Thermal Chemical Vapor Deposition Research Articles

Injection of low-energy SiCH5+ ion-beam to Si substrate during chemical vapor deposition process using methylsilane

Silicon carbide (SiC) films produced on Si substrates by the thermal chemical vapor deposition (CVD) method using methylsilane (MS) were compared with those made by the mass-selected ion-beam deposition (MSIBD) method using MS-derived 100 eV SiCH5+ ions. We also investigated the effect of SiCH5+ ion injections during the CVD process. When the substrate was 550 °C, no distinct peaks were found in the Fourier transform infrared (FTIR) spectroscopy spectra of the samples obtained by both CVD and MSIBD. By contrast, an obvious FTIR peak due to the presence of SiC was observed when SiCH5+ ions were injected to a substrate in conjunction with MS. In the case of 650 °C, we found that the film thickness was significantly increased when additional SiCH5+ ions were injected during the CVD process using MS. These results suggest that the interaction between MS and SiCH5+ has some effects on the SiC film formation at the substrate temperatures 550 and 650 °C. When the substrate temperature was set at 750 °C, the effect of the SiCH5+ ion injection on the SiC film formation was negligibly small compared to that of CVD.

Fabrication, characterization and optical properties of Au-decorated Bi2Se3 nanoplatelets

Au-decorated Bi2Se3 nanoplatelet heterostructures are fabricated by a two-step process of thermal CVD at 600 °C and magnetron sputtering at room-temperature. The crystal structures and binding energies of rhombohedral Bi2Se3 and FCC Au are determined by XRD, HRTEM, XPS, and Raman spectroscopy. XPS and Raman spectroscopy reveal the interaction between Au and Bi2Se3 by shifting in the binding energies of Au–Au, Au–Se and Bi–Se bonds and the wavenumber of A1g2 and Eg2 modes. Au-decorated Bi2Se3 nanoplatelet heterostructures are observed using FESEM, and confirmed by XPS, Raman spectroscopy, and HRTEM imaging. Their optical band gap of the Au-decorated Bi2Se3 nanoplatelet heterostructures increases with Au thickness about 1.92-fold as much as that of pristine Bi2Se3 (0.39 eV), owing to the Burstein-Moss effect. The optical absorptance of the Au-decorated Bi2Se3 nanoplatelet heterostructures revealed increment with wavelength from 200 to 500 nm and decrement with increasing wavelength from 500 to 800 nm.

Post-growth enhancement of CVD-grown hexagonal boron nitride films on sapphire

This study explores the effect of post-growth annealing on hexagonal boron nitride (hBN) films grown on c-sapphire substrates by chemical vapor deposition as post-growth annealing proves to overcome the equipment limitations of commercial thermal CVD systems and offers a simplistic way to enhance the properties of the as-grown hBN films useful for multiple-wafer scalability, thereby making it a practical approach for industrial manufacturing of high-quality hBN films. hBN films are grown at 1100 °C by CVD process and are annealed up to 1300 °C under nitrogen atmosphere in an annealing furnace system. It is observed that the annealed hBN films are continuous and have a pronounced granular structure as compared to the as-grown hBN films. The annealed BN films retain the 1:1 B:N stoichiometry and the hexagonal phase as observed in the as-grown hBN films. The optical bandgap of the annealed hBN films is augmented from 5.70 eV to 5.82 eV as a result of the annealing treatment, indicating enhanced optical properties.

Precursor mediated and defect engineered ZnO nanostructures using thermal chemical vapor deposition for green light emission

We used thermal chemical vapour deposition to synthesize zinc oxide nanostructured thin films on n-type silicon substrate using zinc oxide (ZnO) and zinc chloride (ZnCl2) powder precursors in conjunction with bulk graphite powder. The synthesized ZnO nanostructured thin films structures are polycrystalline with a relatively enhanced c-axis orientation for ZnO powder precursor with respect to that of ZnCl2 precursor. The scanning electron microscopic analysis substantiate the higher c-axis orientation of ZnO nanostructures, grown using ZnO powder precursor. The photoluminescence (PL) and UV–Vis measurements suggest the presence of zinc vacancies, causing the green emission from both nanostructured thin films. The measured bandgap of ZnO nanostructured thin film using ZnO powder precursor is slightly higher than that of ZnCl2 powder precursor. The capacitance-voltage and Mott-Schottky measurements showed the n-type characteristics with 6.3 × 1016 cm−3 and 2.7 × 1015 cm−3 carrier densities for ZnO nanostructured thin films prepared using ZnO and ZnCl2 precursors, respectively. The current-voltage measurements showed relatively lower current for ZnO nanostructured thin films, synthesized using ZnCl2 precursor, signifying the presence of zinc vacancies trap sites and is also consistent with Mott-Schottky measurements, showing lower carrier concentrations with respect to that of ZnO precursor derived ZnO nanostructured thin films. Thus, controlled Zn vacancies in ZnO nanostructured thin films may lead to the efficient green light emitters, useful for green light colour emission applications.

Graphene Properties, Synthesis and Applications: A Review.

We have evaluated some of the most recent breakthroughs in the synthesis and applications of graphene and graphene-based nanomaterials. This review includes three major categories. The first section consists of an overview of the structure and properties, including thermal, optical, and electrical transport. Recent developments in the synthesis techniques are elaborated in the second section. A number of top–down strategies for the synthesis of graphene, including exfoliation and chemical reduction of graphene oxide, are discussed. A few bottom–up synthesis methods for graphene are also covered, including thermal chemical vapor deposition, plasma-enhanced chemical vapor deposition, thermal decomposition of silicon, unzipping of carbon nanotubes, and others. The final section provides the recent innovations in graphene applications and the commercial availability of graphene-based devices.

Sugarcane waste based synthesized graphene like nanocarbon (GNC) for shock absorption application

We report on the synthesis, characterization, and shock absorption characteristics of Graphene like Nano Carbon (GNC) prepared by the combustion of biomass (sugarcane waste) using the Rapid Thermal Chemical Vapor Deposition (RT-CVD) technique. Post synthesis, the samples were purified by subjecting them to intercalation and annealing. The synthesised GNCs were then characterised by Raman, Infrared, and UV spectroscopy, together with microscopy. In analysis, the GNCs were observed to be rectangular in shape, thick, having sharp edges and corners, and having an area ∼50–200 μm2 with wrinkles on it. TEM images showed that GNCs exhibit smooth wrinkle contours with bits of dark showing conjugated graphene layers stacked together having multiple defects and dislocations. In Raman spectroscopy, D peak is observed at ∼1335 cm−1 and G peak is observed at ∼1591 cm−1 indicating GNC consists of sp2 and sp3 hybridised complex phases. The Crystalline Length (La), Disordered Length (LD) and Defect Density (nD) have been estimated to be 21.26 nm, 9.60 nm and 1.084 × 10−12/cm2 respectively. FTIR spectra revealed that C-C is present at ∼1420 cm−1 and C-O-C is present at 900 cm−1. In Uv measurements, no typical absorption peak was observed due to the micrometre size of GNC. The shock absorption properties of GNCs were investigated by subjecting them to pressure (~1.5 GPa) using a Split Hopkinson Pressure Bar (SHPB). The obtained mechanical parameters revealed that GNCs absorbed ∼65% of incident energy and ∼15% transmitted, demonstrating their utility in the development of armour, shock and blast mitigating blocks, defense, and space applications.

Electrodeposition of Ni-Fe Alloy in Presence of Complexing Agent

The nickel-iron alloys have been widely used for versatile soft magnetic applications and electro-magnetic applications due to their magnetic properties for a long time. Also, it has been discovered that Ni-Fe alloy near 36 wt% Ni shows almost zero thermal expansion composition(CTE) in a wide temperature range (~150 ℃). The phenomenon showing low CTE in a specific composition is called the Invar effect. Due to the Invar effect, Invar alloys are used for temperature-sensitive applications such as oscillators and fiber-optic package parts. Invar alloy films are used for fine metal masks, an essential part of OLED fabrication. The invar film currently in use is fabricated using the pyrometallurgy method, more than 20um thick. However, miniaturization and high performance of the products require the thinner thickness of the Invar film, around 10um thick which shows the need for a bottom-up fabrication process of invar film. There are various methodologies to fabricate thin films, such as thermal evaporation, sputtering, CVD, and electrodeposition. Most fabricating processes are the vacuum process, a high-cost and non-continuous process. On the other hand, electrodeposition is a non-vacuum process, relatively low-cost, large-scale, and continuous process.Despite these advantages, there are some obstacles to gaining the Invar thin film by electrodeposition, such as anomalous deposition, composition uniformity, and higher CTE of electrodeposited Invar film. There are researches[1-3] about electrodeposited Ni-Fe thin films in the aspect of CTE, magnetic properties, crystal structures, etc. However, very few researchers have seen the effect of complexing agents other than specific complexing agents such as boric acid and ascorbic acid. In addition, Ni-Fe electrodeposition shows very different results depending on temperature and agitation, but no research confirms the effect on various complexing agents under the same condition.In this study, we synthesized Ni-Fe alloy thin film by electrodeposition in the presence of various complexing agents with different functional groups (amine, carboxyl, alcohol, etc.) such as glycolic acid, malonic acid, ethylenediamine, etc. on 20um stainless 304 foil substrates. The electrodeposition was conducted under the aqueous acidic bath(pH 2) at 55℃. Electrochemical studies were conducted to set appropriate potential and current density for electrodeposition. The thin film was characterized by SEM, EDS, XRD, and copper strip tests to observe the difference in composition, surface morphology, phase, and internal stress.

Stress Relaxation in SGOI Structure Obtained by Condensation

The development of effective buffer layer has required years of work in order to obtain relaxed SiGe substrates [1]. However, main drawback of this approach relies on the presence of embedded and numerous dislocations which can be detrimental for optimal applications. Recently, a surprising relaxation phenomenon has been observed on specific Silicon-Germanium On Insulator (SGOI) structures [4-5].It has been observed that when the sample is heated, slippage is observed at the SGOI/Buried Oxide (BOX) interface.The phenomenon is not clearly understood. However, several explanations have been raised. It can be explained by the mechanical properties by Ge-O bonds which are weaker than the Si-O bonds at the SGOI/BOX interface causing the slip. [2] Also, the Ge atoms in the last crystalline layer at the BOX interface decreases the quantity of Si atoms inducing less bonds between the Si atoms of SGOI and the BOX.We suggest to take advantage of this phenomenon to obtain fully relaxed SGOI layers without dislocations. This new approach would allow to create high performance relaxed SGOI layers in industrial conditions with 300 mm wafers. This innovation is relevant for several applications, such as optical applications and the formation of base substrate to generate tensile Si epitaxy layer. It has to be noticed that any Ge concentration until pure GeOI structure is possible.Figure 1 shows the different process steps to obtain relaxed SGOI layer explained below. SiGe epitaxy (fig.1-a) is performed on an 300mm SOI wafer by Rapid Thermal Chemical Vapor Deposition (RT-CVD). Germane (GeH4) and Dichlorosilane (DCS) are used as precursor gases to obtain a 20nm thick fully strained Si0.8Ge0.2 layer. Upstream work is performed to improve the uniformity of the SiGe layer (thickness and composition) within the 300mm wafer. Indeed, they are key parameters impacting Ge concentration within wafer uniformity obtained after condensation.[3]Then, condensation is performed (fig.1-b) using thermal oxidation in a 300mm industrial furnace under N2/O2 atmosphere at 1000°C during several hours. Condensation is tuned to obtain the desired Ge concentration in the SGOI structure. Condensation allows to transform a SiGe/Si/BOX structure into SiGe/BOX structure called SGOI. Two mechanisms are involved in the condensation. The first mechanism is the Si-selective oxidation in the SiGe layer allowing Ge atoms to accumulate at the oxidation interface. The second mechanism is the Ge diffusion in the structure which allows SiGe inter-diffusion. The Ge atoms are maintained and homogenized in depth of the SGOI layer during the interdiffusion mechanism thanks to the BOX acting as a diffusion barrier. [2]During this work, the layer composition, the thickness as well as the stress were characterized by ellipsometry, XRR, XRD and SIMS. In addition, the surface was analyzed by AFM to detect any crystal defects.In this study, we propose to investigate the relaxation of SGOI layer with a concentration of Ge=50% because such structure shows no defects after condensation [2]. Thereafter, it will be possible to carry out GeOI in the future.Figure 2 shows SiGe thickness and density measurement by XRR. A thickness variation of 13.67 A and a density variation of 0.22g/cm3 of the SGOI layer after condensation on the whole wafer is obtained. The average density is 4,31g/cm3 with a concentration of %Ge=51% which was our target concentration.Then, the relaxation phenomenon is studied using anneals in the temperature range [700;900] °C during several hours. Indeed, we chose a temperature close to the SiO2 viscosity temperature and a long annealing time allowing to generate a slow slip thus limiting defects.Figure 3 shows a RSM map obtained by XRD of an Si0.5Ge0.5OI layer after annealing at 800°C for 2h. The mapping shows Si substrate as well as the layer relaxed along the (113) and (224) planes at an angle Φ=45°. RSM map allows to calculate the relaxation rate which is 22%. The relaxation on the sample is a success that remains to be improved by annealing time or temperatures to be optimized.This new approach would allow the realization a defect free relaxed SGOI layer under industrial conditions on a 300mm wafer. It would provide a new method for applications such as optical or the growth of tensile Si channels.[1] P.M.Mooney, Materials Science and Engineering, 1996[2] F.Roze. PhD thesis, 2018[3] D.Valenducq, PhD thesis, 2021[4] V.Boureau et al., ECS, 2018[5] Usuda, Koji, et al., Solid-State Electronics, 2013 Figure 1

3D porous graphene/double-walled carbon nanotubes/gold nanoparticles hybrid film for modifying electrochemical electrode

3D porous graphene/carbon nanotubes (Gr/CNTs) hybrid films containing nanoparticles have introduced new possibilities for the development of high-performance electrochemical sensors. Herein, we developed a novel technique for the fabrication of 3D porous graphene/double-walled carbon nanotubes/gold nanoparticles (Gr/DWCNTs/AuNPs) hybrid film on copper foils by using the thermal chemical vapor deposition (CVD) method. On these porous films, DWCNTs, Gr winkles, and a homogeneous AuNP covering were observed. These prepared 3D porous films were then transferred onto the surface of screen-printed electrodes (SPE) to investigate the electrochemical properties by using cyclic voltammetry (CV) technique. Consequently, 3D porous Gr/DWCNTs/AuNPs film modified electrodes exhibited good electrochemical characteristics with an active surface area of 2.76 times higher than that of Gr/DWCNTs film. This is due to the use of AuNPs, which improves the conductivity and surface area of the porous film.

Synthesis and Characterization of Silica–Tantala Microporous Membranes for Gas Separations Fabricated Using Chemical Vapor Deposition

Composite membranes consisting of microporous tantalum-doped silica layers supported on mesoporous alumina substrates were fabricated using chemical vapor deposition (CVD) in both thermal decomposition and counter-flow oxidative deposition modes. Tetraethyl orthosilicate (TEOS) was used as the silica precursor and tantalum (V) ethoxide (TaEO) as the tantalum source. Amounts of TaEO from 0 mol% to 40 mol% were used in the CVD gas mixture and high H2 permeances above 10−7 mol m−2 s−1 Pa−1 were obtained for all conditions. Close examination was made of the H2/CH4 and O2/CH4 selectivities due to the potential use of these membranes in methane reforming or partial oxidation of methane applications. Increasing deposition temperature correlated with increasing H2/CH4 selectivity at the expense of O2/CH4 selectivity, suggesting a need to optimize membrane synthesis for a specific selectivity. Measured at 400 °C, the highest H2/CH4 selectivity of 530 resulted from thermal CVD at 650 °C, whereas the highest O2/CH4 selectivity of 6 resulted from thermal CVD at 600 °C. The analysis of the membranes attempted by elemental analysis, X-ray photoelectron spectroscopy, and X-ray absorption near-edge spectroscopy revealed that Ta was undetectable because of instrumental limitations. However, the physical properties of the membranes indicated that the Ta must have been present at least at dopant levels. It was found that the pore size of the resultant membranes increased from 0.35 nm for pure Si to 0.37 nm for a membrane prepared with 40 mol% Ta. Similarly, an increase in Ta in the feed resulted in an increase in O2/CH4 selectivity at the expense of H2/CH4 selectivity. Additionally, it resulted in a decrease in hydrothermal stability, with the membranes prepared with higher Ta suffering greater permeance and selectivity declines during 96 h of exposure to 16 mol% H2O in Ar at 650 °C.

Growth of silicon carbide multilayers with varying preferred growth orientation

SiC multilayer coatings were deposited via thermal chemical vapor deposition (CVD) using silicon tetrachloride (SiCl4) and various hydrocarbons under identical growth conditions, i.e. at 1100 °C and 10 kPa. The coatings consisted of layers whose preferred growth orientation alternated between random and highly 〈111〉-oriented. The randomly oriented layers were prepared with either methane (CH4) or ethylene (C2H4) as carbon precursor, whereas the highly 〈111〉-oriented layers were grown utilizing toluene (C7H8) as carbon precursor. In this work, we demonstrated how to fabricate multilayer coatings with different growth orientations by merely switching between hydrocarbons. Moreover, the success in depositing multilayer coatings on both flat and structured graphite substrates has strengthened the assumption proposed in our previous study that the growth of highly 〈111〉-oriented SiC coatings using C7H8 was primarily driven by chemical surface reactions.

Effect of Evaporation Boat-Substrate Distance on the Formation of Zinc Oxide Nanostructures

Zinc Oxide (ZnO) is one of the important semiconductor materials which contribute effectively to the development of the semiconductor industry technology. ZnO nanostructures (NSs) were synthesized using thermal chemical vapor deposition (TCVD) technique under atmospheric pressure at different evaporation boat-substrate distances. ZnO NSs were prepared by oxidizing Znic acetate dihydrate powder within quartz tube instead of its outside. The effect of change evaporation boat-substrate distance (2.5, 4.5, 6.5 and 8.5 cm) on the optical and structural properties of ZnO NSs were studied. ZnO NSs were characterized by UV-Visible spectrophotometer, X-ray diffraction (XRD) technique and photoluminescence (PL) spectroscopy to evaluate its optical and structural properties. Optical band gap measurement results exhibited a red-shifted from (3.25 eV) to (3.05 eV), as the separation distance increased from (2.5 cm) to (8.5 cm), respectively. XRD technique confirms that metal oxide was ZnO and having hexagonal structure. The average crystallite size of the samples was decreased from 63.4 to 58.3 nm, with the increase in separation distance from 2.5 to 8.5 cm. Also, the sharpness, strong intensity and narrow width of dominant diffraction peak indicate the high crystallinity of the prepared ZnO NSs. The PL spectra of the ZnO NSs revealed a wide deep-level emission for all the prepared samples. ZnO NSs grown by TCVD technique may provide potential applications in nano-photovoltaics and nano-photodetectors.

Development of electrochemical sensor based on polyalanine/CuCl-Gr/DWCNTs for highly sensitive detection of glyphosate

In this study, a hybrid film based on copper chloride doped graphene/double-walled carbon nanotubes (CuCl-Gr/DWCNTs) was prepared for further application in detection of glyphosate (Gly) at low levels. Gr/DWCNTs film was first fabricated on copper foil and then modified with CuCl using thermal chemical vapor deposition (CVD) technique, before being transferred onto gold screen printed electrode (AuE). An ad-layer polyalanine (PolyA) was introduced on the top of CuCl-Gr/DWCNTs hybrid film by direct electro-deposition from alanine monomer in order to facilitate immobilization of enzyme molecules. The as-prepared PolyA/CuCl-Gr/DWCNT film was finally used for developing Gly electrochemical sensor based on inhibition of Gly towards urease enzyme. The developed Gly sensor showed a high sensitivity of 1383 (μA.ppb−1.cm−2) and a low detection limit (LOD) of 0.54 × 10−3 ppb in a wide concentration range of 10−3 ppb - 50 ppb. Moreover, the sensor was also applied to the detection of Gly in river water samples, with recoveries ranging from 112.8 % to 113.9 % (RSD: 1.54–2.03 %). The results suggested that the developed sensor with high sensitivity can be used for the detection of Gly in water sources.

Conversion of Carbon Dioxide into Chemical Vapor Deposited Graphene with Controllable Number of Layers via Hydrogen Plasma Pre-Treatment.

In this work, we report the conversion of carbon dioxide (CO2) gas into graphene on copper foil by using a thermal chemical vapor deposition (CVD) method assisted by hydrogen (H2) plasma pre-treatment. The synthesized graphene has been characterized by Raman spectroscopy, X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The results show the controllable number of layers (two to six layers) of high-quality graphene by adjusting H2 plasma pre-treatment powers (100–400 W). The number of layers is reduced with increasing H2 plasma pre-treatment powers due to the direct modification of metal catalyst surfaces. Bilayer graphene can be well grown with H2 plasma pre-treatment powers of 400 W while few-layer graphene has been successfully formed under H2 plasma pre-treatment powers ranging from 100 to 300 W. The formation mechanism is highlighted.

Synchrotron EXAFS spectroscopy and density functional theory studies of Pd/MoS2 Schottky-type nano/hetero-junctions

Molybdenum disulfide (MoS2) nanostructures are grown on the silicon substrates using thermal chemical vapor deposition and then Pd anchoring on them is carried out by DC magnetron sputtering to form Pd/MoS2 Schottky-type nano/hetero-junctions. Extended X-ray absorption fine structure (EXAFS) spectroscopy is applied to study the local structure around the molybdenum K-edge. In this way, the kind, coordination number, and distance of neighbors of absorber atom are determined. Moreover, structural analysis has been performed by X-ray diffraction. Optical studies are conducted by UV–Visible and differential reflectance spectroscopy. The electronic properties of the samples are examined using Raman spectroscopy with an excitation laser at 532 nm. Furthermore, the surface chemical analysis is monitored by X-ray photoelectronspectroscopy. In addition, a simulation study of the structural and electronical properties of the samples is carried out to understand the effect of Pd adding on MoS2 structure using Quantum ESPRESSO software. The reasonable place of the Pd atom after Pd anchoring in MoS2 lattice is obtained.

Multi-layer growth of tungsten disulphide using thermal chemical vapour deposition

Transition metal dichalcogenides, in their 2D form are proven to be significant material for next-generation nanoelectronic and optoelectronic devices. However, for the realization of practical applications, it is very important to devise facile, and cost-effective synthesis routes without compromising their quality. In this work, multi-layer 2D tungsten disulphide (WS2) has been synthesized using thermal assisted chemical vapour deposition technique. The synthesis was carried out using two different substrates, and the effect of relative position of tungsten trioxide powder and substrate on the multi-layer growth of WS2 has been studied. The nucleation density and layer number is observed to be varying with the reaction time and the type of the substrate. The as-synthesized samples were characterized by using field emission scanning electron microscopy, and Raman spectroscopy.

Low-energy Ar+ ion beam induced chemical vapor deposition of silicon carbide films using dimethylsilane

In this paper, a methodology for silicon carbide (SiC) film formation by ion beam induced chemical vapor deposition (IBICVD) using dimethylsilane (DMS) is presented. Both pure DMS gas and Ar+ ion beam were simultaneously injected to a Si substrate. The Ar+ ion energy was 100 eV. The Si substrate temperature was 400, 600, or 800 °C. The duration of each ion beam injection experiment was 10 h. When the substrate temperature was 400 °C, no film formation occurred by the IBICVD experiment. In the case of 600 °C, a film was found to be formed on the substrate by the injection of both DMS gas and Ar+ ion beam. Although Fourier transform infrared (FTIR) spectroscopy measurement of the film showed that the film consisted of SiC, the film thickness was not enough to analyze the film characteristics further. When the Si substrate was set at 800 °C, a film was formed on the substrate by IBICVD. FTIR, X-ray diffraction, and X-ray photoelectron spectroscopy (XPS) measurements of the film showed the occurrence of SiC deposition. The XPS measurement also showed that the atomic concentration ratio of carbon to silicon (C/Si ratio) of the film was 1.36. Therefore, excessive C atoms were incorporated to the deposited films. On the contrary, the C/Si ratio of a SiC film prepared by the thermal CVD method using DMS was 1.88. These results suggest that the Ar+ ion beam induced chemical vapor deposition using DMS is useful for reducing of the amount of C atoms to be excessively included in the film.

Size-controllable synthesis of 2D Mn3O4 triangular-shaped nanosheets by thermal chemical vapor deposition

In this study, monolayer up to few-layer of Mn 3 O 4 nanosheets grown on c-Si (111) substrates using a thermal chemical vapor deposition (TCVD) technique were investigated in detail, where the growth reaction pressure was varied from 0.12 to 0.72 mbar. The morphology of the triangular-shaped Mn 3 O 4 nanosheet greatly depends on the atomic ratio of O to Mn, which eventually determines the horizontal growth rate of the triangle's edges that forms the shape of the nanosheet. A low O/Mn ratio results in the formation of a triangle with a longer edge as compared to a high O/Mn ratio which produces a shorter edge. The 2D triangular-shaped Mn 3 O 4 nanosheets prepared at 0.42 mbar exhibited a thickness of ∼1.10–2.29 nm (equivalent to the approximate thickness of monolayer-bilayer) with a maximum edge length of ∼850 nm, whereas ultrathin nanosheets with a thickness of ∼1.93–4.68 nm (equivalent to ∼2–3 layers) with an edge length of <250 nm were found at the highest reaction pressure of 0.72 mbar. The results imply a synthesis of 2D Mn 3 O 4 nanosheets with controllability of thickness and edge length that vary from monolayer to ultrathin nanosheets at different O/Mn ratios. By presuming that the Mn 3 O 4 growth along the [001] direction, we performed first-principles density-functional theory calculations to validate the structure and electronic properties of these 2D Mn 3 O 4 nanosheets. Our calculated lattice parameters for the 2D Mn 3 O 4 were considerably close to the experimental measurements. The band structure calculations predicted that the 2D Mn 3 O 4 possessed metallic characteristics. This paper discusses the seed-assisted growth mechanism of these 2D Mn 3 O 4 nanosheets. • Thermal CVD grown Mn 3 O 4 nanosheet. • The atomic ratio between O and Mn controlled the morphologies of the triangular-shaped Mn 3 O 4 nanosheet. • A low O/Mn ratio produced monolayer 2D triangular shaped with a longer edge. • A high O/Mn ratio produced ultrathin nanosheets with thickness up to 3 layers and shorter edge. • Based on DFT calculations, 2D Mn 3 O 4 nanosheet exhibited metallic characteristics.

Characterization of High-Performance Zinc Chloride Activated Biochar Modified by Thermal Chemical Vapor Deposition (CVD) and Its Removal Mechanism of Aqueous Nitrate Ions

Characterization of High-Performance Zinc Chloride Activated Biochar Modified by Thermal Chemical Vapor Deposition (CVD) and Its Removal Mechanism of Aqueous Nitrate Ions

Highly Water-Repellent and Anti-Reflective Glass Based on a Hierarchical Nanoporous Layer

Optically anti-reflective and water-repellent glass is required for solar cell covers to improve power-generation efficiency due to transparency improvement and dirt removal. Research has been conducted in recent years on technologies that do not use fluorine materials. In this study, we focused on the anti-reflective properties and microstructure of hierarchical nanoporous layer (HNL) glass and used it as a substrate. As a result, we have achieved both strong anti-reflectivity and high water repellency on HNL glass by coating polydimethylsiloxane (PDMS) using baking and thermal chemical vapor deposition (CVD). The surfaces showed a significantly higher sliding velocity of water droplets than the PDMS-treated material on the flat glass plate. They also showed such water repellency that the droplets bounced off the surface.