Molybdenum trioxide (MoO₃) in-plane anisotropy has increasingly attracted the attention of the scientific community in the last few years. Many of the observed in-plane anisotropic properties stem from the anisotropic refractive index and elastic constants of the material but a comprehensive analysis of these fundamental properties is still lacking. Here we employ Raman and micro-reflectance measurements, using polarized light, to determine the angular dependence of the refractive index of thin MoO₃ flakes and we study the directional dependence of the MoO₃ Young’s modulus using the buckling metrology method. We found that MoO₃ displays one of the largest in-plane anisotropic mechanical properties reported for 2D materials so far.

Finding 2D and thin‐film layered materials have become essential to develop not only in scientific‐related fields, but also in a wide industry, which is constantly feeding from this progress. For electronic devices, thin‐film materials are supposed to be a step forward to overcome Moore's law. In many other technologic areas, the development of tools based on flakes of materials has found new physics, becoming a rising field. Although, destructive techniques are commonly used to characterize the thickness of these materials. Herein, a list of materials is presented, whose thicknesses are characterized by their apparent colors in several substrates, a harmless, fast, and reliable technique that has been already used to determine the number of layers in several works. This list is also enlarged with other materials and substrates.

Considering that two-dimensional (2D) molybdenum trioxide has acquired more attention in the last few years, it is relevant to speed up thickness identification of this material. We provide two fast and non-destructive methods to evaluate the thickness of MoO₃ flakes on SiO₂/Si substrates. First, by means of quantitative analysis of the apparent color of the flakes in optical microscopy images, one can make a first approximation of the thickness with an uncertainty of ±3 nm. The second method is based on the fit of optical contrast spectra, acquired with micro-reflectance measurements, to a Fresnel law-based model that provides an accurate measurement of the flake thickness with ±2 nm of uncertainty.

This work investigates the vibrational and electrical properties of molybdenum trioxide (α-MoO₃) upon tensile strain applied along different crystal directions. Using a three-point bending setup in combination with Raman spectroscopy, we report measurements of a blueshift of the Raman modes when uniaxial tensile strain is applied along the a- and c-axis to this material. Furthermore, the electrical measurements reveal an increase in resistance with strain applied along both in-plane directions. The findings from the uniaxial strain and Raman spectroscopy measurements are further confirmed by ab-initio calculations. This study provides valuable insights into the mechanical and vibrational properties of α-MoO₃ and its potential use in several applications. This study contributes to the growing body of knowledge on the properties of α-MoO₃ and lays the foundation for further exploration of its potential applications. Given MoO₃ holding the natural hyperbolic phonon polaritons, attracting significant research interest, this study has the potential to arouse the curiosity of the scientific community.

We report on outstanding photo-responsivity, R > 10³ A/W, fast response (~0.1 s), and broadband sensitivity ranging from the UV to the NIR in two terminal graphene/MoS₂ photodetectors. Our devices are based on the deterministic transfer of MoS₂ on top of directly grown graphene on sapphire, and their performance outperforms previous similar photodetectors using large-scale grown graphene. Here we devise a protocol for the direct growth of transparent (transmittance, Tr > 90%), highly conductive (sheet resistance, R_□ < 1 kΩ) uniform and continuous graphene films on sapphire at 700 °C by using plasma-assisted chemical vapor deposition (CVD) with C₂H₂/H₂ gas mixtures. Our study demonstrates the successful use of plasma-assisted low-temperature CVD techniques to directly grow graphene on insulators for optoelectronic applications.

We perform X-ray diffraction and AFM characterization of CdSe-nano-pyramids layers up to monolayer covering. The CdSe-particles are perfectly ordered growing with an axial and lateral matching with the HOPG substrate lattice in a hexagonal arrange.