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Monolithically-integrated graphene structures as sensors

Graphene is a single, atomic-layer thick two-dimensional sheet of bonded carbon atoms that is characterized by superb electric and mechanical properties, thermal conductivity, and optical transparency. Graphene is a promising candidate material for post-silicon microfabrication due to its high carrier mobility. However, current graphene device manufacturing processes do not address the need to integrate the graphene layer with electrodes for fabricating a range of device components based on graphene materials, such as FETs and electrical interconnects.

This invention allows for the single-step chemical vapor deposition (CVD) graphene synthesis process to build monolithically-integrated electronic devices with structures and regions of varying numbers of graphene layers to produce a range of elements, including graphene channels and graphite electrodes. The single-step synthesis technique also enables the production of an entire device area, including interconnect lines, in a single step and the assembly of multiple components of FETs on flexible and transparent plastic films (Figure 1). In contrast to the multiple processing steps required in conventional complementary metaloxide- semiconductor (CMOS) microfabrication, this single-step process allows for the synthesis and integration of complex graphene devices, such as the fabrication of flexible semitransparent graphene FET arrays, graphene biosensors, and pH sensor arrays. For example, this invention allows for the straightforward fabrication of single or arrays of the protein biosensors illustrated in Figure 2.



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Figure 1: Flexible and semitransparent topgate monolithic graphene FET arrays. (A) Schematic illustration of the device layout. (B) Photograph (main panel) of the devices wrapped on a cylindrical glass (radius of curvature: 1.2 cm). The device rested on a paper printed with a logo, to show the semitransparent property of the monolithic graphene devices (left inset). Scale bars, 4 mm. Optical micrograph of the topgate FET arrays (right image, scale bar, 200 μm). A blue arrow presents the gate line, and a red arrow indicates the part with S/D, channel and interconnects.


Figure 2: Diagram of graphene FET biosensor with antibody receptors to sense to presence of specific proteins.

Intellectual Property Status: Patent(s) Pending

Applications

Carbon graphene structures may revolutionize the field of post-silicon electronics. However, a number of technical limitations prevent the advancement and widespread adoption of graphene nanolayer devices and components. The technology described here solves a number of those challenges by allowing for a single-step synthesis of a large number of monolithic graphene structures as well as the integration of graphene components with other circuit components made from carbon. This technology allows for the creation of a whole new class of graphene-based components and circuits. For example, the multilayer graphene structures synthesized with this technology can be transferred onto both rigid and flexible substrates, such as transparent plastic films, enabling a wide range of applications (see Figure 1).

The single-step synthesis process allows for the creation of a range of devices, including sensors. For example, this technology can be used to create a monolithic graphene/graphite field-effect transistor (FET) device array that allows for real-time, multiplexed sensing, such as voltage, pH and, with the proper functionalization, sensing of biomolecules. An example FET biosensor is a macromolecule protein sensor with antibody receptors linked to the sensor’s graphene layer as shown in Figure 2. This micro-scale sensor allows for the detection of minute amounts of specific proteins in solution for a large range of medical, drug development, and safety inspection applications.

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