MEIS and ToF-SIMS analyses of organic ultrathin films for absolute quantification of functional groups

Abstract

Complementary use of medium-energy ion-scattering spectroscopy (MEIS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) analyses was proposed as a new methodology for absolute quantification of functional groups in organic ultrathin films. First, MEIS analysis was used to determine the absolute areal densities of Ru dye molecules in organic ultrathin films, which were made by spin coating Ru 535-bis TBA (C58H86O8N 8S2Ru) solutions with varying concentrations. The thicknesses of the films were less than 2 nm each and the densities of these ultrathin layers were linearly correlated with the solution concentrations. The determined absolute areal densities of the Ru organic molecules were then used to calculate the areal densities of the stoichiometric functional groups. Secondly, the ToF-SIMS intensities of the characteristic peaks such as Ru +, C16H35N+, CO2 -, CSN-, CSNRu-, etc, associated with the functional groups of a Ru 535-bis TBA molecule were correlated by the densities of the Ru organic molecules. Our results show that the correlation curves obtained through the complementary use of MEIS and ToF-SIMS techniques could be useful to quantify functional groups on organic ultrathin films. Copyright © 2010 John Wiley & Sons, Ltd.