title: Silicon growth at the two-dimensional limit on Ag(111).
abstract: Having fueled the microelectronics industry for over 50 years, silicon is arguably the most studied and influential semiconductor. With the recent emergence of two-dimensional (2D) materials (e.g., graphene, MoS2, phosphorene, etc.), it is natural to contemplate the behavior of Si in the 2D limit. Guided by atomic-scale studies utilizing ultrahigh vacuum (UHV), scanning tunneling microscopy (STM), and spectroscopy (STS), we have investigated the 2D limits of Si growth on Ag(111). In contrast to previous reports of a distinct sp(2)-bonded silicene allotrope, we observe the evolution of apparent surface alloys (ordered 2D silicon-Ag surface phases), which culminate in the precipitation of crystalline, sp(3)-bonded Si(111) nanosheets. These nanosheets are capped with a √3 honeycomb phase that is isostructural to a √3 honeycomb-chained-trimer (HCT) reconstruction of Ag on Si(111). Further investigations reveal evidence for silicon intermixing with the Ag(111) substrate followed by surface precipitation of crystalline, sp(3)-bonded silicon nanosheets. These conclusions are corroborated by ex situ atomic force microscopy (AFM), transmission electron microscopy (TEM), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). Even at the 2D limit, scanning tunneling spectroscopy shows that the sp(3)-bonded silicon nanosheets exhibit semiconducting electronic properties.
authors.affiliation: Center for Nanoscale Materials, Argonne National Laboratory , 9700 South Cass Avenue, Building 440, Argonne, Illinois 60439, United States .
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Mannix
authors.forename: Brian
authors.initials: B
authors.lastname: Kiraly
authors.forename: Brandon L
authors.initials: BL
authors.lastname: Fisher
authors.forename: Mark C
authors.initials: MC
authors.lastname: Hersam
authors.forename: Nathan P
authors.initials: NP
authors.lastname: Guisinger