A coordinatively unsaturated single iron site confined in a graphene matrix shows an ultrahigh activity for catalytic oxidation.

Resistive switching (RS) is an interesting property shown by some materials systems that, especially during the last decade, has gained a lot of interest for the fabrication of electronic devices, with electronic nonvolatile memories being those that have received the most attention. The presence and quality of the RS phenomenon in a materials system can be studied using different prototype cells, performing different experiments, displaying different figures of merit, and developing different computational analyses. Therefore, the real usefulness and impact of the findings presented in each study for the RS technology will be also different. This manuscript describes the most recommendable methodologies for the fabrication, characterization, and simulation of RS devices, as well as the proper methods to display the data obtained. The idea is to help the scientific community to evaluate the real usefulness and impact of an RS study for the development of RS technology.

A long-wavelength infrared (IR) photodetector based on two-dimensional materials working at room temperature would have wide applications in many aspects in remote sensing, thermal imaging, biomedical optics, and medical imaging.However, sub-bandgap light detection in graphene and black phosphorus has been a long-standing scientific challenge because of low photoresponsivity, instability in the air and high dark current. In this study, we report a highly sensitive, air-stable and operable long-wavelength infrared photodetector at room temperature based on PdSe2 phototransistors and its heterostructure. A high photoresponsivity of~42.1 AW -1 (at 10.6 μm) was demonstrated, which is an order of magnitude higher than the current 2 record of platinum diselenide. Moreover, the dark current and noise power density were suppressed effectively by fabricating a van der Waals heterostructure. This work fundamentally contributes to establishing long-wavelength infrared detection by PdSe2 at the forefront of long-IR two-dimensional-materials-based photonics.KEYWORDS: photodetector, long-wavelength infrared, photoresponsivity, palladium diselenide, detectivity, heterostructure Scalable two-dimensional, long-wavelength infrared photodetectors operating at room temperature are highly desirable for upcoming remote sensing, thermal imaging, biomedical optics, medical imaging, and space communication applications.State-of-the-art long-wavelength infrared (LWIR) photodetectors based on narrow-bandgap semiconductors using HgCdTe alloy and III-V compound quantum structures suffer from several major challenges, such as the need for operation at liquid nitrogen temperatures, the complexity of sample synthesis and challenging device fabrication processes. 1 Commercial widely used LWIR photodetectors with 5-20 nm wavelength operating at room temperature based on VOx and α-Si possess many advantages such as compatibility with mass production, low price, and facile fabrication processes. However, their low sensitivity, short detection wavelength range and low response speed restrict their application. 2 Recently, the discovery of graphene, a two-dimensional layered material, has offered an opportunity to overcome some of these issues. In previous studies, LWIR photodetectors based on a graphene nanoribbon, 3 graphene quantum dot-like arrays 4 and a graphene heterostructure 5 have been demonstrated. Generally, the photoresponsivity has been low, approximately 7.5 μA W -1 in the graphene nanoribbon, due to the limited light absorption of 2.3% in an atomic thin layer, 6 and a high dark current due to the gapless band structure. Although strategies such as surface plasma enhanced light absorption 7 and carrier multiplication [8][9][10] have been adopted to enhance the photoresponsivity of graphene photodetectors, the photoresponsivity is still relatively low at several tens of mA W -1 .A photoresponsivity of up to 0.4 AW -1 at 10.6 μm was demonstrated by etching graphene to form quantum-dot-like arrays. 4 The resulting high responsivity was 16 ...

Dirac semimetals have attracted extensive attentions in recent years. It has been theoretically suggested that many-body interactions may drive exotic phase transitions, spontaneously generating a Dirac mass for the nominally massless Dirac electrons. So far, signature of interaction-driven transition has been lacking. In this work, we report high-magnetic-field transport measurements of the Dirac semimetal candidate ZrTe5. Owing to the large g factor in ZrTe5, the Zeeman splitting can be observed at magnetic field as low as 3 T. Most prominently, high pulsed magnetic field up to 60 T drives the system into the ultra-quantum limit, where we observe abrupt changes in the magnetoresistance, indicating field-induced phase transitions. This is interpreted as an interaction-induced spontaneous mass generation of the Dirac fermions, which bears resemblance to the dynamical mass generation of nucleons in high-energy physics. Our work establishes Dirac semimetals as ideal platforms for investigating emerging correlation effects in topological matters.

Van der Waals (vdW) heterodiodes based on two-dimensional (2D) materials have shown tremendous potential in photovoltaic detectors and solar cells. However, such 2D photovoltaic devices are limited by low quantum efficiencies due to the severe interface recombination and the inefficient contacts. Here, we report an efficient MoS2/AsP vdW hetero-photodiode utilizing a unilateral depletion region band design and a narrow bandgap AsP as an effective carrier selective contact. The unilateral depletion region is verified via both the Fermi level and the infrared response measurements. The device demonstrates a pronounced photovoltaic behavior with a short-circuit current of 1.3 μA and a large open-circuit voltage of 0.61 V under visible light illumination. Especially, a high external quantum efficiency of 71%, a record high power conversion efficiency of 9% and a fast response time of 9 μs are achieved. Our work suggests an effective scheme to design high-performance photovoltaic devices assembled by 2D materials.