Física

The ability to construct 2D systems, beyond materials’ natural formation, enriches the search and control capability of new phenomena, for instance, the synthesis of topological lattices of vacancies on metal surfaces through scanning tunneling microscopy. In the present study, we demonstrate that metal atoms encaged in a silicate adlayer on silicon carbide is an interesting platform for lattice design, providing a ground to experimentally construct tight-binding models on an insulating substrate. Based on the density functional theory, we have characterized the energetic and electronic properties of 2D metal
lattices embedded in the silica adlayer. We show that the characteristic band structures of those lattices are ruled by surface states induced by the metal-s orbitals coupled by the host-pxy states, giving rise to spxy Dirac bands neatly lying within the energy gap of the semiconductor substrate.

In this work, a study of the optical and structural properties of a phosphate glass (P2O5-Al2O3-Na2O-K2O) doped with cadmium sulfide (CdS) nanocrystals and co-doped with Nd3+ ions produced by the fusion method was carried out. This study was conducted by analyzing the Optical absorption, Photoluminescence (PL) spectra, Time-resolved PL decay curves, and Raman spectroscopy measurements. The growth of the CdS nanocrystal was confirmed by the optical absorption spectra, Transmission Electron Microscopy, and Raman spectroscopy, which also indicates the presence of surface defect states. After Nd doping, PL spectra show an energy transfer process between the CdS nanocrystal and the Nd3+ ions. This process decreases with the nanocrystal size and can be eliminated by tuning the excitation wavelength. In addition, the influence of the CdS nanocrystal size on the Nd emission lifetime and luminescence quantum efficiency was studied in two different excitations (405 and 532 nm). This kind of system has the potential to work as optoelectronic devices, such as laser active media, optical amplifiers, and planar waveguides due to near-infrared emission of the Nd3+ ions.