Structural, optical, and electrical characterization of gadolinium oxide films deposited by low-pressure metalorganic chemical vapor deposition

Abstract

We report the growth and characterization of gadolinium oxide films deposited on Si(100) and fused quartz in the temperature range of 450–800°C by a low-pressure metalorganic chemical vapor deposition technique using a β-diketonate complex of gadolinium as the precursor. The x-ray diffractometry study of the films reveals that, irrespective of the growth temperature, the films grown on fused quartz (i.e., an amorphous substrate) and silicon (i.e., a single-crystal substrate) comprise the cubic Gd2O3 phase with a (111) texture. However, the films grown on fused quartz at higher temperatures also show the presence of the monoclinic phase of Gd2O3. The growth of strongly oriented films on fused quartz has been understood on the basis of minimization of the surface energy. The scanning electron microscopy and atomic force microscopy studies reveal that the films grown at or above 525°C are densely packed and grainy. Optical properties of the films, as studied by ultraviolet (UV)-visible spectrophotometry and Fourier transform infrared spectroscopy, are found to depend strongly on the chemical vapor deposition condition. The analyses reveal further that the films grown at or above 500°C are free of heteroatoms, i.e., C, N, and H. The optical band gap of the films is in the range of 5.0–5.4eV. Electrical characterization was carried out on Al∕Gd2O3∕Si metal-insulator-semiconductor structures by capacitance–voltage (C–V) and current–voltage analyses. The effective dielectric constant of the films was in the range of 7–23. The bidirectional C–V characteristics show a counterclockwise hysteresis due to the presence of slow interface traps. A minimum leakage current of 4.6×10–5A∕cm2 at the 1-MV∕cm field was demonstrated.