Injection Chemical Vapor Deposition Research Articles

Rare-earth doped yttrium silicate (Y2SiO5) thin films grown by chemical vapour deposition for quantum technologies

Yttrium orthosilicate (Y2SiO5 - YSO) is one of the most promising crystals to host rare-earth (RE) ions for quantum technologies applications. In this matrix, they indeed exhibit narrow optical and spin linewidths that can be exploited to develop quantum memories or quantum information processing capabilities. In this paper, we propose a new method to grow RE doped silicate thin films on silicon wafers based on direct liquid injection chemical vapour deposition (DLI-CVD). We optimize the deposition and annealing conditions to achieve formation of the high temperature X2-YSO phase. The phase purity and crystalline quality of the films are assessed by evaluating the optical properties of Eu3+ ions embedded in this oxide matrix. In view of the results, we discuss the possible phase formation mechanisms, and the potential of this new wafer-compatible form of YSO for quantum technologies applications.

Integration of epitaxial LiNbO3 thin films with silicon technology

Development of bulk acoustic wave filters with ultra-wide pass bands and operating at high frequencies for 5th and 6th generation telecommunication applications and micro-scale actuators, energy harvesters and sensors requires lead-free piezoelectric thin films with high electromechanical coupling and compatible with Si technology. In this paper, the epitaxial growth of 36°Y-X and 30°X-Y LiNbO3 films by direct liquid injection chemical vapour deposition on Si substrates by using epitaxial SrTiO3 layers, grown by molecular beam epitaxy, has been demonstrated. The stability of the interfaces and chemical interactions between SrTiO3, LiNbO3 and Si were studied experimentally and by thermodynamical calculations. The experimental conditions for pure 36°Y-X orientation growth have been optimized. The piezoelectricity of epitaxial 36°Y-X LiNbO3/SrTiO3/Si films was confirmed by means of piezoelectric force microscopy measurements and the ferroelectric domain inversion was attained at 85 kV.cm−1 as expected for the nearly stoichiometric LiNbO3. According to the theoretical calculations, 36°Y-X LiNbO3 films on Si could offer an electromechanical coupling of 24.4% for thickness extension excitation of bulk acoustic waves and a comparable figure of merit of actuators and vibrational energy harvesters to that of standard PbZr1−x Ti x O3 films.

Investigating the thermal and irradiation stability of chemical vapor deposited erbium oxide tritium barrier coatings for Li breeder blanket applications

Two-micron thick erbium oxide tritium barrier coatings have been prepared by aerosol injection chemical vapor deposition and subsequently irradiated with 33 MeV Au 6+ ions at fluences up to 2.1 × 1016 Au/m2 at 550°C. Scanning electron microscopy, X-ray diffraction and transmission electron microscopy were used to investigate the coating surface morphologies, phase structures and cross-sectional microstructures as a function of irradiation and thermal treatment. XRD data was also used to extract information about the evolution of lattice strain in the coating. Some of the cubic erbia transformed to the monoclinic phase in the sample that was ion irradiated at temperature, and this was accompanied by a change from columnar to a more equiaxed grain structure. All coatings were found to experience out-of-plane tensile strain, thought to originate from thermal stresses created during coating manufacture. Thermal treatment reduced microstrains present in the as-deposited sample, whilst the cubic-to-monoclinic phase transformation reduced strain in the cubic phase but increased strain in the monoclinic phase.

Enhanced solar water splitting using bismuth ferrite photoanodes grown by direct liquid injection chemical vapor deposition

Enhanced solar water splitting using bismuth ferrite photoanodes grown by direct liquid injection chemical vapor deposition

Excellent field emission with enhanced photodetection behavior of multiwalled carbon nanotubes: experimental and theoretical study

In this study, we synthesized multiwalled carbon nanotubes (MWCNTs) using the direct liquid injection chemical vapor deposition (DLICVD) method, the growth temperatures were varied to investigate their unique properties.

Dispersion of surface elastic waves on Z-LiNbO3 films on Z-sapphire

Epitaxial thin films of lithium niobate with a thickness of 160 nm, oriented along the crystallographic c axis, were grown by direct liquid injection chemical vapor deposition on c-sapphire substrates. Different families of very high-frequency surface acoustic waves with general polarization exist in such piezoelectric films on high-velocity substrates. Surface Brillouin light scattering measurements, complemented with fast finite element analysis of wave dispersion, demonstrate Rayleigh, leaky shear, and leaky longitudinal surface waves, excited at frequencies between 10 and 30 GHz. The Brillouin technique reveals dispersion and anisotropy of propagation without the implementation of high-frequency surface acoustic wave transducers.

Growth of Samarium-Substituted Epitaxial Bismuth Ferrite Films by Chemical Vapor Deposition

There is great interest in BiFeO3 and various substituted heterostructures for ferroelectric random-access memory (RAM) and energy-efficient magnetoelectric logic and memory devices. High-quality heterostructures of these material systems with smooth topography are desirable to incorporate into functional devices. For this purpose, the direct liquid injection chemical vapor deposition (DLI-CVD) technique has been employed to grow BiFeO3 and Bi-site samarium-substituted epitaxial films on (001)-oriented SrTiO3 and SrRuO3-buffered SrTiO3 substrates. Structural and morphological characterizations of the films are carried out using X-ray diffraction, atomic force microscopy, and scanning electron microscopy techniques. The films show textured growth and exhibit smooth morphology with root mean square roughness below 2.5 nm. Ferroelectric characteristics and memory retention in thin films are demonstrated using piezoresponse force microscopy. The thickness scaling of the switching voltage has been analyzed to validate the Kay–Dunn law for Sm-substituted BiFeO3 and compared with that of pure BiFeO3.

Chemical vapor deposition of entropy-stabilized rock-salt type oxide thin films

Here we present the first synthesis of a multi-cationic oxide (MgCoNiCuZn)O by pulsed liquid injection chemical vapor deposition. The synthesis is performed between 400 °C and 550 °C from five metal–organic precursors simultaneously solubilized in dimethoxyethane (DME). The microstructure of the material was studied using HRTEM with HAADF, SEM, EDS, XPS and XRD before and after annealing.

What lies beneath? Investigations of atomic force microscopy-based nano-machining to reveal sub-surface ferroelectric domain configurations in ultrathin films

Multiferroic materials, encompassing simultaneous ferroelectric and ferromagnetic polarization states, are enticing multi-state materials for memory scaling beyond existing technologies. Aurivillius phase B6TFMO (Bi6TixFeyMnzO18) is a unique room temperature multiferroic material that could ideally be suited to future production of revolutionary memory devices. As miniaturization of electronic devices continues, it is crucial to characterize ferroelectric domain configurations at very small (sub-10 nm) thickness. Direct liquid injection chemical vapor deposition allows for frontier development of ultrathin films at fundamental (close to unit cell) dimensions. However, layer-by-layer growth of ultrathin complex oxides is subject to the formation of surface contaminants and 2D islands and pits, which can obscure visualization of domain patterns using piezoresponse force microscopy (PFM). Herein, we apply force from a sufficiently stiff diamond cantilever while scanning over ultrathin films to perform atomic force microscopy (AFM)-based nano-machining of the surface layers. Subsequent lateral PFM imaging of sub-surface layers uncovers 45° orientated striped twin domains, entirely distinct from the randomly configured piezoresponse observed for the pristine film surface. Furthermore, our investigations indicate that these sub-surface domain structures persist along the in-plane directions throughout the film depth down to thicknesses of less than half of an Aurivillius phase unit cell (˂ 2.5 nm). Thus, AFM-based nano-machining in conjunction with PFM allows demonstration of stable in-plane ferroelectric domains at thicknesses lower than previously determined for multiferroic B6TFMO. These findings demonstrate the technological potential of Aurivillius phase B6TFMO for future miniaturized memory storage devices. Next-generation devices based on ultrathin multiferroic tunnel junctions are projected.

Deposition of SrCO3 thin film consisting of self-assembled bundles of nanostructures by a plasma-enhanced liquid injection chemical vapour deposition technique

Deposition of SrCO3 thin film consisting of self-assembled bundles of nanostructures by a plasma-enhanced liquid injection chemical vapour deposition technique

Investigation on structural and optical properties of porous SnO2 nanomaterial fabricated by direct liquid injection chemical vapour deposition technique

In the present study, Cassiterite SnO2 thin film synthesized by direct liquid injection chemical vapour deposition method. The surface morphology of the nanomaterial exhibited the rope-like structures with nanospheroid. Peak broadening in the prepared material is analyzed by Scherrer, modified Scherrer, Williamson-Hall, Size-strain and Halder-Wagner methods for investigation of crystallite size and intrinsic strain. The optical properties of the nanomaterial such as bandgap (Eg), absorption coefficient (α), skin depth (δ), optical density (Dopt), extinction coefficient (k), refractive index (n), and dielectric constants (εi and εr) are analyzed by using the UV–Visible transmittance and reflectance spectrum of the prepared SnO2 nanomaterial. The optical band gap of SnO2 based thin film was calculated by the Tauc plot and found to be 3.8 eV.

Effect of Chemical Treatment and Thermal Annealing in N2 Atmosphere on Copper Foil Surface for Graphene Growth by Direct-Liquid-Injection Chemical Vapor Deposition Process

Copper foils are widely used as a substrate for graphene grown by chemical vapor deposition method. The qualities of Cu foils can significantly affect the characters of resulting graphene films. Here, we systematically investigated the effects of chemical treatments and thermal annealing at high temperatures (890-950 °C) in N2 atmosphere. We then compared the graphene quality grown by direct liquid injection chemical vapor deposition (DLI-CVD) method with cyclohexane (C6H12) precursor on un-treated and treated Cu foil. We found that the chemical treatment conditions can improve surface morphology of the Cu foil. In addition, the annealing process at 920 °C for 10 min in N2 atmosphere can increase the grain size and lead to a favorable crystal orientation of (111) plane. Raman and microscopy analyses of the graphene film, show higher yields of monolayer graphene, while, at other annealing conditions and un-treated Cu foil, multilayer graphene is observed.

On the Use of Carbon Cables from Plastic Solvent Combinations of Polystyrene and Toluene in Carbon Nanotube Synthesis.

For every three people on the planet, there are approximately two Tonnes (Te) of plastic waste. We show that carbon recovery from polystyrene (PS) plastic is enhanced by the coaddition of solvents to grow carbon nanotubes (CNTs) by liquid injection chemical vapour deposition. Polystyrene was loaded up to 4 wt% in toluene and heated to 780 °C in the presence of a ferrocene catalyst and a hydrogen/argon carrier gas at a 1:19 ratio. High resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and Raman spectroscopy were used to identify multiwalled carbon nanotubes (MWCNTs). The PS addition in the range from 0 to 4 wt% showed improved quality and CNT homogeneity; Raman “Graphitic/Defective” (G/D) values increased from 1.9 to 2.3; mean CNT diameters increased from 43.0 to 49.2 nm; and maximum CNT yield increased from 11.37% to 14.31%. Since both the CNT diameters and the percentage yield increased following the addition of polystyrene, we conclude that carbon from PS contributes to the carbon within the MWCNTs. The electrical contact resistance of acid-washed Bucky papers produced from each loading ranged from 2.2 to 4.4 Ohm, with no direct correlation to PS loading. Due to this narrow range, materials with different loadings were mixed to create the six wires of an Ethernet cable and tested using iPerf3; the cable achieved up- and down- link speeds of ~99.5 Mbps, i.e., comparable to Cu wire with the same dimensions (~99.5 Mbps). The lifecycle assessment (LCA) of CNT wire production was compared to copper wire production for a use case in a Boeing 747-400 over the lifespan of the aircraft. Due to their lightweight nature, the CNT wires decreased the CO2 footprint by 21 kTonnes (kTe) over the aircraft’s lifespan.

Morphological Characterization of Calcium Phosphate Particles Obtained by Pulsed-Injection Metal Organic Chemical Vapor Deposition

ABSTRACTAmorphous calcium phosphate particles were synthesized for the first time by the Pulsed Injection Chemical Vapor Deposition technique onto silicon wafers, using Trimethyl Phosphate and Calcium Lactate mixed in a methanol solution as the precursor. The particles were deposited at a substrate temperature of 500, 550, and 600 °C obtaining the best results at 500 °C in terms of nucleation, density, morphology, and Ca/P ratio. The functional groups and vibrational modes, elemental composition, and surface morphology, were studied using Fourier Transform Infrared Spectroscopy, Raman Spectroscopy, and X-ray Energy Dispersion Spectrometry, and Scanning Electron Microscopy, respectively. The presence of the phosphate group characteristic of calcium phosphate was also observed. Uniform growth of the microstructures as the growth time and the temperature of the substrate increases were also observed, together with agglomerates of calcium phosphate in microstructures of 10, 50, and 100 nm in diameter. In these calcium phosphate agglomerates, calcium and phosphorus presence were observed, which is an important feature due to the Ca/P ratio gives information regarding biocompatibility.

Direct liquid injection chemical vapor deposition of ZrO2 films from a heteroleptic Zr precursor: interplay between film characteristics and corrosion protection of stainless steel

The direct liquid injection chemical vapor deposition (DLI-CVD) of uniform and dense zirconium oxide (ZrO2) thin films applicable as corrosion protection coatings (CPCs) is reported. We present the entire development chain from the rational choice and thermal evaluation of the suitable heteroleptic precursor [Zr(OiPr)2(tbaoac)2] over the detailed DLI-CVD process design and finally benchmarking the CPC behavior using electrochemical impedance spectroscopy (EIS). For a thorough development of the growth process, the deposition temperature (Tdep) is varied in the range of 400 – 700 °C on Si(100) and stainless steel (AISI 304) substrates. Resulting thin films are thoroughly analyzed in terms of structure, composition, and morphology. Grazing incidence X-ray diffractometry (GIXRD) reveals an onset of crystallization at Tdep ≥ 500 °C yielding monoclinic and even cubic phase at low temperatures. At Tdep = 400 °C, isotropic growth of XRD amorphous material is shown to feature cubic crystalline domains at the interfacial region as revealed by electron diffraction. Corrosion results obtained through EIS measurements and further immersion tests revealed improved CPC characteristic for the 400 °C processed ZrO2 coatings compared to the ones deposited at Tdep ≥ 500 °C, yielding valuable insights into the correlation between growth parameter and CPC performance which are of high relevance for future exploration of CPCs.

Effect of pyrolysis temperature on the synthesis of high-quality MWCNTs by CVD method

Production of high-quality Multi-Walled Carbon Nano-Tubes (MWCNTs) is essential in some field, especially in medical and mechanical applications. This work illustrates the synthesis of high-quality (MWCNTs) by Injection Chemical Vapor Deposition (Inj-CVD) method using Ferrocene / Toluene solution as a carbon precursor and a catalyst. The effect of synthesis pyrolysis temperature, which has a pivot impact on the synthesis process, was investigated. The structure defects, impurities, thermal stability and sample morphology, as well as the mean diameters of the MWCNTs, were analyzed using Raman spectroscopy, thermal gravimetric analysis (TGA) and scanning electron microscope (SEM), respectively. The results revealed that a change in quality, mean diameter and purity were observed when the pyrolysis temperature varied between 700°C to 850°C. High-quality MWCNTs were observed by Raman spectroscopy at a pyrolysis temperature of 700°C with ID/IG = 0.2. While the outer and inner diameters were 25±6 nm and 7.8±1.5nm respectively, measured by Transmission Electron Microscope (TEM). The Inj-CVD shows an excellent control of the quality of the prepared MWCNTs by optimizing the synthesis temperature.

Effect of carbon nanotubes grown temperature on the fracture behavior of carbon fiber reinforced magnesium matrix composites: Interlaminar shear strength and tensile strength

The design of an interfacial structure is particularly important for load transfer in composites. In this paper, different amounts of carbon nanotubes (CNTs) were grafted onto the carbon fiber (CF) surface by adjusting grown temperature using injection chemical vapor deposition (ICVD). The prepared CF preform grafted with CNTs (CNTs-CF) were used to reinforce magnesium alloy by squeeze casting process. The microstructures were analyzed by means of optical microscope (OM) and scanning electron microscope (SEM), and the interlaminar shear strength (ILSS) and tensile strength of the composites were determined by double-notch shear test and tensile test. The results indicated that moderate ILSS was more conducive to improving the tensile properties of carbon fiber reinforced magnesium matrix (Cf/Mg) composites. Compared with Cf/Mg, the tensile strength of composite with CNTs increased by about 80%. For Cf/Mg composites grafted with CNTs, CNTs had the effects of delaying crack propagation and increasing energy consumption by the pull-out and bridging mechanism, which were the main reasons for improving the strength. The analysis of shear fracture surface showed that the crack propagation path can be optimized by adjusting the amounts of grafted CNTs. The presence of CNTs affects the stress distribution and consequently the crack initiation as well as the crack propagation.

On the role of carbon nanotubes addition in carbon fiber-reinforced magnesium matrix composites

Introducing carbon nanotubes (CNTs) to form a multiscale reinforcing structure is regarded as an unique approach to effectively improve the interface property of metal matrix composites. Curved CNTs were grafted onto the surface of the carbon fiber fabrics by injection chemical vapor deposition, and pieces of fabrics were further stitched into preform. Carbon fiber grafted with CNTs-reinforced magnesium matrix composites (CNTs-Cf/Mg) was prepared by squeeze casting. The influence of grafted CNTs on the interfacial microstructure and mechanical properties was investigated. The results showed that the carbon fiber preform grafted with CNTs was fully infiltrated with the melt matrix alloy. The larger Al8Mn5-phase particles were refined by grafted CNTs, and a transition layer of Al8Mn5/CNTs was formed on the surface of carbon fiber. Tensile strength and bending strength of the CNTs-Cf/Mg composite were significantly increased compared to the composite without grafted CNTs by 33% and 29%, respectively. The fracture morphologies confirmed that the enhanced plasticity of matrix alloy near the interface prevented obvious debonding after grafting CNTs on carbon fiber. The main operative mechanism by CNTs was attributed to optimized interface fracture behavior. This could be a very prominent method to adjust the interface structure and improve the properties of composites.

Chemically vapor deposited Eu3+:Y2O3 thin films as a material platform for quantum technologies

Rare earth ions hosted in solids are good candidates for quantum technologies due to their chemical stability and optical and spin transitions exhibiting long coherence lifetimes. While bulk oxide crystals are usually the preferred host material, the development of a scalable silicon-compatible thin film platform would be desirable. In this paper, we report on the growth of Y2(1−x)Eu2xO3 thin films on silicon in the full range of Eu3+ concentration by direct liquid injection chemical vapor deposition (CVD). Our sub-micrometer polycrystalline films with a strong-(111) texture were grown for all compositions into the bixbyite cubic phase. The variation of growth rates with temperature and flow indicated that deposition occurred through a mass-transport controlled regime. Optical assessment of the Eu-doped thin films showed inhomogeneous linewidths as narrow as 50 GHz and fluorescence lifetimes of 1 ms for the lowest concentrations. Finally, a spectral hole was successfully burned in a 200 nm-thin film with a 2% Eu doping leading to a homogeneous linewidth of 11 MHz. These values are still below those reported for bulk single crystals indicating that additional decoherence mechanisms exist in such nanometric films, which might be alleviated by further improvement of the crystalline quality. Nevertheless, these results pave the way to the use of CVD-grown Eu:Y2O3 thin films as a platform for integrated quantum devices.

Synthesis of MWCNT/PPY nanocomposite using oxidation polymerization method and its employment in sensing such as CO2 and humidity

This paper includes the synthesis of a composite of multiwall carbon nanotube (MWCNT) and conducting polymer polypyrrol (PPY) and its characterizations along with the applications direct liquid injection chemical vapour deposition (DLICVD) and oxidation polymerization method have been used for the synthesis of MWCNT and MWCNT/PPY nanocomposite respectively. MWCNT/PPY's thin film was prepared using the technique of spin coating and characterized by scanning electron microscope (SEM), transmission electron microscope (TEM), particle size analyzer and X-ray diffractometer (XRD). Raman spectroscopy has been used to observe the vibrational and rotational spectra of MWCNT and MWCNT/PPY nanocomposite. The optical bandgap and minimum crystallite size have been calculated and found to be 3.2 eV and 8.1 nm respectively. The synthesized MWCNT/PPY has been used for CO2 and humidity sensing at room temperature (300 K). The sensor response of thin-film towards CO2 was found to be 7.2 at 1000 ppm and minimum response and recovery time at 250 ppm were found to be 30 s and 37 s respectively. The sensitivity of thin-film towards humidity was found to be 41.33 kΩ/%RH. The theoretical calculation was also performed in support of experimental data.