Abstract
The purpose of this dissertation was to explore the approach of directly preparing high-quality crystalline Si films at low temperatures on a polyimide substrate for use in flexible crystalline Si film-based electronics. For this reason, a low-temperature technique was developed to synthesis intrinsic crystalline Si film using microwave plasma enhanced chemical vapor deposition (MWPECVD) with H2-diluted silicon tetrachloride (SiCl4) mixture as the precursor at a temperature as low as 185oC. The growth mechanism of high crystallinity arises from the synergistic effects of preferential etching, self-cleaning and chemical annealing by the stronger etching species of H and Cl radicals in the high density plasma process accompanying with ion bombardment effect. To dope the crystalline Si film efficiently, the self-biased sputtering solid doping source (SSSDS) process integrated in SiCl4/H2 microwave plasma was proposed. We also synthesized crystalline Si pillar film with a sharp apex nanostructure via the Au-catalyzed vapor–solid–solid (VSS) mechanism using the SiCl4/H2 microwave plasma, followed by H2 plasma treatment. Furthermore, the resulting crystalline Si films (i.e., intrinsic Si film, doped Si film and Si pillar film) were implemented in flexible crystalline Si film-based electronics. The device performance showed that the flexible Si-thin film transistors using 100 nm intrinsic crystalline Si film as channel layer, exhibited excellent characteristics of high field-effect carrier mobility as high as 106 cm2/Vs and on/off current ratio of 1.2 × 106. Doped and intrinsic crystalline Si films could further be incorporated into a flexible crystalline Si-solar cells with a single junction n–i–p structure. They showed the best performance in open-circuit voltage of 0.54 V, short-circuit current density of 20.91 mA/cm2, and efficiency of 7.36%. In addition, the flexible Si-field emission display using the H2 plasma treated B-doped crystalline Si pillar film as cathode revealed high electron field emission behavior and stability, viz., the low turn-on field of 5.88 V/μm, high current density of 1.39 mA/cm2@10 V/μm, and extremely long half-lifetime over 10 hr were achieved. The superior flexibility for these soft electronics were also demonstrated. These results thus represent important steps toward a low-cost approach to high-performance flexible crystalline Si film-based electronics.