Graphene and other two-dimensional materials have received considerable attention regarding their potential applications in nano-electronics. Here, we report top-gate nonvolatile memory field-effect transistors (FETs) with different layers of MoSe ₂ nanosheets channel gated by ferroelectric film. The conventional gate dielectric of FETs was replaced by a ferroelectric thin film that provides a ferroelectric polarization electric field, and therefore defined as an Fe-FET where the poly (vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) was used as the gate dielectric. Among the devices with MoSe ₂ channels of different thicknesses, the device with a single layer of MoSe ₂ exhibited a large hysteresis of electronic transport with an over 10 ⁵ write/erase ratio, and displayed excellent retention and endurance performance. The possible mechanism of the device’s good properties was qualitatively analyzed using band theory. Additionally, a comprehensive study comparing the memory properties of MoSe ₂ channels of different thicknesses is presented. Increasing the numbers of MoSe ₂ layers was found to cause a reduced memory window. However, MoSe ₂ thickness of 5 nm yielded a write/erase ratio of more than 10 ³ . The results indicate that, based on a Fe-FET structure, the combination of two-dimensional semiconductors and organic ferroelectric gate dielectrics shows good promise for future applications in nonvolatile ferroelectric memory.

Two-dimensional (2D) layered semiconductor materials, such as transition metal dichalcogenides (TMDCs), have attracted considerable interests because of their intriguing optical and electronic properties. Controlled growth of TMDC crystals with large grain size and atomically smooth surface is indeed desirable but remains challenging due to excessive nucleation. Here, we have synthesized high-quality monolayer, bilayer MoSe₂ triangular crystals, and continuous thin films with controlled nucleation density via reverse-flow chemical vapor deposition (CVD). High crystallinity and good saturated absorption performance of MoSe₂ have been systematically investigated and carefully demonstrated. Optimized nucleation and uniform morphology could be achieved via fine-tuning reverse-flow switching time, growth time and temperature, with corresponding growth kinetics proposed. Our work opens up a new approach for controllable synthesis of monolayer TMDC crystals with high yield and reliability, which promote surface/interface engineering of 2D semiconductors towards van der Waals heterostructure device applications.

In our previous work on ultra-fast silicon detectors, extremely small carrier drift times of 50–100 picoseconds were predicted for electrode spacing of 5–10 μm. Expanding on these previous works, we systematically study the electrical characteristics of the ultra-fast, 3D-trench electrode silicon detector cell with p-type bulk silicon, such as electric potential distribution, electric field distribution, hole concentration distribution, and leakage current to analyze the full detector depletion voltage and other detector properties. To verify the prediction of ultra-fast response times, we simulate the instant induced current curves before and after irradiation with different minimum ionizing particle (MIP) hitting positions. High position resolution pixel detectors can be fabricated by constructing an array of these extremely small detector cells.