C. Morales

Physicochemical conditions for ZnO films deposited by microwave chemical bath deposition

Physicochemical analysis was carried out to obtain the species distribution diagrams (SDDs) for the deposition of ZnO films as a function of OH− ion concentration ([OH−]) in the reaction solution. The study of SDDs predicts nucleation and ZnO film growth by means of the dominant species at a given pH value. To confirm this, a series of experiments were made varying the [OH−] in the reaction solution and keeping the others parameters constant. Structured zinc oxide (ZnO) films were obtained on glass substrates by microwave chemical bath deposition (MWCBD). Structural, optical and morphological ZnO film properties were investigated as a function of [OH−]. X-Ray diffraction technique (XRD) measurements show multiple diffraction peaks, indicating the polycrystalline nature of ZnO films. Scanning Electron Microscopy (SEM) images of ZnO structures showed morphological changes with the variation of [OH−]. The stoichiometry of the structures changed as the [OH−] was varied in solution. From Raman spectra, it was observed that the [OH−] of the reaction mixture strongly affects the crystal quality of ZnO structures. A reaction pathway for the synthesis of ZnO structures based on our results is proposed. Experimental results are consistent with the physical–chemical analysis.

Oxygen concentration effect on properties of SiOC thin films obtained by HWCVD

This work presents a study of the changes in the optical, morphological and compositional properties of SiOC thin films obtained by hot wire chemical vapor deposition (HWCVD) technique. A mixture of hydrogen (H2), oxygen (O2) and monomethyl-silane (MMS) was used as reactant gas, which was passed through a tantalum filament (Ta) in order to be decomposed and obtained the film. Changes were made in the oxygen concentration into the reactor to observe its influence on the luminescent properties of the obtained films. From FTIR absorption spectra of the films was possible to identify absorption bands corresponding to Si-O, Si-C, Si-H and Si-OH bonds. It was observed that when deposition temperature increases, the intensities of the absorption bands of the species H and OH also increase. On the other hand, from the SEM images it was observed an increase in the grain size when oxygen flow is higher, while from ellipsometry and EDS results it was observed that exist incorporation of Ta when higher oxygen flow is used. The presence of Ta in our films can be due to the degradation of the filament during the deposition. Besides, all samples obtained at low oxygen flows presented a very low emission, while those obtained at higher flow presented a wide and intense band emission in the visible spectrum, even though, it has not been possible to identify if the emission is due to effects of quantum confinement or defects in the SiOx matrix.