Electrochemical investigation on adsorption kinetics of long chain alkylsilanes and influence of solvents on their self-
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RESEARCH ARTICLE
Electrochemical investigation on adsorption kinetics of long chain alkylsilanes and influence of solvents on their self‑assembly and electron transfer behavior on indium tin oxide R. Venkata Jagadeesh1 · V. Lakshminarayanan2 Received: 15 May 2020 / Accepted: 17 August 2020 © Springer Nature B.V. 2020
Abstract In situ adsorption kinetics of hexadecyltrimethoxy silane (HDTMS) and octadecyltrimethoxy silane (ODTMS) on indium tin oxide (ITO) surface at short time intervals were measured by electrochemical impedance (EIS) spectroscopy technique at constant frequency. The studies suggest that, self-assembly of silanes on ITO proceeds through two distinct adsorption steps, a fast first step followed by a slower second step. The inhibition of electron transfer by self-assembled silanes prepared in ethanol, toluene and hexane solvents were evaluated by cyclic voltammetry (CV) and EIS using [Fe(CN)6]3−/4− and [Ru(NH3)6]3+/2+ redox species. It is shown that, the quality of silane films are influenced by the polarity of solvent, chain length of silane and ITO substrate–solvent interactions. The effect of annealing on electron transfer barrier property of silane monolayers after their formation were studied. The pinhole characteristics of silane films on ITO prepared from various solvents under study were measured using EIS. This study demonstrates a strategy of producing an ultra-smooth and closepacked silane films on ITO surfaces which can have potential applications towards high performance organic electronics.
* R. Venkata Jagadeesh [email protected] 1
Department of Electronic Systems Engineering, Indian Institute of Science, Bangalore 560012, India
Soft Condensed Matter Group, Raman Research Institute, Bangalore 560080, India
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13
Vol.:(0123456789)
Journal of Applied Electrochemistry
Graphic Abstract
Keywords Long chain silane · Adsorption kinetics · Pinhole analysis · Double layer capacitance · Solvent effect
1 Introduction Self-assembled monolayers (SAMs) of silane molecules on metal and oxide surfaces are of particular interest owing to their widespread interest of these materials in electronics industry [1, 2]. SAMs of closely-packed, well-ordered, compact and ultra-smooth crystalline hydrophobic silanes are essential for fabrication of high performance organic semi-conductors, organic field-effect transistor (OFETs) and organic thin-film transistors (OTFTs) [3]. It is very wellknown that, the underlying dielectric layer has the ability to reduce the surface energy, diffusion, charge mobility and aggregation of the conducting layer in transistors and field effect transistors (FETs) [4, 5]. Presence of grain boundaries, defects and pinholes in SAM may result in exposure of the surface hydroxyl groups, which are responsible for deterioration of the performance of electronics by trapping water molecules [6]. Thus, highly hydrophobic surfaces which are free of pinholes and defects are desirable. Devnyck et al. observed an increase in charge mobility (0.74 cm2 V−1 s−1) of pentac
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