Organic Field-Effect Transistors pentacene

Only recently it has been discovered that electronic states at the dielectric interface substantially determine the charge carrier transport in organic field-effect transistors. Pentacene is a prominent example where the unique p-type behavior of pentacene based OFETs has been attributed to the organic semiconductor alone and where the influence of electronic interface states at the pentacene/insulator surface has been overseen. The reason for this was the belief that organic semiconductors are unable to form dangling bonds at the interface, which are the main cause for interface states in inorganic semiconductors. However, there are other forms of interface states which can act as efficient charge carrier traps. 

In the context of organic field-effect transistors (OFETs), two novel 1,4-dithiins, 43-ry and 7>-anti, have been prepared as pentacene analogues <2004JOC2197, 2003JOC9813>, consisting of the parent 1,4-dithiin with a benzo[7]thiophene on both sides <2004TL7943>. 

Growth Morphologies and Charge Carrier Mobilities of Pentacene Organic Field Effect Transistors with RF Spnttered Alumininm Oxide Gate Insnlators on ITO Glass... 

Presently there exists a strong research interest in the understanding, development, and optimisation of organic field effect transistors (OFETs) [1, 2]. Two classes of semiconducting organic materials are considered, namely molecular materials which are processed into thin films by vacuum sublimation [1, 2], and polymers which are deposited onto substrates in the form of solutions, for instance by spin coating [3]. In this chapter we report on OFETs based on thin polycrystalline films of the molecular material pentacene (Pc) as the semiconducting material. 

Figure 8.1 Schematic cross section of our pentacene (Pc) organic field effect transistors.

Off-currents have also been measured at some organic field effect transistors using silicon dioxide as the gate dielectric. During the investigations it was not possible to detect the real reason for this sporadically occurring behaviour, which was only detectable after the pentacene deposition. One explanation could be the generation of interface traps as a consequence of the pentacene deposition. 

Abstract. Pentacene organic field effect transistors (OFETs) electrical and structural properties have already been analysed from the point of view of different gate dielectric and growth conditions utilization. The AFM and micro Raman investigations show that the first organic monolayer at the pentacene/dielectric interface are essential determinants of carrier transport phenomena and achievable drain current of pentacene OFETs. 

Dimitrakopolous, C.D., Brown, A.R., and Pomp, A., Molecular beam deposited thin films of pentacene for organic field effect transistor applications, J. Appl. Phys., 80, 2501, 1996. 

Cui, T.H. and Liang, G.R., Dual-gate pentacene organic field-effect transistors based on a nanoassembled SiOj nanoparticle thin film as the gate dielectric layer, Appl. Phys. Lett. 86 (6), 064102, 2005. 

Jung, S.Y. and Yao, Z., Organic field-effect transistors with single and double pentacene layers, Appl. Phys. Lett. 86, 83505, 2005. 

Yang, S.Y, Shin, K., and Park, C.E., The effect of gate-dielectric surface energy on pentacene morphology and organic field-effect transistor characteristics, Adv Func. Mat, 15, 1806, 2005. 

Poly(tetrafluoro-/7-xylylene) can be used as a gate dielectric for pentacene-based organic field-effect transistors [41]. This polymer can be deposited by chemical vapor polymerization even at room temperature. The dielectric constant shows an extraordinary stability at sr of 2.3. 

Guo TF, Tsai ZJ, Chen SY, Wen TC, Chung CT (2007) Influence of polymer gate dielectrics on n-channel conduction of pentacene-based organic field-effect transistors. J Appl Phys 101 124505... 

Paasch G, Scheinert S (2007) Space charge layers in organic field-effect transistors with Gaussian or exponential semiconductor density of states. J Appl Phys 101 024514 Sze SM (1981) Physics of semiconductor devices, 2nd edn. WHey, New York Lin Y-Y, Gundlach DJ, Nelson SF, Jackson ThN (1997) Pentacene-based organic thin-film transistors. IEEE Trans Election Dev 44 1325-1331... 

Ahles M, Schmechel R, von Seggem H (2(X)4) n-Type organic field-effect transistor based on interface-doped pentacene. Appl Phys Lett 85 4499-4501... 

Functionalization of pentacene with the specific aim of improving performance in devices is a recent endeavor - the first use of a functionalized pentacene in a field-effect transistor was reported only recently (2003) [26], Functionalization of pentacene has led to the ability to engineer the solid-state arrangement, electronic, and solubility properties of this important semiconductor and to improve its stability and film-forming ability. Recent functionalized pentacene materials have yielded devices with properties comparable with those of the parent acene, have enabled the formation of devices from solution-deposited films, and have even changed the semiconductor behavior of this organic molecule from p-type to n-type. As functionalization strategies are refined, materials with all of the properties necessary for commercial device applications should soon be developed. 

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