[1] Department of Physics, Pennsylvania State University, University Park, PA 16802, United States
[2] Materials Research Institute, Pennsylvania State University, University Park, PA 16802, United States
[3] Dept. of Mat. Sci. and Engineering, Pennsylvania State University, University Park, PA 16802, United States
[4] Ctro. Desenvolvimento da Tecn. Nucl., CDTN/CNEN, Belo Horizonte, MG, Brazil