Co‐adsorption processes, kinetics and quantum mechanical modelling of nanofilm semiconductor gas sensors

Abstract

A quantum mechanical model of co-adsorption on semiconductor surfaces is developed and successfully adopted towards exposure to several gases. It is related to nanofilms and thus allows the application of electric fields altering the electronic surface properties of adsorption centres (electroadsorptive effect, EAE). The model is matched against experimental data with O 2 , NO 2 and CO measurements under the hypothesis of no direct interaction among the species. However the sequence of adsorption plays an important role where the adsorption of one gas species is opening up other sites that are filled by another sort of impinging molecules. Quantum mechanical modelling of co-adsorption: (a) NO 2 and CO present at the SnO 2 surface. (b) Simplified model. (c) Probability of adsorption.

Direct Observation of the Electroadsorptive Effect on Ultrathin Films for Microsensor and Catalytic‐Surface Control

“…Modelling: The Wolkenstein-Geistlinger model [4,5,35,36] formulates a Fermi-level-dependent adsorption coefficient b that is multiplied by the partial pressure in a standard Langmuir isotherm. The model takes into account the quantum chemistry of chemisorption wherein physisorption is considered as an independent precursor of two chemisorbed states ("strong" and "weak").…”

Current Trends in Nanomaterials for Metal Oxide-Based Conductometric Gas Sensors: Advantages and Limitations. Part 1: 1D and 2D Nanostructures

“…As a result of these reactions, a decrease or increase in the resistance (conductivity) of the gas-sensitive layer occurs, which is proportional to the concentration of the test gas [ 22 , 23 , 24 , 25 , 26 , 27 , 34 ]. The processes occurring on the surface of metal oxides during interaction with gases and vapors are repeatedly and in detail described in reviews and books [ 27 , 28 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 , 51 , 52 , 53 , 54 , 55 , 56 , 57 , 58 , 59 , 60 , 61 ]. Second, metal oxide conductometric gas sensors from the very beginning of their development were based on the use of nanomaterials.…”

Activation of thin layers of two aromatic hydrocarbons

“…Acenes are a group of materials with low melting point, and have the advantage that they are well characterized. Studies intended to applications of organic layers in high-tech industry such as chemical sensors and molecular electronic devices are now in progress [1][2][3][4]. A broken surface of covalent silicon possesses a grid of dangling bonds, and the adsorption points are properly defined.…”