We show that the (3 × 1) stripe structure observed in TaTe2 at room temperature arises from the formation of Ta4+–Ta4+ dimer chains along with a separate chain of Ta3+. More importantly, we reveal an intriguing lattice distortion and charge modulation at low temperature, which suggests an interplay and competition between the triple-axis (3 × 3) charge density wave-like modulation and the single-axis (3 × 1) stripe configuration. This work highlights the importance of TaTe2 as an alternative platform with rich structural and electrical phases to explore charge-lattice coupling.

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Surfaces and interfaces play a critical role in determining properties and functions of nanomaterials, in many cases dominating bulk properties, owing to the large surface-and interface-area-to-volume ratio. Using Si nanomembranes, a well-controlled two-dimensional single-crystalline semiconductor, as a prototype system, we discuss how surfaces and interfaces influence electrical transport properties at the nanoscale. We show that electronic conduction in Si nanomembranes is not determined by bulk dopants but by the interplay of surface and interface electronic structures with the "bulk" band structure of the thin Si membrane. Additionally, we describe our recent experimental results on the control of highly ordered molecular structures on Si surfaces, which is of intense interest for the integration of ordered organic thin films in silicon-based electronics. This could also potentially lead to the rational design of Si nanostructures with controlled properties through regulation of the surface chemistry.

Growing organic molecular films on inorganic substrates is crucial for organic electronics applications; however, it still remains a significant challenge to achieve long-range molecular ordering. Here we report the formation of highly ordered zinc phthalocyanine (ZnPc) thin films on the deactivated Si(111)-B √3 × √3 R30°surface characterized by scanning tunneling microscopy (STM) and low energy electron diffraction (LEED). We find that for the initial submonolayer growth, access to the anisotropic step-flow growth mode yields a reduction in the substrate symmetry resulting in two dominant mirror-reflected domains. Upon further deposition, the ZnPc molecules are able to maintain a highly ordered configuration both laterally and vertically up to 40 monolayers even though the molecule− substrate interaction decreases as evidenced by the diminished moirépattern and a mild relaxation in the molecular packing. We attribute the formation of highly ordered organic molecular thin films to the delicate balance between the molecule−molecule and molecule− substrate interactions. These findings pave the way for the integration of functional organic materials into silicon-based electronics.

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We report the growth evolution of thermally evaporated zinc phthalocyanine (ZnPc) on the deactivated Si(111) surface using scanning tunneling microscopy (STM). We find that the Ehrlich-Schwöebel barrier (ESB) associated with the ZnPc step edges is negligible, while the formation of molecular domain boundaries provides an activation barrier and additional nucleation sites which increases the film roughness and interrupts the anisotropic step-flow growth. By increasing the substrate temperature, the grain boundary density is significantly reduced, resulting in a well-controlled surface morphology. This study provides insight into the influence of the ESB and the grain boundary crossing barrier on the growth dynamics of organic thin films.

Freestanding silicene, a monolayer of Si arranged in a honeycomb structure, has been predicted to give rise to massless Dirac fermions, akin to graphene. However, Si structures grown on a supporting substrate can show properties that strongly deviate from the freestanding case. Here, combining scanning tunneling microscopy/spectroscopy and differential conductance mapping, we show that the electrical properties of the phase of few-layer Si grown on Ag(111) strongly depend on film thickness, where the electron phase coherence length decreases and the free-electron-like surface state gradually diminishes when approaching the interface. These features are presumably attributable to the inelastic inter-band electron-electron scattering originating from the overlap between the surface state, interface state and the bulk state of the substrate. We further demonstrate that the intrinsic electronic structure of the as grown phase is identical to that of the R30° reconstructed Ag on Si(111), both of which exhibit the parabolic energy-momentum dispersion relation with comparable electron effective masses. These findings highlight the essential role of interfacial coupling on the properties of two-dimensional Si structures grown on supporting substrates, which should be thoroughly scrutinized in pursuit of silicene.