Tunable Electronic Properties of Few-Layer Tellurene under In-Plane and Out-of-Plane Uniaxial Strain

3D Chiral Micro-Pinwheels Based on Rolling-Up Kirigami Technology

Expanding micro-/nanostructures into 3D ones results not only in boosting structural integration level with compact geometry but also enhancing a device's complexity and functionality. Herein, a synergetic 3D micro-/nanoshape transformation is proposed by combining kirigami and rolling-up techniques, or rolling-up kirigami, for the first time. As an example, micro-pinwheels with multiple flabella are patterned on pre-stressed bilayer membranes and rolled up into 3D structures. The flabella are designed when they are patterned on a 2D thin film, facilitating the integration of micro-/nanoelement and other functionalization processes during 2D patterning, which is typically much easier than post-shaping an as-fabricated 3D structure by removing redundant materials or 3D printing. The dynamic rolling-up process is simulated using elastic mechanics with a movable releasing boundary. Mutual competition and cooperation among flabella are observed during the whole release process. More importantly, the mutual conversion between translation and rotation offers a reliable platform for developing parallel microrobots and adaptive 3D micro-antennas. Additionally, 3D chiral micro-pinwheel arrays integrated into a microfluidic chip are successfully applied to detect organic molecules in solution using a terahertz apparatus. With an extra actuation, active micro-pinwheels can potentially serve as a base to functionalize 3D kirigami as tunable devices.

High performance 1D-2D CuO/MoS2 photodetectors enhanced by femtosecond laser-induced contact engineering

The integration of 2D materials with other dimensional materials opens up rich possibilities for both fundamental physics and exotic nanodevices. However, current mixed-dimensional heterostructures often suffer from interfacial contact issues and environment-induced degradation, which severely limits their performance in electronics/optoelectronics. Herein, we demonstrate a novel BN-encapsulated CuO/MoS₂ 2D-1D van der Waals heterostructure photodetector with an ultrahigh photoresponsivity which is 10-fold higher than its previous 2D-1D counterparts. The interfacial contact state and photodetection capabilities of 2D-1D heterojunctions are significantly improved via femtosecond laser irradiation induced MoS₂ wrapping and contamination removal. These h-BN protected devices show highly sensitive, gate-tunable and robust photoelectronic properties. By controlling the gate and bias voltages, the device can achieve a photoresponsivity as high as 2500 A W^-1 in the forward bias mode, or achieve a high detectivity of 6.5 × 10¹¹ Jones and a typical rise time of 2.5 ms at reverse bias. Moreover, h-BN encapsulation effectively protects the mixed-dimensional photodetector from electrical depletion by gas molecules such as O₂ and H₂O during fs laser treatment or the operation process, thus greatly improving the stability and service life in harsh environments. This work provides a new way for the further development of high performance, low cost, and robust mixed-dimensional heterostructure photodetectors by femtosecond laser contact engineering.

Direct Laser Irradiation and Modification of 2D Te for Development of Volatile Memristor

Laser irradiation, as a kind of post-fabrication method for two-dimensional (2D) materials, is a promising way to tune the properties of materials and the performance of corresponding nano-devices. As the memristor has been regarded as an excellent candidate for in-memory devices in next-generation computing system, the application of laser irradiation in developing excellent memristor based on 2D materials should be explored deeply. Here, tellurene (Te) flakes are exposed to a 532 nm laser in the air atmosphere to investigate the evolutions of the surface morphology and atom structures under different irradiation parameters. Laser is capable of thinning the flakes, inducing amorphous structures, oxides and defects, and forming nanostructures by controlling the irradiation power and time. Furthermore, the laser-induced oxides and defects promote the migration of metal ions in Te, resulting in the formation of the conductive filaments, which provides the switching behavers of volatile memristor, opening a route to the development of next-generation nano-devices.