Lauren M. Tonge

Organometallic chemical vapor deposition of high Tc superconducting films using a volatile, fluorocarbon-based precursor

Uniform films of the high Tc superconductor YBa2Cu3O7−δ have been prepared by organometallic chemical vapor deposition using the volatile metalorganic precursors Cu(acetylacetonate)2, Y(dipivaloylmethanate)3, and Ba(heptafluorodimethyloctanedionate)2. With argon as a carrier gas and water vapor as a reactant, film growth rates of 10–30 nm/min are achieved. After annealing under oxygen, energy dispersive x‐ray analysis, profilometry, and x‐ray diffraction data reveal that such YBa2Cu3O7−δ films on [100] single‐crystal MgO have good compositional and dimensional uniformity as well as preferential orientation of crystallite c axes perpendicular to the substrate surface. Four‐probe resistivity measurements reveal the onset of superconductivity at ∼90 K and zero resistance by 66.2 K.

Organometallic chemical vapor deposition routes to high Tc superconducting Tl-Ba-Ca-Cu-O films

Films of the Tl‐Ba‐Ca‐Cu‐O high Tc superconductor can be prepared by either of two organometallic chemical vapor deposition routes. Ba‐Ca‐Cu‐O films are first prepared on yttria‐stabilized zirconia using the volatile precursors Ba(heptafluorodimethyloctanedionate)2, Ca(dipivaloylmethanate)2, and Cu(acetylacetonate)2. Deposition is carried out at 5 Torr pressure with argon as the carrier gas and water vapor as the reactant gas. Thallium is next incorporated in these films either by vapor diffusion using bulk Tl‐Ba‐Ca‐Cu‐O as the source, or by organometallic chemical vapor deposition using Tl(cyclopentadienide) as the source. The latter deposition is carried out at atmospheric pressure with an argon carrier and water‐saturated oxygen reactant, followed by rapid thermal annealing. Both types of films consist primarily of the TlBa2Ca2Cu3Ox phase, have preferential orientation of the CuO planes parallel to the substrate surface, and exhibit onset of superconductivity at ∼120 K with zero resistance by 100 K.

Organometallic chemical vapor deposition of high Tc superconducting Bi‐Sr‐Ca‐Cu‐O films

Films of the high Tc Bi‐Sr‐Ca‐Cu‐O superconductor have been prepared by organometallic chemical vapor deposition using the volatile metalorganic precursors Cu(acetylacetonate)2 , Sr(dipivaloylmethanate)2 , and Ca(dipivaloylmethanate)2, and triphenylbismuth. Deposition is carried out at 2 Torr with argon as the carrier gas and oxygen and water vapor as reactants. Film growth rates of 2–3 μm/h are achieved. After annealing under oxygen, energy dispersive x‐ray analysis and x‐ray diffraction data reveal that such films on [100] single‐crystal MgO consist predominantly of the Bi2(Sr,Ca)3Cu2Ox, Tc=85 K, phase and have preferential orientation of the crystallite c axes perpendicular to the substrate surface. Four‐probe resistivity measurements reveal the onset of film superconductivity at ∼110 K and zero resistance by 75 K.

Organometallic chemical vapor deposition of strontium titanate

SrTiO3 thin films were deposited by low‐pressure organometallic chemical vapor deposition. Titanium isopropoxide, Sr(dipivaloylmethanate)2, oxygen, and water vapor were used as reactants, and argon was used as a carrier gas. Growth rates ranging from 0.3 to 4.5 μm/h were obtained on (0001) sapphire substrates at 600–850 °C. Highly textured SrTiO3 films with a [111] orientation were obtained at a growth temperature of 800 °C. The growth parameters which influenced the composition, phase stability, morphology, and texture of the thin films were examined.

Growth studies of ferroelectric oxide layers prepared by organometallic chemical vapor deposition

Abstract Low pressure organometallic chemical vapor deposition was used to prepare ferroelectric thin films. Both the bismuth and the strontium titanate system were investigated. Under the optimal growth conditions phase pure, textured films could be prepared. The growth parameters which influenced composition and phase stability were examined.

Organometallic chemical vapor deposition of high T/sub c/ superconducting Bi-Sr-Ca-Cu-O films

Films of the high Tc Bi‐Sr‐Ca‐Cu‐O superconductor have been prepared by organometallic chemical vapor deposition using the volatile metalorganic precursors Cu(acetylacetonate)2 , Sr(dipivaloylmethanate)2 , and Ca(dipivaloylmethanate)2, and triphenylbismuth. Deposition is carried out at 2 Torr with argon as the carrier gas and oxygen and water vapor as reactants. Film growth rates of 2–3 μm/h are achieved. After annealing under oxygen, energy dispersive x‐ray analysis and x‐ray diffraction data reveal that such films on [100] single‐crystal MgO consist predominantly of the Bi2(Sr,Ca)3Cu2Ox, Tc=85 K, phase and have preferential orientation of the crystallite c axes perpendicular to the substrate surface. Four‐probe resistivity measurements reveal the onset of film superconductivity at ∼110 K and zero resistance by 75 K.

Unusual band-filling and counterion ordering effects in a phthalocyanine molecular metal. Single crystal studies of Ni(Pc) (C104)y

The phthalocyanine molecular metal Ni(Pc) (C104)y, y=0.39−0.47 for most crystals, has been synthesized by electrocrystallization techniques. The structure of a crystal with y=0.42 consists of staggered (39.5°) Ni(Pc)+0.42 units stacked at 3.233(1) A separations and disordered, off-axis C10-4 ions. At lower temperatures, the C10-4 ions undergo a transition to an ordered arrangement. At 300°K, σ‖=700±200Ω-1 cm-1 with metal-like (dσ/dT<0) behavior as the temperature is lowered. A broad maximum in σ(T) is found near 200°K, with discontinuous conductivity behavior observed in all samples at lower temperatures. The cause appears to be domain wall phenomena associated with C104 ordering rather than macroscopic fracturing. Thermoelectric power data are also metal-like (S≈T) with no evidence of the aforementioned discontinuities. Room temperature values of S=20−35 μVK-1 are in accord with the relatively high degree of Ni(Pc)+ρ partial oxidation. Polarized single crystal reflectance data reveal a plasma edge, the high energy of which is also explicable in terms of the relatively high degree of partial oxidation. Analysis of the thermoelectric power and optical data yields, in both cases, a tight-binding bandwidth of ca. 1.5 eV.

Organometallic chemical vapor deposition of superconducting, high Tc Pb‐doped Bi‐Sr‐Ca‐Cu‐O thin films

Highly oriented films of the high Tc Bi‐Pb‐Sr‐Ca‐Cu‐O (BPSCCO)superconductor have been prepared by two organometallic chemical vapor deposition (OMCVD) approaches. In the first approach, Pb is introduced by alternate deposition of BSCCO and PbOx films using the volatile metalorganic precursors Cu(acetylacetonate)2, Sr(dipivaloylmethanate)2, Ca(dipivaloylmethanate)2, triphenyl bismuth, and tetraphenyl lead. In the second approach, Pb is incorporated into an OMCVD‐derived BSCCO film by vapor diffusion using PbO as the source. X‐ray diffractometry and scanning electron microscopy reveal that Pb doping significantly improves the crystalline orientation and the film morphology. Films deposited by both methods on [100] single‐crystal MgO consist predominantly of the Bi2(Sr,Ca)3Cu2Ox phase and have a high preferential orientation of the crystallite c axes perpendicular to the substrate surface. Four‐probe resistivity measurements indicate the onset of film superconductivity at ∼110 K and zero resistance by 80 K.

Low pressure organometallic chemical vapor deposition of high-Tc superconducting YBa2Cu3O7−δ films

Abstract High-Tc superconducting YBa2Cu3O7−δ films have been prepared by low-pressure organometallic chemical vapor deposition using Cu(acetylacetonate)2, Y(dipivaloylmethanate)3, and Ba(dipivaloylmethanate)2 as volatile metal-organic precursors. An argon carrier gas is employed and water vapor serves as the reactant. Film growth rates of 10–30 nm min-1 are achieved at a system pressure of 5 torr. After annealing under oxygen, the YBa2Cu3O7−δ films deposited on SrTiO3 exhibit excellent compositional and structural uniformity in addition to preferential orientation of crystalline c axes perpendicular to the SrTiO3 surface. The onset of superconductivity is at ca. 90 K and zero resistance is achieved by 47 K.

Formation of oriented high Tc superconducting Bi‐Sr‐Ca‐Cu‐O thin films on silver substrates by organometallic chemical vapor deposition

Highly oriented thin films of the high Tc Bi‐Sr‐Ca‐Cu‐O superconductor have been deposited on silver substrates by low‐pressure organometallic chemical vapor deposition. The volatile metalorganic complexes Cu(acetylacetonate)2, Sr(dipivaloylmethanate)2, Ca(dipivaloylmethanate)2, and triphenyl bismuth are used as precursors with N2O as a reactant gas. X‐ray diffraction measurements reveal that the films deposited at 625 °C contain a mixture of the Bi2(Sr,Ca)2CuOx and Bi2(Sr,Ca)3Cu2Ox phases. The post‐annealed films are predominantly composed of the Bi2(Sr,Ca)3Cu2Ox phase with preferential orientation of the crystallite c axes perpendicular to the substrate surface. Magnetic susceptibility measurements indicate the superconducting onset temperature of the annealed films to be at 80 K. The zero‐field critical current density, estimated from magnetization measurements, is ∼3.9×105 A/cm2 at 5.5 K.