Spray pyrolysis is a popular method for the low-cost synthesis of oxides and other compounds in thin-film form. Here, we discuss several nuances of using this method for ternary and quaternary compounds. Specifically, we outline how precursor solubility and thermal decomposition, as well as desorption of intermediate species from the sample surface govern the spray pyrolysis growth process. We demonstrate how the stoichiometry transfer from solution to film can be affected in selected test cases. We present real-time optical growth measurements of the behaviour of individual Cu, Cr, Zn, and Sn precursors, as well as post-growth analysis of film composition by X-ray photoelectron spectroscopy for ternary transparent conducting oxides (TCOs; p-type: CuxCrO2, SnTiOx; and n-type: a-ZnSnO3). We illustrate how several steps of spray pyrolysis affect the stoichiometry transfer from the solution to the ternary thin film. Using binary Cu2O as a test case, we also show how the choice of instrument geometry and nozzle type can affect film homogeneity. All materials discussed have been chosen to highlight potential difficulties of the spray pyrolysis process of ternary, quaternary, or even more complex oxides, and the mechanisms should be considered for other materials as well. We therefore also provide an extensive overview of suitable precursor salts with similar expected properties as used in this experimental work to guide future ternary oxide studies.

The optical anisotropy of pristine and reduced single crystalline (010) orientated [Formula: see text] is presented. The reduction of [Formula: see text] is complex due to the abundance of V-O phases, strong dependence on the reducing conditions and multitude of reduction pathways. Different phases close in stoichiometry can exhibit drastically different electronic and optical properties. Reflectance anisotropy spectroscopy (RAS) provides a non-destructive optical probe that can be employed in real-time to monitor changes in thin films. Pristine [Formula: see text](010) exhibits strong anisotropy with significant features beyond the optical bandgap of 2.5 eV. Axially resolved optical constants, extracted using ellipsometry, facilitate the calculation of the RAS which is in excellent agreement with the experimental data. Vacuum annealing has been performed at four different temperatures and X-ray Diffraction and RAS have been conducted after each anneal. Depending on the anneal temperature, different phases are introduced into the [Formula: see text] crystal including [Formula: see text], [Formula: see text] and [Formula: see text]. Spectral features of each of these phases are identified. [Formula: see text] is understood in terms of the axially resolved optical constants from the literature, while isotropic [Formula: see text] modifies the total reflection once it undergoes its semiconductor-to-metal phase transition at 340 K. This understanding of the optical response of the ideal single crystal facilitates applying RAS to monitor the growth and changes of [Formula: see text] thin films in real time.

In this paper, the local bonding structure in amorphous zinc tin oxide (a-ZTO) is probed using a combination of XANES and EXAFS techniques at the Zn and Sn K-edges to gain insight into charge carrier generation in the material. a-ZTO is prepared using two growth methods; spray pyrolysis and magnetron sputtering. It is seen that a-ZTO grown by magnetron sputtering shows no changes in the chemical environment as the cation ratio is varied; meanwhile, XANES analysis of spray pyrolysis grown samples shows alterations to spectra likely due to the effects caused by different precursors. Although a slight shift in Sn-O bond length is visible between magnetron sputtered and spray grown samples, no correlation could be discerned between bond length and variation in cation ratio. It is concluded that a-ZTO, while amorphous over longer ranges, is locally composed of ZnO and SnO2 "building blocks". An alteration in the cation ratio changes the hybridization at the conduction band minimum, resulting in the observed variation in the mobility, charge carrier concentration, and bandgap.

High-quality epitaxial p-type V2O3 thin films have been synthesized by spray pyrolysis. The films exhibited excellent electrical performance, with measurable mobility and high carrier concentration. The conductivity of the films varied between 115 and 1079 Scm−1 while the optical transparency of the films ranged from 32 to 65% in the visible region. The observed limitations in thinner films’ mobility were attributed to the nanosized granular structure and the presence of two preferred growth orientations. The 60 nm thick V2O3 film demonstrated a highly competitive transparency-conductivity figure of merit compared to the state-of-the-art.

In this study, CuCl2 nanoparticles (NPs) synthesised via pulsed laser ablation in liquid (PLAL) were successfully employed to simultaneously detect glutamine and ammonia, with a limit of detection of 20 nM and up to 1500 ppm, respectively. These NPs hold potential for non-invasive diagnosis and monitoring of various health conditions using urine and sweat samples. The sensing mechanism relied on the plasmon peaks of CuCl2 NPs in the UV range (at 300, 363, and 423 nm), which were used to correlate the levels of glutamine and ammonia concentration with the absorbance. Quasi-spherical CuO and pyramidal CuCl2 NPs were synthesised through laser ablation of Cu powder in liquid IPA and IPA-HCl, respectively. CuCl2 NPs displayed higher ablation efficiency, higher optical absorbance (20-fold), and an 8400-fold increase in colloidal conductivity (0.0005 vs 4.2 mS/cm) compared to CuO NPs. The NP size distribution ranged broadly from 10 nm to less than 100 nm. XPS analysis revealed that ablation in pure IPA resulted in oxidized Cu NPs, while ablation in IPA-HCl liquid medium (12 nM HCl) led to the formation of a combination of metallic copper and CuCl2 NPs that were more conductive and had higher optical absorbance than their oxidized counterparts.

PorosityPorosity in copper filters is sensitive to powder type and space holder material in addition to fabrication processing conditions. This study is focused on the use of two different copper powderCopper powder types (spherical and dendritic) to produce air flow filtersAir flow filtration. The hydraulic pressing method was used to produce copper filters under varying pressure with different spacer (polyvinyl alcohol (PVA)) concentrations. Following compaction, the samples were thermally sintered in two segments at 200 °C and 750 °C. The morphologyMorphology, porosityPorosity, and mechanical propertiesMechanical properties of the sintered samples were characterized. The morphological analysis demonstrated better consolidation and overlapping of copper powderCopper powder particles in samples with a higher weight percentage of the spacer material (PVA). The highest porosityPorosity was achieved in the sample produced using dendritic copper powderCopper powder mixed with the highest weight percentage of PVA (3

The concentration of biomolecules such as trypsin and ammonia in bodily fluids are indicators of health conditions including pancreatic diseases and acute liver failure respectively. The maximum UV-Visible intensity and wavelength shifts of Mg-Cu bimetallic oxide nanoparticles (BNPs) were found to be proportional to changes in trypsin and ammonia concentration. The BNPs could selectively detect trypsin in tap water containing ions, ammonia, and glutamine at concentrations as low as 0.0003%v/v. The synthesis of Mg-Cu BNPs was accomplished by ablating a mixture of Mg and Cu powders and Mg and Cu colloids using a Nd:YAG 1064 nm laser in isopropanol alcohol and HCl. The BNPs demonstrated higher optical absorbance intensity in the UV-Visible range compared to their monometallic constituents, making them more suitable for use in biochemical sensing of trypsin and ammonia. The BNPs exhibited a massive 730-fold increase in electrical conductivity compared to monometallic Mg nanoparticles (0.001 mS/cm vs. 0.73 mS/cm). Field emission scanning electron microscopy was used to visualize the NP morphologies, revealing pyramidal and quasi-spherical BNPs with diameters as small as 5 nm.

Ferrite oxides, specifically spinel ferrites, are an interesting material class for a variety of applications. For spintronic devices, their stoichiometry, crystal quality, and even more importantly interface sharpness are of crucial importance. This chapter will review the use of molecular beam epitaxy (MBE) and plasma-assisted MBE to grow high-quality ferrites. We will show that with proper use of in situ growth monitoring, nucleation layers, and strain-reducing buffer layers, the stoichiometry of mixed ferrites can be controlled over a wide range in a precise matter. MBE provides control over thin film growth to the level of individual atomic layers, allowing the technique to grow not only high-quality interfaces for a specific device but also to grow ferrite superlattices and matching layers to change the magnetic properties of the ferrites.

Selective laser sintering (SLS) of copper components manufactured via powder metallurgy is widely studied due to minimal material wastage. However, copper has poor optical absorption when exposed to infrared (IR) lasers, such as in laser-based additive manufacturing or laser surface processing. To address this issue, an innovative approach to enhance the optical absorption of copper powders during infrared laser sintering is presented in this study. Carbon nanotubes (CNTs) have several unique properties, including their high surface area, plasmonic response, excellent conductivity, and optical absorption properties. CNTs were mixed with copper powders at different weight percentages using an acoustic method. The resulting Cu-CNT compositions were fabricated into pellets. The Box-Behnken Design of Experiments methodology was used to optimize the IR laser processing conditions for sintering. Spectroscopic analysis was conducted to evaluate the reflection and thermal absorption of the IR wavelengths by the Cu-CNT composites. Density and hardness measurements were taken for the laser-sintered Cu-CNT pellets. The coating of copper powders with CNTs demonstrated enhanced optical absorption and correspondingly reduced reflection. Due to the enhanced optical absorption, increased control and sensitivity of the laser sintering process was achieved, which enabled improvement in the mechanical properties of strength, hardness, and density, while also enabling control over the composite thermal expansion coefficient. A maximum average hardness of 66.5 HV was observed. Indentation test results of the samples revealed maximum tangential and radial stresses of 0.148 MPa and 0.058 Mpa, respectively.

Additive free conductive ink formulation via green techniques and its direct printing is critical for many appli-cations including smart electronics, solar cells, healthcare and electrochemical energy storage. The available printable ink generations are far away from ideal. This study reports the development of additive free silver (Ag) nano particle (NP) inks via flow-based Laser Ablation Synthesis in Solution (LASiS) system and Aerosol Jet printing. Examples of LASiS Ag NP printed tracks and patterns on unprocessed glass, rubber, and plastic sub-strates with spatial uniformity and high printing resolution are demonstrated. For thermally sintered Ag NP track, the resistivity decreased to 4.74 x 10(-6) omega m and conductivity improved to 2.11 x 10(5) S/m. The track resistance of asymptotic to 83 omega improved to asymptotic to 51 omega and the resistivity of 7.72 10(-6) omega m (conductivity: 1.29 x 10(5) S/m) improved to 4.74 x 10(-6) omega m. This work highlights that LASiS is a versatile, additive-free conductive ink formulation method for the scalable production of next generation printed electronic components and devices, using the emerging Aerosol Jet printing technology.

Silver nano-colloids have been generated via Laser Ablation Synthesis in Solution (LASiS) system. Nanoparticle formation with particle size below 50 nm in DI water was confirmed using UV-VIS spectroscopy, Dynamic Light Scattering (DLS) technique, and transmission electron microscopy (TEM). Supercapacitor structure, having dimension 11 mm x 10 mm, was successfully Aerosol Jet printed on an untreated polymer substrate using as produced LASiS silver nano-colloid.

Oxide semiconductors are penetrating into a wide range of energy, environmental, and electronic applications, possessing a potential to outrun currently employed semiconductors. However, an insufficient development of p-type oxides is a major obstacle against complete oxide electronics. Quite often oxide deposition is performed by the spray pyrolysis method, inexpensive to implement and therefore accessible to a large number of laboratories. Although, the complex growth chemistry and a lack of in situ monitoring during the synthesis process can complicate the growth optimization of multicomponent oxides. Here we present a concept of plasmonic, optical sensing that has been applied to spray pyrolysis oxide film growth monitoring for the first time. The proposed method utilizes a polarization based refractive index sensing platform using Au nanodimers as transducing elements. As a proof of concept, the changes in the refractive index of the grown film were extracted from individual Cu(acac)2 and Cr(acac)3 precursors in real time to reveal their thermal decomposition processes. Obtained activation energies give insight into the physical origin of the narrow temperature window for the synthesis of high performing p-type transparent conducting copper chromium oxide CuxCrO2. The versatility of the proposed method makes it effective in the growth rate monitoring of various oxides, exploring new candidate materials and optimizing the synthesis conditions for acquisition of high performing oxides synthesized by a high throughput cost-effective method.

This paper presents an examination of the production of copper air filters via the Hydraulic Pressing (HP) method. Processing conditions examined included powder particle type (spherical and dendritic), varying compaction pressures (635, 714, and 793 MPa) and different pore forming (polyvinyl alcohol (PVA)) concentrations (1, 2, and 3 wt.%). Following compaction, the samples were thermally sintered in a two stage sintering regime at 200 °C and 750 °C. The morphology, porosity, and mechanical properties of the sintered samples were characterised. Morphological analysis demonstrated better consolidation and overlapping of the copper powder particles in samples with a higher weight percentage of the PVA. Highest porosity was achieved in the sample produced using the dendritic copper powder mixed with highest weight percentage of PVA. As the samples were very porous, the hardness of the samples varied greatly. Samples prepared with spherical powders at high pressure demonstrated the highest hardness. The results in this study show that copper filters with 14%–26% porosity can effectively be produced using spherical and dendritic copper powders by controlling the compaction pressure and PVA concentration.

Conductive inks allow for low cost and scalable deposition of conductive tracks and patterns for printed electronics. Metal nanoparticle colloids are a novel form for producing conductive inks. Laser Ablation Synthesis in Solution (LASiS) is a “green” method for the production of metal nanoparticle colloids without the need for environmentally hazardous chemicals, however the method has typically been limited by its low production rates. This study reports on the generation of an additive free silver nanocolloid with maximized productivity using a flow-based LASiS system and its characterization using dynamic light scattering, UV–VIS, transmission electron microscopy and field emission scanning electron microscopy. The productivity of the LASiS silver nanoparticle (size ∼34 ± 5 nm) was ∼0.9 mg mL−1. While the flow-based system achieves high laser ablation rates in the mass of nanomaterial generated per unit time, the volume of liquid required for the flow leads to relatively low concentrations. Therefore, in this work, LASiS concentrated ink was formulated via a centrifugal method, which was then drop-cast and heat treated to produce a conductive silver layer. Centrifuging to concentrate the ink was shown to be a necessary step to achieve good results, with the lowest resistance across the drop-cast material of 60.2 Ω after annealing.

Defects introduced to the surface of Bi(111) break the translational symmetry and modify the surface states locally. We present a theoretical and experimental study of the 2D defects on the surface of Bi(111) and the states that they induce. Bi crystals cleaved in ultrahigh vacuum (UHV) at low temperature (110 K) and the resulting ion-etched surface are investigated by low-energy electron diffraction (LEED), X-ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy (UPS), and scanning tunneling microscopy (STM) as well as spectroscopy (STS) techniques in combination with density functional theory (DFT) calculations. STS measurements of cleaved Bi(111) reveal that a commonly observed bilayer step edge has a lower density of states (DOS) around the Fermi level as compared to the atomic-flat terrace. Following ion bombardment, the Bi(111) surface reveals anomalous behavior at both 110 and 300 K: Surface periodicity is observed by LEED, and a significant increase in the number of bilayer step edges and energetically unfavorable monolayer steps is observed by STM. It is suggested that the newly exposed monolayer steps and the type A bilayer step edges result in an increase to the surface Fermi density as evidenced by UPS measurements and the Kohn-Sham DOS. These states appear to be thermodynamically stable under UHV conditions.

Metal nanoparticles have unique chemical, physical, electrical, and optical properties that make them attractive for a wide range of applications in sensing, anti-fouling surfaces, medicine, and conductive inks. Pulsed Laser Ablation in Liquid (PLAL) is a green method of nanoparticle colloid production, capable of producing ligand-free nanoparticles in solution without the need for hazardous, environmentally unfriendly chemicals. Control of the process parameters can give control over the resulting colloid properties such as particle size distribution. In this work, silver (Ag) nanoparticles (NPs) with average particle size from 2.04 to 19.3 nm and copper (Cu) NPs with average particle size from 40 to 85.9 nm were produced by PLAL) technique.

In this work we present a comprehensive study of the domain structure of a nickel oxide single crystal grown by floating zone melting and suggest a correlation between point defects and the observed domain structure. The properties and structure of domains dictate the dynamics of resistive switching, water splitting and gas sensing, to name but a few. Investigating the correlation between point defects and domain structure can provide a deeper understanding of their formation and structure, which potentially allows one to tailor domain structure and the dynamics of the aforementioned applications. A range of inhomogeneities are observed by diffraction and microscopy techniques. X-ray and low-energy electron diffraction reveal domains on the submicron- and nanometer-scales, respectively. In turn, these domains are visualised by atomic force and scanning tunneling microscopy (STM), respectively. A comprehensive transmission electron microscopy (TEM) study reveals inhomogeneities ranging from domains of varying size, misorientation of domains, variation of the lattice constant and bending of lattice planes. X-ray photoelectron spectroscopy and electron energy-loss spectroscopy indicate the crystal is Ni deficient. Density functional theory calculations—considering the spatial and electronic disturbance induced by the favourable nickel vacancy—reveal a nanoscale distortion comparable to STM and TEM observations. The different inhomogeneities are understood in terms of the structural relaxation induced by ordering of nickel vacancies, which is predicted to be favourable.

NbO terminated Nb(110) and its oxidation are examined by scanning tunneling microscopy and spectroscopy (STS). The oxide structures are strongly influenced by the structural and electronic properties of the underlying NbO substrate. The NbO is terminated by one-dimensional few-nanometer nanocrystals, which form an ordered pattern. High-resolution STS measurements reveal that the nanocrystals and the regions between the nanocrystals exhibit different electronic characters. Low-dosage oxidation, sufficient for sub-monolayer coverage of the NbO, with subsequent UHV annealing results in the formation of resolved sub-nanometer clusters, positioned in-between the nanocrystals. Higher dosage oxidation results in the formation of a closed Nb 2 O 5−y layer, which is confirmed by X-ray photoelectron spectroscopy measurements. The pentoxide is amorphous at the atomic-scale. However, large scale (tens of nanometers) structures are observed with their symmetry matching that of the underlying nanocrystals.

Transparent conductive oxides (TCOs) are important materials for a wide range of optoelectronic devices. Amorphous zinc tin oxide (a-ZTO) is a TCO and one of the best nontoxic, low-cost replacements for more expensive amorphous indium-gallium-zinc oxide. Here, we employ spray pyrolysis (SP), an inexpensive and versatile chemical vapor deposition-based technique, to synthesize a-ZTO with an as-deposited conductivity of ≈300 S/cm-the highest value hitherto among the reported solution-processed films. Compositional analysis via X-ray photoelectron spectroscopy reveals a nonstoichiometric transfer of Zn and Sn from the dissolved precursors into the film, with the best electrical properties achieved at a film composition of xfilm = 0.38 ± 0.04 ((ZnO)x(SnO2)1-x (0 < x < 1)). The morphology of these films is compared to films synthesized by physical vapor deposition (PVD), and a strong correlation between morphology and electrical properties is revealed. The granular nature of the SP-grown films, which seems like a drawback at first glance, brings about the prospect of using a-ZTO in ink-jet-printed films from a nanoparticle suspension for the room-temperature deposition. Brief post-anneal cycles in N2 gas improve the conductivity of the films by means of grain boundary (GB) passivation.

We report on the synthesis of titanium suboxide films using a magnetron sputtering setup. The structure of the produced films is characterized using Raman spectroscopy and X-ray diffraction and electrical properties are measured by four-probe method. We demonstrate that depending on the oxidation rate of the growing films it is possible to produce polycrystalline αTiO, corundum and orthorhombic Ti2O3 or almost amorphous TiO2. We focus on the characterization of the two phases of Ti2O3 and show that their structure and electrical properties significantly differ from earlier results obtained for bulk crystals or epitaxial films. Our corundum-type Ti2O3 films have high electrical conductivity (compared to the bulk) and no metal-insulator phase transition: the material is locked in the metallic state. The conductivity of our orthorhombic Ti2O3 is lower compared to epitaxial films; this phase does not demonstrate any phase transitions as well.