peak value of 12.24 S cm-1 when x=0.03,this value was 3-4 orders of magnitude larger than the undoped CuCrO2;When x>0.03,spinal phase MgCr2O4 gradually emerged.The linear fitting results of p-T curve at 200-300 K indicated the thermal activation mode was well fitted.With the increasing of Mg doping,thermal activation energy decrease and the minimum thermal activation energy Ea=0.031 eV was obtained when x=0.03.The linear results of seebeck coefficient indicated that when x<0.03,with the increasing of Mg doping,the seebeck coefficient decreased at the whole measuring temperature range(300K-1000K).When x>0.03,with the increasing of Mg doping,the Seebeck coefficient of polycrystalline bulks change little.So the maximum solid solution of Mg doping is 0.03.The change of conductivity and seebeck coefficient is related to carrier concentration of Cr3+ to Cr4+.The optimized PLD process:deposition temperature 730℃/flowing oxygenpressure 1 Pa/laser energy 300 mJ/frequency 4 Hz for deposition and annealing temperature 730℃/static oxygen pressure 2000Pa/annealing duration 20min for annealing were utilized to grow CuCr1-xMgxO2(x=0～0.08)films on planar and tilted α-Al2O3(0001).All the films were c-axis oriented,and the epitaxy of films decreased with the increasing substrats tilted angle;With the increasing of Mg doping,the angle discrepancy between film and substrate decreased and the epitaxy of films decreased under the same tilted angle.This may be related to the decrease of apparent activation energy Q and the increase of grain with the increasing of Mg doping.The linear results of ρ-T curve indicated resistance decrease with temperature increase.Those present semiconductor behaviors.The room temperature resistance decrease with the increasing of Mg doping,and when x=0.08 the lowest resistance is 0.19 Ωcm.The LIV response of CuCrO2(0≤x≤0.08)/Al2O3(0001)15°film while the laser energy density is 80mJ/cm2 increase with the increasing of Mg doping and the peak value of Up=45mV when x=0.08.The peak value of CuCr0.92Mg0.08O2/Al2O3(0001)5°,10°,15°film while the laser energy density is 80mJ/cm2 have linear relation with sin(2θ).The peak value of CuCr0.92Mg0.08O2/Al2O3(0001)10° film increase with increase of the laser energy density.The Mg doped thin films had a larger ρc/ρab,approximate in the insulator were △ρ/ρ～△S/S,High ρc/ρab corresponding to high △S,and LIV signal peak Up was proportional to △S.Therefore,CuCr0.98Mg0.08O2 thin film had larger peak voltage Up. |
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