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In this paper, we examine the effects of subband quantization on the efficacy of an L-shaped gate vertical dopingless tunneling field-effect transistor. The proposed architecture leverages an intrinsic tunneling interface that is fully aligned with the gate metal, resulting in enhanced electrostatic control. We utilized a two-step numerical simulation approach grounded in the Schrödinger-Poisson equations to evaluate the performance of our proposed device and accurately calculate the ON-state current. Additionally, we assessed the influence of defects at the heterojunction on the performance of our device. Under quantum mechanical assumptions, parameters such as I ON = 23.8 µA/µm, SS AVG = 12.03 mV/dec, and the I ON / I OFF ratio = 4.88 × 10 10 indicate that our structure is a promising candidate for high-performance applications.

Graphene nanoribbons (GNRs) have emerged as promising candidates for nanoelectronic devices due to their unique electronic and transport properties. In this study, we investigate the impact of passivation on cove-edge graphene nanoribbon (CGNR) using both cadmium (Cd) and hydrogen (H) atoms. Through a comprehensive density functional theory (DFT) analysis coupled with non-equilibrium Green’s function (NEGF) simulations, we explore the electronic transport properties and device behavior of these passivated CGNRs. Our results reveal a distinctive semiconductor-to-metal transition in the electronic properties of the Cd-passivated CGNRs. This transition, induced by the interaction between Cd atoms and the GNR edges, leads to a modulation of the bandstructure and a pronounced shift in the conductance characteristics. Interestingly, the Cd-passivated CGNR devices exhibit negative differential resistance (NDR) with remarkably high peak-to-valley current ratios (PVCRs). NDR is a phenomenon critical for high-speed switching, enables efficient signal modulation, making it valuable for nanoscale transistors, memory elements, and oscillators. The highest PVCR is measured to be 53.7 for Cd-CGNR-H which is x10 and x17 times higher than strained graphene nanoribbon and silicene nanoribbon respectively. These findings suggest the promising potential of passivated CGNRs as novel components for high-performance nanoelectronic devices.

Mechanically exfoliated multilayer WS2 flakes are used as the channel of field effect transistors for low-power photodetection in the visible and near-infrared (NIR) spectral range. The electrical characterization as a function of the temperature reveals devices with n-type conduction and slightly different Schottky barriers at the drain and source contacts. The WS2 phototransistors can be operated in self-powered mode, yielding both a current and a voltage when exposed to light. The spectral photoresponse in the visible and the NIR ranges shows a high responsivity (4.5 μA/W) around 1250 nm, making the devices promising for telecommunication applications.

The properties and performance of two-dimensional (2D) materials can be greatly affected by point defects. PtTe 2 , a 2D material that belongs to the group 10 transition metal dichalcogenides, is a type-II Dirac semimetal, which has gained a lot of attention recently due to its potential for applications in catalysis, photonics, and spintronics. Here, we provide an experimental and theoretical investigation of point defects on and near the surface of PtTe 2 . Using scanning tunneling microscopy and scanning tunneling spectroscopy (STS) measurements, in combination with first-principle calculations, we identify and characterize five common surface and subsurface point defects. The influence of these defects on the electronic structure of PtTe 2 is explored in detail through grid STS measurements and complementary density functional theory calculations. We believe these findings will be of significance to future efforts to engineer point defects in PtTe 2 , which is an interesting and enticing approach to tune the charge-carrier mobility and electron–hole recombination rates, as well as the site reactivity for catalysis.

In this work, we present a comprehensive theoretical and experimental study of quantum confinement in layered platinum diselenide (PtSe 2 ) films as a function of film thickness. Our electrical measurements, in combination with density functional theory calculations, show distinct layer-dependent semimetal-to-semiconductor evolution in PtSe 2 films, and highlight the importance of including van der Waals interactions, Green’s function calibration, and screened Coulomb interactions in the determination of the thickness-dependent PtSe 2 energy gap. Large-area PtSe 2 films of varying thickness (2.5–6.5 nm) were formed at 400 °C by thermally assisted conversion of ultra-thin platinum films on Si/SiO 2 substrates. The PtSe 2 films exhibit p -type semiconducting behavior with hole mobility values up to 13 cm 2 /V·s. Metal-oxide-semiconductor field-effect transistors have been fabricated using the grown PtSe 2 films and a gate field-controlled switching performance with an I ON / I OFF ratio of >230 has been measured at room temperature for a 2.5–3 nm PtSe 2 film, while the ratio drops to <2 for 5–6.5 nm-thick PtSe 2 films, consistent with a semiconducting-to-semimetallic transition with increasing PtSe 2 film thickness. These experimental observations indicate that the low-temperature growth of semimetallic or semiconducting PtSe 2 could be integrated into the back-end-of-line of a silicon complementary metal-oxide-semiconductor process.

Topological Insulators (TIs) present an interesting materials platform for nanoscale, high frequency devices because they support high mobility, low scattering electronic transport within confined surface states. However, a robust methodology to control the properties of surface plasmons in TIs has yet to be developed. Surface doping of TIs with molecules may provide tunable control of the two-dimensional plasmons in Bi 2 Se 3 , but exploration of such heterostructures is still at an early stage and usually confined to monolayers. We have grown heterostructures of Bi 2 Se 3 /C 60 with exceptional crystallinity. Electron energy loss spectroscopy (EELS) reveals significant hybridisation of π states at the interface, despite the expectation for only weak van der Waals interactions, including quenching of 2D plasmons. Momentum-resolved EELS measurements are used to probe the plasmon dispersion, with Density Functional Theory predictions providing an interpretation of results based on interfacial charge dipoles. This work provides growth methodology and characterization of highly crystalline TI/molecular interfaces that can be engineered for plasmonic applications in energy, communications and sensing. Topological insulators offer promising potential for nanoscale, high-frequency devices, yet controlling surface plasmon properties remains challenging. Here, the authors grow Bi 2 Se 3 /C 60 heterostructures with exceptional crystallinity, using electron energy loss spectroscopy and density functional theory to reveal significant π state hybridization and quenching of 2D plasmons.

This study demonstrates the oxidation-driven degradation of exfoliated GaSe highlighting the changes to not only the material’s morphology but its chemical composition as well. We have employed a number of simulation and experimental techniques, including DFT calculations, SEM, EDX and Raman spectroscopy, to understand the atomic structure and vacancy effects between the β and ε polytypes, and to understand the degradation occurring. The combined results of the DFT and experimental results show that the crystal used was the β polytype with a bandgap value of ~ 1.92 eV. Further experimental analysis demonstrates that the oxidation occurs on the surface of the material producing Ga2O3 which is possibly due to defect sites or dangling bonds. This oxidation encourages the formation of hemispherical blisters on the material surface. EDX analysis indicates that these blisters are Se-rich while Raman spectroscopy confirms the presence of amorphous and crystalline Se in these regions while also showing the disappearance of the dominant vibrational modes of GaSe. This work emphasises the importance of the environment’s role and developing encapsulation strategies in relation to interface engineering and material stability for fabricating air-stable nanoelectronic devices.

Topological Insulators (TIs) present an interesting materials platform for nanoscale, high frequency devices because they support high mobility, low scattering electronic transport within confined surface states. However, a robust methodology to control the properties of surface plasmons in TIs has yet to be developed. Surface doping of TIs with molecules may provide tunable control of the two-dimensional plasmons in Bi Se , but exploration of such heterostructures is still at an early stage and usually confined to monolayers. We have grown heterostructures of Bi Se /C with exceptional crystallinity. Electron energy loss spectroscopy (EELS) reveals significant hybridisation of states at the interface, despite the expectation for only weak van der Waals interactions, including quenching of 2D plasmons. Momentum-resolved EELS measurements are used to probe the plasmon dispersion, with Density Functional Theory predictions providing an interpretation of results based on interfacial charge dipoles. This work provides growth methodology and characterization of highly crystalline TI/molecular interfaces that can be engineered for plasmonic applications in energy, communications and sensing.

Topological Insulators (TIs) present an interesting materials platform for nanoscale, high frequency devices because they support high mobility, low scattering electronic transport within confined surface states. However, a robust methodology to control the properties of surface plasmons in TIs has yet to be developed. We propose that charge transfer between Bi\\(_2\\)Se\\(_3\\) and crystalline C\\(_{60}\\) films may provide tunable control of the two-dimensional plasmons in Bi\\(_2\\)Se\\(_3\\). We have grown heterostructures of Bi\\(_2\\)Se\\(_3\\)/C\\(_{60}\\) with exceptional crystallinity. Electron energy loss spectroscopy (EELS) reveals significant hybridisation of \\(\\pi\\) states at the interface, despite the expectation for only weak van der Waals interactions, including quenching of 2D plasmons. Momentum-resolved EELS measurements are used to probe the plasmon dispersion, with Density Functional Theory predictions providing an interpretation of results based on interfacial charge dipoles. Our measurements suggest a robust methodology for tuneable TI interfaces that can be engineered for plasmonic applications in computing, communications and sensing.

Platinum diselenide (PtSe_2) field-effect transistors with ultrathin channel regions exhibit p-type electrical conductivity that is sensitive to temperature and environmental pressure. Exposure to a supercontinuum white light source reveals that positive and negative photoconductivity coexists in the same device. The dominance of one type of photoconductivity over the other is controlled by environmental pressure. Indeed, positive photoconductivity observed in high vacuum converts to negative photoconductivity when the pressure is rised. Density functional theory calculations confirm that physisorbed oxygen molecules on the PtSe_2 surface act as acceptors. The desorption of oxygen molecules from the surface, caused by light irradiation, leads to decreased carrier concentration in the channel conductivity. The understanding of the charge transfer occurring between the physisorbed oxygen molecules and the PtSe_2 film provides an effective route for modulating the density of carriers and the optical properties of the material.