Nanoscale molecular patterning on artificially fabricated nanoscale structured Al surfaces
Kato, Hitoshi; Takemura, Susumu; Kimura, Shogo; Okumura, Takayuki; Kobayakawa, Daisuke; Watanabe, Yohei; Sugiyama, Takeharu; Hiramatsu, Tomoyasu; Nanba, Noriyuki; Nishikawa, Osamu; Taniguchi, Masahiro
Japan

The surface of an Al plate was treated with a combination of chemically and electrochemically processes. Two types of chemical treatment were conducted. One was an acetone cleansing process under supersonic and the other was Semi Clean cleansing. The creation of two types of characteristic surface structures (crater-type, line-type) according to the chemical processes was demonstrated after those surface treatments. Successive electrochemical process by applying DC voltage to the Al plate in H2SO4 solution created more ordered and finer nanostructures. One was a uniformly extended scale-structure formed by linked-craters. The other was a highly oriented line-structure. Dynamic force microscopy (DFM) measurement clarified that the nanoscale highly oriented line-structure and the fine scale structures were created on Al surface by the successive electrochemical process. The line distance was estimated approximately 30-40 nm by the cross section analysis of the Al surface in the case of the line-structure. In the case of the fine scale-structure, the diameter of each crater was estimated as 50-100nm. The authors intended to make molecular patterning with a nanoscale size on the highly oriented line-structure and the fine scale-structure. Copper phthalocyanine (CuPc) was selected because of its unique electronic and optical properties. Highly-functional molecules CuPc molecules were put on the nanoscale structure by casting a toluene droplet containing CuPc. A molecular patterning was demonstrated by DFM and X-ray photoemission spectroscopy (XPS). In the case of the highly oriented line-structure, the DFM cross section analysis on pre-deposited and deposited surfaces clarified that the depth of the row became shallow and in some area the row width became narrower after CuPc deposition. Thus, CuPc molecules were filled in the channel. N 1s and Cu 2p core-level lines appeared after CuPc deposition. C 1s spectrum was composed of two peaks which was characteristic to CuPc. Spectral profiles of each peak differed between pre-deposited and deposited samples which reflected the molecular-surface binding states.
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