Silicon nanoribbons on Ag(110): silicene or Si chain reconstruction?

Since the first reported synthesis, in 2005, of one-dimensional nanoribbon structures following the evaporation of silicon on Ag(110), a number of studies have proposed that they are composed of silicene--a single layer of a buckled honeycomb structure of Si atoms [1]. This interpretation was subsequently questioned in experimental studies using Raman and surface differential reflectance spectrsocopy [2]. Recently a number of new structural models have been proposed that suggest a Si-stabilized missing row reconstruction based on zigzag [3] or pentamer [4] chains. Here I present refined experimental and theoretical studies using grazing incidence x-ray diffraction (GIXD), scanning tunneling microscopy (STM), surface optical spectra (RAS and SDRS), and density-functional theory (DFT) which confirms the correct structure as being a pentamer chain reconstruction and definitively ruling out a honeycomb structure like that of freestanding silicene [5]. References: [1] A. Kara et al, Journal of Superconductivity and Novel Magnetism 22, 259 (2009); P. De Padova, et al, Applied Physics Letters 96, 261905 (2010); B. Aufray et al, Applied Physics Letters 96, 183102 (2010); C. Lian and J. Ni, Physica B: Condensed Matter 407, 4695 (2012). [2] E. Speiser et al, Applied Physics Letters 104, 161612 (2014); Y. Borensztein, et al, Physical Review B 89, 245410 (2014). [3] C. Hogan, S. Colonna, R. Flammini, A. Cricenti, and F. Ronci, Phys. Rev. B 92, 115439 (2015). [4] J. I. Cerdá, J. S?awi?ska, G. Le Lay, A. C. Marele, J. M. Gómez-Rodríguez, and M. E. Dávila, Nat. Commun. 7, 13076 (2016). [5] Geoffroy Prévot, Conor Hogan, Thomas Leoni, Romain Bernard, Eric Moyen, and Laurence Masson, Phys. Rev. Lett. 117, 276102 (2016); Conor Hogan, D. Martin, Y. Borensztein, in preparation.