Preparation And Optical Properties Of Rare Earth Ions Doped ZnO Films

In recent years, with the development of thin film technologies and application of materials, nano film materials as new kinds of the semiconductor materials has a wide range of application in various areas of production. ZnO as a new type of multifunction semiconductor with a wide band gap, has been extensively studied in lighting-emitting diodes, field effect transistors, room temperature ultraviolet lasers, solar cells and piezoelectric gated diode, gas sensor. Unique properties of ZnO are a direct band gap of3.37eV at room temperature(RT),large exciton binding energy of60meV and excellent physical and chemical properties, which allow efficient ultraviolet excitonic emission at room temperature, as laser and short wavelength near UV light emitting diode. Rare earth ions have unique magnetic, electrical and optical properties, due to rare earth ions have special shell structure, RE3+ions emission peaks usually involve4f-4f transitions. The RE3+ions can be a luminescence center of luminescence materials, because it have a large number of characteristic sharp emission peaks in the band of visible, near infrared spectral region and near ultraviolet. Consequently, Rare earth ions doped ZnO films have received a extensive attention by researchers at home and abroad.In this paper, we prepared the high-quality Er3+/Yb3+co-doped ZnO thin films by the RF magnetron sputtering technique using Er3+/Yb3+co-doped ZnO ceramic target on sapphire substrates and quartz glass substrates. Structural, elements, and waveguide properties of the deposited thin films were investigated by using many analyzing approaches. The main contents of this paper are as follows:The structural and crystal quality of deposited the thin films were studied by XRD, the results demonstrate that the temperature of substrate on the structural have an important effect on crystal quality of films. The films appear (002) and (100) diffraction peaks when the substrate temperature lower than200℃,while, the peak along (100) is dismissed and appear (004) diffraction peak when the substrate temperature higher400℃. With the increase of the substrate temperature, the FWHM of (002) diffraction peak decreased, Er3+/Yb3+doped ZnO thin films with a strong c-axis orientation. The effective refractive index of TE and TM mode for Er3+/Yb3+doped ZnO thin films were measured by prism coupling method at a wavelength of633nm, it was found that the indexes refractive of the thin films are less than of the ZnO bulk crystal. Consequently, with the increase of the substrate temperature, the crystalline quality of the thin films is improved, the average roughness is also reduced, and it can change the indexes refractive of the thin films. The composition of thin film is analyzed by Rutherford backscattering (RBS) to calculate the film thickness, and the difference of the film thickness is only1.1%compared to application prism coupling method to measure the film thickness. It was found that a weak green light with the naked eye visible by980nm laser beam irradiating the sample surface.The structural and crystal quality of deposited the thin films were studied by XRD, the results demonstrate that various of Oxygen Argon ratios on the structural have an important effect on crystal quality of films. All the films appear (002),(004) diffraction peaks and the films with a strong c-axis orientation. With the increase of the Oxygen pressure, the intensity of diffraction peak increased, the FWHM decreased, the strong diffraction peak with a narrow FWHM in Oxygen/Argon equal to2/16. The effective refractive index of TE and TM mode for Er3+/Yb3+doped ZnO thin films were measured by prism coupling method at a wavelength of633nm, it was found that the effective refractive index of Er3+/Yb3+doped ZnO nano-thin films is closer to ZnO crystal refractive index in Oxygen/Argon equal to2/16, and the films have well planar waveguide structure. The films with a strong c-axis orientation and improve the crystalline quality of the thin films when various of Oxygen Argon ratios decreased.The structural of the thin films were studied by XRD, the results shows that the strong (002),(004) diffraction peaks with a narrow FWHM and the big grain sized Er3+/Yb3+doped ZnO thin films with a strong c-axis orientation and the crystalline quality of the thin films is better on sapphire substrate materials.The effective refractive index of TE and TM mode for Er3+/Yb3+doped ZnO thin films were measured by prism coupling method at a wavelength of633nm, it was found that the indexes refractive of the thin films are less than of the ZnO bulk crystal. The effective refractive index of Er3+/Yb3+doped ZnO nano-thin films on sapphire substrate is closer to ZnO crystal refractive index. The films with a strong c-axis orientation and better optical waveguide properties of thin films on sapphire substrate materials.