Syntheses of Liquid Phase [(efac)Ag(P(OR)3)] Precursors and Their Application to the Preparation of Silver and Silver Selenide Thin Films

Recently, the preparation of silver metal thin films through chemical vapor deposition (CVD) has been a research field of particular interest due mainly to their wide variety of applications, such as contact materials in microelectronic circuitry, 1 components of high Tc superconductors, 2 bactericidal coatings, 3 and the development of electroluminescent materials. 4 A central issue in the typical low-pressure CVD process for the preparation of silver films has been the development of thermally stable silver precursors; a number of Ag precursors has been reported but they often showed low volatility and thermal and/or photochemical instability. Among them, silver β-diketonate phosphine adducts were interesting since phosphine ligands could function as both anti-oligomerization and deoxygenating agents. The incorporation of the ancillary ligands is believed to give rise to coordination saturation around silver metal and to prevent oligomerization reaction. Also, the phosphine ligands are well known to reduce oxygen contamination in silver films. But many of the phosphine compounds are pyrophoric or air sensitive. Accordingly, in this study, various phosphites were chosen as an ancillary ligand because they are relatively more stable and easy to handle. Besides, such phosphite ligands are expected to be better π acceptors than phosphine ligands, leading to more thermally stable silver complexes. Also, silver selenide thin films have been extensively studied because of their potential applications to superionic conductors, 5 solar cells, 6 thermochromic materials, and photosensitizers. 7 In this background, new phosphite adduct precursors of silver β-diketonate complexes were synthesized and characterized by various spectroscopic methods. Using them, silver metal films were deposited on glass or silicon substrates through MOCVD method. Then, those silver metal films were converted to Ag2Se film by selenium vapor deposition. Experimental Section