One-Volt, Solution-Processed Organic Transistors with Self-Assembled Monolayer-Ta2O5 Gate Dielectrics.

Navid Mohammadian,Leszek A Majewski,Srikrishna Sagar,Michael L Turner,Sheida Faraji,Bikas C Das

doi:10.3390/ma12162563

Abstract

Low-voltage, solution-processed organic thin-film transistors (OTFTs) have tremendous potential to be key components in low-cost, flexible and large-area electronics. However, for these devices to operate at low voltage, robust and high capacitance gate dielectrics are urgently needed. Herein, the fabrication of OTFTs that operate at 1 V is reported. These devices comprise a solution-processed, self-assembled monolayer (SAM) modified tantalum pentoxide (Ta2O5) as the gate dielectric. The morphology and dielectric properties of the anodized Ta2O5 films with and without n-octadecyltrichlorosilane (OTS) SAM treatment have been studied. The thickness of the Ta2O5 film was optimized by varying the anodization voltage. The results show that organic TFTs gated with OTS-modified tantalum pentoxide anodized at 3 V (d ~7 nm) exhibit the best performance. The devices operate at 1 V with a saturation field-effect mobility larger than 0.2 cm2 V−1 s−1, threshold voltage −0.55 V, subthreshold swing 120 mV/dec, and current on/off ratio in excess of 5 × 103. As a result, the demonstrated OTFTs display a promising performance for applications in low-voltage, portable electronics.

Highlights

Organic thin-film transistors (OTFTs) have been attracting interest owing to their developing applications in low-cost, light-weight, and flexible electronic devices such as active-matrix displays [1], radio frequency identification tags [2], and bio and chemical sensors [3]
All electrical measurements were done in ambient conditions in an electrically shielded, dark box
Manchester, A thick, i.e.,the thicker than depth of X-ray photoelectron spectra (XPS), oxide was observed on the anodized region of the samples

Summary

Introduction

Organic thin-film transistors (OTFTs) have been attracting interest owing to their developing applications in low-cost, light-weight, and flexible electronic devices such as active-matrix displays [1], radio frequency identification tags [2], and bio and chemical sensors [3]. The demonstrated p-channel transistors displayed relatively low mobility (~0.02 cm V−1 s−1 ), positive threshold voltage (+0.26 V), large subthreshold swing (> 1 V/dec), and their on/off current ratios were just above 10. This shows that the fabrication of high performance, organic semiconductor. VTH should be around 0 V and SS close to 60 mV/dec, which is the theoretical limit of subthreshold swing at room temperature [16] This is a very challenging task, as it requires the gate dielectric thickness of high-κ materials to be reduced below 10 nm. The fabricated devices show typical p-channel transistor behaviour, demonstrating a high potential to use the developed process for practical organic TFT fabrication

Experimental Section

V bias the bottom electrode and the top

Results

Conclusions