The as grown indium tin oxide (InSnO₂, ITO) layers have high resistivity and the transparency is also very limited though ITO is known as a transparent oxide with n-type electrical conductivity. In this work ITO layers were deposited by evaporation and then underwent a post-growth annealing. Annealing leads to low electrical resistivity and to an enhanced transparency. Annealed samples really show n-type conductivity. In this work ITO coating layers are envisaged for measurements where the layer conductivity plays an important role. One of such cases is when the optical sensitivity can be combined with specific advantages of the electrochemical processes.

ITO layers of typically 10 nm thickness were deposited onto OWLS sensor chips and on Si_1-xTi_xO covered glass substrates. The basic measurement after the annealing was the conductivity determination. On sensor chips also the angle dependent photocurrent spectra were evaluated. This allows the selection of the chips. The electrical conductivity was estimated first by two point direct resistance measurements, then by van der Pauw configuration and by collinear four point probe method. W needles and Sn containing mechanical contacts were used. All types of contacts proved to be applicable. Contact resistance was determined separately. Also the repetitivity of the technological processes was controlled partly by electrical measurements.

Storage time dependent stability and light sensitivity were studied. It is demonstrated that the resistance decreases due to the illumination, but in a very small extent. The decrease depends on the wavelength and the process is very slow (tens of minutes, up to hours). The recovery is also slow and also some drift in resistance is observed under continuous repetitive measurements.

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1. OWLS See in the Darkness: a Label Free Microbiological Detection Method with SiTiO and InSnO Coated Planar Waveguide Sensor
2. Combination of the Optical Waveguide Lightmode Spectroscopy Method with Electrochemical Measurements
3. Influence of Illumination and Decay of Electrical Resistance of ITO Nanoscale Layers
4. An RBS Study of Thin PLD and MOCVD Strontium Copper Oxide Layers
5. Surface Scattering Optical Loss Measurements in Thin Oxide Planar Waveguide Layers