108 research outputs found
Anomalous insulator metal transition in boron nitride-graphene hybrid atomic layers
The study of two-dimensional (2D) electronic systems is of great fundamental
significance in physics. Atomic layers containing hybridized domains of
graphene and hexagonal boron nitride (h-BNC) constitute a new kind of
disordered 2D electronic system. Magneto-electric transport measurements
performed at low temperature in vapor phase synthesized h-BNC atomic layers
show a clear and anomalous transition from an insulating to a metallic behavior
upon cooling. The observed insulator to metal transition can be modulated by
electron and hole doping and by the application of an external magnetic field.
These results supported by ab-initio calculations suggest that this transition
in h-BNC has distinctly different characteristics when compared to other 2D
electron systems and is the result of the coexistence between two distinct
mechanisms, namely, percolation through metallic graphene networks and hopping
conduction between edge states on randomly distributed insulating h-BN domains.Comment: 9 pages, 15 figure
Two-step fabrication of nanoporous copper films with tunable morphology for SERS application
peer-reviewedIt is important to design and fabricate nanoporous metals (NPMs) with optimized microstructures for specific applications. In this contribution, nanoporous coppers (NPCs) with controllable thicknesses and pore sizes were fabricated via the combination of a co-sputtering of Cu/Ti with a subsequent dealloying process. The effect of dealloying time on porous morphology and the corresponding surface enhanced Raman scattering (SERS) behaviors were systematically investigated. Transmission electron microscopy (TEM) identified the presences of the gaps formed between ligaments and also the nanobumps on the nanoparticle-aggregated ligament surface, which were likely to contribute as the “hot spots” for electromagnetic enhancement. The optimal NPC film exhibited excellent SERS performance towards Rhodamine 6G (R6G) with a low limiting detection (10−9 M), along with good uniformity and reproducibility. The calculated enhancement factor of ca. 4.71 × 107 was over Au substrates and comparable to Ag systems, promising the proposed NPC as a cheap candidate for high-performance SERS substrate
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