Yttrium oxide films prepared by pulsed laser deposition

Abstract

Yttrium oxide, Y2O3, films were prepared by pulsed laser deposition in the presence of oxygen (O2) gas. The microstructures of these films were found to be highly dependent on the deposition temperature and the amount of O2 gas used during the deposition process. X-ray diffraction (XRD) analysis showed that the Y2O3 films transformed from amorphous to polycrystalline form when the deposition temperature was increased to 350 °C at an O2 pressure of 0.01 mbar, and an extremely strong XRD peak originated from Y2O3(111) orientation was observed when the deposition temperature was increased above 400 °C. However, during the deposition at a fixed temperature (650 °C), the Y2O3 films became amorphous when the O2 pressure was successively increased. For the films deposited on either fused silica or silicon substrate between 150 and 650 °C, very smooth surface morphologies with an average surface roughness of 0.4–19 nm have been observed by an atomic force microscopy. UV/Visible spectrometer and Fourier transform infrared analysis have shown that the as-grown Y2O3 films are highly transparent from the UV (with a band gap 5.6 eV) to the middle infrared region (∼15 μm). The refractive index of the Y2O3 films measured by a spectroscopic ellipsometer changed from 1.9 to 2.15 with decreasing wavelength. Furthermore, a good waveguiding property has been observed in the as-grown Y2O3 films. The dielectric constant of these Y2O3 films measured by a standard ferroelectric test system is between 11 and 18 depending on the film thickness. A C–V measurement has confirmed that these Y2O3 films are indeed good for metal-insulator-semiconductor device applications.