Features of Ce(IV) phosphate coatings formation on the silica surface during their synthesis by successive ionic layer deposition method

Abstract

The article presents the conditions for obtaining Ce(IV) phosphate coatings on the surface of silicon and quartz by the successive ionic layer deposition (SILD) method. It has been shown that when using solutions of (NH₄)₄Ce(SO₄)₄ and NaH₂PO₄ as reagents, coatings of the composition Ce(OH)PO₄·nH₂O are formed on the surface of the substrates, and when solutions of (NH₄)₄Ce(SO₄)₄ and Na₃PO₄, coatings of the composition Na_0.2Ce(OH)_2.4(PO_4)0.6·nH₂O are formed. These compounds have an amorphous structure. SEM analysis of Na_0.2Ce(OH)_2.4(PO_4)0.6·nH₂O on the silicon surface showed that for the samples obtained as a result of 15 SILD cycles, the planar isotropic coatings are rolled into microtubules with a microscroll morphology of 3–5 μm in diameter and 30–100 μm in length. The composition of the noted Ce(IV) phosphates can be relatively easily doped during the synthesis process, for example, with Fe(II) cations and tungstate anions. It was found that Ce(OH)PO₄·nH₂O coatings are characterized by intense absorption band in the UV region of the spectrum, and can be used as components in various types of absorbers. Moreover, the degree of absorption can be controlled by varying the number of synthesis conditions, for example, the number of SILD cycles.