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10 pags., 5 figs. -- This article belongs to the Special Issue 2D Materials and Heterostructures with Application in Optoelectronics ; 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 project has received funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme (grant agreement n◦ 755655, ERC-StG 2017 project 2D-TOPSENSE), the European Commission, under the Graphene Flagship (Core 3, grant number 881603), the Spanish Ministry of Economy, Industry and Competitiveness through the grant MAT2017-87134-C2-2-R and partially funded by the Spanish Ministerio de Ciencia e Innovación through grant RTI2018-096498-B-I00 (MCIU/AEI/FEDER, UE). SP acknowledges the fellowship PRE2018-084818.

Direct growth of graphene films on dielectric substrates (quartz and silica) is reported, by means of remote electron cyclotron resonance plasma assisted chemical vapor deposition r-(ECR-CVD) at low temperature (650 °C). Using a two step deposition process– nucleation and growth– by changing the partial pressure of the gas precursors at constant temperature, mostly monolayer continuous films, with grain sizes up to 500 nm are grown, exhibiting transmittance larger than 92% and sheet resistance as low as 900 Ω sq−1. The grain size and nucleation density of the resulting graphene sheets can be controlled varying the deposition time and pressure. In additon, first-principles DFT-based calculations have been carried out in order to rationalize the oxygen reduction in the quartz surface experimentally observed. This method is easily scalable and avoids damaging and expensive transfer steps of graphene films, improving compatibility with current fabrication technologies. ; This work has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 696656. JA acknowledges funding from FPI Program of MINECO (BES-2012-058600). JIM acknowledges funding from the ERC-Synergy Program (Grant ERC-2013-SYG-610256 NANOCOSMOS) and computing resources from CTI-CSIC. CM acknowledges the financial support by the 'Ramón y Cajal' Program of MINECO (RYC-2014-16626). ; Peer reviewed

In this study we report on the effective p-doping of chemical vapor deposition (CVD) graphene transferred from copper foil onto SiO2/Si and PET substrates. Tetrachloroauric acid (HAuCl4) is used to promote graphene doping with a direct correlation between its concentration and modification of graphene's electrical properties. The doping mechanism entails the charge transfer (CT) between AuIII ions and graphene, and the formation of Au nanoparticles (AuNPs) on the surface. X-ray photoelectron spectroscopy (XPS) was employed to confirm this charge transfer, whereas the presence of the AuNPs was verified based on Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM) images. The influence of doping on the electrical properties of graphene was assessed by Kelvin Probe Microscopy (KPM) and standard Hall Effect measurements, proving the ability of the method to effectively tune the carrier concentration, achieving sheet resistances as low as 79 Ω/sq. The controlled tuning of the electrical properties together with the use of flexible substrates makes the presented results a very interesting approach enabling the development of a variety of industrial applications, including flexible electronics. ; The research leading to these results has received funding from the European Union Seventh Framework Programme under grant agreement n°604391 Graphene Flagship. This work was also supported by the EU-FET grant GRAPHENICS618086 and the Polish National Science CentreUMO-2013/09/N/ST5/02481. ; Peer reviewed

We describe a three axis vector magnet system for cryogenic scanning probe microscopy measurements. We discuss the magnet support system and the power supply, consisting of a compact three way 100 A current source. We obtain tilted magnetic fields in all directions with maximum value of 5T along z-axis and of 1.2T for XY-plane magnetic fields. We describe a scanning tunneling microscopy-spectroscopy (STM-STS) set-up, operating in a dilution refrigerator, which includes a new high voltage ultralow noise piezodrive electronics and discuss the noise level due to vibrations. STM images and STS maps show atomic resolution and the tilted vortex lattice at 150 mK in the superconductor β-Bi2Pd. We observe a strongly elongated hexagonal lattice, which corresponds to the projection of the tilted hexagonal vortex lattice on the surface. We also discuss Magnetic Force Microscopy images in a variable temperature insert ; This work was supported by Convocatoria Doctorados en el Exterior 568-2012 COLCIENCIAS, the Spanish MINECO (FIS2011-23488, MAT2011-27470-C02-02, CSD2009-00013), by the Comunidad de Madrid through program Nanofrontmag-CM (S2013/MIT-2850) and by Marie-Curie actions under the project FP7-PEOPLE-2013- CIG-618321. The research leading to these results has received funding from the European Union Seventh Framework Programme under Grant Agreement No. 604391 Graphene Flagship. We also acknowledge Banco Santander, COST MP1201. J.A. and C.M. acknowledge the FPI (BES- 2012-058600) and Juan de la Cierva (JCI-2011-08815) programs, respectively

Graphene functionalization with organics is expected to be an important step for the development of graphene-based materials with tailored electronic properties. However, its high chemical inertness makes difficult a controlled and selective covalent functionalization, and most of the works performed up to the date report electrostatic molecular adsorption or unruly functionalization. We show hereafter a mechanism for promoting highly specific covalent bonding of any amino-terminated molecule and a description of the operating processes. We show, by different experimental techniques and theoretical methods, that the excess of charge at carbon dangling-bonds formed on single-atomic vacancies at the graphene surface induces enhanced reactivity towards a selective oxidation of the amino group and subsequent integration of the nitrogen within the graphene network. Remarkably, functionalized surfaces retain the electronic properties of pristine graphene. This study opens the door for development of graphene-based interfaces, as nano-bio-hybrid composites, fabrication of dielectrics, plasmonics or spintronics. ; The research leading to these results has received funding from the Spanish MINECO (through Grants No. MAT2014-54231-C4-1-P, MAT2016-80394-R, RYC-2014-16626 and RYC-2015-17730), from the EU via the ERC-Synergy Program (Grant No. ERC-2013-SYG-610256 Nanocosmos) and the European Union Seventh Framework Program (Grant No. 604391 Graphene Flagship), and from the Comunidad Autónoma de Madrid (CAM) via the MAD2D-CM Program (Grant No. S2013/MIT-3007). We also thank the computing resources from CTI-CSIC. R.L. acknowledges financial support from Spanish MINECO under Grant agreement No. CONSOLIDER INGENIO CSD2009-00013. ; Peer reviewed