Ultra-compact, passive, wireless sensor using quantum capacitance effect in graphene

Abstract

An electrical device includes at least one graphene quantum capacitance varactor. In some examples, the graphene quantum capacitance varactor includes an insulator layer, a graphene layer disposed on the insulator layer, a dielectric layer disposed on the graphene layer, a gate electrode formed on the dielectric layer, and at least one contact electrode disposed on the graphene layer and making electrical contact with the graphene layer. In other examples, the graphene quantum capacitance varactor includes an insulator layer, a gate electrode recessed in the insulator layer, a dielectric layer formed on the gate electrode, a graphene layer formed on the dielectric layer, wherein the graphene layer comprises an exposed surface opposite the dielectric layer, and at least one contact electrode formed on the graphene layer and making electrical contact with the graphene layer.

1 - 20 . (canceled) 
     
     
         21 . A method of sensing chemical compounds in a sample comprising:
 exposing the sample to a graphene sensor element;   applying a DC gate voltage to the graphene sensor element; and   measuring capacitance of the graphene sensor element;   wherein the graphene sensor element comprises:
 a graphene layer. 
   
     
     
         22 . The method of  claim 21 , further comprising applying a DC gate voltage to the graphene sensor element across a range of gate voltages. 
     
     
         23 . The method of  claim 21 , wherein the sample is a biological sample. 
     
     
         24 . The method of  claim 21 , wherein the graphene sensor element further comprises a dielectric layer under the graphene layer. 
     
     
         25 . The method of  claim 24 , wherein the graphene sensor element further comprises an insulator layer under the dielectric layer. 
     
     
         26 . The method of  claim 25 , wherein the graphene sensor element further comprises a gate electrode between the insulator layer and the dielectric layer, wherein the gate electrode is a multi-finger structure comprising at least two gate electrode fingers. 
     
     
         27 . The method of  claim 21 , wherein capacitance of the graphene layer changes in response to collection of electrons in the graphene layer upon exposure to the sample. 
     
     
         28 . The method of  claim 21 , wherein the graphene sensor element is a graphene quantum capacitance varactor. 
     
     
         29 . The method of  claim 21 , further comprising contacting a readout circuit with the graphene sensor element. 
     
     
         30 . The method of  claim 21 , wherein the graphene sensor element has a capacitance modulation ratio of greater than about 1.2. 
     
     
         31 . A medical sensor comprising:
 a sensor element comprising a graphene layer; and   a layer a molecules attached to the grapheme layer via pi-pi interactions,   wherein capacitance of the sensor element changes in response to exposure of the sensor element to a sample.   
     
     
         32 . The medical sensor of  claim 31 , wherein the graphene sensor element further comprises a dielectric layer under the graphene layer. 
     
     
         33 . The medical sensor of  claim 32 , wherein the graphene sensor element further comprises an insulator layer under the dielectric layer. 
     
     
         34 . The medical sensor of  claim 33 , wherein the graphene sensor element further comprises a gate electrode between the insulator layer and the dielectric layer, wherein the gate electrode is a multi-finger structure comprising at least two gate electrode fingers. 
     
     
         35 . The medical sensor of  claim 31 , wherein capacitance of the graphene layer changes in response to collection of electrons in the graphene layer upon exposure to the sample. 
     
     
         36 . The medical sensor of  claim 31 , wherein the graphene sensor element is a graphene quantum capacitance varactor. 
     
     
         37 . The medical sensor of  claim 31 , further comprising a readout circuit responsive to the capacitance of the graphene layer and configured to output a signal indicative of the electrical charge. 
     
     
         38 . The medical sensor of  claim 31 , wherein the sensor element has an equivalent oxide thickness (EOT) of less than about 5 nanometers (nm). 
     
     
         39 . The medical sensor of  claim 31 , wherein the sensor element has a capacitance modulation ratio of greater than about 1.2. 
     
     
         40 . The medical sensor of  claim 31 , wherein molecules of the layer of molecules comprise a pyrene group.