Ultra-thin-film transistors based on ultra-thin amorphous ZnSnO films

Ultra-thin amorphous ZnSnO (a-ZTO) films were deposited by pulsed laser deposition at room temperature and annealed at various temperatures for ultra-thin-film transistors (UTFTs). The thicknesses of the ultra-thin a-ZTO films are approximately 3.1 nm. The electrical resistivity of the nanofilms decreases greatly with the annealing temperature initially increasing. All the UTFTs with annealing temperature ranging from 250 to 450 °C exhibit good switching properties operating in the enhancement mode with the field-effect mobility of above 8.2 cm V s. The annealing treatment exhibits extreme importance for the UTFTs to obtain better performance as oxygen vacancy is controlled easily in the ultra-thin films by annealing. The 350 °C-annealed a-ZTO UTFT depicts the largest field-effect mobility of 20.9 cm V s, the minimum threshold voltage of 2.3 V, the minimum subthreshold swing of 0.339 V/decade, the minimum density of the interfacial trap states of 1.02 × 10 cm and a large on/off current ratio of 3.3 × 10. Besides, the UTFT with the annealing temperature of 450 °C depicts excellent long-term stability under bias stress due to the least oxygen vacancies. The observations will offer basic design guideline for improvement and future applications of UTFTs.