Micro/Nano Structural Thin Films Fabricated By Glancing Angle Deposition And Their Application In Electroluminescence Devices

Low-dimensional nanostructural thin films have attracted intensive attentions for their potential applications in many fields. They have unique physical and chemical properties. The films with controlled nanostructural also have potential applications in the miniaturization and integration of the optoelectronic devices. Glancing angle deposition technology is a physical evaporation method. Shadowing effect and evaporation rate of materials have influences on the nanostructures formed in the deposition process. Nanostructures of films also can be controlled by changing spatial positions between the incoming particle flux and the substrate multi-dimensionally. In this research, we fabricated thin films with different nanostructures by glancing angle deposition, investigated their optical and electrical properties, and used them into the electroluminescence devices. Thin films with array structures were used to improve the light outcoupling of the devices. The electron emission ability of the nanocolumn thin films under high electricity field was used to improve the primary electron source, and the electron transport and acceleration process of solid state cathodoluminescence.1. The glancing angle deposition system based on electron beam evaporation apparatus was constructed:the substrate holder, the propulsion system for substrate, and the controlling system. The glancing angle deposition system can be used to prepare nanostructural thin films by controlling the substrates rotating in three degrees of freedom. We measured and calibrated the parameters during the deposition process, and finally verified the reliability and stability of the system.2. ZnS thin films with different nanostructures were fabricated by glancing angle deposition technology. The influences of characteristic parameters on the films nanostructures during the deposition process were investigated, including the angle between the incoming particle flux and the substrate normal, the deposition rate, the rotation speed of the substrate and the substrate types. The dynamics growth process of nanostructural ZnS films was analysis. The morphology and crystallinity of nanostructural ZnS films were characterized and analyzed. The results show that:ZnS films with uniform columnar structures were fabricated when the oblique angle was set to80°, the rotation speed of substrate was0.05rev/s and the deposition rate was0.2nm/s. The ZnS nanocolumn thin films had the cubic sphalerite-type structure, and preferred to grow along the (111) direction. The continuous and compact ZnS films were fabricated when the oblique angle was fixed at0°, the preferred growth orientation of the compact films changed to (220) direction. The preferred orientation and the nanostructure of the films fabricated under different conditions are diversity. The effects of surface roughness of substrates on the nanostructures of ZnS films prepared at the same conditions were investigated.3. Improving the light outcoupling efficiency is a critical factor for improving the efficiency of organic light emitting devices (OLED). We investigated the transmitting abilities of the substrates with ZnS nanocolumn thin films deposited on the glass side of ITO/glass. The variation of nanostructures changed the refractive index of ZnS films, which could improve the transmittance properties of the substrates by reducing reflection. Diffraction effect of the periodic nanocolumn arrays could also increase the intensity of the transmitted light at normal direction. ZnS nanocolumn layers were applied into the OLEDs with the structure of ITO/NPB/Alq3(BAlq)/Al for the enhancement of outcoupling from the devices.4. ZnS:Mn thin films with different nanostructures were deposited on Si and ITO substrates by glancing angle deposition technology. ZnS:Mn films show the same crystallinity as ZnS films prepared above. ZnS:Mn thin films deposited at80°also had the cubic sphalerite-type structure with preferred orientation of (111). The continuous ZnS:Mn films deposited at0°show a preferred orientation of (220) direction.5. Electroluminescence devices with nanostructural ZnS:Mn films were fabricated. The cubic sphalerite-type structure of ZnS:Mn nanocolumn thin films with preferred orientation of (111) improved the transportation and acceleration ability of the films. The luminous intensities of the devices with ZnS:Mn nanocolumn films were enhanced.6. Performances of organic-inorganic hybrid devices with nanostructural ZnS or ZnS:Mn thin films were investigated. Electrons were accelerated in these nanostructural layers. Then the accelerated electrons could impact excitation luminescence centers resulting light emitting, or producing light emitting by reinjected recombinations of organic materials based on the theory of solid state cathodoluminescence. We got the mixed light emitting from the devices with ZnS:Mn/MEH-PPV as emitting layer. The devices including the nanocolumn thin films have higher luminous intensity.