Aluminum gallium nitride (AlGaN/GaN)-based gas sensors can, e.g., detect car exhaust gases. If the material were modified for use in wearable sensors, portable air pollutant monitoring would be possible.

Abdallah Ougazzaden, CNRS and Georgia Institute of Technology, Metz, France, and colleagues have developed a technique for the transfer of such semiconductor-based gas sensors to low-cost flexible substrates. The team grew monolayers of hexagonal boron nitride (h-BN) as a sacrificial layer on sapphire wafers using a metal organic vapor phase epitaxy (MOVPE) process. Then, wafer-like AlGaN/GaN gas sensors were grown on top of the h-BN, also in an MOVPE process.

The boron nitride layer is only weakly connected to the other layers by van-der-Waals interactions. Due to the weak attachment of the sensors to the h-BN, the devices can easily be transferred from the sapphire wafers to other substrates, such as flexible polymers or metallic foils. This modifies the properties of the sensor and leads to significantly improved sensitivity and faster response times. According to the researchers, this approach is promising for the production of wearable and portable sensor devices.

• Gas sensors boosted by two-dimensional h-BN enabled transfer on thin substrate foils: towards wearable and portable applications,
  Taha Ayari, Chris Bishop, Matthew B. Jordan, Suresh Sundaram, Xin Li, Saiful Alam, Youssef ElGmili, Gilles Patriarche, Paul L. Voss, Jean Paul Salvestrini, Abdallah Ougazzaden,
  Sci. Rep. 2017.
  DOI: 10.1038/s41598-017-15065-6