Ferroelectricity of YMnO3 thin films prepared via solution

We have observed the ferroelectricity at room temperature in YMnO3 thin fil ms prepared via solution. Precursor films of YMnO3 on Pt/sapphire or Y2O3/S i substrates were heat treated in vacuum or in air for controlling the crys tallinity. X-ray diffraction measurements indicated that each film was a si ngle phase of hexagonal YMnO3. While the film heat treated in air indicated an insufficient crystallinity, the film heat treated in vacuum showed a hi gh crystallinity with a c-axis preferred orientation. The leakage current o f the film heat treated in vacuum was at least three orders of magnitude lo wer than that heat treated in air. The ferroelectricity of the film heat tr eated in vacuum was confirmed in the capacitance-voltage measurement at roo m temperature due to its high crystallinity with the c-axis preferred orien tation and the small leakage current. (C) 1999 American Institute of Physic s. [S0003-6951(99)04131-5].