Graphene

Graphene is foreseen for a handful of electronic and optoelectronic nano-devices. Making nano-devices out of graphene requires nanopatterning. Determining the quality of patterned graphene is essential and the detection of defects demands a sensitive chemical nano-characterization tool.

The Fluorolog-QM fluorescence spectrometer with an integrating sphere option is an excellent choice for PLQY measurements in NIR. The K-Sphere is very convenient and easy to use, as it couples directly to the sample compartment optics and allows a use of external light sources, such as DPSS lasers, which can be attached to the front of the sample compartment. The sphere has holders for cuvettes, slides and powders that can be easily interchanged. The results demonstrate very good reproducibility and precision for NIR PLQY measurements spanning almost two orders of magnitude. Based on multiple measurements, the demonstrated PLQY standard deviations range from 1.3% for high QY value (77%) to 6.4% for the QY below 1%.

The new Fluorolog-QM spectrofluorometers, due to their modularity and advanced software and a universal interface, are an ideal choice for studying multiple aspects of upconversion. This technical note illustrates the use of Fluorolog-QM-75-21 for spectral and time-resolved characterization of these materials.

Graphene, a single layer of carbon atoms arranged in a two-dimensional honeycomb lattice, exhibits remarkable electrical, thermal, and mechanical properties, making it a subject of extensive research in various scientific fields.

Graphene oxide is a nanocarbon material with a high aspect ratio and a high surface area with a thickness of about 1 nm and a sheet length of several to tens of microns.

Visualizing the distribution of structural defects and functional groups present on the surface of two-dimensional (2D) materials such as graphene oxide challenges the sensitivity and spatial resolution of most advanced analytical techniques.

The use of TERS to reveal the defects density in the structure of CNTs is of interest for a better understanding of the electrical properties of the devices made with such nano-objects. Not only defects concentration but also local chirality changes from the different radial breathing modes, pressure effect and strain distribution can be studied at the single carbon nanotube level through TERS.

Spectroscopic ellipsometry (SE) is used to determine the optical constants of C60 and C70 thin films over the range 0.6-6.5eV (i.e. 190-2100nm). The information provided by the optical constants allows for a better understanding of the electronic structure of these materials.

The UVISEL Spectroscopic Ellipsometer is the ideal tool for reliable film thickness and optical constants characterization of amorphous carbon coatings, even in difficult cases where the film thickness is very thin. Roughness, and interface "adhesion" can also been determined.

Raman has shown a high potential in characterising the SWCNTs' structure. The correlation between knowledge about structure with physical and chemical properties about the tubes make the technique extremely powerful to control the quality of the SWCNTs for specific applications. Raman spectrometer capabilities like spatial resolution, spectral resolution and excitation wavelength versatility have been examined. Beside Raman, preliminary fluorescence studies are describing the potential of the technique.

The Raman spectra of the various forms of elemental carbon are very sensitive to the type of nearest neighbour bonding, and to intermediate and long range order. In many cases Raman spectroscopy is the technique of choice for characterization of carbon materials. Correlation of Raman spectral features with tribological properties can facilitate the deposition of carbon films.

Graphene is a new nanomaterial which may partially replace silicon in microcircuits and computer chips in the future. In order to better understand its quality characteristics, fast reliable techniques that deliver the right property measures are needed. Raman spectroscopy has emerged as a key technique for studying this exceptional material.

In this work, spectroscopic ellipsometry (SE) was successfully applied to characterize the optical properties and the thicknesses of doped and undoped diamond layers. The sensitivity of this technique enables the doped layer to be distinguished from the undoped one in a sample consisting of a stack of these two layers. Moreover, an interface between the two layers has been detected. This work and others reported previously show clearly that ellipsometry is the technique of choice for the characterization of optical and structural properties of layered materials thanks to its sensitivity and the wide range of information it provides.

The Raman spectra of elemental carbon materials are known to be sensitive to polymorphy. For hard carbon films, the spectra of amorphous and diamond-like carbons can be band-fit to separate the contributions of the "graphitic carbon" (G band) from the "disordered carbon" (D band). The spectral behaviour of carbon films has been empirically correlated with thin film physical properties such as hardness, durability, optical transparency, electrical conductivity, thermal conductivity and corrosion resistance, and can be of use for prediction of these properties without extensive alternative testing. The DiskRam has been designed to automate the collection of Raman spectra from hard carbon coatings on computer hard disk media and the extraction of parameters that are well correlated with the properties of the films. The extracted information is output in spreadsheet format for SPC at a manufacturing facility.

The colour enhancement treatment on native brown and yellow diamonds can be highlighted by Photoluminescence analyses performed with the Raman spectrometer LabRAM HR. The PL signature of green and violet diamonds has also been recorded. The defect centres responsible of the colour of the diamonds have all been detected and assigned. This proves the Raman spectrometer to be a very good tool to investigate the fine defects in the Diamond structure by Photoluminescence analysis.