Monolithic growth of ultrathin Ge nanowires on Si(001) 
J. Zhang, G. Katsaros, F. Montalenti, D. Scopece, R. Rezaev, C. Mickel, B. Rellinghaus, L. Miglio, S. De Franceschi, A. Rastelli, O. Schmidt, Physical Review Letters 109 (2012).