Ultraviolet photodetectors (PDs) have been fabricated from p-ZnO:(Li,N)/n-ZnO structures in this Letter. The PDs can operate without any external power supply and show response only to a very narrow spectrum range. The self-power character of the devices is due to the built-in electric field in the p-n junctions that can separate the photogenerated electrons and holes while the high spectrum-selectivity has been attributed to the filter effect of the neutral region in the ZnO:(Li,N) layer. The performance of the self-powered highly spectrum-selective PDs degrades little after five months, indicating their good reliability.

Reliable self-powered highly spectrum-selective ZnO ultraviolet photodetectors

Co-doping: an effective strategy for achieving stable p-type ZnO thin films

The evolutionary success in information technology has been sustained by the rapid growth of sensor technology. Recently, advances in sensor technology have promoted the ambitious requirement to build intelligent systems that can be controlled by external stimuli along with independent operation, adaptivity, and low energy expenditure. Among various sensing techniques, field-effect transistors (FETs) with channels made of two-dimensional (2D) materials attract increasing attention for advantages such as label-free detection, fast response, easy operation, and capability of integration. With atomic thickness, 2D materials restrict the carrier flow within the material surface and expose it directly to the external environment, leading to efficient signal acquisition and conversion. This review summarizes the latest advances of 2D-materials-based FET (2D FET) sensors in a comprehensive manner that contains the material, operating principles, fabrication technologies, proof-of-concept applications, and prototypes. First, a brief description of the background and fundamentals is provided. The subsequent contents summarize physical, chemical, and biological 2D FET sensors and their applications. Then, we highlight the challenges of their commercialization and discuss corresponding solution techniques. The following section presents a systematic survey of recent progress in developing commercial prototypes. Lastly, we summarize the long-standing efforts and prospective future development of 2D FET-based sensing systems toward commercialization.

Two-Dimensional Field-Effect Transistor Sensors: The Road toward Commercialization.

Defect luminescence and its mediated physical properties in ZnO

A lithium and nitrogen codoping method has been employed to prepare p-type MgZnO films, and p-MgZnO/i-ZnO/n-ZnO structured light-emitting devices (LEDs) and photodetectors have been fabricated. The LEDs can work continuously for about 97 h under the injection of a 20 mA continuous current, which is the best value ever reported for ZnO-based LEDs. The performance of the photodetectors degrades little after several running cycles. The above results reveal the applicability of the p-MgZnO films in optoelectronic devices.

p-type doping of MgZnO films and their applications in optoelectronic devices.

By employing lithium and nitrogen codoping method, p-type zinc oxide (ZnO) films have been prepared, and the p-type conduction can maintain for 207 days. ZnO p-n junctions have been constructed based on the p-type ZnO. Under the drive of continuous current, obvious emission has been observed from the p-n junctions, and the ZnO p-n junction light-emitting devices (LEDs) can still work after placing in air ambient for 180 days. Room temperature electroluminescence spectra of the p-ZnO:(Li, N)/n-ZnO structured LEDs under continuous current recorded intermittently for 180 days. (C) 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Stable p-type ZnO films obtained by lithium-nitrogen codoping method

Coating two-dimensional (2D) materials with molecules bearing tunable properties imparts their surfaces with functionalities for applications in sensing, nanoelectronics, nanofabrication, and electrochemistry. Here, we report a method for the site-selective surface functionalization of 2D superatomic Re6Se8Cl2 monolayers. First, we activate bulk layered Re6Se8Cl2 by intercalating lithium and then exfoliate the intercalation compound Li2Re6Se8Cl2 in N-methylformamide (NMF). Heating the resulting solution eliminates LiCl to produce monolayer Re6Se8(NMF)2-x (x ≈ 0.4) as high-quality nanosheets. The unpaired electrons on each cluster in Re6Se8(NMF)2-x enable covalent surface functionalization through radical-based chemistry. We demonstrate this to produce four previously unknown surface-functionalized 2D superatomic materials: Re6Se8I2, Re6Se8(SPh)2, Re6Se8(SPhNH2)2, and Re6Se8(SC16H33)2. Transmission electron microscopy, chemical analysis, and vibrational spectroscopy reveal that the in-plane structure of the 2D Re6Se8 material is preserved through surface functionalization. We find that the incoming groups control the density of vacancy defects and the solubility of the 2D material. This approach will find utility in installing a broad array of chemical functionalities on the surface of 2D superatomic materials as a means to systematically tune their physical properties, chemical reactivity, and solution processability.

Site-Selective Surface Modification of 2D Superatomic Re6Se8.

Recently, magnetic topological semimetals have received a lot of attention due to their potential applications in the field of spintronics. By using first-principles calculations, we propose that two ferromagnetic spinel materials of X2MnO4 (X= Li, Na) have Weyl-type nodal chains around the Fermi level. Their stabilities are validated by cohesive energies, phonon dispersions, and elastic constants. The nodal chains are composed of two types of nodal loops, which are protected by the glide operation M̃z, the mirror operation M101 and their equivalent. The drumhead surface states are observed on the (001) surface and they exhibit nontrivial topological features. In addition, under different electron correlations and lattice strains, the semimetal states of these two materials are well kept. Our work provides two promising candidates for exploring the combination of magnetic materials and topological semimetal states.

Shen He

Papers

Stable p-type ZnO films obtained by lithium-nitrogen codoping method

Site-Selective Surface Modification of 2D Superatomic Re6Se8.

Ja n 20 22 Weyl-type nodal chains in X 2 MnO