Nanotexturing To Enhance Photoluminescent Response of Atomically Thin Indium Selenide with Highly Tunable Band Gap.
Brotons-Gisbert, Mauro et al.
Optical contrast of 2D InSe on SiO2/Si and transparent substrates using bandpass filters
The particular optical and electronic properties recently reported for 2D InSe depict this 2D material as being very versatile for future electronic and optoelectronic devices with tunable and optimized functionalities. For its fundamental study and the development of practical applications, rapid and accurate identification methods of atomically thin InSe are essential. Here, we demonstrate an enhancement of the optical contrast between InSe nanosheets and the underlying SiO2/Si substrate by illuminating with a 40 nm wide bandpass filter centered at 500 nm. Moreover, we study the optical contrast of 2D InSe on transparent substrates. Our results suggest that a good optical contrast is achi…
Optical Contrast and Raman Spectroscopy Techniques Applied to Few-Layer 2D Hexagonal Boron Nitride
The successful integration of few-layer thick hexagonal boron nitride (hBN) into devices based on two-dimensional materials requires fast and non-destructive techniques to quantify their thickness. Optical contrast methods and Raman spectroscopy have been widely used to estimate the thickness of two-dimensional semiconductors and semi-metals. However, they have so far not been applied to two-dimensional insulators. In this work, we demonstrate the ability of optical contrast techniques to estimate the thickness of few-layer hBN on SiO2/Si substrates, which was also measured by atomic force microscopy. Optical contrast of hBN on SiO2/Si substrates exhibits a linear trend with the number of h…
Out-of-plane orientation of luminescent excitons in atomically thin indium selenide flakes
Van der Waals materials offer a wide range of atomic layers with unique properties that can be easily combined to engineer novel electronic and photonic devices. A missing ingredient of the van der Waals platform is a two-dimensional crystal with naturally occurring out-of-plane luminescent dipole orientation. Here we measure the far-field photoluminescence intensity distribution of bulk InSe and two-dimensional InSe, WSe$_2$ and MoSe$_2$. We demonstrate, with the support of ab-initio calculations, that layered InSe flakes sustain luminescent excitons with an intrinsic out-of-plane orientation, in contrast with the in-plane orientation of dipoles we find in two-dimensional WSe$_2$ and MoSe$…
Quantum size confinement in gallium selenide nanosheets: band gap tunability versus stability limitation
Abstract Gallium selenide is one of the most promising candidates to extend the window of band gap values provided by existing two-dimensional semiconductors deep into the visible potentially reaching the ultraviolet. However, the tunability of its band gap by means of quantum confinement effects is still unknown, probably due to poor nanosheet stability. Here, we demonstrate that the optical band gap band of GaSe nanosheets can be tuned by ∼120 meV from bulk to 8 nm thick. The luminescent response of very thin nanosheets (<8 nm) is strongly quenched due to early oxidation. Oxidation favors the emergence of sharp material nanospikes at the surface attributable to strain relaxation. Simul…
Two-Dimensional Indium Selenide for Sulphur Vapour Sensing Applications
Surface-to-volume ratio in two-dimensional (2D) materials highlights among their characteristics as an inherent and intrinsic advantage taking into account their strong sensitivity to surface effects. For this reason, we have proposed in this work micromechanically exfoliated 2D nanosheets of InSe as an optical vapour sensor. As a proof of concept, we used 2-mercaptoethanol as the chemical analyte in vapour phase to monitor the change of the InSe photoluminescence (PL) before and after exposure to the analyte. For short vapour exposure times (at low analyte concentration), we found a PL enhancement of InSe nanosheets attributed to the surface localization of Se defects. For long vapour expo…
Optical and dielectric properties of MoO 3 nanosheets for van der Waals heterostructures
Two-dimensional (2D) insulators are a key element in the design and fabrication of van der Waals heterostructures. They are vital as transparent dielectric spacers whose thickness can influence both the photonic, electronic, and optoelectronic properties of 2D devices. Simultaneously, they provide protection of the active layers in the heterostructure. For these critical roles, hexagonal Boron Nitride (hBN) is the dominant choice due to its large bandgap, atomic flatness, low defect density, and encapsulation properties. However, the broad catalogue of 2D insulators offers exciting opportunities to replace hBN in certain applications that require transparent thin layers with additional opti…
Enhanced optical response of InSe nanosheet devices decorated with CsPbX3 (X = I, Br) perovskite nanocrystals
Abstract The combination of several two-dimensional materials opens the door for the creation of cooperative nanodevices with functionalities that complement to each other and even compensate the weaknesses of the individual components. Two-dimensional indium selenide (InSe) shows one of the largest tunability bandgap found in two-dimensional materials with application in optoelectronics. However, the intrinsic out-of-plane luminescent dipolar nature limits its implementation in devices operating in vertical configuration. All-inorganic CsPbX3 (X = Br, I) cubic nanoparticles offer high absorption and emission quantum yields and great integrability with two-dimensional materials. Combining t…
Out-of-plane orientation of luminescent excitons in two-dimensional indium selenide.
Van der Waals materials offer a wide range of atomic layers with unique properties that can be easily combined to engineer novel electronic and photonic devices. A missing ingredient of the van der Waals platform is a two-dimensional crystal with naturally occurring out-of-plane luminescent dipole orientation. Here we measure the far-field photoluminescence intensity distribution of bulk InSe and two-dimensional InSe, WSe2 and MoSe2. We demonstrate, with the support of ab-initio calculations, that layered InSe flakes sustain luminescent excitons with an intrinsic out-of-plane orientation, in contrast with the in-plane orientation of dipoles we find in two-dimensional WSe2 and MoSe2 at room-…