Silicon‐Based Photonic Architectures from Hierarchically Porous Carbon Opals

Abstract

Silicon‐based materials are needed in cutting‐edge technological fields, for which hierarchical porosity and photonic properties help improve performance. In this work, the versatility of several fabrication routes that combine silicon infiltration by chemical vapor deposition (CVD), reactive ion etching (RIE), and carbon calcination, which produce a palette of novel silicon‐based material architectures, is demonstrated. Design strategies are discussed and the main features of the processing steps are addressed to provide a variety of new silicon‐based materials with high morphological versatility and photonic quality. Three‐dimensional hollow carbon opals (HCO) permit control of the porosity of subsequent architectures through the initial silicon infiltration, while open or closed surfaces are achieved primarily as a function of RIE conditions. The composition of derived structures depends on the sequence in which the processes are applied. As a result, pure Si and hybrid C–Si inverse structures can be produced with open or closed spheres in the top layer and with an optional passivation layer. Remarkably, by properly choosing the Si infiltration parameters and the calcination/RIE procedure, final structures are achieved with double‐shell spheres.

Effect of thermal treatments on chiral nematic cellulose nanocrystal films

“…Regardless of the birefringence loss that could have happened upon carbonisation, the pitch of the retained helicoidal architecture is of the order of 215-235 nm, therefore too small to induce selective reflection above 400 nm to appear in the visible range (Parker et al, 2018). Interestingly, the shape of the original cellulose nanorods appeared to be retained in the carbonaceous structure, as well as heterogeneities in the pitch and in the cut; this indicates minimal thermal deformation of the cellulose nanocrystals shape during the thermal treatment, making it an interesting system for producing hierarchically organized 3D carbonaceous materials (Gil-Herrera et al, 2020;Herou et al, 2019;Kubo et al, 2013;Shopsowitz et al, 2011;Yan et al, 2016). While the helicoidal architecture of the films was retained for thermal treatments at 900 C, this was not uniformly observed throughout the films' cross-section.…”

Novel Design of Superhydrophobic and Anticorrosive PTFE and PAA + β − CD Composite Coating Deposited by Electrospinning, Spin Coating and Electrospraying Techniques

“…292 to 690 eV, respectively. Detailed peak shape analysis of C 1s emission were performed by the deconvolution of the C 1s spectrum with several Gaussian/Lorentzian symmetric components (ratio of 70/30) by using a least-squares fitting routine [ 48 ]. The energy position of the peaks and their relative heights were determined to account for the emission ascribed to the different chemical environment of carbon atoms) according to the values reported in previous works [ 57 , 58 ].…”

“…To complete this information, an analysis of the elemental and chemical composition of PAA, β-CD, PTFE (reference samples), S1, S2, S3, and S4 set of samples was performed by X-ray photoelectron spectroscopy (XPS). These experiments were carried out in a UHV chamber with a base pressure of 10 −10 mbar equipped with a hemispherical electron energy analyzer (SPECS Phoibos 150 spectrometer) and a 2D delay-line detector, by using an X-ray source of Mg-Kα (1253.6 eV) [ 48 ]. XPS spectra were acquired at normal emission take-off angle by using an energy step of 0.50 and 0.10 eV and a pass energy of 40 and 20 eV for survey spectra and detailed core-level regions, respectively.…”