Chemical Vapor Deposition Technology Research Articles

Structure Modulation and Self-Lubricating Properties of Porous TiN–MoS2 Composite Coating Under Humidity–Fluctuating Conditions

To improve the friction performance and service life of protective coatings in humidity-fluctuating environments, porous hard titanium nitride (TiN)–molybdenum disulfide (MoS2) composite coatings were prepared by using direct current magnetron sputtering (DCMS) with the mode of oblique angle deposition (OAD) and chemical vapor deposition (CVD) technologies. The structure and chemical component were characterized by field emission scanning electron microscopy (FESEM), energy dispersive spectrometer (EDS), grazing incidence X-ray diffraction (GIXRD), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. The tribological properties of these TiN–MoS2 composite coatings were investigated. The results indicate that the porous TiN–MoS2 composite coating exhibited outstanding friction performance and long service life under humidity-fluctuating environments. At the initial 20% relative humidity (RH) stage, the MoS2 on the porous TiN–MoS2 composite coating surface worked as an effective lubricant; thus, the coating demonstrated excellent lubrication performance, and the friction coefficient (COF) was about 0.05. As the humidity was alternated to 70% RH, the lubrication effect diminished due to the production of molybdenum oxide (MoO3), and the COF was about 0.2, which was attributed to the degradation of MoS2 on the wear track and the release of fresh MoS2 from the porous TiN matrix. After the environmental conditions shifted from 70% to 20% RH, the MoO3 was removed, and the lubrication effect was restored. In summary, TiN–MoS2 porous composite coating offers a promising approach for lubrication in humidity-fluctuating environments.

Increasing the Wear Resistance of Stamping Tools for Coordinate Punching of Sheet Steel Using CrAlSiN and DLC:Si Coatings

The punching of holes or recesses on computer numerical control coordinate presses occurs in sheets at high speeds (up to 1200 strokes/min) with an accuracy of ~0.05 mm. One of the most effective approaches to the wear rate reduction of stamping tools is the use of solid lubricants, such as wear-resistant coatings, where the bulk properties of the tool are combined with high microhardness and lubricating ability to eliminate waste disposal and remove oil contaminants from liquid lubricants. This work describes the efficiency of complex CrAlSiN/DLC:Si coatings deposited using a hybrid unit combining physical vapor deposition and plasma-assisted chemical vapor deposition technologies to increase the wear resistance of a punch tool made of X165CrMoV12 die steel during coordinate punching of 4.0 mm thick 41Cr4 carbon structural steel sheets. The antifriction layer of DLC:Si allows for minimizing the wear under thermal exposure of 200 °C. The wear criterion of the lateral surface was 250 μm. The tribological tests allow us to consider the CrAlSiN/DLC:Si coatings as effective in increasing the wear resistance of stamping tools (21,000 strokes for the uncoated tool and 48,000 strokes for the coated one) when solving a wide range of technological problems in sheet stamping of structural steels.

One-step fabrication of high energy storage polymer films with a wide bandgap and high melting temperature induced by the fluorine effect for high temperature capacitor applications with ultra-high efficiency.

The development of polymer dielectrics with both high energy density and low energy loss is a formidable challenge in the area of high-temperature dielectric energy storage. To address this challenge, a class of polymers (Parylene F) are designed by alternating fluorinated aromatic rings and vinyl groups in the polymer chain to confine the conjugating sequence and broaden the bandgap with the fluorine effect. The target films with desired thickness, ultra-high purity, and a wide bandgap are facilely fabricated by a one-step chemical vapor deposition (CVD) technique from monomers. The symmetric and bulky aromatic structures exhibit high crystalline performance and excellent stability at high temperature. The presence of strongly electronegative fluorine atoms effectively enhances bandgap and electron trapping capability, which effectively reduces the conduction loss as well as the possibility of breakdown at high temperatures. CVD technology avoids the post-processing film-forming process, ensuring the fabrication of thin films with high quality. These benefits allow Parylene F films to effectively store electrical energy at temperature up to 150 °C, exhibiting a record discharged energy density of 2.92 J cm-3 at charge-discharge efficiency exceeding 90%. This work provides a new idea for the design and synthesis of all-organic polymer dielectric films for high temperature applications.

Nucleation study of AlN crystal growth on 6H-SiC substrates using the MOCVD

This study delves into the nucleation process of AlN crystal growth on a 6H-SiC substrate using metal-organic chemical vapor deposition technology through molecular dynamics simulations and experimental research. It was found that AlN predominantly exhibits an island growth mode, with nucleation morphologies mainly being triangular and hexagonal. This paper provides a detailed analysis of the surface morphology and atomic structure of AlN thin films and compares the fusion processes of the crystals. Through simulations, this study reveals the formation energy and adsorption energy of different nucleation morphologies and their adsorption capacities for Al and N atoms. Additionally, the research observed various types of stacking faults that may occur during the AlN thin film growth process and explored the formation mechanisms of these faults and their impact on the quality of subsequent films. Ultimately, it concludes that hexagonal AlN with double-bonded Al atoms at the edges possesses more stable structural formation energy and stronger adsorption capacity, which contributes to the outward expansion of its edges but may also lead to a transition of the nucleation morphology to triangular.

Covering a 1280–1495 nm (215 nm) wideband high-gain bismuth-doped fiber amplifier with only 1240 nm pumping

In this study, two bismuth-doped fibers were fabricated by atomic layer deposition (ALD) combined with modified chemical vapor deposition (MCVD) technology. For a dual-pump amplification configuration, 1240 and 1310 nm pumping the BDF simultaneously, when the 1240 nm pump power changes, it has little impact on the gain. The 1310 nm pump wavelength overlaps with the emission range of bismuth active centers associated with phosphorus (BACs-P), potentially suppressing its excitation. The experiment reveals that the emission range of BACs associated with silicon (BACs-Si) overlaps the absorption range of BACs-P, indicating that BACs likely exist for their reabsorption properties. Furthermore, enhancing the reabsorption properties can increase the luminescent intensity of BACs-Si in the 1420 nm region with only a 1240 nm pump. The gain of peaks at 1340 and 1420 nm exceeds 31.5 dB at a −23 dBm input signal. Notably, the gain within the 1280–1495 nm range exceeded 15 dB, achieving a bandwidth of 215 nm. This holds significant promise for applications in artificial intelligence, autonomous driving, and other fields with high-capacity communication demands.

HWCVD growth of hydrogenated nanocrystalline silicon oxide window layers for SHJ solar cells

In recent years, successful development of n-type hydrogenated nanocrystalline silicon oxide (n-nc-SiOx:H) window layers with high conductivity and low parasitic absorption, grown by plasma enhanced chemical vapor deposition (PECVD) technology, has significantly enhanced the power conversion efficiency of silicon heterojunction (SHJ) solar cells. Although SHJ solar cells have significant advantages in efficiency, the high cost of the PECVD equipment presents a significant barrier to their mass production. The utilization of the more cost-effective hot wire chemical vapor deposition (HWCVD) technology presents a promising solution. Nevertheless, HWCVD technology currently lacks an industrially viable methodology for growing high-performance window layers due to a phenomenon of associated severe loss of passivation. In this work, the phenomenon and the solution have been investigated. The results demonstrate that, in HWCVD processes, large amounts of hydrogen and small amounts of oxygen, which are essential for enhancing the crystallinity and conductivity and reducing the parasitic absorption, both induce significant damage to the previously grown intrinsic hydrogenated amorphous silicon layer, leading to poor passivation, and hence much lower cell efficiency. Introduction of a densified amorphous silicon barrier layer was found to be an effective solution to the aforementioned passivation loss, resulting in the successful growth of nc-SiOx:H window layers by HWCVD, with an efficiency enhancement of 0.37%abs. Finally, a commercial-size SHJ solar cell with an efficiency of 24.74 % was fabricated using a home-made HWCVD-based pilot SHJ cell line.

Heat treatment and codeposition of Co and Al on nickel-based superalloy DZ411 by CVD process

Co-deposition of aluminide coatings on the inner and outer surfaces of turbine blades using chemical vapor deposition (CVD) technology is a major challenge in the field of advanced materials engineering. To overcome this challenge, a sub-aluminum generator device was designed and Co-Al coatings with typical β-NiAl microstructure were successfully obtained on the inner and outer surfaces of the turbine blades in the present study. In addition, the effects of different heat treatment processes on the microstructures of the Co-Al coatings were also investigated, and the results show that the addition of heat treatment process can easily lead to the thinning of Co-Al coating thickness, the increase of oxidation degree as well as the emergence of different types of topological close packing (TCP) phases. The serious loss of Al would also lead to the occurrence of transition from β-NiAl phase to γʹ-Ni3Al phase. This study not only breaks through the limitations of conventional CVD equipment, but also provides valuable insights into the microstructural evolution of Co-Al coatings under different heat treatment conditions, and provides necessary conditions for further exploration of co-deposition technology for different types of coatings.

Electronics and Optoelectronics Based on Tellurium.

As a true 1Dsystem, group-VIA tellurium (Te) is composed of van der Waals bonded molecular chains within a triangular crystal lattice. This unique crystal structure endows Te with many intriguing properties, including electronic, optoelectronic, thermoelectric, piezoelectric, chirality, and topological properties. In addition, the bandgap of Te exhibits thickness dependence, ranging from 0.31eV in bulk to 1.04eV in the monolayer limit. These diverse properties make Te suitable for a wide range of applications, addressing both established and emerging challenges. This review begins with an elaboration of the crystal structures and fundamental properties of Te, followed by a detailed discussion of its various synthesis methods, which primarily include solution phase, and chemical and physical vapor deposition technologies. These methods form the foundation for designing Te-centered devices. Then the device applications enabled by Te nanostructures are introduced, with an emphasis on electronics, optoelectronics, sensors, and large-scale circuits. Additionally, performance optimization strategies are discussed for Te-based field-effect transistors. Finally, insights into future research directions and the challenges that lie ahead in this field are shared.

Stoichiometry modulated tunable optoelectronic properties of Nb-doped WS2 synthesized by chemical vapor deposition method.

Significant progress has been made in the field of two-dimensional WS2, yet the precise control of the doping process to achieve desired properties and the interpretation of complex physical phenomena in these novel materials necessitate thorough research. In this study, Nb-doped WS2 is synthesized using chemical vapor deposition technology, leading to triangular flakes with a side length of 12-20μm. The X-ray photoelectron spectroscopy analysis indicates that the NbW substitution defect functions as an electron acceptor. The interlayer and transverse forces of the Nb-doped WS2 flake approach 1 nN and 150 pN, respectively. As the doping concentration increases, the valence band maximum energy of Nb-doped WS2 ranges from 4.06eV to 4.3eV. Furthermore, the performance of the photodetector is discussed.

Influence of Si flow rate on the performance of MOCVD-deposited Si-doped Ga2O3 films and the applications in ultraviolet photodetectors

In this work, the Metal-organic Chemical Vapor Deposition (MOCVD) technology was used to successfully grow Si-doped β-Ga2O3 films on C-plane sapphire substrates. The effects of Si flow rate on the surface morphology, crystal composition, electrical and optical properties of the films were characterized and analyzed. The experimental results show that the full width at half maximum (FWHM) and root mean square (RMS) of the films are improved with the decrease of Si flow rate. More importantly, only the sample with the lowest Si flow rate showed conductive ability, and its carrier concentration and mobility were 4.20 cm2/V·s and 3.33 × 1016 cm−3, respectively. In addition, we also made photodetectors corresponding to the thin films. The test results showed that the external quantum efficiency (EQE) and responsiveness (R) of the detectors improved with the decrease of Si flow rate.

Patterned 3D-graphene for self-powered broadband photodetector

The remarkable ultra-wideband energy capabilities of zero-bandgap two-dimensional (2D) graphene have made it an outstanding material for photon absorption and charge carrier generation across a broad spectrum. However, atomically thick 2D-graphene only exhibits a light absorption efficiency of 2.3%, posing a challenge for graphene-based photodetectors to harness photon energy effectively. This study utilized plasma-enhanced chemical vapor deposition technology and a mask to create in situ patterned 3D-graphene/Si-based Schottky heterojunctions. The porous structure and natural nano-resonant cavities of the 3D-graphene enhanced the probability of light absorption, while the curved and sharp edges and corners of the patterned 3D-graphene concentrated the local electromagnetic field and induced localized surface plasmon resonance. Both theoretical and experimental analyses confirmed the improved light absorption mechanisms and charge transfer of photogenerated carriers under the built-in electric field. The photodetector based on the patterned 3D-graphene/Si Schottky structure exhibits excellent broadband response characteristics spanning from 380 to 1550 nm, with responsivity and specific detectivity of 68.47 A/W and 1.43 × 1012 Jones at a wavelength of 1550 nm. Furthermore, the photodetector demonstrated ultrafast microsecond-level response times (116/120 μs rise/fall times) along with exceptional stability and reliability. The potential applications of as-fabricated photodetector include logic devices such as “AND” and “OR” gates and information encryption. This research holds valuable scientific significance for the design of future optoelectronic devices and provides crucial insights and technical support for developing high-performance Si-based graphene detectors.

Multi-interfaced FeCoNi@C/carbon cloth composites for eliminating electromagnetic wave pollution

To tackle the increasing electromagnetic pollution, new and efficient electromagnetic wave absorption (EWA) and shielding (EWS) materials are urgently needed. Multi-component synergism and complex microstructure design are effective measures to improve the EWA and EWS properties. However, how to implement the above designs still faces huge challenges. Herein, multi-interface carbon-coated FeCoNi nanoneedles grown on carbon cloth (FeCoNi@C/CC) were synthesized by a combination of hydrothermal process and chemical vapor deposition (CVD) technology with the concept of “green synthesis”. Using acetylene as the carbon source and atmosphere, the FeCoNi ternary hydroxide can be transformed into a multiple magnetic component (Fe3O4, Ni, and Co metals) by simple annealing. Simultaneously, a uniform carbon layer is formed on the surface, resulting in a composite system with a variety of heterogeneous interfaces and loss mechanisms. Additionally, the dielectric and magnetic loss capacities can be effectively adjusted by changing the temperature of CVD. The optimized FeCoNi@C/CC as filler exhibits remarkable EWA performance with a minimum reflection loss of −69.3 ​dB at a thickness of 1.82 ​mm and a maximum effective absorption bandwidth of 6.80 ​GHz. Moreover, the composites as an integrated component also show a fascinating electromagnetic interference shielding efficiency of 42.2 ​dB. This work provides a guide for the structural design of high-performance electromagnetic protection materials with multi-heterogeneous interfaces.

Directional growth of graphene by microwave plasma CVD constructed TiO2@Ag@graphene ternary junction for efficient hydrogen production

This work proposes a novel strategy which the microwave plasma chemical vapor deposition (MPCVD) technology was used as one important preparation process for synthesizing TiO2@Ag@graphene ternary junction. The ternary junction exhibits an enhanced photocatalytic hydrogen production rate of 4.44 mmol·g−1·h−1, which is approximately 9.25 times higher than that of pure TiO2 (0.48 mmol·g−1·h−1). The remarkable photocatalytic activity can be attributed to the strong synergistic effect between TiO2@Ag and graphene. The loaded Ag and graphene can not only act as electronic conductors to effectively promote the separation of charges, but also obviously improve the response of visible light of TiO2. The photogenerated electrons are transferred from TiO2 to graphene via the Ag medium was further verified by DFT calculations. Constructing an Ag-graphene interface can activate carbon atoms, which can quickly capture electron to fill the π* orbital of graphene. TiO2@Ag@graphene ternary junction exhibits a lower ΔGH* value of 0.51 eV than that of TiO2@Ag (1.49 eV), which indicates that TiO2@Ag@graphene ternary junction with optimal absorption energy for the hydrogen intermediate.

Nitrogen-Doped 3D-Graphene Advances Near-Infrared Photodetector for Logic Circuits and Image Sensors Overcoming 2D Limitations.

The limitations of two-dimensional (2D) graphene in broadband photodetector are overcome by integrating nitrogen (N) doping into three-dimensional (3D) structures within silicon (Si) via plasma-assisted chemical vapor deposition (PACVD) technology. This contributes to the construction of vertical Schottky heterojunction broad-spectrum photodetectors and applications in logic devices and image sensors. The natural nanoscale resonant cavity structure of 3D-graphene enhances photon capture efficiency, thereby increasing photocarrier generation. N-doping can fine-tune the electronic structure, advancing the Schottky barrier height and reducing dark current. The as-fabricated photodetector exhibits exceptional self-driven photoresponse, especially at 1550 nm, with an excellent photoresponsivity (79.6 A/W), specific detectivity (1013 Jones), and rapid response of 130 μs. Moreover, it enables logic circuits, high-resolution pattern image recognition, and broadband spectra recording across the visible to near-infrared range (400-1550 nm). This research will provide new views and technical support for the development and widespread application of high-performance semiconductor-based graphene broadband detectors.

SPECIFICS OF DESIGNING AN INFRARED PYROMETER-REFLECTOMETER FOR SEMICONDUCTOR HETEROSTRUCTURE FABRICATION

There are general technical requirements for all types of reactors for chemical vapour deposition technology using AIII- BV metalorganic compounds. Among them, it is worth highlighting the large temperature gradients that cause the origin of convection loops, which in turn, taking into account the high speed of the gas flow, lead to turbulence in the reactor instead of the expected laminar flow. It is also important to take into account the change in parameters of the wafer surface during the growth process and the need for signal separation between the useful signal from the wafer surface and the background signal from the wafer carrier, which rotates at fixed speed for uniform deposition of compounds. To obtain high-quality heterostructures with reproducible parameters, it is important to have a system of precise temperature control on the wafer surface directly in the deposition area, since the deposition process for many complex semiconductor devices (for example, laser diodes, LEDs, photodiodes, transistors on heterojunctions) is very sensitive to temperature changes. The method of optical pyrometry is a non-contact method that allows to precisely determine the temperature of the wafer surface and meets the technical requirements of CVD epitaxy growth reactors. This article is devoted to the analysis of the features of the development of optoelectronic systems for precise temperature measurement during epitaxial growth in order to determine the criteria for the selection or development of components of the optoelectronic system of the pyrometer-reflectometer. The main physical processes, electro-optical characteristics of Si photodiode, AlGaAs/GaAs LED and parameters of bandpass interference filters were investigated. Based on the analysis of the obtained research and measurement results, scientific recommendations have been developed. The recommendations aimed at the selection and optimization of the parameters of the components of the pyrometer-reflectometer (photodetectors, light emitting diodes, optical filters) in order to improve the accuracy and temperature stability of measurements in the pyrometer’s operation conditions, which take into account the compensation of emissivity change from the surface of the wafer.

Effects of Cp2Mg molar flow rate on structural, optical, and electrical properties of semipolar Mg-doped p-AlGaN epi-layers

The semipolar (11 2‾ 2) plane Mg-doped p-Al0.42Ga0.58N epi-layers were successfully deposited on (10 1‾ 0) m-plane sapphire substrates with metal organic chemical vapor deposition technology. The effects of Cp2Mg molar flow rate on the structural, optical, and electrical properties of p-Al0.42Ga0.58N epitaxial layer were extensively studied. The randomly distributed Mg atoms and/or clusters that partially covered the growth surface were verified to act as an island-like mask to block the propagation of dislocations along the growth direction, resulting in a significant improvement in the crystalline quality of the semipolar Mg-doped p-AlGaN epi-layers. Moreover, two emission peaks with novel behavior were observed in the photoluminescence spectrum and identified to be originated from the transition between the conduction band and the Mg-related shallow acceptor energy level, and the deep Mg-induced compensation donor and the Mg acceptor pair-related transition, respectively. In addition, a hole concentration as high as 1.03 × 1017 cm−3 and a resistivity as low as 12.8 Ω cm were achieved for the semipolar Mg-doped p-Al0.42Ga0.58N epi-layer grown with the optimized Cp2Mg molar flow rate in this study.

Multi-color emission based on InGaN/GaN micro-truncated pyramid arrays

3D micro-nano devices are expected to become the mainstay of multi-color solid-state lighting in the future because of their broad-band characteristic and the advantage of integrating the monolithic light-emitting diode on a single chip. In this work, InGaN/GaN micro-truncated pyramid arrays with six equivalent (101̄1) semi-polar facets and one (0001) polar facet were successfully prepared by the metal-organic chemical vapor deposition technology. The average diameter of the obtained uniform micro-truncated pyramids was 6.8 µm with a height of 2.4 µm. According to the results of micro-photoluminescence performed, the InGaN/GaN micro-truncated pyramid arrays can achieve multi-color emission from blue to red. The luminescent positions corresponding to different wavelengths were detected by the cathode luminescence spectrum. The multi-color emission was related to the quantum hybrid structures apart from the discrepancy of In composition in different positions. The developed microstructure can create multi-color emission by combining distinct luminescence modes, which can aid in the design of future optoelectronic devices.

Bias voltage-induced structural change in PECVD-deposited diamond-like carbon coatings for optimizing the tribological performance

To improve the adhesion strength and enhance the wear resistance of diamond-like carbon (DLC) coatings, different negative bias voltages were utilized to deposit a-Si:C:H/H-DLC/DLC composite coatings on the 45 steel substrates using direct current plasma enhanced chemical vapor deposition technology. Influences of negative bias voltages on the surface morphology, microstructure, mechanical properties, and tribological performance were investigated. The results showed that as the bias voltages increased from −400 V to −600 V, the surface roughness and thickness of the coatings increased, reaching a maximum roughness of 0.426 μm and a maximum total thickness of 9.9 μm. Raman data illustrated the decrease of hydrogen contents and the increase in sp3 bonds content, matching well with the increasing hardness and elastic modulus. The residual stress tended to increase as the bias voltages, while the adhesion strength reached the maximum value of 62.45 ± 2.65 N at −550 V. Under the synergistic effects of surface roughness, interfacial adhesion strength, hardness and elastic modulus, the average friction coefficient and wear rate of the coatings initially decreased and then increased, reaching the best tribological performance at −550 V.

Localized corrosion of nitrogen-doped diamond-like carbon films on the surface of 304 stainless steel

Nitrogen-doped diamond-like carbon (N-DLC) films with different nitrogen content were prepared on the surface of 304 stainless steel (SS) using plasma-enhanced chemical vapour deposition technology. Localized failure mechanisms of the N-DLC films under long-term exposure to sodium chloride solutions have been investigated. The results demonstrated that nitrogen doping significantly affected the failure behavior of the N-DLC films. When undoped, the number of pore defects in the film is high, providing a channel for the corrosive medium to attack the substrate metal. Meanwhile, due to the high internal stress within the undoped film, extensive exfoliation of the film occurred under the effect of the growth of oxides at the film-substrate interface. The DLC film on 304 SS is subject to stress corrosion cracking failure during long-term service in sodium chloride solution. However, when nitrogen doping is 10 sccm, the pH of the micro-zone solution was highly variable due to the dissolution of nitrogen in the film and the processes of formation and hydrolysis of NH4+. A large number of residual metal cations dissolved from the substrate combine with oxygen at the corrosion pits mouth to form oxides. This can aggravate the occlusion effect of the pits and severe pitting corrosion of 304 SS occurs under autocatalytic effects. The N-DLC film with 5 sccm nitrogen addition showed the excellent durability properties. The evolution mechanism of oxidation and dissolution behaviors in the presence of variations in local hydrochemistry is also discussed.

In-situ synthesis of high-quality porous Co-NC@MoS2 composites

MOF-derived nanoporous carbon materials and TMDCs are promising candidates for catalytical applications in many fields, such as photovoltaic devices and lithium-sulfur batteries. Traditional TMDCs catalysts suffer from low conductivity and poor catalytic activity, making it difficult to meet industrial applications. Here, Co-NC@MoS2 composite materials were successfully prepared by chemical vapor deposition technology, which exhibit the high electrocatalytic activity, good charge transport ability, multiple internal channels and excellent electrical conductivity due to the dual advantages of two materials. The composite is expected to be applied in energy catalysis fields such as quantum dot sensitized solar cells.