UC Berkeley

Gas detection has wide-ranging applications, from industrial process control and greenhouse gas monitoring to disease diagnosis and pollution tracking, which are vital to support out civil life in many respects. To meet the needs of these applications, gas sensor technologies should enable scalable production and high performance. The current dominant technology is the micro-hotplate-based resistive ceramic sensor which suffers from high power consumption and poor selectivity. One of promising sensor technology, the chemical-sensitive field-effect transistors (CS-FET) have the advantage of miniature size, low-power consumption, and scalability. In order to improve the applicability of CS-FET sensors for real-world scenario, it is imperative to solve the problem of its response to ambient humidity. This can be achieved using integrated microheaters to locally heat the sensor, and evaporate the adsorbed water molecules.Another challenge for CS-FET devices is they cannot be made sensitive to gases such as methane, CO2, etc. at room temperature. Optical gas sensors are useful for these applications because their sensing mode does not depend on the interaction of the gas with the active material. However, optical sensors need high-performance infrared light emitters to detect gases at low concentrations. Black phosphorus (bP) has proven its ability to outperform the state-of-the-art compound semiconductors with its high photoluminescence quantum yield. Non-dispersive infrared (NDIR) gas sensors with LEDs based on bP are documented which can detect trace concentrations of greenhouse gases. However, optoelectronics based on bP have scalability issues due to its current deposition and processing methods. An ink-based approach to make uniform bP films by spin-coating has been demonstrated, which is then used to fabricate LEDs and photodetectors with high performance.