Investigation of Chemical/Mechanical Polishing of Niobium

CALOTA, GEORGE and Maximova, N and Ziemer, KS and Muftu, S. (2009) Investigation of Chemical/Mechanical Polishing of Niobium. Tribology Transactions, 52 (4). p. 447. ISSN 05698197

Full text not available from this repository.


A chemical/mechanical method for polishing flat niobium sheets to a mirror finish was developed. Various polishing slurries with different open circuit potentials and pH values were considered. All slurries fell within the niobate region of the Pourbaix diagrams, indicating that slurries are in a thermodynamically stable region. Oxidation characteristics of the niobium in the various slurries were determined by XPS and confirmed previously published work that niobium forms various layers of stable niobium oxides roughly 4.5-4.7 nm in thickness on the surface. A multi-step polishing method that relies on mechanical abrasion of the surface proved to be effective, and particles of different hardness and size were explored. Niobium wafers with initial peak-to-valley (PV) surface roughness of 3 to 7 m were polished. The multi-step process utilized a slurry containing 1 m diameter alumina particles to polish this initial roughness down to a submicrometer level. The final polish was provided by a slurry containing smaller particles. The oxide slurry with 70 to 100 nm silica particles gave the best mirror finished surface, with PV = 235 nm, Ra = 32 nm, and RMS = 39 nm. While polishing caused some disorder in the niobium metal, using the oxide slurry gave results closer to those obtained by buffered chemical polish (BCP), which exhibits the highest degree of atomic order based on XPS studies. A polishing process starting with mechanical abrasion, followed by a two-step mechanical polish, is successful for obtaining smooth niobium surfaces on flat wafers.

Item Type: Article
Additional Information: Calota, G (reprint author), Northeastern Univ, Dept Mech Engn, Boston, MA 02115 USA
Uncontrolled Keywords: Polishing; Surface Roughness; XPS; Niobium; Chemical Mechanical Polishing; Buffered Chemical Polishing; Superconducting Radio Frequency Cavities
InterNano Taxonomy: Nanomanufacturing Processes > Miscellaneous Technologies
Nanomanufacturing Processes
Collections: Nanomanufacturing Research Collection
Depositing User: Danielle Federa
Date Deposited: 16 Jun 2009 18:19
Last Modified: 16 Jun 2009 18:19

Actions (login required)

View Item View Item