The role of doping effect on the response of SnO2-based thin film gas sensors: Analysis based on the results obtained for Co-doped SnO2 films deposited by spray pyrolysis

Electrolytically Exfoliated Graphene-Loaded Flame-Made Ni-Doped SnO2 Composite Film for Acetone Sensing

“…28−30 Moreover, the absence of graphene/ graphite oxide peak at around 10°confirms that graphene is in the reduced state. 35,36 When 0.1 wt % Ni-doped SnO 2 nanopowders is loaded with 0.1−5 wt % graphene, the (0 0 2) and (0 0 4) graphitic peaks are overlapped with the (1 1 0) and (2 2 0) peaks of cassiterite SnO 2 such that the resulting diffraction patterns are not significantly different from the unloaded one. The result can be expected because the content of graphene is so low that the contributions of graphitic peaks are not clearly noticeable.…”

“…In a typical n-type SnO 2 gas sensor, oxygen species (O 2 − , O − and O 2− ) are initially chemisorbed on the surface at elevated temperatures in air. With Ni dopants, Ni 2+ and Ni 3+ ions may substitute Sn sites in and on the SnO 2 surface via defect reactions of NiO and Ni 2 O 3 quasi-molecules that can be represented in Kroger−Vink notation according to 35,36,49 …”

“…The enhancement of acetone responses with Ni doping at low concentrations (0.1−0.2 wt %) may be attributed to the increased density of O − and especially O 2− adsorption sites on nanoparticle surfaces due to additional oxygen vacancies formed in Ni 2+ −V o complexes, which directly enhance the formation of oxygen species at high temperature. 35 In addition, the reduced background electron concentration due to Ni (ptype) doping also facilitates electron transfer from gas molecules to conduction band, allowing much larger change in resistance. At higher Ni doping levels (0.5−2 wt %), the acetone response reduces substantially compared with the optimally doped one.…”

“…The surface disorder can be represented as defective surface states that trap charge carries, causing pinning of Fermi-level, less change of surface conductivity due to charge transfer from reducing reaction and deteriorated gas response. 35,49 3.2.3. Effect of Graphene Loading.…”

Influence of Lattice strain and Dislocations on the LPG Sensing Performance of Praseodymium Doped SnO2 Nanostructured Thin Films

“…On the other hand, deep quenching of defects accompanied by heavy doping exerts strong negative influence on gas sensing properties. Besides, the surface disorder introduced by the heavy Pr-doping is accompanied inevitably by the increase of surface state density [7] which could lead to pining of surface Fermi level and the decrease of sensor response [8]. Figure 6 present the dynamic gas response and recovery behaviour for undoped and 1 wt.% Pr-doped SnO 2 sample for different gas concentration which is measured at 350°C.…”