Content area
Full Text
Anal Bioanal Chem (2013) 405:48954904 DOI 10.1007/s00216-013-6847-8
ORIGINAL PAPER
Chloroaluminum phthalocyanine thin films: chemical reaction and molecular orientation
Florian Latteyer & Heiko Peisert & Johannes Uihlein &
Tamara Basova & Peter Nagel & Michael Merz &
Stefan Schuppler & Thomas Chass
Received: 13 November 2012 /Revised: 13 February 2013 /Accepted: 14 February 2013 /Published online: 14 March 2013 # Springer-Verlag Berlin Heidelberg 2013
Abstract The chemical transformation of the polar chloroaluminum phthalocyanine, AlClPc, to -(oxo)bis (phthalocyaninato)aluminum(III), (PcAl)2O, in thin films on indium tin oxide is studied and its influence on the molecular orientation is discussed. The studies were conducted using complementary spectroscopic techniques: Raman spectroscopy, X-ray photoelectron spectroscopy, and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. In addition, density functional theory calculations were performed in order to identify specific vibrations and to monitor the product formation. The thin films of AlClPc were annealed in controlled environmental conditions to obtain (PcAl)2O. It is shown that the chemical transformation in the thin films can proceed only in the presence of water. The influence of the reaction and the annealing on the molecular orientation was studied with Raman spectroscopy and NEXAFS spectroscopy in total electron yield and partial electron yield modes. The comparison of the results obtained from these techniques allows the determination of the molecular orientation of the film as a function of the probing depth.
Keywords Interface/surface analysis . Thin films . Chloroaluminum phthalocyanine
Introduction
Phthalocyanines (Pcs) are of interest for a variety of opto-electronic devices, the commonest applications being field-effect transistors [1, 2], solar cells [3, 4], and light-emitting diodes [3]. The broad bandwidth for applications of Pcs results from their electronic and optical properties which can be tailored by chemical modifications. Substituents can be introduced at the peripheral positions or at the central atom. Substitution at the periphery, for example, with aliphatic [5, 6] or aromatic [7] moieties, induces, for example, liquid-crystalline properties, whereas substitution with oxygen [8, 9], chlorine [10, 11], or fluorine [12] at the central metal creates a permanent dipole moment. Moreover, sandwich complexes [1214] and annulated Pcs [15, 16] are known.
Polar Pcs have been investigated intensively recently. In contrast to the more familiar CuPc or ZnPc, the polar metal Pcs are not planar but are umbrella-like and tilted by...