Luminescence and Electrical Properties of CdS Films Doped with Potassium and Sodium

Abstract

CdS films, both pure and doped with the alkali metals Na and K, with Cl and without it, obtained by the aerosol pyrolysis method from thiourea coordination compounds at a temperature of 250 to 500 o C are investigated. The photoluminescence spectra and the dependence of the luminescence intensity on the duration of exposure of samples to a high-power UV radiation have been obtained. The doping of samples results in a tenfold increase in the intensity of the luminescence band in the visible spectrum range (650-850 nm) as compared to pure samples of CdS. Upon irradiation of samples by high-power UV radiation for 1 h, no noticeable change in the intensity of luminescence of CdS films was observed. This is indicative of the stability of the films under study against the action of UV radiation. The luminescent properties of the films, obtained pyrolytically using thiourea coordination complexes, are determined by the synthesis conditions as well as by the chemical nature of the original substances.Introduction. Semiconductor compounds based on metal sulfides occupy an important place in contemporary engineering. This is due to a variety of electrical, photoelectrical, and optical properties of the given class of compounds. One such compound is cadmium sulfide, which is widely used for manufacturing photoelectric, recording, and regulating devices.Advances in contemporary materials science are closely related with the progress made in the technology of thin films. It is known that the production technique has a profound effect on the film characteristics. Therefore, at present, of great importance are the development and improvement of the techniques of synthesis of metal sulfide films that allow one to produce materials with controllable properties. Among these techniques is the method of spraying solutions of thiourea coordination compounds (TCC) onto a heated substrate [1]. The promise of practical application of this method lies in the simplicity of producing metal sulfide films of mixed composition at fairly low temperatures and the possibility of implanting active impurities into films immediately in the process of obtaining and creating complex heterostructures, which permits one to extend the range of application of the useful properties of these semiconductor materials.The investigations carried out earlier [1] made it possible to formulate conditions for obtaining sufficiently pure metal sulfide layers, solid solutions, and heterostructures based on them.For contemporary optoelectronics, of special interest are thin-film compounds possessing diverse luminescent characteristics.It is known that single and microcrystals of CdS are distinguished for good luminescence in the visible spectral region [2], with undoped cadmium sulfide samples possessing the green "edge" (+520 nm) and red (+730 nm) luminescence bands. In the longwave spectral region there is an IR band (+1000 nm). Moreover, high photosensitivity of CdS films is noted. It was Boer and Borchardt [3] who already revealed and studied the photofatigue (a ...

Highly improved hydration level sensing properties of copper oxide films with sodium and potassium doping

“…For example, doping with alkali metals such as Sodium and Potassium enhances the conductivity, sensitivity and selectivity of humidity sensors [10][11][12]. It was reported that doping thin films with alkali metals affects luminescence and electrical properties of films [13,14]. Also, alkali metals are highly reactive hence can easily be oxidized which makes them even more suitable dopant for metal oxide nanostructures [15].…”