[1] SMC Corp, College Stn, TX 77845 USA
[2] Southern Univ, Solid State Ion & Surface Sci Lab, Dept Phys, Baton Rouge, LA 70813 USA
[3] A&M Coll, Baton Rouge, LA 70813 USA
[4] Natl Inst Technol, Dept Phys, Warangal, Andhra Pradesh, India
[5] Tech Univ Chemnitz, Inst Chem, AG Elektrochem, D-09107 Chemnitz, Germany