Affiliation: | aDept. of Physics and Astronomy and The Nebraska Center for Material and Nanoscience, Univ. of Nebraska, Lincoln, NE 68588-0111, USA;bDept. of Physics and Electronics, Univ. of Puerto Rico-Humacao, 100 Road #908, CUH Station, Humacao, PR 00791, USA;cDept. of Physics, State University of New York at Oswego, Oswego, NY 13126, USA |