Abstract MBenes are a relatively new family of two-dimensional (2D) transition metal borides that can be synthesized through selective etching of A-layers from MAB phases. As in MXenes, surface termination is a key factor influencing their properties. Inspired by the recent discovery of Ti 2 B 2 T x MBene, this Density Functional Theory (DFT) study investigates halogen-terminated Ti 2 B 2 T x compounds (T x = Cl, Br, and I) with coverages ranging from 100% (ideal, x = 2) to 50% (x = 1), for which the unoccupied sites are either treated as vacancies or filled with oxygen atoms. Our main findings reveal that oxygen incorporation is favorable for all halogen terminations, and the interlayer binding energies of the multilayer-Ti 2 B 2 T x MBenes are comparable to those of other vdW 2D materials. Further, the MBenes exhibit good mechanical properties and low interlayer sliding energy barriers, suggesting suitability for tribological applications. The effect of the surface termination on the electronic structures and adsorption energies was also investigated for fundamental insights. Finally, the calculated work function ranges from ~3 to 5 eV, indicating that it can be tuned with precise control over termination coverage and composition, offering a powerful route to tailoring MBene properties for improved application-specific performance.
High-harmonic generation is a sensitive all-optical probe of symmetry and electron dynamics in solids. Here, we use first-principles time-dependent density functional theory (TDDFT) to study high-harmonic generation in Td-WTe2, a two-dimensional semimetal with switchable out-of-plane ferroelectric polarization driven by interlayer sliding. We show that the mirror-symmetry breaking underlying the ferroelectric state produces robust signatures in polarization- and phase-resolved high-harmonic spectra, enabling optical identification of the polarization state. By incorporating interlayer shear motion in coupled electron-lattice TDDFT simulations, we further show that the 0.24 THz shear mode is slow enough to remain effectively decoupled from the ultrafast electronic response responsible for harmonic emission. Our results establish high-harmonic spectroscopy as a non-invasive probe of sliding ferroelectricity and lattice symmetry in two-dimensional quantum materials.
Different variable charges such as interface traps, oxide border traps, and mobile carriers can contribute to the total capacitance in metal oxide semiconductor (MOS) field-effect devices. This study aims to quantify these charge components using multi-frequency, multi-temperature capacitance–voltage/conductance–voltage (C–V/G–V) scans with interface trap density profile mapping combined with Hall measurements on fully depleted few-layer transition metal dichalcogenides (MX2)-based MOS devices. In addition, C–V/G–V simulations based on a distributed network MOS model for two-dimensional (2D) materials have been incorporated to verify the interface trap charge component. The results of this study reveal that mobile carriers dominate the total carrier population, accounting for 58%–74%, while interface trap charges contribute an additional 18%–29% of the total charge. In contrast, oxide border traps constitute 7%–12% of the overall charges. This method for the quantification of the different charge components provides fundamental information for the design and optimization of emerging MX2-based devices.
Graphene intrinsic carrier ambipolarity enables unique circuit functionalities that would otherwise require significantly more complex circuit topologies to achieve with conventional semiconductors. Yet, translating these properties into practical, wafer-scale electronic systems remains a significant challenge. Here, we present an experimental proof of concept of a reconfigurable frequency multiplier based on a single split-gate graphene field-effect transistor. The devices used for this demonstration were externally fabricated through a multi-project wafer tape-out of the 2D Experimental Pilot Line, an initiative aimed at providing a scalable platform service for the manufacturing of 2D-material-based devices and circuits. The split-gate architecture synthesizes a W-shaped transfer characteristic within a single device enabling electrically reconfigurable frequency multiplication by factors of × 2, × 3, and × 4 without requiring multiple transistors or fixed fabrication-dependent tuning mechanisms. Time-domain measurements and spectral analysis confirm harmonic reconfiguration, yielding spectral purities of 48% for the doubler, 69% for the tripler, and 19% for the quadrupler at an input frequency of 100 kHz. This constitutes the first demonstration of a reconfigurable circuit using devices from the multi-project wafer 2D-EPL platform, representing a step forward in the integration complexity achievable with wafer-scale graphene technology.
Graphene oxide (GO) is a class of chemically derived graphene materials widely used in diverse fields, ranging from electronics to environmental applications. Yet, its detailed structure remains an open question due to the effect of the different synthesis methods on the oxidation level. In this work, we compare our synchrotron radiation based soft X-ray spectroscopy and density functional theory (DFT) calculations to elucidate the relevance of functional groups on the structure and electronic properties of GO, synthesized by modified Hummers’ method. We demonstrate that the position of the hydroxyl groups strongly modulates the structure and local bonding environment. Our results indicate that it is energetically preferable to attach functional groups to only one side of the GO layer, which leads to a largely intact carbon network with 60% C-C regions. We observe that the presence of hydroxyl groups induces charge distortions while epoxide groups weaken the adjacent carbon bonds. Furthermore, our two-dimensional electron density map illustrates the detailed electron localization in various carbon sites within GO. This provides information on the interaction of functional groups, which is essential in order to tailor GO with specific properties for applications in energy storage, sensing, and next-generation electronic devices.
