Sequential infiltration synthesis (SIS) provides a successful route to grow inorganic materials into polymeric films by penetrating of gaseous precursors into the polymer, both in order to enhance the functional properties of the polymer creating an organic-inorganic hybrid material, and to fabricate inorganic nanostructures when infiltrating in patterned polymer films or in selfassembled block copolymers. A SIS process consists in a controlled sequence of metal organic precursor and co-reactant vapor exposure cycles of the polymer films in an atomic layer deposition (ALD) reactor. In this work, we present a study of the SIS process of alumina using trimethylaluminum (TMA) and H2O in various polymer films using in situ dynamic spectroscopic ellipsometry (SE). In situ dynamic SE enables time-resolved monitoring of the swelling of the polymer, which is relevant to the diffusion and retain of the metal precursor into the polymer itself. Different swelling behaviour of poly(methylmethacrylate) (PMMA) and polystyrene (PS) was observed when exposed to TMA vapor. PMMA films swell more significantly than PS films do, resulting in very different infiltrated Al2O3 thickness after polymer removal in O2 plasma. PMMA films reach different swollen states upon TMA exposure and reaction with H2O, depending on the TMA dose and on the purge duration after TMA exposure, which correspond to different amounts of metal precursor retained inside the polymer and converted to alumina. Diffusion coefficients of TMA in PMMA were extracted investigating the swelling of pristine PMMA films during TMA infiltration and shown to be dependent on polymer molecular weight. In situ dynamic SE monitoring allows to control the SIS process tuning it from an ALD-like process for long purge to a chemical vapour deposition-like process selectively confined inside the polymer films.

The stabilization of silicene at ambient conditions is essential for its characterization, future processing and device integration. Here, we demonstrate in-situ encapsulation of silicene on Ag(111) by exfoliated few-layer graphene (FLG) flakes, allowing subsequent Raman analysis under ambient conditions. Raman spectroscopy measurements proved that FLG capping serves as an effective passivation, preventing degradation of silicene for up to 48 hours.The acquired data are consistent with former in-situ Raman measurements, showing two characteristic peaks, located at 216 cm -1 and 515 cm -1 . Polarization-dependent measurements allowed to identify the two modes as A and E, demonstrating that the symmetry properties of silicene are unaltered by the capping process.

Many of graphene’s remarkable properties arise from its linear dispersion of the electronic states, forming a Dirac cone at the K points of the Brillouin zone. Silicene, the 2D allotrope of silicon, is also predicted to show a similar electronic band structure, with the addition of a tunable bandgap, induced by spin–orbit coupling. Because of these outstanding electronic properties, silicene is considered as a promising building block for next-generation electronic devices. Recently, it has been shown that silicene grown on Au(111) still possesses a Dirac cone, despite the interaction with the substrate. Here, to fully characterize the structure of this 2D material, we investigate the vibrational spectrum of a monolayer silicene grown on Au(111) by polarized Raman spectroscopy. To enable a detailed ex situ investigation, we passivated the silicene on Au(111) by encapsulating it under few layers hBN or graphene flakes. The observed spectrum is characterized by vibrational modes that are strongly red-shifted with respect to the ones expected for freestanding silicene. By comparing low-energy electron diffraction (LEED) patterns and Raman results with first-principles calculations, we show that the vibrational modes indicate a highly (>7%) biaxially strained silicene phase.

than simply decorating the surface. [2][3][4] SIS allows transforming polymers into organic-inorganic hybrid materials: penetration and reaction of gaseous metal precursors into polymer, during SIS, permit to grow inorganic materials into polymeric films [5] in order to tune some of their features as their optical properties or improve their chemical etch resistance. [6][7][8][9] The SIS process is characterized by two factors: diffusion and entrapment of precursor molecules into the polymer matrix. The most direct method to promote their entrapment is the chemical reaction of penetrant molecules with polymer functional groups in combination with a secondary precursor (coreactant). [4] Thus, the number of reactive sites within the polymer film plays an important role in the determination of the amount of inorganic material grown in the film during the process. Moreover, differently from ALD, the self-terminating reactions are not restricted to the surface sites. Precursor molecules must diffuse into the polymeric film to reach the reactive sites that are distributed in the volume of the polymeric matrix. Consequently, diffusion plays a fundamental part in the kinetics of the infiltration process and needs to be monitored in real time. The most used in situ techniques for investigating the infiltration mechanism are in situ quartz crystal microbalance (QCM) measurements and in situ Fourier transform infrared (FTIR) spectroscopy. [10][11][12][13] In situ dynamic spectroscopic ellipsometry (SE) was recently validated as a valuable tool for real time investigation of the infiltration process in poly(methyl methacrylate) (PMMA) and polystyrene (PS) homopolymers. [14] In situ SE is a noninvasive optical technique frequently used in combination with ALD processes [15][16][17] and for studies of polymer films under several conditions. [18][19][20] During SIS process, in situ SE allows continuous acquisition of information about changes of thickness and refractive index (n) of polymer films without interrupting the process itself on a shorter time scale than in situ FTIR spectroscopic analysis and without the need of ad hoc samples as for QCM measurements. When SIS is performed into self-assembled block copolymers (BCP), [21] the selective binding of precursors to one domain only of BCPs offers the possibility to fabricate inorganic functional nanoarchitectures [22] or hard masks for lithography. [23] Removing polymers by O 2 plasma after Sequential infiltration synthesis (SIS) consists in a controlled sequence of metal organic precursors and coreactant vapor exposure cycles of polymer films. Two aspects characterize an SIS process: precursor molecule diffusion within the polymer matrix and precursor molecule entrapment into polymer films via chemical reaction. In this paper, SIS process for the alumina synthesis is investigated using trimethylaluminum (TMA) and H 2 O in thin films of poly(styrene-random-methyl methacrylate) (P(S-r-MMA)) with variable MMA content. The amount of alumina grown in the P(S-r-MMA) films linear...