[1] Chiang Mai Univ, Fac Sci, Dept Phys & Mat Sci, Chiang Mai 50200, Thailand
[2] Ubon Ratchathani Rajabhat Univ, Fac Sci, Program Phys, Ubon Ratchathani 34000, Thailand
[3] Chiang Mai Univ, Fac Sci, Mat Sci Res Ctr, Chiang Mai 50200, Thailand
[4] Natl Nanotechnol Ctr, Thailand Sci Pk,Phahonyothin Rd,Klong 1, Klongluang 12120, Phathumthani, Thailand