FERROELECTRIC PHASE-TRANSITION IN PIEZOELECTRIC SEMICONDUCTOR ZNO

Ferroelectricity was found in Li-substituted II-VI semiconductor ZnO, although pure ZnO does not show any anomaly from 20 K to 700 K. Dielec tric anomaly, ferroelectric D-E hysteresis loop, and specific heat ano maly were observed in Zn0.9Li0.1O (T-c = 330 K). The spontaneous polar ization of Zn0.9Li0.1O is 0.9 mu C/cm(2) at room temperature. The ferr oelectric phase transition results from small structural distortion (o f order 10(-3) Angstrom) induced along the polar c-axis by the introdu ction of substitutional Li instead of the host Zn in wurtzite structur e.