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Germanium arsenide (GeAs) is a layered semiconductor with remarkably anisotropic thermoelectric and optical properties and a promising candidate for multifunctional devices based on in-plane polarization dependent response. Understanding the underlying mechanism of such devices requires knowledge of GeAs electronic band structure and of the hot carrier dynamics in its conduction band, whose details are still unclear. In this work, we investigate the properties of occupied and photoexcited states of GeAs, by combining scanning tunneling spectroscopy, angle-resolved photoemission spectroscopy (ARPES), and time-resolved ARPES. We find that GeAs is an ∼0.8 eV indirect gap semiconductor, for which the conduction band minimum (CBM) is located at the Γ ¯ point while the valence band maximum is out of Γ ¯ . A Stark broadening of the valence band is observed immediately after photoexcitation, which can be attributed to the effects of the electrical field at the surface induced by inhomogeneous screening. Moreover, the hot electron relaxation time of 1.56 ps is down to the CBM, which is dominated by electron–phonon coupling. Besides their relevance for our understanding of GeAs, these findings present general interest for the design of high performance thermoelectric and optoelectronic devices based on 2D semiconductors. [ABSTRACT FROM AUTHOR]

Using scanning tunneling microscopy (STM), Auger electron spectroscopy, and low energy electron diffraction, we have observed a surprising complete dissolution at room temperature of one lead monolayer deposited by evaporation on an aluminum oxide thin film (∼0.8 nm thick) previously grown on Ag (111). We have observed the quasi-instantaneous diffusion of the lead deposit through the oxide layer to the silver/oxide interface. After the diffusion process, lead atoms form a Moiré superstructure, which is characterized by STM through the oxide layer. This unexpected behavior puts in light the very weak interaction between the aluminum oxide and the silver substrate. [ABSTRACT FROM AUTHOR]

We report results on the self-assembly of silicon nanoribbons (NRs) on the (2 × 1) reconstructed Au(110) surface under ultra-high vacuum conditions. Upon adsorption of 0.2 monolayer (ML) of silicon, the (2 × 1) reconstruction of Au(110) is replaced by an ordered surface alloy. Above this coverage, a new superstructure is revealed by low energy electron diffraction (LEED), which becomes sharper at 0.3 Si ML. This superstructure corresponds to Si nanoribbons all oriented along the [formula] direction as revealed by LEED and scanning tunneling microscopy (STM). STM and high-resolution photoemission spectroscopy indicate that the nanoribbons are flat and predominantly 1.6 nm wide. In addition, the silicon atoms show signatures of two chemical environments corresponding to the edge and center of the ribbons. [ABSTRACT FROM AUTHOR]

We report on the electronic properties of straight, 1.6 nm wide, silicene nanoribbons on Ag(110), arranged in a one-dimensional grating with a pitch of 2 nm, whose high-resolution scanning tunneling microscopy images reveal a honeycomb geometry. Angle-resolved photoemission shows quantum confined electronic states of one-dimensional character. The silicon band dispersion along the direction of the nanoribbons suggests a behavior analogous to the Dirac cones of graphene on different substrates. [ABSTRACT FROM AUTHOR]

Scanning tunneling microscopy (STM) and ab initio calculations based on density functional theory (DFT) were used to study the self-aligned silicon nanoribbons on Ag(110) with honeycomb, graphene-like structure. The silicon honeycombs structure on top of the silver substrate is clearly observed by STM, while the DFT calculations confirm that the Si atoms adopt spontaneously this new silicon structure. [ABSTRACT FROM AUTHOR]

Using atomic resolved scanning tunneling microscopy, we present here the experimental evidence of a silicene sheet (graphenelike structure) epitaxially grown on a close-packed silver surface [Ag(111)]. This has been achieved via direct condensation of a silicon atomic flux onto the single-crystal substrate in ultrahigh vacuum conditions. A highly ordered silicon structure, arranged within a honeycomb lattice, is synthesized and present two silicon sublattices occupying positions at different heights (0.02 nm) indicating possible sp2-sp3 hybridizations. [ABSTRACT FROM AUTHOR]