Nitrogen-Doped Graphene Sheets Grown by Chemical Vapor Deposition: Synthesis and Influence of Nitrogen Impurities on Carrier Transport

A significant advance toward achieving practical applications of graphene as a two-dimensional material in nanoelectronics would be provided by successful synthesis of both n-type and p-type doped graphene. However, reliable doping and a thorough understanding of carrier transport in the presence of charged impurities governed by ionized donors or acceptors in the graphene lattice are still lacking. Here we report experimental realization of few-layer nitrogen-doped (N-doped) graphene sheets by chemical vapor deposition of organic molecule 1,3,5-triazine on Cu metal catalyst. When reducing the growth temperature, the atomic percentage of nitrogen doping is raised from 2.1% to 5.6%. With increasing doping concentration, N-doped graphene sheet exhibits a crossover from p-type to n-type behavior accompanied by a strong enhancement of electron–hole transport asymmetry, manifesting the influence of incorporated nitrogen impurities. In addition, by analyzing the data of X-ray photoelectron spectroscopy, Raman spectroscopy, and electrical measurements, we show that pyridinic and pyrrolic N impurities play an important role in determining the transport behavior of carriers in our N-doped graphene sheets

Magnetic Mesocrystal-Assisted Magnetoresistance in Manganite

Mesocrystal, a new class of crystals as compared to conventional and well-known single crystals and polycrystalline systems, has captured significant attention in the past decade. Recent studies have been focused on the advance of synthesis mechanisms as well as the potential on device applications. In order to create further opportunities upon functional mesocrystals, we fabricated a self-assembled nanocomposite composed of magnetic CoFe₂O₄ mesocrystal in Sr-doped manganites. This combination exhibits intriguing structural and magnetic tunabilities. Furthermore, the antiferromagnetic coupling of the mesocrystal and matrix has induced an additional magnetic perturbation to spin-polarized electrons, resulting in a significantly enhanced magnetoresistance in the nanocomposite. Our work demonstrates a new thought toward the enhancement of intrinsic functionalities assisted by mesocrystals and advanced design of novel mesocrystal-embedded nanocomposites

Tuning Electronic Transport in a Self-Assembled Nanocomposite

Self-assembled nanocomposites with a high interface-to-volume ratio offer an opportunity to overcome limitations in current technology, where intriguing transport behaviors can be tailored by the choice of proper interactions of constituents. Here we integrated metallic perovskite oxide SrRuO₃–wurzite semiconductor ZnO nanocomposites to investigate the room-temperature metal–insulator transition and its effect on photoresponse. We demonstrate that the band structure at the interface can be tuned by controlling the interface-to-volume ratio of the nanocomposites. Photoinduced carrier injection driven by visible light was detected across the nanocomposites. This work shows the charge interaction of the vertically integrated multiheterostructures by incorporating a controllable interface-to-volume ratio, which is essential for optimization of the design and functionality of electronic devices

Giant Photoresponse in Quantized SrRuO₃ Monolayer at Oxide Interfaces

The photoelectric effect in semiconductors is the main mechanism for most modern optoelectronic devices, in which the adequate bandgap plays the key role for acquiring high photoresponse. Among numerous material categories applied in this field, the complex oxides exhibit great possibilities because they present a wide distribution of band gaps for absorbing light with any wavelength. Their physical properties and lattice structures are always strongly coupled and sensitive to light illumination. Moreover, the confinement of dimensionality of the complex oxides in the heterostructures can provide more diversities in designing and modulating the band structures. On the basis of this perspective, we have chosen itinerary ferromagnetic SrRuO₃ as the model material, and fabricated it in one-unit-cell thickness in order to open a small band gap for effective utilization of visible light. By inserting this SrRuO₃ monolayer at the interface of the well-developed two-dimensional electron gas system (LaAlO₃/SrTiO₃), the resistance of the monolayer can be further revealed. In addition, a giant enhancement (>300%) of photoresponse under illumination of visible light with power density of 500 mW/cm² is also observed. Such can be ascribed to the further modulation of band structure of the SrRuO₃ monolayer under the illumination, confirmed by cross-section scanning tunneling microscopy (XSTM). Therefore, this study demonstrates a simple route to design and explore the potential low dimensional oxide materials for future optoelectronic devices