Thickness dependent electrical properties of CdO thin films prepared by spray pyrolysis method

Abstract

A large number of thin films of cadmium oxide have been prepared on glass substrates by spray pyrolysis method. The prepared films have uniform thickness varying from 200-600 nm and good adherence to the glass substrate. A systematic study has been made on the influence of thickness on resistivity, sheet resistance, carrier concentration and mobility of the films. The resistivity, sheet resistance, carrier concentration and mobility values varied from 1"56-5-72× 10-3f~-cm, 128-189f~/El, 1"6-3.9× 1021 crn-3 and 0.3-3 cm2/Vs, respectively for varying film thicknesses. A systematic increase in mobility with grain size clearly indicates the reduction of overall scattering of charge carriers at the grain boundaries. The large concentration of charge carriers and low mobility values have been attributed to the presence of Cd as an impurity in CdO microcrystallites. Using the optical transmission data, the band gap was estimated and found to vary from 2.20-2.42 eV. These films have transmittance around 77% and average reflectance is below 2.6% in the spectral range 350-850 nm. The films are n-type and polycrystalline in nature. SEM micrographs of the CdO films were taken and the films exhibit clear grains and grain boundary formation at a substrate temperature as low as 523 K.

Structural, optical and electrical characterization of CBD synthesized CdO thin films: influence of deposition time

“…7 shows the graph of logσ dc versus 1000/T which confirms the semiconducting nature of CdO as DC conductivity increases with temperature. It is also observed from the graph that the conductivity increases with the thickness which might be due to a decrease in grain boundaries with an increase of film thickness as reported previously [38]. The obtained data was fitted to the Arrhenius equation:…”

Studies on optical and dielectric properties of Al2O3 thin films prepared by electron beam evaporation and spray pyrolysis method

“…At very high temperatures chemical reaction takes place before the vapor reaches the substrate and gives powdery coating. The spray set up used in this work was presented elsewhere [12]. In this method, a simple glass nozzle was fabricated to spray a very fine and small droplets, when the solution is driven by either air from the compressor or nitrogen from a cylinder.…”

Indium-cadmium-oxide films having exceptional electrical conductivity and optical transparency: Clues for optimizing transparent conductors

“…For x ϭ 0.0, the four-probe electrical conductivity (3,000 S͞cm; n-type) is approximately comparable to that of commercial ITO, whereas the charge carrier mobility of Ϸ150 cm 2 ͞Vs rivals or exceeds that of known TCO films, including that of CdO films grown by other deposition methods (ref. 20 and references therein). We speculate that the present rather ''soft'' growth technique provides higher O 2 partial pressures as well as conditions for greater film microstructural orientation and crystallinity.…”