THE CAUSES OF THICKNESS DEPENDENCE OF CDSE AND CDS GAS-SENSOR SENSITIVITY TO OXYGEN

The sensitivity of semiconductor sensors based on thin films depends o n their thickness, in almost all cases. This phenomenon is of practica l usage but its mechanism is not revealed completely. CdSe and CdS fil ms were used as sensors for the detection of oxygen. CdSe films were m ade by thermal evaporation in vacuum, and CdS films by electrohydrodyn amic spray of the liquid on to the heated substrate. Changes in compos ition and in adsorption sensitivity of the sensors were studied by X-r ay photoelectron spectroscopy (XPS) and secondary ion mass spectroscop y (SIMS) methods. The irregular distribution of components along the t hickness and the peculiarities in their ratio near the substrate have been observed. The model of CdSe and CdS sensor adsorption sensitivity dependence on thickness is developed, based on the obtained data.