Exploring gas sensing properties of organic semiconductor gas sensor device

• Main Author: Lee, Ming Xuan
• Other Authors: Lee Pooi See
• Format: Final Year Project
• Language: English
• Published: 2014
• Subjects: DRNTU::Engineering::Materials::Material testing and characterization; DRNTU::Engineering::Materials::Microelectronics and semiconductor materials::Thin films
• Online Access: http://hdl.handle.net/10356/55718
• Institution: Nanyang Technological University

Due to increasing concerns for air pollution, monitoring of toxic gases and vapors has become increasing important as well. There are many types of sensors currently available however researchers are still look for ways to produce cheap and yet effective sensors to meet the demands. One type of electronic sensors is known as the “chemiresistors”. This type of sensor uses resistance change in the device to measure the concentration of gas when a film of chemically reactive materials in the device interacts with the gas. Although there are many types of materials used, in this project we will be focusing on polymers as they are considered the cheaper alternative and also has the added flexibility to be tailored for different properties. The three polymers explored in this project are polyaniline, polypyrrole and copper phthalocyanine as they are found to be the more stable materials in atmosphere. Furthermore, they are also readily available and synthesized. Nitrogen dioxide (NO2) was used to test the gas sensor devices because it is a commonly found toxic gas in the environment and also because of its oxidizing nature. Spin-coating was the main method used in fabrication of the thin films as it is the simplest method available. The film were slightly altered to adjust properties like thickness, porosity and even grain structure to explore how they would affect the sensing properties of the devices. SEM and the surface profiler were then used to analyse the physical properties of the film prior to the testing of the devices with NO2. The physical morphology and also changes in conductivity of the polymer films were then used to explain the gas sensitivity of the film and also the response and recovery time of the film as well.