Grow graphene for electronics the bio-inspired way
Graphene, as many would confirm, has the potential to be used in a number of applications. However, the main challenge for the material is its production targeted for high-end electronics such as touch screens. In light of this, a research team from the National University of Singapore (NUS) has developed a method that allows both the growth and transfer steps of graphene on a silicon wafer, allowing the material to be applied in photonics and electronics, for devices such as optoelectronic modulators, transistors, on-chip biosensors and tunnelling barriers.
According to the researchers, the results of the study have been inspired by how beetles and tree frogs keep their feet attached to submerged leaves.
Gao (left) and research assistant Lim Xiao Fen working on the wafer-scale graphene growth and transfer in the Graphene Research Centre's clean room
Loh Kian Ping, head of the NUS department of chemistry, led a team to come up with the one-step method to grow and transfer high-quality graphene on silicon and other stiff substrates. This promises the use of graphene in high-value areas where no technique currently exists to grow and transfer graphene with minimal defects for use in semiconductors.
Loh, who is also a principal investigator with the Graphene Research Center at NUS Faculty of Science, explained: "Although there are many potential applications for flexible graphene, it must be remembered that to date, most semiconductors operate on "stiff" substrates such as silicon and quartz." Thus, a transfer method with the direct growth of graphene film on silicon wafer is needed for enabling multiple optoelectronic applications, he added.
In the process called "face-to-face transfer", Gao Libo, the first author who is with the Graphene Research Center, grew graphene on a copper catalyst layer coating a silicon substrate. After growth, the copper is etched away while the graphene is held in place by bubbles that form capillary bridges, similar to those seen around the feet of beetles and tree frogs attached to submerged leaves. The capillary bridges help to attach the graphene to the silicon surface and prevent its delamination during the etching of the copper catalyst.
The technique can potentially be deployed in batch-processed semiconductor production lines such as the fabrication of large-scale integrated circuits on silicon wafers. The researchers will be fine-tuning the process to optimize the high throughput production of large diameter graphene on silicon, as well as target specific graphene-enabled applications on silicon. They are also looking at applying the techniques to other 2D films.
Researchers who developed the "face-to-face transfer" technique: (from left) Loh, Lim, Gao and Antonio Castro Neto, Director of the Graphene Research Center