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In this work, the results of ellipsometric studies of thin films of broadband oxides (ZnO, TiO2, ZrO2) and broadband oxides doped with Al2O3 (Al2O3–ZnO, Al2O3–TiO2, Al2O3–ZrO2) are presented. All layers have been produced using the atomic layer deposition method. Ellipsometric studies were performed in the wavelength range of 193–1690 nm. Sellmeier and Cauchy models were used to describe the optical properties of the tested layers. Dispersion dependencies of refractive indices were determined for thin layers of broadband oxides on silicon substrates, and then for layers of Al2O3 admixture. The EDX investigations enabled estimation of the composition of the alloys. The Bruggeman effective medium approximation (EMA) model was used to determine the theoretical dependencies of the dispersion refractive indices of the studied alloys. The refractive index values determined using the Bruggeman EMA model are in good agreement with the values determined from the ellipsometric measurements. The doping of thin layers of ZnO, ZrO2 and TiO2 with Al2O3 enables the creation of anti-reflective layers and filters with a specific refractive index. [ABSTRACT FROM AUTHOR]

This work demonstrated the optimization of HiPIMS reactive magnetron sputtering of hafnium oxynitride (HfOxNy) thin films. During the optimization procedure, employing Taguchi orthogonal tables, the parameters of examined dielectric films were explored, utilizing optical methods (spectroscopic ellipsometry and refractometry), electrical characterization (C-V, I-V measurements of MOS structures), and structural investigation (AFM, XRD, XPS). The thermal stability of fabricated HfOxNy layers, up to 800 °C, was also investigated. The presented results demonstrated the correctness of the optimization methodology. The results also demonstrated the significant stability of hafnia-based layers at up to 800 °C. No electrical parameters or surface morphology deteriorations were demonstrated. The structural analysis revealed comparable electrical properties and significantly greater immunity to high-temperature treatment in HfOxNy layers formed using HiPIMS, as compared to those formed using the standard pulsed magnetron sputtering technique. The results presented in this study confirmed that the investigated hafnium oxynitride films, fabricated through the HiPIMS process, could potentially be used as a thermally-stable gate dielectric in self-aligned MOS structures and devices. [ABSTRACT FROM AUTHOR]

This paper we discusses an effect of coating longperiod gratings (LPGs) with a thin titanium dioxide (TiO2) overlays on refractive index (RI) sensitivity of the LPG. The overlays have been obtained using atomic layer deposition (ALD) method. The method allows for deposition well-controlled in thickness, well defined in optical properties, high-RI and very conformal thin films as required for optical fiber sensors. For the investigated LPGs we obtained sensitivity of 3490 to 6471 nm per RI unit depending on range RI. [ABSTRACT FROM AUTHOR]

Oxide-based thin-film capacitors (TFCs), thin-film transistors (TFTs), and sensor structures (including transparent ones) deposited on transparent substrates are investigated. All oxide elements in these structures are deposited by atomic layer deposition (ALD). Optimization of the ALD processes, which results in layers suitable for the above-mentioned devices, is briefly described. In particular, we demonstrate advantageous properties of composite dielectrics consisting of pairs of Al2O3, HfO2, ZrO2, or TiO2. These composites are then used as gate dielectrics in TFC and TFT structures, with ZnO layers deposited as channel and gate layers. The structures are obtained at low temperatures (no more than 150°C), which enables their deposition on elastic, transparent substrates (polymers, foils). [ABSTRACT FROM AUTHOR]

We discuss properties of thin films of ZnO and ZnMnO grown with atomic layer epitaxy using new, organic zinc and manganese precursors. Several characterization techniques, including X-ray diffraction, atomic force microscopy, scanning electron microscopy, cathodoluminescence, superconducting quantum interfernece device (SQUID) and electron spin resonance, show good topography of the films and their advantageous optical and magnetic properties. [ABSTRACT FROM AUTHOR]

Successful growth of thin films and quantum dots of ZnO by atomic layer deposition (ALD) is reported. Properties of ZnO films produced by four different ALD-procedures and by oxidation of ALD-grown ZnS films are discussed. We also shortly describe the use of thin ZnO films as buffer layers for GaN deposition [ABSTRACT FROM AUTHOR]

The thin layers of ZnO and ZnO: Al (Al doped zinc oxide—AZO) were deposited by the atomic deposition layer (ALD) method on silicon and glass substrates. The structures were deposited using diethylzinc (DEZ) and deionized water as zinc and oxygen precursors. A precursor of trimethylaluminum (TMA) was used to introduce the aluminum dopant. The present study of ALD-deposited ZnO and AZO films was motivated by their applications in photovoltaics. We attempted to expose several properties of such films. Structural, optical (including ellipsometric measurements) and electrical investigations were performed. We discussed the relations between samples doped with different Al fractions and their properties. [ABSTRACT FROM AUTHOR]

The continuous development of ALD thin films demands ongoing improvements and changes toward fabricating materials with tailored properties that are suitable for different practical applications. Ozone has been recently established as a precursor, with distinct advantages over the alternative oxidizing precursors in the ALDs of advanced dielectric films. This study reports alumina (Al2O3) and hafnia (HfO2) formation using an O3 source and compares the obtained structural and electrical properties. The performed structural examinations of ozone-based materials proved homogenous high-k films with less vacancy levels compared to water-based films. The enhanced structural properties also result in the problematic incorporation of different dopants through the bulk layer. Furthermore, analysis of electrical characteristics of the MIS structures with ALD gate dielectrics demonstrated the improved quality and good insulating properties of ozone-based films. However, further optimization of the ALD technique with ozone is needed as a relatively low relative permittivity characterizes the ultra-thin films. [ABSTRACT FROM AUTHOR]

The material BaBiO 3 is known for its insulating character. However, for thin films, in the ultra-thin limit, metallicity is expected because the oxygen octahedra breathing mode will be suppressed as reported recently. Here, we confirm the influence of the oxygen breathing mode on the size of the band gap. The electronic properties of a BaBiO 3 thickness series are studied using in-situ scanning tunneling microscopy. We observe a wide-gap ( E G > 1.2 V) to small-gap ( E G ≈ 0.07 eV) semiconductor transition as a function of a decreasing BaBiO 3 film thickness. However, even for an ultra-thin BaBiO 3 film, no metallic state is present. The dependence of the band gap size is found to be coinciding with the intensity of the Raman response of the breathing phonon mode as a function of thickness. [ABSTRACT FROM AUTHOR]

This paper reports on ZnO/Ag Schottky junctions obtained by the low temperature atomic layer deposition process. Introducing the thin (from 1.25 to 7.5 nm) layer of hafnium dioxide between the ZnO layer and evaporated Ag Schottky contact improves the rectification ratio to about 105 at 2V. For the ZnO/Ag junctions without the HfO2 interlayer, the rectification ratio is only 102. We assign this effect to the passivation of ZnO surface accumulation layer that is reported for ZnO thin films. [ABSTRACT FROM AUTHOR]

Low temperature (at 100 °C and below) growth of ZnO thin films by atomic layer deposition (ALD) is demonstrated. Properties of the layers grown with two different oxygen reagents: ozone and water are compared. Diethylzinc (DEZ) was used as metal precursor. Electrical and structural properties of films obtained at several different growth temperatures, ranging from 50 °C to 250 °C were analyzed. It turned out that the film grown in the water-based process at 250 °C and all films grown with ozone have more ordered crystallographic structure with the privileged growth direction (001) perpendicular to the substrate than water-based samples grown in temperatures 100–200 °C. Higher free electron concentration at room temperature was observed for ozone-based samples grown at 100 °C and 150 °C in comparison to water-based samples obtained at the same growth temperature. Low value of resistivity in case of ozone-based samples grown at 100 °C is a promising result, however lower electron mobility requires further optimization. [ABSTRACT FROM AUTHOR]

• An innovative method of hydrothermal formation of CuO films adopted to MIM structures. • Distinct changes in structural and optical properties of 'as grown' and 'HT + RTP' films observed. • Stability of resistive switching characteristics and larger LRS/HRS ratio of MIM structures with annealed CuO. • Obtained retention approximated to ten years proved the potential application of CuO in RRAM devices. This work presents the preliminary research on Metal-Insulator-Metal (MIM) structures containing copper oxide (CuO) layers for memory applications. Structural and optical investigations of fabricated materials have shown distinct differences in chemical compositions of 'as grown' and thermally annealed CuO, i.e., 'HT + RTP' film. Those differences strongly influence the electrical behavior of fabricated MIM structures. The examined electrical performance of fabricated devices revealed stability and repeatability of the HRS/LRS ratio over time. The presented results have demonstrated the possible application of CuO thin films in low-power and high-speed Resistive Random-Access Memory (RRAM) devices. [ABSTRACT FROM AUTHOR]

Ti-based films are extensively studied as a prospective material for several applications - for UV-protection, antibacterial coating and effective photocatalytic activity. This is because Ti-based TiO 2 shows relatively high reactivity and chemical stability under ultraviolet light (λ < 387 nm), whose energy exceeds the band gap (in the range 3–4 eV) of the anatase crystalline phase. However, the efforts are focused on development of photocatalytic materials exhibiting high reactivity under visible light (λ > 400 nm). Such materials should utilize the main part of the solar spectrum, and if efficient, they should work even under poor illumination, for example upon interior lighting. In this work, we concentrated on optimization of Ti-based films. Films with different chemical compositions were deposited using the atomic layer deposition (ALD) method. These films were prepared using chemical reactions between listed precursors: H 2 O, TiCl 4 , Ti(N(CH 3) 2) 4 and Al 2 (CH 3) 6. The selection of precursors and, consequently, the modification of the ALD Ti-based process allowed the deposition of thin films with quite different structural, optical and electrical properties. [ABSTRACT FROM AUTHOR]

Abstract: This work is focused on the electrical and optical analyses used to estimate the activation energy of the dominant shallow donor in thin ZnO films obtained at low temperature by the atomic layer deposition process. These two approaches, based on the temperature-dependent classical Hall effect and photoluminescence investigations, yielded a donor activation energy E D in the range of 30–40meV, including the estimated error margins. This value, as confirmed by layer composition studies, is attributed to the presence of zinc atoms in the interstitial positions of the ZnO lattice. [Copyright &y& Elsevier]