An Investigation of Structural, Optical and Pyroelectrical Properties of LiTaO3

Abstract

In this study, structural, optical, and pyroelectric properties of Z-cut single crystal LiTaO3 bulk materials with thicknesses of 27 mu m and 250 mu m are analyzed. XRD results show characteristic diffraction peaks of Z-cut LiTaO3 at (012), (006), and (202), along with a Ta2O5 peak due to Li-deficiency. The strong (006) peak confirms a high c-orientation, indicating pyroelectric potential. Raman spectroscopy confirms agreement with known vibration modes of bulk LiTaO3. Band gap values for the 27 mu m and 250 mu m samples are determined as 4.44 eV and 4.65 eV, respectively, with both showing a direct band gap. Temperature changes from 30 degrees C to 180 degrees C were applied at rates of 50 degrees C, 100 degrees C, and 150 degrees C. As temperatures rose, negative pyroelectric currents were observed; with cooling, currents shifted positive. The 250 mu m thick, 24 mm(2) LiTaO3 wafer produced about 4 nA at 50 degrees C rate, rising to 12-13 nA at 150 degrees C. With larger surface areas yielding higher currents, measurements on three wafers at a 50 degrees C change showed the highest-area sample producing similar to 7.5 nA, while the smallest yielded similar to 0.5 nA. The mean pyroelectric current density was higher in 27 mu m (180 mu A/m(2)) than in 250 mu m (125 mu A/m(2)), and the pyroelectric coefficient increased with decreasing thickness, measured at 33.43 mu C/m(2).K (27 mu m) and 23.22 mu C/m(2).K (250 mu m). These results suggest the potential of LiTaO3 crystals in IR detectors and self-powered deep UV detector applications due to their wide band gap.