In recent years, the use of non-silicon thermal infrared detectors for ease of fabrication, not require to cryogenic materials and portability is paid special attention. One of the most proper of thermal detectors are bolometers that widely used in military and civilian industries, specially in thermal imaging of cancerous tissues and glands. In bolometers, after absorbing IR waves, sensing material is heated and will be changed it,s electrical resistance. So high infrared absorption and large temperature coefficient of resistance (TCR) are preferred characteristics for sensing material used in bolometers. Due to problems of conventional sensing materials used in bolometers like toxicity and complex expensive fabrication, researchers lately investigate biological and organic materials.
In this thesis, two biological IR absorbing materials called chitosan and cytochrome c introduced and studied their bolometry properties. In first part, thin film of chitosan biopolymer spin coated on indium tin oxide (ITO) substrate and sandwiched by Al electrode. Then TCR and stability of IR sensor is examined during six days. The sensor is unstable over time and TCR values changed in different days. The maximum acquired value of TCR was 17%/ 0C in 500C that is four times larger than those conventional sensing materials like vanadium oxide and amorphous silicon (a-Si) in room temperature. TCR values of chitosan in room temperature are very low so by this view, it is not a suitable matter for using in bolometers.
In next part of thesis, bolometric properties of cytochrome c protein is investigated. For accurate study of cytochrome and comparison with present organic materials, conducting polymer of PEDOT:PSS that is an IR absorbing material be used. So first, thin films of cytochrome and PEDOT:PSS on Cu substrate and between it,s electrodes fabricated by drop casting method.Then experiments of determination of TCR, response time (speed of response) to IR radiation and response to temperature variations in 3 to 5 micron wavelength range of IR source investigated for fabricated sensors. Also temporal stability of cytochrome and PEDOT:PSS films are studied. The films were unstable so for improvement of stability, UV glue as a protective layer was used. Results show cytochrome c has a larger TCR and lower response time but PEDOT:PSS is more stable than cytochrome c.