Organosoluble Silicon and Germanium Nanoclusters

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1113-F08-08

Organosoluble Silicon and Germanium Nanoclusters Akira Watanabe and Tokuji Miyashita Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai 980-8577, Japan ABSTRACT The organosilicon nanoclusters (OSI) and organogermanium nanocluster (OGE) which have a few nanometer sized silicon or germanium cluster and organic groups bonded to the nanocluster surfaces show solubility in common organic solvents and good film processability by solution coating method. Using the coating films as precursors, inorganic silicon and germanium films were prepared by heat treatment in vacuo and laser annealing. The structural changes of the Si and Ge skeletons of the OSI and OGE by heat treatment and laser annealing were investigated by Raman spectroscopy. The laser-annealed films showed Raman bands assigned to the polycrystalline structure. The micropatterning of polycrystalline Ge by laser direct writing method was demonstrated. The organosoluble OGE is expected to be applicable as a germanium ink which gives polycrystalline Ge film. INTRODUCTION Recently, solution processing using novel nanomaterials attracts more and more interests toward printable and flexible electronic devices and large area electronic devices based on a low cost process. Although silicon and germanium are fundamental elements in the electronic devices, there are few reports on the organosoluble silicon and germanium clusters. In previous papers, we have reported the syntheses and optical and electrical properties of organosilicon and germanium nanoclusters which have a few nanometer sized silicon or germanium cluster and organic groups bonded to the nanocluster surfaces [1-12]. The OSI and OGE are synthesized by solution phase reactions of silicon or germanium tetrachlorides (Figure 1). The first stage of the reaction is the condensation of the tetrachloride in a solution using Mg metal and the formation of nanoclusters dispersed Cl R R Mg R-Br Organosilicon in the solution. The Cl Si Cl Nanocluster (OSI) in THF M M 50oC second stage of the Cl M M M M R reaction is the surface Cl Mg R-Br modification of the nanoOrganogermanium M M Cl Ge Cl Nanocluster (OGE) in THF clusters by organic subo 50 C R R Cl stituents to solubilize the R: organic group, THF: tetrahydrofuran M = Si, Ge nanoclusters into the solution. The OSI and OGE Figure1. Syntheses of OSI and OGE in solution. have possibilities as silicon and germanium inks because of the solubility in common organic solvents. The films of organosoluble silicon and germanium nanoclusters can be applicable to precursors of inorganic Si and Ge [2-6]. The image of the formation of inorganic films using OSI and OGE is schematically illustrated in Figure 2. The precursor film is prepared on a sub-

strate by solution coating method. The organic groups are eliminated from the Si or Ge cluster core by heat treatment or laser irradiation accompanying the reconstruction of the Si or Ge skeletons. The inorganic films can be crystallized by laser annealing. In this paper, we studied

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