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Title: Charge Dynamics of Metal/Organic Semiconductor Interface and Organic Field Effect Transistors: Numerial Simulation Studies
Authors: Kavala, A.
Keywords: Physics
Issue Date: 2017
Publisher: IIT Patna
Series/Report no.: TH-61;
Abstract: Among various organic semiconducting molecular materials, Pentacene has picked up sufficient impetus in past few years. This is because of its two unique advantage over its larger sibling, the conjugated polymers, (a) highest hole mobility among all known organic materials, polymeric or molecular, and (b) ease of making high quality thin film using thin film techniques, thus minimizing trap density. The primary focus in this material is mostly directed to attain higher field effect mobility in organic field effect transistors based on Pentacene. Concurrently, charge dynamics among organic devices (ODs) has also remained a very active topic of research for the past few decades. Unlike the silicon based electronic devices, charge traps and interface energetic significantly shape the charge conduction through any organic device. Therefore, the effect of traps and interface dynamics upon the charge conduction in a Pentacene based organic device is a feature worth researching. This thesis investigates the role of charge traps in Gold/ Pentacene/ Gold sandwich device and role of metal/organic interface in downsized-channel OFET’s by using self-consistent treatment of drift-diffusion, current continuity and Poisson’s equation in a process of numerical simulation modelling. In the former one, numerical simulation of a practical Gold/ Pentacene/ Gold sandwich device I –V characteristics is performed at various temperatures. The results have revealed positive value of Poole Frenkel coefficient and an estimate of field free mobility. Another physical parameters effective carrier density due to traps, have also been estimated in this study. The novelty lies in deduction but not assumption of these physical parameters. In the latter one, study of OFET based on Pentacene has been numerically obtained for a channel length of 500 nm. The output characteristics obtained in this computation has shown a good match with the nature of experimental data reported earlier. The non-linear low voltage output characteristics, termed as sub-threshold like characteristics, has been interpreted in light of thermionic emission model because of the presence of hole injection barrier at drain gold/Pentacene interface. This kind of analysis has facilitated the xviii evaluation of effective channel thickness as a function of transverse electric field due to gate, a parameter which is reported for the first time for Pentacene OFET. Owing to the general nature of treatment, the methodology developed in this study could be applied to any OFET irrespective of the nature of organic semiconducting material for active channel. The analysis is been carried out for both theoretical and experimental OFETs.
Appears in Collections:05. PH

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