Growth Of Oxide Thin Films Research Articles

Effects of Sputter Parameters on Electrochromic Properties of Tungsten Oxide Thin Films Grown by RF Sputtering

Abstract The electrochromic properties of tungsten oxide films grown by RF sputtering were investigated. Among the sputterparameters, first the Ar:O 2 ratios were controlled with division into only an O 2 environment, 1:1 and 4:1. The structure of eachfilm prepared by these conditions was studied by X-ray diffraction, X-ray photoelectron spectroscopy and Rutherfordbackscattering spectroscopy. The sputter-deposited tungsten oxide films had an amorphous structure regardless of the Ar:O 2 ratios. The chemical compositions, however, were different from each other. The stoichiometric structure and low-density filmwas obtained at higher O 2 contents. Electrochemical tests were performed by cyclic voltammetry and chronoamperometry at0.05 M H 2 SO 4 solutions. The current density and charge ratio was estimated during the continuous potential and pulse potentialcycling at − 0.5 V and 1.8 V, respectively. The film grown in a higher oxygen environment had a higher current density anda reversible charge reaction during intercalation and deintercalation. The in-situ transmittance tests were performed by He-Nelaser (633 nm). At higher oxygen contents, a big transmittance difference was observed but the response speed was too slow.This was likely caused by higher film resistivity. Furthermore, the effect of sputtering pressure was also investigated. Thestructure and surface morphology of each film was observed by X-ray diffraction and scanning electron microscopy. A roughsurface was observed at higher sputtering pressure, and this affected the higher transmittance difference and coloration efficiency.Key wordstungsten oxide, RF sputtering, electrochromism.

Negative ions: The overlooked species in thin film growth by pulsed laser deposition

Plasma plume species from a ceramic La0.4Ca0.6MnO3 target were studied by plasma mass spectrometry as a function of laser fluence, background gas, and deposition pressure to understand the interplay between plasma composition and oxide thin film growth by pulsed laser deposition. The plume composition reveals a significant contribution of up to 24% of negative ions, most notably using a N2O background. The significance of negative ions for thin film growth is shown for La0.4Ca0.6MnO3 films grown in different background conditions where the best structural properties coincide with the largest amount of negative plasma species.

Phase‐controlled epitaxial growth of iron oxide thin films on MgO(001) and LaAlO3(001) substrates

AbstractWe have deposited epitaxial iron oxide thin films on MgO(001) and LaAlO3(LAO)(001) substrates, resulting in different phase stabilities. Atomic force microscopy images revealed a smooth surface. Detailed X‐ray diffraction (XRD) measurements were performed to confirm the epitaxial growth and to analyze the atomic growth configuration. We found that (00l) oriented γ‐Fe2O3 was the stable phase on MgO(001) substrates, whereas $ (1\bar 102) $ oriented α‐Fe2O3 was stable on LAO(001). Magnetic hysteresis loop measurements revealed typical ferrimagnetic behavior for γ‐Fe2O3 on MgO, whereas the magnetization of α‐Fe2O3 on LAO was relatively small and consistent with an antiferromagnetic order. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Evaluation of Acceptor Binding Energy of Nitrogen-Doped Zinc Oxide Thin Films Grown by Dielectric Barrier Discharge in Pulsed Laser Deposition

In this research, nitrogen (N)-doped zinc oxide (ZnO) thin films have been grown on a sapphire substrate by dielectric barrier discharge (DBD) in pulsed laser deposition (PLD). DBD has been used as an effective way for massive in-situ generation of N-plasma under conventional PLD process conditions. Low-temperature photoluminescence spectra of N-doped ZnO thin films provided near-band-edge emission after a thermal annealing process. The emission peak was resolved by Gaussian fitting and showed a dominant acceptor-bound excitation peak () that indicated acceptor doping of ZnO with N. The acceptor binding energy of the N acceptor was estimated to be approximately 145 MeV based on the results of temperature-dependent photoluminescence (PL) measurements.

Structural Characterization of Bismuth Zinc Oxide Thin Films Grown by Plasma-Assisted Molecular Beam Epitaxy

We report the structural characterization of thin films grown on c-plane sapphire substrates by plasma-assisted molecular beam epitaxy. By increasing the Bi flux during the growth process, thin films with various Bi contents (x

Catalytic growth of ZnO nanostructures by r.f. magnetron sputtering

The catalytic effect of gold seed particles deposited on a substrate prior to zinc oxide (ZnO) thin film growth by magnetron sputtering was investigated. For this purpose, selected ultra thin gold layers, with thicknesses close to the percolation threshold, are deposited by thermal evaporation in ultra high vacuum (UHV) conditions and subsequently annealed to form gold nanodroplets. The ZnO structures are subsequently deposited by r.f. magnetron sputtering in a UHV chamber, and possible morphological differences between the ZnO grown on top of the substrate and on the gold are investigated. The results indicate a moderate catalytic effect for a deposited gold underlayer of 4 nm, quite close to the gold thin film percolation thickness.

Zinc Oxide Thin Films Grown on Nanostructured Al Thin Layer/Glass Substrate by RF Magnetron Sputtering

ZnO films were deposited on nanostructured Al (n-Al) /glass substrate by RF magnetron sputtering. The results shows that the relation (I (002) /I (100) ≈ I annealed (002)/I annealed (100) ≈1.1) shows the rough n-Al surface is suitable for the growth of a-axis orientation. Meanwhile, the influences of substrate roughness, crystallinity and (101) plane of ZnO film deposited on n-Al layer have been discussed. XPS implies more oxygen atoms are bound to Aluminum atoms, which result in the increase of high metallic Zn in the film.

Effects of the substrate temperature on the deposition of thin SiOx films by atmospheric pressure microwave plasma torch (TIA)

The effect of surface temperature on the deposition of silicon oxide (SiOx) films with a non-thermal microwave axial injection torch (TIA) was investigated in an open air reactor. Argon was used as plasma gas and hexamethyldisiloxane (Si2O2C6H18) as silicon precursor. The parametric study reported here focuses on the influence of the substrate temperature on the morphological and chemical properties of the films deposited in the interval [0°C–130°C]. A similar effect of low and high surface temperature on the deposition process and on the microstructure of the deposited films was highlighted. Macroscopically, particles were promptly produced in the gas phase and incorporated to the film, which generates high surface roughness. Microscopically, FTIR results have shown a high carbon contamination of the deposited films at low and high temperatures, resulting in understoichiometric SiOx films. They have also demonstrated that an optimum growth window for smooth and particle free SiOx was to keep the surface temperature between 30 and 60°C. Simple reaction mechanisms for powder formation and continuous silicon oxide thin films growth are suggested for each temperature ranges.

Accurate measurement of deposition rates for growth of Bi‐based oxide thin films

AbstractBi‐based oxide thin films are important superconducting materials because of its wide applicability, high transition temperatures, and low toxicity. To achieve high quality Bi‐based oxide thin films by molecular beam epitaxy (MBE), the composition is a key parameter. Here, Bi, Cu, Cu/Sr and Cu/Ca thin films on glass substrates prepared by MBE have been examined by using both X‐ray reflectivity and surface profiler. The thickness and surface roughness were obtained through calculation and simulation. In comparison with the film thicknesses measured by these two methods, they are in good agreement. The lines of thickness deposition rate (R) versus source temperature (T) are according with LogR=a+b/T based on Clausius‐Clapeyron equation. Moreover, the Bi2.1CaySr1.9‐yCuO6+δ thin films with different composition and thickness were successfully prepared by MBE by applying the thickness deposition rate lines. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Stability Study of a Magnesium β-Diketonate As Precursor for Chemical Vapor Deposition of MgO

On the basis of the study of the thermal behavior of [Mg(tmhd)2(TMEDA)] (1; tmhd =2,2,6,6-tetramethyl-3,5-heptanedionate; TMEDA = N,N,N′,N′-tetramethylethylenediamine), a novel procedure for magnesium oxide thin film growth has been developed for chemical vapor deposition (CVD) applications. Complementary studies (thermogravimetric measurements and IR and NMR spectroscopy) enabled revelation of the dissociation of TMEDA from 1, confirmed by the detection of both free TMEDA in the vapor phase and less volatile [Mg2(tmhd)4] (2) as a residue after sublimation. The effect of this dissociation is an unwanted changeable sublimation rate of the precursor 1 during the CVD process. The endeavor of a constant deposition rate by simultaneously exploiting the good volatility of 1 was achieved through its synthesis in situ by using 2 with a diamine enriched carrier. Laser reflectance interferometry (LRI) measurements testified that such a method ensured a good and constant deposition rate throughout the growth experim...

Interactions between tri-methylaluminum molecules and their effect on the reaction of tri-methylaluminum with an OH-terminated Si (0 0 1) surface

We studied the interaction between tri-methylaluminum (Al(CH 3) 3, TMA) molecules and their effect on TMA reactions with a fully OH-terminated Si (0 0 1) surface for initial aluminum oxide thin-film growth using density functional theory. The reaction between an adsorbed TMA and the surface produced a di-methylaluminum (–Al(CH 3) 2, DMA) group, and further reaction to a uni-methylaluminum (–AlCH 3, UMA) group with energy barriers of 0.50 and 0.21 eV, respectively. A second TMA adsorbed near the already adsorbed TMA, DMA, or UMA group showed higher energy barriers (0.68–1.01 eV) for its reaction to produce a DMA group due to the interaction between them. Therefore, the fully OH-terminated Si (0 0 1) surface would be covered by the mixture of the adsorbed TMA and UMA groups at an intermediate surface temperature.

ChemInform Abstract: Laser Ablation and Thin Film Deposition

AbstractReview: 99 refs.

Optimised pulsed laser deposition of ZnO thin films on transparent conducting substrates

The growth of polycrystalline zinc oxide (ZnO) thin films by pulsed laser deposition (PLD) on indium tin oxide (ITO) is reported. For the first time the influence of deposition temperature over an extended range (50–650 °C) is investigated on ITO. We describe the role of temperature on the optical and crystalline properties of the deposited films, of 120–250 nm thickness. Additionally, the effect of the background oxygen pressure is reported. Under all of the deposition conditions highly textured c-axis oriented, transparent (>85%) and low roughness (RMS < 10 nm) ZnO films are formed. Growth temperatures ≥450 °C lead to the highest degree of crystallinity and film quality with measured full width half maximum (FWHM) of X-ray diffraction (XRD) peaks as small as 0.14°2θ. XRD measurements of films grown at <350 °C show a shift in the (002) diffraction peak to lower 2θ values, indicating that the deposited films are oxygen deficient. Increasing the oxygen pressure results in the preparation of stoichiometric films at temperatures as low as 50 °C. We demonstrate that in addition to forming high quality ZnO, the optical and electronic properties of ITO can be preserved—even at high temperature—presenting a methodology for preparing highly crystalline ZnO on ITO over a temperature window significantly larger than that of previous literature reports. Furthermore, the low temperature processing opens up the possibility of deposition on a wide range of substrates, especially those unsuitable for exposure to high temperatures.

Effect of Oxygen Pressure on the Initial Oxidation Behavior of Cu and Cu-Au Alloys

ABSTRACTA wide information gap exists between our present atomic-scale knowledge of metal oxidation derived from conventional ultrahigh vacuum (UHV) surface science experiments and the oxidation mechanisms obtained from the growth of bulk oxide thin films under technologically relevant realistic (or near-) atmospheric conditions. To bridge this pressure gap, we present an in-situ transmission electron microscopy (TEM) study of the initial oxidation stage of Cu(100) and Cu-Au(100) surfaces where the oxygen partial pressure varies from 5x10-4 to 150 Torr. For Cu(100), with increasing oxygen partial pressure (pO2), the nucleation density of the oxide islands increases and so does the growth rate of the oxide islands. As the pO2 continues to increase, a transition from epitaxial cube-on-cube Cu2O islands to randomly oriented oxide islands is observed. A kinetic model based on the classic heterogeneous nucleation theory is developed to explain the effect of oxygen partial pressure on the oxide orientation. It is shown that such a transition in the oxide nucleation orientation is related to the effect of oxygen pressure on the nucleation barrier and atom collision rate. The Cu-Au(111) alloy revealed the same oxygen pressure dependency of the oxide nucleation orientation as pure Cu oxidation.

Facile on-demand oriented growth of perovskite oxide thin films: applications of Dion–Jacobson phase as seed layer

We investigated a new fabrication process for high-quality, uniaxial-oriented grown Dion–Jacobson perovskite (DJP) RbLaNb2O7 thin films by means of excimer laser assisted metal organic deposition. Oriented crystal growth occurred only by excimer laser irradiation in air at 400 °C after a deposition of metal–organic solution and preheating at 400 °C. The obtained RbLaNb2O7 thin film showed perfect (010)-oriented growth on borosilicate glass substrates, and the film surface had atomically flat terraces. We confirmed that the obtained DJP RbLaNb2O7 thin films functioned very well as a seed layer for the fabrication of various perovskite oxide thin films with high orientation quality. An oriented grown LaNiO3 thin film fabricated on the DJP seed layer and prepared at 400 °C exhibited low electrical resistivity at room temperature. Moreover, we demonstrated the utility of our methodology for on-demand fabrication by combining our method with an inkjet printing technique to pattern LaNiO3 thin films with a line shape, which also were successfully grown with uniaxial orientation on the DJP seed layer. A ferroelectric Na0.5K0.5NbO3 perovskite film was heteroepitaxially grown on the uniaxial-oriented grains of the LaNiO3/RbLaNb2O7 thin film, and this oriented film exhibited a higher dielectric constant than that of a film fabricated without the DJP seed layer. Thus, we demonstrated facile, oriented crystal growth enabled by the uniaxial-oriented DJP seed layer.

Reaction of Tri-methylaluminum on Si (001) Surface for Initial Aluminum Oxide Thin-Film Growth

We studied the reaction of tri-methylaluminum (TMA) on hydroxyl (OH)-terminated Si (001) surfaces for the initial growth of aluminum oxide thin-films using density functional theory. TMA was adsorbed on the oxygen atom of OH due to the oxygen atom’s lone pair electrons. The adsorbed TMA reacted with the hydrogen atom of OH to produce a di-methylaluminum group (DMA) and methane with an energy barrier of 0.50 eV. Low energy barriers in the range of 0 - 0.11 eV were required for DMA migration to the inter-dimer, intra-dimer, and inter-row sites on the surface. A unimethylaluminum group (UMA) was generated at each site with low energy barriers in the range of 0.21 - 0.25 eV. Among the three sites, the inter-dimer site was the most probable for UMA formation.

Zinc Oxide Thin Films Grown by RF Magnetron Sputtering on Nanostructure Al Thin Layer/Glass and Glass Substrates

ZnO films with random and highly (002)-preferred orientation were deposited on nanostructured Al (n-Al) /glass and glass substrates at room temperature by RF magnetron sputtering method, respectively. According to I (002)/I (100) ≈I annealed (002)/I annealed (100) ≈1.1 (on n-Al) and 2I annealed (002) /I (002) (on n-Al) ≈ I annealed (002) /I (002) (on glass) ≈3.1, the rough n-Al surface is suitable for the growth of a-axis orientation, and the appearance of the (100) peak plays a major role in decreasing the c-axis orientation. The average optical transmission of the film on n-Al layer increased significantly after annealing. At the same time, the growth mode and E g of ZnO films were discussed. On n-Al layer/glass substrate, it is not easy for the growth interface to form the smooth surface during the deposition process and Stranski Krstanov plays a primary role on the deposition of the films. Due to the significant increase of the interplanar spacing d (101), the band gaps for as-grown and annealed films grown on n-Al decreased, comparing with that of the film deposited on glass substrate.

Growth and characterization of zirconium oxide thin films on silicon substrate

The growth and characterization of zirconium oxide (ZrO 2) thin films prepared by thermal oxidation of a deposited Zr metal layer on SiO 2/Si were investigated. Uniform ZrO 2 thin film with smooth surface morphology was obtained. The thermal ZrO 2 films showed a polycrystalline structure. The dielectric constant of the ZrO 2 film has been shown to be 23, and the equivalent oxide thickness (EOT) of the ZrO 2 stacked oxide is in the range of 3.38–5.43 nm. MOS capacitors with ZrO 2 dielectric stack show extremely low leakage current density, less than 10 −6 A/cm 2 at −4 V. Consequently, using this method, high-quality ZrO 2 films could be fabricated at oxidation temperature as low as 600 °C.

Molecular Mechanisms of Aluminum Oxide Thin Film Growth on Polystyrene during Atomic Layer Deposition

One layer at a time: A proposed growth mechanism of Al2O3 atomic layer deposition on a polystyrene surface is presented. The infiltration of trimethylaluminum and H2O precursors may result in Al2O3 growth in the polystyrene matrix (subsurface), thus forming a hybrid interface (shown in the green box) of C8H7O− and C6H4O2Al− ions.

The origin of oxygen in oxide thin films: Role of the substrate

During the growth of oxide thin films by pulsed laser deposition, a strong oxygen substrate-to-film transfer has been experimentally observed for SrTiO3 and LaAlO3 thin films epitaxially grown on O18 exchanged SrTiO3 and LaAlO3 substrates by secondary ion mass spectrometry depth profiling. This oxygen transfer effect can seriously change the respective thin film properties. Taking the oxygen substrate contribution to the overall oxygen balance into account, original ways to design material properties of oxide thin films can be envisioned like a controlled charge carrier doping of SrTiO3 thin films.