The influence of the technical parameters of nanostructured CeOx film production on electronic,structural, optical, and photoelectronic characteristics has been studied for their practical application as the active element of various microelectronic sensors—such as highperformance photoresistors, MOSphoto diodes for bioluminescence registration, ionselective fieldeffect transistor (ISFETs), and MOSvaractors indicating pH changing as a result of biochemical processes. Xray photoelectron spectroscopy analysis (XPS) has shown that the ratio of Ce3+ and Ce4+ ions in CeOx films has changed, depending on the techno logical regime and, first and foremost, on the temperature of the substrate, which results in an changing of the fundamental gap width. The correlation between these alterations and the optical and photoelectric char acteristics has been determined. On the basis of highly sensitive photo photoreceivers and living organisms (daphnia and bioluminescence bacteria), a portative electron bioluminescent metric complex has been cre ated to determine the overall water toxicity caused by mycotoxin patulin, biphentrin, and chlorpyrifos. The minimal sensitivity threshold for patulin is 0.1 mg/l after a 2 h experiment and 0.01 mg/l after 6 and 24 h experiments; for biphentrin, it is 0.01 mg/l after a 3 h experiment and 0.0001 mg/l after a 24 h experiment. It is shown that applying nanocrystalline films of cerium oxide CeOx as the dielectric of MOS structures increases the sensitivity and stability of these sensors due to the high density of the surface of sensitive centers of CeOx (to 1020 m–2), the high values of dielectric permeability (ε = 26) and the bandgap width (3.6 eV), and low values of leakage currents. The results of ISFET and MOS varactor application with nanocrystalline CeOx film for the creation of immune and enzymatic biosensors have been demonstrated. The sensitivity threshold of an enzymatic sensor based on choline esterase to organophosphorous pesticides is 10–9 M, and for ions of heavy metals it is 10–7 M. The pH sensitivity of ISFET is 58 mV/pH, which is close to the maximal possible sensitivity for the semiconductor–dielectric–solution structure (the socalled Nernst sensitivity is 59 mV/pH).
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