Growth Mechanism Of Thin Films Research Articles

Self-assembled plasmonics for angle-independent structural color displays with actively addressed black states

Nanostructured plasmonic materials can lead to the extremely compact pixels and color filters needed for next-generation displays by interacting with light at fundamentally small length scales. However, previous demonstrations suffer from severe angle sensitivity, lack of saturated color, and absence of black/gray states and/or are impractical to integrate with actively addressed electronics. Here, we report a vivid self-assembled nanostructured system which overcomes these challenges via the multidimensional hybridization of plasmonic resonances. By exploiting the thin-film growth mechanisms of aluminum during ultrahigh vacuum physical vapor deposition, dense arrays of particles are created in near-field proximity to a mirror. The sub-10-nm gaps between adjacent particles and mirror lead to strong multidimensional coupling of localized plasmonic modes, resulting in a singular resonance with negligible angular dispersion and ∼98% absorption of incident light at a desired wavelength. The process is compatible with arbitrarily structured substrates and can produce wafer-scale, diffusive, angle-independent, and flexible plasmonic materials. We then demonstrate the unique capabilities of the strongly coupled plasmonic system via integration with an actively addressed reflective liquid crystal display with control over black states. The hybrid display is readily programmed to display images and video.

Growth dynamics of pulsed laser deposited WS2 thin films on different substrates

The scaling behavior, as well as growth mechanism of polycrystalline WS2 thin films grown on glass and Si substrates by pulsed laser deposition as a function of the deposition time, has been studied using height–height correlation function using the AFM images. X-ray diffraction measurement confirms the increase in crystallinity of the WS2 thin film on both the substrates. The WS2 films deposited onto Si substrate showed high rate of roughening or interface width (w) and a rapid increase in island size or correlation length (ξ) of WS2 nanoclusters in comparison to the films deposited onto glass substrate. The WS2 films grown on glass substrate evolved following the nonlinear stochastic deposition equation, however, WS2 films on Si substrate follow a linear growth model. The difference in surface smoothness, thermal conductivity and sticking coefficient of the two substrates causes different growth patterns of WS2 films onto the substrates. The growth of the WS2 films on the two different substrates evolved differently which has been realized more conveniently by schematically analyzing the behavior of the evolution of ξ and w with deposition time, t. The high roughness of the films deposited onto oxidized Si provides a large surface area, which will be useful for electro-catalysis applications.

Investigations of ZnO Nanorod Films Grown by Hydrothermal Method for Ethanol Gas Sensor

Rod-structured ZnO has grown hydrothermally on the seed layer by varying growth time. The growth mechanism of rod-structured ZnO thin films is studied extensively with the help of characterizing tools. The preferred orientation and c/a ratio are studied with Grazing Incidence X-ray diffraction (GIXRD). The growth mechanism of ZnO rod structure is studied in detailed manner with Atomic Force Microscopy (AFM) and Field Emission Scanning Electron Microscopy (FESEM). The optical absorption and emission properties of ZnO rods are studied with respect to growth morphology. Ethanol sensing measurements are carried out at room temperature (RT). The nanostructured ZnO films show good response and sensitivity to ethanol gas at RT.

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.

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.

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.

Quantitative Image Analysis of Fractal‐Like Thin Films of Organic Semiconductors

ABSTRACTMorphology modulation offers significant control over organic electronic device performance. However, morphology quantification has been rarely carried out via image analysis. In this work, we designed a MATLAB program to evaluate two key parameters describing morphology of small molecule semiconductor thin films: fractal dimension and film coverage. We then use this program in a case study of meniscus‐guided coating of 2,7‐dioctyl[1]benzothieno[3,2‐b][1]benzothiophene (C8‐BTBT) under various conditions to analyze a diverse and complex morphology set. The evolution of morphology in terms of fractal dimension and film coverage was studied as a function of coating speed. We discovered that combined fractal dimension and film coverage can quantitatively capture the key characteristics of C8‐BTBT thin film morphology; change of these two parameters further inform morphology transition. Furthermore, fractal dimension could potentially shed light on thin film growth mechanisms. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019, 57, 1622–1634

Studying magnetic properties and surface roughness evolution of Ag-Co electrodeposited films

Abstract The effects of thickness on surface roughness and magnetic properties of Ag-Co thin films prepared by electrodeposition technique were studied. Crystalline structural of the films were discussed. The scaling analysis showed that the surface growth of the Ag-Co thin films has an intrinsic anomalous scaling behavior. Meanwhile, the increase in the film thickness decreased coercivity and squareness while it increased local slope. In-plan demagnetizing factor was also enhanced with the film thickness (growth time) as a power-law and its results confirmed our dynamic scaling results. It was found that thin film growth mechanisms and surface roughness can have sturdy effect on magnetic features of thin films.

Growth mechanism of zinc oxide thin film by mist chemical vapor deposition via the modulation of [H2O]/[Zn] ratios

The growth mechanism of ZnO films fabricated via mist CVD was proposed by analyzing the growth rates, crystallinities, surface morphologies, and chemical states of the films that were grown when the precursor material supply amounts were fixed and the H2O concentrations were changed. At appropriate conditions, e.g. [H2O]/[Zn] ≈ 60–70 and [Zn] = 20 mM, high-quality ZnO thin films with a high growth rate, (001) dominant orientation, smooth surface, and low oxygen-related defects were obtained. These conditions provided a sufficient diffusion length for the precursor materials on the surface and an appropriate collision probability for the precursor and oxygen sources.

Multi-scale study of Ti3SiC2 thin film growth mechanisms obtained by magnetron sputtering

In the present work we focus on the mechanisms involved in Ti3SiC2 MAX phase thin-film formation and on the impact of stoichiometry and thickness/element quantity correlation. TiAlx thin-films, with x=0--2, 100–300 nm thick, were deposited by magnetron sputtering on a SiC-4H (0001) substrate. Samples were annealed at 1000 ∘C for 30 min and analyzed by XRD, AFM, SEM and TEM. The MAX phase Ti3SiC2 was formed at 1000 ∘C in accordance with thermodynamic considerations. Moreover, an epitaxial relation between the film and the substrate occurred as follows (0001)MAX//(0001)SiC and [121¯0]MAX//[121¯0]SiC due to the formation of an earlier TiC phase by species interdiffusion. The catalytic role of Al has been demonstrated and explained by the formation of Ti2AlC as precursor for Ti3AlC2 and for Ti3SiC2. Finally, second phases and continuity of films have been controlled by x and thickness factors. Indeed, the MAX phase film continuity is obtained for Al richer films, whereas the purest MAX phase have been synthesized for the thinnest layer of TiAlx deposited.

Synthesis, structure and magnetization of Co4N thin films

Abstract We reviewed magnetic tetra metal nitrides – Fe 4 N and Co 4 N for their structure, magnetization and the thermodynamics of phase formation. Opposed to Fe 4 N , the formation of a stoichiometric Co 4 N turns out to be extremely difficult. A review of the literature of Co 4 N compound suggest that the experimental lattice parameter (LP) was always found to be smaller than the theoretical predicted value. It can also be seen that as the substrate temperature ( T s ) increases, the LP of Co 4 N film decreases. In this work, we deposited Co 4 N films using molecular beam epitaxy (MBE), direct current magnetron sputtering (dcMS) and high power impulse MS (HiPIMS). Films were characterized using X-ray diffraction, X-ray reflectivity and atomic force microscopy. It was found that at high T s , N out-diffusion significantly affects the growth of Co 4 N phase. We found that the MBE deposited films did not show any signature of Co 4 N phase when T s 703 K but at T s = 703 K , the phase formed can be assigned to fcc Co rather than Co 4 N . On the other hand, the dcMS and HiPIMS grown films clearly show the presence of Co 4 N phase even at T s = 300 K . Detailed analysis of Co 4 N films grown using dcMS and HiPIMS reveals that HiPIMS grown films are single phase and have a denser microstructure. The density of HiPIMS deposited film was also found to be close to the theoretical value. Magneto optical Kerr effect and polarized neutron reflectivity measurements were carried out to study magnetic properties. Differences in the magnetic moment and magnetic anisotropy were correlated with structural parameters. Obtained results are presented and discussed in terms of involved thin film growth mechanism.

Influence of substrate temperature on the morphology and structure of bismuth thin films deposited by magnetron sputtering

The melting point of bismuth is only 271.3 °C which has a great influence on the properties of bismuth itself and the bismuth-contained compounds especially at high temperature. In this paper, the bismuth thin films were prepared using magnetron sputtering method and the influence of deposition temperature on the morphology and structure were investigated over a wide range of substrate temperatures from room temperature to near the melting point. The results showed that 160 °C is a main watershed for the film growth. When the substrate temperature is below 160 °C, the morphology changes a lot from continuous film accumulated mainly by irregular grains to the discontinuous film mainly formed from the isolated polyhedral grains and again to the bimodal grain size distribution of the spherical-polyhedron-shape grains. When the substrate temperature is above 160 °C, the morphology of the bimodal grain size distribution has been maintained except for the changes of the large grain size. The XRD results revealed that the crystallite size hardly changes above 160 °C begin which the bimodal grain size distribution is just formed. The morphology evolution and growth mechanism of bismuth thin films were also studied based on the existing structure zone diagram model and our experimental results.

The Concentration Effect of Complexing Agent on the Morphology and Optoelectronic Properties of Electrochemically Deposited n-type Cu2O Thin Films

In this work, copper oxide (Cu2O) n-type semiconductors were synthesized on fluorine-doped tin oxide (FTO)-coated conducting glass substrates using copper acetate electrolyte through potentiostatic electrodeposition. The effect of the concentration of acetic acid (CH3COOH) as a complexing agent on the growth mechanism, structural, morphological, and optical properties of Cu2O thin films were studied. The obtained results showed that the concentration of acetic acid affects the structure, grain size, surface topography and optoelectronic properties of Cu2O films significantly. X-ray diffraction (XRD) revealed that all the Cu2O films are pure and crystallize in cubic structure with high crystanillity and preferred (111) orientation. Both Mott-Schottky (MS) and photocurrent (PC) measurements confirm the n-type conduction of the deposited films and the enhancement of their electrical properties with increasing acetic acid concentration. Atomic Force Microscopy (AFM) showed the variation in surface topography and roughness of the Cu2O films. The band gap (Eg) of the Cu2O films decreased slightly with increasing the acetic acid concentration. The Cu2O films deposited with 0.04 of acetic acid exhibited better overall properties and are suitable for Cu2O based homo-junction.

Growth mechanism of Sb2Se3 thin films for photovoltaic application by vapor transport deposition

Sb2Se3 is a rapidly advancing sustainable thin film solar cell technology demonstrating 9.2% conversion efficiency recently. Because of its unique quasi-1D crystal structure, the orientation of absorbers plays a key role in charged carrier transport and therefore in solar cell performance. However, deeper understanding how deposition conditions affect film orientation and ability to control it are missing. Herein using vapor transport deposition (VTD) method we studied growth process of Sb2Se3 on Mo, MoSe2, CdS, ZnO and TiO2 substrates. We varied the temperature of substrate and source to imitate various growth conditions. We have found three distinct growth regimes at which films exhibit characteristic features. Compact and large grained morphology with explicit (hkl, l≠0) orientation was achieved when high growth rate regime governed by evolution selection principle was induced on all substrates. Proposed growth model takes into account the influence of substrate and provides directions to obtain Sb2Se3 films with desired morphology and orientation. In conclusion, we have compared morphological properties of Sb2Se3 films synthesized by various evaporation based methods in literature with the properties predicted by the model. A fair agreement was found, proposing that this model can serve as a guideline for Sb2Se3 thin film optimization using evaporation based methods.

Effect of deposition rate on the growth mechanism of microcrystalline silicon thin films using very high frequency PECVD

The intrinsic microcrystalline silicon thin films were deposited by very high frequency plasma enhanced chemical vapor deposition (VHF-PECVD). Two series of films with different deposition rate 0.30 nm/s and 1.94 nm/s were prepared. The film surface and gas phase reaction growth processes were monitored with real-time spectroscopic ellipsometry and optical emission spectroscopy. The effect of deposition rate on the microcrystalline silicon thin film growth mechanism has been studied. The microcrystalline silicon surface growth was analyzed with KPZ model. The results show that the growth exponent of β is 0.448 for the films with low deposition rate, and the growth exponent of β is 0.302 for the films with high deposition rate. The growth exponent does not increase with deposition rate, but declines. And the reasons for this phenomenon were explained.

On the Effect of Thin Film Growth Mechanisms on the Specular Reflectance of Aluminium Thin Films Deposited via Filtered Cathodic Vacuum Arc

The optimisation of the specular reflectance of solar collectors is a key parameter to increase the global yield of concentrated solar power (CSP) plants. In this work, the influence of filtered cathodic vacuum arc deposition parameters, particularly working pressure and deposition time, on the specular and diffuse reflectance of aluminium thin films, was studied. Changes in specular reflectance, measured by ultraviolet–visible and near-infrared spectroscopy (UV-vis-NIR) spectrophotometry, were directly correlated with thin film elemental concentration depth profiles, obtained by Rutherford backscattering spectrometry (RBS), and surface and cross-sectional morphologies as measured by scanning electron microscopy (SEM) and profilometry. Finally, atomic force microscopy (AFM) provided information on the roughness and growth mechanism of the films. The two contributions to the total reflectance of the films, namely diffuse and specular reflectance, were found to be deeply influenced by deposition conditions. It was proven that working pressure and deposition time directly determine the predominant factor. Specular reflectance varied from 12 to 99.8% of the total reflectance for films grown at the same working pressure of 0.1 Pa and with different deposition times. This transformation could not be attributed to an oxidation of the films as stated by RBS, but was correlated with a progressive modification of the roughness, surface, and bulk morphology of the samples over the deposition time. Hence, the evolution in the final optical properties of the films is driven by different growth mechanisms and the resulting microstructures. In addition to the originally addressed CSP applications the potential of the developed aluminium films for other application rather than CSP, such as, for example, reference material for spectroscopic diffuse reflectance measurements, is also discussed.