Studies On The Fabrication Of Novel Ultra Fast Photoconductive Switch

Thin titanium film can be oxidized completely with scanning probe microscope (SPM) via anodic oxidation to form Metal-Insulator-Metal (MIM) structure to fabricate various nanometer scale electronic and opto-electronic devices, such as single electron transistor (SET), high electron mobility transistor, single electron memory (SEM) and photoconductive switch. Ultra-fast photoconductive switch has extensive application in the field of ultra-fast devices testing and optical communication. The key problems of design and theoretical calculation of ultra-fast photoconductive switch, preparation and characterization of substrate material, and characteristic measurement of the fabricated prototype device were extensively studied in this dissertation. The research work mainly includes four aspects as follows:1. The substrate materials of nano electronic and nano opto-electronic devices were compared and selected. 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. The approximate numerical value of output characteristic of the designed novel device was solved.2. Fabrication and testing methods of nano thin film were developed. Ultra-thin titanium film was deposited with dual facing target sputtering system, the surface flatness of the film was measured with AFM and the I-V curve of the film was measured with STM. The measured results indicated that the deposited titanium film was very flat and homogeneous and it had excellent conductivity. So it can be used for anodic oxidation.3. Experiments of AFM anodic oxidation of Ti film under various conditions were extensively carried out and relevant theoretical modeling was deduced based on present theories. 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%. Under such conditions, six nano-oxidation titanium lines 5μm long were fabricated...