Physical properties of CdS/ITO thin films growth by CBD technique with substrate oscillating agitation

Abstract

Cadmium sulphide (CdS) thin films deposited on indium tin oxide (ITO) substrates were prepared by chemical bath deposition technique by using different conditions to agitate the bath and the substrate. For substrate, an oscillating device working at 37 Hz was adapted to support each ITO substrate in order to agitate the substrate during deposition, meanwhile the chemical solution is heated and/not agitated. The deposited films were characterized on their morphology, on the band gap energy, and on thickness. The implemented novel technique for substrate oscillation has shown to improve the films quality, by the chemical bath without colloidal precipitates and by the clean film surfaces obtained. CdS films with variable deposition time can be achieved depending on the agitating technique. The mean band gap energy obtained around 2.41 eV is similar to the typical value reported in the literature for this material. In addition, by oscillating only the substrate during deposition is possible to obtain clean films and avoid the formation of colloidal precipitates on the chemical bath, normally presented when it is magnetically or ultrasonically agitated.

Chemical bath deposition of CdS films on different substrate orientations

“…Thus, during deposition, chemical bath agitation plays an important role in the film surface quality due to the homogenization in both chemical mixing and bath temperature: a regular grain size is obtained, and the film surface dispersion minimized during deposition. Magnetic [8,9], ultrasonic [10e12], oscillation [13] and rotation [14] are types of bath agitation reported for CdS preparation; moreover, the agitation can also be applied directly on substrates, instead of stirring on the chemical bath. Magnetic agitation is the most common technique used to homogenize the chemical bath and there exist several works describing its importance [8,9].…”

Comparative Study of CdS Nano Films Deposited by Chemical Bath and Close Spaced Sublimation Techniques

“…o C thiourea of (0.2 M) about 80 ml solution was added to start fabrication. The films were fabricated with magnetic stirring of 3 Hz for 10-30 minutes at 75 o C. as described in [5]. CdS (CSS) fabrication was carried out in a vacuum chamber of approximately 4x10 -1 mbar.…”

“…It was also observed that at high source temperature, grain size was bigger in the CSS technique. It is reported in the literature that even less crystalline and non uniform films of CBD process gave high efficiency as compared to CSS [5].…”

“…The CdS is a suitable n-type material, which can be fabricated by a variety of fabrication techniques like sol gel technique [4], close spaced sublimation (CSS), chemical bath deposition (CBD), thermal evaporation, chemical vapor deposition, molecular beam epitaxy and spray pyrolysis. Each and every deposition process provides different optical, structural, electrical and morphological properties [5][6][7][8][9][10]. First solar company has reported CdS deposited by high rate vapor transport deposition (HRVTD).…”

“…It is a process in which substrate is placed in a hot chemical solution stirring vigorously for specific time, positive and negative ions will reach and meet on the substrate and thin film is grown. The advantage of this technique is that neither vacuum nor very high temperature is required for CBD [5,21].…”