Highly selective PbS thin film based ammonia sensor for inert ambient: In-situ Hall and photoelectron studies

• Published in: Applied surface science 2018-10, Vol.456, p.430-436
• Main Authors: Beatriceveena, T.V., Prabhu, E., Sree Rama Murthy, A., Jayaraman, V., Gnanasekar, K.I.
• Format: Article
• Language: English
• Subjects: Ammonia sensor; Hall studies; Lead sulphide; Pulsed laser deposition
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/j.apsusc.2018.06.145

PbS thin films show a significant reduction in hole carrier concentration in presence of trace levels of ammonia and N 1s level shows a dissociative adsorption of NH3 on PbS surface. [Display omitted] •Highly selective PbS thin films for monitoring trace levels of ammonia in inert ambient.•PbS responds to 20–500 vppm of ammonia and retraces in oxygen free inert ambient.•In-situ Hall measurements confirm that hole carrier concentration decreases during ammonia sensing.•Core shell XPS reveals that ammonia is dissociatively adsorbed on PbS. Granular thin films of p-type semiconducting PbS (Cubic) with predominantly a-axis oriented grains having an average grain size of about 300 nm were deposited on polycrystalline alumina by pulsed laser deposition technique. Optical measurements show a band gap of 2.25 eV. The thin films were highly selective to ammonia at 473 K even in the presence of hydrogen and they operate in inert ambient with a typical response and recovery times of about 25 s and 120 s respectively. In-situ Hall measurements show an exponential decrease in hole carrier concentration with increasing NH3 level. XPS analysis of Pb 4f and S 2p levels reveals that the valence state of Pb and Sulphur remain in +2 and −2 respectively after exposure to the reducing ammonia and the appearance of N 1s peak at 398.1 eV confirms dissociative chemisorption of ammonia on PbS surface.