Synthesis and characterization of low-melting, highly volatile magnesium MOCVD precursors and their implementation in MgO thin film growth

A series of low-melting, highly volatile, and thermally/air stable diamine-coordinated magnesium metal-organic chemical vapor deposition (MOCVD) precursors, Mg(hfa) ₂(diamine) and Mg(hfa) ₃H(diamine) (hfa = 1,1,1,5,5,5-hexafluoro-2,4-pentanedionate), has been synthesized in a single-step aqueous reaction under ambient conditions, and the molecular structures have been determined by single-crystal X-ray diffraction. These fluorocarbon-bearing magnesium complexes exhibit significantly lower melting points and higher volatilities than most previously reported magnesium precursors for MgO thin film growth. One complex of the series, bis(1,1,1,5,5,5-hexafluoro-2,4-pentanedionato)(N,N,N′, N′-tetramethylethyl-enediamine)magnesium(II), with a low melting point (61°C) and excellent volatility, was successfully implemented in MgO thin film growth by MOCVD. Phase-pure MgO thin films were deposited on Corning 1737F glass, single-crystal Si, and single-crystal SrTiO ₃(100) and -(110), over the temperature range 550-675°C. It is demonstrated that highly (100)-oriented MgO films can be obtained on amorphous glass (X-ray diffraction fwhm = 3.1°). Compared to films on glass, epitaxial MgO thin films on both SrTiO ₃ substrates exhibit excellent out-of-plane alignment (fwhm = 0.7 and 0.9°) and good in-plane alignment. The microstructures, surface morphologies, and optical properties of the MgO thin films were also investigated as a function of growth temperature.