The fascinating properties of two-dimensional （2D） crystals have gainedincreasing interest for many applications. The synthesis of a 2D silicon structure,namely silicene, is attracting great interest for possible de...The fascinating properties of two-dimensional （2D） crystals have gainedincreasing interest for many applications. The synthesis of a 2D silicon structure,namely silicene, is attracting great interest for possible development of nextgeneration electronic devices. The main difficulty in working with siliceneremains its strong tendency to oxidation when exposed to air as a consequenceof its relatively highly buckled structure. In this work, we univocaUy identifythe Raman mode of air-stable low-buckled silicene nanosheets synthesized onhighly oriented pyrolytic graphite （HOPG） located at 542.5 cm-1. The main focusof this work is Raman spectroscopy and mapping analyses in combination withab initio calculations. Scanning tunneling microscopy images reveal the presenceof a patchwork of Si three-dimensional （3D） clusters and contiguous Si areaspresenting a honeycomb atomic arrangement, rotated by 30° with respect to theHOPG substrate underneath, with a lattice parameter of 0.41±0.02 nm and abuckling of the Si atoms of 0.05 nm. Raman analysis supports the co-existenceof 3D silicon clusters and 2D silicene. The Raman shift of low-buckled siliceneon an inert substrate has not been reported so far and it is completely differentfrom the one calculated for free-standing silicene and the ones measured forsilicene grown on Ag（111） surfaces. Our experimental results are perfectlyreproduced by our ab initio calculations of deposited silicene nanosheets. Thisleads us to conclude that the precise value of the observed Raman shift crucially depends on the strain between the silicene and the HOPG substrate.展开更多
A comprehensive picture of the initial stages of silicene growth on graphite is drawn.Evidence is shown that quasiparticle interferences play a crucial role in the formation of the observed silicene configurations.We ...A comprehensive picture of the initial stages of silicene growth on graphite is drawn.Evidence is shown that quasiparticle interferences play a crucial role in the formation of the observed silicene configurations.We propose,on one hand,that the charge modulations caused by those quantum interferences serve as templates and guide the incoming Si atoms to self-assemble to the unique(√3 x√3)R30°honeycomb atomic arrangement.On the other hand,their limited extension limits the growth to about 150 Si atoms under our present deposition conditions.The here proposed electrostatic interaction finally explains the unexpected stability of the observed silicene islands over time and with temperature.Despite the robust guiding nature of those quantum interferences during the early growth phase,we demonstrate that the window of experimental conditions for silicene growth is quite narrow,making it an extremely challenging experimental task.Finally,it is shown that the experimentally observed threedimensional silicon clusters might very well be the simple result of the end of the silicene growth resulting from the limited extent of the quasi-particle interferences.展开更多
文摘The fascinating properties of two-dimensional （2D） crystals have gainedincreasing interest for many applications. The synthesis of a 2D silicon structure,namely silicene, is attracting great interest for possible development of nextgeneration electronic devices. The main difficulty in working with siliceneremains its strong tendency to oxidation when exposed to air as a consequenceof its relatively highly buckled structure. In this work, we univocaUy identifythe Raman mode of air-stable low-buckled silicene nanosheets synthesized onhighly oriented pyrolytic graphite （HOPG） located at 542.5 cm-1. The main focusof this work is Raman spectroscopy and mapping analyses in combination withab initio calculations. Scanning tunneling microscopy images reveal the presenceof a patchwork of Si three-dimensional （3D） clusters and contiguous Si areaspresenting a honeycomb atomic arrangement, rotated by 30° with respect to theHOPG substrate underneath, with a lattice parameter of 0.41±0.02 nm and abuckling of the Si atoms of 0.05 nm. Raman analysis supports the co-existenceof 3D silicon clusters and 2D silicene. The Raman shift of low-buckled siliceneon an inert substrate has not been reported so far and it is completely differentfrom the one calculated for free-standing silicene and the ones measured forsilicene grown on Ag（111） surfaces. Our experimental results are perfectlyreproduced by our ab initio calculations of deposited silicene nanosheets. Thisleads us to conclude that the precise value of the observed Raman shift crucially depends on the strain between the silicene and the HOPG substrate.
文摘A comprehensive picture of the initial stages of silicene growth on graphite is drawn.Evidence is shown that quasiparticle interferences play a crucial role in the formation of the observed silicene configurations.We propose,on one hand,that the charge modulations caused by those quantum interferences serve as templates and guide the incoming Si atoms to self-assemble to the unique(√3 x√3)R30°honeycomb atomic arrangement.On the other hand,their limited extension limits the growth to about 150 Si atoms under our present deposition conditions.The here proposed electrostatic interaction finally explains the unexpected stability of the observed silicene islands over time and with temperature.Despite the robust guiding nature of those quantum interferences during the early growth phase,we demonstrate that the window of experimental conditions for silicene growth is quite narrow,making it an extremely challenging experimental task.Finally,it is shown that the experimentally observed threedimensional silicon clusters might very well be the simple result of the end of the silicene growth resulting from the limited extent of the quasi-particle interferences.
