Low-temperature Chemical Vapor Deposition Research Articles

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.

Plasma-enhanced chemical vapor deposition a-SiOCN:H low-Z thin films for bulk acoustic wave resonators

The 5th generation (5G) wireless telecommunication standards with newly defined frequency bands up to 6 GHz are currently established around the world. While outperforming surface acoustic wave (SAW) filters above 1 GHz, bulk acoustic wave (BAW) resonators in multiplexers for radio-frequency front-end (RFFE) modules continuously face higher performance requirements. In contrast to free-standing bulk acoustic resonators (FBARs), solidly mounted resonator (SMR) technology uses an acoustic Bragg mirror, which has already been successfully applied for several GHz applications. In this work, we investigate the potential of amorphous hydrogenated silicon-oxycarbonitride (a-SiOCN:H) thin films synthesized with low-temperature plasma-enhanced chemical vapor deposition (PECVD) as a low acoustic impedance (low-Z) material. Compared to the state-of-the-art where in Bragg mirrors up to now SiO2 is used as standard, the acoustic impedance ratio against the high-Z material tungsten (W) is enhanced for a better device performance. To limit the expected increase in viscous loss when the acoustic impedance is reduced, to a minimum, predominantly the mass density was reduced while keeping the mechanical elasticity high. By doing so, acoustic impedance values as low as 7.1 MRayl were achieved, thereby increasing the impedance ratio of high-Z to low-Z materials from 8:1 up to 14:1.

In-situ low-temperature sulfur CVD on metal sulfides with SO2 to realize self-sustained adsorption of mercury

Capturing gaseous mercury (Hg0) from sulfur dioxide (SO2)-containing flue gases remains a common yet persistently challenge. Here we introduce a low-temperature sulfur chemical vapor deposition (S-CVD) technique that effectively converts SO2, with intermittently introduced H2S, into deposited sulfur (Sd0) on metal sulfides (MS), facilitating self-sustained adsorption of Hg0. ZnS, as a representative MS model, undergoes a decrease in the coordination number of Zn–S from 3.9 to 3.5 after Sd0 deposition, accompanied by the generation of unsaturated-coordinated polysulfide species (Sn2–, named Sd*) with significantly enhanced Hg0 adsorption performance. Surprisingly, the adsorption product, HgS (ZnS@HgS), can serve as a fresh interface for the activation of Sd0 to Sd* through the S-CVD method, thereby achieving a self-sustained Hg0 adsorption capacity exceeding 300 mg g−1 without saturation limitations. Theoretical calculations substantiate the self-sustained adsorption mechanism that S8 ring on both ZnS and ZnS@HgS can be activated to chemical bond S4 chain, exhibiting a stronger Hg0 adsorption energy than pristine ones. Importantly, this S-CVD strategy is applicable to the in-situ activation of synthetic or natural MS containing chalcophile metal elements for Hg0 removal and also holds potential applications for various purposes requiring MS adsorbents.

Uniform Synthesis of Bilayer Hydrogen Substituted Graphdiyne for Flexible Piezoresistive Applications.

Graphdiyne (GDY) has garnered significant attention as a cutting-edge 2D material owing to its distinctive electronic, optoelectronic, and mechanical properties, including high mobility, direct bandgap, and remarkable flexibility. One of the key challenges hindering the implementation of this material in flexible applications is its large area and uniform synthesis. The facile growth of centimeter-scale bilayer hydrogen substituted graphdiyne (Bi-HsGDY) on germanium (Ge) substrate is achieved using a low-temperature chemical vapor deposition (CVD) method. This material's field effect transistors (FET) showcase a high carrier mobility of 52.6cm2V-1s-1 and an exceptionally low contact resistance of 10Ωµm. By transferring the as-grown Bi-HsGDY onto a flexible substrate, a long-distance piezoresistive strain sensor is demonstrated, which exhibits a remarkable gauge factor of 43.34 with a fast response time of ≈275ms. As a proof of concept, communication by means of Morse code is implemented using a Bi-HsGDY strain sensor. It is believed that these results are anticipated to open new horizons in realizing Bi-HsGDY for innovative flexible device applications.

Achieving stable Zn metal anode via a hydrophobic and Zn2+-conductive amorphous carbon interface

High security and low cost enable aqueous zinc ion batteries (AZIBs) with huge application potential in large-scale energy storage. Nevertheless, the loathsome dendrite and side reactions of Zn anode are harmful to the cycling lifespan of AZIBs. Here, a new type of thin amorphous carbon (AC) interface layer (∼100 nm in thickness) is in-situ constructed on the Zn foil (Zn@AC) via a facile low-temperature chemical vapor deposition (LTCVD) method, which owns a hydrophobic peculiarity and a high Zn2+ transference rate. Moreover, this AC coating can homogenize the surface electric field and Zn2+ flux to realize the uniform deposition of Zn. Consequently, dendrite growth and side reactions are concurrently mitigated. Symmetrical cell achieves a dendrite-free Zn plating/stripping over 500 h with a low overpotential of 31 mV at 1 mA cm−2/1 mAh cm−2. Of note, the full cell with a MnO2/CNT cathode harvests a capacity retention of 70.0 % after 550 cycles at 1 A/g. In addition, the assembled flexible quasi-solid-state AZIBs display a stable electrochemical performance under deformation conditions and maintain a capacity of 76.5 mAh/g at 5 A/g after 300 cycles. This innovative amorphous carbon layer is expected to provide a new insight into stabilizing Zn anode.

Direct Application of Carbon Nanotubes (CNTs) Grown by Chemical Vapor Deposition (CVD) for Integrated Circuits (ICs) Interconnection: Challenges and Developments.

With the continuous shrinkage of integrated circuit (IC) dimensions, traditional copper interconnect technology is gradually unable to meet the requirements for performance improvement. Carbon nanotubes have gained widespread attention and research as a potential alternative to copper, due to their excellent electrical and mechanical properties. Among various methods for producing carbon nanotubes, chemical vapor deposition (CVD) has the advantages of mild reaction conditions, low cost, and simple reaction operations, making it the most promising approach to achieve compatibility with integrated circuit manufacturing processes. Combined with through silicon via (TSV), direct application of CVD-grown carbon nanotubes in IC interconnects can be achieved. In this article, based on the above background, we focus on discussing some of the main challenges and developments in the application of CVD-grown carbon nanotubes in IC interconnects, including low-temperature CVD, metallicity enrichment, and contact resistance.

Large-scale synthesis of 3D ordered microporous carbon at low temperature using cobalt ions exchanged zeolite Y as a template

Zeolite-templated carbons (ZTCs) have a unique three-dimensional (3D) ordered microporous structure and an extra-large surface area, and have excellent properties in adsorption and energy storage. Unfortunately, the lack of efficient synthesis strategies and the difficulty of doing this on a large-scale have seriously limited their development. We have developed a large-scale simple production route using a relatively low synthesis temperature and direct acetylene chemical vapor deposition (CVD) using Co ion-exchanged zeolite Y (CoY) as the template. The Co2+ confined in the zeolite acts as Lewis acid sites to catalyze the pyrolysis of acetylene through the d-π coordination effect, making carbon deposition occur selectively inside the zeolite at 400 °C rather than on the external surface. By systematically investigating the CVD temperature and time, the optimum conditions of 8 h deposition at 400 °C produces an excellent 3D ordered-microporous structure and outstanding structure parameters (3 000 m2 g−1, 1.33 cm3 g−1). Its CO2 adsorption capacity and selectivity are 2.78 mmol g−1 (25 °C, 100 kPa) and 98, respectively. This simple CVD process allows the synthesis of high-quality ZTCs on a large scale at a low cost.

Cryo‐TEM Study of High‐Performance Iron Difluoride Cathode Enabled by Low Temperature CVD Carbon Coating

AbstractMetal fluorides (MFs) are regarded as high‐capacity conversion cathode materials for next‐generation lithium‐ion batteries with high energy density. However, these cathodes suffer from poor electronic conductivity, sluggish reaction kinetics, and deleterious cathode solid electrolyte interface (CEI) formation, which may cause rapid cell degradation upon cycling. Herein, a low temperature chemical vapor deposition (CVD) carbon coating technology is successfully achieved to coat MFs‐FeF2 with a thin amorphous carbon layer, which promotes the formation of a stable CEI with improved electronic and ionic transport property. Consequently, a discharge capacity higher than 450 mAh g−1 of the CVD coated FeF2 is achieved with a capacity retention at about 75% after 2500 cycles in a saturated electrolyte. Moreover, an unprecedented cycling performance with the discharge capacity of 350 mAh g−1 after 500 cycles in a super diluted electrolyte is also achieved. Advanced cryo‐electron microscopy reveals that the carbon coating significantly suppresses the undesirable CEI formation and promotes the formation of a thin CEI with excellent chemo‐mechanical property. This work provides a feasible technology to stabilize the important interface on MFs and offers a new strategy to accelerate the commercial adoption of such cathodes.

Towards Low-Temperature CVD Synthesis and Characterization of Mono- or Few-Layer Molybdenum Disulfide.

Molybdenum disulfide (MoS2) transistors are a promising alternative for the semiconductor industry due to their large on/off current ratio (>1010), immunity to short-channel effects, and unique switching characteristics. MoS2 has drawn considerable interest due to its intriguing electrical, optical, sensing, and catalytic properties. Monolayer MoS2 is a semiconducting material with a direct band gap of ~1.9 eV, which can be tuned. Commercially, the aim of synthesizing a novel material is to grow high-quality samples over a large area and at a low cost. Although chemical vapor deposition (CVD) growth techniques are associated with a low-cost pathway and large-area material growth, a drawback concerns meeting the high crystalline quality required for nanoelectronic and optoelectronic applications. This research presents a lower-temperature CVD for the repeatable synthesis of large-size mono- or few-layer MoS2 using the direct vapor phase sulfurization of MoO3. The samples grown on Si/SiO2 substrates demonstrate a uniform single-crystalline quality in Raman spectroscopy, photoluminescence (PL), scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and scanning transmission electron microscopy. These characterization techniques were targeted to confirm the uniform thickness, stoichiometry, and lattice spacing of the MoS2 layers. The MoS2 crystals were deposited over the entire surface of the sample substrate. With a detailed discussion of the CVD setup and an explanation of the process parameters that influence nucleation and growth, this work opens a new platform for the repeatable synthesis of highly crystalline mono- or few-layer MoS2 suitable for optoelectronic application.

Low T direct plasma assisted growth of graphene on sapphire and its integration in graphene/MoS2 heterostructure-based photodetectors

We report on outstanding photo-responsivity, R > 103 A/W, fast response (~0.1 s), and broadband sensitivity ranging from the UV to the NIR in two terminal graphene/MoS2 photodetectors. Our devices are based on the deterministic transfer of MoS2 on top of directly grown graphene on sapphire, and their performance outperforms previous similar photodetectors using large-scale grown graphene. Here we devise a protocol for the direct growth of transparent (transmittance, Tr > 90%), highly conductive (sheet resistance, R□ < 1 kΩ) uniform and continuous graphene films on sapphire at 700 °C by using plasma-assisted chemical vapor deposition (CVD) with C2H2/H2 gas mixtures. Our study demonstrates the successful use of plasma-assisted low-temperature CVD techniques to directly grow graphene on insulators for optoelectronic applications.

Chemical Vapor Deposition of Ru/RuSe2 Catalyst for Electrolytic Hydrogen Evolution Reaction

AbstractA one‐step synthesis of highly stable Ru/RuSe2 nanoparticles (NPs) on carbon paper is achieved using low temperature and pressure chemical vapor deposition (CVD), resulting in a heterointerface with multiple active sites for catalysis. The catalyst exhibits outstanding performance for the hydrogen evolution reaction (HER) in an alkaline solution, with low overpotentials and fast hydrogen adsorption and desorption kinetics. The Ru/RuSe2/C nanoparticle structure has the potential for large‐scale production and can be used as an efficient catalyst for HER.

Electrical Characteristics of CMOS-Compatible SiOx-Based Resistive-Switching Devices.

The electrical characteristics and resistive switching properties of memristive devices have been studied in a wide temperature range. The insulator and electrode materials of these devices (silicon oxide and titanium nitride, respectively) are fully compatible with conventional complementary metal-oxide-semiconductor (CMOS) fabrication processes. Silicon oxide is also obtained through the low-temperature chemical vapor deposition method. It is revealed that the as-fabricated devices do not require electroforming but their resistance state cannot be stored before thermal treatment. After the thermal treatment, the devices exhibit bipolar-type resistive switching with synaptic behavior. The conduction mechanisms in the device stack are associated with the effect of traps in the insulator, which form filaments in the places where the electric field is concentrated. The filaments shortcut the capacitance of the stack to different degrees in the high-resistance state (HRS) and in the low-resistance state (LRS). As a result, the electron transport possesses an activation nature with relatively low values of activation energy in an HRS. On the contrary, Ohm's law and tunneling are observed in an LRS. CMOS-compatible materials and low-temperature fabrication techniques enable the easy integration of the studied resistive-switching devices with traditional analog-digital circuits to implement new-generation hardware neuromorphic systems.

Nucleation and growth of graphene at different temperatures by plasma enhanced chemical vapor deposition

Temperature plays an important role in the synthesis of graphene by chemical vapor deposition. In the low-temperature plasma-enhanced chemical vapor deposition (PECVD) process, although the cleavage of hydrocarbon precursor no longer depends on growth temperature, which can affect the nucleation and growth of graphene by the diffusion and adsorption of active species, the catalytic ability of substrate and other factors, and ultimately lead to various growth of graphene. In this paper, the nucleation and growth of graphene at different temperatures by PECVD were studied. We noted that the nucleation and growth of graphene varied greatly in different temperature zones. Graphene could not be grown at low temperatures (< 600 ℃). At the medium and low temperature (650 ∼ 800 ℃), high nucleation density of graphene with nanometer size were produced. In the middle and high temperature region (850 ∼ 900 ℃), larger grains of graphene grown, and in the high temperature region (> 950 ℃), the coexistence of large and small grains was finally formed. In addition, the models of the nucleation and growth of graphene in different temperature zones were proposed.

Highly Dispersed Ni over a YSZ Anode Anchored by SiO2 at High Temperature through Low-Temperature Chemical Vapor Deposition

Supported Ni on yttria stabilized zirconia (YSZ) is the most widely used anode for a solid oxide fuel cell (SOFC), where Ni particles are easy to agglomerate at a high temperature of 1400 °C and reductive hydrothermal environments. In this study, Ni particles are successfully dispersed on YSZ through strong interaction between Ni and SiO2. The thin and amorphous SiO2 films, grown by low-temperature chemical vapor deposition (CVD), become spherical particles of nickel silicates uniformly dispersed on the YSZ skeleton after sintering at 1400 °C. Also, the SiO2-anchored Ni particles supported on YSZ (Ni/YSZ-SiO2) are obtained via direct reduction. The electrochemical performance of the Ni/YSZ-SiO2 anode shows a higher power density of approximately 18% than an unmodified Ni/YSZ anode, which resulted from the longer effective TPB area assigned to the highly dispersed Ni particles. The microstructure containing SiO2-anchored Ni particles exhibits high stability under testing and reductive hydrothermal conditions. Accordingly, the method of growing a SiO2 layer via low-temperature CVD is considered as a probable route for the preparation of the Ni/YSZ electrode material with a well-defined microstructure.

Conformal deposition of WS2 layered film by low-temperature metal-organic chemical vapor deposition

Large area multi-layer WS2 film has high potential as a channel material for MOSFETs in next-generation LSIs. State-of-the-art LSIs have complex three-dimensional (3D) structures such as vertical channels and multi-layer stacked channels surrounded by gate electrodes. To develop such structures, it is desirable to fabricate channel layers by CVD, which is suitable for conformal deposition along a substrate with a complicated 3D structure. In this study, we report on WS2 films deposited by Metal-Organic CVD using low-toxicity n-BuNC-W(CO)5 as a liquid tungsten precursor and (t-C4H9)2S2 for sulfur precursor. The deposited films have a roughly stoichiometric composition and are stable even after 60 d of shelf time in air atmosphere. A layered film along the 3D fin substrate parallel to the surface was fabricated on the entire structure.

Modeling and simulation of coverage and film properties in deposition process on large-scale pattern using statistical ensemble method

This study modeled deposition processes using statistical ensemble and feature-scale voxel methods to predict the coverage and film properties on a large-scale pattern for the first time. Certain new concepts, such as the use of probabilities to express physical and chemical phenomena occurring on the surface, interaction among voxels, and super particles for fast calculations, were introduced. Further, the model was used to analyze the experimental characteristic variation between the morphology and film density of SiN in low-temperature plasma-enhanced chemical vapor deposition using a SiH4/NH3/N2 gas mixture with different SiH4 flow rates, which has not been found in SiO2 films. The simulation results demonstrated the effect of the precursor mass in the gas phase on surface migration and morphology formation. In addition, a short residence time was required to prevent the generation of large and heavy precursors to realize good SiN coverage and film properties at a low temperature.

Adsorption and decomposition steps on Cu(111) of liquid aromatic hydrocarbon precursors for low-temperature CVD of graphene: A DFT study

Low-temperature chemical vapor deposition (LT-CVD) of graphene using liquid aromatic hydrocarbons holds technological advantages over conventional growth from methane. However, the nature of decomposition mechanisms of such precursors and their effectiveness in a LT-CVD process is still debated. We investigate by means of density functional theory adsorption energies and decomposition first steps on Cu(111) of single-ring aromatic hydrocarbons, such as benzene and toluene. Our results confirm the stronger stability with respect to methane of aromatic adsorbates, due to exchange of London dispersion forces with Cu surface; however, toluene exhibits improved bindings with respect to benzene. The adsorption energy slightly improves if additional methyl groups are substituted in benzene, as in o-xylene and 1,2,3-trimethylbenzene. Among decomposition reactions, dehydrogenation of the methyl group in toluene is energetically more favored (1.20 eV) than that of methane (1.52 eV) or aromatic C-rings (1.67 eV and 1.72 eV for benzene and toluene), while demethylation of toluene remains negligible due to the prohibitive energy barrier (2.49 eV). Methyl dehydrogenation in toluene leads to the abundant formation of adsorbed benzyl radicals onto Cu in an almost parallel-to-surface configuration, as active species for graphene nucleation. Toluene (and to a lesser extent o-xylene and 1,2,3-trimethylbenzene) should be thus preferred to benzene in LT-CVD of graphene.

Low-Temperature Direct Growth of Nanocrystalline Multilayer Graphene on Silver with Long-Term Surface Passivation.

A wide variety of transition metals, including copper and gold, have been successfully used as substrates for graphene growth. On the other hand, it has been challenging to grow graphene on silver, so realistic applications by combining graphene and silver for improved electrode stability and enhanced surface plasmon resonance in organic light-emitting diodes and biosensing have not been realized to date. Here, we demonstrate the surface passivation of silver through the single-step rapid growth of nanocrystalline multilayer graphene on silver via low-temperature plasma-enhanced chemical vapor deposition (PECVD). The effect of the growth time on the graphene quality and the underlying silver characteristics is investigated by Raman spectroscopy, X-ray diffraction, atomic force microscopy, X-ray photoelectron spectroscopy (XPS), and cross-sectional annular dark-field scanning transmission electron microscopy (ADF-STEM). These results reveal nanocrystalline graphene structures with turbostratic layer stacking. Based on the XPS and ADF-STEM results, a PECVD growth mechanism of graphene on silver is proposed. The multilayer graphene also provides excellent long-term protection of the underlying silver surface from oxidation after 5 months of air exposure. This development thus paves the way toward realizing technological applications based on graphene-protected silver surfaces and electrodes as well as hybrid graphene-silver plasmonics.

Recent progress in low-temperature CVD growth of 2D materials

Abstract Two-dimensional (2D) materials have emerged as a promising class of materials with unique physical and chemical properties that offer exciting prospects for various applications. Among all the synthesis methods, chemical vapor deposition (CVD) techniques have demonstrated great advantages in the large-scale production of 2D materials with a controlled thickness. One of the main challenges in the growth of 2D materials is the need for high temperatures and crystalline substrates, which restrict the scalability and compatibility of 2D materials with existing manufacturing processes, due to the high thermal budget and the necessity to transfer the 2D films to secondary substrates. Low-temperature growth methods for 2D materials have the potential to overcome this challenge and enable the integration of 2D materials into a wide range of devices and applications. In recent years, there have been substantial efforts to develop low-temperature growth techniques for different 2D materials, including graphene, hexagonal boron nitride and transition metal dichalcogenides. These methods include thermal CVD, plasma-enhanced CVD, atomic layer deposition and metal-organic chemical vapor deposition. This review not only discusses the progress in the growth but also highlights the applications of low-temperature-grown 2D materials in various fields, such as field effect transistors, sensors, photodetectors, catalysts, batteries and supercapacitors.

Photoresponse of CVD grown crystalline quantum dot-embedded covalent organic framework thin film.

Covalent organic frameworks (COFs) are a new family of novel 2D materials which are highly sought after for integration into future sensors and other devices for their highly porous structures and large surface areas. However, low-temperature large-area growth of these semiconductive materials with a clean surface for direct device applications is still a challenging task. To provide an on-chip photonic device, a COF366-Quantum dot (COF366-QDs) thin-film-based device fabricated by in situ chemical vapor deposition (CVD) is presented. The high-resolution transmission electron microscopy (HRTEM) displays the formation of the periodic, crystalline and porous framework of the COF layer with mono-dispersed QDs of average particle size of ∼2.5-3 nm. The fabricated COF366-QD layer acts as a photoactive layer in the photonic device with an Au-COFQD-Au structure where a conduction path is formed between the metal electrodes through a network of COF layer with embedded QDs. The device shows photoactive response under 514 nm visible light with a very low dark current of 4.36 × 10-11 A with a minimum light detection capability of 160 nW and a responsivity of ∼3.42 A W-1. The photonic device was highly stable for successive switching cycles with very low attenuation. To our knowledge, this is the first report of a Quantum dot embedded COF366 thin-film by chemical vapor deposition. The proposed interfacing of COF366-QD thin-films on silicon substrate using in situ low-temperature CVD technique can be highly valuable for the development of transfer-free, clean, and low-cost preparation of industrial-scale organic electronics, optoelectronic device applications, and lab-on-chip based technologies for a wide range of future applications.