Organic Thin Film Transistor Integration

Abstract

This thesis examines strategies to exploit existing materials and techniques to advance organic thin film transistor (OTFT) technology in device performance, device manufacture, and device integration. To enhance device performance, optimization of plasma enhanced chemical vapor deposited (PECVD) gate dielectric thin film and investigation of interface engineering methodologies are explored. To advance device manufacture, OTFT fabrication strategies are developed to enable organic circuit integration. Progress in device integration is achieved through demonstration of OTFT integration into functional circuits for applications such as active-matrix displays and radio frequency identification (RFID) tags.OTFT integration schemes featuring a tailored OTFT-compatible photolithography process and a hybrid photolithography-inkjet printing process are developed. They enable the fabrication of fully-patterned and fully-encapsulated OTFTs and circuits. Research on improving device performance of bottom-gate bottom-contact poly(3,3′′′-dialkyl-quarterthiophene) (PQT-12) OTFTs on PECVD silicon nitride (SiN x ) gate dielectric leads to the following key conclusions: (a) increasing silicon content in SiN x gate dielectric leads to enhancement in field-effect mobility and on/off current ratio; (b) surface treatment of SiN x gate dielectric with a combination of O 2 plasma and octyltrichlorosilane (OTS) selfassembled monolayer (SAM) delivers the best OTFT performance; (c) an optimal O 2 plasma treatment duration exists for attaining highest field-effect mobility and is linked to a "turnaround" effect; and (d) surface treatment of the gold (Au) source/drain contacts by 1-octanethiol SAM limits mobility and should be omitted. There is a strong correlation between the electrical characteristics and the interfacial characteristics of OTFTs. In particular, the device mobility is influenced by the interplay of various interfacial mechanisms, including surface energy, surface roughness, and chemical composition.Finally, the collective knowledge from these investigations facilitates the integration of OTFTs into organic circuits, which is expected to contribute to the development of new generation of all-organic displays for communication devices and other pertinent applications. A major outcome of this work is that it provides an economical means for organic transistor and circuit integration, by enabling use of the well-established PECVD infrastructure, yet not compromising the performance of electronics.iv

Thermoelectric Effect and Application of Organic Semiconductors

“…Since proof of concept for organic semiconductors occurred in the 1980s, remarkable development of organic semiconductors has promoted improvement of performance that maybe competitive with amorphous silicon (a-Si), increasing their suitability for commercial applications [7]. Appearance of conductive polymers in the late 1970s, and of conjugated semiconductors and photoemission polymers in the 1980s, greatly accelerated development in the field of organic electronics [8]. Polyacetylene was one of the earliest polymer materials known to be potential as conducting electricity [9], and one could find that oxidative dopant with iodine could greatly increase conductivity by 12 orders of magnitude [10].…”

Investigation of the Electrical Parameters of the Organic Diode Modified with 4-[(3-Methylphenyl)(phenyl)amino] Benzoic Acid

“…As a result, lower RMS roughness is the key reasons for improved mobility in the devices. 26 The roughness values of fabricated thin films summarize in the Table I.…”

Highly Dielectric and Photo-patternable Gate Insulators for Organic Field-effect Transistors

“…The transfer current-voltage plots are shown in Figure 6. The mobility was calculated using Equation (1) described in the introduction. The charge carrier mobilities can be extracted from the slopes of the linear plots of the square root of the drain current versus gate voltage.…”

“…Organic field-effect transistors (OFETs) have attracted great interest due to their potential for lightweight, low cost fabrication, compatibility with a flexible substrate, and the device fabrication through solution processes [1]. For these reasons, OFET is expected to be applied to future generation electronic devices such as flexible displays and low-end electronics such as radio frequency identification (RFID) cards [2,3].…”

“…The drain-source current (I SD ) of OFETs in the saturation regime is expressed by equation 1; (1) where μ is the mobility of the semiconductors, C i is the capacitance per unit area of the gate insulator, V G is the gate applied voltage, V T is the threshold voltage, and W and L are the channel width and length, respectively. Since C i can directly affect the OFET properties as represented by Equation 1, a high C i is required for gate insulators.…”