Chemical Vapor Deposition Method Research Articles

Depressed-cladding thulium-doped fiber for applications below 1800 nm

We present a thulium-doped silica fiber, featuring a depressed cladding, for applications at wavelengths below 1800 nm. The depressed cladding is used as a distributed filter suppressing amplified spontaneous emission at longer wavelengths, which helps promote emission at shorter wavelengths. We describe the fiber design process that was carried out by using a combination of numerical methods. The fiber was prepared in-house by a combination of the standard modified chemical vapor deposition method and nanoparticle doping. We demonstrate the effectiveness and tunability of ASE filtering, which is influenced by fiber bend radius and its variation.

Advancement in Carbon Nanoparticle Synthesis and Their Application: A Comprehensive Review

The global population gradually increase at an alarming state, which would increase demand for food globally. This increasing use of pesticides and fertilizers. In order to meet this demand, an overview of the numerous applications of nanotechnology for agriculture. Various nanomaterials like nanofertilizers and pesticides enhance soil fertility and crop productivity. However, excessive chemical fertilizer use as per FAO, 2017. Among these, the nanotechnology has wide range of applications in healthcare and medicines, diagnosis etc. Recently, carbon nanoparticles (CNPs) play a significant role in various fields. Carbon nanoparticles (CNPs) represent innovative nanostructures. These can be synthesized by different methods, green synthesis as well as chemical synthesis such as arch discharge method, laser ablation method, chemical vapour deposition method etc. The advancement of CNPs entails the exploration of diverse synthetic techniques and exploration of various application due to their chemical and physical properties in healthcare, agriculture (for delivery of agrochemicals) etc. These are also used in plant growth enhancement and resistance to stresses. However, challenges related to precisely defining CNP structures and ensuring property uniformity remain inadequately addressed and lack detailed study. In this review article we emphasize methodologies for the synthesis of CNPs by various chemical methods and also include their applications in therapeutics, pharmaceuticles, sensing and agriculture.

The GeSe/SnSe heterojunction photodetector with self-powered characteristics and high infrared response performance

We present a GeSe/SnSe van der Waals heterojunction fabricated using the wet transfer technique. GeSe and SnSe were synthesized via a low-temperature and atmospheric-pressure chemical vapor deposition method. The GeSe/SnSe heterostructure photodetector demonstrates remarkable rectification characteristics, boasting a rectification ratio of 102, along with an exceptionally low dark current, indicating minimal power consumption. Furthermore, it exhibits a broad optical response, spanning from the visible spectrum (450 nm) to the near-infrared (1064 nm). Under 808 nm laser illumination and reverse bias, the device achieves a responsivity of 19.82 A/W, a detectivity of 4.74 × 109 Jones, and an external quantum efficiency of 3048.32%. Notably, the GeSe/SnSe heterojunction photodetector also exhibits self-powered characteristics, with a responsivity of 0.11 mA/W and a detectivity of 5.44 × 106 Jones at zero bias voltage, accompanied by a fast response time of 23/61 ms (rise/fall). These findings underscore the effectiveness of the GeSe/SnSe heterojunction as a strategy for near-infrared photodetectors to simultaneously achieve low power consumption, high photoresponsivity, and self-powered photodetection, which is promising for optoelectronic device applications.

Single-mode lasers based on pseudo-cubic perovskite CsPbBr3 microcrystals

The performance of perovskite lasers is often influenced by both the gain medium and the optical cavity. Therefore, a cavity with a unique structure and efficient feedback is essential for studying high performance of lasers. We successfully synthesized smooth-surface pseudo-cubic CsPbBr3 microcrystals on a silicon substrate by chemical vapor deposition method. The pseudo-cubic CsPbBr3 microcrystals exhibit a microcavity structure resembling a cube, where three-dimensional total internal reflection can be achieved within the microcavity. This provides a highly promising foundation for exploring high-performance lasers. The pseudo-cubic CsPbBr3 microcrystals demonstrate stimulated emission at a wavelength of 536.2 nm, achieving a full width at half maximum of 0.47 nm for a single-mode laser at room temperature. Additionally, the pseudo-cubic CsPbBr3 microcrystals exhibit remarkable stability that optical properties remain largely unchanged after long-term exposure to air. The perovskite microcavity with this novelty structure has been rarely reported in previous studies, and it also serves as an ideal cavity for lasers with broad prospects for integrated optoelectronic devices due to excellent optical properties and significant stability. This research not only deepens our understanding of unconventional CsPbBr3 microlasers but also provides strong support for future related research and technological development.

Synthesis and characterization of 1T′ and 2H phase coexistence 2D Re1-xMoxS2 alloy films and their application for photodetectors

Alloying is considered an efficient strategy to engineer the crystal structure, modulate the energy band structure and charge carrier concentration by adjusting the elemental composition of transition metal dichalcogenides (TMDs). Here, the two-dimensional (2D) Re1-xMoxS2 alloy films with tunable composition and phase structure were prepared on mica substrates by chemical vapor deposition (CVD) method. The back-gated field effect transistors (FETs) based on 2D Re1-xMoxS2 alloy films were prepared. The Mo component x in 2D Re1-xMoxS2 alloy films was varied from 0, 0.2, 0.4, 0.5, 0.6, 0.8–1 by changing mole ratio of ReO3 to MoO3 while the total number of moles remains the same. The Mo composition-dependent morphology phase structure, electrical transport properties and photoelectric properties of Re1-xMoxS2 alloy films were studied in detail. The results indicate that the 1T′ phase Mo-doped ReS2 and 2H phase Re-doped MoS2 coexist, and the ratio of 2H phase Re-doped MoS2 to 1T′ phase Mo-doped ReS2 can be modulated by changing Mo component x in Re1-xMoxS2 alloy films. 1T′ phase Mo-doped ReS2 exhibits the p-type conduction feature while 2H phase Re-doped MoS2 shows the n-type conduction behavior. The Re1–xMoxS2 alloy devices show obvious photoelectric response to 405, 532, 635 and 808 nm lasers irradiation. The Re0.5Mo0.5S2 (x= 0.5) has the maximum responsivity R of 1024.1 mA/W and external quantum efficiency EQE of 239.3% under 532 nm laser irradiation.

Microstructure regulation and enhanced VOC removal performance of carbon aerogels by surface carbon nanotube grown

Carbon aerogels were newly employed in adsorption for volatile organic compounds (VOCs) as an emerging material. In contrast, the microstructure and high carbon consumption are the primary factors restricting their application scenarios. Carbon nanotubes, recognized for their controllable cylindrical hollow structure and hydrophobic walls, generally possess higher adsorption capacities than typical carbon adsorbents. In this study, carbon nanotubes were grown on the surface of carbon aerogels using the chemical vapor deposition method by controlling different deposition conditions. The results showed that the modified samples displayed the maximum adsorption capacity of 145.0 mg/g and 178.3 mg/g for toluene and 1,2- dichlorobenzene, respectively. After ten regeneration cycles, the performance decreased by 7.9 % and 5.6 %, respectively. Meanwhile, the carbon replenishment was about 0.2 g/g, which is an excellent complement for carbon consumption. Various characterization patterns showed that deposition temperature was reflected in its deposition rate, deposition times influenced the formation of multi-walled carbon nanotubes, and deposition concentration affected the length of carbon nanotubes. This study offers valuable insight into the growth patterns of carbon nanotubes and the microscale regulation of carbon material surfaces, and this method is expected to be an effective means of carbon replenishment, carbon addition to carbon-poor materials, and enhancement of VOCs removal performance, and the growth mechanisms investigated are instructive for practical applications.

Rational design of diamond through microstructure engineering: From synthesis to applications

AbstractDiamond possesses excellent thermal conductivity and tunable bandgap. Currently, the high‐pressure, high‐temperature, and chemical vapor deposition methods are the most promising strategies for the commercial‐scale production of synthetic diamond. Although diamond has been extensively employed in jewelry and cutting/grinding tasks, the realization of its high‐end applications through microstructure engineering has long been sought. Herein, we discuss the microstructures encountered in diamond and further concentrate on cutting‐edge investigations utilizing electron microscopy techniques to illuminate the transition mechanism between graphite and diamond during the synthesis and device constructions. The impacts of distinct microstructures on the electrical applications of diamond, especially the photoelectrical, electrical, and thermal properties, are elaborated. The recently reported elastic and plastic deformations revealed through in situ microscopy techniques are also summarized. Finally, the limitations, perspectives, and corresponding solutions are proposed.

Integrating Lithium Sulfide as a Single Ionic Conductor Interphase for Stable All-Solid-State Lithium-Sulfur Batteries.

As a very prospective solid-state electrolyte, Li10GeP2S12 (LGPS) exhibits high ionic conductivity comparable to liquid electrolytes. However, severe self-decomposition and Li dendrite propagation of LGPS will be triggered due to the thermodynamic incompatibility with Li metal anode. Herein, by adopting a facile chemical vapor deposition method, an artificial solid electrolyte interphase composed of Li2S is proposed as a single ionic conductor to promote the interface stability of LGPS toward Li. The good electronic insulation coupled with ionic conduction property of Li2S effectively blocks electron transfer from Li to LGPS while enabling smooth passage of Li ions. Meanwhile, the generated Li2S layer remains good interface compatibility with LGPS, which is verified by the stable Li-plating/stripping operation for over 500h at 0.15mAcm-2. Consequently, the all-solid-state Li-S batteries (ASSLSBs) with a Li2S layer demonstrate superb capacity retention of 90.8% at 0.2mAcm-2 after 100cycles. Even at the harsh condition of 90 °C, the cell can deliver a high reversible capacity of 1318.8mAhg-1 with decent capacity retention of 88.6% after 100cycles. This approach offers a new insight for interface modification between LGPS and Li and the realization of ASSLSBs with stable cycle life.

Lithium Ion Intercalation-Induced Metal-Insulator Transition in Inclined-Standing Grown 2D Non-Layered Cr2S3 Nanosheets.

Gate-controlled ionic intercalation in the van der Waals gap of 2D layered materials can induce novel phases and unlock new properties. However, this strategy is often unsuitable for densely packed 2D non-layered materials. The non-layered rhombohedral Cr2S3 is an intrinsic heterodimensional superlattice with alternating layers of 2D CrS2 and 0D Cr1/3. Here an innovative chemical vapor deposition method is reported, utilizing strategically modified metal precursors to initiate entirely new seed layers, yields ultrathin inclined-standing grown 2D Cr2S3 nanosheets with edge instead of face contact with substrate surfaces, enabling rapid all-dry transfer to other substrates while ensuring high crystal quality. The unconventional ordered vacancy channels within the 0D Cr1/3 layers, as revealed by cross-sectional scanning transmission electron microscope, permitting the insertion of Li+ ions. An unprecedented metal-insulator transition, with a resistance modulation of up to six orders of magnitude at 300 K, is observed in Cr2S3-based ionic field-effect transistors. Theoretical calculations corroborate the metallization induced by Li-ion intercalation. This work sheds light on the understanding of growth mechanism, structure-property correlation and highlights the diverse potential applications of 2D non-layered Cr2S3 superlattice.

Axially Modified Square-Pyramidal CoN4-F1 Sites Enabling High-Performance Zn-Air Batteries.

Cobalt-nitrogen-carbon (Co-N-C) catalysts with a CoN4 structure exhibit great potential for oxygen reduction reaction (ORR), but the imperfect adsorption energy toward oxygen species greatly limits their reduction efficiency and practical application potential. Here, F-coordinated Co-N-C catalysts with square-pyramidal CoN4-F1 configuration are successfully synthesized using F atoms to regulate the axial coordination of Co centers via hydrothermal and chemical vapor deposition methods. During the synthesis process, the geometry structure of the Co atom converts from six-coordinated Co-F6 to square-pyramidal CoN4-F1 in the coordinatively unsaturated state, which provides an open binding site for the O2. The introduction of axial F atoms into the CoN4 plane alters the local atomic environment around Co, significantly improving the ORR activity and Zn-air batteries performance. In situ spectroscopy proves that CoN4-F1 sites strongly combine with the OOH* intermediate and facilitate the splitting of O-O bond, making OOH* readily decompose into O* and OH* via a dissociative pathway. Theoretical calculations confirm that the axial F atom effectively reduces the electronic density of the Co centers and facilitates the desorption of the OH* intermediate, efficiently accelerating the overall ORR kinetics. This work advances a feasible synthesis mechanism of axial ligands and provides a route to construct efficient high-coordination catalysts.

Band Gap Engineering of MoxW1-xS2 Alloy Monolayers with Wafer-Scale Uniformity.

Modulating the band gap of two-dimensional (2D) transition metal dichalcogenide (TMDC) semiconductors is critical for their application in a wider spectral range. Alloying has been demonstrated as an effective method for regulating the band gap of 2D TMDC semiconductors. The fabrication of large-area 2D TMDC alloy films with centimeter-scale uniformity is fundamental to the application of integrated devices. Herein, we report a liquid-phase precursor one-step chemical vapor deposition (CVD) method for fabricating a MoxW1-xS2 alloy monolayer with a large size and an adjustable band gap. Good crystalline quality and high uniformity on a wafer scale enable the continuous adjustment of its band gap in the range of 1.8-2.0 eV. Density functional theory calculations provided a deep understanding of the Raman-active vibration modes of the MoxW1-xS2 alloy monolayer and the change in the conductivity of the alloy with photon energy. The synthesis of large-area MoxW1-xS2 alloy monolayers is a critical step toward the application of 2D layered semiconductors in practical optoelectronic devices.

Lead-free CsCu2I3 thin films prepared by one-step chemical vapor deposition method for ultraviolet photodetector

Lead-free CsCu2I3 thin films prepared by one-step chemical vapor deposition method for ultraviolet photodetector

Upcycling prawn shells: Chitosan–carbon nanotube nanocomposites with boosted magnetic and electrical properties

AbstractMulti‐walled carbon nanotubes (MWCNTs) were successfully synthesized and functionalized by chemical vapour deposition and acid reflux methods, respectively. Chitosan (CTS) was prepared by a chemical extraction method from waste prawn shells. Various weight fractions of functionalized multi‐walled carbon nanotubes (f‐MWCNTs) have been used as reinforcing agent in CTS biopolymer matrix. Fourier transform infrared spectroscopy analysis was done, which confirms the presence of absorption bands of the various functional groups of chitin, CTS, and MWCNTs. Raman spectra revealed the quality of MWCNTs, the extent of their functionalization, and the quality of nanocomposites. The X‐ray diffraction analysis showed the distinctive peaks for f‐MWCNTs’ and also revealed the formation of CTS/f‐MWCNTs nanocomposites. Transmission Electron Microscopy (TEM) analysis also exhibited that the CTS/f‐MWCNTs nanoparticles have a well‐defined crystalline structure. The highest coercivity and magnetization (Ms) of the CTS/5%f‐MWCNTs nanocomposite are 602 Oe and 0.1202 emu/g, respectively that have been enhanced by 3.83 and 5.27 times compared to the pure CTS respectively. It showed that the conductivity is getting higher with the addition of f‐MWCNTs in the CTS matrix. CTS/5% f‐MWCNTs composites exhibit the highest conductivity than other composites and the conductivity of CTS/5% f‐MWCNTs composite is 4.0×10−4 S/m.

Hydrophobic Silk Fibroin-Agarose Composite Aerogel Fibers with Elasticity for Thermal Insulation Applications.

Aerogel fibers, characterized by their ultra-low density and ultra-low thermal conductivity, are an ideal candidate for personal thermal management as they hold the potential to effectively reduce the energy consumption of room heating and significantly contribute to energy conservation. However, most aerogel fibers have weak mechanical properties or require complex manufacturing processes. In this study, simple continuous silk fibroin-agarose composite aerogel fibers (SCAFs) were prepared by mixing agarose with silk fibroin through wet spinning and rapid gelation, followed by solvent replacement and supercritical carbon dioxide treatment. Among them, the rapid gelation of the SCAFs was achieved using agarose physical methods with heat-reversible gel properties, simplifying the preparation process. Hydrophobic silk fibroin-agarose composite aerogel fibers (HSCAFs) were prepared using a simple chemical vapor deposition (CVD) method. After CVD, the HSCAFs' gel skeletons were uniformly coated with a silica layer containing methyl groups, endowing them with outstanding radial elasticity. Moreover, the HSCAFs exhibited low density (≤0.153 g/cm3), a large specific surface area (≥254.0 m2/g), high porosity (91.1-94.7%), and excellent hydrophobicity (a water contact angle of 136.8°). More importantly, they showed excellent thermal insulation performance in low-temperature (-60 °C) or high-temperature (140 °C) environments. The designed HSCAFs may provide a new approach for the preparation of high-performance aerogel fibers for personal thermal management.

Facet-Dependent Interfacial Charge Transfer between T-Phase VS2 Nanoflakes and Rutile TiO2 Single Crystals.

The hybridizations of two-dimensional (2D) metallic materials with semiconducting transition metal oxides (TMOs) register attractive heterojunctions, which can find various applications in photostimulated circumstances. In this work, we developed an ambient-pressure chemical vapor deposition method to directly grow T-VS2 on atomically smooth rutile TiO2 single crystals with different terminations and thus successfully constructed a heterojunction model of VS2/TiO2 with a well-defined clean interface. Detailed measurements with Kelvin probe force microscopy revealed the facet-dependent charge transfer occurring at the VS2/TiO2 interfaces, seeing variations not only in the amount and direction of the transferred electrons but also in the photoinduced surface potential changes and the dynamics of photogenerated charge carriers under ultraviolet irradiation. Interestingly, ultrathin T-VS2 was found with considerable magnetism at room temperature, disregarding the charge exchange with the TiO2 substrates. These results may bring deep insights into the photoinspired functionalities of the hybridized system combining metallic transition metal dichalcogenides and TMO materials.

Controllable Synthesis of Transferable Ultrathin Bi2Ge(Si)O5 Dielectric Alloys with Composition-Tunable High-κ Properties.

Two-dimensional (2D) alloys hold great promise to serve as important components of 2D transistors, since their properties allow continuous regulation by varying their compositions. However, previous studies are mainly limited to the metallic/semiconducting ones as contact/channel materials, but very few are related to the insulating dielectrics. Here, we use a facile one-step chemical vapor deposition (CVD) method to synthesize ultrathin Bi2SixGe1-xO5 dielectric alloys, whose composition is tunable over the full range of x just by changing the relative ratios of the GeO2/SiO2 precursors. Moreover, their dielectric properties are highly composition-tunable, showing a record-high dielectric constant of >40 among CVD-grown 2D insulators. The vertically grown nature of Bi2GeO5 and Bi2SixGe1-xO5 enables polymer-free transfer and subsequent clean van der Waals integration as the high-κ encapsulation layer to enhance the mobility of 2D semiconductors. Besides, the MoS2 transistors using Bi2SixGe1-xO5 alloy as gate dielectrics exhibit a large Ion/Ioff (>108), ideal subthreshold swing of ∼61 mV/decade, and a small gate hysteresis (∼5 mV). Our work not only gives very few examples on controlled CVD growth of insulating dielectric alloys but also expands the family of 2D single-crystalline high-κ dielectrics.

Combination of chemical vapor deposition and thermal growth methods for facile synthesis of tin oxide-doped multiwalled carbon nanotubes

Combination of chemical vapor deposition and thermal growth methods for facile synthesis of tin oxide-doped multiwalled carbon nanotubes

Synthesis of the 2D Ternary Topological Insulator Bi2‐xSbxSe3 with a Low Carrier Concentration and Ultrahigh Carrier Mobility

AbstractHighcarrier concentration and low mobility in Bi2Se3 hide thetopological surface states (TSS). In the 2D ternary topological insulator (TI) Bi2–xSbxSe3,compensatory Sb doping regulates the carrier concentration and mobility withambipolar performance, together with the ultrathin thickness; these factorsmake the TSS in the 2D ternary TI Bi2–xSbxSe3 more observable. Here, a chemical vapor deposition (CVD) method is provided for synthesizing ultrathin Sb‐doped Bi2Se3 nanoplates with dimensions of 2–126 nm in thickness, 3–100 µm in lateral size, and an average Sb doping ranging from 0.15 ≤ x ≤ 0.75. Bi2–xSbxSe3 field effect transistors and Hall devices are manufactured to determine the carrier concentration and mobility of the obtained Bi2–xSbxSe3 nanoplates. These findings demonstrate that the 2D carrier concentration for Bi2–xSbxSe3 nanoplates can decrease up to 1.6 × 1012 cm–2. Furthermore, field‐effect mobility and Hall mobility of up to 3411 cm2 V–1s–1 and 6462 cm2 V–1 s–1, respectively, are realized. A strong ambipolar field effect is found in low‐carrier‐density Bi2–xSbxSe3 nanoplates, proving that these nanostructures may be freely controlled in terms of carrier type and concentration. The synthesis of high‐quality Bi2–xSbxSe3 nanoplates with low‐carrier concentration and high‐mobility provides a platform for investigating TI characteristics more clearly.

Trichome-Like Biomimetic Air Filters via Templated Silicone Nanofilaments.

Air pollution threats to human health have increased awareness of the role of filter units in air cleaning applications. As an ideal energy-saving strategy for air filters, the slip effect on nanofiber surfaces can potentially overcome the trade-off between filtration efficiency and pressure drop. However, the potential of the slip effect in nanofibrous structures is significantly limited by the tight nanofiber stacks. In this study, trichome-like biomimetic (TLB) air filters with 3D-templated silicone nanofilaments (average diameter: ≈74 nm) are prepared based on an in situ chemical vapor deposition (CVD) method inspired by plant purification. Theoretical modeling and experimental results indicate that TLB air filters make significant use of the slip effect to overcome the efficiency-resistance tradeoff. The selectable filter class (up to U15, ≈99.9995%) allows TLB air filters to meet various requirements, and their integral filtration performance surpasses that of most commodity air filters, including melt-blown cloth, ePTFE membranes, electrospun mats, and glass fiber paper. The proposed strategy directly transforms commercial filter media and filters into TLB air filters using a bottom-up, one-step approach. As a proof-of-concept, reusable N95 respirators and air purifiers equipped with TLB air filters are fabricated, overcoming the limitations of existing filter designs and fabrication methods.

2D WS2/WSe2(Er) Heterojunction for High Performance Photodetectors

Abstract2D transition metal dichalcogenides and their heterojunctions have demonstrated great potentialities for applications in optoelectronics, and rare‐earth doping has proven an effective way for achieving high performance. Here, 2D WS2 and Er3+ in situ doped WSe2 are prepared by the chemical vapor deposition method. Thicknesses and atomic structures of the prepared WS2 and WSe2 are characterized by atomic force microscopy and transmission electron microscope, while qualities of the membranes are characterized by photoluminescence spectroscopy and Raman spectroscopy, respectively. The 13.7 and 15.8 at% of Er3+ doping concentration in WSe2 are examined by energy dispersive spectroscopy and X‐ray photoelectron spectroscopy, respectively. Performances of photodetectors based on the WSe2 and Er3+ doped WSe2 membranes are characterized individually. A microregion fixed‐point transfer technique is used to transfer the monolayer WS2 onto the Er‐doped monolayer WSe2 to form vertical van der Waals heterojunctions. Excellent performances are measured from the monolayer WS2/WSe2(Er3+) heterojunction photodetector with a photoresponsivity (Rλ) of up to 40.5 A W−1 and external quantum efficiency (EQE) of 8793%. The results prove the effectiveness of Er3+ in situ doping in WS2/WSe2(Er) heterojunctions for high‐performance photodetectors.