Recently, new devices combining two-dimensional (2D) materials with ferroelectrics, have been a new hotspot for promising applications in electronics and optoelectronics. Here, we design a new type of FET using the 2D MoS and poly(vinylidene fluoride-trifluoroethylene-chlorofloroethylene) terpolymer ferroelectric relaxor. The devices exhibit excellent performance including a large on/off ratio) and an insignificant leakage current. Moreover, the hysteresis characteristics are effectively modulated for its ferroelectric properties at low temperature. Additionally, a broad range photoresponse (visible to 1.55 μm) and a high sensitivity (>300 A/W, λ = 450 nm) are achieved. These results indicate that ferroelectric relaxor can be applied into the high-performance 2D optoelectronic devices.

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.

Epistasis refers to fitness or functional effects of mutations that depend on the sequence background in which these mutations arise. Epistasis is prevalent in nature, including populations of viruses, bacteria, and cancers, and can contribute to the evolution of drug resistance and immune escape. However, it is difficult to directly estimate epistatic effects from sampled observations of a population. At present, there are very few methods that can disentangle the effects of selection (including epistasis), mutation, recombination, genetic drift, and genetic linkage in evolving populations. Here we develop a method to infer epistasis, along with the fitness effects of individual mutations, from observed evolutionary histories. Simulations show that we can accurately infer pairwise epistatic interactions provided that there is sufficient genetic diversity in the data. Our method also allows us to identify which fitness parameters can be reliably inferred from a particular data set and which ones are unidentifiable. Our approach therefore allows for the inference of more complex models of selection from time series genetic data, while also quantifying uncertainty in the inferred parameters.