GB2485559A

GB2485559A - Graphene based electronic device

Info

Publication number: GB2485559A
Application number: GB1019493.4A
Authority: GB
Inventors: Genhua Pan
Original assignee: Plymouth University
Current assignee: Plymouth University
Priority date: 2010-11-18
Filing date: 2010-11-18
Publication date: 2012-05-23
Also published as: GB201019493D0

Abstract

A graphene based electronic device comprises an array of graphene elements 14, a series of gate electrodes 20, and a series of pairs of source 16 and drain 18 electrodes angled to the gate electrodes such that each graphene element can be addressed individually by appropriate selection of one of the gate electrodes and one of the pairs of source and drain electrodes. The graphene elements may be flakes of graphene or formed from an etched graphene sheet. Probe molecules may be attached to the graphene such that the device acts as an array of FET transistor biosensors.

Description

I

Graphene based Electronic Device This invention relates to an electronic device, and in particular to an electronic device incorporating an array of graphene elements. The device is intended principally as a biosensor, but it may be possible to use it in other applications.

Graphene is a one-atomic layer thick sheet of carbon atoms, the atoms of which are closely packed into a honeycomb like formation. It has been found that graphene has a number of unusual properties, one of which is that is can act as a semiconductor if treated appropriately. Mohanty and Berry (Nano letters 2008, Vol 8, no 12, 4469-4476) describe the use of graphene in a biosensor. In that arrangement, a flake of graphene is applied to a silica layer provided upon a silicon substrate. A probe biomolecule is attached to the graphene flake in such a manner that interactions between the probe biomolecule and a target biomolecule cause variations in the electrical conductivity of the graphene flake. By monitoring the electrical conductivity of the graphene flake, an output indicative of the form or nature of the target biomolecule may be achieved. F Whilst such a device may operate successfully, in practice it is of little commercial benefit as fabrication is impractical and as only a single device is provided, throughput of data is very low.

It is an object of the invention to provide a graphene based electronic device in which at least some of the disadvantages associated with such a known arrangement are overcome or are of reduced effect.

According to the present invention there is provided a graphene based electronic device comprising an array of graphene elements, a series of gate electrodes, each gate electrode being associated with a plurality of the graphene elements, and a series of pairs of source and drain electrodes each being electrically connected to a plurality of graphene elements, the source and drain electrodes being angled to the gate electrodes such that each graphene element can be addressed individually by appropriate selection of one of the gate electrodes and one of the pairs of source and drain electrodes The array of graphene elements may comprise a plurality of graphene flakes.

Alternatively, a single graphene sheet or layer may be etched or otherwise treated to define the separate elements.

By providing a plurality of separate graphene elements each of which can be addressed individually, it will be appreciated that a commercially viable electronic device may be provided. Such a device may be suitable for mass production and may be used in applications in which a high throughput of data is required.

Each graphene element of the array, together with the associated addressing electrodes, may serve as a biosensor, for example functioning in a manner similar to that described in the above mentioned Mohanty and Berry paper, or in DNA or biomolecule-based electronics applications. Alternatively, the graphene elements could serve a range of other functions, for example as transistors, sensors or other devices. One possibility may be to use the device in spin transistor arrays, for example in which the source and drain electrodes are of MgO or a ferromagnetio material instead of, for example, copper. Such a device could be used in spintronics (spin based electronics) applications, computer memories or the like.

Where used as a biosensor, each graphene element has attached thereto or associated therewith a probe biomolecule, and means are provided to permit monitoring of the conductivity of the graphene element, by monitoring, for example, the electrical resistance between the associated source and drain electrodes when a potential is applied to the associated gate electrode.

Conveniently, the graphene elements are mounted upon a Silicon oxide layer beneath which the gate electrodes are provided in the form of a series of parallel strips, each of which is aligned with a row of the graphene elements provided on a substrate of, for example, silicon The gate electrodes are conveniently perpendicular to the source and drain electrodes However, this need not always be the case and arrangements where they are otherwise angled relative to one another are possible The invention will further be described, by way of example with reference to the accompanying drawing, Figure 1, which is a diagrammatic illustration of part of a device in accordance with one embodiment of the invention Referring to Figure 1, an electronic device in accordance with one embodiment of the invention is illustrated. The device comprises a silicon substrate 10 on which a silicon oxide layer 12 is provided. A series of graphene elements 14 are provided upon the silicon oxide layer 12. In the arrangement illustrated the elements 14 take the form of graphene flakes which are formed and placed in position separately. However, other envisaged arrangements involve growing or otherwise forming a sheet of graphene which can be secured or otherwise positioned upon the silicon oxide layer 12, or indeed it may be possible for it to be grown or formed in position upon the layer 12, and then etching, for example using a photolithography technique, or otherwise applying a pattern to the graphene layer to form it into the separate elements 14.

A series of pairs of parallel, elongate source and drain electrodes 16, 18 are applied to the silicon oxide layer 12 adjacent the graphene elements 14, and a series of gate electrodes 20 are formed in or on the silicon substrate 10 beneath the silicon oxide layer 12.

With such an arrangement, each individual graphene element 14 can be uniquely addressed by using the pair of source and drain electrodes 16, 18 associated therewith in combination with the gate electrode 20 associated therewith. Provided only a single graphene element 14 is to be addressed at any given time, such an arrangement permits unique, individual addressing of each graphene element 14 without requiring the provision of separate electrodes for each element 14, and thus permits fabrication of the device in a relatively simple and convenient form.

In the arrangement described herein before, each graphene element 14 is treated so as to take the form of a semiconductor and would serve effectively, as a transistor or switch, the application of a potential to the gate electrode 20. determining whether or not a current is able to pass between the source and drain electrodes 16, 18 associated with that graphene element 14 Such an arrangement is advantageous compared to existing transistor arrangements as graphene when in a conductive mode, is of high conductivity at room temperature and so the transistor so formed would be of a very fast acting form One alternative possibility may be to use the device in spin transistor arrays for example in which the source and drain electrodes are of MgO or a ferromagnetic material instead of, for example, copper Such a device could be used in spintronics (spin based electronics) applications, computer memories or the like.

It is envisaged that, rather than simply taking the form of an array of transistors, the electronic device of the invention may serve as a biosensor array. In order to achieve this, each graphene element 14 of the array has associated therewith or attached thereto a probe biomolecule. The probe biomolecules may take the form of, for example, DNA, ATP, proteins or the like. In use the device is exposed to target F biomolecules which are able to hybridize with the probe molecules. Chimerical affinity between the target and probe biomolecules will affect the conductance of the associated graphene elements 14 by causing a change in the electron mobility across the graphene element 14 between the source and drain electrodes 16, 18. It will be appreciated, therefore, that by applying a potential to a selected one of the gate electrodes 20, and monitoring the electrical resistance between the associated pair of source and drain electrodes 16, 18, the nature or form of the target biomolecule can be studied. The manner in which the electrical resistance is monitored may involve, for example, applying a known voltage across the source and drain electrodes 16, 18 and measuring the current flowing therein. However, other techniques may be used to measure this characteristic without departing from the scope of the invention.

In use, therefore each conductivity of each individual graphene element 14 may be measured by applying a potential to the gate electrode associated with that element and by measuring the electrical resistance between the source and drain electrodes 16, 18 associated with that graphene element 14 Despite the source and drain electrodes 16, 18 being associated with several elements 14, the sensed characteristic will be representative only of the resistance or conductivity or changes therein, of the F graphene element 14 associated with the chosen gate electrode 20 the other graphene elements 14 associated with the selected pair of source and drain electrodes 16, 18 being substantially non-conductive as a result of the absence of an applied potential to the gate electrodes associated with those elements 14 Measurement of the resistance or conductivity of each of the graphene elements 14 can thus be achieved quickly, simply by addressing each of the elements 14 in turn and making the appropriate electrical measurements Such a device is advantageous, as outlined hereinbefore, as it is commercially viable, being capable of large scale manufacture, and in that a rapid or high throughput of measurements can be made, allowing it to be used in a wide range of applications. It is of label-free nature, of very high sensitivity and low noise, and as it is in the form of an electronic device, is convenient to use.

By way of example, the biosensor described hereinbefore may be used in a wide range of biomedical, medical diagnosis, healthcare and ICT for healthcare applications using label-free biosensing. Alternative uses of the technology may be in DNA or biomolecule-based electronics applications.

It will be appreciated that the arrangement described hereinbefore constitutes only a single embodiment of the invention and that a wide range of modifications and alterations may be made thereto without departing from the scope of the invention.