The Nano-Fabrication Of Ultra Fast Photoconductive Switch

The final aim of Nanotechnology is to fabricate special functional apparatus.A ultra-fast photoconductive switches and Tunneling junctions were fabricated with micro-electronic optical lithography, dual facing target sputtering and AFM anodic oxidation .The dissertation studies and analyzes them systematically.The main contributions are as follows:1. The influencing factors of AFM anodic oxidation were analyzed from the theoretical and experimental research .The proper conditions to perform AFM oxidation of titanium were biased voltage of 8V, scanning speed of 0.1μm/s and relative humidity of 30%~50%.On this condition ,the oxidized lines or dots can get good continuity, evenness and repeatability. The scanning speed of 0.1μm/s was approved;2. Theoretically, an equivalent circuit model for ultrafast linear PCSS's has been proposed. Based on the model, the output characteristic of PCSS's was simulated by MATLAB software both in time and frequency domain. A special phenomenon was found and explained. Its half width was 10fs and the band width was 5.5THZ. The possibility and influence of THz radiation by linear PCSS's has been analyzed;3. Structure design and fabrication process of novel photoconductive switch were carried out. Three masks were designed and prepared to form transmission lines and electrodes of ultra-fast photoconductive switch. From analyzing, GaAs grown by molecular beam epitaxy (MBE) at low substrate temperatures was chosen as the substrate, oxidation titanium line fabricated on ultra-thin titanium film by AFM anodic oxidation as the functional part and coplane strip geometry as the transmission line of photoconductive switch to form a novel ultra-fast photoconductive switch;4. Thin titanium film can be oxidized completely with scanning probe microscope (SPM) via anodic oxidation to form MOS (Tip-the oxidized line–the semiconductor substrate) and MIM(Ti-TiOx-Ti) structure which were both studied theoretically and experimentally. The tunneling phenomenon of multi- tunneling junctionsWere analyzed.