Direct preparation of standard functional interfaces in oxide heterostructures for 2DEG analysis through beam-induced platinum contacts

Two-dimensional electron gas (2DEG) in SrTiO3/LaAlO3 heterostructures has been extensively studied in the last few years; however, little attention has been given to a practical way to contact electrically the low dimensional gas at the interface. This work demonstrates a method to contact the 2DEG formed at the oxide interfaces connected by platinum electrodes which were made by the decomposition of organometallic gas using focused ion beams. On the surface, the electrodes were defined through photolithography, and at the interface, the electrodes were deposited through the focused ion beams and electrons, which were then evaluated. The quality of the interface electrodes was evaluated at two different partial oxygen pressures (pO2) used for the film deposition: low (10−4 mbar) and high (10−1 mbar). The electrode deposition conditions using electrons or ions have resulted in different rates of metal deposition and interaction with the interface leading to either metallic (2DEG) or insulating behavior

Computational Chemistry Meets Experiments for Explaining the Geometry, Electronic Structure, and Optical Properties of Ca10V6O25

In this paper, we present a combined experimental and theoretical study to disclose, for the first time, the structural, electronic, and optical properties of Ca10V6O25 crystals. The microwave-assisted hydrothermal (MAH) method has been employed to synthesize these crystals with different morphologies, within a short reaction time at 120 °C. First-principle quantum mechanical calculations have been performed at the density functional theory level to obtain the geometry and electronic properties of Ca10V6O25 crystal in the fundamental and excited electronic states (singlet and triplet). These results, combined with the measurements of X-ray diffraction (XRD) and Rietveld refinements, confirm that the building blocks lattice of the Ca10V6O25 crystals consist of three types of distorted 6-fold coordination [CaO6] clusters: octahedral, prism and pentagonal pyramidal, and distorted tetrahedral [VO4] clusters. Theoretical and experimental results on the structure and vibrational frequencies are in agreement. Thus, it was possible to assign the Raman modes for the Ca10V6O25 superstructure, which will allow us to show the structure of the unit cell of the material, as well as the coordination of the Ca and V atoms. This also allowed us to understand the charge transfer process that happens in the singlet state (s) and the excited states, singlet (s*) and triplet (t*), generating the photoluminescence emissions of the Ca10V6O25 crystals

Magnetoresistance in Sn-Doped In2O3Nanowires

In this work, we present transport measurements of individual Sn-doped In2O3nanowires as a function of temperature and magnetic field. The results showed a localized character of the resistivity at low temperatures as evidenced by the presence of a negative temperature coefficient resistance in temperatures lower than 77 K. The weak localization was pointed as the mechanism responsible by the negative temperature coefficient of the resistance at low temperatures