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- © Ulrich Dahl
"Gas sensors are of increasing importance for controlling gaseous and/or fluid vicinities, in domestic and professional environments, e.g. in workplaces, in manufacturing sites, in street traffic, or even within the nature. Currently, one of the biggest problems in gas/liquid sensing is that for the most chemicals no selective sensing surface is known, up to now, as the mechanism of sensing action is not completely understood. This has motivated me to carry out research involving the combination of surface chemistry, surface physics and nanoscience / semiconductor device / sensor technology to gain insight into the processes occurring on the atomic and molecular scale on the sensor surface to understand the underlying mechanism. I will accomplish my research goal through the identification and investigation of the adsorbate species and adsorption sites that most significantly affects the surface charge and the semiconductor charge carrier physics in the substrate below."
I joined the Institute for Solid State Physics, TU Berlin as an IPODI fellow in 2020. Before this, I was working as a Scientist in Guru Nanak Dev University, India (2017-2020) and my research was based on carbon naotubes/metal oxide nanocomposites as gas sensors. I completed my PhD degree from Guru Nanak Dev University, India in 2013 and following this I worked as an Assistant Professor in Physics in Amritsar, India (2013-2017). My research during my PhD was more focused on the applied science of sensor materials and devices, and it also inculcated the interest in me to expand my experience in core field of research for which I am working at TU Berlin.
Gas sensors, semiconducting oxides, carbon nanotubes, nanostructures, surface science, material characterization
E-Mail: nipin.kohli at tu-berlin.de
Spectro-microscopy correlation at the atomic level of semiconducting metal oxide surfaces for gas sensor applications
Duration: July 2020 - July 2022
Mentor: Prof. Holger Eisele, Faculty II – Mathematics and Natural Sciences, Institute for Festkörperphysik (Institute for Solid State Physics)
Abstract: Semiconducting metal oxide (SMO) based gas sensors are widely used for a broad range of applications including environmental, toxic gas and process monitoring. The thorough understanding of their exact sensing mechanism, however, is still a great challenge. In this project, I will use a unique combination of physico-chemical investigation techniques in order to study the basic sensing mechanisms of two SMOs, namely, In2O3 and SnO2 as model sensors. I want to study the adsorption processes of different gaseous molecules and their electronic impact on the SMO surface. In particular, I will perform spectroscopy by Scanning Tunneling Microscopy (STM) and Spectroscopy (STS), in conjunction with other surface investigation methods to unravel the sensing mechanism at the atomic scale.
Thus, local and non-local techniques are combined to analyze the changes in the sample morphology, the predominant chemical bonding and the electronic states in the surface-near SMOs induced by the analyte. Of particular concern will be the charge carrier physics and band structure below individual adsorbates as these relate to the sensing mechanism in the integrated sensors. The obtained knowledge will be comprehended to design sensors with optimal sensitivity and chemical selectivity towards a particular gaseous species.