TY - JOUR
T1 - Tunable conductivity and conduction mechanism in an ultraviolet light activated electronic conductor
AU - Bertoni, Mariana I.
AU - Mason, Thomas O.
AU - Medvedeva, Julia E.
AU - Freeman, Arthur J.
AU - Poeppelmeier, Kenneth R.
AU - Delley, Bernard
N1 - Funding Information:
This work was supported by the MRSEC program of the National Science Foundation (Grant No. DMR-0076097) at the Materials Research Center at Northwestern University and by the DOE (Grant No. DE-FG02-88ER45372). M.I.B is supported by the U. S. Department of State through a Fulbright Scholarship. Computational resources have been provided by the DOE supported NERSC.
PY - 2005/5/15
Y1 - 2005/5/15
N2 - A tunable conductivity has been achieved by controllable substitution of an ultraviolet light activated electronic conductor. The transparent conducting oxide system H-doped Ca12-x Mgx Al14 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 with x from 0.26 Scm (x=0) to 0.106 Scm (x=1) at room temperature. At each composition the conductivity increases (reversibly with temperature) until a decomposition temperature is reached; above this value, the conductivity drops dramatically due to hydrogen recombination 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 independent, 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 substitution level, concomitant with a decrease in carrier content.
AB - A tunable conductivity has been achieved by controllable substitution of an ultraviolet light activated electronic conductor. The transparent conducting oxide system H-doped Ca12-x Mgx Al14 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 with x from 0.26 Scm (x=0) to 0.106 Scm (x=1) at room temperature. At each composition the conductivity increases (reversibly with temperature) until a decomposition temperature is reached; above this value, the conductivity drops dramatically due to hydrogen recombination 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 independent, 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 substitution level, concomitant with a decrease in carrier content.
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U2 - 10.1063/1.1899246
DO - 10.1063/1.1899246
M3 - Article
AN - SCOPUS:20944440832
VL - 97
JO - Journal of Applied Physics
JF - Journal of Applied Physics
SN - 0021-8979
IS - 10
M1 - 103713
ER -