arXiv subjects

Antonios Michail

Publications and source records attributed to Antonios Michail.

3 recordsLinked to original sources

arXiv2024

Strain distribution in WS2 monolayers detected through Polarization-resolved Second Harmonic Generation

Two-dimensional (2D) graphene and graphene-related materials (GRMs) show great promise for future electronic devices. Nevertheless, GRMs result distinct properties under the influence of the substrate that serves as support through uneven compression/ elongation of GRMs surface atoms. Strain in GRM monolayers is the most common feature that alters the interatomic distances, band structure, providing a new degree of freedom that allows regulation of their electronic properties and introducing the field of straintronics. Having an all-optical detection, a minimally invasive tool that rapidly probes strain in large areas of GRM monolayers, would be of great importance in the research and development of novel 2D devices. Here, we use Polarization-resolved Second Harmonic Generation (P-SHG) optical imaging to identify strain distribution, induced in a single layer of WS2 placed on a pre-patterned Si/SiO2 substrate with cylindrical wells. By fitting the P-SHG data pixel-by-pixel, we produce spatially resolved images of the crystal armchair direction. In regions where the WS2 monolayer conforms to the pattern topography, a distinct cross-shaped pattern is evident in the armchair image owing to strain. The presence of strain in these regions is independently confirmed using a combination of atomic force microscopy and Raman mapping.

physics.app-ph↗

arXiv2023

Biaxial Tensile Strain Enhances Electron Mobility of Monolayer Transition Metal Dichalcogenides

Strain engineering can modulate the material properties of two-dimensional (2D) semiconductors for electronic and optoelectronic applications. Recent theory and experiments have found that uniaxial tensile strain can improve the electron mobility of monolayer MoS$_2$, a 2D semiconductor, but the effects of biaxial strain on charge transport are not well-understood in 2D semiconductors. Here, we use biaxial tensile strain on flexible substrates to probe the electron mobility in monolayer WS$_2$ and MoS$_2$ transistors. This approach experimentally achieves ~2x higher on-state current and mobility with ~0.3% applied biaxial strain in WS$_2$, the highest mobility improvement at the lowest strain reported to date. We also examine the mechanisms behind this improvement through density functional theory simulations, concluding that the enhancement is primarily due to reduced intervalley electron-phonon scattering. These results underscore the role of strain engineering 2D semiconductors for flexible electronics, sensors, integrated circuits, and other optoelectronic applications.

cond-mat.mes-hall↗

arXiv2018

Optical detection of strain and doping inhomogenieties in single layer MoS2

Van der Waals single-layer materials are characterized by an inherent extremely low bending rigidity and therefore are prone to nanoscale structural modifications due to substrate interactions. Such interactions can induce excess charge concentration, conformational ripples and residual mechanical strain. In this work, we employed spatially resolved Raman and Photoluminescence images to investigate strain and doping inhomogeneities in a single layer exfoliated Molybdenum disulphide crystal. We have found that correlations between the spectral parameters of the most prominent Raman bands A1' and E' enable us to decouple and quantify strain and charge doping effects. In comparison with AFM topography, we show that the spatial distribution of the linewidth of the A-exciton peak is strain sensitive and can capture features smaller than the laser spot size. The presented optical analysis may have implications in the development of high-quality devices based on two-dimensional materials since structural and electronic modifications affect considerably their carrier mobility and conductivity.

cond-mat.mtrl-sci↗