Vacancy-induced nanoscale phase separation in KxFe2− ySe2 single crystals evidenced by Raman scattering and powder x-ray diffraction

N. Lazarević,1 M. Abeykoon,2 P. W. Stephens,3,4 Hechang Lei ( ),2 E. S. Bozin,2 C. Petrovic,2 and Z. V. Popović1 1Center for Solid State Physics and New Materials, Institute of Physics Belgrade, University of Belgrade, Pregrevica 118, 11080 Belgrade, Serbia 2Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, New York 11973-5000, USA 3Department of Physics and Astronomy, State University of New York, Stony Brook, NY 11794-3800, USA 4Photon Sciences Directorate, Brookhaven National Laboratory, Upton, New York 11973-5000, USA (Received 7 May 2012; revised manuscript received 10 July 2012; published 6 August 2012)