Fujitsu Laboratories Ltd. announced the development of a novel sensitive gas-sensor based on a new principle that takes advantage of graphene, a material comprising one-atom-thick carbon atoms arranged in a sheet. The details of the novel sensor and the method used will be presented at the 2016 IEEE International Electron Devices Meeting, which opened on December 3 in San Francisco.
With this development, compact instruments can be designed to measure specific gas components with increased speed and sensitivity. The instruments can have potential applications in detecting atmospheric pollution and testing of organically-derived gases in human breath. These can detect lower than tens of parts per billion (ppb) concentration of specific compounds such as ammonia (NH3) and nitrogen dioxide (NO2) for which sensitivity has improved tenfold to less than 1 ppb. This sensitivity to NO2 is an order of magnitude greater than conventional resistivity-based graphene sensors for less than 1ppb concentrations, and also better than the tens of ppb sensitivity of commercial NO2 electrochemical sensors.
The pioneering gas sensor utilizes a novel principle wherein the gate part of a silicon transistor is replaced by graphene, enabling quicker real-time air quality measurements which otherwise may have taken tens of hours (depending on the gas being measured). In addition, it would become simpler to detect gas components in breath to help discover lifestyle diseases.
The prevalent silicon-based very-large-scale integration (VLSI) circuitry has started reaching its miniaturization limits. In contrast, graphene has unique electrical properties which have attracted attention for its application in next-generation electronic devices such as high-sensitivity sensors.
Moreover, performing extremely sensitive measurements is possible using specialized equipments like gas chromatographs, but these measurements take time and the equipment is bulky. In contrast, compact semiconductor gas sensors provide real time data, but their sensitivity is in the parts per million (ppm), which is not sufficient for detecting certain gas components. Sensors that utilize graphene currently work by detecting change in resistance across the graphene layers as a gas adheres to it, but this resistance only varies by significant percentage in the presence of 1ppm concentration, which is not the concentration level needed for practical applications.
In contrast, the novel gas sensor developed by Fujitsu Laboratories Ltd. employs a one-atom thick graphene sheet to replace the ‘gate’ of a conventional silicon transistor. When a gas molecule adheres to the graphene, it causes a change in the transistor’s switching characteristics, which can be used to detect the gas. The graphene returns to its original state once the gas molecule separates from it. The sensor based on this principle can be used to detect various gases in the air and human breath, and test results indicated that the sensor only reacted to NO2 and NH3 i.e. it can detect only specific gases.
The developed sensor is compact with a detection area of a few hundred micrometers, and can be made even smaller (less than 1 micrometer). Its sensitivity is better than existing technologies since it does not rely on chemical reactions, and returns to its original state by application of heat. Therefore, it has potential application in compact devices to measure NO2 in real time against the environmental benchmark of 40-60 ppb, which is an index of air pollution.
After testing the principle behind the graphene sensor, Fujitsu Laboratories aims to put it into practical use as an environmental sensor once its characteristics and durability are verified. The company is also experimenting with ways to detect gases other than nitrogen dioxide and ammonia by using a combination of graphene with other molecules.
Furthermore, by combining this novel sensor with a sensor announced in April 2016 that can measure ammonia with better sensitivity, the company plans to develop a highly sensitive portable sensor for use as a thermometer to measure gases in human breath for early detection of lifestyle diseases.
More information can be found at: Fujitsu Laboratories Ltd.