Characterization of granular metal oxide semiconductor gas sensitive layers by using Hall effect based approaches

• Published in: Journal of physics. D, Applied physics Vol. 40; no. 23; pp. 7217 - 7237
• Main Authors: Oprea, A, Bârsan, N, Weimar, U
• Format: Journal Article
• Language: English
• Published: IOP Publishing 07.12.2007
• ISSN: 0022-3727; 1361-6463
• DOI: 10.1088/0022-3727/40/23/S05

The paper provides a critical assessment of the progress made in the field of gas sensing metal oxide semiconductors (MOX) based on the Hall effect measurement as the main experimental data source. At the beginning, the focus is on the morphologic and the functional peculiarities of this type of material that differentiate them among the larger class of polycrystalline, granular and porous semiconductors. On this basis the complications in defining and extracting the electrical parameters of MOX, especially under operating conditions, are discussed. Different experimental solutions addressing the Hall effect measurements on gas sensing MOX reported in the literature are then briefly presented as the foundation of the discussions about the most utilized modelling procedures. Two main trends are identified: the solid-state and the chemo-physical ones. The solid-state methods focus on the crystallite energy structure, introducing the external influences as model parameters describing the interface trap distribution. The chemo-physical models firstly give a physical picture of the chemical interaction of the ambient with the solid-state surface by connecting the target gases partial pressures with the surface trap concentration and energy and, afterwards, follow the formalism used by the solid-state models. For each type of approach, representative examples and applicative illustrations are considered. An extended overview of the accessible data is included at the end of the paper in a tabulated form.