Browse
Submit Data
Databases
API
Help

Dataset Information

0 Views

0 Connections

0 Citations

0 Reanalyses

0 Downloads

Omics score: 0

Temperature induced crossing in the optical bandgap of mono and bilayer MoS2 on SiO2.

ABSTRACT: Photoluminescence measurements in mono- and bilayer-MoS2 on SiO2 were undertaken to determine the thermal effect of the MoS2/SiO2 interface on the optical bandgap. The energy and intensity of the photoluminescence from monolayer MoS2 were lower and weaker than those from bilayer MoS2 at low temperatures, whilst the opposite was true at high temperatures above 200?K. Density functional theory calculations suggest that the observed optical bandgap crossover is caused by a weaker substrate coupling to the bilayer than to the monolayer.

SUBMITTER: Park Y

PROVIDER: S-EPMC5876333 | biostudies-literature | 2018 Mar

REPOSITORIES: biostudies-literature

ACCESS DATA

Json Xml

Publications

Temperature induced crossing in the optical bandgap of mono and bilayer MoS2 on SiO2.

Park Youngsin Y Chan Christopher C S CCS Taylor Robert A RA Kim Yongchul Y Kim Nammee N Jo Yongcheol Y Lee Seung W SW Yang Woochul W Im Hyunsik H Lee Geunsik G

Scientific reports 20180329 1

Photoluminescence measurements in mono- and bilayer-MoS2 on SiO2 were undertaken to determine the thermal effect of the MoS2/SiO2 interface on the optical bandgap. The energy and intensity of the photoluminescence from monolayer MoS2 were lower and weaker than those from bilayer MoS2 at low temperatures, whilst the opposite was true at high temperatures above 200 K. Density functional theory calculations suggest that the observed ...[more]

PMID: 29599429

Similar Datasets

Monolayer MoS2 Bandgap Modulation by Dielectric Environments and Tunable Bandgap Transistors.

Project description:Semiconductors with a moderate bandgap have enabled modern electronic device technology, and the current scaling trends down to nanometer scale have introduced two-dimensional (2D) semiconductors. The bandgap of a semiconductor has been an intrinsic property independent of the environments and determined fundamental semiconductor device characteristics. In contrast to bulk semiconductors, we demonstrate that an atomically thin two-dimensional semiconductor has a bandgap with strong dependence on dielectric environments. Specifically, monolayer MoS2 bandgap is shown to change from 2.8?eV to 1.9?eV by dielectric environment. Utilizing the bandgap modulation property, a tunable bandgap transistor, which can be in general made of a two-dimensional semiconductor, is proposed.

| S-EPMC4932597 | biostudies-literature

Strain-Induced Spatial and Spectral Isolation of Quantum Emitters in Mono- and Bilayer WSe2.

Project description:Two-dimensional transition metal dichalcogenide semiconductors are intriguing hosts for quantum light sources due to their unique optoelectronic properties. Here, we report that strain gradients, either unintentionally induced or generated by substrate patterning, result in spatially and spectrally isolated quantum emitters in mono- and bilayer WSe2. By correlating localized excitons with localized strain variations, we show that the quantum emitter emission energy can be red-tuned up to a remarkable ?170 meV. We probe the fine-structure, magneto-optics, and second-order coherence of a strained emitter. These results raise the prospect of strain-engineering quantum emitter properties and deterministically creating arrays of quantum emitters in two-dimensional semiconductors.

| S-EPMC4643357 | biostudies-literature

Stacked bilayer phosphorene: strain-induced quantum spin Hall state and optical measurement.

Project description:Bilayer phosphorene attracted considerable interest, giving a potential application in nanoelectronics owing to its natural bandgap and high carrier mobility. However, very little is known regarding the possible usefulness in spintronics as a quantum spin Hall (QSH) state of material characterized by a bulk energy gap and gapless spin-filtered edge states. Here, we report a strain-induced topological phase transition from normal to QSH state in bilayer phosphorene, accompanied by band-inversion that changes number from 0 to 1, which is highly dependent on interlayer stacking. When the bottom layer is shifted by 1/2 unit-cell along zigzag/armchair direction with respect to the top layer, the maximum topological bandgap 92.5 meV is sufficiently large to realize QSH effect even at room-temperature. An optical measurement of QSH effect is therefore suggested in view of the wide optical absorption spectrum extending to far infra-red, making bilayer phosphorene a promising candidate for opto-spintronic devices.

| S-EPMC4570210 | biostudies-literature

Structure and optical bandgap relationship of π-conjugated systems.

Project description:In bulk heterojunction photovoltaic systems both the open-circuit voltage as well as the short-circuit current, and hence the power conversion efficiency, are dependent on the optical bandgap of the electron-donor material. While first-principles methods are computationally intensive, simpler model Hamiltonian approaches typically suffer from one or more flaws: inability to optimize the geometries for their own input; absence of general, transferable parameters; and poor performance for non-planar systems. We introduce a set of new and revised parameters for the adapted Su-Schrieffer-Heeger (aSSH) Hamiltonian, which is capable of optimizing geometries, along with rules for applying them to any [Formula: see text]-conjugated system containing C, N, O, or S, including non-planar systems. The predicted optical bandgaps show excellent agreement to UV-vis spectroscopy data points from literature, with a coefficient of determination [Formula: see text], a mean error of -0.05 eV, and a mean absolute deviation of 0.16 eV. We use the model to gain insights from PEDOT, fused thiophene polymers, poly-isothianaphthene, copolymers, and pentacene as sources of design rules in the search for low bandgap materials. Using the model as an in-silico design tool, a copolymer of benzodithiophenes along with a small-molecule derivative of pentacene are proposed as optimal donor materials for organic photovoltaics.

| S-EPMC3908919 | biostudies-literature

Quantum spin Hall insulator with a large bandgap, Dirac fermions, and bilayer graphene analog.

Project description:The search for room temperature quantum spin Hall insulators (QSHIs) based on widely available materials and a controlled manufacturing process is one of the major challenges of today's topological physics. We propose a new class of semiconductor systems based on multilayer broken-gap quantum wells, in which the QSHI gap reaches 60 meV and remains insensitive to temperature. Depending on their layer thicknesses and geometry, these novel structures also host a graphene-like phase and a bilayer graphene analog. Our theoretical results significantly extend the application potential of topological materials based on III-V semiconductors.

| S-EPMC5930414 | biostudies-literature

High-Speed Imaging of Second-Harmonic Generation in MoS2 Bilayer under Femtosecond Laser Ablation.

Project description:We report an in situ characterization of transition-metal dichalcogenide (TMD) monolayers and twisted bilayers using a high-speed second-harmonic generation (SHG) imaging technique. High-frequency laser modulation and galvano scanning in the SHG imaging enabled a rapid identification of the crystallinity in the TMD, including the orientation and homogeneity with a speed of 1 frame/s. For a twisted bilayer MoS2, we studied the SHG peak intensity and angles as a function of the twist angle under a strong interlayer coupling. In addition, rapid SHG imaging can be used to visualize laser-induced ablation of monolayer and bilayer MoS2 in situ under illumination by a strong femtosecond laser. Importantly, we observed a characteristic threshold behavior; the ablation process occurred for a very short time duration once the preheating condition was reached. We investigated the laser thinning of the bilayer MoS2 with different twist angles. When the twist angle was 0°, the SHG decreased by approximately one-fourth of the initial intensity when one layer was removed. Conversely, when the twist angle was approximately 60° (the SHG intensity was suppressed), the SHG increased abruptly close to that of the nearby monolayer when one layer was removed. Precise layer-by-layer control was possible because of the unique threshold behavior of the laser-induced ablation.

| S-EPMC8308356 | biostudies-literature

High-Performance CVD Bilayer MoS2 Radio Frequency Transistors and Gigahertz Mixers for Flexible Nanoelectronics.

Project description:Two-dimensional (2D) MoS2 have attracted tremendous attention due to their potential applications in future flexible high-frequency electronics. Bilayer MoS2 exhibits the advantages of carrier mobility when compared with monolayer mobility, thus making the former more suitable for use in future flexible high-frequency electronics. However, there are fewer systematical studies of chemical vapor deposition (CVD) bilayer MoS2 radiofrequency (RF) transistors on flexible polyimide substrates. In this work, CVD bilayer MoS2 RF transistors on flexible substrates with different gate lengths and gigahertz flexible frequency mixers were constructed and systematically studied. The extrinsic cutoff frequency (fT) and maximum oscillation frequency (fmax) increased with reducing gate lengths. From transistors with a gate length of 0.3 μm, we demonstrated an extrinsic fT of 4 GHz and fmax of 10 GHz. Furthermore, statistical analysis of 14 flexible MoS2 RF transistors is presented in this work. The study of a flexible mixer demonstrates the dependence of conversion gain versus gate voltage, LO power and input signal frequency. These results present the potential of CVD bilayer MoS2 for future flexible high-frequency electronics.

| S-EPMC8072592 | biostudies-literature

Polar coupling enabled nonlinear optical filtering at MoS2/ferroelectric heterointerfaces.

Project description:Complex oxide heterointerfaces and van der Waals heterostructures present two versatile but intrinsically different platforms for exploring emergent quantum phenomena and designing new functionalities. The rich opportunity offered by the synergy between these two classes of materials, however, is yet to be charted. Here, we report an unconventional nonlinear optical filtering effect resulting from the interfacial polar alignment between monolayer MoS2 and a neighboring ferroelectric oxide thin film. The second harmonic generation response at the heterointerface is either substantially enhanced or almost entirely quenched by an underlying ferroelectric domain wall depending on its chirality, and can be further tailored by the polar domains. Unlike the extensively studied coupling mechanisms driven by charge, spin, and lattice, the interfacial tailoring effect is solely mediated by the polar symmetry, as well explained via our density functional theory calculations, pointing to a new material strategy for the functional design of nanoscale reconfigurable optical applications.

| S-EPMC7078226 | biostudies-literature

Electrical and Optical Properties of Silicon OxideLignin Polylactide (SiO2-L-PLA).

Project description:This paper presents a study on the electrical properties of new polylactide-basednanocomposites with the addition of silicon-dioxide-lignin nanoparticles and glycerine as a plasticizer.Four samples were prepared with nanoparticle mass fractions ranging between 0.01 to 0.15(0.01, 0.05, 0.10, and 0.15), and three samples were prepared without nanoparticle filler-unfilledand unprocessed polylactide, unfilled and processed polylactide, and polylactide with Fusabondand glycerine. All samples were manufactured using the melt mixing extrusion techniqueand injection molding. Only the unfilled and unprocessed PLA sample was directly preparedby injection molding. Dielectric properties were studied with broadband spectroscopy in a frequencyrange from 0.1 Hz to 1 MHz in 55 steps designed on a logarithmic scale and a temperature rangefrom 293.15 to 333.15 K with a 5 K step. Optical properties of nanocomposites were measuredwith UV-VIS spectroscopy at wavelengths from 190 to 1100 nm. The experimental data show thatthe addition of silicon-dioxide-lignin and glycerine significantly affected the electrical propertiesof the studied nanocomposites based on polylactide. Permittivity and electrical conductivity showa significant increase with an increasing concentration of nanoparticle filler. The optical properties arealso affected by nanofiller and cause an increase in absorbance as the number of silicon-dioxide-ligninnanoparticles increase.

| S-EPMC7144936 | biostudies-literature

Interfacial Properties of Monolayer and Bilayer MoS2 Contacts with Metals: Beyond the Energy Band Calculations.

Project description:Although many prototype devices based on two-dimensional (2D) MoS2 have been fabricated and wafer scale growth of 2D MoS2 has been realized, the fundamental nature of 2D MoS2-metal contacts has not been well understood yet. We provide a comprehensive ab initio study of the interfacial properties of a series of monolayer (ML) and bilayer (BL) MoS2-metal contacts (metal?=?Sc, Ti, Ag, Pt, Ni, and Au). A comparison between the calculated and observed Schottky barrier heights (SBHs) suggests that many-electron effects are strongly suppressed in channel 2D MoS2 due to a charge transfer. The extensively adopted energy band calculation scheme fails to reproduce the observed SBHs in 2D MoS2-Sc interface. By contrast, an ab initio quantum transport device simulation better reproduces the observed SBH in 2D MoS2-Sc interface and highlights the importance of a higher level theoretical approach beyond the energy band calculation in the interface study. BL MoS2-metal contacts generally have a reduced SBH than ML MoS2-metal contacts due to the interlayer coupling and thus have a higher electron injection efficiency.

| S-EPMC4772071 | biostudies-literature