New electronic devices such as touch screens, flexible displays, printable electronics, photovoltaics or solid-state lighting have led to a rapid increase in the market growth of flexible, transparent electrical conductors. Our readers already know that ITO (indium tin oxide) has long since ceased to be a solution. Also, that the demand for graphene as an ITO substitute has risen sharply in recent years. Recent advances in the synthesis and characterization of graphene show that it is interesting for many electronic applications as a transparent conductor.
Graphene Production Methods
Because graphene has proven to be useful in this area, more and more scalable possibilities of a high-quality and at the same time inexpensive production method are being sought. The following table lists the most important synthesis methods for graphene to date.
| Synthesis method | Principle |
|---|---|
| Mechanical exfoliation | With the help of an adhesive film, peel off the top layer of a graphite crystal and transfer it to a suitable carrier |
| Chemical Exfoliation | By intercalation of suitable reagents between individual layers of a graphite crystal, graphene flakes are obtained in solution with the help of ultrasonic treatment |
| Reduction of graphene oxide | Exfoliation of graphite oxide in water to graphene oxide, followed by chemical reduction to remove oxygenated groups |
| Epitaxial growth on silicon carbide | Thermal decomposition of a silicon carbide crystal at approx. 1000 degrees C. |
| Mixed Gas Phase Isolation (CVD) | Catalytic decomposition of a gaseous carbon source (e.g. methane) to graphene monolayers on a metallic support (Cu or Ni) |
CVD Graphene
By the way, CVD (chemical vapour deposition) is one of the most interesting methods of graphene synthesis (see table below) because it produces almost perfect graphene.
| Graphene Material | Electr. Factor | Transparency |
|---|---|---|
| CVD-G | 280 Ω/sq.m. | 80% |
| CVD-G | 350 Ω/sq | 90% |
| CVD-G | 700 Ω/sq | 80% |
With this synthesis method, the resulting transparency with low electrical resistance was quite high (80%).
