Wyniki wyszukiwania - BazTech

Ograniczanie wyników

1 Electron Technology

1 2000

Znaleziono wyników: 1

Liczba wyników na stronie

Wyniki wyszukiwania

Sortuj według:

Ogranicz wyniki do:

E-gun sputtered and reactive ion sputterd TiO2 thin films for gas sensors

Edelman F., Rothshild A., Komem Y., Mikhelashvili V., Chack A., Cosandey F.

Electron Technology

2000

Vol. 33, No. 1/2

89-107

Polycrystalline TiO2 films are prospective for gas sensor applications due to the dependence of their electrical conductivity on adsorption of various gases (e.g., O2, H2, CO, NOx, etc.). In this work we present comprehensive structural analysis of the microstructure evilution of TiO2 thin films deposited on SiO2/Si(001) substrates by (1) e--gun sputtering (EGS) of TiO2 target; and (2) reactive ion sputtering (RIS) of Ti target. EGS samples are amorphous in the as--deposited state, transforming to anatase structure (which remain stable up to 800 ° C) as a result of annealing in vacuum. RIS samples are composed of a mixture of both rutile and anatase phases in amorphous matrix in the as -- deposited state, and transform to rutile only after annealing at T>_ 500° C. Both films were found porous. The sensitivity of reduced (vaccum annealed) RIS TiO2 films to O2--environment was studied in an enviromental chamber by switching the total air pressure in the chamber from -3 ~ 8•10 to ~3 Pa for short duration (1 to 10 min.). The films demonstrated fast response in the temperature range 100 ÷ 400° C, their resistance changed considerably according to the air pressure in the chamber. The change in the relative resistance (with respect to the initial resistance at the beginning of each air pulse) was found reversible, and increased with temperature. The response was found inversely dependent on the degree of reduction of the films. In the work we present also (i) effecsts of the film densification during vacuum annealing; (ii) current/voltage characterization of the TiO2 films and the dominant mechanism of conductivity (at room temperature); and (iii) some optical characterization (optical absorption, optical refraction,` Raman scattering and photoluminescence) of the thermally treated TiO2 films. The optical bandgap value of the amorphous (mixed with polycrystalline anatase) EGS TiO2 films was found as 3.7š 0.1 eV. Bandgap, optical absorption and PL ( 2.6 eV peak) intensity were found changing regularly from amorphous to polycrystalline state of TiO2.