appred surface science ELJXVIER Applied Surface Science 96-98 (1996) 689-692 Giant laser-induced voltages at room temperature in Pr doped Y-Ba-Cu-0 thin films H.-U. Habermeier *, N. Jisrawi, G. J@er-Waldau zyxwvutsrqponmlkjihgfedcbaZYXWV Max-Planck-hstitut FKF, Heisenbergsw. I, D 70569 Stuttgart, Germany Received 22 May 1995 Abstract Recent reports on high transient transverse voltages at room temperature in Y,Ba,Cu,O, (YBCO) thin films exposed to laser irradiation show that the thermoelectric fields transverse to a laser-induced temperature gradient are caused by the nonzero off diagonal elements of the Seebeck tensor. To further enhance these signals of a size approximately 0.1 V/K we used the dependence of the Seebeck coefficient on the in plane thermoelectric properties of YBCO. Thin films with a partial substitution of Y by Pr epitaxially grown on Strontiumtitanate single crystals cut with a tilt angle of 10” between substrate surface and the cubic axis are exposed to LJV photon pulses (A = 248 nm, pulse length 28 ns, fluences 5-200 ml/cm*) at room temperature. Compared to the undoped films the an enhancement of the signal by a factor of 20 is found for YU,,Pr,,zBa,Cu,O, films. Further increase of the doping level, however, caused a decrease of this peak values. This result is ascribed to the anisotropic changes of the Seebeck tensor matrix components upon doping. 1. Introduction (ii) The voltage is proportional to the laser power Soon after the publication of a pioneering paper describing the observation of laser-induced voltages by Chang et al. [ll several groups reported support- ing experimental evidence [2-41 for this effect and various attempts for the explanation of these surpris- ing results have been discussed. The experimentally established facts published in [l-4] are summarized as follows: (i) Pulsed laser irradiation at room temperature of nearly c-axis oriented YBCO thin films causes tran- sient transverse voltages up to several volts with a decay time < 1 us. at least as long as the photon energy Is kept constant. Varying the photon energy causes slight changes of the voltage. (iii) The voltage is not depending on the polariza- tion of the laserbeam. (iv) Continuous irradiation causes a continuous voltage. (v) The voltage is proportional to the tilt angle of the YBCO c-axis with respect to the film plane. (vi) Thermal heating instead of laser-heating shows that the signal strength is only related to the flow of the thermal energy through the film and finally (vii> The signal d ecay after laser pulse termination * Corresponding author. E-mail: huh@ servixmpi- can be quantitatively modelled by a themlal heat stuttgakmpgde. propagation model. 0169~4332/96/$15.00 0 1996 Elsevier Science B.V. All rights reserved SSDZO169-4332(95)00545-5