In MoS₂ field-effect transistors, the current or voltage fluctuations related to either mobility- or number-dependent relationships are characterized by low-frequency noise. This noise can typically be used to evaluate the application limits of MoS₂-based electronic devices. In this work, the low-frequency noise characteristics of single-crystal bilayer MoS₂ grown by chemical vapor deposition (CVD) are systematically investigated and found to offer significant performance improvements compared with those based on the monolayer MoS₂ channel. At f = 100 Hz, the normalized drain current power spectral density (S_I/I_d²) is 2.4 × 10⁻¹⁰Hz⁻¹ and 3.1 × 10⁻⁹Hz⁻¹ for bilayer and monolayer MoS₂ transistors, respectively. The 1/f noise behavior can be accurately described by McWhorter's carrier number fluctuation model for both transistor types, suggesting that carrier trapping and de-trapping by dielectric defects is the dominant mechanism of 1/f noise in CVD MoS₂ transistors. Furthermore, a minimal WLS_I/I_d² of 3.1 × 10⁻¹⁰ μm²/Hz (where W is the gate width and L is the gate length) is achieved at V_bg = 3 V by effectively reducing the contact resistance of bilayer MoS₂ transistors using a back-gate voltage. These results demonstrate that CVD bilayer MoS₂ is a promising candidate for future large-scale 2D-semiconductor-based electronic applications with improved noise performance.

Two-dimensional (2D) MoS₂ have attracted tremendous attention due to their potential applications in future flexible high-frequency electronics. Bilayer MoS₂ exhibits the advantages of carrier mobility when compared with monolayer mobility, thus making the former more suitable for use in future flexible high-frequency electronics. However, there are fewer systematical studies of chemical vapor deposition (CVD) bilayer MoS₂ radiofrequency (RF) transistors on flexible polyimide substrates. In this work, CVD bilayer MoS₂ RF transistors on flexible substrates with different gate lengths and gigahertz flexible frequency mixers were constructed and systematically studied. The extrinsic cutoff frequency (f_T) and maximum oscillation frequency (f_max) increased with reducing gate lengths. From transistors with a gate length of 0.3 μm, we demonstrated an extrinsic f_T of 4 GHz and f_max of 10 GHz. Furthermore, statistical analysis of 14 flexible MoS₂ RF transistors is presented in this work. The study of a flexible mixer demonstrates the dependence of conversion gain versus gate voltage, LO power and input signal frequency. These results present the potential of CVD bilayer MoS₂ for future flexible high-frequency electronics.

The piezoelectric properties of 4-(4-dimethylaminostyryl) methylpyridine p-toluene sulfonate (DAST)-polydimethylsiloxane (PDMS) composite thin film was investigated. Flexible nanogenerators based on zinc oxide (ZnO) nanowire (NW) arrays/DAST-PDMS were fabricated. DAST holds organic crystal structure, and it can possess piezoelectric properties, and it can enhance the piezoelectric properties of ZnO NW arrays. PDMS can not only mix DAST powder with a liquid to prepare a thin film but also protect ZnO NW arrays and DAST from deterioration. When applying pressure with a balance weight of 100 g, the flexible nanogenerator based on ZnO NW arrays/DAST-PDMS can generate an output voltage of 2.3 V, which is much larger than that of the nanogenerator based on ZnO NW arrays. The effect of the strength of vertical external force, frequency of vertical external force, and degree of bending deformation on the ZnO NW arrays/DAST-PDMS flexible nanogenerators were investigated in this Letter. In our experiments, the output voltage of the ZnO NW arrays/DAST-PDMS flexible nanogenerators can reach 3.3 V. After bending the nanogenerator 20 times, the energy collection device based on the ZnO NW arrays/DAST-PDMS flexible nanogenerator was able to light an LED bulb.

We study the Josephson current (supercurrent) in a system consisting of two superconductors connected to a single-level quantum dot (QD), which is also side-coupled to a nanowire hosting Majorana bound states (MBSs). Our results show that the MBSs change both the peak height and position in the current-carrying density of states (CCDOS), and this determines the amplitude of the Josephson current due to the phase difference between the superconductors. By adjusting the energy level in the QD and MBSs-QD hybridization strengths, the magnetic flux penetrating through the closed circuit formed by the QD and the nanowire as well as the direct overlap between the MBSs, one can fully control the electron transport processes. The present results are useful in superconductor-based electrical devices and the newly developed area of superconducting coated conductors.

As an atomically thin semiconductor, 2D molybdenum disulfide (MoS₂) has demonstrated great potential in realizing next-generation logic circuits, radio-frequency (RF) devices and flexible electronics. Although various methods have been performed to improve the high-frequency characteristics of MoS₂ RF transistors, the impact of the back-gate bias on dual-gate MoS₂ RF transistors is still unexplored. In this work, we study the effect of back-gate control on the static and RF performance metrics of MoS₂ high-frequency transistors. By using high-quality chemical vapor deposited bilayer MoS₂ as channel material, high-performance top-gate transistors with on/off ratio of 10⁷ and on-current up to 179 μA/μm at room temperature were realized. With the back-gate modulation, the source and drain contact resistances decrease to 1.99 kΩ∙μm at V_bg = 3 V, and the corresponding on-current increases to 278 μA/μm. Furthermore, both cut-off frequency and maximum oscillation frequency improves as the back-gate voltage increases to 3 V. In addition, a maximum intrinsic f_max of 29.7 GHz was achieved, which is as high as 2.1 times the f_max without the back-gate bias. This work provides significant insights into the influence of back-gate voltage on MoS₂ RF transistors and presents the potential of dual-gate MoS₂ RF transistors for future high-frequency applications.