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Abstract: Tungsten diselenide (WSe2) has emerged as a promising ambipolar semiconductor material for field-effect transistors (FETs) due to its unique electronic properties, including a sizeable band gap, high carrier mobility, and remarkable on–off ratio. However, engineering the contacts to WSe2 remains an issue, and high contact barriers prevent the utilization of the full performance in electronic applications. Furthermore, it could be possible to tune the contacts to WSe2 for effective electron or hole injection and consequently pin the threshold voltage to either conduction or valence band. This would be the way to achieve complementary metal–oxide–semiconductor devices without doping of the channel material.This study investigates the behaviour of two-dimensional WSe2 field-effect transistors with multi-layer palladium diselenide (PdSe2) as a contact material. We demonstrate that PdSe2 contacts favour hole injection while preserving the ambipolar nature of the channel material. This consequently yields high-performance p-type WSe2 devices with PdSe2 van der Waals contacts. Further, we explore the tunability of the contact interface by selective laser alteration of the WSe2 under the contacts, enabling pinning of the threshold voltage to the valence band of WSe2, yielding pure p-type operation of the devices.
Keywords: field-effect transistor, tungsten diselenide, van der Waals, two-dimensional materials
Published in RUNG: 29.05.2024; Views: 649; Downloads: 3
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Keywords: tungsten carbide, hydrogen evolution, overpotential, electro- catalyst, platinum composite
Published in RUNG: 30.08.2018; Views: 5079; Downloads: 0
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Abstract: We used wet-chemistry techniques to prepare colloidal tungsten (W) nanoparticles (NPs). The synthesis of W NPs was conducted using the so called hot-matrix method in 1-octadecene [1]. The sizes of obtained W NPs are in the order of 2 - 5 nm. These W NPs are coated with hydrophobic molecules which allow their dispersion in organic solvents like choloroform (CHCl3). It was found that the colloidal stability of the dispersions is exceptionally high exceeding several years. The stability of W NPs which prevents coagulation allows the preparation of thin films with uniform thicknesses by spin-coating, inkjet-printing and spray coating. We have prepared both tungsten trioxide (WO3) and tungsten carbide (W2C, WC) thin films. The preparation of WO3 thin films was achieved by spin-coating of W NPs on fluorine doped tin oxide (FTO) glass substrates and following thermal treatment in air at 500°C. The preparation of W2C and WC were done after spin-coating of W NPs on graphite substrate and following heat treatment under Ar atmosphere at 1000 and 1450°C. The obtained WO3 and W2C (e.g WC) films were used both in photo/electrochemical water splitting studies. In conclusion, we have developed a procedure for the synthesis of W NPs which can be used for the preparation of different class of materials for water splitting studies.
Keywords: metal oxides, metal carbides, tungsten nanoparticles
Published in RUNG: 09.10.2017; Views: 5667; Downloads: 0
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