Chemical vapour deposition (CVD) is a powerful technology for producing high-quality solid thin films and coatings. While widely used in modern industries, it is continuously being developed as it is adapted to new materials. Today, CVD synthesis is being pushed to new heights with the precise manufacturing of both inorganic thin films of two-dimensional (2D) materials and high-purity polymeric thin films that can be conformally deposited on various substrates. In this Primer, an overview of the CVD technique including instrument construction, process control, material characterization, and reproducibility issues is provided. By taking graphene, 2D transition metal dichalcogenides (TMDs) and polymeric thin films as typical examples, the best practices for experimentation involving substrate pre-treatment, hightemperature growth and post-growth processes are presented. Recent advances and scaling-up challenges are also highlighted. By analyzing current limitations and optimizations, we also provide insight into possible future directions for the method, including reactor design for highthroughput and low-temperature growth of thin films.

REBa2Cu3Ox ((REBCO), RE = rare earth) superconductor tapes with moderate levels of dopants have been optimized for high critical current density in low magnetic fields at 77 K, but they do not exhibit exemplary performance in conditions of interest for practical applications, i.e., temperatures less than 50 K and fields of 2–30 T. Heavy doping of REBCO tapes has been avoided by researchers thus far due to deterioration in properties. Here, we report achievement of critical current densities (Jc) above 20 MA/cm2 at 30 K, 3 T in heavily doped (25 mol. % Zr-added) (Gd,Y)Ba2Cu3Ox superconductor tapes, which is more than three times higher than the Jc typically obtained in moderately doped tapes. Pinning force levels above 1000 GN/m3 have also been attained at 20 K. A composition map of lift factor in Jc (ratio of Jc at 30 K, 3 T to the Jc at 77 K, 0 T) has been developed which reveals the optimum film composition to obtain lift factors above six, which is thrice the typical value. A highly c-axis aligned BaZrO3 (BZO) nanocolumn defect density of nearly 7 × 1011 cm−2 as well as 2–3 nm sized particles rich in Cu and Zr have been found in the high Jc films.

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lightweight, wearable, and stretchable properties of CPs relative to traditional materials highlight the areas where CPs may find their niche in modern devices. [2] The fabrication of uniform CPs in large scale with high throughput roll-to-roll process is of great importance in industrial sectors. To achieve this purpose, chemical vapor deposition (CVD) along with other vapor deposition methods are the promising approaches to expedite the commercialization process of CPs in large-scale applications.For polymers which dissolve, films can be formed by solution-based methods such as dip-coating and spin-coating. However, CPs, particularly those formed from unfunctionalized monomers, are often insoluble or require solvents which are unsafe and costly to use. The lack of solubility is typically associated with a rigid backbone structure that promotes crystallite formation. As a result, dissolution requires overcoming the associated enthalpy of crystallization.The need for solubilizing polymers is eliminated by employing CVD as the thin film formation technique. A variety of different CVD processes have been developed for vapor phase reactants to undergo similar polymerization mechanisms as those reported for solution synthesis. [3] These include CVD polymer methods for chain growth by free radical or cationic initiation, or by condensation polymerization. For most conjugated macromolecules, the desired variant of the CVD method needs to mimic the step-growth polymerization mechanism in order to obtain optimized properties, such as electrical conductivity. This motivated the invention of oxidative CVD (oCVD) in which the vacuum chamber design, strategy for reactant vapor introduction, and process conditions are optimized for step-growth polymerization. Vapor deposition methods which are not mechanistically motivated, such as thermal evaporation, pulsed laser deposition, and plasma-enhanced CVD, can result in conjugated polymer films having properties that are insufficient for integration into many types of devices. Thus, one major significance of achieving conjugated polymers having highly desirable characteristics by oCVD is the ability to fabricate state-of-the-art optoelectronic and energy storage devices.The oCVD process is a single-step method to convert vapor phase monomers, along with vapors of oxidant, into thin CP films. [3,4] At the surface of the substrate, step-growth Conducting 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 versati...

Engineering the texture and nanostructure to improve the electrical conductivity of semicrystalline conjugated polymers must address the rate-limiting step for charge carrier transport. In highly face-on orientation, the charge transport between chains within a crystallite becomes rate-limiting, which is highly sensitive to the π-π stacking distance and interchain charge transfer integral. Here, face-on oriented semicrystalline poly(3,4-ethylenedioxythiophene) (PEDOT) thin films are grown via water-assisted (W-A) oxidative chemical vapor deposition (oCVD). Combining W-A with the volatile oxidant, antimony pentachloride, yields an optimized electrical conductivity of 7520 ± 240 S cm −1 , a record for PEDOT thin films. Systematic control of π-π stacking distance from 3.50 Å down to 3.43 Å yields an electrical conductivity enhancement of ≈1140%. The highest electrical conductivity also corresponds to minimum in Urbach energy of 205 meV, indicating superior morphological order. The figure of merit for transparent conductors, σ dc /σ op , reaches a maximum value of 94, which is 1.9× and 6.7× higher than oCVD PEDOT grown without W-A and utilizing vanadium oxytrichloride and iron chloride oxidizing agents, respectively. The W-A oCVD is single-step all-dry process and provides conformal coverage, allowing direct growth on mechanical flexible, rough, and structured surfaces without the need for complex and costly transfer steps.