Functionalization of Indium Tin Oxide

Abstract

The preparation and functionalization of ITO surfaces has been studied using primarily X-ray photoemission spectroscopy and infrared reflection-absorption spectroscopy (IRRAS) and the reagents n-hexylamine and n-octyltrimethoxysilane (OTMS). Particular attention has been paid to characterization of the surfaces both before and after functionalization. Surfaces cleaned by ultraviolet (UV)/ozone treatment and subsequently exposed to room air have approximately 0.5-0.8 monolayers (ML) of adsorbed impurity C. Most is in the form of aliphatic species, but as much as one-half is partially oxidized and consists of C-OH, C-O-C, and/or >C=O groups. The coverage of these species can be reduced by cleaning in organic solvents prior to UV/ozone treatment. The OH coverage on the ITO surfaces studied here is relatively small (approximately 1.0 OH nm-2), based on the Si coverage after reaction with OTMS. A satellite feature in the O 1s XPS spectrum, often suggested to be a quantitative measure of adsorbed OH, receives a significant contribution from sources not directly related to hydroxylated ITO. n-Hexylamine adsorbs, at a saturation coverage of approximately 0.08 ML, via a Lewis acid-base interaction. The particular acid site has not been conclusively identified, but it is speculated that surface Sn sites may be involved. For OTMS, a saturation coverage of about 0.21 ML is found, and the C/Si atom ratios suggest that some displacement of preadsorbed organic impurities occurs during adsorption. The alkyl chain of adsorbed OTMS is disordered, with no preferred stereoisomer. However, the chain appears to lie mainly parallel to the surface with the plane defined by the terminal CH3-CH2-CH2- segment oriented essentially perpendicular to the surface.

Efficient Chemisorption of Organophosphorous Redox Probes on Indium Tin Oxide Surfaces under Mild Conditions

“…It is worth noting that such a high doping level of ITO is in agreement with the data provided by the supplier, i.e., 10−20% SnO 2 doping level, but also with values reported by other groups on commercial ITO samples. 37 Both of the In 3d 5/2 and a Sn 3d 5/2 highresolution peaks were fitted with three components (Table S2): a main one at low energy values (444.5 and 486.6 eV, respectively), corresponding to the bulk oxide, and a second one associated with surface hydroxide groups at 445.2 and 487.2 eV. 38 A standard deviation of 0.1 eV of the binding energy is obtained among the different ITO samples.…”

Modification of ITO surface using aromatic small molecules with carboxylic acid groups for OLED applications

“…This is a significant advantage to create a strong covalent bond, since the surface hydroxyl content of ITO is notoriously low (approximately 1 OH nm 2 ) [33,34]. The bonding carboxylic acid group of MPPBA molecule on ITO is illustrated in Fig.…”

Dopant and Defect Induced Electronic States at In2O3 Surfaces

“…Although the influence of plasmons or final state screening on core XPS of ITO and related materials is now gaining acceptance in the literature [187,[207][208][209], some papers published since 2,000 have questioned the importance of these effects [186,210]. Indeed the very existence of low energy conduction electron plasmons in ITO has been called into question [186]-a standpoint that is very difficult to understand given the pivotal importance of plasmons in determining the optical properties of ITO.…”