Copper substrate for deposition of graphene

Abstract

Technologies are presented for growing graphene by chemical vapor deposition (CVD) on a high purity copper surface. The surface may be prepared by deposition of a high purity copper layer on a lower purity copper substrate using deposition processes such as sputtering, evaporation, electroplating, or CVD. The deposition of the high purity copper layer may be followed by a thermal treatment to facilitate grain growth. Use of the high purity copper layer in combination with the lower purity copper substrate may provide thermal expansion matching, compatibility with copper etch removal, or reduction of contamination, producing fewer graphene defects compared to direct deposition on a lower purity substrate at substantially less expense than deposition approaches using a high purity copper foil substrate.

What is claimed is: 
     
         1 . A copper substrate for growing a graphene monolayer, the copper substrate comprising:
 a first copper layer characterized by a first copper percentage by weight, a first oxygen percentage by weight, and a first average thickness; and   a second copper layer in contact with the first copper layer, wherein the second copper layer is characterized by a second copper percentage by weight, a second oxygen percentage by weight, and a second average thickness;   wherein:
 the second copper percentage is greater than the first copper percentage; 
 the second oxygen percentage is about the same or less than the first oxygen percentage; and 
 the second average thickness is less than the first average thickness. 
   
     
     
         2 . The copper substrate of  claim 1 , wherein the first average thickness is at least about 3 micrometers. 
     
     
         3 . The copper substrate of  claim 1 , wherein the second average thickness is one atomic monolayer of copper to about 25 micrometers. 
     
     
         4 . The copper substrate of  claim 1 , wherein the second copper percentage is greater than the first copper percentage by at least about 0.1%. 
     
     
         5 . The copper substrate of  claim 1 , wherein:
 the second copper percentage is at least about 99.9%,   the first copper percentage is less than about 99.9%, or   the second copper percentage is at least about 99.9% and the first copper percentage is less than about 99.9%.   
     
     
         6 . A system for manufacturing a copper substrate for growing graphene, the system comprising:
 a deposition chamber;   a sample stage configured to hold a copper substrate in the deposition chamber;   a copper deposition source;   a cleaning agent source configured to direct a cleaning agent to the copper substrate held by the sample stage;   a sensor configured to determine a thickness of a layer deposited by the copper deposition source;   a heater configured to heat the copper substrate held by the sample stage to an annealing temperature;   a gas source configured to provide a thermal annealing gas to the copper substrate held by the sample stage; and   a microprocessor coupled to the deposition chamber, the sample stage, the copper deposition source, the cleaning agent source, the sensor, and the beater, wherein the microprocessor is programmable to:
 employ the cleaning agent source to direct the cleaning agent to a first copper layer of the copper substrate held by the sample stage in the deposition chamber; 
 employ the copper deposition source and the sensor to deposit a second copper layer on the first copper layer, wherein the second copper layer is thinner compared to the first copper layer, and 
 employ the heater and the gas source to thermally anneal the first copper layer at the copper substrate. 
   
     
     
         7 . The system of  claim 6 , further comprising:
 a chemical vapor source that is configured to provide one or more chemical vapor deposition precursors for forming graphene, wherein the microprocessor is further programmable to: employ the chemical vapor source to grow a graphene monolayer at the second copper layer using the one or more chemical vapor deposition precursors for forming the graphene.   
     
     
         8 . The system of  claim 7 , wherein in a dimension perpendicular to the graphene monolayer, a first copper layer is further characterized by a first average thickness 
     
     
         9 . The system of  claim 8 , wherein the microprocessor is further programmable to:
 employ a copper deposition source and a sensor to deposit the second copper layer at a second average thickness that is less than the first average thickness.   
     
     
         10 . The system of  claim 6 , wherein the annealing temperature is about 800° C. to about 900° C. 
     
     
         11 . The system of  claim 6 , wherein the second copper layer is saturated in dissolved oxygen at the annealing temperature. 
     
     
         12 . The system of  claim 6 , wherein the second copper layer is deposited on a surface of the first copper layer by one or more of sputtering, evaporation, electroplating, or chemical vapor deposition (CVD). 
     
     
         13 . The system of  claim 6 , wherein the microprocessor is further programmable to:
 employ the heater and the gas source to thermally anneal the first copper layer in an atmosphere comprising:
 about 1 mole % hydrogen to about 10 mole % hydrogen; and 
 about 90 mole % to about 99 mole % of one or more noble gases. 
   
     
     
         14 . The system of  claim 6 , wherein the microprocessor is further programmable to:
 employ the heater and the gas source to thermally anneal the first copper layer in an atmosphere substantially free of oxygen.   
     
     
         15 . A graphene-copper composite, comprising:
 a first copper layer characterized by a first copper percentage by weight, a first oxygen percentage by weight, and a first average thickness;   a second copper layer having a first surface in contact with the first copper layer, wherein the second copper layer characterized by a second copper percentage by weight, a second oxygen percentage by weight, and a second average thickness; and   a graphene monolayer in contact with a second surface of the second copper layer, wherein:
 the second copper percentage is greater than the first copper percentage; 
 the second oxygen percentage is about the same or less than the first oxygen percentage; and 
 the second average thickness is less than the first average thickness. 
   
     
     
         16 . The graphene-copper composite of  claim 15 , wherein the first average thickness is at least about 3 micrometers. 
     
     
         17 . The graphene-copper composite of  claim 15 , wherein the second average thickness is one atomic monolayer of copper to about 25 micrometers. 
     
     
         18 . The graphene-copper composite of  claim 15 , wherein the second copper percentage is greater than the first copper percentage by at least about 0.1%. 
     
     
         19 . The graphene-copper composite of  claim 15 , wherein the first oxygen percentage by weight is about 0.001%. 
     
     
         20 . The graphene-copper composite of  claim 15 , wherein the second oxygen percentage by weight is about 0.0028%.