Effects of surface chemical composition on the early growth stages of alpha-sexithienyl films on silicon oxide substrates.
In organic field effect transistors, charge transport is confined to a narrow region next to the organic/dielectric interface. It is thus extremely important to determine the morphology and the molecular arrangement of the organic films at their early growth stages. On a substrate of technological interest, such as thermally grown silicon oxide, it has been recently found that alpha-sexithienyl aggregates made of flat-lying molecules can simultaneously nucleate besides islands made of molecules standing vertical. In this paper, we investigate the effects due to variations in surface chemical composition on alpha-sexithienyl ultrathin film formation. Flat-lying molecules are no longer detected when Si-OH groups present at the surface are chemically removed but also when the Si-OH or Si-H group density is maximized. This gives evidence that variations in the surface chemical composition can largely affect the nucleation and growth processes of organic/dielectric interfaces. We hypothesize that isolated OH groups can interact with alpha-sexithienyl molecules and anchor them down flat with respect to the surface.
CNR - Istituto per lo Studio di Materiali Nanostrutturati, Bologna Division,Via P. Gobetti 101, I-40129 Bologna, Italy. f.dinelli@bo.ismn.cnr.it
Franco
F
Dinelli
Jean-François
JF
Moulin
Maria Antonietta
MA
Loi
Enrico
E
Da Como
Massimiliano
M
Massi
Mauro
M
Murgia
Michele
M
Muccini
Fabio
F
Biscarini
Jiang
J
Wie
Peter
P
Kingshott