Phosphorus doping of graphene for conductometric room temperature ammonia sensing

The ammonia (NH3)-sensing performance of phosphorus-doped graphene sensors is systematically investigated in this paper. Using a chemical vapor deposition (CVD) system, phosphorus pentoxide was used as the phosphorus source to achieve stable phosphorus doping of graphene at 480 oC. The NH3-sensing test results showed that the NH3 response of phosphorus-doped graphene increased by 2.4 times on average, the response (recovery) time shortened by 70.6% (73.4%) on average, and the theoretical limit of detection (LOD) was 68.76 ppb. In addition, the phosphorus-doped graphene sensor also exhibits excellent repeatability, stability, and ultra-high selectivity to NH3. XPS, EDS, and FTIR analysis show that the P-O groups introduced on graphene are the key to improving the NH3 sensitivity of graphene. The P-O groups provide sufficient O atoms to assist graphene to adsorb NH3 molecules, thereby improving the NH3 sensitivity of graphene. A simple, large-scale implementable, and effective phosphorus doping by the CVD method was proposed to improve the NH3 sensitivity of graphene in this work, which is of great significance for promoting the practical application of graphene gas sensors.