Oxidative Chemical Vapor Deposition Research Articles

Conductive Fused Porphyrin Tapes on Sensitive Substrates by a Chemical Vapor Deposition Approach.

Oxidative polymerization of nickel(II) 5,15‐diphenyl porphyrin and nickel(II) 5,15‐bis(di‐3,5‐tert‐butylphenyl) porphyrin by oxidative chemical vapor deposition (oCVD) yields multiply fused porphyrin oligomers in thin film form. The oCVD technique enables one‐step formation, deposition, and p‐doping of conjugated poly(porphyrins) coatings without solvents or post‐treatments. The decisive reactions and side reactions during the oCVD process are shown by high‐resolution mass spectrometry. Owing to the highly conjugated structure of the fused tapes, the thin films exhibit an electrical conductivity of 3.6×10−2 S cm−1 and strong absorption in the visible to near‐infrared spectral region. The formation of smooth conjugated poly(porphyrins) coatings, even on sensitive substrates, is demonstrated by deposition and patterning on glass, silicon, and paper. Formation of conductive poly(porphyrins) thin films could enable the design of new optoelectronic devices using the oCVD approach.

Sequential Solution Polymerization of Poly(3,4-ethylenedioxythiophene) Using V2O5 as Oxidant for Flexible Touch Sensors

SummaryVarious in situ synthesis methods have been developed for the polymerization of 3,4-ethylenedioxythiophene monomers, such as electropolymerization, oxidative chemical vapor deposition, and vapor phase polymerization. Meeting industrial requirements through these techniques has, however, proven challenging. Here, we introduce an alternative method to fabricate highly conductive poly(3,4-ethylenedioxythiophene) (PEDOT) films in situ by solution means. The process involves sequential deposition of oxidants (V2O5 in this case) and monomers. Excess reactants and by-products can be completely removed from the PEDOT film by MeOH rinsing. The obtained PEDOT films possess good crystallinity and high doping level, with carrier concentration three orders of magnitude higher than that of the commercial product (PH1000, Heraeus GmbH). The electrical conductivity of the as-cast PEDOT film reaches up to 1,420 S/cm. In addition, this method is fully compatible with large-scale printing techniques. These PEDOT conducting films enable the realization of flexible touch sensors, which demonstrate superior flexibility and sensitivity.

Hall of Fame Article: Device Fabrication Based on Oxidative Chemical Vapor Deposition (oCVD) Synthesis of Conducting Polymers and Related Conjugated Organic Materials (Adv. Mater. Interfaces 1/2019)

Hall of Fame Article: Device Fabrication Based on Oxidative Chemical Vapor Deposition (oCVD) Synthesis of Conducting Polymers and Related Conjugated Organic Materials (Adv. Mater. Interfaces 1/2019)

Device Fabrication Based on Oxidative Chemical Vapor Deposition (oCVD) Synthesis of Conducting Polymers and Related Conjugated Organic Materials

AbstractConducting polymers (CPs) combine electronic conductivity, optical transparency, and mechanical flexibility compatible with lightweight substrates. Due to these features CPs exhibit promising performance for a wide range of applications including electronic, optoelectronic, electrochemical, optochemical, and energy storage and harvesting devices. Fabrication of high‐quality CPs thin film in a large scale is of high demand in multiple industrial sectors. Chemical vapor deposition (CVD) is a promising approach for scale‐up and commercialization of CPs in large‐scale thin film applications by a roll‐to‐roll process. The CVD technique is a versatile deposition technique for fabricating CPs due to its unique combination of characteristics, including formation of conformal coatings, processing at low temperatures, solvent‐free synthesis, uniformity of growth, mechanical flexible films, industrial scale‐up, and substrate‐independence. This review focuses primarily on the oxidative CVD technique for the fabrication of CPs and related conjugated polymers by emphasizing on their applications in devices.

Review on graphene and its derivatives: Synthesis methods and potential industrial implementation

Graphene and its derivatives have gained significant attention of late due to their remarkable physicochemical properties. This review focuses firstly on the synthesis methods of graphene and its derivatives along with their attributes and characterization techniques. This is followed by a discussion of the potential industrial implementation of the synthesis routes. The potential industrial implementation of the graphene synthesis methods are reviewed using the key criteria of cost, process condition, yield, scalability, product quality and environmental impact. The literature data supported that synthesis routes such as oxidative exfoliation-reduction, liquid-phase exfoliation and chemical vapor deposition have the potential to be commercialized due to their ability to produce large amount of high quality graphene. Further development is necessary to overcome barriers such as environmental concerns and the high graphene cost.

Growth Temperature and Electrochemical Performance in Vapor-Deposited Poly(3,4-ethylenedioxythiophene) Thin Films for High-Rate Electrochemical Energy Storage

Poly(ethylene 3,4-dioxythiophene (PEDOT) films synthesized by oxidative chemical vapor deposition (oCVD) display strong electrochemical activity in the region from 2 to 4.2 V vs Li/Li+. By contrast, the more commonly studied PEDOT:polystyrenesulfonate (PSS) films have negligible electrochemical activity in this region. For the oCVD films, its small dopant anions (Cl–) that can easily enter and exit the polymer structure allow exchange with the Li+ counterion in solution, while for PEDOT:PSS, the poly(styrenesulfonate) dopant is a large macromolecule having substantially lower mobility. Here, we seek to elucidate the relationship between the structural characteristics of oCVD PEDOT thin films and their electrochemical properties, particularly in Li-ion electrolyte systems. Specifically, we seek to rationally design the thin-film properties of oCVD PEDOT for high-rate performance and cycle life by varying the film growth temperature. We observe that the dominant effect of increasing growth temperature is an...

Boron Nitride Nucleation Mechanism during Chemical Vapor Deposition

We present nonequilibrium molecular dynamics simulations demonstrating how boron nitride (BN) nanomaterials nucleate during boron oxide chemical vapor deposition (CVD). Chemical reactions between g...

Engineering conformal nanoporous polyaniline via oxidative chemical vapor deposition and its potential application in supercapacitors

Oxidative chemical vapor deposition (oCVD) offers unique advantages in synthesizing and integrating conducting polymers, like polyaniline (PANI), over conventional solution-based techniques, among them its ability to achieve thin films, conformal and uniform coatings, and coatings on topologically complex substrates. In this work, PANI was synthesized by oCVD via oxidative polymerization using aniline monomer and antimony pentachloride oxidant. Fourier transform infrared (FTIR) and X-ray photoelectron spectroscopy (XPS) confirm the formation of PANI. Uniquely, as evidenced by scanning electron microscopy (SEM) and atomic force microscopy (AFM), oCVD PANI shows a rough nanoporous morphology with pore openings of around 20 nm, while maintaining the conformality and uniformity of the coating. This nanoscale porosity leads to greater surface area that enhanced the energy storage capacity of non-porous electrospun carbon nanofibers (CNFs). With a coating thickness of ∼160 nm on CNFs, the oCVD PANI-CNF composite shows high specific capacitance and excellent cycling stability, and demonstrates the potential for porous oCVD PANI to enhance supercapacitor energy storage and power density.

Oxidative Chemical Vapor Deposition: Nanostructured Unsubstituted Polythiophene Films Deposited Using Oxidative Chemical Vapor Deposition: Hopping Conduction and Thermal Stability (Adv. Mater. Interfaces 9/2018)

Oxidative Chemical Vapor Deposition: Nanostructured Unsubstituted Polythiophene Films Deposited Using Oxidative Chemical Vapor Deposition: Hopping Conduction and Thermal Stability (Adv. Mater. Interfaces 9/2018)

Oxidative Chemical Vapor Deposition of 3D Graphene Oxide on Nickel Foam for Hydrogen Evolution Reaction in Acidic Electrolyte

The development of cheaper non-noble metal electrocatalysts for hydrogen evolution reaction (HER) that can withstand in acidic environment is one attractive route for renewable energy applications. The 3D graphene oxide on nickel skeleton has been recently developed as electrocatalyst in acid solution since it is less expensive than existing noble metal-based catalysts and yet exhibits promising potential for efficient reaction between molecules such as H2O, H2, NH3, O2 etc. In this work, the 3D graphene oxide was synthesized as a thin film coated on Ni foam substrate by the CVD method using methanol and water as a carbon precursor and a weak oxidizing agent, respectively. The influence of oxidation level of 3D graphene oxide to the overpotential, Tafel slope, and band gap energy was investigated in 0.5 M H2SO4 solution. It was found that 3D graphene oxide can improve electrocatalytic property of Ni by the oxygen-functional groups, which can act as an alternative path for H2 production by the recombination of the spilled Hads from Ni. This novel 3D graphene oxide/ nickel foam may be a good electrocatalyst for practically producing H2 fuel.

Ammonium-tungstate-promoted growth of boron nitride nanotubes

Ammonium tungstate ((NH4)10W12O41 · xH2O) is a kind of oxygen-containing ammonium salt. The following study proves that it can be successfully used as a metal oxide alternative to produce boron oxide (B2O2) by oxidizing boron (B) in a traditional boron oxide chemical vapor deposition (BOCVD) process. This special oxidant promotes the simplistic fabrication of boron nitride nanotubes (BNNTs) in a conventional horizontal tube furnace, an outcome which may have resulted from its strong oxidizability. The experimental results demonstrate that the mole ratio of B and (NH4)10W12O41 · xH2O is a key parameter in determining the formation, quality and quantity of BNNTs when stainless steel is employed as a catalyst. We also found that Mg(NO3)2 and MgO nanoparticles (NPs) can be used as catalysts to grow BNNTs with the same precursor. The BNNTs obtained from the Mg(NO3)2 catalyst were straighter than those obtained from the MgO NP catalyst. This could have been due to the different physical forms of the catalysts that were used.

Nanostructured Unsubstituted Polythiophene Films Deposited Using Oxidative Chemical Vapor Deposition: Hopping Conduction and Thermal Stability

AbstractUnsubstituted polythiophene (PT), a promising material that is challenging to process into thin films due to its intrinsic insolubility, can be synthesized and deposited using unique oxidative chemical vapor deposition (oCVD) at room temperature. The conduction mechanism of nanostructured oCVD PT thin films is illuminated through the investigation of in situ conductivity measurements. It is identified that the 3D variable range hopping process governs the transport of charge carriers in oCVD PT thin films with an activation energy of ≈48 meV regardless of doping concentrations. It is also reported that the thermal stability of oCVD PT largely relies on the doping concentration of the material; oCVD PT demonstrates excellent thermal stability at temperatures up to 160 °C with carrier density values lower than ≈1 × 1017 cm−3, while higher doping leads to a reduction in conductivity at T >≈ 100 °C due to electron–hole recombination. X‐ray photoelectron spectroscopy analyses on the change in the concentrations of dopant anions (Cl− and FeCl4−) support the suggested mechanisms.

Molecular engineered conjugated polymer with high thermal conductivity.

Traditional polymers are both electrically and thermally insulating. The development of electrically conductive polymers has led to novel applications such as flexible displays, solar cells, and wearable biosensors. As in the case of electrically conductive polymers, the development of polymers with high thermal conductivity would open up a range of applications in next-generation electronic, optoelectronic, and energy devices. Current research has so far been limited to engineering polymers either by strong intramolecular interactions, which enable efficient phonon transport along the polymer chains, or by strong intermolecular interactions, which enable efficient phonon transport between the polymer chains. However, it has not been possible until now to engineer both interactions simultaneously. We report the first realization of high thermal conductivity in the thin film of a conjugated polymer, poly(3-hexylthiophene), via bottom-up oxidative chemical vapor deposition (oCVD), taking advantage of both strong C=C covalent bonding along the extended polymer chain and strong π-π stacking noncovalent interactions between chains. We confirm the presence of both types of interactions by systematic structural characterization, achieving a near-room temperature thermal conductivity of 2.2 W/m·K, which is 10 times higher than that of conventional polymers. With the solvent-free oCVD technique, it is now possible to grow polymer films conformally on a variety of substrates as lightweight, flexible heat conductors that are also electrically insulating and resistant to corrosion.

Thermal conductivity of poly(3,4-ethylenedioxythiophene) films engineered by oxidative chemical vapor deposition (oCVD).

Oxidative chemical vapor deposition (oCVD) is a versatile technique that can simultaneously tailor properties (e.g., electrical, thermal conductivity) and morphology of polymer films at the nanoscale. In this work, we report the thermal conductivity of nanoscale oCVD grown poly(3,4-ethylenedioxythiophene) (PEDOT) films for the first time. Measurements as low as 0.16 W m−1 K−1 are obtained at room temperature for PEDOT films with thicknesses ranging from 50–100 nm. These values are lower than those for solution processed PEDOT films doped with the solubilizing agent PSS (polystyrene sulfonate). The thermal conductivity of oCVD grown PEDOT films show no clear dependence on electrical conductivity, which ranges from 1 S cm−1 to 30 S cm−1. It is suspected that at these electrical conductivities, the electronic contribution to the thermal conductivity is extremely small and that phonon transport is dominant. Our findings suggest that CVD polymerization is a promising route towards engineering polymer films that combine low thermal conductivity with relatively high electrical conductivity values.

Sequential Solution Polymerization of Poly(3,4-Ethylenedioxythiophene) Using V<Sub>2</Sub>O<Sub>5</Sub> as Oxidant for Flexible Touch Sensors

Various in-situ synthesis methods have been developed for the polymerization of 3,4-ethylenedioxythiophene (EDOT) monomers, such as electro-polymerization (EP), oxidative chemical vapor deposition (OCVD) and vapor phase polymerization (VPP). Additional to these existing techniques, here a novel and facile method is introduced to fabricate highly conductive poly(3,4-ethylenedioxythiophene) (PEDOT) films in-situ by solution means. The process contains sequential deposition of oxidants and monomers. V2O5 is introduced as the oxidant in this synthetic route. Excess reactants and by-products can be completely removed from the PEDOT film by MeOH-rinsing. The obtained PEDOT films possess good crystallinity and high doping level, with carrier concentration three orders of magnitude higher than the commercial product (PH1000, Heraeus GmbH). The electrical conductivity of the as-cast PEDOT film reaches up to 1420 S/cm. In addition, this method is fully compatible with large-scale printing techniques. A 15 cm × 12 cm PEDOT film is printed on polyethylene terephthalate (PET) substrate by bar coating. These PEDOT conducting films enable the realization of flexible touch sensors, which demonstrate superior flexibility and sensitivity. The low-cost and highly efficient synthetic method shows great potential for large-scale production of PEDOT films that have wide applications in electromagnetic shielding, antistatic coating, sensor, etc.

Oxidative chemical vapour deposition of a graphene oxide carbocatalyst on 3D nickel foam as a collaborative electrocatalyst towards the hydrogen evolution reaction in acidic electrolyte

In this study, a graphene oxide (GO) carbocatalyst was synthesized as a thin film on a 3D Ni foam substrate (GO@Ni) by oxidative chemical vapour deposition (CVD) using methanol and water as precursors.

Chemical vapor deposition - based synthesis of conductive polydopamine thin-films

Polydopamine (PDA) represents a family of synthetic bio-inspired pigments offering high functional activity combined with semiconducting properties. To date, it represents one of the main synthetic biopolymers used mainly because of its simple synthesis in aqueous solutions. Thereby dopamine polymerizes in the presence of ambient oxygen to polydopamine. However, its structure renders a sophisticated backbone relating to variations of ambient growth parameters such as temperature, local pH and partial oxygen pressure; preponderant repeating units found in aqueous polydopamine are 5,6-hydroxyl-indole derivatives. However, hydrogen-bonded aggregation competes with the polymerization leading to complex systems. In order to reduce the aggregation we hypothesized that acidic oxidants will direct the polymerization towards CC coupling and hence create synthetic biopolymers.In this work we demonstrate oxidative chemical vapor deposition (o-CVD) for PDA, where we obtain the desired consistent biopolymer thin-films as shown by structural analysis. Furthermore, as-gained polydopamine is conductive and renders fingerprint signatures of free charge carriers. Concomitantly it preserves its functionality – imperative for potential applications in catalysis or as bio-linker.

Deposition Dependent Ion Transport in Doped Conjugated Polymer Films: Insights for Creating High‐Performance Electrochemical Devices

AbstractCharge conduction and redox events in films of doped conjugated polymers are necessarily accompanied by counterion transport. However, insights into how deposition conditions affect ion transport in a structurally diverse set of doped conjugated polymer films and across a polymer/electrolyte interface have not been gathered. Here, cyclic voltammetry and electrogravimetry measurements are used to probe solvent and ion transport across a doped conjugated polymer/electrolyte interface. A representative polymer, p‐doped poly(3,4‐ethlyenedioxythiophene) (PEDOT), obtained using two different deposition methods, vapor phase polymerization (VPP) and oxidative chemical vapor deposition (oCVD), is studied. PEDOT films obtained via VPP and oCVD display dissimilar morphologies at the micro‐ and nanometer length scales, resulting in significantly differing swelling behavior, mass trapping, and ion transport upon exposure to a periodic applied potential. PEDOT films obtained using oCVD display notable permselectivity and near‐ideal mass transport during repeated doping/dedoping cycles in various electrolytes, indicating that these films are robust electroactive materials. This study underlines the extent to which film deposition conditions affect ion transport across polymer/electrolyte interfaces and provides insights into optimal film forming conditions for high‐performance supercapacitors and electrochemical transistors.

Chemical Vapor Deposition of Thin, Conductive, and Fouling-Resistant Polymeric Films.

Fouling has been a persistent issue within applications ranging from membrane separation to biomedical implantation. Research to date focuses on fouling-resistant coatings, where electrical conductivity is unnecessary. In this study, we report the synthesis of multifunctional thin films with both fouling resistance and electrical conductivity for their potential applications in the electrolysis-based self-cleaning of separation membranes and in the field of bioelectronics. This unique combination of properties results in multifunctional coatings that are a zwitterionic derivative of intrinsically conductive polymer poly(3,4-ethylenedioxythiophene) (PEDOT) synthesized via oxidative chemical vapor deposition (oCVD). Their fouling resistance is shown to be comparable to that of known dielectric fouling-resistant surfaces, such as a poly(4-vinylpyridine)-co-divinylbenzene (p4VP-DVB)-derived zwitterionic coating, an amphiphilic poly(1H,1H,2H,2H-perfluorodecyl acrylate-co-2-hydroxyethyl methacrylate) (pPFDA-HEMA) coating, and a glass surface, and are far superior to the fouling resistance of gold or polydimethylsiloxane (PDMS) surfaces. The fouling resistances of seven surfaces are quantitatively characterized by molecular force probe (MFP) analysis. In addition, four-point probe electrical measurements, Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), variable-angle spectroscopic ellipsometry (VASE), profilometry, water contact angle (WCA) measurements, surface ζ-potential measurements, and atomic force microscopy (AFM) were employed to characterize the physiochemical properties and morphology of the different surfaces.

Boron nitride nanotubes grown on stainless steel from a mixture of diboron trioxide and boron

Boron nitride nanotubes (BNNTs) can be grown on stainless steel by annealing a mixture of diboron trioxide (B2O3) and boron (B) at 1200–1300°C under ammonia (NH3). In previously reported boron oxide chemical vapor deposition methods for the synthesis of BNNTs, diboron dioxide (B2O2) is generated in situ by the reaction of boron and metal oxides. In this study, we directly used a mixture of B2O3 and boron as boron sources, thereby, avoiding the use of metal containing species in the starting material. The concentration of B2O3 significantly influenced the formation, quality and quantity of BNNTs.