[en] In this study we present results on the AC admittance response of bilayer MoS₂ films grown using chemical vapor deposition. A new MOS capacitor design for ultra-thin body 2D materials is proposed. We show that along with the density of interface traps (D _it), a transverse electric field distribution in the semiconductor and parasitic capacitance also cause frequency dispersion in measured capacitance. D _it extracted using the conductance method in 40 devices indicates reliable measurements for channel length, L  <  10 m. For devices with L  >  10 m, an increase in D _it is an artifact of access resistance in the semiconductor. Temperature measurements show an increasing defect distribution from cm⁻² eV⁻¹ around mid-gap to cm⁻² eV⁻¹ close to the conduction band minimum. (paper)

[en] Two-dimensional transition metal dichalcogenides have been the focus of intense research for their potential application in novel electronic and optoelectronic devices. However, growth of large area two-dimensional transition metal dichalcogenides invariably leads to the formation of grain boundaries that can significantly degrade electrical transport by forming large electrostatic barriers. It is therefore critical to understand their effect on the electronic properties of two-dimensional semiconductors. Using MoS₂ as an example material, we are able to probe grain boundaries in top and buried layers using conductive atomic force microscopy. We find that the electrical radius of the grain boundary extends approximately 2 nm from the core into the pristine material. The presence of grain boundaries affects electrical conductivity not just within its own layer, but also in the surrounding layers. Therefore, electrical grain size is always smaller than the physical size, and decreases with increasing thickness of the MoS₂. These results signify that the number of layers in synthetically grown 2D materials must ideally be limited for device applications. (paper)

[en] The rapid cadence of MOSFET scaling is stimulating the development of new technologies and accelerating the introduction of new semiconducting materials as silicon alternative. In this context, 2D materials with a unique layered structure have attracted tremendous interest in recent years, mainly motivated by their ultra-thin body nature and unique optoelectronic and mechanical properties. The development of scalable synthesis techniques is obviously a fundamental step towards the development of a manufacturable technology. Metal-organic chemical vapor deposition has recently been used for the synthesis of large area TMDs, however, an important milestone still needs to be achieved: the ability to precisely control the number of layers and surface uniformity at the nano-to micro-length scale to obtain an atomically flat, self-passivated surface. In this work, we explore various fundamental aspects involved in the chemical vapor deposition process and we provide important insights on the layer-dependence of epitaxial MoS₂ film’s structural properties. Based on these observations, we propose an original method to achieve a layer-controlled epitaxy of wafer-scale TMDs. (paper)

[en] Silicene, the Si counterpart of graphene, grows on Ag(111) forming domains. Investigation, by means of scanning tunneling microscopy, of morphological properties is carried out by considering post-deposition process. Particular attention is here addressed to the post-deposition annealing temperature, which plays an important role in determining the resulting morphology. On the other hand, electronic properties are probed by scanning tunneling spectroscopy and a position-dependent local density of states results, which can be understood in terms of symmetry breaking in the honeycomb lattice.