Characterization of acceptor-doped $Ba_{0.6}Sr_{0.4}TiO_3$ thin films as gate insulators for low voltage operating thin film transistors fabricated at room temperature

Abstract

Flexible electronics on polymer substrates require device structures that are amendable to room temperature fabrication and processing. Organic thin film transistors (OTFTs) based on pentacene satisfy this criteria. OTFTs have received intense interest for applications requiring, structural flexibility, large area coverage, and low-cost. Such applications include active matrix OLED/LCD displays, sensing devices, and radio frequency identification (RFID) tags. To obtain low voltage operation (a requirement for low power electronic systems) and high performance (i.e. high mobility), OTFTs often require the use of high capacitance gate insulator suitable for portable, battery-powered device applications. High capacitance gate insulators can be obtained by the use of very thin films and/or high dielectric constant gate materials. Very thin gate insulators can lead to significant manufacturing problems given that the surface roughness of the polymers may be on the order of the thickness of the insulators leading to pinholes in the insulator, and high resultant leakage currents. Flexible polymer substrates, often characterized by rough surfaces (RMS roughness ~ 3 nm), therefore benefit from the use of high-K dielectrics given that high electric fields can be achieved with use of thicker films (~ 200 nm) without need to increase operating voltage. Further, room temperature processing could enable 3D integration of large stacks of active electronic device layers as well as flexible/wearable electronics, and conformable 3D imaging. In addition, transparent thin film transistors (TTFTs), represented by ZnO-based TFTs which can be processed at room temperature have attracted much attention due to their potential of replacing hydrogenated amorphous or polycrystalline silicon (a-Si:H or poly-Si) TFTs. ZnO is a transparent compound semiconductor with a wide band gap (3.37 eV) which can be grown as a polycrystalline film at room temperature. Therefore, ZnO is considered to...