Chemistry, Physics and Technology of Surface

ISSN 2518-1238 (Online), ISSN 2079-1704 (Print)

Sol-gel method followed by centrifugation obtained film ZnO: Al porous substrates on Si (1 1 1). The influence of annealing temperature and the amount of application and drying of sol layers on the surface roughness, structural stability of ZnO:Al film, shrinkage and compaction of the film, physical stability and exfoliation are considered.

The aim of this work is to obtain and study the structural properties of the film ZnO:Al on porous Si (1 1 1) substrate. The pore size of the substrate is 500 nm. The depth of the porous layer is 6 μm. The precursor contains 0.3 M zinc acetate Zn(CH₃COO)₂∙12H₂O, absolute isopropyl alcohol, dіmethylformamide, 2-methoxyethanol and AlCl₃∙6H₂O. The mixture is placed in an ultrasonic bath. The mixing process lasts 30 min. The resulting solution is aged for 52 h at the temperature of 22±2 °C. The sol is applied by spin-coating (3000 rpm, 30 s). Next, the baking process is carried out with a step of 10 min and a temperature interval of 20 °C. The processing temperature reaches 350 °C. Then the samples are cooled to room temperature. The application process and drying are repeated until the required thickness is obtained. At the last stage, the temperature range was 20 °С; the final annealing temperature was 500 and 550 °С.

The surface morphology and cross section of the obtained structure were characterized by scanning electron microscopy. The chemical composition of the surface was studied using X-ray spectral microanalysis. Phase analysis was determined using an X-ray machine DRON-3M.

It has been found that with multiple deposition of sol layers (8 or more), healing of cracks in the lower layers of the resulting coatings occurs. It has been proven that at an annealing temperature of 550 °C the film surface is smooth, homogeneous, less rough, and has higher adhesion to the silicon substrate. The resulting ZnO:Al films have a thickness of ~ 1 μm. The films have a hexagonal wurtzite structure. EDAX-spectra demonstrate the stoichiometric composition of the surface of the heterostructure ZnO:Al/porous-Si/Si.

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