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High-density phases of TiO2, such as rutile and high-pressure TiO2-II, have attracted interest as materials with high dielectric constant and refractive index values, while combinations of TiO2-II with anatase and rutile have been considered promising materials for catalytic applications. In this work, the atomic layer deposition of TiO2 on α-Al2O3 (0 0 0 1) (c-sapphire) was used to grow thin films containing different combinations of TiO2-II, anatase, and rutile, and to investigate the properties of the films. The results obtained demonstrate that in a temperature range of 300–400 °C, where transition from anatase to TiO2-II and rutile growth occurs in the films deposited on c-sapphire, the phase composition and other properties of a film depend significantly on the film thickness and ALD process time parameters. The changes in the phase composition, related to formation of the TiO2-II phase, caused an increase in the density and refractive index, minor narrowing of the optical bandgap, and an increase in the hardness of the films deposited on c-sapphire at TG ≥ 400 °C. These properties, together with high catalytic efficiency of mixed TiO2-II and anatase phases, as reported earlier, make the films promising for application in various functional coatings.

As research into additives and intentionally introduced impurities in dielectric thin film for enhancing the resistive switching based random access memories (RRAM) continues to gain momentum, the aim of the study was to evaluate the effects of chemically presynthesised Ni nanoparticles (NPs) embedded in a dielectric layer to the overall structure and resistive switching properties. HfO2-based thin films embedded with Ni NPs were produced by atomic layer deposition (ALD) from tetrakis(ethylmethylamino)hafnium (TEMAH) and the O2 plasma ALD process onto a TiN/Si substrate. The Ni NPs were separately synthesised through a continuous flow chemistry process and dispersed on the dielectric layer between the two stages of preparing the HfO2 layer. The nanodevices’ morphology and composition were analysed with physical characterisation methods and were found to be uniformly dispersed across the sample, within an amorphous HfO2 layer deposited around them. When comparing the resistive switching properties of otherwise identical samples with and without Ni NPs, the ILRS/IHRS ratio rose from around a 4 to 9 at 0.2 V reading voltage, the switching voltage dropped from ~2 V to ~1.5 V, and a distinct increase in the endurance characteristics could be seen with the addition of the nanoparticles.

Atomic layer deposited polycrystalline Cr2O3 films grown from chromyl chloride and methanol were analysed using spectrophotometry, spectral ellipsometry and atomic force microscopy. The films possessed polycrystalline eskolaite structure with rough sublayer in contact with air. Using the positions and peak widths of the two visible absorption bands as fixed from absorption measurements, we could determine the optical dispersion of the film material in 1.3 – 6 eV energy region. A direct band gap of chromia film grown in these conditions was 3.2 eV, the other also direct absorption band with a gap of 5.15 eV was found situated in UV.

Due to the several applications of biosensors, such as magnetic hyperthermia and magnetic resonance imaging, the use of superparamagnetic nanoparticles or thin films for preparing biosensors has increased greatly. We report herein on a strategy to fabricate a nanostructure composed of superparamagnetic thin films. Ruthenium-doped iron oxide thin films were deposited by using atomic layer deposition at 270 and 360 °C. FeCl3 and Ru(EtCp)2 were used as metal precursors and H2O/O2 as the oxygen precursor. Doping with ruthenium helps to lower the formation temperature of hematite (α-Fe2O3). Ruthenium content was changed from 0.42 at% up to 29.7 at%. Ru-doped films had a nano-crystallized structure of hematite with nanocrystal sizes from 4.4 up to 7.8 nm. Magnetization at room temperature was studied in iron oxide and Ru-doped iron oxide films. A new finding is a demonstration that in a Ru-doped iron oxide thin film superparamagnetic behavior of nanocrystalline materials (α-Fe2O3) is observed with the maximum magnetic coercive force Hc of 3 kOe. Increasing Ru content increased crystallite size of hematite and resulted in a lower blocking temperature.

Producción Científica, Thin HfO2 films were grown by atomic layer deposition on chemical vapor-deposited large-area graphene. The graphene was transferred, prior to the deposition of the HfO2 overlayer, to the HfO2 bottom dielectric layer pregrown on the Si/TiN substrate. Either HfCl4 or Hf[N(CH3)(C2H5)]4 was used as the metal precursor for the bottom layer. The O2 plasma-assisted process was applied for growing HfO2 from Hf[N(CH3)(C2H5)]4 also on the top of graphene. To improve graphene transfer, the effects of the surface pretreatments of the as-grown and aged Si/TiN/HfO2 substrates were studied and compared. The graphene layer retained its integrity after the plasma processes. Studies on resistive switching on HfO2-graphene-HfO2 nanostructures revealed that the operational voltage ranges in the graphene-HfO2 stacks were modified together with the ratios between high- and low-resistance states., Fondo Europeo de Desarrollo Regional (projects TK134 and TK141), Ministerio de Economía, Industria y Competitividad (project TEC2017-84321-C4-2-R), Estonian Research Agency (projects PRG4 and PRG753)

In recent years, several materials and metal-insulator-metal devices are being intensively studied as prospective non-volatile memories due to their resistive switching effect. In this work, thickness-dependent resistive switching polarity was observed in TiN/Ti/HfO2/Pt structures as the sign of the voltages at which SET and RESET occur depended on the film thickness. A thorough revision of the previous literature on bipolar resistive switching polarity changes is made in order to condense previous knowledge of the subject in a brief and comprehensible way and explain the experimental measurements. The different resistive switching polarities occur in a similar voltage range, which is a new finding when compared to precedent research on the subject. A hypothesis is proposed to explain the change in resistive switching polarity, based on the assumption that polarity change is due to filament disruption occurring at different interfaces.

Acid-treated multi-walled carbon nanotubes (MWCNTs) were decorated with TiO2 using the atomic layer deposition (ALD) technique followed by uniform distribution of platinum nanoparticles (PtNPs) through magnetron sputtering. Surface analyses were performed by scanning electron microscopy (SEM), scanning transmission electron microscopy (STEM) and X-ray photoelectron spectroscopy (XPS). Electrochemical decontamination and characterization of the Pt-TiO2/MWCNT electrodes were carried out by CO stripping followed by cyclic voltammetry in acid media. The oxygen reduction reaction (ORR) was studied in O2-saturated 0.05 M H2SO4 solution using the rotating disk electrode (RDE) method. Durability of the prepared catalysts was examined by repetitive potential cycling. Electrochemical data obtained was analyzed and compared to that of the commercial Pt/C catalyst. It was revealed that the Pt-TiO2/MWCNT catalysts possess higher ORR activity and better durability as compared to that of the commercial Pt/C.

Double layered stacks of ZrO2 and SnO2 films, aiming at the synthesis of thin magnetic and elastic material layers, were grown by atomic layer deposition to thicknesses in the range of 20–25 nm at 300 °C from ZrCl4, SnI4, H2O, and O3 as precursors. The as-deposited nanostructures consisted of a metastable tetragonal polymorph of ZrO2, and a stable tetragonal phase of SnO2, with complementary minor reflections from the orthorhombic polymorph of SnO2. The hardness and elastic modulus of the stacks depended on the order of the constituent oxide films, reaching 15 and 171 GPa, respectively, in the case of top SnO2 layers. Nonlinear saturative magnetization could be induced in the stacks with coercive fields up to 130 Oe.

Effective corrosion protection via a thin ceramic coating on an Al-alloy AA2024-T3 is demonstrated. The preparation of the coating consists of two steps. First, with a special anodizing process, a chemically homogeneous thin base layer is formed on the substrate. Then, the nanoscale pores in the base layer are sealed, and the entire surface is covered with a chemically resistant Al2O3/TiO2 nanolaminate using atomic layer deposition. The sample surface is thoroughly characterized, including linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS) and testing by long-term immersion in a salt solution. The coating withstands LSV up to 10 V versus saturated calomel electrode (SCE) and salt solution immersion of 7152 h (298 days).

Producción Científica, ZrO2-graphene-ZrO2 layered structures were built and their crystallinity was characterized before resistive switching measurements. Thin nanocrystalline ZrO2 dielectric films were grown by atomic layer deposition on chemical vapor deposited graphene. Graphene was transferred, prior to the growth of the ZrO2 overlayer, to the ZrO2 film pre-grown on titanium nitride. Nucleation and growth of the top ZrO2 layer was improved after growing an amorphous Al2O3 interface layer on graphene at lowered temperatures. Studies on resistive switching in such structures revealed that the exploitation of graphene interlayers could modify the operational voltage ranges and somewhat increase the ratio between high and low resistance states., Fondo Europeo de Desarrollo Regional (project TK134), Estonian Research Agency (grants PRG753 and PRG4), Ministerio de Economía, Industria y Competitividad (grant TEC2017-84321-C4-2-R)

The oxygen reduction reaction (ORR) activity and durability of Pt nanoparticles sputtered on Nb-doped TiO2 coated glassy carbon and titanium electrodes were investigated. The Nb-TiO2 thin-film coatings were deposited by atomic layer deposition. Scanning electron microscopy and atomic force microscopy analysis revealed a uniform coating of the electrode substrates with doped-metal oxide. X-ray photoelectron spectroscopy analysis confirmed the presence of Nb, Ti, and Pt metals on the electrode surface. Electrochemical characterization of the prepared catalysts was performed by cyclic voltammetry and CO stripping experiments in 0.05 M H2SO4 solution. The Pt/Nb-TiO2 catalyst showed remarkable electrocatalytic activity toward the ORR at a very low Pt loading of 8.6 μg cm−2. The accelerated durability test confirmed that Pt/Nb-TiO2 catalyst was more durable than the commercial Pt/C (20 wt.%). More importantly, the prepared Pt/Nb-TiO2 electrocatalyst showed a considerable increase in the electrochemically active surface area as well as the ORR activity after the durability test.

Graphene layers grown by chemical vapour deposition (CVD) method and transferred from Cu-foils to the oxidized Si-substrates were investigated by spectroscopic ellipsometry (SE), Raman and X-Ray Photoelectron Spectroscopy (XPS) methods. The optical properties of transferred CVD graphene layers do not always correspond to the ones of the exfoliated graphene due to the contamination from the chemicals used in the transfer process. However, the real thickness and the mean properties of the transferred CVD graphene layers can be found using ellipsometry if a real thickness of the SiO2 layer is taken into account. The pulsed layer deposition (PLD) and atomic layer deposition (ALD) methods were used to grow dielectric layers on the transferred graphene and the obtained structures were characterized using optical methods. The approach demonstrated in this work could be useful for the characterization of various materials grown on graphene., Comment: 8 pages, 8 figures, 2 tables, presented on "Solid State Surfaces and Interfaces", November 2016 Piestany, Slovakia

Atomic layer deposition of TiO 2 from TiCl 4 and ozone on single crystal α-Al 2 O 3 substrates was investigated and the possibility to control the phase composition by the substrate orientation was demonstrated. Epitaxial growth of rutile and high-pressure TiO 2 -II on α-Al 2 O 3 (0 0 0 1) and rutile on α-Al 2 O 3 (0 1 1 2) were obtained at 400–600 °C. On α-Al 2 O 3 (0 0 0 1), the epitaxial relationships were determined to be [0 1 0] R // [2 1 1 0] S and [0 0 1] R // [0 1 1 0] S for rutile and sapphire, and [0 0 1] II // [2 1 1 0] S and [0 1 0] II // [0 1 1 0] S for TiO 2 -II and sapphire. The TiO 2 -II concentration up to 50% was obtained in the films deposited at 425–500 °C. On α-Al 2 O 3 (0 1 1 2), the epitaxial relationship of rutile was [0 1 0] R // [2 1 1 0] S and [0 0 1] R // [0 1 1 0] S . The densities of epitaxial films reached 4.2–4.3 g/cm 3 on substrates with both orientations but the epitaxial quality was markedly higher on α-Al 2 O 3 (0 0 0 1).

Pt nanoparticle-titanium dioxide/multi-walled carbon nanotube (Pt–TiO 2 /MWCNT) materials were synthesised by combining chemical vapour deposition (CVD), atomic layer deposition (ALD) and magnetron sputtering techniques. These composite materials were employed as electrocatalysts for oxygen reduction reaction (ORR). The surface morphology of the prepared catalysts as well as their supports was examined by scanning electron microscopy (SEM). The SEM images revealed the preferential growth of aligned MWCNTs. The surface composition of Pt–TiO 2 /MWCNT catalysts was characterised using X-ray photoelectron spectroscopy (XPS). Their electrocatalytic properties toward the ORR were investigated in acid and alkaline media using the rotating disk electrode (RDE) technique. The ORR activity of Pt–TiO 2 /MWCNT was compared with that of commercial Pt/C catalyst and bulk Pt.

Etching rate of technologically important metal oxide thin films in hot sulphuric acid was investigated. The films of Al-, Ti-, Cr-, and Ta-oxides studied were grown by atomic layer deposition (ALD) method on silicon substrates from different precursors in large ranges of growth temperatures (80–900 °C) in order to reveal process parameters that allow deposition of coatings with higher chemical resistance. The results obtained demonstrate that application of processes that yield films with lower concentration of residual impurities as well as crystallization of films in thermal ALD processes leads to significant decrease of etching rate. Crystalline films of materials studied showed etching rates down to values of

Rutile ${\rm TiO}_{2}$ (1 0 1) and cassiterite ${\rm SnO}_{2}$ (1 0 1) epitaxial single and double nanolayers, the latter stacked in either sequence, are atomic layer deposited on $r$ -cut $\alpha\hbox{-}{\rm Al}_{2}{\rm O}_{3}(0~1~\bar{1}~2)$ substrates. Thickness of the layers is varied. Epitaxial quality of the films is characterized by X-ray diffraction (XRD), reflection high-energy electron diffraction, and transmission electron microscopy. In gas response measurements, as-grown films and the films coated with electron-beam evaporated Pt nanoclusters are exposed, at 350 $^{\circ}{\rm C}$ , to ${\rm H}_{2}$ , CO, and ${\rm CH}_{4}$ diluted in air. In response to test gas concentrations of 30 parts per million (ppm), the films with a thickness of order of 10 nm exhibit, depending on the makeup and gas, as high as two- to five-fold decrease in the resistance. It is shown that the platinum surface catalyst is effective in accelerating the response and recovery processes. The transition times of the order of a few tens of seconds are observed. The results demonstrate the feasibility of gas sensing with single-crystal-like nanolayer films. Comparison of sensor characteristics of such quasi-2D nanostructures and the literature data relevant to individual nanowires, nanorods, and nanobelts, i.e., typical representatives of the quasi-1D structures, shows that, as to ${\rm H}_{2}$ , CO, and ${\rm CH}_{4}$ , both structures are worthy competitors.

Properties of TiO2 based DRAM capacitors with equivalent oxide thickness of 0.5 nm are described. It is shown, that dielectric constant values more than 100 can be obtained in these structures for the TiO2 films with the thickness down to 10 nm. Leakage current density below 10-7 A/cm2 at 0.8 V can be obtained after post-deposition processing for the films with the thickness of 16 nm (EOT ≈ 0.5 nm). Al doping of the TiO2 films decreases dielectric constant, but improves leakage current density. Al-doped TiO2 films with the thickness of 10 nm (EOT = 0.46 nm) exhibit leakage current density below 10-7 A/cm at 0.8 V.

Properties of TiO"2-based capacitors with RuO"2 bottom electrode were examined. It is shown that post-deposition room temperature plasma treatment and oxygen annealing at 300^oC significantly reduces amount of impurities in the TiO"2 layer. Leakage current density of the capacitors is suppressed due to improvement of oxygen stoichiometry and increase of Schottky barrier height at the TiO"2-dielectric/metal electrode interface after post-deposition processing. Leakage current density below 10^-^7A/cm^2 was achieved for capacitor with equivalent oxide thickness of 0.58nm.

TiO2–Cr2O3 nanolaminates were atomic layer deposited on (0 1 2)-oriented sapphire and (1 0 0)-oriented silicon. The thickness of the alternating layers in the eight-layer laminates grown was close to 10 nm. The laminates were characterized by cross-sectional high-resolution transmission electron microscopy, high-resolution scanning electron microscopy, atomic force microscopy, reflection high-energy electron diffraction, and micro-Raman spectroscopy. A highly oriented growth of the laminate on sapphire and its growth with a very little preferred orientation on silicon were revealed. The laminate grown on sapphire had, along with better crystallinity, more exactly defined and more planar interphase boundaries. The amount of indefiniteness of the boundaries increased with the layer distance from the substrate. The crystalline phase of titania was rutile in the laminate grown on sapphire and anatase in the laminate grown on silicon, while the crystalline phase of chromia had eskolaite structure. In the laminate grown on sapphire, titania contained numerous twins; compressively strained chromia had in this case more perfect structure.

The resistive response of atomic layer deposited thin epitaxial α-Cr2O3(0 0 1) films, to H2 and CO in air, was studied. The films were covered with Pt nanoislands formed by electron-beam evaporation of a sub-monolayer amount of the material. The gas measurements were performed at 250°C and 450°C. These temperatures led to different proportion of chemical states, Pt2+ and Pt4+, to which the Pt oxidized. The modification was ascertained by the X-ray photoelectron spectroscopy method. As a result of the modification, the response was fast at 250°C, but slowed at 450°C. A disadvantageous abundance of Pt4+ arising at 450°C in air could be diminished by high-vacuum annealing thus restoring the response properties of the system at 250°C.

Chromium oxide thin films were atomic layer deposited from CrO2Cl2 and CH3OH on α-Al2O3(0 0 1) (c -sapphire) substrates at 420 °C. On the basis of X-ray reflection evidence, the thickness of the films in a series prepared ranged from 4 to 400 nm. As it was ascertained by reflection high-energy electron diffraction, the films grew epitaxially. Electron probe microanalysis showed that O/Cr atomic ratio in them was close to 1.5 and that the residual impurities were present in insignificant amounts. The rms roughness of the films measured by atomic-force microscopy and X-ray reflection was of the order of 1 nm or less. X-ray diffraction and Raman scattering data suggested that the films were strained, and that the strain was tensile in the c direction and compressive in the c plane. According to the surface Brillouin scattering measurements, the elastic properties of the films differed only slightly from those for single-crystal bulk chromia. The films, when surface activated with Pt nanoislands, had a moderate response to CO in air with the transition times in the range of tens of seconds. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Atomic layer deposition of Cr2O3 thin films from CrO2Cl2 and CH3OH on amorphous SiO2 and crystalline Si(1 0 0) and α-Al2O3( 1 1 ¯ 0 2 ) substrates was investigated, and properties of the films were ascertained. Self-limited growth with a rate of 0.05–0.1 nm/cycle was obtained at substrate temperatures of 330–420 °C. In this temperature range epitaxial eskolaite was formed on the α-Al2O3( 1 1 ¯ 0 2 ) substrates. The predominant crystallographic orientation in the epitaxial films depended, however, on the growth temperature and film thickness. Sufficiently thick films grown on the SiO2 and Si(1 0 0) substrates contained also the eskolaite phase, but thinner films deposited at 330–375 °C on these substrates were amorphous. The growth rate data of films with different phase composition allowed a conclusion that the crystalline phase grew markedly faster than the amorphous phase did. The amorphous, polycrystalline and epitaxial films had densities of 4.9, 5.1 and 5.1–5.3 g/cm3, respectively.

Epitaxial chromium oxide (α-Cr 2 O 3 ) films grown by atomic layer deposition at 375 °C from CrO 2 Cl 2 and CH 3 OH on (1 1¯ 0 2) oriented α-Al 2 O 3 have been studied by reflection high-energy electron diffraction (RHEED), X-ray diffraction (XRD) and X-ray reflection (XRR). The thickness of the films ranged from 10 to 310 nm, and the average growth rate was 0.1 nm per deposition cycle. According to the XRD analysis, the orientation relationship in thinner films was (1 1¯ 0 2)[1 1 0]Cr 2 O 3 || (1 1¯ 0 2)[1 1 0]Al 2 O 3 . Confirmed by the RHEED and XRD analyses, (1¯ 1 0 2) became the preferred growth plane at the thicknesses above 40 nm. This change has been interpreted as the appearance of an asymmetric rhombohedral twin with the orientation relationship between the layers (1¯ 1 0 2)[1 1 0]top || (1 1¯ 0 2)[1 1 0]bottom and (1¯ 1 0 2)[1 1¯ 1]top || (1 1¯ 0 2)[1¯ 1 1]bottom. The match of the anion and cation sublattices of both layers was characterized in terms of the structural model of the twin interface.

The microstructures of epitaxial SnO 2 (rutile) thin films deposited by atomic layer deposition on α-Al 2 O 3 (0 1 2) substrates at 600°C using either SnCl 4 or SnI 4 as tin precursor have been investigated by X-ray diffraction and transmission electron microscopy. It is shown that the film/substrate interface is flat without any visible additional phase, while the film structure and surface morphology depend on the metal precursor. Typical of the SnCl 4 -process films is a rough surface and a high density of defects, including (0 1 1) and (1 0 1) twins and anti-phase boundaries (APBs). In contrast, the SnI 4 -process films with their uniform thickness, flat surface and low density of APBs approach the perfect single crystal. Irrespective of the processing, all films have (1 0 1) texture, parallel to the substrate surface, with the epitaxial relationships [0 1 0] SnO 2 ∥ [1 0 0] α-Al 2 O 3 and [1 0 1 ] SnO 2 ∥[ 1 2 1] α-Al 2 O 3 .

Undoped SnO 2 thin films are grown on α-Al 2 O 3 (0 1 2) ( r -cut sapphire) substrates by gas phase atomic layer deposition (ALD). Two precursor pairs, SnI 4 –O 2 and SnCl 4 –H 2 O 2 , both new for ALD, are used. The films have a cassiterite structure and are (1 0 1)[0 1 0] cassiterite ||(0 1 2)[1 0 0] sapphire oriented. A good epitaxial quality and the conductivity acceptable from the standpoint of semiconductor gas sensors are achieved for ultrathin films grown from SnI 4 –O 2 at 600 °C. The sensitivity of these films to CO in air has a maximum at a thickness of about 10 nm. Response rise and decay times belonging to a several seconds interval are measured. The films are assumed to function as a single grain.

Many materials exhibit interesting and novel properties when prepared as thin films. Thin film metal oxides have had an impact on the technological progress of the microelectronics mainly due to their electrical and optical properties. Since the future goes towards the nanometre scale there is an increasing demand for thin film deposition processes that can produce high quality metal oxide films in this scale with high accuracy.This thesis describes atomic layer deposition of Ta2O5, HfO2 and SnO2 thin films and chemical vapour deposition of SnO2 thin films. The films have been deposited by employing metal iodides and oxygen as precursors. All these processes have been characterised with regards to important processing parameters. The films themselves have been characterised by standard thin film analysing techniques such as x-ray diffraction, scanning electron microscopy, atomic force microscopy and transmission electron microscopy. The chemical and physical properties have been coupled to critical deposition parameters. Furthermore, additional data in the form of electrical and gas sensing properties important to future applications in the field of microelectronics have been examined.The results from the investigated processes have shown the power of the metal iodide based atomic layer deposition (ALD) and chemical vapour deposition (CVD) processes in producing high quality metal oxide thin films. Generally no precursor contaminations have been observed. In contrast to metal chloride based processes the metal iodide processes produces films with a higher degree of crystalline quality when it comes to phase purity, roughness and epitaxy. The use of oxygen as oxidising precursor allowed depositions at higher temperatures than normally employed in water based ALD processes and hence a higher growth rate for epitaxial growth was possible.

Atomic Layer Deposition of Epitaxial and Polycrystalline SnO2 Films from the SnI4/O2 Precursor Combination.

We report the atomic-layer-deposition growth of SnO2 thin films from SnCl4 and H2O2 (case A), and SnI4 and O2 (case B) on (0 1 2)-oriented α-Al2O3 (corundum) substrates. In case A, the growth rate had a maximum at 250–500°C and slowly decreased at higher temperatures. In case B, the growth rate increased monotonically with temperature, increase being relatively slow at 500–750°C. At 500–600°C, the films grew three times faster in case B than in case A. The phase content, crystalline properties, purity, and thickness of the films were characterized by X-ray diffraction, X-ray reflection, and X-ray fluorescence spectroscopy. The films grown at 250°C and higher temperatures had tetragonal (cassiterite) structure. At 700°C in case A and 400–750°C in case B, the overgrowth could be considered as epitaxial. The orientational relationship has been determined to be (1 0 1)[0 1 0]cassiterite||(0 1 2)[1 0 0]corundum.

The proper choice of coating materials and methods in core–shell nanowire (NW) engineering is crucial to assuring improved characteristics or even new functionalities of the resulting composite structures. In this paper, we have reported electron-beam-induced reversible elastic-to-plastic transition in Ag/Al2O3 and Au/Al2O3 NWs prepared by the coating of Ag and Au NWs with Al2O3 by low-temperature atomic layer deposition. The observed phenomenon enabled freezing the bent core–shell NW at any arbitrary curvature below the yield strength of the materials and later restoring its initially straight profile by irradiating the NW with electrons. In addition, we demonstrated that the coating efficiently protects the core material from fracture and plastic yield, allowing it to withstand significantly higher deformations and stresses in comparison to uncoated NW.

In this work, we have prepared metal-insulator-metal capacitors for dynamic random access memory capacitor application using atomic layer deposition of TiO"2 [email protected] dielectric and RuO"2 bottom electrode. We compare TiO"2 layers grown using TiCl"4 precursor or Ti-tetra-isopropoxide precursor, and Al-doped TiO"2 layers grown using Ti-tetra-isopropoxide precursor. The capacitors were analyzed in the terms of capacitance - voltage and current - voltage measurements and transmission electron microscopy imaging.

A procedure for changing the course of the atomic-layer chemical vapor deposition (ALCVD) growth of TiO 2 from TiCl 4 and H 2 O on amorphous SiO 2 substrates/underlayers at low temperatures is proposed. The changes are characterized by the real-time incremental dielectric reflection measurements and post-growth spectrophotometry and reflection high-energy electron diffraction measurements. In the procedure, an ultrathin layer of the material is deposited and, subsequently, in situ inhomogeneously etched in the TiCl 4 flow, both steps being performed at a temperature above 350 °C. As a result, an ultrathin microrough mixed amorphous/anatase-phase surface layer is created. By using this layer as a seed layer, the crystalline-growth temperature of the material is reduced. So anatase (mixed with amorphous phase) TiO 2 thin films on SiO 2 substrates at 125 °C are, for the first time, grown. The films are shown to be depth-inhomogeneous. The upper part of the films, when they are thicker, is well textured.

Peculiarities of the atomic-layer chemical vapor deposition growth of TiO2 and SnO2 thin films from chlorides and water at low (≤300°C) temperatures are in situ monitored on a submonolayer scale by incremental dielectric reflection. RHEED, AES, EPMA, SFM, and UV–VIS spectrophotometry are used for the ex situ characterization of the growth. It is shown that the main peculiarity of the TiO2 growth exhibits itself in the spontaneous crystallization at the very beginning of the deposition while the peculiarity of the SnO2 growth is connected with a low reactivity of water.

We show that the measuring of the reflectance changes in transparent systems allows one to optically characterize the surface of films growing under the conditions of atomic partial-monolayer deposition. In the model, a continuous layer with effective optical parameters describes the growth front. Growing amorphous TiO 2 thin films from TiCl 4 and H 2 O at 115°C is used in demonstration experiments.

Atomic layer deposition of TiO 2 thin films from TiCl 4 and H 2 O at 150°C was found to result in nonhomogeneous film growth as a function of time. The unevenness of the growth was ascertained by in situ optical interference technique. In order to obtain a more detailed understanding of the growth behavior, AFM, SEM, EPMA, RHEED, XRD, and XPS measurements were performed on a series of films of different thickness. The data obtained allow us to relate the peculiarities of the growth to the appearance of anatase inclusions in the amorphous base layer of TiO 2 followed by their development into crystalline particles. We managed to delimit the nucleation stage of the growth, the stage of the full coverage of the substrate with the amorphous film, the stage of the origination of the anatase inclusions, and the final stage at which the polycrystalline film is deposited. The increase of crystallinity and roughness was correlated with the increase of the film thickness and quantitatively determined. It was found that in our films the composition of both the crystalline and amorphous part corresponds to TiO 2 stoichiometric phase, and that the films contain 0.3 mass% of Cl.

The traveling-wave reactor is an effective instrument for performing atomic layer deposition (ALD). In this paper, the use of a Brewster-angle interferometric reflectance technique for in situ real-time monitoring of ALD growth of transparent thin films on transparent and non-transparent substrates in suited traveling-wave reactors is proposed and analyzed on the basis of a classical four-phase approximation. An appropriate experimental reactor system is described. The technique is applied to the diagnostics of TiO 2 growth from TiCl 4 and H 2 O. Features of the reflectance signal in the conditions of time-homogeneous ALD growth are discussed.

MIM capacitors with MOCVD-grown RuO 2 bottom electrode, ALD-grown TiO 2 rutile dielectric and RuO 2 and Pt top electrodes were prepared and characterised by the means of C-V and J-V measurements. Dielectric constants were in the range of 140, which correspond to EOT of 0.5 nm and leakage current density as low as 1.5*10−6 A/cm2 was achieved. Strong influence of TiO 2 stoichiometry on the leakage currents was found and analysed.

Thin films in the Cr-Ti-O system were atomic layer deposited from CrO2Cl2, TiCl4, and CH3OH on Si(1 0 0), fused SiO2, and a -Al2O3(0 1 2) substrates at 420 oC. The proportion between Ti and Cr resulted from the ratio of the CrO2Cl2/CH3OH and TiCl4/CH3OH pulsing. The films were grown up to the thickness of about 70 nm. Annealing of the films was performed in O2 at 1000 oC. A notable dependence of their microstructure, conductance, and conductometric response to CO, H2, and CH4 in dry air on the substrates, Ti content, and annealing has been demonstrated. The films were polycrystalline on Si and SiO2, and epitaxial on a -Al2O3. At temperatures above 400 oC, the films had a conductance, advantageous from the point of view of semiconductor gas sensors. In response to a 30-ppm CO exposure at 450 oC, an annealed film on the a -Al2O3(0 1 2) substrate, distinguished by a relatively high Ti/Cr atomic ratio, showed a 16-% conductance decrease in 20 s, with a 120-s recovery.© (2006) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Atomic layer deposition (ALD) of SnO2 thin films from SnI4 and either H2O2 or O2 on the α-Al203(1 1- 2) substrates is studied. Reactor temperature is varied from 100 to 750 °C. X-ray diffaction, x-ray reflection, x-ray fluorescence, x-ray photoelectron spectroscopy, reflection high-energy electron diffraction, and UV-visible spectroscopy are used to obtain the growth and structural data. The SnI4-H202 precursor pair brings forth the film growth even at temperatures as low as 100°C with a wholly amorphous outcome up to 150°C. For the pair SnI4-02, the films grown nearby the process initiation temperature of 400°C are also amorphous. When the temperature is raised respectively above 250 and 500°C, both pairs make epitaxial growth happen, generally in three-dimensional mode. Exceptionally, in a limited range of grown thicknesses in the proximity of 50 nm, the growth from SnI4 and O2 at 750°C appears to be driven by the predominantly two-dimensional nucleation, as the films grow extremely flat. The SnI4-02 precursor pair gives at 600- 750°C the highest growth per cycle of about 0.085 nm. The epitaxially grown tetragonal (cassiterite) films are (1 0 1)- oriented. The iodine contamination in them is below 0.1%. All the film-substrate structures are highly transparent in the visible region.© (2005) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.