Graphene has become the focus of extensive research efforts and it can now be produced in waferscale. for the development of next generation graphene-based electronic components, electrical characterization of graphene is imperative and requires the measurement of work function, sheet resistance, carrier concentration and mobility in both macro-, micro-and nano-scale. Moreover, commercial applications of graphene require fast and large-area mapping of electrical properties, rather than obtaining a single point value, which should be ideally achieved by a contactless measurement technique. We demonstrate a comprehensive methodology for measurements of the electrical properties of graphene that ranges from nano-to macro-scales, while balancing the acquisition time and maintaining the robust quality control and reproducibility between contact and contactless methods. the electrical characterisation is achieved by using a combination of techniques, including magneto-transport in the van der pauw geometry, tHz time-domain spectroscopy mapping and calibrated Kelvin probe force microscopy. The results exhibit excellent agreement between the different techniques. Moreover, we highlight the need for standardized electrical measurements in highly controlled environmental conditions and the application of appropriate weighting functions.The unique properties of graphene 1 and the increasing demand for large-scale production were the reason for the development of various industrial methods to grow this material. One of the most promising methods is the use of CVD to grow graphene onto various metallic substrates. In CVD growth, graphene is grown on the surface of the metal after hydrocarbons decompose 2 . The most promising metal substrate used until now is Cu 3 , however graphene is currently grown also on Ni(111) 4-6 , Ru(0001) 7 , Pt(111) 8,9 , and Ir(111) 9-11 . Subsequently to the growth process, for graphene to be use in electronic applications, it needs to be transferred on an insulating substrate (i.e. Si/SiO 2 , quartz or polyethylene terephthalate (PET), which is a transparent and flexible substrate). The already happening now use of graphene in RF electronics 12 , integrated circuits 13 and optoelectronics 14 has triggered impressive progress in large-scale production, however the community still lacks standardised electrical measurements to extract useful parameters such as carrier concentration, mobility and sheet resistance, all of those are often presented as figures-of-merit of the graphene quality. Currently, the most widely used method for electrical characterisation involves magneto-transport measurements in lithographically patterned Hall bars to extract carrier concentration, mobility and resistance. However, this method is not suitable for high throughput characterisation and often the measured graphene is significantly altered due to the microfabrication processes, in which case the electrical properties of the pristine transferred graphene are different from the ones measured. An alternative method fo...
The adoption of 2D transition metal dichalcogenide (TMD) based optoelectronic devices is limited by Fermi level pinning effects and consequent large contact resistances upon contacting TMDs with bulk metal electrodes. A potential solution for near‐ideal Schottky–Mott behavior and concomitant Schottky barrier height control is proposed by contacting TMDs and (semi‐)metals in van der Waals heterostructures. However, measurement approaches to directly assess interface parameters relevant to the Schottky–Mott rule on a local scale are still lacking. In the present work, a heterostructure of monolayer tungsten diselenide (WSe2) with monolayer graphene (1LG) and bilayer graphene (2LG) is investigated on a bottom‐gate substrate. Kelvin probe force microscopy and tip‐enhanced photoluminescence measurements at different electrostatic doping induced Fermi levels in graphene enable decoupling and quantification of contributions from the interface dipole and electrode work function. These are used to locally probe Schottky barrier characteristics with below 32 nm lateral resolution, demonstrating that the WSe2/1LG junction operates at the Schottky–Mott limit (S ≈ 1). At the WSe2/2LG junction, a reduction of the interface dipole is directly related to changes in excitonic emission properties. These are attributed to charge transfer modulation across the interface, critical for obtaining high‐performance transfer characteristics in transistors and related devices.
Nanoscale Schottky Barrier Characteristics The local Schottky–Mott characteristics determine the quality of electronic interfaces in metal–semiconductor van der Waals heterostructures. In the article number 2200196, Sebastian Wood and co‐workers demonstrate how advanced scanning probe microscopy can probe the interface characteristics of monolayer tungsten diselenide on graphene transistors, distinguishing contributions from interface dipoles and graphene work function, and providing evidence for unpinned Fermi levels through electrostatic doping.
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