This Small Business Innovation Research (SBIR) Phase I project addresses the need for substrates for graphene films. Graphene is a unique two-dimensional material that has been called the ?miracle material? because of its extraordinary structural and electronic properties that can be used in many applications. However, graphene is a relatively new material and as such is still not reproducibly fabricated in large areas. Highly perfect epitaxial graphene films have been synthesized on single crystals via surface decomposition on silicon carbide and by chemical vapor deposition on catalytic metals such as copper. However ?epitaxial growth? where graphene atoms are in registry with the substrate is limited by the single-crystal substrate requirement. Electronic properties of graphene deposited on standard polycrystalline materials are not optimal due to grain mismatch in the substrate. In this project we utilize ion-beam assisted deposition technology to make single-crystal like coatings on a variety of surfaces such as glass and metal foils. We explore these artificially aligned films to produce large area substrates for deposition of epitaxial graphene. Such substrates would enable one to deposit high-performance epitaxial graphene on many different surfaces without the need for rigid single-crystal substrates.
The broader impact/commercial potential of this project is to provide a technology for large-area fabrication of high-quality graphene films. Graphene offers a singular combination of properties such as very high conductivity, optical transparency, and mechanical robustness, making it an excellent candidate for transparent electrodes in photovoltaics, displays, and other optoelectronic devices. However, what is still needed is a technology for providing large-area high-performance graphene on a variety of different surfaces. By providing a scalable method of ?crystal-aligned? film deposition, the ion-beam film aligning technology can in turn enable large-area epitaxial graphene films to be produced. These graphene films should approach the quality of those made on small single-crystal wafers. Use of such crystal-aligned templates has already been proven for epitaxial superconducting films that are used to manufacture high temperature superconductor wire in kilometer lengths.
Graphene is a single atomic sheet of graphite and it has only recently been recognized as a unique two-dimensional material. Graphene is a subject of intense materials research because of its fundamental science, but also because of its large potential for applications in electronics. However, graphene is a relatively new material and as such is still not fabricated reproducibly and in high quality in large areas. In this project we worked on developing a new process for fabrication of graphene in large area and at low cost. In the past highly perfect epitaxial graphene has been synthesized on single crystals via surface decomposition of silicon carbide and by chemical vapor deposition (CVD) on catalytic metals such as copper. The CVD graphene, widely regarded as most practical, still has to be transferred to dielectric surfaces for most applications. The transfer process requires multiple steps of chemical treatment in order to remove graphene from copper and place it on desired substrates. Many additional defects form during the transfer process, not to mention the difficulties in scaling up the process for large size sheets of graphene. Our company, iBeam Materials, practices an ion-beam assisted deposition (IBAD) technology to make single-crystal like coatings on arbitrary surfaces such as glass and metal foils. In this project we partnered with University of Kansas to explore epitaxial copper on IBAD substrates as a substrate for large area epitaxial deposition of graphene. In the process of doing this research we discovered a new way of depositing graphene that leaves graphene behind with no copper underneath the graphene. The copper layer evaporates during graphene deposition and leaves behind graphene.This new process eliminates the need for transferring the graphene from the substrate as it can be deposited directly on dielectric materials. The fundamental mechanisms of this process are still not completely understood and we are pursuing further research to understand it better. We believe that in this process graphene deposition is nucleating on the oxide material instead of the copper layer and that we are depositing bilayers of graphene. We measured electrical conductivity of this graphene and found it to be rather high, similar to that for typical graphene transferred from copper. Graphene offers a singular combination of properties such as very high conductivity, optical transparency, and mechanical robustness, making it an excellent candidate for transparent electrodes in photovoltaics, displays, and other optoelectronic devices. However, what is still needed is a technology for providing large-area high-performance graphene on a variety of different surfaces. By providing a scalable method of crystal-aligned film deposition, our IBAD technology can in turn enable large-area epitaxial graphene films to be produced. Our newly discovered process also enables deposition of graphene directly on insulating substrates such as ceramics or glass. iBeam Materials intends to pursue commercialization of this technology.
