Growth Mechanism Of Films Research Articles

Anodic behavior of zinc in aqueous borate electrolytes

The behavior of zinc in aqueous borate electrolytes at anodic polarization in galvanostatic regime was investigated. Induction periods and voltage breakdown phenomena were observed in the respective kinetic curves. The dependence of the duration of these induction periods on the polarization conditions (j = 5 ÷ 60 mA cm−2; H3BO3 content = 0.1 ÷ 3 wt %; pH 5.8 ÷ 8.2; t = 10 ÷ 30 °C) was studied. The registered breakdown voltages obey the law of Burger and Wu, and exceeded 200 V. Clear periodical oscillations of the forming voltage were registered at high current densities. The obtained films were submitted to X-ray diffractometry (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and attenuated total reflectance Fourier transformed infrared spectroscopy (ATR-FTIR). The data obtained by these observations have revealed that these layers are composed of amorphous 2ZnO.3BO3.7H2O. Furthermore, on the basis of the scanning electron microscopy (SEM) observations a conceptual model was developed for qualitative explanation of the film growth mechanism. The appearance of high amplitude oscillations was explained by complete disjoining of the layer due to accumulation of mechanical stress. These conclusions were confirmed by obtained atomic force microscopy (AFM) images and (ICP-OES) measurements of the electrolytes after the respective polarizations.

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

Influence of Electron Beam Treatment of Co–Cr Alloy on the Growing Mechanism, Surface Topography, and Mechanical Properties of Deposited TiN/TiO2 Coatings

This study examines the effect of electron beam treatment (EBT) of Co–Cr substrate on the film growth mechanism, mechanical properties, and surface topography of TiN/TiO2 coatings deposited by reactive magnetron sputtering. The obtained results and processes that occurred during the deposition are discussed in the context of crystallographic principles, and special attention is paid to the crystallographic orientation and growth mechanism studied by X-ray diffraction (XRD). The mechanical properties were investigated by means of nanoindentation and wear tests. The surface topography was evaluated using atomic force microscopy (AFM). The results obtained in the present study showed that polycrystalline TiN and anatase TiO2 phases were present in all cases. Electron beam treatment of Co–Cr substrate tended to form a reorientation of the microvolumes from (111) to (200) of TiN, leading to a change in the growth mechanism from three-dimensional (Volmer–Weber) to layer-by-layer (Frank–van der Merwe). It was found that the electron beam treatment process did not significantly affect the thickness of the coatings and the deposition rate. The treatment process led to an increase in surface roughness. The higher surface roughness after the EBT process should be appropriate to support cell growth and adhesion on the surface of the deposited bilayer coating. It was demonstrated that EBT of the substrate caused a decrease in hardness of the deposited coatings from 10 to 5 GPa. The observed decrease in hardness was attributed to the change in the preferred crystallographic orientation and film growth mechanism. The hardness of the bilayer coating after the application of EBT of the Co–Cr substrate was much closer to that of human bones, which means that severe stress shielding effect could not be expected. The evaluated coefficient of friction (COF) exhibited significantly lower values in the case of EBT of the substrate compared to the untreated Co–Cr material.

Study on the Effect of Chemically Different Substrates on Nucleation and Growth Mechanism of Perfluoropentacene Thin Films

We studied the effect of chemical properties of substrates on the structural properties of perfluoropentacene (PFP) thin films grown by the supersonic molecular beam deposition technique. To this e...

Formation mechanism of 2D WS2 with different morphology by chemical vapor deposition

Exploring materials formation mechanism and shape evolution during the growth of nanomaterials is vital for controllable synthesis and improving the crystal quality. Here, two dimensional WS2 films were synthesized on Si/SiO2 substrates via atmospheric pressure chemical vapor deposition. Different shapes of WS2 films scattered on the surface of substrate can be obtained simultaneously under the same experimental condition. We find that the edge free energy of different edges competes with each other, which promotes the growth of two dimensional WS2. Besides, the local ratio between W and S atoms of precursors on the surface of substrates can also influence the growth process and the final morphology of WS2 films. This work is helpful in further understanding the growth mechanism of 2D films and then further modulating the quality of 2D materials.

The growth mechanism and characterization of few-layer diphenyl dinaphthothienothiophene films prepared by vacuum deposition

The growth mechanism of 2,9-diphenyl-dinaphtho [2,3-b:2′,3′-f]thieno [3,2-b]thiophene (DPh-DNTT) thin-films prepared by vacuum deposition was investigated based on the morphological crystallinity of the obtained films. In addition to atomic force microscopy, which is commonly used for imaging surface morphology, optical microscopy was also positively used for the same purpose. The technique allows the quick and easy evaluation of thin films. The optical microscopy images show that DPh-DNTT films grew according to a layer-by-layer growth mode. Each layer grew as flat two-dimensional (2D) islands with a thickness of about 2.3 nm, where DPh-DNTT molecules stand almost vertically on the substrate. The height difference between layers provided a color contrast in these images, which visualizes the initial 2D island on the Si substrate with thermally grown SiO2 and fractal-shape 2D islands on top surface. By using the method, a monolayer of isolated and round 2D islands, with a diameter of approximately 4 μm, formed at a high substrate temperature on a SiO2 surface that had been previously treated with O2 plasma or UV-O3. The presence of a DPh-DNTT layer on the substrate was also confirmed by micro-Raman measurement.

Thin-film growth behavior of non-planar vanadium oxide phthalocyanine**Project supported by the National Natural Science Foundation of China (Grant No. 51673214) and the National Key Research and Development Program of China (Grant No. 2017YFA0206600).

The thin film properties of organic semiconductors are very important to the device performance. Herein, non-planar vanadyl phthalocyanine (VOPc) thin films grown on rigid substrates of indium tin oxide, silicon dioxide, and flexible substrate of kapton by organic molecular beam deposition under vacuum conditions are systematically studied via atomic force microscopy and x-ray diffraction. The results clearly reveal that the morphology and grain size are strongly dependent on the substrate temperature during the process of film deposition. Meanwhile, the VOPc films with the structure of phase I or phase II can be modulated via in situ annealing and post-annealing temperature. Furthermore, the crystalline structure and molecular orientation of vapor-deposited VOPc can be controlled using molecular template layer 3, 4, 9, 10-perylene-tetracarboxylic dianhydride (PTCDA), the VOPc film of which exhibits the phase I structure. The deep understanding of growth mechanism of non-planar VOPc film provides valuable information for controlling structure-property relationship and accelerates the application in electronic and optoelectronic devices.

Highly sensitive NO2 sensors based on organic field effect transistors with Al2O3/PMMA bilayer dielectrics by sol-spin coating

Abstract NO2 gas sensors based on organic field effect transistors (OFETs) with alumina/poly(methyl methacrylate) (Al2O3/PMMA) bilayer dielectrics were prepared by sol-spin coating method. The sensors with 0.8 mol/L Al2O3-sol dielectric layer show a high NO2 response, low baseline drift, stable sensing performance, and fast response/recovery time at room temperature. The sensitivity is over 129%/ppm and the limit of detection is below 1 ppm (134%). The results are comparable to most organic devices. The high sensor properties were attributed to the more ordered films on the dielectric layer and better electrical properties with bilayer dielectric devices than those with single dielectric devices. Compared to OFETs with PMMA single dielectric, the mobility was improved above 23 times, threshold voltage was reduced by 32.47 V, and both on-off current radio and saturation current were improved above an order of magnitude for OFETs with Al2O3/PMMA bilayer dielectrics at 0.8 mol/L Al2O3-sol. Moreover, the mechanism of organic film growth and the effect of bilayer dielectrics on sensing properties were analyzed. It is revealed that the highly electrical and NO2 sensing properties are closely relate. A simple and effective method, the sol-spin coating method, was provided to obtain high performance NO2 gas sensors based on OFETs.

Induced Synthesis of Vertically Oriented Multilayer MoS2 via CVD Method

Fabrication of nanostructured MoS2 for photodetector applications has become increasingly attractive due to its atomically thin profile and favorable bandgap. In this paper, vertically oriented multilayer MoS2 (V-MoS2) are grown directly on a SiO2 substrate by chemical vapor deposition (CVD) with TiO2 being adopted as an induced precursor for the first time. The interim morphologies of the synthesized MoS2 are investigated and the growth mechanism of the MoS2 film is proposed.

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.

SnPc Molecules on Surfaces Studied by Scanning Tunneling Microscopy

Using single molecule as a basic unit of storage devices is an appealing direction of device miniaturization. Tin-phthalocyanine (SnPc) molecules exhibit bistable adsorption configurations, Sn-up and Sn-down. A reversible conversion between these two configurations is readily manipulated and probed by scanning tunneling microscopy (STM). When SnPc molecules are used to form functional devices, they need to adsorb on supporting surfaces. So the growth mechanisms of ultra-thin films on metal surfaces or buffer layers have been investigated. Both layer-island (Stranski–Krastanov) and three-dimensional-island (Volmer–Weber) growth modes are observed in experiments. Because of an electronic decoupling of buffer layers, electronic and vibronic states of SnPc molecules are spectroscopically identified. Molecular switches between Sn-up and Sn-down configurations are achieved by either an electrical mean or mechanical forces. When the STM tip contacts SnPc molecules with controlled structures, electrons transports through single-molecule junctions are explored in detail. In addition, Ag–SnPc–Ag junction exhibits three conductance states at different voltages. These researches pave a way for further development of high-density data storage devices.

Influence of pulse frequency on the morphology, structure and optical properties of ZnO films prepared by pulsed electrodeposition

Zinc oxide films were grown at 65 °C by pulsed electrodeposition onto ITO substrates using as electrolyte solution 0.1 M Zn(NO3)2 without supporting electrolyte. The potential was pulsed between OCP and −1300 versus Pt. ZnO films were measured by x-ray diffraction, UV–vis transmittance and scanning electron microscopy. The pulse frequency was varied from 1 to 100 Hz, with amplitude of 1300 mV and symmetric pulses. It was observed that the frequency has a major effect on film structuring with a big impact on the crystal habit and film thickness. The films were crystalline with different crystallographic orientation depending on the growth conditions with a band gap around 2.8–3.4 eV indicating a strong influence of the frequency on the electronic defects. The film growth mechanism and the film properties are discussed in terms of the effect of pulse frequency on the competing stages of nucleation-dissolution and Zn deposition-oxidation stages.

Structural and luminescence properties of laser assisted Eu3+ doped BaZrO3 thin films

Eu3+ doped BaZrO3 thin films were deposited on quartz substrates in a wide range of oxygen pressure (1–300 mTorr), using Pulsed laser deposition technique. X-ray diffraction pattern showed the different growth orientation of the films with oxygen pressure (PO2). The different growth mechanisms were drawn to explanin the thin films growth mechanism at the different oxygen pressure. Time of flight secondary ion mass spectroscopy analysis exhibited homogeneous distribution of all the elements throughout the depth of the films. The depth profile anaylsis revealed sharp interface at the low PO2 and broad intermixing region of the films with the substrate at low PO2. Transmittance spectra revealed the different optical bandgap with different PO2. Excitation spectra showed a broad absorption band centered at 260 nm due to the absorption in the defect states. The emission spectra showed intense emission at 597 nm corresponding to the 5D0→7F1 transition of Eu3+. Apart from this, a broad blue-green emission was observed centered at 440 nm due to the trap levels associated with the oxygen vacancy below the conduction band. The energy transfer mechanism between the host to Eu3+ ion was described via a defect state process. Colour coordintes of the emission spectra showed that colour emission of thin films can be tuned by varying the oxygen pressure. The short-excited state lifetime and high value of internal quantum efficiency make these films potential candidates for light emitting diode application.

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.

Effect of Processing Parameters on Monolayer MoS2 Prepared by APCVD in a Quasiclosed Crucible

Chemical vapor deposition is one of the universally acknowledged methods to synthesize two-dimensional transition-metal dichalcogenides with high crystal quality and large size. However, variations in the process parameters directly influence the number of layers and the quality of molybdenum disulfide (MoS2) films. Thus, achieving controllable growth of monolayer MoS2 films is still a challenge. In this study, the immunity of the monolayer nature of MoS2 domains to process parameters was systematically investigated by varying the vaporization/growth temperature, time of sulfur addition, ramp rate, and distance between the precursors and receiving substrate using a quasiclosed crucible in a modified atmospheric-pressure CVD system. The results indicated that incorporating a quasiclosed crucible could facilitate controllable growth of monolayer MoS2 films where the monolayer nature is immune to process parameters. Further, we attempted to elucidate the growth mechanism of monolayer MoS2 films, which will contribute toward precise control over the synthesis of MoS2 and other transition-metal dichalcogenides within a broad processing window.

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.

Impact of Cone‐Shape‐Patterned Sapphire Substrate and Temperature on the Epitaxial Growth of p‐GaN via MOCVD

In this paper, the authors report both the effects of the cone‐shape‐patterned sapphire substrate (CSPSS) and the growth temperature on surface morphology and crystalline quality of the p‐GaN layers, grown via metal‐organic chemical vapor deposition (MOCVD). Low‐temperature GaN buffer and high‐temperature undoped GaN (u‐GaN) coalescence layers are grown between p‐GaN epitaxial film and substrate for all the samples. The time evolution of surface morphology of those films is monitored by scanning electron microscope (SEM) in order to investigate the growth mechanism of films on CSPSS. The compressive stresses in the p‐GaN films is also discussed. From atomic force microscopy (AFM) and X‐ray diffraction (XRD) results, it is observed that, using CSPSS at a lower temperature (1030 °C) significantly reduces the surface roughness and enhances the crystallinity of p‐GaN film compared to growth at 1060 °C on conventional sapphire substrate. Furthermore, the low resistivity level of 0.05 Ω cm and high hole carrier concentration of 1.57 × 1019 cm−3 in the p‐GaN have been achieved by using CSPSS at lower temperature.