Electrodeposition of lithium phthalocyanine thin films: Part I. Structure and morphology
- PDF / 629,955 Bytes
- 11 Pages / 612 x 792 pts (letter) Page_size
- 43 Downloads / 222 Views
MATERIALS RESEARCH
Welcome
Comments
Help
Electrodeposition of lithium phthalocyanine thin films: Part I. Structure and morphology M. Brinkmanna) and S. Graff Institut Charles Sadron, 6 rue Boussingault, 67083 Strasbourg Cedex, France
C. Chaumont Institut de Physique et de Chimie des Mat´eriaux de Strasbourg, Groupe des Mat´eriaux Inorganiques (GMI), 23 rue du Loess, 67037 Strasbourg Cedex, France
J-J. Andr´e Institut Charles Sadron, 6 rue Boussingault, 67083 Strasbourg Cedex, France (Received 9 March 1998; accepted 14 October 1998)
A new thin film synthesis route based on the electrochemical oxidation of PcLi2 and deposition of lithium phthalocyanine (PcLi) onto indium tin oxide (ITO) substrate is demonstrated. The effects on the thin film morphology of various parameters such as the electrolysis time, the nature of the solvent, and the oxidation potential are investigated. The thin film growth is studied via x-ray diffraction, potential step experiments, and ex situ scanning electron microscopy. Various morphologies of the x-form thin films are observed for different electrolysis times and solvents. Thin films grown in acetonitrile of thickness above 1 mm consist in unidirectionally oriented needle-shaped crystallites.
I. INTRODUCTION
Phthalocyanines are versatile materials widely used in the dye industry and are easily handled to design electronic devices via vacuum sublimation.1 Among all the undoped and unsubstituted phthalocyanines, the lithium phthalocyanine (PcLi) is a stable neutral radical and one of the few intrinsic molecular semiconductors crystallizing in at least three different structures (the x, the a, and the b structures). The optical, magnetic, and structural properties of PcLi have been extensively studied in solution2 and in the solid state for the x structure (powders and single crystals).3–5 In particular, electron spin resonance (ESR) studies have shown that the extremely narrow ESR signal in x-form powders under vacuum (DH1/2 , 20 mG in single crystals) is broadened proportionally to the dioxygen pressure (dDH1/2y dP(O2 ) , 5Gybar), suggesting the possibility to design oxygen sensors based on x-form PcLi thin films. Several works6,7 have paid attention to the peculiar polymorphism of PcLi in thin films and powders which affects, among other properties, its sensitivity to the presence of O2 . In the case of powders and single crystals, various synthetic routes have been proposed. The x structure of PcLi is obtained through electrochemical oxidation of PcLi2 and the a structure via reduction of phthalodinitrile.3,8 The two structures evidenced in powders and thin films are (i) the PcLi x polymorph
a)
Address all correspondence to this author. Present address: ISM-CNR, 101 via Gobetti, 40129 Bologna, Italy. e-mail: [email protected]
2162
http://journals.cambridge.org
J. Mater. Res., Vol. 14, No. 5, May 1999
Downloaded: 14 Mar 2015
which shows a tetragonal unit cell with parameters a b 1.385 nm, c 0.65 nm, and space group P4ymcc9 and (ii) the a structure of PcLi w
Data Loading...
