Achieving Low Contact Resistance by Engineering a Metal-Graphene Interface Simply with Optical Lithography.

High-performance graphene-based transistors crucially depend on the creation of the high-quality graphene-metal contacts. Here we report an approach for achieving ultralow contact resistance simply with optical lithography by engineering a metal-graphene interface. Note that a significant improvement with optical lithography for the contact-treated graphene device leads to a contact resistance as low as 150 Ω·µm. The residue-free sacrificial film impedes the photoresist from further doping graphene, and all of the source and drain contact regions defined by optical lithography remain intact. This approach, being compatible with complementary metal-oxide-semiconductor (CMOS) fabrication processes regardless of the source of graphene, would hold promise for the large-scale production of graphene-based transistors with optical lithography.

A more reliable measurement method for metal/graphene contact resistance.

The contact resistance of metal/graphene is becoming a major limiting factor for graphene devices. Among various kinds of contact resistance test methods, the transmission line model is the most common approach to extract contact resistance in graphene devices. However, experiments show that in some cases there exists large inaccuracy and instability using this method. In this study, we added a cross-bridge structure at the terminal of the transmission line as a supporting test. This modified transmission line measurement structure can easily compare not only the transmission line and Kelvin contact resistance, getting a more reliable value, but also the other contact-related parameters, such as specific contact resistivity, transfer length and the graphene sheet resistance under and outside contact metal at the same time. The new measurement test is very helpful in enabling us to study the contact property accurately. The specific contact resistivity in our experiment is in the range of 2.0 × 10(-6) Ω · cm(2) and 3.0 × 10(-6) Ω · cm(2) at room temperature. With the temperature decreasing from 290 K to 60 K, the transfer length fluctuates around 1.7 µm, and the specific contact resistivity reduces to less than 2.0 × 10(-6) Ω · cm(2).

The electrochemical transfer of CVD-graphene using agarose gel as solid electrolyte and mechanical support layer.

The transfer of chemical vapor deposition (CVD)-grown graphene is the prerequisite for many applications. Herein, we introduce a simple and eco-friendly electrochemical technique to transfer graphene using agarose gel as the solid electrolyte and a mechanical support layer for graphene sheets. This transfer technique will be a perfect candidate for the industrial applications of graphene.

Controllable atmospheric pressure growth of mono-layer, bi-layer and tri-layer graphene.

Here we report a three-step growth method for high-quality mono-layer, bi-layer and tri-layer graphene with coverage ~90% at atmospheric pressure. The growth temperature and gas flow rate have been found to be the key factors. This method would be of great importance for the large scale production of graphene with defined thickness.

Molecular evidence for the intermolecular S···S interaction in the surface molecular packing motifs of a fused thiophene derivative.

A microscopic investigation of the molecular packing structures of a fused thiophene derivative reveals the important role of intermolecular S···S interaction in directing the 2D self-assembly. Thermal annealing of the assembly results in the irreversible phase transition to a new structure with different molecular trimeric packing motifs.