Low Carrier Mobility Research Articles

Insight into Magnesium Doping on Morphology, Optical, and Electrical Properties of Cu2O Layer Synthesized by Electrodeposition Method

Cu2O stands out as a promising semiconductor material for solar energy conversion, primarily due to its exceptional light-absorbing qualities and its widespread availability. However, its efficiency is somewhat hindered by its relatively low carrier mobility and a limited absorption band for carriers. The introduction of magnesium (Mg) doping into Cu2O has emerged as a potential means to enhance its morphology, optical characteristics, and electrical properties, making it an intriguing avenue for exploration. To fabricate the Mg-doped Cu2O layers, an electrodeposition process was employed on an Indium Tin Oxide (ITO) substrate. The resulting films were then subjected to characterization using Field Emission Scanning Electron Microscopy (FESEM), Ultraviolet-Visible Spectroscopy (UV-Vis), and HALL Effect Measurement, focusing on their morphology, optical properties, and electrical behaviors. Notably, the concentration of magnesium played a significant role in shaping the properties of the Cu2O layer. The fabrication process extended up to a dopant concentration of 0.3 M for both undoped Cu2O and Mg-doped Cu2O layers, leading to morphological alterations. Specifically, the grain size increased with varying dopant concentrations, but it became smaller and more compact after doping with 0.3 M Mg. The average absorbance of visible light for both undoped and Mg-doped Cu2O layers fell within the range of 1~2 au. Intriguingly, a doping level of 0.3 M Mg led to the simultaneous achievement of high carrier mobility (29.98 cm2/Vs), low bulk carrier concentration (2.3.928 x 1021 cm-3), and high resistivity (5.3 x 10-5 Ω cm) in the Cu2O material. Additionally, Cu2O/ITO thin films exhibiting rectifying characteristics were successfully fabricated, confirming the semiconductor nature of the deposited p-type Cu2O layer. The primary objective of this study was to synthesize Cu2O layers doped with varying concentrations of Mg and thoroughly characterize their morphology, optical attributes, and electrical behaviors through the electrodeposition method. The study findings and implications were extensively discussed.

Enhanced Carrier Mobility and Thermoelectric Performance by Nanostructure Engineering of PEDOT Thin Films Fabricated via the OCVD Method Using SbCl5 Oxidant

AbstractAir‐stable, lightweight, and electrically conductive conjugated polymers have attracted significant attention for thermoelectric applications, especially in low‐temperature environments. However, their low carrier mobility has limited broader adoption. This study addresses this challenge by investigating the nanostructure of poly(3,4‐ethylenedioxythiophene) (PEDOT) thin films fabricated via oxidative chemical vapor deposition (oCVD) at various deposition temperatures. Through systematic control of the semi‐crystalline orientation and π–π stacking distance, a substantial enhancement in carrier mobility (23.58 ± 1.71 cm2 V−1 s−1) and electrical conductivity (6345 ± 210 S cm−1) is achieved. The thermoelectric power factor demonstrates a direct correlation with deposition temperature, achieving a maximum value of 112.57 ± 4.33 µW m−1 K−2. PEDOT thin films fabricated at higher deposition temperatures show minimal reductions in electrical conductivity as absolute temperature decreased, reflecting a lower resistivity ratio and extended metallic state, as indicated by the metal–insulator transition in the Zabrodskii plot. Incorporating the Seebeck coefficient into the parabolic energy band diagram revealed strong agreement between theoretical and experimental carrier mobility, while also indicating that the energy barrier for intercrystalline charge transport decreases as deposition temperature increases. The highly face‐on orientation and reduced π–π stacking distance in PEDOT thin films facilitate quasi‐1D conduction, thereby enhancing carrier mobility.

Solvent-modified carbon nitride integrated with SiO2 for enhanced photocatalytic activity: Microstructural modification and catalytic mechanisms

The photocatalytic activity of carbon nitride (CN) materials is primarily limited by low photogenerated carrier separation and mobility. The solvothermal method can regulate the molecular structure of materials to enhance charge separation and transport. In this study, we used ethanol (EtOH), DMF, and deionized water (H2O) as solvents to customize the microstructure of CN through a one-step solvothermal method and loaded SiO2 onto CN, ultimately synthesizing SiO2/CN composites (SiCNX, where X = E, D, H) with significantly improved photocatalytic efficiency. The modification with these three solvents led to noticeable changes in the basic structure of CN, reflected in the number of carbon vacancies, the integrity of the tri-s-triazine ring framework, the degree of polymerization, and the presence of C–C/CC bonds. The SiCNE composite, synthesized with ethanol modification, stood out by demonstrating exceptional photocatalytic degradation ability for Rhodamine B (RhB), achieving 99 % decolorization of a high-concentration RhB solution (300 mg/L) in 35 min. Additionally, the performance of SiCNE is 6.24 times that of CN and 224 times that of SiO2. This study not only exhibits the potential of solvent-modified SiCNX in constructing efficient electron transfer pathways but also highlights its capability in remarkably improving photocatalytic performance, providing a promising avenue for the development of future photocatalytic materials.

A-Site Engineering with Thiophene-Based Ammonium for High-Efficiency 2D/3D Tin Halide Perovskite Solar Cells.

Tin halide perovskites are the most promising candidate materials for lead-free perovskite solar cells (PSCs) thanks to their low toxicity and ideal band gap energies. The introduction of 2D/3D mixed perovskite phases in tin-based PSCs (TPSCs) has proven to be the most effective approach to improving device efficiency and stability. However, a 2D perovskite phase normally shows relatively low carrier mobility, which will be unfavorable for carrier transfer in the devices. In this work, we used a thiophene-based cation 2-(thiophen-3-yl)ethan-1-aminium (3-TEA) as a spacer to form a novel 2D perovskite phase in TPSCs, which shows the most promising effect on the performance enhancement in comparison with other cations like 2-(thiophen-2-yl)ethan-1-aminium (2-TEA) and benzene-based 2-phenylethan-1-aminium (PEA). Theoretical calculations reveal that 3-TEA enables the most compact crystal packing of [SnI6]4- octahedral layers, resulting in the lowest hole effective mass and formation energy in the 2D phase. This effect significantly enhances device efficiency and stability by facilitating more efficient carrier transfer within the 2D phase. These findings indicate that thiophene-based 2D perovskites are well-suited for high-performance TPSCs.

A‐Site Engineering with Thiophene‐Based Ammonium for High‐Efficiency 2D/3D Tin Halide Perovskite Solar Cells

AbstractTin halide perovskites are the most promising candidate materials for lead‐free perovskite solar cells (PSCs) thanks to their low toxicity and ideal band gap energies. The introduction of 2D/3D mixed perovskite phases in tin‐based PSCs (TPSCs) has proven to be the most effective approach to improving device efficiency and stability. However, a 2D perovskite phase normally shows relatively low carrier mobility, which will be unfavorable for carrier transfer in the devices. In this work, we used a thiophene‐based cation 2‐(thiophen‐3‐yl)ethan‐1‐aminium (3‐TEA) as a spacer to form a novel 2D perovskite phase in TPSCs, which shows the most promising effect on the performance enhancement in comparison with other cations like 2‐(thiophen‐2‐yl)ethan‐1‐aminium (2‐TEA) and benzene‐based 2‐phenylethan‐1‐aminium (PEA). Theoretical calculations reveal that 3‐TEA enables the most compact crystal packing of [SnI6]4− octahedral layers, resulting in the lowest hole effective mass and formation energy in the 2D phase. This effect significantly enhances device efficiency and stability by facilitating more efficient carrier transfer within the 2D phase. These findings indicate that thiophene‐based 2D perovskites are well‐suited for high‐performance TPSCs.

Synergistic effect of FeOOH cocatalyst and Al2O3 passivation layer on BiVO4 photoanode for enhanced photoelectrochemical water oxidation

BiVO4 is one of the most attractive photoanodes for water oxidation due to its 2.4 eV narrow band gap, suitable band edge position, good stability in aqueous solution, low cost and non-toxicity. However, due to some inherent disadvantages such as low carrier mobility, severe charge recombination and slow water oxidation kinetics, the actual BiVO4 photocurrent density is often lower than the theoretical value of 7.5 mA cm−2. In this paper, BiVO4 was modified by alkali-treated Al2O3 passivation layer and FeOOH, and the photocurrent density of BiVO4 reached an astonishing 3.8 mA cm−2 at 1.23 VRHE, and the ABPE (applied bias photon-to-current efficiency) was close to 1 %. The detailed structural characterization and electrochemical test show that Al2O3 prepared by ALD (atomic layer deposition) can play a role in passivation of BiVO4 surface state after alkali treatment, inhibit electron hole recombination on BiVO4 surface, and accelerate hole transfer. As a hole storage layer and catalyst layer, FeOOH promoted the interfacial hole transfer, increased the active sites at the electrode electrolyte interface, and significantly increased the water oxidation activity. This work provides a novel method to enhance the performance of water electrolysis by using ALD to assist passivation of bismuth vanadate photoanode surface states.

Enhanced water splitting on (010) facet-exposed BiVO4 photoanode with improved carrier injection efficiency

Transition metal oxide semiconductors, noted for their stability and suitable bandgap, are promising photoanodes for water splitting. Surface engineering is critical to tackle issues like low carrier mobility and charge recombination, stemming from atomic arrangement and Fermi level differences. While exposing dominant crystal facets boosts photocatalytic capability, it can hinder carrier injection into the electrolyte. In this study, BiVO4 films with various facet exposures were synthesized and characterized using scanning electron microscopy and x-ray diffraction to confirm their morphology and crystalline structure. Mott–Schottky analysis was employed to investigate changes in the band structure near the semiconductor–electrolyte interface, revealing that high (010)-BiVO4 facet exposure enhances carrier separation but reduces injection efficiency. The results from photoconductive atomic force microscopy tests demonstrated that enhanced band bending at the semiconductor interface improves hole transfer. Coating the (010)-BiVO4 photoanode with MoS2 and an amorphous ZrO2 interlayer yielded a photocurrent density of 0.6 mA cm−2 at 1.2 V (vs RHE) under AM 1.5 G illumination, tripling the pristine photoanode's performance and nearly tripling water splitting efficiency. Mechanism revealing the improved photoelectrochemical performance is attributed to a greater band bending on the BiVO4 surface, enhancing hole injection dynamics. This work provides a feasible strategy for a deeper understanding of the intrinsic mechanisms of facet engineering and improving the activity of photoanodes.

As‐Doped Polycrystalline CdSeTe: Localized Defects, Carrier Mobility and Lifetimes, and Impact on High‐Efficiency Solar Cells

AbstractThe efficiency potential for single‐junction photovoltaics (PV) is described by the detailed balance model, which requires the elimination of nonradiative recombination and perfect minority carrier collection. Improvements in GaAs, Si, and perovskite PV follow this model. It might be more complex for CdTe, a leading thin‐film PV technology. While lifetime, passivation, and doping goals for 25% efficient CdTe solar cells are largely reached, voltage is ≈20% below the detailed balance limit. Why is that? In Se‐alloyed CdSexTe1‐x (Se is required for >20% efficiency) additional losses can occur due to electrostatic and bandgap fluctuations and due to electronic trap states. To understand mechanisms limiting CdSeTe solar cell performance and to suggest improvements, carrier dynamics, and transport in CdSexTe1‐x with variation in Se composition and as doping is analyzed. It is shown that trapping, likely due to anion‐site defects and their complexes, is correlated with low charge carrier mobility of 0.1–0.6 cm2 (Vs)−1. Even with 1000 ns charge carrier lifetimes, carrier diffusion length is less than the absorber thickness, reducing efficiency to ≈23%. Device simulations are used to analyze the performance of CdSexTe1‐x solar cells; thermodynamic models are not sufficient for absorbers with electronic disorder and trapping.

Electrical properties of completely compensated single-crystal Ge-on-GaAs films with two-dimension Coulomb disorder

We present electrical properties of heavily doped and completely compensated Ge films grown on semiinsulating GaAs(100) substrates by vacuum evaporation. The thin (∼100 nm) Ge films are single-crystal and characterized using temperature-dependent transport measurements, with anomalously large activation energy up to half the Ge bandgap, anisotropy of the transverse magnetoresistance, high resistivity (up to 140 Ω cm), low free charge carrier mobility (∼50 cm2/V·s), and concentration (∼1014–1015 cm−3). This behaviour is attributed to a completely compensated semiconductors arising from Ga and As impurity incorporation and large-scale potential fluctuations. Analysis suggests a two-dimensional percolative transport mechanism in Ge-on-GaAs heterostructures.

(Ag–NiO)/g-C3N4 with enhanced photocatalytic activity for hydrogen evolution under simulated sunlight

g-C3N4 is a promising metal-free photocatalyst for hydrogen production, whose application is difficult due to the low mobility of charge carriers and rapid electron-hole recombination. Here we propose a new route to improve its response to simulated sunlight and prevent electron-hole recombination by grafting mixed Ag–NiO (1:1 nominal Ag/NiO weight ratio) materials, as an alternative to platinum group metal co-catalysts. g-C3N4 was prepared by urea pyrolysis, whereas Ag–NiO was prepared by a co-precipitation method, and then the composites were prepared by physical mixing using sonication-grinding. The presence of Ag–NiO on the surface plays a key role in accepting excited electrons and enhancing their lifetime for a subsequent reduction of protons to hydrogen. Hydrogen production was carried out from the photoreforming of ethanol under simulated sunlight. The results revealed that 2% (Ag–NiO)/g-C3N4 is effective among others with 5.2 times higher H2 production than unmodified g-C3N4. The percentage of ethanol in the ethanol/water ratio is very important as we have found that with increasing its quantity, the evolution of hydrogen becomes significant.

1,5‐Diazocine‐Based Diaryl Ketones: Design, Synthesis, and Optoelectronic Properties

ABSTRACTThree novel heterocyclic host based on diaryl ketone‐tethered 1,5‐diazocines were designed and synthesized for applications in phosphorescent organic light‐emitting diodes (PhOLEDs). The hosts were derived by anchoring the naphthyl ketone (TBN), anthryl ketone (TBA), and phenanthryl ketone (TBP) to the 1,5‐diazocine core. The materials were successfully characterized using spectroscopic techniques. TBN and TBP exhibited low external quantum efficiency of 1.5% and 1.9% when explored as hosts in PhOLED devices. Among the series, TBP exhibited the highest luminance of 4160 cd/m2, maximum luminance efficiency of 6.3 cd/A, and power efficiency of 3.21 lm/w, when doped with Ir(ppy)3 in PhOLED. Nevertheless to our surprise, TBA manifested the lowest device performance than other TBs as a host due to low carrier mobility caused by a highly twisted structure as deciphered from the comparative analysis of single‐crystal structure that could impede carrier transport crucial for efficient electroluminescence. The outcomes of electroluminescence were validated and explained with analysis of single‐crystal structure, and also with the aid of density functional theory.

First-principles prediction of high carrier mobility for β-phase MX2N4 (M = Mo, W; X = Si, Ge) monolayers

The recently synthesized monolayer MoSi2N4 (Science 2020, 369, 367) exhibits exceptional environmental stability, a moderate band gap, and excellent mechanical properties, presenting exciting opportunities for the exploration of two-dimensional (2D) MX2Z4 materials. However, the low carrier mobility of α-phase MoSi2N4 significantly limits its potential applications in field-effect transistor (FET) devices. In this study, we systematically investigate the structural stability, elastic properties, and carrier mobility of a novel family of β-phase MX2N4 (M = Mo, W; X = Si, Ge) monolayers through first-principles calculations. Our findings reveal that these β-phase MX2N4 monolayers demonstrate remarkable dynamic, thermal, and mechanical stability. Specifically, we identify the MoSi2N4, MoGe2N4, WSi2N4, and WGe2N4 monolayers as semiconductors with band gaps of 2.70 eV, 1.57 eV, 3.12 eV, and 1.93 eV, respectively, as calculated using the HSE06 functional. Moreover, the MX2N4 monolayers exhibit significant elastic anisotropy, characterized by high ideal tensile strengths and a critical tensile strain exceeding 25%. Notably, the WGe2N4 monolayer displays exceptional anisotropic in-plane charge transport, achieving mobility levels of up to 104 cm2V− 1S− 1, surpassing those of the α-phase MX2N4 monolayers. These novel ternary monolayer structures have the potential to broaden the 2D MX2Z4 material family and emerge as promising candidates for applications in field-effect transistors.

CuBi2O4/CuO photocathode with conformal CQD@Ni(OH)2 coating for stable solar water splitting

CuBi2O4 exhibits a high onset potential and theoretically high photocurrent density due to its well-matched bandgap for solar water splitting. However, factors such as low charge carrier mobility and severe charge recombination prevent CuBi2O4 from reaching its ideal photoelectrochemical performance, while photocorrosion of the Cu element severely compromises its stability. Herein, a convenient and low-cost chemical bath deposition method has been employed to combine carbon quantum dots (CQDs) with Ni(OH)2, resulting in the preparation of a conformal CQD@Ni(OH)2 layer-coated CuBi₂O₄/CuO heterojunction photocathode. Under AM 1.5G illumination, CuBi2O4/CuO/CQD@Ni(OH)2 illustrates a photocurrent density of −1.36 mA cm−2, which is 2.12 times higher than that of CuBi2O4/CuO. More importantly, the conformal coating of CQD@Ni(OH)2 effectively prevents photocorrosion induced by oxidation-reduction reactions of Cu2+/Cu. At 0.3 VRHE, the photocurrent of CuBi2O4/CuO/CQD@Ni(OH)2 remains at 76.4% after 10000 s of chopped light illumination, significantly outperforming the 48.9% retention observed for CuBi2O4/CuO photocathode after 3600 s of chopped light illumination. This work demonstrates that the CQDs and Ni(OH)2 are good candidates for the photoelectrode overlayer with significant synergetic effects.

High response MSM UV photodetectors based on MgZnO/MnS heterojunction

Ultraviolet (UV) photodetectors (PDs) are favored for their wide range of applications. In this work, MgZnO/MnS composite films were prepared on quartz glass by sol-gel and successive ionic layer adsorption and reaction (SILAR) methods for UV photodetection. Compared with MgZnO device, the MgZnO/MnS device overcomes the drawbacks of lower carrier mobility and more traps in the original MgZnO photosensitive layer, and has ultrahigh responsivity and detectivity (4564.5 A/W, 1.7 × 1016 Jones), high photocurrent (up to 1.8 × 10−3 A), lower dark current (down to 8.8 × 10- 10 A) and high light-dark ratio (up to about 8 × 105), which is attributed to the formation of a p-n junction by the contact between MgZnO and MnS, resulting in the establishment of an internal electric field to serve as a depletion layer. The built-in electric field consumes most of the carriers so that the device exhibits a low conductivity, and MnS fills up some of the defects on the surface of the MgZnO, which results in a low dark current. Under UV radiation, photogenerated carriers are separated by built-in electric field, leading the recombination of electron-hole pairs decrease. This causes the device show high conductivity and generate high photocurrent. These results make MgZnO/MnS PDs promising for applications in device requiring high responsivity.

Novel Self-Assembling Supramolecular Phenanthro[9,10-a]phenazine Discotic Liquid Crystals: Synthesis, Characterization and Charge Transport Studies.

The incorporation of heteroatoms in the chemical structure of organic molecules has been identified as analogous to the doping process adopted in silicon semiconductors to influence the nature of charge carriers. This strategy has been an eye-opener for material chemists in synthesizing new materials for optoelectronic applications. Phenanthro[9,10-a]phenazine-based mesogens have been synthesized via a cyclo-condensation pathway involving triphenylene-based diketone and o-phenyl diamines. The incorporation of phenazine moiety as discussed in this paper, alters the symmetric nature of the triphenylene. The phenanthro[9,10-a]phenazine-based mesogens exhibit hole mobility in the order of 10-4 cm2/Vs as measured by the space-charge limited current (SCLC) technique. The current density in the SCLC device increases with increasing temperature which indicates that the charge transport is associated with the thermally activated hopping process. This report attempts to elucidate the self-organization of asymmetric phenanthro[9,10-a] phenazine in the supramolecular liquid crystalline state and their potential for the fabrication of high-temperature optoelectronic devices. However, the low charge carrier mobility can be one of the challenges for device performance.

Hybrid System of Polystyrene and Semiconductor for Organic Electronic Applications

While organic semiconductors hold significant promise for the development of flexible, lightweight electronic devices such as organic thin-film transistors (OTFTs), photodetectors, and gas sensors, their widespread application is often limited by intrinsic challenges. In this article, we first review these challenges in organic electronics, including low charge carrier mobility, susceptibility to environmental degradation, difficulties in achieving uniform film morphology and crystallinity, as well as issues related to poor interface quality, scalability, and reproducibility that further hinder their commercial viability. Next, we focus on reviewing the hybrid system comprising an organic semiconductor and polystyrene (PS) to address these challenges. By examining the interactions of PS as a polymer additive with several benchmark semiconductors such as pentacene, rubrene, 6,13-bis(triisopropylsilylethynyl) pentacene (TIPS pentacene), 2,8-difluoro-5,11-bis(triethylsilylethynyl) anthradithiophene (diF-TES-ADT), and 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene (C8-BTBT), we showcase the versatility of PS in enhancing the crystallization, thin film morphology, phase segregation, and electrical performance of organic semiconductor devices. This review aims to highlight the potential of an organic semiconductor/PS hybrid system to overcome key challenges in organic electronics, thereby paving the way for the broader adoption of organic semiconductors in next-generation electronic devices.

In Situ Photoelectrochemical‐Induced Surface Reconstruction of BiVO4 Photoanodes for Solar Fuel Production

BiVO4 has been widely concerned due to its great potential in photoelectrochemical (PEC) water splitting. However, low carrier mobilities and high recombination efficiency of photogenerated carriers impede its photocatalytic performance. Herein, an in situ PEC cyclic‐voltammetry‐induced surface reconstruction of BiVO4 photoanodes (BVO pristine) is developed with significantly enhanced efficiency for solar water splitting. A series of in situ characterizations (including in situ X‐ray diffraction, in situ Raman), together with electrochemical tests and density‐functional theory calculations, reveal that during the photoelectrical activation process, the BVO pristine surfaces undergo a crystal plane reconstruction with greatly increased {040} crystal face to promote the separation of photogenerated carriers. In addition, abundant vanadium vacancies and oxygen vacancies are also introduced into the BiVO4 surface during the crystal face reconstruction process with more favorable surface water adsorption and increased injection efficiency of photogenerated carriers. Therefore, the charge‐transfer resistance (Rct) between BVO pristine and electrolyte under AM 1.5G illumination substantially reduced from the original 15 200 to 2820 Ω after the activation. Moreover, the photocurrent density of activated BVO pristines increases more than 12 times, relative to the original BiVO4. In this work, a new horizon for in situ photoelectric activation of semiconductor photoelectrodes with significantly enhanced PEC water splitting is provided.

Opto-electrical study of 4T perovskite-chalcogenide tandem solar cell with the addition of quasi-2D perovskite as capping layer of 3D perovskite layer

This study presents a four-terminal (4T) perovskite-chalcogenide tandem solar cell (TSC) that includes quasi-2D perovskite material in the top sub-cell in order to provide a stable structure, and the bottom sub-cell contains Zn(O,S,OH) material to provide a nontoxic buffer layer. First, a reference TSC with a total power conversion efficiency (PCE) of 26.48% is modeled, using MAPbI3 and CIGSSe as 3D perovskite and chalcogenide absorber layers (ALs), respectively. Next, two structures are designed to produce a stable SC using the Ruddlesden Popper (RP) quasi-2D perovskite materials, which have the chemical formula BA2MAm−1PbmI3m+1, m = 2–5. The initial structure uses quasi-2D perovskites in place of the 3D perovskite AL. According to the results, BA2MAPb2I7 represents the maximum PCE of 16.00%, 10.48% less than previously. This is caused by quasi-2D materials’ high Eg and low carrier mobility. In the second structure, 3D perovskite AL is capped with the quasi-2D perovskites. In terms of attaining maximum PCE, the optimal TSC is found for BA2MA3Pb4I13 with a PCE of 25.80%. Compared to the initial structure, this one’s PCE increased by 61.25%. In order to boost PCE, a 80 nm-thick anti-reflection (AR) layer is added to the second structure, and the PCE increased to 27.48%. Therefore, the final TSC is proposed as a 4T quasi-2D/3D perovskite-chalcogenide TSC that is stable, and has nontoxic buffer layer, with 3.78% more PCE than the reference structure.

Deterministic grayscale nanotopography to engineer mobilities in strained MoS2 FETs

Field-effect transistors (FETs) based on two-dimensional materials (2DMs) with atomically thin channels have emerged as a promising platform for beyond-silicon electronics. However, low carrier mobility in 2DM transistors driven by phonon scattering remains a critical challenge. To address this issue, we propose the controlled introduction of localized tensile strain as an effective means to inhibit electron-phonon scattering in 2DM. Strain is achieved by conformally adhering the 2DM via van der Waals forces to a dielectric layer previously nanoengineered with a gray-tone topography. Our results show that monolayer MoS2 FETs under tensile strain achieve an 8-fold increase in on-state current, reaching mobilities of 185 cm²/Vs at room temperature, in good agreement with theoretical calculations. The present work on nanotopographic grayscale surface engineering and the use of high-quality dielectric materials has the potential to find application in the nanofabrication of photonic and nanoelectronic devices.

Broadband terahertz modulation in symmetric gate-controlled graphene photonic crystals

Innovative research in terahertz (THz) communications is urgently needed to meet the evolving demands of the industry. In the past, the absence of optoelectronic devices made it difficult to control THz waves effectively. In this study, a symmetric gate-controlled graphene photonic crystal (PC) is proposed, which achieves a modulation depth (MD) of more than 99 %, an ultralow insertion loss (IL) of 0.08, and a wide operation bandwidth (BW) simultaneously. Additionally, even in graphene samples with low carrier mobilities, the high-performance MD can be achieved with acceptable IL in the broadband THz range. Furthermore, our proposed one-dimensional graphene PC system enhances manufacturing convenience. Through the adoption of the proposed symmetric structure, highly efficient THz communications can be achieved through photonic systems that utilize graphene.