Epitaxial Tl2Ba2CaCu2O8 thin films with excellent electrical transport characteristics are grown in a two-step process involving metal-organic chemical vapor deposition (MOCVD) of a BaCaCuO(F) thin film followed by a postanneal in the presence of Tl2O vapor. Vapor pressure characteristics of the recently developed liquid metal-organic precursors Ba(hfa)2 • mep (hfa = hexafluoroacetylacetonate, mep = methylethylpentaglyme), Ca(hfa)2 • tet (tet = tetraglyme), and the solid precursor Cu(dpm)2 (dpm = dipivaloylmethanate) are characterized by low pressure thermogravimetric analysis. Under typical film growth conditions, transport is shown to be diffusion limited. The transport rate of Ba(hfa)2 • mep is demonstrated to be stable for over 85 h at typical MOCVD temperatures (120 °C). In contrast, the vapor pressure stability of the commonly used Ba precursor, Ba(dpm)2, deteriorates rapidly at typical growth temperatures, and the decrease in vapor pressure is approximately exponential with a half-life of ∼9.4 h. These precursors are employed in a low pressure (5 Torr) horizontal, hot-wall, film growth reactor for growth of BaCaCuO(F) thin films on (110) LaAlO3 substrates. From the dependence of film deposition rate on substrate temperature and precursor partial pressure, the kinetics of deposition are shown to be mass-transport limited over the temperature range 350–650 °C at a 20 nm/min deposition rate. A ligand exchange process which yields volatile Cu(hfa)2 and Cu(hfa) (dpm) is also observed under film growth conditions. The MOCVD-derived BaCaCuO(F) films are postannealed in the presence of bulk Tl2Ba2CaCu2O8 at temperatures of 720–890 °C in flowing atmospheres ranging from 0–100% O2. The resulting Tl2Ba2CaCu2O8 films are shown to be epitaxial by x-ray diffraction and transmission electron microscopic (TEM) analysis with the c-axis normal to the substrate surface, with in-plane alignment, and with abrupt film-substrate interfaces. The best films exhibit a Tc = 105 K, transport-measured Jc= 1.2 × 105 A/cm2 at 77 K, and surface resistances as low as 0.4 mΩ (40 K, 10 GHz).
cm 3 in comparison to 1.8 g/cm 3 obtained for SiBCN 3 synthesized by polymer pyrolysis. High hardness values up to 22 GPa are found, which might be further increased by reducing the residual hydrogen content by applying higher bias potentials or by reduced precursor flow.Metal-organic chemical vapor deposition (MOCVD) is already an indispensable thin film growth technique for advancing microelectronics technologies, and it is predicted to play an even larger role in the future. [1] The inherent advantages of MOCVD (low growth temperatures, high continuous throughput, growth at high reactant gas pressures,
This communication reports rapid, efficient syntheses of the zirconium-organic metal-organic chemical vapor deposition (MOCVD) precursors Zr(acac)4 and Zr(dpm)4 (acac = acetylacetonate; dpm = dipivaloylmethanate) as well as a new, highly volatile, air- and moisture-stable Zr precursor based on a tetradentate Schiff-base ligand, Zr(tfacen)2 (tfacen = bis-trifluoroacetylacetone-ethylenediiminate). The improved one-step synthetic routes employ tetrakis(dimethylamido)zirconium as a common intermediate and represent a major advance over previous methods employing ZrCl4 or diketonate metathesis. Furthermore, Zr(tfacen)2 is shown to be an effective metal-organic precursor for the MOCVD-mediated growth of (100) oriented yttria-stabilized zirconia thin films.
T h e evolution of HTS device technologies will benefit fsorn the development 01' MOCVD (Metal-organic Chemical Vapor Deposition) routes to high quality HTS I'ilms as well as to those of insulators with low dielectric loss and close HTS lattice matches. Reviewed here are research efforts at precursor design focusing on Ba sources. A novel low pressure TGA technique is used to compare volatilities of MOCVD precursors and to quantif'y the role of' gas phase diffusion in film growth. TO form high quality T12Ba2Can-1C~1104+2n (n = 2.3) films, BaCaCuO(F) films are first deposited by MOCVD using the liquid precursors Ba(hl'ai?*rncp. Ca(hfa)2*tet, and solid Cu(dpm)2 (hfa = hexafluoroacetylacetonatc, clp~n = dipivaloyl~netha~iatc. mep = methylethyIpentaglyme, tet = tetraglyme). The film growth process is shown to he Inash transport-limited, and an interesting ligand exchange process is identified. The supei.conductu~; TBCCO phase is formed following an ex-situ anneal in the presence of T120 ar tentperau~i-cs from 820-900°C. Transport properties of TBCCO-2223 films include a Tc as high as I15K. Jc of 2x105 A/cm2 (77K), and Rs of 0.35mQ (5K, 10 GHz). The MOCVD growth of low loss, lattice-matched dielectric NdGa03, PrGa03, SrzAlTaOg, and SrPrGa04 f'il~ns is also discussed. High quality YBa2Cu307-, films have been grown upon MOCVD-dm-ived PsGaO? suhsri.a~cs.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.