Organic field-effect transistor with octadecyltrichlorosilane (OTS) self-assembled monolayers on gate oxide: effect of OTS quality

Abstract

To cite this version:M. Devynck, P. Tardy, G. Wantz, Y. Nicolas, L. Hirsch. Organic field-effect transistor with octadecyltrichlorosilane (OTS) self-assembled monolayers on gate oxide: effect of OTS quality. European Physical Journal: Applied Physics, EDP Sciences, 2011, 56 (3) AbstractThe effect of OTS (octadecyltrichlorosilane) Self Assembled Monolayer (SAM) grafted on SiO 2 gate dielectric of pentacene based OFETs (organic field effect transistors) is investigated. A significant improvement of the charge mobility (µ), up to 0.74cm 2 /Vs, is reached thanks to OTS treatment. However, in spite of improved performances, several drawbacks, such as an increase in mobility dispersion, substantial hysteresis in I DS -V G characteristics and high threshold voltages (V T ) are observed. Changing solvent and deposition method turns out to have no significant effect on the mobility dispersion. A more accurate approach on the evolution of the mobility and the threshold voltage dispersion with OTS storage time highlights the effect of the OTS solution ageing. Even if no difference is evidenced in the surface energy and roughness of the OTS layer, electrical characteristics exhibit considerable deterioration with OTS solution storage time. Using an "aged" OTS solution, opened under air, kept under argon and distilled before use results in an increase of the I DS -V G hysteresis as well as in V T and in mobility dispersion. In comparison, fresh-OTS-based OFETs present a very low hysteresis, a threshold voltage close to 0 and a much lower mobility dispersion. It is demonstrated that aged OTS solutions contain impurities that are not removed by distillation process which lead to less densely packed layer causing interfacial charge traps thus deteriorated performances.

Silane-Based SAMs Deposited by Spin Coating as a Versatile Alternative Process to Solution Immersion

“…In contrast, the chemical vapor deposition (CVD) method consists of the exposure of a clean substrate to silane vapor, which does not require organic solvents. − However, CVD has to be performed in a sealed container in ultra-high vacuum conditions and generally at elevated temperature (150–200 °C), which may not be compatible with some sensitive organic functions, although deposition at room temperature may be possible in some cases. Other processes have been more rarely applied for the preparation of silane-based SAMs and less extensively studied in detail such as the Langmuir–Blodgett , method and the spin coating technique …”

“…Indeed, it has the advantages of being fast, simple, easy to handle, conducted in ambient conditions, and less demanding in terms of organic solvent. Monolayers derived from SiCl 3 -terminated carbosilane dendrons, p -tolyltrichlorosilane, and octadecylsilanes , have been afforded using the spin coating technique. More recently, we reported the first functional SAM elaborated via this technique.…”

“…Other processes have been more rarely applied for the preparation of silanebased SAMs and less extensively studied in detail such as the Langmuir−Blodgett 27,28 method and the spin coating technique. 29 Among these two, the spin coating technique, commonly used for thin films or multilayer deposition on planar substrates, attracts particular attention as an alternative to conventional SAMs deposition methods. Indeed, it has the advantages of being fast, simple, easy to handle, conducted in ambient conditions, and less demanding in terms of organic solvent.…”

Effects of Different Self-Assembled Monolayers on Thin-Film Morphology: A Combined DFT/MD Simulation Protocol

“…Lee et al as well as Porzio et al showed how SAMs with different chain lengths affect differently the OTFT performances. Other groups − showed how different fabrication techniques and experimental conditions affect the quality of a SAM, thus influencing the device performances. Moreover, recent computational studies involving molecular dynamics (MD) simulations were able to clarify the mechanisms of self-assembly and ordering of organic molecules on different SAM surfaces. − …”

Remote Doping Effects of Indium–Gallium–Zinc Oxide Thin-Film Transistors by Silane-Based Self-Assembled Monolayers

“…OTS (Sigma-Aldrich St. Louis, MO, USA) and ODTS (Sigma-Aldrich) have additional 8 and 18 carbon chains in trichlorosilane (HCI 3 Si), respectively. We prepared 5 mL of a 1% v / v solution by mixing OTS and chlorobenzene (C 6 H 5 Cl) (Sigma-Aldrich) [ 26 ]. Moreover, ODTS was mixed using the same method with a 1% v / v concentration.…”