One-step Chemical Vapor Deposition Method Research Articles

Visible light photocatalytic properties of one-step SnO2-templated grown SnO2/SnS2 heterostructure and SnS2 nanoflakes

The nanoflakes of SnS2/SnO2 heterostructure and SnS2 were synthesized by a one-step SnO2-templated chemical vapor deposition method. The metal oxide-assisted growth mechanism of SnS2/SnO2 heterostructure and SnS2 nanoflakes were realized through investigating serial microstructures of products with varied growth time. Furthermore, the photocatalytic activity for MB dyes degradation of varied growth time products was used to explore the effect of product microstructure under the visible light irradiation. The SnO2/SnS2 heterostructure and the oxide vacancies of nanoflakes demonstrated an improved visible light photocatalytic performance for MB degradation, which was around twice of the pure SnS2 nanoflakes and better than P25. The results of different scavengers on the degradation efficiency for MB indicate the·O2 −, and ·OH are the main active species in the photodegradation reaction. The one-step growth mechanism of SnS2/SnO2 could prove a facile process to grow metal oxide-metal sulfide heterostructure.

Revealing the many-body interactions and valley-polarization behavior in Re-doped MoS2 monolayers

Substitutional doping has proved to be one of the most important approaches to tune and improve the opto-electronic performance of traditional semiconductors. Similarly, controllable substitution of cations in two-dimensional layered materials can effectively modify and manipulate the band structures, which help to explore sciences and broaden the related applications. In this paper, the salt-assisted one-step chemical vapor deposition method was used to achieve Re substitution in MoS2 monolayers. High-resolution scanning transmission electron microscopy confirms the substitution of Re atoms in Mo sites. X-ray photoelectron spectroscopy and micro-photoluminescence (PL) characterization studies suggest that the Re substitution introduces typical n-type doping in MoS2 monolayers, resulting in the distinct many-body interactions in the doped sample with a higher trion ratio than in the pristine sample in the wide temperature window. The result is further confirmed by the shorter recombination lifetime observed in the Re-doped sample acquired by time-resolved PL measurements. More intriguingly, the circularly polarized PL characterization studies demonstrate that Re doping can improve the valley polarization of the MoS2 monolayer. Our work provides a deep understanding of the optical properties and the associated many-body interactions in the Re-doped MoS2 system and offers a potential way to enhance the valley polarization for spin-/valley-photonic applications.

One-step in-situ fabrication of carbon nanotube/stainless steel mesh membrane with excellent anti-fouling properties for effective gravity-driven filtration of oil-in-water emulsions

The occurrence of membrane fouling has resulted in limited wastewater treatment applications. The development of superhydrophilic-underwater superoleophobic materials has received significant attention owing to their good anti-fouling properties. However, to fabricate such materials need costly regents and tedious steps. Thus, developing a one-step process to prepare a low-cost material for oil/water separation is still desired. In this study, bio-inspired from an arachnid, inorganic carbon nanotube stainless steel meshes (CNT@SSMs) having superhydrophilic-underwater superoleophobic and excellent anti-fouling properties and a unique fiber structure were fabricated via a one-step thermal chemical vapor deposition method. The CNT@SSMs had a small pore size enabling a high water flux of 10,639 L m−2h−1 and the separation of oily wastewater, including various emulsions, at a high rejection ratio of >98.89%. As a result of its excellent chemical stability under high temperatures, a broad pH range, and saline environments, the CNT@SSM has the potential to be used in extreme conditions. In summary, these CNT@SSMs are easy to fabricate and are low-cost as a result of inexpensive reagents involved. Moreover, these novel superwetting membranes are promising candidates for treatment of hazardous oily wastewater.

SnO2/ZnSnO3 double-shelled hollow microspheres based high-performance acetone gas sensor

In this study, the preparation process and the sensing performance toward acetone of SnO2/ZnSnO3 composite microspheres with the double-shelled hollow structure were reported. It was synthesized by one-step chemical vapor deposition (CVD) method using sucrose as solid precursor pyrolysis carbon template. In addition, the internal structure of the composite microspheres can be effectively controlled by changing the sucrose concentration. The perfect double-shelled hollow structure (average diameter of about 500 nm) of the prepared sensitive materials was observed through SEM and TEM. It is noteworthy that the double-shelled hollow structure had a large specific surface area (188.60 m2/g), which can both increase the internal and external reactive sites of the sensitive material effectively. Compared with other obtained composite microspheres, the SnO2/ZnSnO3 sample with double-shelled hollow structure presented the best sensing performance, and the response to 100 ppm acetone reached 30 at 290 °C. Furthermore, it also presented excellent selectivity and long-term stability to acetone. The excellent performance was attributed to the synergistic effect of the double-shelled hollow structure with large specific surface area and the n-n heterojunction at the interface of the SnO2/ZnSnO3 composite. The sensing mechanisms of the double-shelled hollow SnO2/ZnSnO3 composite material were discussed in detail.

Fabrication of Flexible Resistive Switching Devices Based on Lead‐Free All‐Inorganic CsSnBr3 Perovskite Using a One‐Step Chemical Vapor Deposition Method

AbstractResistive switching (RS) devices have evolved as one of the most promising candidates in the memory filed due to their excellent endurance and retention, fast switching speed, and extra‐high storage density capability. However, the coexistence of toxic lead cations and low RS performance have largely limited the application of halide perovskite in nonvolatile memory filed. Herein, the lead‐free all‐inorganic perovskite CsSnBr3 films are synthesized on flexible polyimide (PI) substrates through a one‐step chemical vapor deposition (CVD) method to construct environmentally friendly RS devices. The RS devices with Pt/CsSnBr3/Pt/PI structure exhibit reliable and reproducible bipolar RS characteristics with an ultralow set/reset voltage (≈0.2/−0.15 V) and a high on/off ratio (≈105). Additionally, the RS devices are further tested by robust current–voltage curves under consecutive flexing cycles, exhibiting high mechanical bendability and electrical reliability. This work demonstrates that lead‐free all‐inorganic perovskite CsSnBr3 film is a good candidate as switching media for applications in the next‐generation environmentally friendly RS devices and opens an avenue for future flexible electronics.

Lateral Monolayer MoSe2 -WSe2 p-n Heterojunctions with Giant Built-In Potentials.

2D transition metal dichalcogenides (TMDs) have exhibited strong application potentials in new emerging electronics because of their atomic thin structure and excellent flexibility, which is out of field of tradition silicon technology. Similar to 3D p-n junctions, 2D p-n heterojunctions by laterally connecting TMDs with different majority charge carriers (electrons and holes), provide ideal platform for current rectifiers, light-emitting diodes, diode lasers and photovoltaic devices. Here, growth and electrical studies of atomic thin high-quality p-n heterojunctions between molybdenum diselenide (MoSe2 ) and tungsten diselenide (WSe2 ) by one-step chemical vapor deposition method are reported. These p-n heterojunctions exhibit high built-in potential (≈0.7 eV), resulting in large current rectification ratio without any gate control for diodes, and fast response time (≈6 ms) for self-powered photodetectors. The simple one-step growth and electrical studies of monolayer lateral heterojunctions open up the possibility to use TMD heterojunctions for functional devices.

Boosted photoelectrochemical performance of In2O3 nanowires via modulating oxygen vacancies on crystal facets

Introducing oxygen vacancies into faceted metal oxide nanostructures will largely boost photoelectrochemical water splitting ability, but currently remains a huge challenge. Herein, a simple one-step chemical vapor deposition method is developed to effectively introduce oxygen vacancies into In2O3 nanowires with the active {001} facets exposed. Theoretical calculations reveal that the introduction of oxygen vacancies produces a new defect level as shallow donor and increases the states of density, thereby enhancing the visible light absorption and promoting the separation and transportation of photogenerated carrier of faceted In2O3 nanowires. The In2O3 nanowires grown at optimal condition yield the maximal photocurrent density of 1 mA/cm2 at 0.22 V versus Ag/AgCl with unity Faradic efficiency. The results demonstrate that introducing oxygen vacancies into faceted photoelectrodes is feasible for further promoting the photoelectrochemical performance. Moreover, the methodology can be extended to other practical optoelectronic devices such as solar cell and photodetectors.

Sp3-Defect and pore engineered carbon framework for high energy density supercapacitors

Carbon based supercapacitor suffers from low energy density due to inefficient electrical double-layer storage mechanism. Herein, sp3-defect engineered sp2 carbon framework with hierarchical porous architecture (HCF) is developed via a one-step chemical vapor deposition (CVD) method for high energy density supercapacitor. Theoretical calculations are performed firstly and results reveal that the sp3-defects in host sp2 carbon sheets promote the sodium-ion storage performance attributed to the reduced energy barrier of sodium-ion adsorption and increased density of states around Fermi level. The HCF is extensively characterized and the results show that the density of sp3-defects and hierarchical micro-meso-macropore size of HCF can be well tuned by regulating the CVD temperature. Owing to reasonably engineered sp3-defects (~32.8 at%), well-defined multiscale pore architectures and wide interlayer in HCF, extra pseudocapacitive sodium-ion storage sites are obtained and therefore a capacitance up to 558.8 F/g is achieved. The resultant HCF based symmetric supercapacitor device gives a high energy density of 38.76 Wh/kg at a power density of 375.04 W/kg and still retains 30.00 Wh/kg at a high power density of 5970.15 W/kg. This work provides a facile strategy to explore the intrinsic defect in carbon electrode materials for high performance energy storage systems.

Large-scale Synthesis of Carbon Fiber Sponges by Chemical Vapor Deposition

Macroscopic carbon fiber (CF) sponges were synthesized using a one-step chemical vapor deposition (CVD) method at 230 °C. The CF sponges can grow large in a single run and the yield reaches up to 2...

Interfacial improvement of carbon fiber/epoxy composites using one-step method for grafting carbon nanotubes on the fibers at ultra-low temperatures

This paper focuses on improving the out-of-plane properties of carbon fiber/epoxy composites to extend their applications. Carbon nanotubes (CNTs) were introduced on carbon fiber surface by a novel one-step chemical vapor deposition (CVD) method at ultra-low temperature and hybrid composites were fabricated by molding technology. Mechanical and dielectric tests were conducted to figure out the changes in out-of-plane properties after grafting CNTs. The results of single-fiber tensile strength indicated that both the strength and the Weibull modulus of the CNTs-coated carbon fiber increased due to the less damage caused to the fiber by catalysts at low temperature and the repairing effect of the CNTs. Compared with the properties of desized fiber based composites, both interfacial shear strength (IFSS) and interlaminar shear strength (ILSS) of CNTs-coated fiber/epoxy composites increased by 30.73% and 32.29%, respectively, as well as the dielectric properties were also improved. The fracture mechanisms of CNTs were investigated based on the morphology observation on the interface. The improved out-of-plane properties were associated with the improved stress transfer between the carbon fibers and surrounding matrix through the newly formed interphase induced by CNT layer.

Mesoporous Single-Atom-Doped Graphene–Carbon Nanotube Hybrid: Synthesis and Tunable Electrocatalytic Activity for Oxygen Evolution and Reduction Reactions

Mesoporous heteroatom-doped carbon-based nanomaterials are very promising as catalysts for electrochemical energy conversion and storage. We have developed a one-step catalytic chemical vapor deposition method to grow a highly graphitized graphene nanoflake (GF)–carbon nanotube (CNT) hybrid material doped simultaneously with single atoms of N, Co, and Mo (N–Co–Mo–GF/CNT). This high-surface-area material has a mesoporous structure, which facilitates oxygen mass transfer within the catalyst film, and exhibits a high electrocatalytic activity and stability in oxygen reduction and evolution reactions (ORR and OER) in alkaline media. We have shown that in this metal (M)–N–C catalyst, M (Co, Mo)–C centers are the main sites responsible for OER, while, for ORR, both M and N–C centers synergistically serve as the active sites. We systematically investigated tuning of the ORR and OER activity of the porous catalyst depending on the choice of the underlying substrate. The ORR kinetic current and OER activity for N–Co–Mo–GF/CNT were significantly enhanced when the catalyst was deposited onto a Ni substrate, resulting in an advanced electrocatalytic performance compared to the best bifunctional ORR/OER catalysts reported so far. Using a developed scanning electrochemical microscopy analysis method, we demonstrated that the higher OER reactivity on Ni was attributable to the formation of underlying catalyst/Ni interfacial sites, which are accessible due to the porous, electrolyte-permeable structure of the catalyst.

Photodetection application of one-step synthesized wafer-scale monolayer MoS2 by chemical vapor deposition

Monolayer MoS2 is a known candidate to replace silicon-based materials for photodetection purposes. Achieving industrial production and application of MoS2 calls for efficient and economic synthesis of such material. Here, we report a one-step and low-cost chemical vapor deposition method for the controlled synthesis of high quality and uniform wafer-scale (approximately 9.5 × 4.5 cm) monolayer MoS2 film on SiO2/Si substrates. Using the as-synthesized MoS2 films, MoS2/PbS quantum dot hybrid device arrays are also fabricated. These hybrid devices have broad spectral photoresponse (457–1064 nm), rapid response rate, high responsivity of approximately 1.8 × 104 A W−1, and ultrahigh detectivity of approximately 7.6 × 1013 Jones, which outperforms other pristine two-dimensional as well as commercial Si and InGaAs materials. This low-cost and efficient method of growing wafer-scale monolayer MoS2, as well as the excellent performance of its hybrid device arrays, will strongly support the production and application of monolayer MoS2 in the future.

Effects of composition and temperature on the exciton emission behaviors of Mo(SxSe1−x)2 monolayer: experiment and theory

Exploring the excitonic behavior of two-dimensional (2D) alloys is of great significance, which not only could promote the understanding of fundamental photophysics in optoelectric devices, but could also guide the functional improvement of future applications. Here, we demonstrate the controllable synthesis of monolayer Mo(SxSe1−x)2 nanosheets using a one-step chemical vapor deposition method and systematical investigation on the exciton emission characteristics based on the temperature-dependent photoluminescence spectroscopy (PL) experiments. As a result, the tunable bandgap of Mo(SxSe1−x)2 alloys between 1.52 and 1.85 eV can be achieved, which is consistent with the theoretical results calculated by the ab initio density function theory. Besides, both the exciton and trion behaviors in Mo(SxSe1−x)2 are observed from the PL spectra at T = 80 K. More intriguingly, the differences between the emission energy of exciton and trion (ΔE), known as the dissociation energy of the trion, are positively correlated to the concentrations of the sulfur (S) elements, which is also proved by the theoretical calculation. Combining the experimental and theoretical results, the phenomena can be explained by the reduced dielectric screening effect and the increasing Fermi energy (EF) along with the increasing of sulfur in Mo(SxSe1−x)2 nanosheets, jointly leading to the increase of ΔE. Furthermore, the evolutions of ΔE in Mo(SxSe1−x)2 alloys as a function of temperature have been also discovered, which lay the foundation for the potential uses of 2D alloys in optoelectronic devices.

P-type Doping in Large-Area Monolayer MoS2 by Chemical Vapor Deposition.

Molybdenum disulfide (MoS2) with excellent properties has been widely reported in recent years. However, it is a great challenge to achieve p-type conductivity in MoS2 because of its native stubborn n-type conductivity. Substitutional transition metal doping has been proved to be an effective approach to tune their intrinsic properties and enhance device performance. Herein, we report the growth of Nb-doping large-area monolayer MoS2 by a one-step salt-assisted chemical vapor deposition method. Electrical measurements indicate that Nb doping suppresses n-type conductivity in MoS2 and shows an ambipolar transport behavior after annealing under the sulfur atmosphere, which highlights the p-type doping effect via Nb, corresponding to the density functional theory calculations with Fermi-level shifting to valence band maximum. This work provides a promising approach of two-dimensional materials in electronic and optoelectronic applications.

Few-layer MoS2 nanosheets anchored by CNT network for superior lithium storage

A novel self-assembled porous network of carbon nanotubes (CNTs) attached to molybdenum disulfide (MoS2) nanosheets is prepared via a one-step atmospheric pressure chemical vapor deposition (APCVD) method. The conventional APCVD method cannot be used to uniformly deposit three-dimensional (3D) structures. Instead, an alternative method is used to overcome the disadvantage of conventional APCVD, whereby molybdenum oxide (MoO3) is decomposed by a molybdate ion (MoO42−) using in situ sulfuration. The synergy between the highly conductive CNT network and the layered MoS2 nanosheets contributes to the formation of high-efficiency ion/electron channels and improves the electrode durability and stability. The as-prepared C-MoS2/CNT composite exhibits both high rate stability and long-term capacity in lithium-ion batteries (LIBs). The C-MoS2/CNT electrode has a much higher initial discharge capacity of 1430 mAh g−1 at 100 mA g−1 and an impressive rate capability (885 mAh g−1 at 4000 mA g−1). Moreover, the C-MoS2/CNT composite also exhibits a long cycle life of 1260 mAh g−1 after 200 cycles at 500 mA g−1 and 1066 mAh g−1 at 1000 mA g−1 after 250 cycles. The mechanism and design strategy presented in this work may provide ideas for the development of other electrode materials.

One-step growth of wafer-scale monolayer tungsten disulfide via hydrogen sulfide assisted chemical vapor deposition

Wafer-scale monolayer WS2 has been widely investigated. Here, we report a repeatable and low-cost one-step chemical vapor deposition method for the direct growth of a 4-in. monolayer WS2 film on a thermal oxide silicon wafer by using WO3 and H2S gas as precursors. H2S gas exhibits a high vulcanization ability and can effectively reduce the growth temperature of WS2 to 825 °C. The growth process follows a self-limiting growth to form a monolayer polycrystalline film, which is merged via many stable small-angle grain boundaries. The wafer-scale monolayer WS2 film shows uniform and high-quality electrical properties. This method helps promote the future production and application of wafer-scale monolayer sulfide.

One-Step CVD Synthesis of Few-Layer SnS2/MoS2 Vertical Heterostructures

Constructing van der Waals (vdW) heterostructures with various-layered two-dimensional (2D) materials is attractive to design various materials and devices. For controllable fabrication of vdW heterostructures, it is very important to make the growth process clear. In this work, SnS2/MoS2 vertical heterostructures were synthesized by the one-step chemical vapor deposition (CVD) method. The bottom MoS2 triangle layers can be partially or completely covered by SnS2 layers. The interlayer charge separation was also observed in the heterostructures by photoluminescence (PL) spectroscopy. The growth mechanism of SnS2/MoS2 vertical heterostructures was also discussed for the first time. MoS2 triangle layers form on the substrates at first and then grow a top layer of SnS2. This study will provide an important and practical method, as a guidance to prepare high-quality vertical heterostructures.

Strategic extended air stability of organolead halide perovskite nonvolatile memory devices

In this study, we demonstrated long-term stability in the resistive switching (RS) properties of MAPbI3 films, coated via a one-step chemical vapor deposition (CVD) method using no additives or polymers. The RS behavior of the CVD-fabricated memory devices compares favorably to that of spin-coated films; these devices exhibited reliably stable bipolar resistive switching properties for 30 days under ambient conditions, while spin-coated devices were stable for only 10 days. For further enhancement of air stability, a 20 nm-thick ZnO passivation layer was deposited on MAPbI3via on-axis and facing-target sputtered (FTS) techniques. The resistive random-access memory (ReRAM) devices with a ZnO passivation layer deposited via FTS technique exhibited extended air stability for 3 months under ambient conditions, whereas in the case of memory devices fabricated with an on-axis sputtered passivation layer, air stability was limited to 60 days. This extended air stability can be attributed to excellent step coverage and free of plasma damage during deposition. Memory devices fabricated via the CVD and FTS methods showed no significant variations at either set or reset levels of voltage and showed favorable levels in terms of both data retention and endurance performance with storage time.

An experimental and computational study of enhanced charge storage capacity of chemical vapor deposited Ni3S2-reduced graphene oxide hybrids

In the present approach, we have successfully synthesized wormlike Ni3S2 and Ni3S2-RGO hybrids on nickel (Ni) foam by a facile and highly reproducible one-step chemical vapor deposition (CVD) method. We have demonstrated that Ni3S2 and Ni3S2-RGO hybrids can be grown directly on the current collector of energy storage devices without using any binder, which may lead to serve industry for large-scale production of the material. We have studied the pseudocapacitive energy storage performance of the CVD grown Ni3S2 and its hybrids with variable concentration of RGO. The Ni3S2-RGO hybrid with 0.5 mg GO showed a maximum areal specific capacitance of 1.4 F·cm−2 at a current density of 1 mA·cm−2 (approximately 1124 Fg−1 at a current density of 1 Ag−1). The enhanced supercapacitive performance of Ni3S2-RGO predominantly due to its high surface area and high conductivity as compared to bare Ni3S2. The electrochemical impedance spectroscopic analysis revealed Ni3S2-RGO possess enhanced charge-transfer characteristics as compared to bare Ni3S2. Furthermore, Density Functional Theory (DFT) simulations infer the strong hybridization between C p orbital and Ni d orbital lead to enhanced electrochemical property and Density of States (DOS) is crucially responsible for the improved charge storage performance of Ni3S2-RGO hybrids.

Low temperature HFCVD synthesis of tungsten oxide thin film for high response hydrogen gas sensor application

• WO 3 thin films are obtained through low temperature HFCVD technique. • WO 3 thin films exhibits cauliflower morphology (WCNs) with typical monoclinic WO 3 crystal structure. • Highly uniform WCNs thin film is prepared. • High sensitivity of ∼87% towards H 2 gas is achieved. A quick and efficient approach was employed for the growth of nanocrystalline tungsten oxide (WO 3 ) thin films using one-step hot filament chemical vapor deposition (HFCVD) method at low temperature. In a typical experiment, the parent material tungsten (W) was subjected to oxidation, gasification and its subsequent condensation to obtain the uniform deposition of WO 3 thin film on silicon substrate at significantly low temperature of ∼200 °C. Prepared WO 3 thin film possessed the cauliflower nanostructure (WCNs) with typical monoclinic WO 3 crystal structure. Prepared WCNs thin films were applied for the detection of hydrogen (H 2 ) gas at 100 ppm. H 2 response increased with rise in temperature and the maximum response of ∼87% was obtained at the optimized temperature of ∼250 °C with response time 180 s.