SEM tomography for the investigation of hybrid structures

The morphological investigation at the micrometric scale of a graphene - ZnO nanorods hybrid structure is performed by scanning electron microscopy. When operated in the scanning-transmission imaging mode, the detection strategy allows implementation of a tomographic approach to recover the three dimensional spatial arrangement of the sample constituents. This tomographic approach complements the serial-sectioning imaging methods and is suitable for thin, self-standing specimens

Reduced Graphene Oxide: fundamentals and applications

In this paper we report our recent studies on the fundamental physical/chemical properties of supported reduced Graphene Oxide (rGO) obtained either via standard thermal annealing or under extreme-UV (EUV) light exposure alongside with investigations on its possible technological applications. rGO has been studied by X-ray Photoelectron Spectroscopy (XPS), micro-Raman Spectroscopy (μRS), and Optical Microscopy. rGO reduction degree has been calibrated on the basis of its color contrast (CC) providing a handy tool to quantitatively determine the fraction of sp The original choice of using EUV instead of UV light to photo-reduce supported GO is not only advantageous in terms of reduction efficiency but it also allows to introduce the concept of EUV photolithography (today limited to the silicon technology only) for the processing of graphene-based materials. Here we demonstrate resistless sub-micrometer GO photo-patterning over large areas ( 10 mm 2 ) This result is a relevant upgrade for the graphene-based technology that can take advantage, in this way, from the entire know-how of the EUV-based technology in view of an eco-sustainable all-carbon technology

Electronic structure of tris(8-hydroxyquinolinato)aluminium(III) revisited using the Heyd-Scuseria-Ernzerhof hybrid functional: Theory and experiments

The electronic properties of tris(8-hydroxyquinolinato)aluminium(III) (AlQ3) have been revisited using the screened hybrid Heyd-Scuseria-Ernzerhof density functional theory. We show that such approach very well accounts for the experimental occupied (valence band spectrum) and unoccupied (inverse photoemission spectrum) states. Furthermore, the density of states projected onto nitrogen, oxygen, and carbon are compared with soft x-ray adsorption and emission spectroscopy, showing a very good agreement between theory and experiments. Finally, a fully theoretical interpretation of the carbon 1s core level is proposed

Infrared photoluminescence of erbium-tris(8-hydroxyquinoline)in a distributed feedback cavity

A distributed feedback (DFB) waveguide cavity with erbium-tris(8-hydroxyquinoline) has been fabricated by X-ray interference lithography in a laboratory-scale apparatus. The DFB cavity consists of a large area ( 8 mm2) one-dimensional grating of polymethylmethacrylate on Si(100). Structural, morphological and optical properties of the device have been studied. On-grating narrowing of the photoluminescence emission has been observed for the 492 nm grating period in correspondence to the 4f–4f Er band peak (at 1530 nm), indicating the possibility of optical gain for applications in the telecommunications

Tunable sulfur desorption in exfoliated MoS2 by means of thermal annealing in ultra-high vacuum

The effects of thermal annealing in ultra-high vacuum on the electronic structures of bulk and liquid exfoliated MoS2 have been studied by core level and valence band X-ray photoemission spectroscopy. A quantitative analysis of core level spectra demonstrates, in the case of exfoliated MoS2, that, upon annealing above 200 C, defect formation occurs in the form of sulfur single and double vacancies. Sulfur vacancies introduce surface states in the band gap (determined by the analysis of the valence band spectra). This determines a rigid shift of the core levels to lower binding energies, as a consequence of an upward band bending

The electronic structure of gas phase croconic acid compared to the condensed phase: More insight into the hydrogen bond interaction

The electronic structure of croconic acid in the gas phase has been investigated by means of core level and valence band photoemission spectroscopy and compared with hybrid Heyd-Scuseria-Ernzerhof density functional theory calculations. The results have been compared with the corresponding ones of the condensed phase. In the gas phase, due to the absence of hydrogen bond intermolecular interactions, the O 1 s core level spectrum shows a shift of binding energy between the hydroxyl (O–H) and the carbonyl group (C=O) of 2.1 eV, which is larger than the condensed phase value of 1.6 eV. Interestingly, such a shift decreases exponentially with the increase of the O–H distance calculated from theory. The significant differences between the gas and condensed phase valence band spectra highlight the important role played by the hydrogen bonding in shaping the electronic structure of the condensed phase

Use of Optical Contrast To Estimate the Degree of Reduction of Graphene Oxide

We report an optical contrast study of graphene oxide on 72 nm Al2O3/Si(100) and 300 nm SiO2/Si(100) as a function of its reduction degree. The reduction has been performed by means of ultrahigh vacuum thermal annealing from 25 °C (pristine graphene oxide) to 670 °C. In parallel to the optical contrast investigation, performed with optical microscopy, the graphene oxide films have been characterized with core level X-ray photoemission spectroscopy and micro- Raman spectroscopy. The optical contrast of graphene oxide (normalized to the one measured for pure graphene) on both substrates ranges from ∼0.4 to 1.0 for pristine and 670 °C annealed graphene oxide, respectively. Optical microscopy and X-ray photoemission spectroscopy data have been crosscorrelated, leading to calibration graphs that demonstrate that just by simply measuring the optical contrast of graphene oxide one can determine with very good approximation the fraction of sp2 hybridized carbon