Low-voltage Thin-Film Transistors

Abstract

Anodically oxidized, ultra-thin (d < 5 nm) films emerge as the dielectric of choice for low-cost thin film capacitors, low voltage thin film transistors (TFTs) and TFT-based bio and chemical sensors. In this thesis, the fabrication and optimization of ultrathin films of anodically oxidized aluminium oxide as the gate dielectric for thin film transistors that can be operated at 1 V are described. In the initial study, the optimal anodic oxidation conditions of AlxOy films have been researched. It has been found that AlxOy films anodized at 2.3 V (d ≈ 3 nm) possessed the highest dielectric constant and the lowest leakage currents which facilitated the high gate capacitance, and as a result, the ultra-low voltage transistor operation. The feasibility of achieving low threshold voltage TFTs that can be operated at 1 V using the optimized 2.3 V anodized alumina dielectric film has been verified by demonstrating both high performance p-channel organic transistors (OTFTs), as well as n-channel metal oxide transistors (MOTFTs). Furthermore, low voltage OTFTs using water-processed IDT-BT organic semiconductor nanoparticle films as the active layer capable of operating well below 5 V with saturation field-effect mobilities higher than 5×10-2 cm2/Vs have been successfully demonstrated by introducing a newly developed spin-spraying deposition technique. Lastly, low voltage, high performance PDPPTT p-channel OTFTs operating at 1.5 V with saturation field-effect mobilities around 10-1 cm2/Vs have been successfully demonstrated using ultra-thin (d < 10 nm), photocatalytically-oxidized (PCO) alumina dielectric films. It appears that as it is in the case of the anodic alumina, PCO alumina insulator films have a high potential to enable the fabrication of ultra-low voltage capacitors and TFTs in a highly reproducible manner.

Date of Award	31 Dec 2019
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Leszek Majewski (Supervisor) & Max Migliorato (Supervisor)