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A3: High temperature materials

Thermoelectric performance of Al-doped ZnO thin films on SrTiO3 substrate at different deposition temperatures

S.Saini1,P.Mele1,H.Honda1,K.Matsumoto2,K.Miyazaki3,A.Ichinose4,L.Molina5,P.E.Hopkins6
1ISSD,Hiroshima Univ2D. of Mater. Sci. KIT3D. of Mech. Eng KIT,Japan4CRIEPI,Japan5 D. of Mater. & Geosci. Tech Univ of Darmstadt6D. of Mech. & Aerospace Eng, Univ of Virginia

We have prepared 2% Al doped ZnO (AZO) thin films on SrTiO3 substrates by Pulsed Laser Deposition (PLD) technique at various deposition temperatures (Tdep = 300⁰C, 400⁰C, 500⁰C, and 600⁰C). Deposition parameters such as pulse frequency (10 Hz), substrate-target distance about (35 mm) and rotation speed of the target (30% rpm) were kept unchanged during all the deposition routes. Electric conductivity (s) and Seebeck coefficient (S) were evaluated in the interval T = 300 - 600 K. s decreases with Tdep, while S is always negative, confirming n-type conduction, and its absolute value increases with Tdep. The best performance was obtained with thin film deposited at 300⁰C, which is fully c-axis oriented and presented columnar growth: s = 310 S/cm, S = -65 mV/K and power factor (S2s) = 0.13×10-3 Wm-1K-2 at 300 K. Its thermal conductivity (k) is 6.5 Wm-1K-1, 5 times lower than for the corresponding bulk material (34 Wm-1K-1). The figure of merit ZT = (S2s)T/k is 0.05 at 600 K, surpassing the performance of bulk material and all the other films. The value of ZT decreases with increase in deposition temperature.