Thin films for superconducting electronics: Precursor performance issues, deposition mechanisms, and superconducting phase formation-processing strategies in the growth of Tl2Ba2CaCu2O8 films by metal-organic chemical vapor deposition

Bruce J. Hinds, Richard J. McNeely, Daniel B. Studebaker, Tobin J Marks, Timothy P. Hogan, Jon L. Schindler, Carl R. Kannewurf, Xiao Feng Zhang, Dean J. Miller

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Abstract

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).

Original languageEnglish
Pages (from-to)1214-1236
Number of pages23
JournalJournal of Materials Research
Volume12
Issue number5
Publication statusPublished - May 1997

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Organic Chemicals
Organic chemicals
metalorganic chemical vapor deposition
Chemical vapor deposition
Electronic equipment
Metals
Film growth
Thin films
Vapor pressure
thin films
Processing
electronics
Substrates
Deposition rates
vapor pressure
Surface resistance
Temperature
Wave transmission
Epitaxial films
Growth temperature

ASJC Scopus subject areas

  • Materials Science(all)

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Thin films for superconducting electronics : Precursor performance issues, deposition mechanisms, and superconducting phase formation-processing strategies in the growth of Tl2Ba2CaCu2O8 films by metal-organic chemical vapor deposition. / Hinds, Bruce J.; McNeely, Richard J.; Studebaker, Daniel B.; Marks, Tobin J; Hogan, Timothy P.; Schindler, Jon L.; Kannewurf, Carl R.; Zhang, Xiao Feng; Miller, Dean J.

In: Journal of Materials Research, Vol. 12, No. 5, 05.1997, p. 1214-1236.

Research output: Contribution to journalArticle

Hinds, Bruce J. ; McNeely, Richard J. ; Studebaker, Daniel B. ; Marks, Tobin J ; Hogan, Timothy P. ; Schindler, Jon L. ; Kannewurf, Carl R. ; Zhang, Xiao Feng ; Miller, Dean J. / Thin films for superconducting electronics : Precursor performance issues, deposition mechanisms, and superconducting phase formation-processing strategies in the growth of Tl2Ba2CaCu2O8 films by metal-organic chemical vapor deposition. In: Journal of Materials Research. 1997 ; Vol. 12, No. 5. pp. 1214-1236.
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abstract = "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).",
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N2 - 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).

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