PECVD Technique Research Articles

Nitrogen modified graphene nanowalls for retrieval of trace level cerium from aqueous medium

Removal of cerium from environmental and aqueous streams is essential in waste water rejuvenation processes. Nitrogen modified graphene nano walls (N-GNWs) have shown ultra-high sorption efficiency of trivalent cerium from aqueous medium (Kd > 2 × 107) and a large sorption capacity of ∼ 2500 mg/g is achieved. N-GNWs were deposited on carbon paper substrate using PECVD technique. The three-dimensional nature of N-GNWs are revealed from high resolution FESEM images. Raman spectroscopic studies have shown that GNWs are defective and possess a few layer graphene like structure. Secondary Ion Mass Spectroscopic studies of the Ce sorbed N-GNWs and optical emission spectroscopy of the residual solution confirm the sorptive retrieval of cerium. Visual Minteq based ionization model is introduced to explain high (>90 %) sorption of Ce at pH≥7 and the mechanistic aspects of sorption for standard Cerium solution is discussed. The sorption involves attachment of cerium hydroxyl ions to the active cites on the sorbent surface.

A substrate constituent Na-catalyzed growth of carbon nanotubes on glass substrate by atmospheric pressure PECVD

A growth mechanism of carbon nanotubes (CNTs) without any externally added catalyst is reported in this study. Instead of any externally added catalyst, the constituents of the used soda lime glass substrates seem to play the pivotal role in the growth of CNTs. XPS analysis of the synthesized CNTs reveal that among the various constituents of soda lime glass, sodium (Na) emerges as the primary catalyst for initiating CNT growth. The adopted PECVD technique involving an especially designed spiral-shaped fused hollow cathode source for generating the required atmospheric pressure plasma makes such synthesis easily feasible. The important key factors influencing CNT growth include substrate temperature and plasma pre-treatment of the substrate. Plasma pre-treatment of the substrate at an elevated temperature leads to the formation of catalyst nanoparticles on the surface of the substrate. This report features a detailed CNT growth mechanism proposed on the basis of optical emission spectroscopy and XPS analyses. To be precise, this study demonstrates a novel Na-catalysed synthetic approach for achieving uniform CNT growth on glass substrates without using any externally added catalyst, facilitating the preparation of clean CNTs.

Reflection optimization of a multicrystalline solar cell embedded in a photovoltaic module

In this paper we study the surface reflection of a photovoltaic module. The antireflection layer based on silicon nitride SiNx, is deposited by PECVD technique and optimized to a solar cell surface. However, encapsulating the cell in a module (Glass/EVA/SiNx/Silicon) modifies the total reflection of the whole structure. Therefore an optimization of reflection is required to get a good electrical output of the module. In this purpose, we have proceeded by characterizing step by step the optical constants of each layer constituting the module structure: SiNx antireflective layer, EVA layer and glass. We elaborated a specific structure to get those parameters. We measured the total reflection in the UV-VIS-NIR spectra. Reflection curves of EVA and Glass show the same flat shape between 350 and 1100 nm. The mean reflection value of 8.2 % and 7.8 % respectively indicate that the two mediums EVA and glass are quasi similar. Meanwhile the whole structure presents a spectral reflection with a shape similar to that of silicon nitride layer, with a minimum around 600 nm (5.1 % and 2.3 % respectively). After simulating the optical parameters of the layers, we optimized again the reflection of the structure to be minimal. This indicates us that the optimal values of the SiNx layer to be used in the structure are: n = 2.4 and d = 69.18 nm. These values give a minimum reflection of the structure around 0.16 % at 614 nm.

Retraction Note to: Increase of the Surface Mobility of Carbon Molecular Crystals (CMCs) Using the PECVD Technique

Retraction Note to: Increase of the Surface Mobility of Carbon Molecular Crystals (CMCs) Using the PECVD Technique

Study on properties of diamond-like carbon films deposited by RF ICP PECVD method for micro- and optoelectronic applications

In this paper, a comparison of Diamond-like Carbon (DLC) films with different sp3 fraction content prepared by Radio Frequency Inductively Coupled Plasma Enhanced Chemical Vapour Deposition (RF ICP PECVD) was presented. Structural, surface, optical, and mechanical properties of deposited DLC films were analyzed with the use of awide range of measurement techniques. The investigated films were deposited on silicon (Si), amorphous silica (SiO2), and metallic (Ti6Al4V) substrates at room temperature. The deposited DLC films have sp3 fraction content ranging from 35 % to 70 %, uniform, compact and dense microstructure. The investigation indicates that the properties of DLC films required for micro- and optoelectronic applications improve with the sp3 fraction content. The refractive index (n) increased from 1.976 to2.086, packaging density (PD) from 0.964 to 0.744, electrical resistivity (ρ) from 2.1 ∙ 1010 to 4.4 ∙ 1011 Ωcm, hardness (H) from 16.4 19.1 to GPa and elastic modulus (E) from 109 to 129 GPa. However, the 50 % sp3 DLC thin film exhibited the highest resistance to cracking (H3/E2 = 0.44). The decrease of Urbach energy (EU) from 0.75 to 0.46 eV was observed for the DLC film with the highest sp3 fraction content, while all investigated DLC samples had similar optical bandgap energy (Egopt ≈ 1.3 eV). The research has shown that it is possible to obtain DLC coatings using the RF ICP PECVD technique that has better properties than films deposited by the classic PECVD technique.

Exploring the functionalization of Ti-6Al-4V alloy with the novel antimicrobial peptide JIChis-2 via plasma polymerization

This study aimed to characterize the immobilization of the novel JIChis-2 peptide on the Ti-6Al-4V alloy, widely used in the biomedical sector. The antimicrobial activity of JIChis-2 was evaluated in the Gram-negative bacterium E. coli. Its immobilization occurred by inducing the formation of covalent bonds between the N-terminus of the peptides and the surface previously submitted to acrylic acid polymerization via the PECVD technique. Coated and uncoated surfaces were characterized by FTIR, AFM, SEM and EDX. Studies of global and localized corrosion were carried out, seeking to explore the effects triggered by surface treatment in an aggressive environment. Additionally, the ability of the functionalized material to prevent E. coli biofilm formation evidenced that the strategy to immobilize JIChis-2 in the Ti-6Al-4V alloy via PECVD of acrylic acid resulted in the development of a functional material with antibiofilm properties.

Design and preparation of high-transmittance broadband antireflection coatings with tailored refractive indices deposited by PECVD

The design and preparation of conventional optical films are mainly limited by the refractive indices of available materials. Here, a simple-operation antireflection coatings (ARCs) design method was developed based on the tailored refractive index characteristics of thin-film materials. High-transmittance, broadband (400–800 nm), three-layer single- and double-sided ARCs with tailored refractive indices and transmittances of 99.2% and 98.5%, respectively, were designed. The sensitivity of the ARCs system was simulated, which predicts the variable range of the transmittance affected by the random manufacturing errors in the refractive index (±0.5%) and film thickness (±2.5%) of each layer. The ARCs consisted of nonstoichiometric silicon oxynitride and silicon nitride films formed on glass substrates by PECVD techniques. The crystallite state, relative atomic concentration, and Si-centered tetrahedral phase Si–Si4-(ν+η)OνNη of each layer were determined. The morphology images of top and cross-section views and elemental mapping of ARCs were displayed. The designed and measured transmittances were compared; the average transmittance deviations of the single- and double-sided amorphous ARCs over the visible were 0.1% and 0.4%, respectively, which show good agreement. Furthermore, the reproducibility, repeatability, and stability of PECVD were evaluated. These results are detail discussed and are expected to serve as a reference for the preparation of optical films formed via PECVD.

Exploration of Novel Hafnium Oxide (HfO2) Based Plasma-Assisted Gate All Around Carbon Nanotube FET (GAA-CNTFET) for High Sensing Applications

The present research aims to implement a Hafnium Oxide (HfO2) based Plasma-Assisted Gate All Around Carbon Nanotube Field Effect Transistor (GAA-CNTFET) and use it for a better understanding of plasma parameters and their effect on the device. With a more streamlined focus on plasma synthesized (PECVD technique) CNT for channel material, the intention is to understand how the incorporation of high-k dielectrics leads to enhanced device performance. HfO2 is used as a high-k dielectric to overcome the limitations of conventional Silicon Dioxide (SiO2) gate dielectric. A comparative analysis has been performed, based on which it can be concluded that using HfO2 leads to improvement in all observed performance metrics—higher drain current, transconductance, output conductance, early voltage, and gate capacitance. Furthermore, by implementing a cavity in the oxide layer and utilizing the concept of dielectric modulation, it can be observed that tailoring the dielectric permittivity of the cavity affects and alters the device’s performance characteristics. Better performance and high sensitivity are tilted towards a higher dielectric constant value. This analysis’s results help quantify the practical usage of the device for sensing applications in biology, environment and other prominent industries.

Hydrophobization of paper intended for packaging

Superhydrophobic surfaces are highly desired for several applications due to their exceptional properties such as self-cleaning, anti-icing, anti-friction and others. Such surfaces can be prepared via numerous methods including plasma technology [1-7]. Among plasma technology methods used to prepare these surfaces, the plasma enhanced chemical vapor deposition method, which provides the advantages of low cost, simple processing, and easy to form micro-nano structure. In this work, a treatment of surface paper for improving hydrophobicity using a PECVD technique was realized, paper substrates was treated by CH4 plasma , the substrates were held on a grounded substrate, with time variation of 5, 10, 15 and 20 min, while pressure and power have been kept constant at 8.10-2 and 100 W respectively. After deposition we proceeded to carry out structural and morphological characterization of the treated surfaces, by (SEM), AFM, FTIR and then through contact angle measurements. It is found that all layers are hydrophobic and super-hydrophobic. Except the layers treated for 10 minutes which are hydrophobic with a contact angle equal to 137.7° , the layers treated for 05, 15 and 20 minutes show superhydrophobic surfaces with a contact angles equal to 153.8°, , 149.2° and 156◦ respectively.

The Optical and Thermo-Optical Properties of Non-Stoichiometric Silicon Nitride Layers Obtained by the PECVD Method with Varying Levels of Nitrogen Content.

In this paper, we investigated the optical and thermo-optical properties of a-SiNx:H layers obtained using the PECVD technique. SiNx:H layers with different refractive indices were obtained from silane and ammonia as precursor gases. Surface morphology and chemical composition studies were investigated using atomic force microscopy, scanning electron microscopy, Fourier transform infrared spectroscopy and energy dispersive spectrometry methods. Spectroscopic ellipsometry was used to determine the optical indexes, thicknesses and optical bandgap of the films. The main purpose was to identify the thermo-optical characteristics of layers with different refractive indexes. Thermo-optical studies were performed to determine the temperature hysteresis of optical parameters. These measurements showed that after annealing up to 300 °C and subsequent cooling, the value of optical parameters returned to the initial values.

Optical properties of polymerized ethylene thin films deposited by PECVD technique

Optical properties of polymerized ethylene thin films deposited by PECVD technique

(Invited) The Application of ALD and ALE Passivated MicroLED Display

Micro LED has been engaged to the next generation display technology and evolved for various applications from several electronic manufacturers and institutions. The less than 10×10 μm2 area of micro-LEDs is desired for the high pixel per inch (PPI) of micro display but the sidewall effect from etching process will drop the quantum efficiency. Therefore, a good passivation process is essential to be introduced into micro-LED process to overcome the efficiency droop issue. The passivation technique of atomic layer deposition (ALD) enables to improve the sidewall damages from dry etching and hence the quantum efficiency of micro-LEDs can be enhanced [1, 2]. Furthermore, the improvement can be enhanced within smaller size of micro LEDs. In particular, due to the excellent uniformity and step coverage passivation by ALD Al2O3 thin films, the interest in efficient ALD equipment has gradually increased. The atomic layer etching (ALE) is an advance etching process that promises an excellent depth control in shallow device structures. This paper provides an overview of ALD and ALE process for improving the micro-LED performance.The epitaxial structure of the micro-LED structures was grown on a c-plane sapphire substrate using metal-organic chemical vapor deposition (MOCVD). Following the development of MOCVD, a transparent and ohmic p-contact of indium tin oxide (ITO) with a thickness of 100 nm was deposited by electron-beam evaporation as a transparent and ohmic p-contact. The ITO layer can result in efficient electrical current spreading and provide a transparent emission window for topside emitting devices. N-type GaN, p-type GaN, and the multiple quantum wells (MQWs) active region, which consists of twelve pairs of InGaN wells and a GaN barrier with an emission wavelength of around 445 nm, are the major epitaxial layers. The growth phases of micro-LED processing included mesa etching, ohmic contact metallization, sidewall passivation deposition using Al2O3 of thickness 21.3 nm and SiO2 of thickness 300 nm, and interconnects. The inductively coupled plasma (ICP) dry etching process is used for the mesa etching method, and SiO2 and Al2O3 passivation layers are deposited using PECVD and ALD techniques. Since Al2O3 and SiO2 are well-known dielectric materials for photonic applications, they were selected. Because of the field effect passivation produced by negative fixed charges, Al2O3 has emerged as a unique passivation material for commercial solar cells. The passivation layers tend to prevent surface recombination and reabsorption of emitted light near the etched surface during forward-biased activity. Following the deposition of the dielectric passivation layers, a hole was created using the ICP etching technique for the deposition of metal contacts. The electrode metal consisted of 50/300 nm of Ti/Au for p- and n- metal contacts deposited using electron-beam evaporation followed by rapid thermal annealing. The process flow of ALD passivated micro-LED is shown in Fig. 1(a).Fig. 1(b) showed the effect of the ALD-Al2O3 passivation technique on the EQE enhancement of µ-LEDs. According to the literature, the peak EQE of a small LED is considerably small due to the surface and nonradiative recombination of the mesa layer caused by plasma-assisted dry etching. ALD sidewall passivation is an important method for reducing plasma damage in LEDs. We can observe the 21.3 nm Al2O3 passivation on micro-LED in Fig.1(a). Therefore, Fig. 1 (b) presents the EQEs of 10 × 10-µm2 µ-LEDs with and without an Al2O3 passivation layer deposited using the ALD technology for reducing plasma damage. Compared with the device not subjected to ALD-Al2O3 passivation, the 10 × 10-µm2 array subjected to ALD-Al2O3 passivation exhibited an EQE enhancement of 37.5%. This result proves that ALD sidewall passivation can effectively reduce the sidewall damage caused by SRH nonradiative recombination and thus increase the EQE of small LEDs.

Bismuth (III) oxide / carbon nanocomposites for degradation of indigo carmine dye in aqueous solution

In this work, we reported the synthesis of bismuth (III) oxide (α- Bi2O3)/Carbon nanocomposites using the combination of spin-coating and PECVD techniques. The films obtained consist of bismuth (III) oxide aggregates covered by a carbon matrix. SEM observations showed a porous structure with presence of sheets of about 1 μm size. The optical properties of Bi2O3/C nanocomposites have been determined and it turns out, they are similar to the ones of the Bi2O3 layer. The catalytic effect of the Bi2O3/C nanocomposites were tested by monitoring the degradation of the indigo carmine dye (IC) in a water solution using four experimental process: Ultraviolet (UV)-Visible-Infrared (IR), UV–Visible, UV and IR radiation. The best degradation was obtained using the combination of these radiations.

Effect of thermal annealing on microstructure and optical properties of silver-carbon nanocomposite thin films

We reported a novel and versatile processing for the synthesis of Ag-carbon nanocomposites using the combination of the sputtering and PECVD techniques. The influence of the thermal annealing on the surface morphology, the structure and the optical properties of these films was studied. The effective medium model was used to describe the spectrophotometric measurements. Numerical calculations were allowed determining optical constants. The calculated transition gap Eg was found to vary between 1 and 1.5 eV depending on the annealing temperature. These values are lower than those reported for standard Ag-TiO2 and Ag-ZnO nanocomposites, which is promising for advanced optoelectronic devices.

Boron carbide thin films deposited by RF-PECVD and PLD technique: A comparative study based on structure, optical properties, and residual stress

Radio-Frequency Plasma Enhanced Chemical Vapour Deposition (RF-PECVD), and Pulsed Laser Deposition (PLD) techniques were used to deposit boron carbide (BxC) thin films. Films were investigated to compare crystallinity, chemical composition, optical properties, and residual stress. X-ray diffraction analysis revealed that the film deposited by PLD was amorphous, while PECVD technique yielded crystalline BxC film. PLD technique provided films with better stoichiometric purity with B4C being the most dominant phase, as observed in XPS spectra. However, super-stoichiometric phase (BxC (x > 4)) was dominant in PECVD film. Moreover, the PECVD film had greater adhesion (Lc3 ~29.5 N), hardness (~2798 HK), and lubricity (COF~ 0.03) compared to PLD deposited film. Optically, PECVD deposited film have higher value of refractive indices (1.82 at 600 nm) and lower extinction coefficient. Finally, residual stress measured via substrate curvature method revealed that for PLD 400 C film, the stress was compressive in nature while the same for PECVD -100 V film was tensile, with 10 times less in magnitude. Ultimately, this study provides the user with opportunity to weigh the advantages and disadvantages of PECVD and PLD techniques for deposition of functional BxC films.

Design of Ni/NiO–TiO2/rGO nanocomposites on carbon cloth conductors via PECVD for electrocatalytic water splitting

The facile synthesis and design of noble metal-free efficient catalysts to accelerate the sluggish kinetics of the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is still a big challenge for electrolytic water splitting. In that context, the preparation of efficient catalysts with superior catalytic activity from cheap raw materials on a large scale is crucial. Briefly, Ni/NiO/TiO2/rGO is designed using the environmental-friendly and easily up-scalable PECVD technique. This trinary composite presents significance in regulating the crystalline structure, composition and electronic properties towards superior HER and OER activity in acidic solution as bifunctional electrocatalysts for efficient water splitting. Together with the promising long-term stability and durability, Ni/NiO/TiO2/rGO displays excellent electrocatalytic activity towards HER with η10 of 130 mv vs RHE and a Tafel slope of 40 mV/dec.

Synthesis and thermal simulations of novel encapsulated CNT multifunctional thin-film based nanomaterial of SiO2-CNT and TiN-CNT by PVD and PECVD techniques for thermal applications

This research work focuses on synthesizing novel multi-layer thin-film 2D material which consists of CNTs as-synthesized thin film as the base material. These thin films could be used in various applications such as field emission materials, structural reinforcement, thermal dissipation, etc. Nearly vertically aligned carbon nanotubes (CNTs) were synthesized on a silicon substrate using Radio Frequency Plasma Enhanced Chemical Vapor Deposition (RF PECVD). In the current research, thin films of Titanium Nitride (TiN) and Silicon Dioxide (SiO2) is deposited on CNTs using Physical Vapor Deposition (PVD) technique. Transmission Electron Microscope (TEM) results indicate the presence of polycrystalline and amorphous features in TiN/CNT and SiO2/CNT composites. Energy Dispersive X-Ray Spectroscopy (EDS) in the TEM has been used to identify the deposited elements. Raman spectroscopy was used to determine the sp2, sp3 content and investigate the vibrational signature of molecules for the composites. The hardness of the composites was measured using nanoindentation. The hardness of TiN/CNT and SiO2/CNT calculated using values arising in compression testing of the films together is estimated to be 3.18 GPa and 2.80 GPa respectively. Thermal simulations to near synthesis material were carried out using Ansys software and found that a typical 80 °C temperature could be reduced to room temperature with the composite thin films. Simulations using software estimate the thermal heat flux for Si/CNT/TiN system is 1570 W/mm2 and the same for Si/CNT/SiO2 is 172.45 W/mm2.

Reduction of residual stress in polymorphous silicon germanium films and their evaluation in microbolometers

Hydrogenated polymorphous silicon germanium (pm-SixGe1–x:H) thin films were deposited by the PECVD technique at 200 °C. Three compositions were investigated by changing the silane/germane gas mixture. It was found that the temperature coefficient of resistance (TCR) varies from 2.25% K−1 to 4.26% K−1 while the electrical conductivity ranges from 9.1 × 10−6 S cm−1 to 3.7 × 10−3 S cm−1. On the other hand, the residual stress of as-deposited films was highly compressive reaching values of nearly 700 MPa. After a thermal annealing of 3 hours, it was observed an acceptable reduction and a slight change towards tensile stress. A thin film with low residual stress and high TCR was chosen to manufacture test microbolometers in order to assess if the thermosensing properties of pm-SixGe1–x:H were not affected. After fabricating the microbolometers, their structural conditions were evaluated by scanning electron microscopy and it was found that the reduction of stress significantly improved their mechanical stability and reduced the warping of the membranes. Finally, test structures were characterized at a chopper frequency of 30 Hz, with a DC current of 2.5 μA in a vacuum environment of 20 mTorr. Voltage responsivity of 1.9 × 106 V/W, detectivity of 4.4 × 108 cm ∙ Hz1/2/W, NEP of 1 × 10−11 W/Hz1/2, NETD of 18 mK and 2 ms of thermal response time were measured. In summary, we have studied different process conditions to obtain better pm-SixGe1–x:H films in terms of their electrical and mechanical properties. In this sense, the results obtained with microbolometers show that pm-SixGe1–x:H is a very attractive material to develop infrared vision systems with high sensitivity.

Emitting properties of a-Si:C:H films with a gold submicron grating

In this study reflection and photoluminescence spectra of a-Si:C:H thin film with gold grating on it was examined theoretically and experimentally. The hydrogenated amorphous amorphous silicon-carbon alloy films were fabricated by the PECVD technique. Arrays of gold stripes with different gold width were created by lift-off e-beam lithography. Reflection, and PL spectra has been measured by a Fourier imaging spectroscopy. The theoretical calculations are in a good agreement with experimental results. From the PL spectra it follows, that the TE polarization gives sharper and more efficient PL signal than the TM polarization, and PL efficiency almost does not depend on gold stripes widths. It was shown that only in TE modes the PL outcouples from the gratings owing to the fact that there is no plasmon’s affect in this polarization.

Fabrication of Poly(N-isopropylacrylamide) with Higher Deposition Rate and Easier Phase Transition by Initiated Plasma Enhanced Chemical Vapor Deposition

This study demonstrates the fabrication of thermoresponsive poly(N-isopropylacrylamide) (PNIPAAm) thin films using the initiated PECVD (i-PECVD) method, in which the initiator tert-butyl peroxide was used together with the monomer NIPAAm. The deposition rates, wettability properties, and the low critical solution temperature (LCST) of i-PECVD deposited PNIPAAM were compared with those of classical continuous wave and pulsed PECVD techniques without TBPO. The effect of plasma power, plasma operation mode, substrate temperature and the presence of initiator on the deposition rate and wettability properties of PNIPAAm thin films were investigated. The results showed that it was possible to tune the deposition rate and wettability properties of PNIPAAm thin films by changing the PECVD parameters. The highest deposition rate (47.9 nm/min) and the largest contact angle difference (18.3°) depending on the temperature were obtained using the i-PECVD method. The LCST value of i-PECVD-PNIPAAm was able to be tuned between 31 and 34 °C. Such value was dependent on the presence and amount of the initiator. On the basis of these results, the i-PECVD method can be considered as the most proper approach for producing of PNIPAAm with desired properties.