Laboratory of Atomic and Molecular Layer Deposition (ALD/MLD) of Dagestan State University

Surface chemistry is being developed for atomic layer deposition of new oxide nanomaterials for use in electronics, energy, ecology, nanomedicine, and biotechnology. The mechanisms of surface reactions and the obtained nanofilms are comprehensively studied using quantum chemical modeling, as well as such physico-chemical analysis methods as X-ray reflectometry and diffractometry, spectroscopic ellipsometry, X-ray photoelectron spectroscopy, etc. The main results obtained: 1. The ALD process of mixed titanium-vanadium (TixVyOz) and aluminum-vanadium (AlxVyOz) oxide thin films using new combinations of precursors (TiCl4 (TMA), VOCl3 and H2O) were developed, thermal transformations of the obtained films were studied, heterostructured TiO2-V2O5 coatings were obtained during annealing of TixVyOz films, the formation of V2O5 nanowires was shown, and during annealing of AlxVyOz, the formation of heterostructured Al2O3-V2O5 coatings was observed, as well as the formation of nanosized nuclei of triclinic AlVO4. 2. The ALD process for molybdenum oxide (MoO3) thin films, mixed titanium-molybdenum oxide (TixMoyOz) and aluminum-molybdenum oxide (AlxMoyOz) thin films were developed using TiCl4 or TMA (Al(CH3)3), MoOCl4 or MoO2Cl2 and H2O as precursors. The use of MoO2Cl2 in ALD processes was demonstrated for the first time. Linear growth and self-limiting behavior of surface reactions were demonstrated for the films obtained using the developed ALD synthesis programs. 3. The ALD process for yttrium oxide (Y2O3) was developed using a new combination of precursors - tris(butylcyclopentadienyl)yttrium (Y(CpBut)3) and H2O. The use of Y(CpBut)3 in ALD processes was shown for the first time. The yttrium precursor showed thermal stability and high reactivity in surface reactions with H2O, linear growth and self-limiting behavior of surface reactions were demonstrated. Films obtained at 230 °C had a cubic polycrystalline structure with an average density of 96% of the bulk density of Y2O3. XPS studies showed the level of carbon impurities below the detection limit (~0.2 at.%).

Synthesis and characterization of multifunctional nanomaterials obtained using atomic layer deposition (ALD) technology and their application in nanomedicine as antibacterial nanocoatings for implantable devices, medical instruments, and in pharmaceuticals. Use of nanotechnology for biomedical applications. The most significant studies in this area: 1. Development of a method for improving the functional (antibacterial and biocompatible) properties of hernia meshes for hernia defect repair by applying antibacterial nanocoatings based on titanium-vanadium oxide films using the ALD method. 2. Development of a method for producing surgical suture materials with improved antibacterial properties using the ALD method. 3. Development of medical masks and filters for artificial lung ventilation and inhalation anesthesia devices with improved antibacterial properties. 4. Development of technology for obtaining new dressings with improved antibacterial and hemostatic properties for accelerated wound healing. 5. Development of a method for obtaining needles with improved echogenic properties for targeted puncture and aspiration biopsy. 6. Development of a technology for reusable surgical instruments for laparoscopic surgical interventions by applying a nanocoating using the atomic layer deposition method. 7. Research in the field of nanobiotechnological applications of the ALD method. Development of a method for increasing the shelf life of food products using antibacterial functional nanomaterials obtained by atomic layer deposition. 8. Development of new promising nanomaterials using the ALD method for biomedical applications based on molybdenum, titanium and aluminum oxides with improved antibacterial properties in natural light.

The main tasks to be solved within the framework of the research: - Evaluation of the probability of various reactions in ALD by calculating thermodynamic parameters using the DFT method; - Evaluation of the chemical activity of gas-phase reagents in ALD reactions; - Calculation of geometric, energy and spectroscopic parameters of reagents and nanostructured formations in the ALD process. The quantum chemistry methods used: - Density functional theory with valence-split basis sets of wave functions; - Various semi-empirical methods for preliminary geometric optimization. The main programs used: ORCA, Avogadro, ChemCraft.

Development of methods and new programs for the synthesis of ALD for obtaining films of titanium, aluminum, etc. nitrides is underway. The main results obtained: 1. Thin films of aluminum nitride and oxynitride were obtained by atomic layer deposition in the temperature range from 170 to 290 °C (the optimum deposition temperature is 200-230 °C). Tris(dimethylamido)aluminum and ammonia were used as precursors for the atomic layer deposition of AlN. The growth rate at 200 °C was ~0.8 Å/cycle. The films were deposited on a Si substrate with a layer of natural silicon oxide. The ratio of atomic concentrations N/Al in the films is ~1.3. Aluminum oxynitride films were obtained by periodically dosing H2O during the atomic layer deposition of AlN at 200 °C. The composition of the oxynitride films corresponded to the formula Al0.5O0.43N0.07; 2. Atomic layer deposition (ALD) of titanium nitride (TiN) was carried out by alternating surface reactions of titanium tetrachloride (TiCl4) and hydrazine (N2H4). Deposition was carried out in the temperature range from 150 to 350 °C. The film deposition process was studied in situ by quartz crystal microbalance (QCM) and Fourier transform infrared spectroscopy (FTIR). At 200 and 225 °C, QCM data showed the self-limiting nature of the surface reactions of TiCl4 and N2H4, as well as the linearity of film growth with the number of cycles. At the optimal growth temperature of 275 °C, the growth rate of the TiNx film was 0.36 Å/cycle. The roughness and density of the 116.3 Å thick film obtained at the given temperature were 7.2 Å and 87.5% (of the bulk density of TiN), respectively. Analysis of these films by X-ray photoelectron spectroscopy (XPS) showed that the chlorine impurity content in them was below the sensitivity limit of the instrument (

Methods have been developed for the MLD synthesis of silicon-containing SiAlCHO, SiCNHO, SiAlCNH, SiAlCONH hybrid organo-inorganic films using cyclosiloxanes (2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane (V4D4), 1,3,5-trivinyl-1,3,5-trimethylcyclotrisiloxane (V3D3)) and cyclosilazane (2,4,6-trimethyl-2,4,6 trivinylcyclotrisilazane (V3N3)) by reactions via the ring-opening mechanism. Linear growth, self-limiting behavior of surface reactions, and highly conformal nature of the films obtained using the developed MLD synthesis programs have been demonstrated. Radical-initiated crosslinking of SiAlCHO and SiAlCONH thin films was carried out by the MLD method by including an additional step of di-tert-butyl peroxide (TBPO) injection. Thermal decomposition of TBPO with the formation of radicals led to the formation of cross-links between chemisorbed linear tetramethyl-tetravinylcyclotetrasiloxane chains during MLD of SiAlCHO film, and trimethyl-trivinylcyclotrisilazane chains during SiAlCONH MLD. The dielectric properties of SiAlCHO MLD films were measured in an Al/V4D4-TMA/Al MIM device. The thin SiAlCHO MLD films with a thickness of only 12 nm synthesized in this work showed a low leakage current density (below 5.1×10–8 A cm-2 at ±2.5 MV cm-1) and good thermal stability. MLD hybrid SiAlCНO films were used as pre-ceramic precursors for the synthesis of ceramics based on organosilicon polymers by thermal post-treatment. The resulting SiAlCO composite ceramic nanofilm based on polymers with nanographitized carbon formed during pyrolysis retained an amorphous structure without cracks and surface segregation, and demonstrated uniform linear shrinkage of the film across the thickness. The ceramic films exhibited photoluminescent properties and demonstrated high temperature stability when annealed in air above 1100 °C.

A new method for producing thin 3C-SiC films on Si by pyrolysis of polyamide films synthesized by molecular layer deposition on Si(111) has been developed. Using trimesoyl chloride (TMC) and 1,2-ethylenediamine (EDA) reagents, polyamide films have been synthesized by the MLD method and the physicochemical transformations occurring in this process have been considered. It has been shown that at a synthesis temperature of 120 °C, a linear dependence of the coating thickness on the number of MLD cycles is observed. The growth rate of the polyamide film was 1.88 nm/cycle. Heteroepitaxy of 3C-SiC(111) films on Si(111) obtained after MLD pyrolysis of polyamide films at a temperature of 1300 °C has been determined. The minimum obtained thickness of the SiC film was ~ 22.1 nm. According to high-resolution TEM data, the 3C-SiC(111) and Si(111) crystal lattices were found to be consistent. The interplanar distance for 3C-SiC films was determined to be ~0.251 nm. Elemental mapping showed a uniform distribution of carbon and silicon in the SiC film. It was found that the most optimal pyrolysis mode, where the smallest number of surface pores is observed, with sufficient time for the formation of SiC, is a linear increase in temperature to 1300 °C for 60 min, for which, however, it is necessary to select the thickness of the polyamide in such a way as to minimize the amount of residual carbon. Different modes of pyrolysis of polyamide films by MLD were studied: at 900, 1000, 1100, 1200, 1300 oC, where reaching the temperature to the set point within 1 hour had a linear character, and holding at the peak temperature also lasted 1 hour. Using Raman spectroscopy, the appearance of peaks characteristic of cubic SiC (3C-SiC or β-SiC) at a temperature of 1100 oC and a gradual increase in the intensity of peaks characteristic of 3C-SiC at temperatures of 1200 and 1300 oC were shown. Conformal and uniform 3C-SiC films were obtained on the surface of the Si substrate treated with reactive ion etching. It was found that after heat treatment of the polyamide film on silicon, the thickness of the forming silicon carbide coating decreases, but the linear dependence of the thickness on the number of MLD cycles observed during the synthesis of the polymer structure is preserved. The obtained results allow us to conclude that it is possible to predict the thickness of the ceramic coating at the stage of obtaining the polymer film.

Vacuum equipment for deposition of ceramic, organic and hybrid organo-inorganic coatings. These capabilities are based on the methods of atomic layer deposition (ALD, deposition of ceramic coatings) and molecular layer deposition (MLD) for obtaining inorganic and organic-inorganic thin films. The etching technology is based on the atomic layer etching (ALE) method. The equipment can be used both for research and development and for production. All equipment is designed with maximum involvement of components from Russian manufacturers, as well as leading foreign companies in the vacuum industry Swagelok, MKS, Kurt Lesker, Fujikin, Inficon, etc. 1) ALD/MLD Master-200 apparatus: This device is designed for both research and development and the manufacture of individual products using thermal ALD, MLD and ALE technologies. The volume of the working chamber is 736 cm3, the internal diameter is 25 cm and the height is 1.5 cm. The maximum substrate temperature is 350˚C. Films can be deposited both on flat substrates (silicon substrates with a diameter of up to 200 mm) and on dispersed materials (in a special holder). In the standard configuration, it is possible to deposit films, their alloys and nanolaminates using up to 6 precursors simultaneously. 2) Granit-6 ALD/MLD apparatus: The equipment is designed both for research and development work and for deposition of ALD and MLD coatings in small batches. This unit is equipped with a large reaction chamber. The working volume of the chamber is 2750 cm3, where the internal diameter is 10 cm and the length is 35 cm. Substrates can be placed in the deposition chamber in batches in the direction of the gas flow. In the standard configuration, the maximum deposition temperature is 250˚C. In an additional configuration, the maximum deposition temperature can be increased to 350˚C. 3) ALD/MLD SPARK apparatus: The unit is designed for both research and development and for the production of individual products. Flat (silicon) substrates up to 3″ (76 mm) in diameter can be used as a substrate. The unit is equipped with a gateway for loading a substrate no more than 2″ (50 mm) in diameter. A substrate up to 3″ in size can be loaded from the front door (optional). The presence of a differentially pumped gateway chamber minimizes the presence of oxygen in the main chamber. Plasma is generated in a hollow cathode made of stainless steel, which also reduces the oxygen impurity content compared to ICP plasma sources manufactured using quartz tubes. The presence of a plasma source allows film deposition not only by thermal methods (ALD, MLD and ALE), but also by plasma-stimulated methods (PE-ALD and PE-ALE). This significantly expands the range of deposited materials. The use of plasma allows for lowering the deposition or etching temperature of some materials.