Preparation and study of the titanium oxide thin films doped with Tb3+ and Ce3+ ions

Abstract

In this study, we investigated the dependence of the thickness and refractive index of thin films on the withdrawal speed. The films were produced by dip-coating on a glass substrate. The hydrolytic (conventional) sol-gel method was used in the preparation of titanium alkoxide, which were obtained by homogenizing tetraethylorthotitanate stabilized by beta-diketone (2,4-pentanodione) in an alcohol solution. Potential applications, such as active planar waveguides, were evaluated by m-line spectroscopy, electron absorption spectra in the ultraviolet visible region, and photoluminescence. Based on the m-line measurements, the thickness of the films obtained from the homogenized sols were found to be dependent on the withdrawal speed. The thickness range from 400 to 500 nm to the films prepared by withdrawal speed 100 mm/min, 600 to 700nm using 200 mm/min, and 800 to 900 nm to withdrawal speed 300 mm/min. The refractive index is not affected by deposition speed. The photoluminescence of the Tb III ion exhibited lines that were attributed to the transitions characteristic of this ion, i.e., transitions from the 5 D 4 excited state to the 7 F J (J=3,4,5,6) fundamental state.Keywords: titanium dioxide, sol-gel, coating, waveguide INTRODUCTIONThe development of techniques based on the production of thin films applied to materials science is one of the major factors responsible for technological advances 1. There is much interest today in the design of new materials for waveguides. Based on the mechanical and optical properties of films deposited on transparent substrates, these materials are believed to have a wide range of potential applications in the field of optics 2, 3.Thin films prepared by the sol-gel route have attracted special attention due to the formation of pores in their structure, which may originate applications such as chemical sensors and selective membranes 2, and which may be utilized to produce films with adequate protective behavior on metal substrates 4, 5.Thanks to the spectral wealth provided by the lanthanide series it is possible to find ions that are perfectly suiTable for the regions of the electromagnetic spectrum used in telecommunications. Thin films doped with rare earth ions to obtain materials with luminescent properties offer unique advantages, such as easy doping and control of the concentrations of dopant 6. When doped with photoactive organic molecules, these films can be used as optical components due to the transfer of energy.Various studies have been conducted to obtain information about the morphology, thermal stability and spectroscopic properties of thin films, such as luminescence and life span of excited states 7, 8. These thin films have engendered much interest due to the variety of possible applications, which include optical 9 and electroluminescent 10, 11 devices, sensors 12, 13, biomaterials 14-16 and others 17.Ce 3+ ions have important applications due to their high chemical stability and high diffusion coefficient 18-22. Tb 3+ is used...

A study on the refractive index of sol-gel Ba1-xGdxTiO3 thin films using spectroscopic ellipsometry

“…Where the refractive index at 632.8 nm wavelength increases from 2.01 to 2.33 with the increase of film thickness. Generally, the increase in film thickness improves film densification with the addition of layer deposition [13,21]. Thus, it can be concluded that the variation of the refractive index with the variation of film thickness is attributed to the increase in the film density for thicker films.…”