Growth Mechanism Of Films Research Articles

A new method to obtain the repassivation time of passive materials based on the single particle impingement

Repassivation time (tre) is a significant parameter when evaluating the repassivation property of material. Herein, we propose a new method to obtain tre by first theoretically unifying the repassivation current–time (i(t)) function for common film growth models, subsequently simplifying the unified i(t) function based on single particle impingement data, then deriving the completed repassivation current expression corresponding to tre using mathematical approximation methods, and finally verifying this method via comparing the obtained tre of three materials. The newly proposed method is reliable, universal and simple to compare repassivation properties of different materials without curve fitting and considering film growth mechanism.

New Materials to Battle the Transistor Interconnect Bottleneck

With ever decreasing transistor size, materials that combine both diffusion barrier and liner material properties are needed to successfully electroplate Cu and thus beat the current interconnect bottleneck. In order to facilitate coating of high aspect ratio vias, the material should be as thin as possible. One possibility to achieve this is presented in this study, where we investigate through density functional theory, the behavior Cu on Ru-doped and Ru passivated ε-TaN (1 1 0). Initially, the adsorption, diffusion and association of one and two Cu atoms on the different surfaces was studied in order to probe the early stages of film growth. This showed that, while surface diffusion of atoms was more favourable on the Ru-passivated surface, the Ru dopant acts as a nucleation site for Cu, with atoms preferentially diffusing towards it.In order to understand the mechanism of film growth on this surface in more detail and to fine-tune the barrier and liner properties of the material, the effect of different percentages of surface doping were studied. Further, the behavior of Cu13 and Cu29 clusters on different doped surfaces and on the passivated surfaces was investigated. In particular, the study focused on the pathways toward agglomeration as well as the associated activation energies. We find that on a Ru doped surface the atoms agglomerate spontaneously to form a two-layer film, whereas they remain in a monolayer on Ru-passivated TaN (1 1 0).

Method of Surface Energy Investigation for Nanostructured Materials: Application to Control NiFe Films Growth Mechanism

Method of Surface Energy Investigation for Nanostructured Materials: Application to Control NiFe Films Growth Mechanism

Step-confined thin film growth via near-surface atom migration

Understanding of thin film growth mechanism is crucial for tailoring film growth behaviors, which in turn determine physicochemical properties of the resulting films. Here, vapor-growth of tungsten carbide overlayers on W(110) surface is investigated by real time low energy electron microscopy. The surface growth is strongly confined by surface steps, which is in contrast with overlayer growth crossing steps in a so-called carpet-like growth mode for example in graphene growth on metal surfaces. Density functional theory calculations indicate that the step-confined growth is caused by the strong interaction of the forming carbide overlayer with the substrate blocking cross-step growth of the film. Furthermore, the tungsten carbide growth within each terrace is facilitated by the supply of carbon atoms from near-surface regions at high temperatures. These findings suggest the critical role of near-surface atom diffusion and step confinement effects in the thin film growth, which may be active in many film growth systems.

Plasma‐initiated chemical vapour deposition of organosiloxane thin films: From the growth mechanisms to ultrathin low‐k polymer insulating layers

AbstractThe growth mechanisms of low dielectric constant polymer thin films elaborated from the atmospheric‐pressure plasma‐initiated chemical vapour deposition (AP‐PiCVD) reaction of a cyclic vinyl organosiloxane are experimentally elucidated in this study. The use of ultrashort plasma pulses (ca. 100 ns), as a polymerisation initiator, with long plasma off‐times results in the formation of atomically smooth thin films. The increase of the monomer saturation ratio, PM/Psat, results in an increase in the growth rate and a better retention of the cyclic structure of the monomer, promoting lower dielectric constants. Based on this experimental study, guidelines are provided to determine the optimal process window for the AP‐PiCVD of functional polymer thin films.

Plasma polymerization of cyclopropylamine in a low-pressure cylindrical magnetron reactor: A PIC-MC study of the roles of ions and radicals

A study of plasma polymerization of cyclopropylamine in a low-pressure cylindrical magnetron reactor is presented. Both experimental and numerical approaches are used to investigate thin film growth mechanisms and polymer film properties depending on the magnetic field strength. Combining both approaches enables the consistency of the numerical model to be checked while acquiring data for understanding the observed phenomena. Samples are first analyzed by x-ray photoelectron spectroscopy, time of flight secondary ion mass spectrometry, and ion beam analysis to illustrate the differences in degrees of chemical functionalization and cross-linking between the regions of high and low magnetic fields. 3D particle-in-cell Monte Carlo collision simulations are then performed to shed light on experimental results, after implementing a set of electron-cyclopropylamine collision cross sections computed using the R-matrix method. The simulations enable the main radicals produced in the discharge to be tracked by determining their production rates, how they diffuse in the plasma, and how they absorb on the reactor walls. Additionally, the cyclopropylamine ion (C3H7N+) behavior is followed to bring insights into the respective roles of ions and radicals during the plasma polymerization process.

Towards a better understanding of the oxide film growth mechanism in E110 zirconium alloy under high-temperature oxidation in steam

AbstractHigh-temperature oxidation of E110 (Zr-1%Nb) zirconium alloy in steam at Т = 1100°C to various degrees has been carried out. Based on the studies of morphology and microstructure of the oxide film and metal, as well as on review of previously published results, the mechanism of alloy oxidation has been proposed, which includes oxide thickening close to the oxide/metal interface, growth of the thickened areas and their conversion into nodules, growth of the nodules and crowning of the metal surface (white spots), clustering of nodules under the formed oxide, formation of a double (white on the surface) oxide film and delamination of the oxide upper layer.

Passivation effect of zinc oxide thin films with temperature on Si (100) substrate by atomic layer deposition

ABSTRACTThe thin film growth behavior and mechanism of ZnO grown by atomic layer deposition (ALD) on Si (100) substrate was using diethylzinc (DEZn) and H2O as the zinc and oxygen sources, resperctively. The preferred orientation of ZnO on the Si (100) substrate was changed from (002) to (100). We suggest a hypothesis on the mechanism of preferred orientation change during ZnO deposition. This phenomenon seemed to play a major role in the vertical growth of (001) plane parallel to the substrate, which resulted in (002) preferred orientation growth of the ZnO films at low temperature regions. At high temperatures, the ethyl fragments further decomposed and desorbed from the surface. Therefore, the passivation effect disappeared and suppression of (002) growth was no longer possible. The microstructure evolution of ZnO was investigated by using a field emission scanning electron microscope (FeSEM) and x-ray diffraction (XRD).

Exploring Bi3+ distribution characteristics of MAPbxBi1-xBr3 thin films by space-limited method

There is always a surge of interest in compositional engineering to improve the performance of organic–inorganic halide perovskite (OIHP) solar cells among research communities. However, the role of dopant in OIHPs has not been clearly clarified so far. Relying on the slow growth of spaced-limited method, crystallization details of OIPH thin films can be amplified to explore the dopant distribution behavior easily. Herein, we optimized preparation conditions of spaced-limited method, and then conducted Bi3+ incorporation into MAPbBr3 single-crystalline thin films (SCTFs) to further explore its impacts from another angle. PTAA-modified substrate surfaces could accelerate the diffusion of precursor ions in the slit, which facilitated to obtain large area OIPH thin films. After Bi3+ incorporation, it’s easy to find that Bi3+ could gradually aggregate on the top surface of MAPbxBi1-xBr3 thin films to form a layer of brown materials (MAPbBr3 crystal grains containing high Bi3+ content). As Bi3+ concentration increased in precursor solution, Bi3+-based perovskite (MA3Bi2Br9) would finally separate. Bi3+ distribution behavior and growth mechanism of MAPbxBi1-xBr3 thin films can give more enlightenment for understanding the role of dopant ions in OIHPs for applications in modern electronics.

Precipitation Behavior of Laves Phase in the Vicinity of Oxide Film of Ferritic Stainless Steel: Selective Oxidation-Induced Precipitation

Anti-corrosion behavior of Fe–Cr alloys at elevated temperature is greatly influenced by the protective nature of oxide scale formed on them. However, precipitates formed underneath the scale can affect the diffusion of reactive elements, growth mechanism and failure mechanism of oxide film. Here, we elucidate the precipitation mechanism of Laves phase in the vicinity of oxide film during oxidation at 950–1050 °C in air. Two types of automotive exhaust manifold-used ferritic stainless steels were designed by replacing Mo with different contents of W and adding small content of Ce. By systematic investigations of the precipitates in the vicinity of steel/oxide interface, we conclude that Laves phase precipitated near the oxide film is related to the selective oxidation of chromium, which is dramatically different from conventional precipitation mechanism. Nb was localized at the interface due to rejection from the growing Cr2O3 scale, which promoted the formation of Laves phase. The experimental steels were characterized by excellent oxidation resistance and Ti–rich oxide formed in the internal oxidation zone that hindered the further diffusion of oxygen.

Facile Au-assisted epitaxy of nearly strain-free GaN films on sapphire substrates.

The nearly strain-free GaN films were epitaxially grown successfully on the Au-coated c-plane sapphire substrate by a convenient chemical vapor deposition approach. The growth of GaN single crystalline epitaxial films is a self-patterned process. The morphology, structure, compositions and optical properties of as-synthesized GaN materials were characterized through field-emission scanning electron microscopy, atomic force microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, energy dispersive spectroscopy mapping, Raman spectroscopy and photoluminescence spectroscopy. The characterization results confirm that the epitaxial GaN films grown on Au-coated c-plane sapphire substrates have a single-crystalline and nearly strain-free structure, and exhibit strong UV emission. A possible growth mechanism of the GaN film is proposed: Au-assisted vapor deposition initiates the nucleation of the GaN seeds, and then these seeds grow into inclined inverted hexagonal GaN pyramids with a threefold azimuthal symmetry and vertical inverted hexagonal pyramids; and subsequently, the vertical inverted hexagonal pyramids expand laterally and annihilate the inclined inverted hexagonal pyramids; eventually these vertical pyramids coalesced to form nearly strain-free GaN films. This synthesis strategy provides a new idea for the simple self-patterned growth of nearly strain-free GaN epitaxial films on Au-coated sapphire substrates, and will promote broader applications in GaN-based electronic and optoelectronic devices.

Effect of NaClO disinfection/cleaning on passive films on AISI 316L

316 L stainless steel samples were passivated in NaClO containing solutions in order to simulate disinfection processes. Passive films were grown at the open circuit potential by immersion in NaClO aqueous solutions at different concentrations and temperature in order to understand how exposure to aggressive environments could affect subsequent corrosion resistance of SSs. In the attempt to study the passive film growth mechanism, in-situ Open Circuit Potential measurements were performed in the same growth solutions. Photoelectrochemical and impedance investigation of passive films was carried out in order to link their solid state properties with their corrosion behaviour.

In vacuostudies on plasma-enhanced atomic layer deposition of cobalt thin films

Plasma-enhanced atomic layer deposition (PE-ALD) of cobalt (Co) using cyclopentadienylcobalt dicarbonyl [CpCo(CO)2] combined with hydrogen, nitrogen, ammonia, and argon based plasma gases was investigated. The utilized ALD tool was clustered to an ultrahigh vacuum analytic system for direct surface analyses including X-ray photoelectron spectroscopy (XPS). The combination with a nondestructive surface analysis system enabled a sample transfer without vacuum break and thereby a direct qualification and quantification of the chemical surface composition under quasi in situ conditions. The authors studied the influence of process parameters (e.g., pulse times, plasma power, and substrate temperature) on film compositions and film properties. The occurrence and prevention of sputtering effects due to ion bombardment at high plasma powers were discussed. Beyond those results, precise information about the impact of different plasma gas compositions on the resulting film properties was obtained. Cobalt films grown using a hydrogen/nitrogen (H2/N2) plasma as a coreactant showed a stable film composition (CoNx) with a high Co content of 75 at. %. Using scanning electron microscopy and four point probe measurements, a moderate electrical resistivity of about 56 μΩ cm was calculated for a 20 nm film. The high sensitivity of in vacuo XPS measurements allowed investigations of interface reactions for a single PE-ALD pulse as well as investigations of the initial film growth mechanisms. The nucleation of CoNx films during PE-ALD using H2/N2 plasma as a coreactant was investigated on several substrate materials by XPS. After the very first cycle of the PE-ALD process, no Co could be detected on all the investigated substrates. XPS revealed that the plasma pulse was needed to provide active binding sites for the adsorption reaction of precursor molecules due to the formation of Si-Nx or Si-NxOy surfaces. Therefore, the plasma pulse plays an important role in the PE-ALD process of Co on silicon surfaces. The early cycles were characterized by the onset of Co—O bonds. The homogeneous film body on all substrates consisted of Co-nitride compounds.

Growth of corrosion product film on 12Cr1MoV steel in sulfur-containing sodium aluminate solution

The growth mechanism of product film on steel surface in sulfur-containing sodium aluminate solution was studied with relevance to processing of high-sulfur bauxite ores in Bayer process. Scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), X-ray diffraction (XRD), potentiodynamic polarization curves and electrochemical impedance spectroscopy (EIS) were used to study the growth of corrosion product film on 12Cr1MoV steel in sodium aluminate solution containing 5 g/L S2– and 3 g/L S2O2– 3. Results indicated that the corrosion rate gradually decreased with increasing corrosion time (t). The fitted corrosion rate equation was V = 4.365t–0.809. The corrosion resistance was highest after 5 d. The growth evolution of the product film was divided into three stages: film formation, film conversion and film growth. The final corrosion product film comprised an inner film layer mainly composed of Fe3O4 and an outer film layer mainly composed of FeS, FeS2 and Fe2O3.

The surface morphology evolution of ZrSi2 films under different substrate temperature

Zr silicide (ZrSi2) films fabricated by the electron beam deposition (EBD) under different substrates temperature for the potential applications in the field of integrated circuit manufacturing. The surface morphology evolution of ZrSi2 films under different substrate temperature are characterized by scanning electron microscope (SEM), x-ray photoelectron spectroscopy (XPS) and the electron back-scattered diffraction (EBSD). The sheet resistance of ZrSi2 films are detected by the four-point probe method. In fact, the growth mechanism and physical proprieties of ZrSi2 films synthesized under such conditions are not clear. The work in this article can lead to the further understanding of the synthesis process of the ZrSi2 films. Consequently, more basic work need to be carried out for the future systematic researches.

Enhanced flux pinning isotropy by tuned nanosized defect network in superconducting YBa2Cu3O6+x films

Striving to improve the critical current density Jc of superconducting YBa2Cu3O6+x (YBCO) thin films via enhanced vortex pinning, the interplay between film growth mechanisms and the formation of nanosized defects, both natural and artificial, is systematically studied in undoped and BaZrO3 (BZO)-doped YBCO thin films. The films were grown via pulsed laser deposition (PLD), varying the crystal grain size of the targets in addition to the dopant content. The microstructure of the PLD target has been observed to have a great impact on that of the deposited thin films, including the formation of vortex pinning centers, which has direct implications on the superconducting performance, especially on the isotropy of flux pinning properties. Based on experimentally measured angular dependencies of Jc, coupled with a molecular dynamics (MD) simulation of flux pinning in the YBCO films, we present a quantitative model of how the splay and fragmentation of BZO nanorods artifically introduced into the YBCO film matrix explain the majority of the observed critical current anisotropy.

Oxidation of metal thin films by atomic oxygen: A low energy ion scattering study

In this study, we combine low-energy ion scattering (LEIS) static and sputter depth profiles for characterization of the oxidation kinetics on Zr, Mo, Ru, and Ta films of various thicknesses, followed by exposure to atomic oxygen at room temperature (∼20 °C). A method for nondestructive determination of the oxide growth rate via LEIS static depth profiling (static DP) is presented in detail. This method shows high sensitivity to the oxide thickness formed, and the results are in agreement with those obtained by X-ray reflectometry and sputter depth profiling (sputter DP). Sequential exposures of oxygen isotopes in combination with LEIS sputter DP are applied to elucidate the growth mechanism of the oxide films. The results indicate that the oxidation kinetics at the applied experimental conditions is directly influenced by the metal work function, characterizing a Cabrera-Mott growth type. The maximum thickness of the formed oxide and oxide growth rate are in the order Zr ≈ Ta > Mo > Ru. The combining of analysis by LEIS static DP and isotope tracing sputter DP is decisive in the characterization of oxidation kinetics in the room temperature regime.

Growth Mechanisms and the Effects of Deposition Parameters on the Structure and Properties of High Entropy Film by Magnetron Sputtering.

Despite intense research on high entropy films, the mechanism of film growth and the influence of key factors remain incompletely understood. In this study, high entropy films consisting of five elements (FeCoNiCrAl) with columnar and nanometer-scale grains were prepared by magnetron sputtering. The high entropy film growth mechanism, including the formation of the amorphous domain, equiaxial nanocrystalline structure and columnar crystal was clarified by analyzing the microstructure in detail. Besides, the impacts of the important deposition parameters including the substrate temperature, the powder loaded in the target, and the crystal orientation of the substrate on the grain size and morphology, phase structure, crystallinity and elemental uniformity were revealed. The mechanical properties of high entropy films with various microstructure features were investigated by nanoindentation. With the optimized grain size and microstructure, the film deposited at 350 °C using a power of 100 W exhibits the highest hardness of 11.09 GPa. Our findings not only help understanding the mechanisms during the high entropy film deposition, but also provide guidance in manufacturing other novel high entropy films.

Dynamics Contributions to the Growth Mechanism of Ga2O3 Thin Film and NWs Enabled by Ag Catalyst.

In the last few years, interest in the use of gallium oxide (Ga2O3) as a semiconductor for high power/high temperature devices and UV nano-sensors has grown. Ga2O3 has an enormous band gap of 4.8 eV, which makes it well suited for applications in harsh environments. In this work, we explored the effect of Ag thin film as a catalyst to grow gallium oxide. The growth of gallium oxide thin film and nanowires can be achieved by heating and oxidizing pure gallium at high temperatures (~1000 °C) in the presence of trace amounts of oxygen. We present the results of structural, morphological, and elemental characterization of the β-Ga2O3 thin film and nanowires. In addition, we explore and compare the sensing properties of the β-Ga2O3 thin film and nanowires for UV detection. The proposed process can be optimized to a high scale production Ga2O3 nanocrystalline thin film and nanowires. By using Ag thin film as a catalyst, we can control the growth parameters to obtain either nanocrystalline thin film or nanowires.

On the growth of Co-doped BaFe2As2 thin films on CaF2

The competition between phase formation of BaF2 and Ba(Fe1−xCox)2As2 on CaF2 single crystals has been analysed. Ba(Fe0.92Co0.08)2As2 thin films have been deposited by pulsed laser deposition. X-ray diffraction, atomic force microscopy and scanning electron microscopy studies have revealed that the formation of secondary phases and misorientations as well as the growth modes of the Ba(Fe0.92Co0.08)2As2 thin films strongly depend on the growth rate. At high growth rates, formation of BaF2 is suppressed. The dependency of the Ba(Fe0.92Co0.08)2As2 lattice parameters supports the idea of fluorine diffusion into the crystal structure upon suppression of BaF2 formation similar as was proposed for FeSe1−xTex thin films on CaF2. Furthermore, a growth mode transition from a layer growth mechanism to a three-dimensional growth mode at high supersaturation has been found, suggesting similarities between the growth mechanism of iron-based superconductors and high-Tc cuprate thin films.