Graphene is the first engineering electronic material, which is purely two-dimensional: it consists of two exposed sp2-hybridized carbon surfaces and has no bulk. Therefore, surface effects such as contamination by adsorbed polymer residues have a critical influence on its electrical properties and can drastically hamper its widespread use in devices fabrication. These contaminants, originating from mandatory technological processes of graphene synthesis and transfer, also impact fundamental studies of the electronic and structural properties at the atomic scale. Therefore, graphene-based technology and research requires “soft” and selective surface cleaning techniques dedicated to limit or to suppress this surface contamination. Here, we show that a high-density H2 and H2-N2 plasmas can be used to selectively remove polymeric residues from monolayer graphene without any damage on the graphene surface. The efficiency of this dry-cleaning process is evidenced unambiguously by a set of spectroscopic and microscopic methods, providing unprecedented insights on the cleaning mechanisms and highlighting the role of specific poly-methyl-methacrylate residues at the graphene interface. The plasma is shown to perform much better cleaning than solvents and has the advantage to be an industrially mature technology adapted to large area substrates. The process is transferable to other kinds of two-dimensional material and heterostructures.

Efficient nonlinear phenomena in integrated waveguides imply the realization in a nonlinear material of tightly confining waveguides sustaining guided modes with a small effective area with ultra-low propagation losses as well as high-power damage thresholds. However, when the waveguide cross-sectional dimensions keep shrinking, propagation losses and the probability of failure events tend to increase dramatically. In this work, we report both the fabrication and testing of high-confinement, ultralow-loss silicon nitride waveguides and resonators showing average attenuation coefficients as low as ∼3 dB/m across the S-, C-, and L bands for 1.6-µm-width × 800-nm-height dimensions, with intrinsic quality factors approaching ∼10 7 in the C band. The present technology results in very high cross-wafer device performance uniformities, low thermal susceptibility, and high power damage thresholds. In particular, we developed here an optimized fully subtractive process introducing a novel chemical-physical multistep annealing and encapsulation fabrication method, resulting in high quality Si 3 N 4-based photonic integrated circuits for energy-efficient nonlinear photonics and quantum optics.

Plasma oxidation of the c-Si substrate through a very thin gate oxide layer can be observed during HBr/O2/Ar based plasma overetch steps of gate etch processes. This phenomenon generates the so-called silicon recess in the channel and source/drain regions of the transistors. In this work, the authors compare the silicon recess generated by continuous wave HBr/O2/Ar plasmas and synchronous pulsed HBr/O2/Ar plasmas. Thin SiO2 layers are exposed to continuous and pulsed HBr/O2/Ar plasmas, reproducing the overetch process conditions of a typical gate etch process. Using in situ ellipsometry and angle resolved X-ray photoelectron spectroscopy, the authors demonstrate that the oxidized layer which leads to silicon recess can be reduced from 4 to 0.8 nm by pulsing the plasma in synchronous mode.

Summary: A line‐shaped atmospheric pressure filamentary plasma is developed to carry out the open air deposition of silicon oxide films from N2/hexamethyldisoxane (HMDSO) mixtures with/without adding oxygen. FT‐IR, XPS, SEM, and ellipsometry were used to analyse the samples. It is found that the deposited films present mainly inorganic characteristics even without an oxygen admixture in the open air system. Smooth, continuous, and uniform films can be formed at relatively low monomer content. By increasing the monomer content for a fixed power density or oxygen in the input gases, the deposition rates increase and then show a plateau, suggesting that there exists saturation values for the deposition rates corresponding to the monomer and oxygen content. By the comparison of films deposited in the open air device and in a controlled nitrogen atmosphere in the same device, the important role of the oxygen in the open air reactor has been shown. This study exhibits a potential of open air deposition at atmospheric pressure to form SiO2 films for large‐scale deposition.

It is known that graphene surface contaminations by residues affect drastically its intrinsic properties and cannot be avoided when chemical vapor deposited (CVD) graphene is transferred on other substrates. In this work, we investigate by X‐ray photoelectron spectroscopy and work function measurements using X‐ray photoemission electron microscopy the capabilities of high‐density plasmas to clean graphene. The evolution of different chemical species at surface is monitored as a function of plasma exposure. H2 plasmas are shown to clean efficiently PMMA residues from CVD graphene on Cu. However, when the same plasma is used on graphene transferred on SiO2/Si substrate a liftoff of the graphene layer is observed before the end of cleaning procedure. These results are discussed in terms of H+ penetration through graphene and H2 formation between the SiO2 substrate and graphene. Using Cl‐based chemistries, we found that the plasma is able to etch polymeric contamination at the graphene surface. It is also found that the plasma induces spreading of the Si nanoparticle contamination that hampers the cleaning process. Copyright © 2016 John Wiley & Sons, Ltd.

The directed self-assembly (DSA) of block copolymers (BCPs) is a powerful method for the manufacture of high-resolution features. Critical issues remain to be addressed for successful implementation of DSA, such as dewetting and controlled orientation of BCP domains through physicochemical manipulations at the BCP interfaces, and the spatial positioning and registration of the BCP features. Here, we introduce novel top-coat (TC) materials designed to undergo cross-linking reactions triggered by thermal or photoactivation processes. The cross-linked TC layer with adjusted composition induces a mechanical confinement of the BCP layer, suppressing its dewetting while promoting perpendicular orientation of BCP domains. The selection of areas of interest with perpendicular features is performed directly on the patternable TC layer via a lithography step and leverages attractive integration pathways for the generation of locally controlled BCP patterns and nanostructured BCP multilayers.

Hexamethyldisiloxane was used to deposit silicon dioxide thin films using a low frequency plasma reactor at low pressure as well as a dielectric barrier discharge (DBD) at atmospheric pressure. FT‐IR, XPS, EIS, SEM and ellipsometry were used to analyse the samples. The results show that, at low pressure, the deposited films which are smooth, continuous and dense present a polymer‐like structure. By carrying out the film deposition after an oxygen plasma pretreatment step, a further improvement in the protective properties is achieved, which is observed in the case of SiOχ coatings with 13.56 MHz RF generators.1 At atmospheric pressure, the deposited films present an inorganic character deposited in open air and a polymer‐like one deposited under a controlled nitrogen atmosphere in our DBD reactor. The latter also allows continuous films which present the best anti‐corrosive properties (which have been studied for the first time for anti‐corrosive properties) when they contain some carbon incorporated.

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