Liquid 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.

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.

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.

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.

Crystallographically Controlled Synthesis of SnSe Nanowires: Potential in Resistive Memory Devices

AbstractHere the controlled growth of SnSe nanowires by a liquid injection chemical vapor deposition (CVD) method employing a distorted octahedral [SnCl4{nBuSe(CH2)3SenBu}] single‐source diselenoether precursor is reported. CVD with this single‐source precursor allows morphological and compositional control of the SnSex nanostructures formed, including the transformation of SnSe2 nanoflakes into SnSe nanowires and again to SnSe nanoflakes with increasing growth temperature. Significantly, highly crystalline SnSe nanowires with an orthorhombic Pnma 62 crystal structure can be controllably synthesized in two growth directions, either <011> or <100>. The ability to tune the growth direction of SnSe will have important implications for devices constructed using these nanocrystals. The SnSe nanowires with a <011> growth direction display a reversible polarity‐dependent memory switching ability, not previously reported for nanoscale SnSe. A resistive switching on/off ratio of 103 without the use of a current compliance limit is seen, illustrating the potential use of SnSe nanowires for low‐power nonvolatile memory applications.

Heteroleptic Tin(IV) Aminoalkoxides and Aminofluoroalkoxides as MOCVD Precursors for Undoped and F-Doped SnO2 Thin Films.

A series of asymmetric and potentially bidentate amino alcohols and amino fluoro alcohols (RNOH) having a different number of methyl/trifluoromethyl substituents at the α-carbon atom, [HOC(R1)(R2)CH2NMe2] (R1 = R2 = H (dmaeH); R1 = H, R2 = CH3 (dmapH); R1 = R2 = CH3 (dmampH); R1 = H, R2 = CF3 (F-dmapH); R1 = R2 = CF3 (F-dmampH)) have been used to develop new monomeric and heteroleptic tin(IV) amino(fluoro)alkoxides [Sn(OR)2(ORN)2] (R = Et, Pri, But). These new complexes, which were thoroughly characterized by spectroscopy (IR and multinuclei NMR (1H, 13C, 19F, and 119Sn)) as well as single-crystal X-ray studies on representative samples, were investigated for their thermal behavior to determine their suitability as MOCVD precursors for the deposition of metal oxide thin films. The two most suitable compounds, [Sn(OBut)2(dmamp)2] and [Sn(OBut)2(F-dmamp)2], were used in a direct liquid injection chemical vapor deposition (DLI-CVD) process to deposit undoped SnO2 and F-doped SnO2 thin films, respectively, on silicon and quartz substrates. Film growth rates at different temperatures (from 400 to 700 °C), film thickness, crystalline quality, and surface morphology were investigated. The films deposited on quartz showed high transparency (above 80%) in the visible region and low carbon contamination on the surface (11-13% from XPS), which could easily be removed completely with 2 min of Ar+ sputtering.

Self-supported Pt-doped ceria nanofilms directly investigated by transmission electron microscopy

In this study, we report a direct deposition of three-dimensional freestanding nanostructures of platinum-doped ceria films on holey carbon coated copper transmission electron microscopy (TEM) grid by direct liquid injection chemical vapor deposition (DLI-CVD). TEM was then directly performed on the pristine thin films, without any kind of mechanical or ion thinning. High-resolution TEM reveals that highly porous and crystallized layers were deposited over the whole membrane. The existence of platinum in the ceria grains was confirmed by Energy Dispersive X-ray Spectroscopy (EDS) and X-ray Photoelectron Spectroscopy (XPS). Moreover, the substitution of carbon membrane by Pt-CeO2 layer was highlighted by Electron Energy Loss Spectroscopy (EELS), showing that the Pt-CeO2 nanofilms are freestanding. These results are very promising and represent an important step for performing specific nanoscale TEM analyses necessary for the study of the growth mechanism of nanofilms on substrates.

Optimization of Carbon Nanotube-Coated Monolith by Direct Liquid Injection Chemical Vapor Deposition Based on Taguchi Method

Carbon nanotubes (CNTs) have the potential to act as a catalyst support in many sciences and engineering fields due to their outstanding properties. The CNT-coated monolith was synthesized over a highly active Ni catalyst using direct liquid injection chemical vapor deposition (CVD). The aim was to study the optimum condition for synthesizing CNT-coated monoliths. The Taguchi method with L9 (34) orthogonal array design was employed to optimize the experimental conditions of CNT-coated monoliths. The design response was the percentage of carbon yield expressed by the signal-to-noise (S/N) value. The parameters including the mass ratio of Ni to citric acid (Ni:CA) (A), the injection rate of carbon source (B), time of reaction (C), and operating temperature (D) were selected at three levels. The results showed that the optimum conditions for CNT-coated monolith were established at A1B2C1D2 and the most influential parameter was D followed by B, C, and A. The ANOVA analysis showed the design was significant with R-squared and standard deviation of the factorial model equal to 0.9982 and 0.22, respectively. A confirmation test was conducted to confirm the optimum condition with the actual values of the average percentage of carbon yield deviated 1.4% from the predicted ones. The CNT-coated monoliths were characterized by various techniques such as field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), and Raman spectroscopy.

Magnetic-field-induced ferroelectric domain dynamics and in-plane polarization in odd and mixed layered Aurivillius structures

Herein, we conclusively discovered the role of “2D” odd/mixed, layered Aurivillius structures in generating coupled order parameters by directly visualizing magnetic-field-induced ferroelectric switching. We developed a novel sequence liquid injection-chemical vapor deposition process to fabricate atomistically controlled layer-by-layer genuine multiferroic Bi6Ti2.9Fe1.5Mn0.6O18 and Bi6Ti2.7Fe1.5Mn0.8O18 thin films. Ferromagnetic signature (MS = 13.79 emu/cc, HC = 9 mT at 300 K, and MR = 8 emu/cc) was generated for Bi6Ti2.9Fe1.5Mn0.6O18 thin films; however, no response was observed for mixed m = 5/6 intergrowths in Bi6Ti2.7Fe1.5Mn0.8O18 films. In-plane PR with magnetic (Fe/Ti)/conducting (Au/Ti) for Bi6Ti2.9Fe1.5Mn0.6O18 thin films is less (±23.66–24.69 μC/cm2) than the mixed m = 5/6 Bi6Ti2.7Fe1.5Mn0.8O18 layer structure (±57.42–67.94 μC/cm2). High leakage current for Fe/Ti interdigital capacitors (IDCs) compared to Au/Ti IDCs samples confirms Au/Ti IDCs’ suitability for ferroelectric industry. High ferro-paraelectric transition (Tc = 850 K), excellent in-plane polarization with negligible fatigue (9% after 1010 switching cycles), and coupled magnetoelectric (ME) (10% in-plane and 13% out-of-plane) orders provide an important contribution in a high-temperature fatigue free nonvolatile in-plane FeRAM, 4-state logics, and ME sensors. This article is being retracted effective 16 November 2020.