Synthesis and Characterization of Low-Melting, Highly Volatile Magnesium MOCVD Precursors and Their Implementation in MgO Thin Film Growth Lian Wang, Yu Yang, Jun Ni, Charlotte L. Stern, and Tobin J. Marks* Department of Chemistry and the Materials Research Center, Northwestern UniVersity, EVanston, Illinois 60208-3113 ReceiVed June 10, 2005. ReVised Manuscript ReceiVed July 17, 2005 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) 3 H(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. Introduction Magnesia, MgO, is used extensively in the insulating and buffer layers of multilayer electronic/photonic devices due to its very large band gap (7.2 eV), excellent thermal stability (melting point ) 2900 °C), electrical insulating properties (dielectric constant ) 9.8), and the tendency to form films with highly MgO(100)-oriented textured microstructures, benefiting from the simple cubic rock-salt crystal structure. 1-6 Highly biaxial-textured MgO thin films have been success- fully deposited by ion beam-assisted deposition (IBAD) and employed as template/buffer layers for YBCO supercon- ducting coatings, to facilitate templating processes, block electrical crosstalk, and minimize interfacial diffusion and lattice mismatches. 7,8 Textured MgO thin films are also commonly used to improve the thin film crystallinity in magnetic storage media at reduced substrate cost. 9,10 Single- crystal MgO wafers are excellent substrates for epitaxial thin film growth owing to the favorable surface conditions, propagating the desired microstructural texture from the substrate to the films. 11,12 In addition, MgO thin films, with superb refractory properties and low sputtering rates, play an important role as protective layers to ameliorate discharge characteristics and panel lifetime deficiencies in ac-plasma display panels. 13-15 To date, MgO thin films have been deposited by several techniques, including sol-gel, 3,13,16,17 sputtering, 14,18,19 pulsed laser deposition (PLD), 2 ion beam-assisted deposition (IBAD), 7,8,15 and chemical vapor deposition (CVD). 20-24 Among these techniques, metal-organic chemical vapor (1) Huang, R.; Kitai, A. H. Appl. Phys. Lett. 1992, 61, 1450-1452. (2) Tarsa, E. J.; English, J. H.; Speck, J. S. Appl. Phys. Lett. 1993, 62, 2332-2334. (3) Yoon, J. G.; Kim, K. Appl. Phys. Lett. 1995, 66, 2661-2663. (4) Zeng, J. M.; Wang, H.; Shang, S. X.; Wang, Z.; Wang, M. J. Cryst. Growth 1996, 169, 474-479. (5) Nam, K. H.; Han, J. G. Surf. Coat. Technol. 2003, 171, 51-58. (6) Chen, X. Y.; Wong, K. H.; Mak, C. L.; Yin, X. B.; Wang, M.; Liu, J. M.; Liu, Z. G. J. Appl. Phys. 2002, 91, 5728-5734. (7) Wang, C. P.; Do, K. B.; Beasley, M. R.; Geballe, T. H.; Hammond, R. H. Appl. Phys. Lett. 1997, 17, 2955-2957. (8) Brewer, R. T.; Atwater, H. A. Appl. Phys. Lett. 2002, 80, 3388-3390. (9) Lee, L. L.; Cheong, B. K.; Laughlin, D. E.; Lambeth, D. N. Appl. Phys. Lett. 1995, 67, 3638-3640. (10) Kang, K.; Zhang, Z. G.; Papusoi, C.; Suzuki, T. Appl. Phys. Lett. 2004, 84, 404-406. (11) Jin, S.; Yang, Y.; Medvedeva, J. E.; Ireland, J. R.; Metz, A. W.; Ni, J.; Kannewurf, C. R.; Freeman, A. J.; Marks, T. J. J. Am. Chem. Soc. 2004, 126, 13787-13793. (12) Metz, A. W.; Ireland, J. R.; Zheng, J.-G.; Lobo, R. P. S. M.; Yang, Y.; Ni, J.; Stern, C. L.; Dravid, V. P.; Bontemps, N.; Kannewurf, C. R.; Poeppelmeier, K. R.; Marks, T. J. J. Am. Chem. Soc. 2004, 126, 8477-8492. (13) Jung, H. S.; Lee, J. K.; Hong, K. S.; Youn, H. J. J. Appl. Phys. 2002, 92, 2855-2860. (14) Lee, J. H.; Eun, J. H.; Park, S. Y.; Kim, S. G.; Kim, H. J. Thin Solid Films 2003, 435, 95-101. (15) Yu, Z. N.; Seo, J. W.; Zheng, D. X.; Sun, J. Surf. Coat. Technol. 2003, 163, 398-404. (16) Ho, I. C.; Xu, Y. H.; Mackenzie, J. D. J. Sol.-Gel Sci. Technol. 1997, 9, 295-301. (17) Chakrabarti, S.; Ganguli, D.; Chaudhuri, S. Mater. Lett. 2003, 57, 4483-4492. (18) Caceres, D.; Vergara, I.; Gonzalez, R. J. Appl. Phys. 2003, 93, 4300- 4305. (19) Cheng, Y. H.; Kupfer, H.; Richter, F.; Giegengack, H.; Hoyer, W. J. Appl. Phys. 2003, 93, 1422-1427. 5697 Chem. Mater. 2005, 17, 5697-5704 10.1021/cm0512528 CCC: $30.25 © 2005 American Chemical Society Published on Web 10/14/2005