SRF2011 - List of Authors (Gu, D.)

Paper	Title	Page
THPO044	Structural Characterization of Nb Films Deposited by ECR Plasma Energetic Condensation on Crystalline Insulators	819
	X. Zhao, H.L. Phillips, C.E. Reece, J.K. Spradlin, A-M. Valente-Feliciano JLAB, Newport News, Virginia, USA H. Baumgart, D. Gu ODU, Norfolk, Virginia, USA K.I. Seo NSU, Newport News, Virginia, USA
	Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. An energetic condensation thin film coating technique with an electron cyclotron resonance (ECR) induced plasma ion source is used to deposit Nb thin films on crystalline insulating substrates, such as a-plane and c-plane sapphire (Al2O3) and on magnesium oxide, MgO (100), (110), and (111). Heteroepitaxial Nb films were produced by ECR deposition with regulated substrate temperature. The residual resistance ratio (RRR) of about 1 micron thick films reach unprecedented values (350 - 450) on a-plane (11-20) sapphire substrates. The epitaxial relationship of Nb/crystalline substrate is found to be strongly influenced by the substrate bias voltage (adding to the initial Nb+ kinetic energy), the substrate crystalline orientation, and heating conditions. At low substrate temperature, the Nb films demonstrated non-epitaxial crystalline textures, revealed by XRD Pole Figure technique and Electron Backscattering Diffraction (EBSD). The texture might be caused by “Volmer-Weber” growth mode, i.e. island growth, at low surface adatom mobility. This study shows that the film’s crystal structural character has great impact on its RRR/Tc value.

THPO064	Structural Properties of Niobium Thin Films Deposited on Metallic Substrates by ECR Plasma Energetic Condensation	877
	J.K. Spradlin, H.L. Phillips, C.E. Reece, A-M. Valente-Feliciano, X. Zhao JLAB, Newport News, Virginia, USA D. Gu ODU, Norfolk, Virginia, USA K.I. Seo NSU, Newport News, Virginia, USA
	Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. Particle accelerator technologies rely on SRF cavities to create the accelerating gradient for beam lines. Solid niobium cavities are widely employed throughout the community despite high material, fabrication, and operation cost. New thin film technologies are being explored for the suitability of niobium coatings for accelerating cavities. Thin layers of high-quality niobium would be deposited on a base material that has lower material and fabrication cost. Copper is a strong candidate for the cavity base due to availability, cost, machinability, and potentially improved performance characteristics of the niobium SRF surface. Initial results of TEM, EBSD and XRD analyses of niobium thin films grown on copper substrates under controlled conditions are presented to demonstrate the feasibility of the technology and establish lower limits of performance characteristics. Correlation of RRR data with the structure of niobium thin films will demonstrate the importance of thin film structural quality.

Paper

Title

Page

Structural Characterization of Nb Films Deposited by ECR Plasma Energetic Condensation on Crystalline Insulators

819

X. Zhao, H.L. Phillips, C.E. Reece, J.K. Spradlin, A-M. Valente-Feliciano
JLAB, Newport News, Virginia, USA
H. Baumgart, D. Gu
ODU, Norfolk, Virginia, USA
K.I. Seo
NSU, Newport News, Virginia, USA

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
An energetic condensation thin film coating technique with an electron cyclotron resonance (ECR) induced plasma ion source is used to deposit Nb thin films on crystalline insulating substrates, such as a-plane and c-plane sapphire (Al2O3) and on magnesium oxide, MgO (100), (110), and (111). Heteroepitaxial Nb films were produced by ECR deposition with regulated substrate temperature. The residual resistance ratio (RRR) of about 1 micron thick films reach unprecedented values (350 - 450) on a-plane (11-20) sapphire substrates. The epitaxial relationship of Nb/crystalline substrate is found to be strongly influenced by the substrate bias voltage (adding to the initial Nb+ kinetic energy), the substrate crystalline orientation, and heating conditions. At low substrate temperature, the Nb films demonstrated non-epitaxial crystalline textures, revealed by XRD Pole Figure technique and Electron Backscattering Diffraction (EBSD). The texture might be caused by “Volmer-Weber” growth mode, i.e. island growth, at low surface adatom mobility. This study shows that the film’s crystal structural character has great impact on its RRR/Tc value.

THPO064

Structural Properties of Niobium Thin Films Deposited on Metallic Substrates by ECR Plasma Energetic Condensation

877

J.K. Spradlin, H.L. Phillips, C.E. Reece, A-M. Valente-Feliciano, X. Zhao
JLAB, Newport News, Virginia, USA
D. Gu
ODU, Norfolk, Virginia, USA
K.I. Seo
NSU, Newport News, Virginia, USA

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
Particle accelerator technologies rely on SRF cavities to create the accelerating gradient for beam lines. Solid niobium cavities are widely employed throughout the community despite high material, fabrication, and operation cost. New thin film technologies are being explored for the suitability of niobium coatings for accelerating cavities. Thin layers of high-quality niobium would be deposited on a base material that has lower material and fabrication cost. Copper is a strong candidate for the cavity base due to availability, cost, machinability, and potentially improved performance characteristics of the niobium SRF surface. Initial results of TEM, EBSD and XRD analyses of niobium thin films grown on copper substrates under controlled conditions are presented to demonstrate the feasibility of the technology and establish lower limits of performance characteristics. Correlation of RRR data with the structure of niobium thin films will demonstrate the importance of thin film structural quality.