MOCVD Routes to Tl2Ba2Can-1CunO4+2nSuperconductor and Dielectric Insulator Thin Films

The 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. J c 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.