In this letter, a top-gated field effect device (FED) manufactured from monolayer graphene is investigated.Except for graphene deposition, a conventional top-down CMOS-compatible process flow is applied.Carrier mobilities in graphene pseudo-MOS structures are compared to those obtained from top-gated Graphene-FEDs. The extracted values exceed the universal mobility of silicon and silicon-on-insulator MOSFETs.

We study photodetection in graphene near a local electrostatic gate, which enables active control of the potential landscape and carrier polarity. We find that a strong photoresponse only appears when and where a p-n junction is formed, allowing on-off control of photodetection.Photocurrents generated near p-n junctions do not require biasing and can be realized using submicron gates. Locally modulated photoresponse enables a new range of applications for graphene-based photodetectors including, for example, pixilated infrared imaging with control of response on subwavelength dimensions. MANUSCRIPT TEXTGraphene is a promising photonic material 1 whose gapless band structure allows electron-hole pairs to be generated over a broad range of wavelengths, from UV, visible 2 , and telecommunication bands, to IR and THz frequencies 3 . Previous studies of photocurrents in graphene have demonstrated photoresponse near metallic contacts [4][5][6][7] , at the interface between single-layer and bilayer regions 8 , or at the edge of chemically doped regions 10 . Photocurrents generated near metal contacts were attributed to electric fields in the graphene that arise from band bending near the contacts 5-7 , and could be modulated by sweeping a global back-gate voltage with the potential of the contacts fixed. In these studies, photocurrent away from contacts and interfaces was typically very weak. In contrast, the present study concerns devices with top gates, separated from otherwise homogeneous graphene by an insulator, Al2O3, deposited by atomic layer deposition (ALD). When the top gate inverts the carrier type under the gate, a p-n junction is formed at the gate edges, and a highly localized photocurrent is observed using a 1 * These authors contributed equally to this work. focussed scanning laser. A density difference induced by the top gate that does not create a p-n junction does not create local photosensitivity.Comparing experimental results to theory suggests that the photocurrent generated at the p-n interface results from a combination of direct photogeneration of electron-hole pairs in a potential gradient, and a photothermoelectric effect in which electric fields result from optically induced temperature gradients 8,11 . Both effects are strongly enhanced at p-n interfaces: The enhancement of direct photocurrent results from its scaling inversely with local conductivity, while the thermoelectric contribution is enhanced by the strong spatial dependence of the Seebeck coefficient near the p-n interface. As neither mechanism is wavelength selective, the overall effect should provide broadband photosensitivity. We further anticipate that the ability to activate local photosensitive regions using gate voltages will provide pixel-controlled bolometers for imaging or spectroscopy with broadband sensitivity and subwavelength spatial resolution.A typical device layout and micrograph are shown in Fig. 1. Graphene was deposited onto ~300 nm of silicon dioxide on degenerately doped silicon by mechanical exfoliat...

An efficient and mature inkjet printing technology is introduced for mass production of coffee-ring-free patterns of high-quality graphene at high resolution (unmarked scale bars are 100 μm). Typically, several passes of printing and a simple baking allow fabricating a variety of good-performance electronic devices, including transparent conductors, embedded resistors, thin film transistors, and micro-supercapacitors.

Resistive switching (RS) is an interesting property shown by some materials systems that, especially during the last decade, has gained a lot of interest for the fabrication of electronic devices, with electronic nonvolatile memories being those that have received the most attention. The presence and quality of the RS phenomenon in a materials system can be studied using different prototype cells, performing different experiments, displaying different figures of merit, and developing different computational analyses. Therefore, the real usefulness and impact of the findings presented in each study for the RS technology will be also different. This manuscript describes the most recommendable methodologies for the fabrication, characterization, and simulation of RS devices, as well as the proper methods to display the data obtained. The idea is to help the scientific community to evaluate the real usefulness and impact of an RS study for the development of RS technology.

Layered two-dimensional (2D) materials display great potential for a range of applications, particularly in electronics. We report the large-scale synthesis of thin films of platinum diselenide (PtSe), a thus far scarcely investigated transition metal dichalcogenide. Importantly, the synthesis by thermally assisted conversion is performed at 400 °C, representing a breakthrough for the direct integration of this material with silicon (Si) technology. Besides the thorough characterization of this 2D material, we demonstrate its promise for applications in high-performance gas sensing with extremely short response and recovery times observed due to the 2D nature of the films. Furthermore, we realized vertically stacked heterostructures of PtSe on Si which act as both photodiodes and photovoltaic cells. Thus, this study establishes PtSe as a potential candidate for next-generation sensors and (opto-)electronic devices, using fabrication protocols compatible with established Si technologies.

Monolayer graphene exhibits exceptional electronic and mechanical properties, making it a very promising material for nanoelectromechanical devices. Here, we conclusively demonstrate the piezoresistive effect in graphene in a nanoelectromechanical membrane configuration that provides direct electrical readout of pressure to strain transduction. This makes it highly relevant for an important class of nanoelectromechanical system (NEMS) transducers. This demonstration is consistent with our simulations and previously reported gauge factors and simulation values. The membrane in our experiment acts as a strain gauge independent of crystallographic orientation and allows for aggressive size scalability. When compared with conventional pressure sensors, the sensors have orders of magnitude higher sensitivity per unit area.

Using scanning tunneling microscopy in an ultrahigh vacuum and atomic force microscopy, we investigate the corrugation of graphene flakes deposited by exfoliation on a Si/SiO2 (300 nm) surface. While the corrugation on SiO2 is long range with a correlation length of about 25 nm, some of the graphene monolayers exhibit an additional corrugation with a preferential wavelength of about 15 nm. A detailed analysis shows that the long-range corrugation of the substrate is also visible on graphene, but with a reduced amplitude, leading to the conclusion that the graphene is partly freely suspended between hills of the substrate. Thus, the intrinsic rippling observed previously on artificially suspended graphene can exist as well, if graphene is deposited on SiO2.

We report nanoscale patterning of graphene using a helium ion microscope configured for lithography. Helium ion lithography is a direct-write lithography process, comparable to conventional focused ion beam patterning, with no resist or other material contacting the sample surface. In the present application, graphene samples on Si/SiO2 substrates are cut using helium ions, with computer controlled alignment, patterning, and exposure. Once suitable beam doses are determined, sharp edge profiles and clean etching are obtained, with little evident damage or doping to the sample. This technique provides fast lithography compatible with graphene, with approximately 15 nm feature sizes.