Electrical behaviour and optical properties of screen-printed ITO thin films

Abstract

Tin-doped indium oxide (ITO) films have been prepared by a screen printing (SP) method. The obtained SPITO films are granular and porous. Sheet resistance of as-made layers, measured by the four-probe method, varies from 5 to 10 IdL depending on firing time. The electrical behaviour of ITO films under different storage conditions was studied. We show qualitatively that the sheet resistance of ITO films depends on oxygen and water vapour pressures. The effect d heat treatment on sheet resistance in air and vacuum was also studied. The interpretation of the observed behaviours is based on the adsorption-desorption and diffusion phenomena. The refractive index n of the films has been determined from experimental R(A) spectra. The dielectric constant &-of the films is deduced from an n2 = fo?) plot by using Drude theory. The degree of porosity of the films and the refractive index of the ITO crystallites were evaluated.by simulating SP ITO as an effective medium. Carrier concentration and mobility were estimated from optical parameters by taking the electron reduced mass m' = O.3me. Finally, the first allowed direct transitions between the valence band and the conduction band, estimated from an a2(hv) plot, were found to be in the range 44.12 eV, depending on fabrication parameters

Porous screen printed indium tin oxide (ITO) for NOx gas sensing

“…When the temperature increases from the ambient to about 100 °C, we observe a slight decrease of the sheet resistance, which could be due to oxygen and water vapour desorption from grain surface (physisorbed species) and pores (quasi-free species). At this stage a non equilibrium between subsurfacic and bulk oxygen occurs leading to a segregation of bulk oxygen to the surface, thus producing further oxygen vacancies [9]. This may explain the fast variation of the resistivity in the 100 °C-200 °C temperature range.…”

“…Above this temperature range, a quasi stabilisation of the resistivity was observed. This behaviour could be due to the low segregation of the deep unstable bulk oxygen and then to rather long delay in oxygen desorption [9].…”

Effect of deposition parameters on properties of ITO films prepared by reactive middle frequency pulsed dual magnetron sputtering

“…16 It is of interest to relate the free electron parameters derived from SE to the resistivity of the films produced at different deposition parameters. These two parameters represent the free electron contribution to the optical constants according to the Drude model.…”

Recovery of Indium form Waste LCD by Solvent Extraction with Ionic Liquids

“…With the rapid development of modern display industry, ITO screen has been widely used in LCD TV, flatscreen televisions, smart phones and other electronic products. [4] On the other hand, a large number of LCD were discarded and stockpiled as hazardous materials due to the fact that the LCD products have a relatively short service life (about 3-5 years). [5] The recycling of indium from waste LCDs has been a hot topic, which is expected to efficiently ease the tight application of indium resource, and has a considerable development prospect.…”