Dutch scientists found a way to create and clean tiny mechanical sensors in a scalable manner. These sensors suspending a two-dimensional sheet of hexagonal boron nitride (h-BN), or ‘white graphene’ over small holes in a silicon substrate. This innovation could lead to extremely small gas and pressure sensors for future electronics.
White graphene is an interesting material with a honeycomb lattice structure similar to that of graphite. While, graphite conducts electricity acts as an insulator. This property makes h-BN popular as a high-end lubricant, especially in industrial applications where electrical conductivity is undesirable. Since, h-BN has the added benefit of being chemically and thermally more stable than graphite. h-BN is also used in harsh environments such as space in deep ultraviolet applications. Many researchers have been able to study the properties of h-BN as a 2-D material until now.
Through a series of steps, researchers using a technique chemical vapour deposition to transfer the sheet of transparent white graphene onto a silicon substrate containing tiny circular cavities. By doing, they created microscopic drums. These drums function as mechanical resonators and used as infinitesimal gas or pressure sensors, for instance in mobile phones.
As a result of the steps, researchers transfer monoatomic sheet onto the silicon substrate, the drums were contaminated with a number of polymers. Common contaminations such as change the properties of the sensors. The result is that all of the sensors may behave slightly differently. “In order to outperform the normal sensors in the market, it is important that all 2-D sensors behave in exactly the same way.
Using ozone gas to clean the drums. The aggressive gas removed all of the organic polymers. However, traces of PMMA, a polymer with inorganic components left behind on resonators. Researchers say, this problem solved by using organic substrates while transferring the sheet of white graphite onto the cavities. The Delft researchers provided proof of principle for the fabrication of incredibly small sensors for future electronics.
More information: [nature]