ZnO were deposited on sapphire and silicon substrates by RF magnetron sputtering from a metallic zinc target. The structural and optical propertied of ZnO films were studied by X-ray diffraction, and UV-VIS-NIR scanning spectrophotometer. XRD measurements show ZnO films had a preferential orientation along the c-axis. Only one peak, (002) phase, appears on the diffraction spectra. The transmittance spectra indicate that ZnO films possessed a transmittance of about 80% in the visible region and a sharp absorption edge at wavelength of about 390nm. The refractive index n and the extinction coefficient k are all sensitive to the oxygen partial pressure and the substrate temperature. Furthermore, based on the ideal five layers symmetrical waveguide films, the relationships of the loss and the thickness of the waveguide layer and the buffer layer were analyzed using ZnO as waveguide layer and SiO2 as buffer layer.
Microcavity structures are widely utilized as resonators in many optoelectronic devices to improve their optical performance. We present an analytic approach to study the angle-dependent properties in active microcavities with dielectric Bragg reflectors. Based on the hard mirror (HM) model and paraxial propagation approximation, the angle dependent resonance properties can be expressed analytically in virtue of the cavity parameters and incident angle. Making use of these expressions, we found both the position of the active layer and the configuration of dielectric Bragg mirrors contribute to the angular characteristics of resonance in the active microcavity. The varying trend of the standing wave effect, intracavity electrical field and the degradation of quantum efficiency due to different incident angle are discussed in detail. It's found that there exists an optimal cavity configuration where the enhanced intracavity resonance can keep high value within a broader incidence range. Then further performance optimization of the whole devices can be performed.
Graded refractive index Silicon Oxy-nitride thin films were deposited by RF magnetron reactive sputtering at different N2/O2 flow ratio. The effects of gas flow ratio on the refractive index, extinction coefficient and composition were studied using UV-VIS spectrophotometer, XPS and FTIR characterization methods. A simple and accurate method is presented for determination of the optical constants and physical thickness of thin films. Which was consisted in fitting the experimental transmission curve with the help of the physical model. The relationship between composition and optical gap and dispersion energy was analyzed using Wemple DiDomenico single-oscillator model. As a result, the samples’ refractive index can be controlled from 1.92 to 1.46 by adjusting the gas flow ratio, and the optical gap lies between 5eV~6.5eV.
Novel organic light-emitting diodes (OLEDs) using polymidy, fluorene-based cardo perylere polyimide (PFB5) were fabricated. EL properties of single-layer light-emitting diodes (LED) of indium-tin-oxide (ITO)/PFB5+/Al and ITO/PFB5+PBD/Al and multi-layer devices of ITO/PFB5/PBD/Al,ITO/PFB5/Alq/Al were characterized. In the pure PFB5 single layer device, the EL spectrum has a broad band and the peak wavelenght at 420nm, 450nm, and 545nm respectively. However, the EL emission fromthe single layer deviec of PFB5 blend PBD or multi-layer devices has the greatly narrow band and the peak wavelength at 545nm. Furthermore, the EL efficiency is improved significantly in these EL devices.