Effect of Self-Assembled Monolayer Modification on Indium--Tin Oxide Surface for Surface-Initiated Vapor Deposition Polymerization of Carbazole Thin Films

With the aim of controlling the interface between an inorganic electrode and an organic layer, a surface-initiated vapor deposition polymerization method was employed to prepare carbazole polymer thin films that are chemically bound to an indium--tin oxide (ITO) surface. A self-assembled monolayer (...

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Published inJapanese Journal of Applied Physics Vol. 49; no. 4; pp. 04DK21 - 04DK21-5
Main Authors Umemoto, Yuya, Kim, Seong-Ho, Advincula, Rigoberto C, Tanaka, Kuniaki, Usui, Hiroaki
Format Journal Article
LanguageEnglish
Published The Japan Society of Applied Physics 01.04.2010
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Summary:With the aim of controlling the interface between an inorganic electrode and an organic layer, a surface-initiated vapor deposition polymerization method was employed to prepare carbazole polymer thin films that are chemically bound to an indium--tin oxide (ITO) surface. A self-assembled monolayer (SAM) that has an azo initiator as a terminal group was prepared on an ITO surface, on which carbazole acrylate monomers were evaporated under ultraviolet (UV) irradiation. The surface morphological characteristics of the films prepared with/without UV irradiation and with/without the SAM were compared. It was found that the UV irradiation leads to the polymerization of carbazole monomers irrespective of the type of substrate used. On the other hand, the surface morphological characteristics were largely dependent on the existence of the SAM. Uniform and smooth polymer thin films were obtained only when the monomers were evaporated on the SAM-modified surface under UV irradiation. A comparison of film growth characteristics on a UV--ozone-treated ITO surface suggested that the formation of uniform films was made possible not by the modification of surface energy but by the growth of the polymers chemically bound to the substrate surface.
Bibliography:Schematic diagram of the surface-initiated deposition polymerization process: (a) ITO substrate, (b) SAM formation process, (c) SAM-modified substrate, (d) vacuum chamber, (e) polymeric thin film, (f) thickness monitor, (g) evaporated monomers, (h) evaporator, (i) quartz window, (j) light guide, (k) shutter, and (l) high-pressure mercury lamp. Reaction scheme of surface-initiated deposition polymerization, involving (a) SAM formation and (b) vapor deposition polymerization. Surface morphology of CEA films deposited on bare ITO surface by (a) simple vapor deposition and (b) UV-assisted deposition. The scale bar indicates a length of 50 \mbox{$\mu$m}. IR spectra of CEA monomer (a) and the films deposited on gold surface without (b) and with (c) UV irradiation. The arrows indicate peak positions for 1: carbonyl C=O, 2: vinyl C=C stretching, 3: vinyl CH 2 in-plane deformation, 4: ester C--C--O, 5: ester O--C--C, 6: vinyl C--H in-plane deformation, and 7: vinyl C--H out-of-plane deformation. F 1s XPS spectra of the substrate surface before (a) and after (b) immersing in Vazo 56 during SAM preparation process. Surface morphology of CEA films deposited on SAM-modified ITO surface by (a) simple vapor deposition and (b) UV-assisted deposition. The scale bar indicates a length of 50 \mbox{$\mu$m}. Surface morphology of CEA film prepared by UV-assisted deposition on UV--ozone treated ITO. The scale bar indicates a length of 50 \mbox{$\mu$m}.
ISSN:0021-4922
1347-4065
DOI:10.1143/JJAP.49.04DK21