With growing industrialization and technological advancement, monitoring breathable air and drinkable water quality has become indispensable. Conventional sensors suffer from low life time and are expensive due to semi-automated fabrication and costly electrolyte. In this regard, resistive sensors have simpler structure and CMOS compatibility thereby facilitating batch fabrication. Resistive sensor often has metal oxides which work at elevated temperature (200-400C), have poor selectivity and are sensitive to humid environment. My talk would aim at establishing nanostructured NiO based (i) gas and (ii) Heavy metal ion sensors smart environmental monitoring with improved performance. The selectivity, operating temperatures and bio-compatibility were tuned by (i) varying nanostructure morphologies (ii) metal doping onto NiO lattice and (iii) fabricating junction devices. My talk would focus on a novel heterojunction non-linear devices that was fabricated to replace conventional complex resistive gas sensor arrays. The devices, when operated in the linear region showed tunable selectivity. Two such devices were fabricated: (i) Fe 0.1 Ni 0.9 O/NiO and (ii) ZnO/NiO heterojunctions. The first one was a p + -p heterojunction which showed tunable selectivity towards 2-propanol, toluene and formaldehyde vapors depending on the operating temperature. The tuning of selectivity could be achieved due to exponential increase of thermal carriers. The second one was a p-n heterojunction which demonstrated voltage tunable selectivity among 2-propanol, toluene and formaldehyde vapors. Both the devices were operated under forward bias. A detailed possible mechanism that governed the sensing was put forward. This device would be highly feasible for most hand-held daily applications.
Sayan Dey has completed his Ph.D. from the department of Electronics & Electrical Communication Engineering, Indian Institute of Technology Kharagpur on July 2020. He has done his B.Tech in Electronics & Communication Engineering from West Bengal University of Technology in 2011 and M.Tech in Nanoscience and technology from Jadavpur University, Kolkata in 2015. He worked as assistant systems engineer in Tata Consultancy Services Limited, Kolkata from March 2012 to August 2013. He was awarded the Innovative Student’s Project Award (M.Tech category) by the Indian National Academy of Engineering (INAE), New Delhi in 2015. His research interests are design and fabrication of nanomaterials based chemoresistive sensor devices for environmental and health monitoring and its interfacing circuitry.