[1] Univ Michigan, Appl Phys Program, Ann Arbor, MI 48109 USA
[2] Univ Michigan, Dept Chem, Ann Arbor, MI 48109 USA
[3] Boston Univ, Dept Phys, Dept Mech Engn, 590 Commonwealth Ave, Boston, MA 02215 USA
[4] Boston Univ, Div Mat Sci & Engn, Boston, MA 02215 USA