In spite of recent significant research into various two-dimensional (2D) materials after the emergence of graphene, the development of a new 2D material that provides both high mobility and an appropriate energy band gap (which are crucial for various device applications) remains elusive. In this report, we demonstrate that the carrier transport behaviour of 2D Ti2CTx, which belongs to the family of 2D transition metal carbides and nitrides, can be tuned by modifying the surface group Tx (-OH, -F, and -O). Our results show that 2D Ti2C(OH)xFy and Ti2COx films can be obtained via simple chemical treatment, thermal annealing, and mechanical exfoliation processes. For the first time, we study the carrier transport properties of 2D Ti2CTx field effect transistors (FETs), obtaining the high field effect carrier mobilities of 10(4) cm(2) V(-1) s(-1) at room temperature. The temperature dependent resistivity of the Ti2COx film exhibits semiconductor like Arrhenius behaviour at zero gate voltage, from which we estimate the energy gap of 80 meV. One interesting feature of the FETs based on transition metal carbides is that the field effect mobility at room temperature is less sensitive to the measured transport gaps, which may arise from the dominant charge transport of activated carriers over the narrow energy gaps of the transition metal carbides. Our results open up the possibility that new 2D materials with high mobilities and appropriate band gaps can be achieved, and broaden the range of electronic device applications of Ti2CTx films.

We report the preparation of thickness-controlled few-layer black phosphorus (BP) films through the modulated plasma treatment of BP flakes. Not only does the plasma treatment control the thickness of the BP film, it also removes the chemical degradation of the exposed oxidized BP surface, which results in enhanced field-effect transistor (FET) performance. Our fabricated BP FETs were passivated with poly(methyl methacrylate) (PMMA) immediately after the plasma etching process. With these techniques, a high field-effect mobility was achieved, 1150 cm(2)/(V s), with an Ion/Ioff ratio of ∼10(5) at room temperature. Furthermore, a fabricated FET with plasma-treated few-layer BP that was passivated with PMMA was found to retain its I-V characteristics and thus to exhibit excellent environmental stability over several weeks.

the third method, that is, the introduction of magnetism in graphene with the proximity effect in the interface of magnetic insulators and graphene. Pioneer works have been demonstrated with 3D bulk magnetic insulators like yttrium iron garnet, europium (II) sulfide, and bismuth ferrite. [7][8][9][10][11][12][13][14][15] Due to the short-range nature of the magnetic exchange coupling, a fully 2D van der Waals heterostructures is desired for downsizing the device and introducing magnetic proximity effect (MPE) at the same time. The recent profound discoveries of 2D ferromagnets [16][17][18][19][20][21][22][23][24][25][26][27][28][29] bring the possibility of 2D ferromagnetic van der Waals heterostructures, [30][31][32][33][34][35][36] it is urgent and essential to comprehensively investigate the magnetic coupling between graphene and 2D ferromagnetic materials for developing 2D spintronic devices. Not just the evidence of the existence of MPE in 2D ferromagnetic van der Waals heterostructures, [37,38] here, we report the direct observation of MPE in graphene/CrBr 3 van der Waals heterostructures by probing Zeeman spin Hall effect (ZSHE) through non-local transport measurements. A further quantitative estimation of Zeeman splitting field demonstrates a significant magnetic proximity exchange field even in a low magnetic field. Furthermore, we observe anomalous longitudinal resistance changes at the Dirac point R XX,D with increasing external magnetic field near ν = 0. This may attribute to the MPE induced ground state phases transformation of graphene from the ferromagnetic state at the lower magnetic field and a canted antiferromagnetic state at a higher field in quantum Hall regime.A typical graphene/CrBr 3 van der Waals heterostructure with Hall bar structure for electrical transport measurement is fabricated as shown in Figure 1a. In order to reach the best performance and a substantial MPE in graphene/CrBr 3 heterostructures, we optimize the fabrication process and conditions to achieve the desired heterostructures (see Experimental Section for details). The sample in the final stage is encapsulated and protected by poly(methyl methacrylate) (PMMA), which keeps the device surface away from the moisture and air for cryotemperature tests. The atomic structure of layered CrBr 3 is shown in Figure 1b. The Cr 3+ ions are configured in a honeycomb network, and the green arrows represent the spin direction of Cr atoms, which are found to exhibit a strong ferromagnetic coupling. [39][40][41][42][43][44] The Raman spectra of Figure 1c indicates that the monolayer graphene still preserves a high crystal quality when heterostructured with CrBr 3 layer. The optical image in 2D van der Waals heterostructures serve as a promising platform to exploit various physical phenomena in a diverse range of novel spintronic device applications. Efficient spin injection is the prerequisite for these devices. The recent discovery of magnetic 2D materials leads to the possibility of fully 2D van der Waals spintronics devices by implemen...

Measurement of nonlinear response offers powerful probes of material propertiesnot accessible at linear order, as they follow distinct symmetry requirements 1,2,3,4,5,6 . For instance, unlike the linear Hall effect, the second-order nonlinear Hall effect typically requires the breaking of inversion symmetry rather than time reversal symmetry 1 , and its successful detection in recent experiments on ultrathin WTe2 has attracted significant attention 7,8 . This second-order nonlinear Hall effect could be used to probe the Berry curvature, a band geometric property, in non-magnetic materials, just like the anomalous Hall effect being used to probe the Berry curvature in magnetic materials 9,10 . As another intrinsic band geometric property, the Berry-connection polarizability tensor was theoretically predicted to play a crucial role in high-order responses 11 but not yet experimentally demonstrated. Here, we report for the first time a high-order nonlinear Hall effect in multi-layer 𝑻 𝒅 -MoTe2 samples. Unprecedently, the third-order Hall

We report a simple and scalable method to fabricate homogeneous transparent conductive thin films (TiCT, one of the MXene) by dip coating of an AlO substrate in a colloidal solution of large-area TiCT thin flakes. Scanning electron microscopy and atomic force microscopy images exhibit the wafer-scale homogeneous TiCT thin film (∼5 nm) covering the whole substrate. The sheet resistance is as low as 70 Ω/sq at 86% transmittance, which corresponds to the high figure of merit (FOM) of 40.7. Furthermore, the thickness of the film is tuned by a SF+Ar plasma treatment, which etches TiCT film layer by layer and removes the top oxidized layer without affecting the bottom layer of the TiCT flake. The resistivity of plasma-treated TiCT film is further decreased to 63 Ω/sq with an improved transmittance of 89% and FOM of 51.3, demonstrating the promise of TiCT for future transparent conductive electrode application.