Determination of the refractive index and wavelength‐dependent optical properties of few‐layer CrCl within the Fresnel formalism

Abstract

Based on previous reports on the optical microscopy contrast of mechanically exfoliated few layer CrCl 3 transferred on 285 nm and 270 nm SiO 2 on Si(100), we focus on the experimental determination of an effective mean complex refractive index via a fitting analysis based on the Fresnel equations formalism. Accordingly, the layer and wavelength-dependent absorbance and reflectance are calculated. Layer and wavelength-dependent optical contrast curves are then evaluated demonstrating that the contrast is significantly high only around welldefined wavelength bands. This is validated a posteriori, by experimental UV-Vis absorbance data. The present study aims to show the way towards the most reliable determination of thickness of the 2D material flakes during exfoliation.

Two-Dimensional CrCl3-Layered Trihalide Nanoflake Sensor for the Detection of Humidity, NO2, and H2

“…The characteristic Raman peaks of LPE CrCl 3 flakes at 116.5, 165.5, 208.5, 247, 300.2, and 345.0 cm –1 match the energy positions and relative intensities of mechanically exfoliated CrCl 3 flakes and bulk CrCl 3 crystals, highlighting that the proposed LPE effectively produces flakes with no appreciable strain as observed during mechanical exfoliation. UV–vis spectroscopy results also confirm these findings on LPE CrCl 3 (Supporting Information Figure S4b), and the UV–vis spectrum of NMP-exfoliated CrCl 3 exhibits the same absorption bands (peaks at approximately 530 and 729 nm) as the UV–vis spectrum of mechanically exfoliated 2D-CrCl 3 flakes with an estimated absorption coefficient of 170 L g –1 m –1 for the 530 nm absorption edge.…”

“…These empty cages, located at the center of the honeycomb lattice formed by Cr atoms (Figure a), similar to the model of Li adsorption over CrI 3 , can be spontaneously filled by ambient oxygen (red spheres in Figure a), resulting in the formation of an ordered semioxidized O–CrCl 3 surface phase, with oxygen impurities intercalated in the Cr atomic layer under ambient conditions, as recently demonstrated by theoretical and experimental observations. ,, Moreover, the presence of Cl vacancies in 2D-CrCl 3 flakes must be also considered, as indicated by the dotted-black circles in Figure a, which are energetically favorable, as proven in refs , . Consequently, the presence of the O–CrCl 3 phase and Cl vacancies induces a partial electron charge transfer from O and Cl atoms to Cr, ,, eventually encouraging the electrostatic interactions of ambient molecules over preferential atomic polar sites.…”

“…32,33,55 Moreover, the presence of Cl vacancies in 2D-CrCl 3 flakes must be also considered, as indicated by the dotted-black circles in Figure 9a, which are energetically favorable, as proven in refs 28,55. Consequently, the presence of the O−CrCl 3 phase and Cl vacancies induces a partial electron charge transfer from O and Cl atoms to Cr, 29,40,41 eventually encouraging the electrostatic interactions of ambient molecules over preferential atomic polar sites. 3.6.…”

Hot carrier dynamics of BiTeI with large Rashba spin splitting

“…Fresnel equations can be used to describe the reectivity of the materials, it have been used to study the 2-dimensional materials, such as MoS 2 , MoSe 2 , WS 2 , WSe 2 and CrCl 3 . 37,38 Here, we invite it to investigate the reectivity of BiTeI. Reectivity of a material under consideration can be described as R ¼ (n À n 0 )/(n + n 0 ) ¼ 1 À 2n 0 /(n + n 0 ), with n 0 ¼ 1, and n ¼ ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi 3 0 m 0 3 r m r p .…”

Synchrotron radiation photoemission spectroscopy of the oxygen modified CrCl3 surface

“…High-quality crystals of CrCl 3 were provided by the group of Prof. Tomasz Klimczuk and the preparation was explained in detail in the supplementary information (SI) and in recent references 26,27 . Some members of our group have reported the unexpected magnetic properties of exfoliated CrCl 3 compared to the bulk, which can also be read in SI.…”