Graphene-semiconductor based wavelength selective photodetector for sub-bandgap photo detection
Graphene photodetectors capable of operating in the sub-bandgap region relative to the bandgap of semiconductor nanoparticles, as well as methods of manufacturing the same, are provided. A photodetector can include a layer of graphene, a layer of semiconductor nanoparticles, a dielectric layer, a supporting medium, and a packaging layer. The semiconductor nanoparticles can be semiconductors with bandgaps larger than the energy of photons meant to be detected.
1. A method of manufacturing a graphene semiconductor photodetector, the method comprising:
providing a monolayer chemical vapor deposition (“CVD”) of graphene on a metal;
spin-coating a poly(methyl methacrylate) (PMMA) solution in anisole onto the graphene layer and air drying it;
removing the metal on the reverse side of the graphene by etching;
separating the released graphene on PMMA film and rinsing the film consecutively in a plurality of clean deionized (“DI”) water baths;
placing the film onto a clean substrate and air drying it;
dissolving the PMMA with a solvent;
patterning the graphene into a ribbon with e-beam lithography and oxygen;
depositing silver (Ag) in a thermal evaporator on the e-beam lithography in a defined central area of the graphene ribbon;
transforming the Ag into one of AgCl, AgBr, and AgI by a reaction with Cl 2 , Br 2 , or I 2 , respectively;
after the transformation of the Ag, coating Al 2 O 3 by atomic layer deposition (ALD) onto the structure;
removing the Al 2 O 3 on the contact area by dipping it in a buffered HF solution (BHF), and patterning a nickel (Ni) electrode on the graphene ribbon with e-beam lithography followed by metal sputtering; and
cleaning the PMMA.
2. The method of claim 1 wherein the step of spin-coating is carried out at 4,000 rpm for 1 minute with a 7 wt. % PMMA solution.
3. The method of claim 1 wherein the step of removing the metal on the reverse side of the graphene by etching is carried out with an oxygen reactive ion etching (RIE) for 2 minutes and then etching overnight in 0.1 M (NH 4 ) 2 S 2 O 8 aqueous solution.
4. The method of claim 1 wherein the substrate upon which the film is placed is one or more of a clean silicon substrate with 470 nm or 200 nm thermal oxide, quartz, or polyethylene terephthalate (PET) film.
5. The method of claim 1 , wherein the Ag is deposited to a thickness of at least 0.5 nm.
6. The method of claim 1 , wherein the step of dissolving PMMA is carried out with a mixture of dichloroethene and acetone.
7. The method of claim 1 , wherein the step of transforming the Ag comprises transforming the Ag into AgCl by a reaction with Cl 2 via the following steps:
covering a sample substrate with a layer of silica gel and placing it in a sealed vial with solid KClO 3 ;
adding an HCl solution to the solid so the Cl 2 is generated in-situ (KClO 3 +6HCl=KCl+5Cl 2 +3H 2 O); and
allowing it to react with evaporated Ag nanoparticles.
8. The method of claim 1 , wherein the step of transforming the Ag comprises transforming the Ag into AgBr by a reaction with Br 2 via the following steps:
covering a sample substrate with a layer of silica gel and placing it in a sealed vial with solid KBr;
adding solid KMnO 4 and H 2 SO 4 mixture solution to the solid so a Br 2 vapor is produced by the reaction (2KMnO 4 +8H 2 SO 4 +10KBr=6K 2 SO 4 +5Br 2 +2MnSO 4 +8H 2 O); and
allowing it to react with Ag nanoparticle.
9. The method of claim 1 wherein the step of transforming the Ag comprises transforming the Ag into AgI by a reaction with I 2 via the following steps:
placing a sample substrate in a sealed vial containing I 2 solid; and
heating the reaction vial to allow the I 2 vapor to react with Ag nanoparticle.
10. The method of claim 1 , wherein the step of coating Al 2 O 3 comprises utilizing trimethylaluminum as a precursor.
11. The method of claim 1 , wherein the metal is copper, wherein the solvent is acetone, and wherein cleaning the PMMA comprises cleaning the PMMA with a mixture of dichloroethene and acetone.