Plasma-enhanced Chemical Vapor Deposition Technique Research Articles

Optimized study of the annealing effect on the electrical and structural properties of HDLC thin-films

The plasma-enhanced chemical vapor deposition (PECVD) technique has been utilized for the facile surface deposition of hydrogenated diamond-like carbon (HDLC) thin-films onto Si(100) substrates. The as-deposited film surface is homogenous, free of pinholes, and adheres to the substrate. Annealing of the synthesized HDLC surface in a vacuum was performed in the temperature range of 200 to 1000 °C. A host of instrumental techniques, viz. FTIR spectroscopy, AFM, STM, and EC-AFM, were successfully employed to detect the morphological transformation in the HDLC films upon annealing. EC-AFM studies show irreversible biased behavior after undergoing a surface redox couple reaction and morphological change. Raman spectroscopy was carried out along with STM and EC-AFM to determine the functional nature and conductivity of the annealed surface.

Sub-micrometer plasma-enhanced chemical vapor deposition using an atmospheric pressure plasma jet localized by a nanopipette scanning probe microscope

We developed a localized plasma-enhanced chemical vapor deposition (PE-CVD) technique to deposit silicon oxide with a sub-micrometer width on a substrate using an atmospheric pressure plasma jet (APPJ) irradiated from a nanopipette nozzle. To realize fine material deposition, hexamethyldisiloxane (HMDSO) vapor was blown into the localized helium APPJ irradiated from the sub-micrometer aperture of the nanpopipette with the jet length limited to the aperture size of the nanopipette. The irradiation distance was controlled using a shear-force positioning technique using scanning probe microscopy (SPM). The proposed system successfully deposited silicon oxide dots with sub-micrometer width on a substrate. After the deposition, the topography of the deposited surface was observed by scanning the nanopipette, which can be used as an SPM probe. The localized PE-CVD properties were systematically investigated by varying the deposition parameters. The amount of deposited material could be controlled by the flow rate of the carrier gas of the HMDSO vapor, APPJ irradiation time, and nanopipette–substrate surface irradiation distance.

The evolution of properties with deposition time of vertical graphene nanosheets produced by microwave plasma-enhanced chemical vapor deposition

In our studies, the vertical graphene nanosheets (VGN) of various heights and densities were grown on fused silica substrates by microwave plasma-enhanced chemical vapor deposition technique at different growth durations from 20 to 140 min to follow the evolution of VGN properties on the deposition time. The feedstock of the working gases and applied microwave power was kept constant focusing solely on the influence of the deposition duration. The properties and quality of VGN samples were explored by methods of scanning electron microscopy, atomic force microscopy, Raman scattering spectroscopy, and transient absorption spectroscopy (TAS). A clear correlation between the TAS results and the defectiveness and disorder of VGN layers defined by Raman scattering spectroscopy illustrates that the TAS technique can be efficiently used to describe the quality of graphene nanostructures. Increasing the deposition duration optimal growth conditions were determined ensuring the highest quality of the graphene while further increase resulted in deposits of different carbon allotropes.

DLC-Based Coatings Obtained by Low-Frequency Plasma-Enhanced Chemical Vapor Deposition (LFPECVD) in Cyclohexane, Principle and Examples

The LFPECVD (Low-Frequency Plasma-Enhanced Chemical Vapor Deposition) technique is now used on an industrial scale for the deposition of carbon-based coatings for several applications. This short review recalled the main principles of LFPECVD and provided examples of DLC-based films. The main differences between low-frequency (LF) and radio-frequency (RF) discharges were also recalled here and examples of deposition and characterization of carbon-based films were proposed. The influence of the bias voltage or the temperature of the active electrode on the deposition rate and the structure of a-C: H films obtained in cyclohexane/hydrogen mixtures was first discussed. Next, the properties of carbon-based films doped with silicon were described and, finally, it was shown that multilayer architectures make it possible to reduce the stresses without altering their tribological properties.

Vertical Graphene Growth on AlCu4Mg Alloy by PECVD Technique

Vertical graphene, which belongs to nanomaterials, is a very promising tool for improving the useful properties of long-used and proven materials. Since the growth of vertical graphene is different on each base material and has specific deposition setting parameters, it is necessary to examine each base material separately. For this reason, a full factor design of experiment was performed with 26 = 64 rounds, which contained additional 5 central points, i.e., a total of 69 rounds of individual experiments, which was to examine the effect of input factors Temperature, Pressure, Flow, CH4, Plasma Power, and Annealing in H2 on the growth of vertical graphene on aluminum alloy AlCu4Mg. The deposition was performed using plasma-enhanced chemical vapor deposition (PECVD) technology. Mainly, the occurrence of graphene was analyzed, which was confirmed by Raman spectroscopy, as well as its thickness. The characterization was performed using electron and transmission microscopy, including an atomic force microscope. It was found that the growth of graphene occurred in 7 cases and its thickness is affected only by the interaction flow (sccm) × pretreatment H2 (sccm).

Surface morphology of nanostructured zinc oxide materials obtained by plasma-enhanced chemical vapor deposition

Zinc oxide nanostructures have been obtained by plasma-enhanced chemical vapor deposition technique. High-purity elemental zinc was used as the precursor. RF (40MHz) inductively coupled plasma discharge was used for the initiation of the plasma-chemical reactions in the gas phase. Hydrogen-oxygen (H2-O2) composition of various ratios was used as the source plasma gas mixture. The optical emission spectroscopy was used as the powerful tool to determine the intermediate excited particles and assume the possible mechanism of the plasma-chemical reactions. The paper also investigates the influence of the substrate’s materials, its temperature, and the power of the heat input into the discharge. The properties of the sprayed materials were characterized by the method of atomic force microscopy.

Optical Constant and Conformality Analysis of SiO2 Thin Films Deposited on Linear Array Microstructure Substrate by PECVD

SiO2 thin films are deposited by radio frequency (RF) plasma-enhanced chemical vapor deposition (PECVD) technique using SiH4 and N2O as precursor gases. The stoichiometry of SiO2 thin films is determined by the X-ray photoelectron spectroscopy (XPS), and the optical constant n and k are obtained by using variable angle spectroscopic ellipsometer (VASE) in the spectral range 380–1600 nm. The refractive index and extinction coefficient of the deposited SiO2 thin films at 500 nm are 1.464 and 0.0069, respectively. The deposition rate of SiO2 thin films is controlled by changing the reaction pressure. The effects of deposition rate, film thickness, and microstructure size on the conformality of SiO2 thin films are studied. The conformality of SiO2 thin films increases from 0.68 to 0.91, with the increase of deposition rate of the SiO2 thin film from 20.84 to 41.92 nm/min. The conformality of SiO2 thin films decreases with the increase of film thickness, and the higher the step height, the smaller the conformality of SiO2 thin films.

Effect of trampoline sputtering on surface morphology and coatings properties

The collective trampoline ion-plasma effect was used to modify surface properties of metals, ceramics, silicon and carbon in a desired manner. The rough surfaces created by low-energy dense ion flows were demonstrated to include double-level hierarchical structures. Namely, the submicron and nanoscale peaks and valleys were found. The coating films were deposited by the nanoclusters emitted in the trampoline mode, as well as by plasma-enhanced chemical vapor deposition (PECVD) and physical vapor deposition (PVD) methods. The substrates were prepared by prior ion processing in the trampoline mode. Preliminary nanoscale texturing of surfaces substantially modified the interaction of ion-plasma flows with surfaces during the subsequent film formation by PVD and PECVD techniques. The so created rough surface showed the strong film adhesion and a 25%–50% faster film formation during ion-plasma deposition as compared to the case of a non-textured surface. The transfer of target material in the form of nanoclusters allowed obtaining dense defect-free micron-scale films. The submicron structure leads to the infrared and visible light trapping. The results were analyzed on the basis of the previously suggested qualitative model of the trampoline sputtering.

Universal interface and defect engineering dual-strategy for graphene-oxide heterostructures toward promoted Li–S chemistry

Li–S battery is broadly regarded as one of the most promising energy storage systems due to its prominent merits in energy density and theoretical capacity. Nevertheless, existing challenges such as formidable shuttle effect and sluggish redox kinetics hinder its practical application. Herein, we propose a universal interface and defect engineering dual-strategy to design graphene-oxide (G-oxide) hybrids as heterostructured electrocatalysts targeting promoted Li–S chemistry. The employment of direct plasma-enhanced chemical vapor deposition technique allows the in situ formation of graphene over a suite of oxide powders. Benefiting from the creation of heterointerface and carbon/oxygen defects, G-oxide realizes balanced management of polysulfide adsorption, lithium-ion migration and electron transportation, accordingly rendering bi-directional electrocatalysis behaviors for the sulfur conversion. Thus-assembled S/G-oxide cathode affords stable cycling performances even under a sulfur loading of 8.1 mg cm−2 and an electrolyte usage of 4.0 μL mg–1S.

Novel photoluminescent In2O3/a-SiC core/shell nanostructure synthesized by HW-assisted PECVD method

Semiconductor core/shell nanostructures have been recently attracted a great interest due to interesting properties and wide potential applications. In this work, In2O3/a-SiC core/shell nanostructure was successfully synthesized for the first time using hot wire-assisted plasma-enhanced chemical vapor deposition technique. The crystalline structure, morphology, chemical composition, and optical properties of the deposited film were investigated by variety of characterization techniques including X-ray diffraction, field emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, high-resolution transmission electron microscopy, Fourier transform infrared spectroscopy, UV–Vis–NIR spectrophotometry, photoluminescence spectroscopy (PL) and Raman scattering spectroscopy. The results verified the formation of core/shell nanostructures, crystalline In2O3 as a core and amorphous SiC as a shell, successfully. The average diameter and thickness of synthesized core and shell were 101 and 38 nm, respectively. A strong and broad room-temperature PL emission in the visible and near-infrared region was observed for the synthesized structure as a result of synergic effects. This broad band was consisted of Gaussian peaks at the wavelengths of 570, 656, 728, 763, and 842 nm. The origin of different PL peaks was discussed in the paper. The results show that the novel In2O3/a-SiC core/shell nanostructure is a good candidate for optical applications.

Compositional, Structural, Morphological, and Optical Properties of ZnO Thin Films Prepared by PECVD Technique

ZnO thin films were synthesized on silicon and glass substrates using the plasma-enhanced chemical vapor deposition (PECVD) technique. Three samples were prepared at substrates temperatures of 200, 300, and 400 °C. The surface chemical composition was analyzed by the use of X-Ray Photoelectron spectroscopy (XPS). Structural and morphological properties were studied by using X-ray diffraction (XRD) and scanning electron microscopy (SEM). Optical properties were carried out by UV-visible spectroscopy. XPS spectra showed typical peaks of Zn(2p3/2), Zn(2p1/2), and O(1s) of ZnO with a slight shift attributed to the substrate temperature. XRD analysis revealed hexagonal wurtzite phases with a preferred (002) growth orientation that improved with temperature. Calculation of grain size and dislocation density revealed the crystallization improvement of ZnO when the substrate temperature varied from 200 to 400 °C. SEM images of ZnO films showed textured surfaces composed of grains of spherical shape uniformly distributed. The transmittance yields are reaching 80%, and the values of the band-gap energy indicate that the ZnO films prepared by PECVD present transparent and semiconducting properties.

Silica Layer Used in Sensor Fabrication from a Low-Temperature Silane-Free Procedure

Silica (SiO2, silicon dioxide—a dielectric layer commonly used in electronic devices) is widely used in many types of sensors, such as gas, molecular, and biogenic polyamines. To form silica films, core shell or an encapsulated layer, silane has been used as a precursor in recent decades. However, there are many hazards caused by using silane, such as its being extremely flammable, the explosive air, and skin and eye pain. To avoid these hazards, it is necessary to spend many resources on industrial safety design. Thus, the silica synthesized without silane gas which can be determined as a silane-free procedure presents a clean and safe solution to manufactures. In this report, we used the radio frequency (rf = 13.56 MHz) plasma-enhanced chemical vapor deposition technique (PECVD) to form a silica layer at room temperature. The silica layer is formed in hydrogen-based plasma at room temperature and silane gas is not used in this process. The substrate temperature dominates the silica formation, but the distance between the substrate and electrode (DSTE) and the methane additive can enhance the formation of a silica layer on the Si wafer. This silane-free procedure, at room temperature, is not only safer and friendlier to the environment but is also useful in the fabrication of many types of sensors.

TiO2 Coatings Via Atmospheric-Pressure Plasma-Enhanced Chemical Vapor Deposition for Enhancing the UV-Resistant Properties of Transparent Plastics.

Herein, TiO2 coatings were deposited on photodegradable polymers for protection from UV irradiation using the atmospheric-pressure plasma-enhanced chemical vapor deposition (AP-PECVD) technique. Polymethylmethacrylate (PMMA) and polycarbonate (PC) substrates were coated with titanium tetraisopropoxide as the precursor in an open-air atmospheric-pressure nonequilibrium argon plasma jet. The AP-PECVD-derived TiO2 coatings exhibited good adhesion to PMMA and PC. The TiO2 coatings could shield more than 99% of UV light in the wavelength range of 200–300 nm, without affecting the transmittance of visible light. UV irradiation tests on polymer films demonstrated that the degradation rates of PMMA and PC were significantly reduced by one-tenth after they were coated with TiO2 films.

Effect of Bias Voltage on Characteristics of Multilayer Si-DLC Film Coated on AA6061 Aluminum Alloy

The multilayer Si-DLC films have been deposited on AA6061 aluminum alloy using a mesh hollow cathode plasma-enhanced chemical vapor deposition technique from acetylene and silane precursor gas at temperature 373 K. Low magnification electron microscopes, Raman spectroscopy, and Fourier transform infrared spectroscopy were employed for characterizing the coating film structure. The MFT-4000 scratch tester, G200 nano-indentation tester, and MS-T3001 tribology tester were utilized to evaluate the adhesion strength, mechanical properties, and friction coefficient. Potentiodynamic polarization and potentiostatic techniques were used to study the multilayer Si-DLC films electrochemical behavior in harsh solution 3.5 wt.% NaCl. The findings revealed that the increase in bias voltage to − 300 V led to the adhesion strength, hardness, elastic modulus, and friction coefficient around 18N, 9.89 GPa, 85.57 GPa, and 0.17, respectively. The polarization results showed a decrease in corrosion current density, increased polarization resistance, and decreased passive current almost 1.28×10−10 A/cm−2, 5.26×109 Ω cm2, and 24.3 nA cm−2, respectively. The findings are ascribed to reduce the internal stress and increase the overall content of sp3 bonds in the film. Moreover, the Si-doped DLC film forms a passive layer from SiOx at the film/solution interface to impede the charge transfer.

Environmentally friendly approach for the fabrication of polyamide thin film nanocomposite membrane with enhanced antifouling and antibacterial properties

In this work, we employed an environmentally friendly approach based on plasma enhanced chemical vapour deposition (PECVD) to modify titania nanotubes (TNTs), aiming to obtain better dispersion of nanofillers in polyamide (PA) layer of thin film nanocomposite (TFN) reverse osmosis membrane. Owing to the hydrophilic nature of TNTs, dispersing it homogenously in organic solvent during interfacial polymerization process is difficult to achieve. Therefore, the TNTs are mildly modified by PECVD technique in order to ameliorate its stability in organic solvent. Our results showed that depositing thin layer of methyl methacrylate (MMA) on the TNTs surface could enhance its dispersion quality in organic solvent and further improve the properties of PA layer by enhancing membrane water flux by 16% without compromising NaCl rejection. More importantly, the developed TFN membrane showed excellent fouling resistance by recording flux recovery rate of 85.77% compared to 57.94% shown by the control membrane. Its antibacterial property was also obviously better than that of control membrane. Overall, the developed TFN membrane demonstrated good performance stability with respect to NaCl rejection and water permeability and the trace amount of nanofillers detected in the water sample (in the level ofμg/L) did not negatively influence the membrane filtration performance.

Hybrid Metamodel—NSGA-III—EDAS based Optimal Design of Thin Film Coatings

In this work, diamond-like carbon (DLC) thin film coatings are deposited on silicon substrates by using plasma-enhanced chemical vapour deposition (PECVD) technique. By varying the hydrogen (H₂) flow rate, CH₄−Argon (Ar) flow rate and deposition temperature (T_d) as per a Box-Behnken experimental design (BBD), 15 DLC deposition experiments are carried out. The Young’s modulus (E) and the coefficient of friction (COF) for the DLCs are measured. By using a second-order polynomial regression approach, two metamodels are built for E and COF, that establish them as functions of H₂ flow rate, CH₄-Ar flow rate and T_d. A non-dominated sorting genetic algorithm (NSGA-III) is used to obtain a set of Pareto solutions for the multi-objective optimization of E maximization and COF minimization. According to various practical scenarios, evaluation based on distance from average solution (EDAS) approach is used to identify the most feasible solutions out of the Pareto solution set. Confirmation experiments are conducted which shows the efficacy of the polynomial regression—NSGA-III—EDAS hybrid approach. The surface morphology of the DLCs deposited as per the optimal predictions is also studied by using atomic force microscopy.

Rapid Surface Modification of Ultrafiltration Membranes for Enhanced Antifouling Properties.

In this work, several ultrafiltration (UF) membranes with enhanced antifouling properties were fabricated using a rapid and green surface modification method that was based on the plasma-enhanced chemical vapor deposition (PECVD). Two types of hydrophilic monomers—acrylic acid (AA) and 2-hydroxyethyl methacrylate (HEMA) were, respectively, deposited on the surface of a commercial UF membrane and the effects of plasma deposition time (i.e., 15 s, 30 s, 60 s, and 90 s) on the surface properties of the membrane were investigated. The modified membranes were then subjected to filtration using 2000 mg/L pepsin and bovine serum albumin (BSA) solutions as feed. Microscopic and spectroscopic analyses confirmed the successful deposition of AA and HEMA on the membrane surface and the decrease in water contact angle with increasing plasma deposition time strongly indicated the increase in surface hydrophilicity due to the considerable enrichment of the hydrophilic segment of AA and HEMA on the membrane surface. However, a prolonged plasma deposition time (>15 s) should be avoided as it led to the formation of a thicker coating layer that significantly reduced the membrane pure water flux with no significant change in the solute rejection rate. Upon 15-s plasma deposition, the AA-modified membrane recorded the pepsin and BSA rejections of 83.9% and 97.5%, respectively, while the HEMA-modified membrane rejected at least 98.5% for both pepsin and BSA. Compared to the control membrane, the AA-modified and HEMA-modified membranes also showed a lower degree of flux decline and better flux recovery rate (>90%), suggesting that the membrane antifouling properties were improved and most of the fouling was reversible and could be removed via simple water cleaning process. We demonstrated in this work that the PECVD technique is a promising surface modification method that could be employed to rapidly improve membrane surface hydrophilicity (15 s) for the enhanced protein purification process without using any organic solvent during the plasma modification process.

Development of biobased multilayer films with improved compatibility between polylactic acid-chitosan as a function of transition coating of SiOx

A SiOx coating prepared via plasma-enhanced chemical vapor deposition (PECVD) technique was used as a transition layer between polylactic acid (PLA) and chitosan (CS) to form a three-layer composite film of PLA/SiOx/CS. The effect of oxygen plasma irradiation time (0 s, 30s and 60s) on SiOx surface and PLA-CS interface was examined based on the contact angle, pull-off test and scanning electron microscope (SEM). The mechanical, barrier and antibacterial properties of PLA/SiOx/CS films were also investigated. The results showed that oxygen plasma irradiation improved the hydrophilicity of the SiOx surface and the adhesive strength between SiOx-CS of PLA/SiOx/CS films in a time-dependent manner. SEM examination revealed a gap between PLA/CS layers, but the interfacial separation among layers in PLA/SiOx/CS films disappeared as the transition layer of SiOx and oxygen plasma irradiation (60s) intensified. Notably, the oxygen barrier property and antibacterial activity of PLA/SiOx/CS films were dramatically enhanced. Additionally, moisture resistance was slightly decreased following the incorporation of the CS coating compared with the PLA film. The tensile strength of the composite film also increased with the number of layers, while elongation at break decreased. The prepared PLA/SiOx/CS films with multifunction are promising applied in food packaging as biobased materials.

CVD-diamond nanoparticle synthesis for DLC film application

Diamond-like carbon (DLC) films have been extensively applied as a solid lubricant and as a protective coating due to their attractive chemical, mechanical, and tribological properties. Furthermore, these properties of DLC coatings can be improved with the incorporation of nanoparticles of different materials, especially diamond nanoparticles (DNPs). Herein, the incorporation of chemical vapor deposition (CVD) DNPs was done from a deionized aqueous colloidal solution by using a controlled pulsed valve, which is an innovative aspect of this work. The CVD DNPs were pulverized into the plasma region and incorporated in the DLC films bulk with controllable size particle distribution and density. In addition, an enhanced process to obtain DNPs with suitable size distribution was established by using a high energy ball milling technique, centrifugation, and a special chemical cleaning process. The DLC films were deposited on a metallic substrate via a modified, pulsed DC plasma-enhanced chemical vapor deposition (PECVD) technique, with an additional cathode. X-ray diffractometry (XRD) and scanning electronic microscopy (SEM) techniques showed that an aqueous colloidal solution of high-purity DNPs with a mean diameter of 32 nm was obtained. Dynamic light scattering (DLS) results showed that it is possible to control particle size distribution by varying the milling and centrifugation time lengths. Therefore, a valuable result was that DLC films could be deposited with DNPs by using clean water without affecting deposition rate, the adhesion between the DLC films and substrates, the structural quality of the film, and keeping lower coefficient of friction.

Achieving high efficiency silicon heterojunction solar cells by applying high hydrogen content amorphous silicon as epitaxial-free buffer layers

High hydrogen content (CH) intrinsic amorphous silicon (a-Si:H) buffer layers were deposited on both sides of crystalline silicon wafers using plasma-enhanced chemical vapor deposition technique, which significantly improved surface passivation as well as conversion efficiency of the silicon heterojunction solar cells. Properties of the buffer layer and impact on the device performance were investigated. High resolution transmission electron microscope characterization shows that no obvious epitaxial growth occurred at the interface as long as a-Si:H buffer layer was introduced between c-Si and bulk intrinsic layer. Further study indicates that minority carrier lifetime of the device is related to hydrogen content of the buffer layer, reaching highest value up to 2050 ms at CH of 33%. These findings evidently confirmed that suppression of epitaxial growth and thus improved passivation were realized by using high-hydrogen-content a-Si:H buffer layer, based on which a high efficiency solar cell was prepared with large area.