AVS 59th Annual International Symposium and Exhibition
    Electronic Materials and Processing Thursday Sessions
       Session EM-ThP

Paper EM-ThP16
Small-Molecule Scaffolds for Directed Self-Assembly

Thursday, November 1, 2012, 6:00 pm, Room Central Hall

Session: Electronic Materials and Processing Poster Session
Presenter: P.L. Mancheno-Posso, University of Arizona
Authors: P.L. Mancheno-Posso, University of Arizona
A.J. Muscat, University of Arizona
Correspondent: Click to Email
Functionalization of oxide surfaces with vinyltrichlorosilane (VTCS, CH2=CH-SiCl3) was studied using water contact angle, ex situ ellipsometry, X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM). VTCS monolayers can be used as scaffolds for the deposition of a subsequent layer and keep it in close proximity to the surface due to its short length and terminal vinyl group. In this work, Si(100) samples were ultrasonically cleaned in acetone, methanol, and DI water for 5 min each. Native oxide was removed using a 1:100 (v/v) solution of 49% HF in water for 1 min. Subsequently, samples were hydroxylated with a 3:1 (v/v) solution of H2SO4 and H2O2 for 10 min at 60 °C. VTCS was adsorbed from 1:1000 (v /v) solutions in toluene, chloroform, and acetone. The layer thickness after 30 min in toluene was 47.5±6.4 Å, in chloroform 7.1±0.9 Å, and in acetone 4.0±1.9 Å. These results suggest acetone as the most appropriate solvent to produce a monolayer. The contact angle was near 0° on the piranha-treated surface and increased to 25.3±0.5° after VTCS adsorption. Addition of bromine atoms to the vinyl group was performed by immersing the samples in a 2% (v/v) solution of elemental bromine in dichloromethane for 2 hr. The contact angle was 63.2±3.9° after bromination. A Br 3d XPS peak at 70.0 eV (C-Br) demonstrated the chemical modification of the unsaturated bond of the VTCS molecule. AFM roughness analysis yielded an RMS value of 0.11 nm for the VTCS monolayer. The reaction of VTCS with hydroxyl groups at the surface was demonstrated on a thick hafnia layer by the presence of XPS peaks at 102.6 eV for Si 2p and 532.3 eV for O 1s, which correspond to Si-O bonds formed by VTCS and the substrate. Oxidation of the vinyl group with potassium permanganate (5 mM) and sodium periodate (195 mM) yielded a peak at 286.6 eV for C 1s, suggesting the formation of C-OH moieties.