[1] Univ Arkansas, Nanotechnol Ctr, Grad Inst Technol, Little Rock, AR 72204 USA
[2] Natl Inst Res & Dev Isotop & Mol Technol, R-400293 Cluj Napoca, Romania
[3] NASA, Electrostat & Surface Phys Lab, Kennedy Space Ctr, Kennedy Space Ctr, FL 32899 USA
[4] Univ Arkansas, Dept Appl Sci, Little Rock, AR 72204 USA
[5] Univ Cent Florida, Adv Mat Proc & Anal Ctr, Orlando, FL 32826 USA