Abstract Photo- or photoelectric-gating modulation is a promising strategy for high-performance photodetectors, which amplifies photoresponsivity by long-lived trapped charges at the interface. However, the performance is normally limited by the uncontrollable trapping process. Here, we develop a large photoelectric-gating, which enhances interfacial charge trapping process by a van-der-Waals interface with an electric-gating tunable energy barrier in the band alignment. By synergy of photo-gating and electric-gating effects, responsivity and detectivity of 1,4-bis(4-methylstyryl)benzene/tungsten diselenide (WSe 2 ) increase by 25-fold and 3-fold to 3.6 × 10 6 A/W and 8.6 × 10 14 Jones. High-quality two-dimensional van-der-Waals interface is of great importance. Sufficient supply of gas-phase molecules in physical vapor deposition is pivotal to obtain such interface between organic crystal and WSe 2 . As an application, an electric-gating switchable photodetector has been developed, showing great potential of this strategy not only in high-performance photodetectors but also in new photoelectrical devices.
Abstract Relatively low mobility and thermal conductance create challenges for application of tungsten diselenide (WSe 2 ) in high performance devices. Dielectric interface is of extremely importance for improving carrier transport and heat spreading in a semiconductor device. Here, by near-equilibrium plasma-enhanced chemical vapour deposition, we realize catalyst-free growth of poly-crystalline two-dimensional hexagonal-boron nitride (2D-BN) with domains around 20~ 200 nm directly on SiO 2 /Si, quartz, sapphire, silicon or SiO 2 /Si with three-dimensional patterns at 300 °C. Owing to the atomically-clean van-der-Walls conformal interface and the fact that 2D-BN can better bridge the vibrational spectrum across the interface and protect interfacial heat conduction against substrate roughness, both improved performance and thermal dissipation of WSe 2 field-effect transistor are realized with mobility around 56~ 121 cm 2 V −1 s −1 and saturated power intensity up to 4.23 × 10 3 W cm −2 . Owing to its simplicity, conformal growth on three-dimensional surface, compatibility with microelectronic process, it has potential for application in future two-dimensional electronics.
A 2D cross-linked polythiophene network was prepared via surface-confined chemical vapor deposition. Better in-plane conjugation results in improved carrier transport, making it a new type of polythiophene material for electronic applications.
Graphene has attracted tremendous research interest owing to its widespread potential applications. However, these applications are partially hampered by the lack of a general method to produce high-quality graphene at low cost. Here, to the best of our knowledge, we use low-cost solid carbon allotropes as the precursor in plasma-enhanced chemical vapor deposition (PECVD) for the first time, and find that the hydrogen plasma and reaction temperature play a crucial role in the process. Hydrogen plasma etches carbon black, and produces graphene crystals in a high-temperature zone. Based on this finding, a modified PECVD technology is developed, which produces transparent conductive nanographene films directly on various substrates at a temperature as low as 600 °C. For application, the closely packed structure of the nanographene film enables a remarkable temperature-dependent behavior of the resistance with a ratio higher than that previously reported, indicating its great potential for usage in highly sensitive temperature detectors.
Traditional methods to prepare two-dimensional (2D) B–C–N ternary materials (BCxN), such as chemical vapor deposition (CVD), require sophisticated experimental conditions such as high temperature, delicate control of precursors, and postgrowth transfer from catalytic substrates, and the products are generally thick or bulky films without the atomically mixed phase of B–C–N, hampering practical applications of these materials. Here, for the first time, we develop a temperature-dependent plasma-enhanced chemical vapor deposition (PECVD) method to grow 2D BCxN materials directly on noncatalytic dielectrics at low temperature with high controllability. The C, N, and B compositions can be tuned by simply changing the growth temperature. Thus, the properties of the as-made materials including band gap and conductivity are modulated, which is hardly achieved by other methods. A 2D hybridized BC2N film with a mixed BC2N phase is produced, for the first time, with a band gap of about 2.3 eV. The growth temperature is 580–620 °C, much lower than that of traditional catalytic CVD for growing BCxN. The product has a p-type conducting property and can be directly applied in field-effect transistors and sensors without postgrowth transfer, showing great promise for this method in future applications.
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