J. Laverock,1 J. Kuyyalil,1 B. Chen,1 R. P. Singh,2,* B. Karlin,3 J. C. Woicik,3 G. Balakrishnan,2 and K. E. Smith1,4 1Department of Physics, Boston University, 590 Commonwealth Avenue, Boston, Massachusetts 02215, USA 2Department of Physics, University of Warwick, Coventry CV4 7AL, United Kingdom 3Materials Science and Engineering Laboratory, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA 4School of Chemical Sciences and MacDiarmid Institute for Advanced Materials and Nanotechnology, University of Auckland, Auckland 1142, New Zealand (Received 24 October 2014; revised manuscript received 8 April 2015; published 20 April 2015)