Michael P. Chudzik

Charge transport, optical transparency, microstructure, and processing relationships in transparent conductive indium–zinc oxide films grown by low-pressure metal-organic chemical vapor deposition

Indium–zinc oxide films (ZnxInyOx+1.5y), with x/y=0.08–12.0, are grown by low-pressure metal-organic chemical vapor deposition using the volatile metal–organic precursors In(TMHD)3 and Zn(TMHD)2 (TMHD=2,2,6,6–tetramethyl–3,5–heptanedionato). Films are smooth (rms roughness=40–50 A) with complex microstructures which vary with composition. The highest conductivity is found at x/y=0.33, with σ=1000 S/cm (n-type; carrier density=3.7×1020 cm3; mobility=18.6 cm2/V s; dσ/dT<0). The optical transmission window of such films is broader than Sn-doped In2O3, and the absolute transparency rivals or exceeds that of the most transparent conductive oxides. X-ray diffraction, high resolution transmission electron microscopy, microdiffraction, and high resolution energy dispersive X-ray analysis show that such films are composed of a layered ZnkIn2O3+k phase precipitated in a cubic In2O3:Zn matrix.

Buffers for high temperature superconductor coatings. Low temperature growth of CeO2 films by metal–organic chemical vapor deposition and their implementation as buffers

Abstract Smooth, epitaxial cerium dioxide thin films have been grown in-situ in the 450–650°C temperature range on (001) yttria-stabilized zirconia (YSZ) substrates by metal–organic chemical vapor deposition (MOCVD) using a new fluorine-free liquid Ce precursor. As assessed by X-ray diffraction, transmission electron microscopy (TEM), and high-resolution electron microscopy (HREM), the epitaxial films exhibit a columnar microstructure with atomically abrupt film-substrate interfaces and with only minor bending of the crystal plane parallel to the substrate surface near the interface and at the column boundaries. With fixed precursor temperature and gas flow rate, the CeO 2 growth rate decreases from ∼10 A/min at 450°C to ∼6.5 A/min at 540°C. The root-mean-square roughness of the films also decreases from 15.5 A at 450°C to 4.3 A at 540°C. High-quality, epitaxial YBa 2 C 3 O 7− x films have been successfully deposited on these MOCVD-derived CeO 2 films grown at temperatures as low as 540°C. They exhibit T c =86.5 K and J c =1.08×10 6 A/cm 2 at 77.4 K.

Transmission electron microscopy investigation of texture development in magnesium oxide buffer layers

Biaxially textured magnesium oxide (MgO) buffer layers were grown by inclined substrate deposition and examined before YBa/sub 2/Cu/sub 3/O/sub 7-x/ deposition to optimize their texture. Transmission electron microscopy of buffer layers in both cross-sectional and plan view was used to investigate film microstructure and texture development as a function of deposition thickness (0.05-3 /spl mu/m) and substrate inclination angle (0-55/spl deg/ from the substrate normal). It was determined that the combined effects of preferential growth of the {200} equilibrium crystal habit of MgO and shadowing by columnar grains led to the development of off-axis [200]-textured films.

High-rate reel-to-reel continuous coating of biaxially textured magnesium oxide thin films for coated conductors☆

Biaxially textured thin films of magnesium oxide (MgO) were deposited by electron beam evaporation at deposition rates of 0.6 {mu}m/min on moving Ni-based alloy tapes as oriented buffer layers for coated conductors. Moving substrates were inclined with respect to the atomic vapor and translated through collimated dual vapor sources. Growth anisotropy in the MgO and self-shadowing effects due to the inclined angle combine to create biaxial texture in the deposited thin films. MgO films grown to a thickness of 2.0 {mu}m with this inclined-substrate deposition technique have yielded in-plane textures of 10--12{degree} fill-width half-maximum (FWHM). Results of a parametric study on the in-plane texture in short-length static-mode samples are presented, along with preliminary results of long-length samples deposited under translating conditions.

Efficient route to TlBa2Ca2Cu3O9+x thin films by metal-organic chemical vapor deposition using TlF as a thallination source

Thin TlBa2Ca2Cu3O9+x films were grown on single crystal (110) LaAlO3 from metal-organic chemical-vapor deposition-derived Ba–Ca–Cu–Ox precursor films employing Ba(hfa)2⋅mep, Ca(hfa)2⋅tet, and Cu(dpm)2 (hfa=hexafluoroacetylacetonate; dpm=dipivaloylmethanate; tet=tetraglyme; mep=methylethylpentaglyme) as the volatile metal sources. Thallination is then accomplished by annealing the precursor films in the presence of a bulk BaO+CaO+CuO+TlF source at 885 °C in flowing O2. The presence of TlF is essential for nucleating the Tl-1223 phase. The resulting Tl-1223 films are nearly phase-pure, highly oriented, epitaxial by x-ray diffraction, and contain negligible fluoride by windowless energy-dispersive x-ray measurements. The films exhibit a transport measured Tc=103 K and Jc=4.4×104 A/cm2 (77 K, 0 T). Magnetic hysteresis measurements yield Jc=1.9×105 A/cm2 (30 K, 0.01 T) and show considerable flux pinning at low temperatures with Jc=1.4×105 A/cm2 (5 K, 4.5 T).

Metal-organic chemical vapor deposition routes to films of transparent conducting oxides

This contribution reports the in situ growth of transparent, conducting Ga x In 2-x O 3 and Zn k In 2 O k+3 films by MOCVD (metal-organic chemical vapor deposition) techniques using In(dpm) 3 , Ga(dpm) 3 , and Zn(dpm) 2 (dpm = dipivaloylmethanate) as volatile precursors. In the former series, film microstructure in the x = 0.4 – 1.0 range is predominantly cubic with 25° C electrical conductivities as high as 1300 S/cm (n-type; carrier density = 1.2 × 10 20 cm −3 , mobility = 68 cm 2 /Vs) and optical transparency in the visible region greater than that of ITO. In the latter series, films in the composition range K = 0.16 – 3.60 were studied; the microstructural systematics are rather complex. Electrical conductivities (25° C) as high as 1000 S/cm (n-type; carrier density = 3.7 × 10 20 cm −3 , mobility = 18.6 cm 2 /Vs) for K = 0.66 were measured. The optical transparency window is significantly broader than that of ITO.

Novel Metal-Organic Chemical Vapor Deposition / T1F Annealing Route to Thin Films of Tl1Ba2Ca2Cu3O9+x

Thin films of TI1Ba2Ca2Cu3O9+x have been grown on single crystal (110) LaAlO3 by a metal-organic chemical vapor deposition process employing Ba(hfa)2.mep, Ca(hfa)2.tet. and Cu(dpm)2 (hfa = hexafluoroacetylacetonate; dpm = dipivaloylmethanate; tet = tetraglyme; mep =methylethylpentaglyme) as the volatile metal sources. A subsequent phase-selective annealing procedure accomplishes thallination using TIF in a bulk oxide pellet. The resulting films are nearly phase-pure and highly oriented and contain negligible fluoride by windowless energy-dispersive x-ray measurements. The films exhibit transport measured Tc = 103 K and Jc > 104 A/cm2 (77 K. 0 T) and at low temperatures retain Jc > 105 A/cm2 (5 K, 4.5 T) as measured by magnetic hysteresis.