Modified bubbling transfer method for graphene delamination

Abstract

In the BB transfer, or so called electrochemical delamination process, a transfer film is firstly spray-coated on a stack formed by two graphene sandwiching a metal (Cu or Cr) foil as a protection layer. Then, direct current (dc) voltage is applied to the first stack as a cathode and an anode (from be a platinum wire, a carbon rod, or others) in an electrolyte aqueous solution. With application of the electrolysis potential, hydrogen bubbles appear at the graphene/metal foil interfaces, while oxygen bubble appear at the anode due to the reduction of water. These H 2 bubbles provide a gentle but persistent force to detach the graphene film from the copper foil at its edges, and the process is aided by the permeation of the electrolyte solution into the interlayers as the edges delaminate.

What is claimed is: 
     
         1 . A modified bubbling transfer method for graphene delamination comprising the steps of
 preparing the electrolyte solution for water electrolysis, pre-coating a transfer film on the upper graphene film of a first stack of an upper graphene film, a metal foil and a lower graphene film and connect with conducting wire to serve as a positive electrode,   preparing a negative electrode;   locating the positive and negative electrodes in the electrolyte solution and connecting to a DC power supply;   locating a non conductive transfer cloth between the two electrodes for separating the two electrodes;   switching on the DC power supply to begin the electrochemical delamination process, a second stack formed by the transfer film and the upper graphene film gradually separating from the metal foil;   lifting the second stack of the transfer film and the upper graphene film from the metal foil with the transfer cloth and the negative electrode being parallel as close as they could be, and the transfer cloth gradually attaching to a bottom of the first graphene film which is separated from the metal foil and an exposed upper surface of the metal foil;   dipping the lift up the third stack formed by the transfer film, the first graphene film and the transfer cloth into de-ionized water to remove electrolyte residue on the surfaces of the third stack, and   drying the third stack to remove de-ionized water thereon for final package.   
     
     
         2 . The modified bubbling transfer method for graphene delamination as claimed in  claim 1 , wherein a voltage between the two electrodes being controlled within 20V with current density within 1A/square inch. 
     
     
         3 . The modified bubbling transfer method for graphene delamination as claimed in  claim 1 , wherein the metal foil is a copper foil or a Cr foil. 
     
     
         4 . The modified bubbling transfer method for graphene delamination as claimed in  claim 1 , wherein the transfer film is selected from a group containing nitrocellulose lacquer, polyurethane, PMMA, epoxy, and other ketone removable polymer coatings. 
     
     
         5 . The modified bubbling transfer method for graphene delamination as claimed in  claim 1 , wherein the electrolyte is a 0.05 mM to 0.1 M water solution of K 2 SO 4 , K 2 S 2 O 8 , or NaOH, or other water solvable salt. 
     
     
         6 . The modified bubbling transfer method for graphene delamination as claimed in  claim 1 , wherein the electrolysis voltage is adjusted between 2 and 16 Volts. 
     
     
         7 . The modified bubbling transfer method for graphene delamination as claimed in  claim 1 , wherein with predetermined proper transfer film, electrolyte solvent content, electrolysis current density, the detach speed was adjusted for different size of the graphene films. 
     
     
         8 . The modified bubbling transfer method for graphene delamination as claimed in  claim 1 , wherein a distance between the negative electrode and a delaminating Cu (Cr) interface between the metal foil and the second stack as positive electrode, decides the delaminating speed; the closer the distance, the faster the delamination could be 
     
     
         9 . The modified bubbling transfer method for graphene delamination as claimed in  claim 1 , wherein the negative electrode is a platinum wire or a carbon rod. 
     
     
         10 . The modified bubbling transfer method for graphene delamination as claimed in  claim 1 , wherein ultrasonic treatment could be applied the BB transfer set-up for remove the new generated bubble and aid the delamination process without cause graphene loss or film break.