npj 2D Materials and Applications

Journal: npj 2D Materials and Applications

Abbreviation

npj 2D Mater Appl

Publisher

Nature

ISSN

2397-7132

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Publications 1 - 10 of 11

Disorder-induced bulk photovoltaic effect in a centrosymmetric van der Waals material
Cheon, Cheol-Yeon; Sun, Zhe; Cao, Jiang; et al. (2023)
npj 2D Materials and Applications
Sunlight is widely seen as one of the most abundant forms of renewable energy, with photovoltaic cells based on pn junctions being the most commonly used platform attempting to harness it. Unlike in conventional photovoltaic cells, the bulk photovoltaic effect (BPVE) allows for the generation of photocurrent and photovoltage in a single material without the need to engineer a pn junction and create a built-in electric field, thus offering a solution that can potentially exceed the Shockley–Queisser efficiency limit. However, it requires a material with no inversion symmetry and is therefore absent in centrosymmetric materials. Here, we demonstrate that breaking the inversion symmetry by structural disorder can induce BPVE in ultrathin PtSe2, a centrosymmetric semiconducting van der Waals material. Homogenous illumination of defective PtSe2 by linearly and circularly polarized light results in a photoresponse termed as linear photogalvanic effect (LPGE) and circular photogalvanic effect (CPGE), which is mostly absent in the pristine crystal. First-principles calculations reveal that LPGE originates from Se vacancies that act as asymmetric scattering centers for the photo-generated electron-hole pairs. Our work emphasizes the importance of defects to induce photovoltaic functionality in centrosymmetric materials and shows how the range of materials suitable for light sensing and energy-harvesting applications can be extended.
Noise diagnostics of graphene interconnects for atomic-scale electronics
Pósa, László; Balogh, Zoltán; Krisztián, Dávid; et al. (2021)
npj 2D Materials and Applications
Graphene nanogaps are considered as essential building blocks of two-dimensional electronic circuits, as they offer the possibility to interconnect a broad range of atomic-scale objects. Here we provide an insight into the microscopic processes taking place during the formation of graphene nanogaps through the detailed analysis of their low-frequency noise properties. Following the evolution of the noise level, we identify the fundamentally different regimes throughout the nanogap formation. By modeling the resistance and bias dependence of the noise, we resolve the major noise-generating processes: atomic-scale junction-width fluctuations in the nanojunction regime and sub-atomic gap-size fluctuations in the nanogap regime. As a milestone toward graphene-based atomic electronics, our results facilitate the automation of an optimized electrical breakdown protocol for high yield graphene nanogap fabrication.
Mobility calculation in disordered WS₂-Al₂O₃ stacks from first principles
Dossena, Mauro; Van Troeye, Benoit; Ducry, Fabian; et al. (2025)
npj 2D Materials and Applications
Transition metal dichalcogenides (TMDCs) are promising candidates for future nano-transistor channels due to their outstanding intrinsic transport properties. However, their electron mobility is highly sensitive to the surrounding dielectric, often falling well below theoretical expectations. In this work, we explore how a stacked Al₂O₃ dielectric affects electron mobility in monolayer WS₂ using first-principles quantum transport simulations. We identify that fluctuations in the electrostatic potential, arising from the disordered structure of Al₂O₃, significantly degrade mobility, especially when WS₂ interfaces with under-coordinated aluminum atoms. Our calculated mobilities (≃1–30 cm²/(V ⋅ s)) align with experimental observations and remain far from the ideal limit (≃300 cm²/(V ⋅ s)). We further demonstrate that encapsulating WS₂ with hexagonal boron nitride (hBN) or employing a crystalline oxide can recover high mobility values. However, these strategies introduce trade-offs in electrostatic control and fabrication complexity, underlining the need for careful dielectric engineering in TMDC-based devices.
Seamless in two dimensions: prospects of lateral heterostructures from integration to quantum devices
Chakraborty , Suman Kumar; Nayak , Biswajeet; Kundu , Baisali; et al. (2025)
npj 2D Materials and Applications
Lateral heterostructures of two-dimensional (2D) transition metal dichalcogenides feature atomically sharp, covalently stitched 1D interfaces that enable direct band-to-band coupling. This perspective highlights their unique ability to control quasiparticles, excitons, and spins, with implications for optoelectronics, excitonic and valleytronic devices, tunneling field-effect transistors, neuromorphic computing, spintronics, and quantum circuits. It also outlines challenges in scalable synthesis, interface engineering, and 2D–3D integration, charting paths toward future quantum technologies.
Spatially mapping thermal transport in graphene by an opto-thermal method
Braun, Oliver; Furrer, Roman; Butti, Pascal; et al. (2022)
npj 2D Materials and Applications
Mapping the thermal transport properties of materials at the nanoscale is of critical importance for optimizing heat conduction in nanoscale devices. Several methods to determine the thermal conductivity of materials have been developed, most of them yielding an average value across the sample, thereby disregarding the role of local variations. Here, we present a method for the spatially resolved assessment of the thermal conductivity of suspended graphene by using a combination of confocal Raman thermometry and a finite-element calculations-based fitting procedure. We demonstrate the working principle of our method by extracting the two-dimensional thermal conductivity map of one pristine suspended single-layer graphene sheet and one irradiated using helium ions. Our method paves the way for spatially resolving the thermal conductivity of other types of layered materials. This is particularly relevant for the design and engineering of nanoscale thermal circuits (e.g. thermal diodes).
An ab initio study on resistance switching in hexagonal boron nitride
Ducry, Fabian; Waldhoer, Dominic; Knobloch, Theresia; et al. (2022)
npj 2D Materials and Applications
Two-dimensional materials have been widely investigated to implement memristive devices for data storage or neuromorphic computing applications because of their ultra-scaled thicknesses and clean interfaces. For example, resistance switching in hexagonal boron nitride (h-BN) has been demonstrated. This mechanism is most of the time attributed to the movement of metallic ions. It has however also been reported when h-BN is contacted with two inert electrodes such as graphene or Pt. We suggest here that the switching mechanism of the latter devices, which has not yet been clearly established, relies on locals change of the electronic structure of h-BN as caused by atomic defects, e.g., multi-vacancies. This class of intrinsic h-BN defects can create electrically controllable interlayer bridges. We use a combination of hybrid density functional theory and the Non-equilibrium Green's function formalism to show that a single interlayer bridge resulting from the presence of a trivacancy in a graphene/h-BN/graphene stack leads to a switching voltage of similar to 5 V and a high-to-low resistance ratio >100. Both values lie within the reported experimental range and thus confirm the likelihood that intrinsic defects play a key role in the resistance switching of h-BN in contact with inert electrodes.
Strong modulation of carrier effective mass in WTe2 via coherent lattice manipulation
Soranzio, Davide; Savoini, Matteo; Beaud, Paul; et al. (2022)
npj 2D Materials and Applications
The layered transition-metal dichalcogenide WTe2 is characterized by distinctive transport and topological properties. These properties are largely determined by electronic states close to the Fermi level, specifically to electron and hole pockets in the Fermi sea. In principle, these states can be manipulated by changes to the crystal structure. The precise impact of particular structural changes on the electronic properties is a strong function of the specific nature of the atomic displacements. Here, we report on time-resolved X-ray diffraction and infrared reflectivity measurements of the coherent structural dynamics in WTe2 induced by femtosecond laser pulses excitation (central wavelength 800 nm), with emphasis on a quantitative description of both in-plane and out-of-plane vibrational modes. We estimate the magnitude of these motions, and calculate via density functional theory their effect on the electronic structure. Based on these results, we predict that phonons periodically modulate the effective mass of carriers in the electron and hole pockets up to 20%. This work opens up new opportunities for modulating the peculiar transport properties of WTe2 on short time scales.
Ab initio Simulation of Spin-Charge Qubits based on Bilayer Graphene-WSe₂ Quantum Dots
Ge, Huaiyu; Koopmann, Peter; Mrcarica, Filip; et al. (2025)
npj 2D Materials and Applications
We propose a spin-charge qubit based on a bilayer graphene and WSe₂ van der Waals heterostructure that together form a quantum dot and demonstrate its functionality from first-principles simulations. Electron and hole confinement as well as electrically controllable spin-orbit coupling (SOC) are modeled by self-consistently solving the Schrödinger and Poisson equations with material parameters extracted from density functional theory as inputs. In both electron and hole quantum dots, we find a two orders of magnitude enhancement of SOC (1.8 meV) compared to intrinsic graphene, in the layer directly adja- cent to WSe₂. Time-dependent investigations of the quantum device reveal rapid qubit gate operation in the order of picoseconds. Our simulations indicate that bilayer graphene and WSe₂ heterostructures provide a promising platform for the processing of quantum information.
Dissipative Transport and Phonon Scattering Suppression via Valley Engineering in Single-Layer Antimonene and Arsenene Field-Effect Transistors
Cao, Jiang; Wu, Yu; Zhang, Hao; et al. (2021)
npj 2D Materials and Applications
Two-dimensional (2D) semiconductors are promising channel materials for next-generation field-effect transistors (FETs) thanks to their unique mechanical properties and enhanced electrostatic control. However, the performance of these devices can be strongly limited by the scattering processes between carriers and phonons, usually occurring at high rates in 2D materials. Here, we use quantum transport simulations calibrated on first-principle computations to report on dissipative transport in antimonene and arsenene n-type FETs at the scaling limit. We show that the widely-used approximations of either ballistic transport or simple acoustic deformation potential scattering result in large overestimation of the ON current, due to neglecting the dominant intervalley and optical phonon scattering processes. We additionally investigate a recently proposed valley engineering strategy to improve the device performance by removing the valley degeneracy and suppressing most of the intervalley scattering channels via an uniaxial strain along the zigzag direction. The method is applicable to other similar 2D semiconductors characterized by multivalley transport.
Electric field tunable bandgap in twisted double trilayer graphene
Perrin, Mickael L.; Jayaraj, Anooja; Ghawri, Bhaskar; et al. (2024)
npj 2D Materials and Applications
Twisted van der Waals heterostructures have recently emerged as a versatile platform for engineering interaction-driven, topological phenomena with a high degree of control and tunability. Since the initial discovery of correlated phases in twisted bilayer graphene, a wide range of moiré materials have emerged with fascinating electronic properties. While the field of twistronics has rapidly evolved and now includes a range of multi-layered systems, moiré systems comprised of double trilayer graphene remain elusive. Here, we report electrical transport measurements combined with tight-binding calculations in twisted double trilayer graphene (TDTLG). We demonstrate that small-angle TDTLG (~1.7−2.0∘) exhibits an intrinsic bandgap at the charge neutrality point. Moreover, by tuning the displacement field, we observe a continuous insulator-semimetal-insulator transition at the CNP, which is also captured by tight-binding calculations. These results establish TDTLG systems as a highly tunable platform for further exploration of magneto-transport and optoelectronic properties.

Publications 1 - 10 of 11

Journal: npj 2D Materials and Applications

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