Controlled aging of PbS colloidal quantum dots under mild conditions

A new controlled aging methodology was developed for the synthesis of PbS colloidal quantum dots (QDs), applying larger PbS QDs as a starting material for smaller QDs by application of environmentally friendly oleic acid and oleylamine as reagents. This simple and mild procedure provides a possible strategy for tailoring the size-dependent properties of PbS QDs.     

Atomic layer deposition of the titanium dioxide thin film from tetraethoxytitanium and water

Using the methods of Rutherford backscattering spectrometry, X-ray photoelectron spectroscopy, X-ray diffraction in the geometry of the grazing beam, and Fourier transform infrared spectroscopy, we studied the chemical composition and structure of thin films of titanium dioxide formed by atomic layer deposition from tetraethoxytitanium and water. It is shown that the films obtained are characterized by a high stoichiometry of composition and by amorphous or polycrystalline structure of the anatase modification, depending on the number of reaction cycles. Using a model of the process of atomic layer deposition that takes into account the size and number of ligands of the reacting molecules, we calculated the amount of titanium dioxide deposited in a single reaction cycle.     

Atomic layer deposition of thin films of titanium dioxide from titanium tetramethoxide and water

The atomic layer deposition of titanium oxide in the precursor systems Ti(OCH₃)₄-H₂O and Ti(OC₂H₅)₄-H₂O was compared. The growth rate of titanium oxide formed by the atomic layer deposition in the Ti(OCH₃)₄-H₂O system can be adequately estimated with due to regard for the number and size of ligands of a metal-containing precursor. The study in simulated body fluid solutions showed that polycrystallin TiO₂ coatings with anatase structure are prone to accelerated osseointegration and, consequently, promising for the development of new biomedical products.     

Structural properties of the titanium dioxide thin films grown by atomic layer deposition at various numbers of reaction cycles

A dependence of structural properties of TiO₂ films grown on both Si- and Ti-substrates by atomic layer deposition (ALD) at the temperature range of 250-300 °C from titanium ethoxide and water on the number of reaction cycles N was investigated using Fourier-transform infrared (FTIR) spectroscopy and X-Ray diffraction (XRD). TiO₂ films grown on both Si- and Ti-substrates revealed amorphous structure at low values of N < 400. However, an increase of N up to values 400-3600 resulted in the growth of polycrystalline TiO₂ with structure of anatase on both types of substrates and according to XRD-measurements the sizes of crystallites rose with the increase of N. The maximum anatase crystallite size for TiO₂ grown on Ti-substrate was found to be on ∼35% lower in comparing with that for TiO₂ grown on Si-substrate. A use of titanium methoxide as a Ti precursor with the ligand size smaller than in case of titanium ethoxide allowed to observe an influence of the ligand size on both the growth per cycle and structural properties of TiO₂. The average growth per cycle of TiO₂ deposited from titanium methoxide and water (0.052 ± 0.01 nm/cycle) was essentially higher than that for TiO₂ grown from titanium ethoxide and water (0.043 ± 0.01 nm/cycle). Ligands of smaller sizes were found to promote the higher crystallinity of TiO₂ in comparison with the case of using the titanium precursor with ligands of bigger sizes.     

Atomic-layer deposition of thin titanium dioxide films from tetramethoxytitanium and water

Comparative analysis of atomic-layer deposition of titanium dioxide in precursor systems Ti(OCH₃)₄-H₂O and Ti(OC₂H₅)₄-H₂O demonstrated that the growth rate of titanium dioxide produced by atomic-layer deposition in the Ti(OCH₃)₄-H₂O system can be adequately estimated using a model taking into account the number and size of ligands in the metal-containing precursor. Studies in simulated body fluids demonstrated that polycrystalline anatase TiO₂ coatings are capable of accelerated osteointegration, which makes this precursor promising for development of new biomedical articles.     

Atomic layer deposition of titanium dioxide thin films from tetraethoxytitanium and water

The structure and chemical composition of the titanium dioxide thin films formed by atomiclayer deposition (ALD) from tetraethoxytitanium and water precursors were studied by Rutherford backscattering spectrometry, X-ray photoelectron spectroscopy, grazing incidence X-ray diffraction, Fourier transform infrared spectroscopy, and atomic force microscopy. The deposited films were demonstrated to have good stoichiometry and anatase type polycrystalline structure. The growth per cycle of titanium dioxide was calculated by an ALD model taking into account the sizes and number of ligands in reactant molecules.