electronic conductor

electronic conductor,Mariana I. Bertoni,Thomas O. Mason,Julia E. Medvedeva,Arthur J. Freeman

electronic conductor  
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A tunable conductivity has been achieved by controllable substitution of a novel UV light activated electronic conductor. The transparent conducting oxide system H-dope d Ca 12-xMg xAl 14 O33 (x = 0; 0.1; 0.3; 0.5; 0.8; 1.0) presents a conductivity that is strongly dependent on the substitution level and temperature. Four-point dc-conductivity decreases w ith x from 0.26 S/cm (x = 0) to 0.106 S/cm (x = 1) at room temperature. At each composition the conductivity increases (reversibly with temperature) until a decomposition te mperature is reached; above this value, the conductivity drops dramatically due to hydrogen rec ombination and loss. The observed conductivity behavior is consistent with the predictions of our first principles density functional calculations for the Mg-substituted system with x=0, 1 and 2. The Seebeck coefficient is essentially composition- and temperature-independe nt, the later suggesting the existence of an activated mobility associated with small polaron conduction. The optical gap measured remains constant near 2.6 eV while transparency increases with the s ubstitution level, concomitant with a decrease in carrier content.
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