We report on a new chemical sensor based on black phosphorus/molybdenum diselenide van der Waals hetero-junctions. Due to the atomically thin nature of two-dimensional (2D) materials, surface adsorption of gas molecules can effectively modulate the band alignment at the junction interface, making the device a highly sensitive detector for chemical adsorptions. Compared to sensors made of homogeneous nanomaterials, the hetero-junction demonstrates considerably lower detection limit and higher sensitivity toward nitrogen dioxide. Kelvin probe force microscopy and finite element simulations have provided experimental and theoretical explanations for the enhanced performance, proving that chemical adsorption can induce significant changes in band alignment and carrier transport behaviors. The study demonstrates the potential of van der Waals hetero-junction as a new platform for sensing applications, and provides more insights into the interaction between gaseous molecules and 2D hetero-structures.

Metalenses are expected to play an increasingly important role in miniaturized and integrated optical imaging components/systems. However, devising broadband achromatic metalenses with high focusing efficiencies is still quite challenging. In this work, we proposed an aperture-shared partition phase cooperative manipulation approach for designing a high-efficiency broadband achromatic metalens composed of two concentric sub-metalenses. As a proof-of-concept, an achromatic polarization-independent metalens is successfully designed for the visible and near-infrared range from 450 nm to 1400 nm with the focusing efficiency over 70% for the wavelength range of 600 nm to 1400 nm. The approach reported here provides a possibility for designing a high-performance metalens, which has great potential applications in integrated optics.

Research progress of graphene and its composite electrodes in neuronal signal recording, stimulation and related optical signal coupling technology.

By using the first-principles method, the electronic structures and magnetism of equiatomic quaternary Heusler alloys FeRhCrSi and FePdCrSi were calculated. The results show that both FeRhCrSi and FePdCrSi compounds are ferrimagnets. Both compounds are half-metals and their half-metallicity can be maintained in a wide range of variation of the lattice constant under hydrostatic strain and c/a ratio range under tetragonal distortion, implying that they have low sensitivity to external interference. Furthermore, the total magnetic moments are integers, which are typical characteristics of half-metals. The calculated negative formation energy and cohesive energy indicate that these two alloys have good chemical stability. Furthermore, the value of the elastic constants and the various moduli indicate the mechanical stability of these two alloys. Thus, FeRhCrSi and FePdCrSi are likely to be synthesized in the experiment.