Ferroelectricity of the 1.7 nm-high and 38 nm-wide self-assembled PbTiO3 island

Crystalline and ferroelectric properties of nanosized PbTiO3 islands grown at 390 and 560 °C by metalorganic chemical vapor deposition (MOCVD) were investigated by the grazing incidence X-ray diffraction (GIXD) method and piezoresponse scanning force microscopy (PFM). By reducing the growth temperature from 560 to 390 °C, average height of PbTiO3 islands decreased from 19 to 3.6nm while the average width slightly decreased from 49 to 41nm. GIXD measurements revealed that nanosized PbTiO3 islands with the pure perovskite phase were successfully grown at 390 and 560 °C. Preferential orientations of PbTiO3 islands grown at 390 and 560 °C were (001) and (111), respectively. Using PFM, piezoelectric hysteresis loops with polarization reversal were obtained at each individual island. This is evidence for the presence of ferroelectricity in nanosized islands. The minimum island exhibiting ferroelectricity was 1.7 nm high and 38 nm wide.