Synthesis and characterization of volatile liquid Mo precursors for vapor phase deposition of thin films containing molybdenum

Abstract

Volatile molybdenum precursors in liquid phase for vapor phase deposition of thin films containing molybdenum have been successfully synthesized. Heteroleptic liquid molybdenum precursors were prepared by treating MoCl5 with bidentate β-ketonate ligands such as 2,2,6,6-Tetramethyl-3,5-heptanedione (thdH) at different stoichiometric ratios (1:1 and 1:2). Molybdenum precursors in liquid phases also have been obtained via simple ligand-exchange reactions of Mo(thd)xCl4-x (x = 1 or 2) with LiNR2 (R = Et(C2H5), iPr(C3H7), SiMe3(Si(CH3)3)). The newly synthesized molybdenum precursors are readily miscible (soluble) in most organic solvents, such as acetonitrile, diethyl ether, and hexane. The chemical composition of these precursors has been characterized using Fourier-transform infrared analysis and nuclear magnetic resonance spectroscopy. The volatility and thermal stability of precursor compounds have also been investigated using thermogravimetric analysis and vapor pressure measurement. The strategy used in this experiment, which introduces bidentate ligands to the coordination sphere of the central molybdenum atom in MoCl5, improves the volatility and transferability of molybdenum precursors in gas-phase deposition processes by making them in a liquid phase.