Growth of ferroelectric Li-doped ZnO thin films for metal-ferroelectric-semiconductor FET

Kekuda, Dhananjaya and Nagaraju, J and Choudhury, Palash Roy and Krupanidhi, S B (2006) Growth of ferroelectric Li-doped ZnO thin films for metal-ferroelectric-semiconductor FET. Journal of Physics D: Applied Physics, 39. pp. 2664-2669.

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Abstract

A metal-ferroelectric-semiconductor structure has been developed by depositing Li-doped ZnO thin films (Zn1−xLixO, x = 0.25) on p-type Si substrates by the pulsed laser ablation technique. (002) preferential oriented films were deposited at a low growth temperature of 500 ◦C and 100mTorr oxygen partial pressure. The dielectric response of the films has been studied over a temperature range 250–373 K. A dielectric anomaly was observed at 360 K. The capacitance–voltage characteristics of Ag/Zn0.75Li0.25O/Si exhibited clockwise hysteresis loops with a memory window of 2V. The films deposited at 100mTorr pressure show a stable current density and a saturated polarization hysteresis loop with a remanent polarization of 0.09μCcm−2 and coercive field of 25 kV cm−1. Leakage current measurements were done at elevated temperatures to provide evidence of the conduction mechanism present in these films. Ohmic behaviour was observed at low voltage, while higher voltages induced a bulk space charge. The optical properties of Zn0.75Li0.25O thin films were studied in the wavelength range 300–900 nm. The appearance of ferroelectric nature in Li-doped ZnO films adds an additional dimension to its applications.

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