Polycrystalline Targets Research Articles

High-resolution emission spectroscopy of W I lines: Comparing near-threshold sputtering of mono- and polycrystalline tungsten by Ar ions

This work presents the first experimental study on the near-threshold sputtering regime for monocrystalline low-index plane tungsten targets investigated using high-resolution emission spectroscopy. We analyzed the line shape emitted by sputtered atoms, which contains information on the angular and velocity distribution functions via Doppler broadening. Specifically, we report changes in the line profile of the resonant W I 498.4 nm transition during plasma exposure of polycrystalline and monocrystalline (100) and (111) tungsten targets at the linear plasma device PSI-2. Biasing the targets from −60 V to −100 V provided low-energy argon ions for near-threshold sputtering. The line shapes, measured along the angle of observation perpendicular to the normal of the sample, were significantly broader for the monocrystalline (100) and (111) compared to that of the polycrystalline target. In particular, the (111) target demonstrates a pronounced heart-shaped profile. The modeling captures this distribution via a ∝ cos(θ)exp(−bθ) function—θ is the polar angle—combined with a parameterized Thompson velocity distribution. Furthermore, comparing the experimental data to molecular dynamics simulations at 100 eV illustrates a reasonable agreement of the angular distribution function with the measurements.

Microstructure and characteristics of Zn and Mg-doped LiNbO3 materials for electrochromic devices

In this investigation, polycrystalline targets of lithium niobate (LN), zinc-doped lithium niobate (Zn:LN), and magnesium-doped lithium niobate (Mg:LN) were synthesized utilizing the Hot Isostatic Pressing (HIP) and Cold Isostatic Pressing (CIP) sintering technique. Subsequently, amorphous thin films of LN, Zn:LN, and Mg:LN and electrochromic devices were fabricated via radio frequency (RF) magnetron sputtering. Comprehensive characterization of the microstructure and optoelectronic properties of the targets, films and devices was conducted employing scanning electron microscopy, X-ray diffraction, spectrophotometry, atomic force microscopy, and an electrochemical workstation. Studies have shown that doping with zinc and magnesium enhances the sintering quality of ceramics, reducing lithium vacancies in polycrystalline lithium niobate ceramics. Zinc doping increases the resistance of lithium niobate, whereas magnesium doping introduces a secondary phase that decreases the resistance. The resistances of LN, Zn:LN, and Mg:LN polycrystalline ceramics are 8.35 GΩ, 9.80 GΩ, and 7.61 GΩ, respectively. The doping process refines the growth of the target and film particles, enhancing the microstructural quality. Notably, the ionic conductivity of the Mg:LN film escalates to 1.7 × 10−5 S/cm. Using doped lithium niobate thin films as electrolytes, the electrochromic devices showed a 38 % increase in coloration efficiency and a 46 % improvement in bleaching efficiency, significantly enhancing device performance.

The rebound law of micro-particle on amorphous alloys under high impact velocities

Compared to their crystalline counterparts, amorphous alloys due to disordered structures are expected to have higher elasticity of deformation. However, in this work, we use the micro-ballistic impact technique to show a smaller dynamic redound of micro-particles on a Zr-based amorphous alloy than that on its corresponding polycrystalline target. We find that the two alloys follow the same rebound law of micro-particle under low impact velocities, but with increasing impact velocity the amorphous alloy exhibits a faster decrease in rebound velocity of micro-particle. This lower rebound results from the easier activations of shear banding in glassy structures, thus contributing to more significant energy dissipation during the micro-particle impact. Further analyses imply that the amorphous alloys and their crystalline counterparts are more favorable in shock wave and projectile protection, respectively. This work is useful in the understanding of the dynamic elasticity and shock energy dissipation of amorphous alloys under micro-particle impacts.

Effect of thickness on the superconducting properties of the thin films of FeTe0.55Se0.45 deposited on YSZ substrates using Pulsed laser deposition (PLD) technique

We report the successful fabrication of thin films of thickness ∼26 nm, 59 nm, 76 nm, and 158 nm of the composition FeTe0.55Se0.45 on the (100)-oriented Yttria-stabilized zirconia (YSZ) substrate using the pulsed laser deposition (PLD) technique. The effect of thickness on the structure and superconducting properties of the thin films has been investigated. X-ray diffraction study reveals the growth of thin films along the c-axis. The temperature-dependent resistivity measurements confirm superconductivity in all the fabricated thin films, and the highest ∼ 16.2 K has been observed for the thin film of thickness ∼59 nm, which is higher than the corresponding value of the polycrystalline target sample. The superconducting parameters such as upper critical magnetic field coherence length thermally activated energy (TAE) U0, and vortex phase state have been measured by magnetotransport measurements near in the different applied magnetic fields up to 12 T. The TAE values determined from the conventional and modified thermally activated flux flow (TAFF) models are discussed and compared. A crossover from 2-dimensional (2D) vortex to 3-dimensional (3D) vortex behaviour has been observed. The vortex phase diagrams are used to observe the transition from the vortex liquid to the vortex glass state in the grown thin films. Moreover, magnetoresistance (MR) measurements show non-saturating linear magnetoresistance (LMR) in the high field region, indicating the presence of the possible topological state in the grown thin films. The values of magnetic field dependent transport critical current density, have been evaluated from the current-voltage (I-V) curves. Furthermore, the normalised pinning force density has been used to characterize the pinning processes using the Dew Hughes’ scaling rule which reveals that the grown thin films contain δl-surface pinning centers.

Thin Films Fabricated by Pulsed Laser Deposition for Electrocatalysis

Thin Films Fabricated by Pulsed Laser Deposition for Electrocatalysis

IGZO-decorated ZnO thin films and their application for gas sensing

In this study, indium–gallium–zinc oxide (IGZO)-decorated ZnO thin films were investigated through the change in IGZO deposition time for the detection of NO2 gas. The atomic layer deposited ZnO on interdigitated Au electrode alumina substrates are decorated with IGZO by controlling the deposition time. The IGZO (ZnO:Ga2O3:In2O3 = 1:1:1 mol. %) polycrystalline target was used for deposition and effect of deposition time was investigated. The sensor responses (Rgas/Rair) of 20.6, 39.3, and 57.1 and 45.2, 102.5, and 243.5 were obtained at 150 °C, 200 °C, and 250 °C and 25-ppm NO2 concentration for ZnO (Z1) and IGZO-decorated ZnO (Z3) films, respectively. The sensor response (Rgas/Rair) increased from ∼27 to 243.5 by decorating the ZnO film with IGZO for a 60-s sputtering time. The sensor recovery and response times of the IGZO-decorated ZnO/ZnO sensor increased, and the sensor selectivity to different gases was also evaluated.

Formation of In-=SUB=-2-=/SUB=-O-=SUB=-3-=/SUB=- films by magnetron sputtering on Al-=SUB=-2-=/SUB=-O-=SUB=-3-=/SUB=- (012) substrates

The results of studies of the microstructure and optical characteristics of In2O3 films deposited by the dc-magnetron sputtering of a polycrystalline target onto single-crystal sapphire substrates are summarized. The technological regimes of films preparation differed in the deposition time, substrate temperature, and the presence of additional heat treatment of film structures in air. It has been established that the optical refractive index of films deposited on a "cold" substrate increases in the direction from the substrate to the external interface. Heat treatment of the films eliminates the inhomogeneity of the refractive index and leads to a decrease in the band gap. The observed optical properties are explained by the thickness inhomogeneous microstructure of the films, which is formed during sputtering of a target with a relatively low mechanical strength. Keywords: In2O3 films, magnetron sputtering, Al2O3 substrates, refraction index, bandgap width.

Формирование плёнок In-=SUB=-2-=/SUB=-O-=SUB=-3-=/SUB=- методом магнетронного напыления на подложках Al-=SUB=-2-=/SUB=-O-=SUB=-3-=/SUB=- (012)

The results of studies of the microstructure and optical characteristics of In2O3 films deposited by the dc-magnetron sputtering of a polycrystalline target onto single-crystal sapphire substrates are summarized. The technological regimes of films preparation differed in the deposition time, substrate temperature, and the presence of additional heat treatment of film structures in air. It has been established that the optical refractive index of films deposited on a "cold" substrate increases in the direction from the substrate to the external interface. Heat treatment of the films eliminates the inhomogeneity of the refractive index and leads to a decrease in the band gap. The observed optical properties are explained by the thickness inhomogeneous microstructure of the films, which is formed during sputtering of a target with a relatively low mechanical strength.

Indium-gallium–zinc oxide (IGZO) thin-film gas sensors prepared via post-deposition high-pressure annealing for NO2 detection

Indium–gallium–zinc oxide (IGZO) thin films were prepared in a N2 environment by varying the annealing pressure and then tested for NO2 gas detection. These thin films, whose average thickness ranged between 5 and 100 nm, were deposited via the sputtering on alumina substrates equipped with interdigitated Au electrodes using an IGZO polycrystalline target (ZnO: Ga2O3:In2O3 = 1:1:1 mol%). The effects of annealing pressure and environment were investigated. A superior sensor response (S) was observed when increasing the annealing pressure; the prepared IGZO thin film showed an S of –800 at an operating temperature of 250 °C for 25 ppm NO2 gas. The recovery time decreased with increasing the annealing temperature. The sensor annealed at 400 °C at 3 atm showed superior selectivity to various gases and longtime stability of 60 days was attained. The role of the oxygen vacancies in the sensor performance was also investigated.

Sensing Properties of Indium-Gallium-Zinc-Oxide Thin Films under the Influence of Thickness and Annealing Ambient

In this study, indium-gallium-zinc-oxide (IGZO) thin films were investigated for detection of Nitrogen Dioxide (NO2) gas. IGZO films with a thickness range of 25–100 nm were deposited using IGZO (ZnO: Ga2O3:In2O3 = 1:1:1 mol.%) polycrystalline target on interdigitated Au electrode alumina substrates and annealed in different annealing atmosphere of Nitrogen (N2) and Oxygen (O2). The effects of the IGZO thickness and different annealing ambient on IGZO were investigated on sensing properties. The N2 ambient showed a superior response (S = Rgas/Rair) compared to O2 annealing by a factor of 2.3 times. In addition, the sensor response increases with film thickness up to 25 nm and decreases with an increase in thickness. The sensor showed a high response for the IGZO thin film (25 nm), which was 519 times that of the other sensors at 200 °C. The sensor recovery and response time improved, and the sensor selectivity was tested under different gases.

Dependence of the Electrophysical Characteristics of Metal–Ferroelectric–Semiconductor Structures on the Field-Electrode Material

Films of the composition Ba0.8Sr0.2TiO3 (BST 80/20) are synthesized on a silicon substrate by the method of the high-frequency sputtering of a polycrystalline target. The results of investigations of the film composition, the electrophysical properties of capacitor structures based on them, and the dependence of these properties on the material (Al, Cu, Ni, Cr) of the upper electrode are presented.

Experimental investigation of laser ablation of stone polycrystalline targets

We report the results of an experimental investigation of ablation of stone polycrystalline targets of complex multicomponent composition, which imitate the substance of asteroids. The targets were irradiated by nanosecond pulses of a neodymium laser at an energy density ΦL of up to 5 × 104 J cm−2. The experiments demonstrated the existence of two ablation regimes, with the boundary between them lying at ΦL ≈ 4000 J cm−2. The regime change is characterised by a change in the form of the dependence of the surface mass density of removed target material on the laser energy density and by the appearance of a minimum in the dependence of specific energy of destruction on ΦL. This is supposedly related to the passage from a one-dimensional plasma plume expansion to the three-dimensional one and the corresponding decrease in the efficiency of energy transfer from the laser beam to the target due to a lowering of laser-produced plasma density. Our experiments also showed the existence of a maximum in impulse coupling coefficient Cm as a function of laser energy density (Cm ≈ 6.3 × 10−5 N W−1 for ΦL = Φopt ≈ 25 J cm−2). Maxima were also recorded in the dependences of the ablation efficiency and average ablation flow velocity on ΦL. For ΦL > Φopt, the decrease in the function Cm(ΦL) turns out to be much steeper than for metals and polymer materials. The difference is supposedly due to the lower strength and lower plasticity of the polycrystalline stone targets.

Continuous ferrimagnetic Y3Fe5O12 layers on the ceramic PbZr0·45Ti0·55O3 substrates

For the first time, continuous layers of yttrium iron garnet (YIG, Y3Fe5O12) with a thickness of about 2 μm were synthesized on ferroelectric ceramic substrates based on lead titanate zirconate (PZT, PbZr0·45Ti0·55O3). The Y3Fe5O12 layer was deposited by ion-beam sputtering – deposition on PZT substrates of 400 μm thick by sputtering a polycrystalline target of the composition Y3Fe5O12 with a mixture of argon and oxygen ions. Due to preliminary planarization of the PZT surface with a TiO2 layer, a high-quality plane-parallel YIG/PZT interface was obtained, which is confirmed by scanning electron microscopy in combination with the focused ion beam technique. Atomic force microscopy showed that planarization makes it possible to achieve surface smoothness of 10 nm.The YIG/PZT heterostructures obtained in this work are potentially attractive for use in logic circuits based on low-scattering spin waves, memory elements, as well as electrically controlled microwave devices.

An affordable method to produce CuInS2 ‘mechano-targets’ for film deposition

We report on the room temperature, simple and cheap preparation by mechano-synthesis of polycrystalline targets of complex sulphide semiconductors, namely CuInS2 (CIS), to be used for film deposition in physical vacuum techniques such as PLD, sputtering or LT-PED. The sulphur (S)-based targets usually require expensive high pressure equipment to compensate the high S vapour pressure; nevertheless they are indispensable for the deposition of high band-gap semiconductor materials. The comparison of CIS films grown by mechano-synthesis and by commercial targets demonstrates similar material quality, making the mechano-synthesis a viable solution in the fabrication of high band-gap, S-based targets of complex chalcogenides.

Study of vortex glass-liquid transition in superconducting Fe(Te, Se) thin films on LaAlO3 substrates

Superconducting thin films of two different thicknesses have been fabricated on (100) LaAlO3 substrates using a polycrystalline target of composition Fe1.05Te0.50Se0.50 by the pulsed laser deposition technique. The onset of superconducting transition temperatures (TConset) at 0 T magnetic field of the grown thin films of thickness of ∼74 nm and ∼185 nm are ∼12.65 and 13.15 K, respectively. The upper critical field BC2(0) values have been calculated by the Ginzburg–Landau theory as well as by the Werthamer–Helfand–Hohenberg model, and the corresponding coherence lengths have been estimated. In the present work, the thermally activated energy (TAE) has been obtained using the conventional Arrhenius law as well as by a modified thermally activated flux flow (TAFF) theory. For both models, the TAEs of vortices show a crossover at a magnetic field of ∼2 T corresponding to the transition from the single vortex pinning regime to the collective vortex pinning regime. Based on the analysis of the field dependence of TAE, the planer/point defect dominating magnetic field regions have been identified. The analysis of the magnetotransport data with the modified TAFF model reveals the dominating three dimensional behavior of vortices for both thin films. Moreover, in the vortex phase diagram, a narrow vortex melting region and a vortex glass-liquid phase transition below BC2 have been observed for both of the grown thin films. Furthermore, the X-ray photoelectron spectroscopy results show that Fe is present in Fe2+ and Fe3+ chemical states in both thin films.

Reflection of hydrogen and deuterium atoms from the beryllium, carbon, tungsten surfaces

Particle reflection coefficients for scattering of hydrogen and deuterium atoms from amorphous beryllium, carbon and tungsten were obtained, which are of interest for thermonuclear reactor physics. For the case of deuterium scattering from tungsten the data were also calculated for polycrystalline and crystalline target. The calculations were carried out by two methods: by modeling the trajectories of the incident particles and by using the binary collision approximation. Interaction potentials between hydrogen and helium atoms and the selected materials were calculated in the scope of the density function theory using program DMol for choosing wave functions. The dependence of the reflection coefficient RN on the potential well depth was found. The results demonstrate a good agreement with the available experimental values.

Simulation of Particle Scattering at Amorphous and Polycrystalline Targets

A procedure for simulating the scattering of atomic particles at amorphous and crystalline targets is described in the binary collision approximation. The influence of thermal vibrations, choice of the potential, and the inclusion of inelastic energy losses are analyzed using the simulation of hydrogen-atom scattering at a tungsten surface as an example. The coefficients of reflection from crystalline, polycrystalline, and amorphous surfaces are compared.

Effect of Fe ion implantation on the thermoelectric properties and electronic structures of CoSb3 thin films.

In the present study, thin films of single-phase CoSb3 were deposited onto Si(100) substrates via pulsed laser deposition (PLD) method using a polycrystalline target of CoSb3. These films were implanted by 120 keV Fe-ions with three different fluences: 1 × 1015, 2.5 × 1015 and 5 × 1015 ions per cm2. All films were characterised by X-ray diffraction (XRD), Raman spectroscopy, atomic force microscopy (AFM), Rutherford backscattering (RBS) spectrometry and X-ray absorption spectroscopy (XAS). XRD data revealed that the ion implantation decreased the crystalline nature of these films, which are recovered after the rapid thermal annealing process. The Seebeck coefficient S vary with the fluences in the temperature range of 300 K to 420 K, and is found to be highest (i.e., 254 μV K−1) at 420 K for the film implanted with 1 × 1015 ions per cm2. The high S and low resistivity lead to the highest power factor for the film implanted with 1 × 1015 ions per cm2 (i.e., 700 μW m−1 K−2) at 420 K. The changing of the sign of S from negative for the pristine film to positive for the Fe-implanted samples confirm that the Fe ions are electrically active and act as electron acceptors by replacing the Co atoms. XAS measurements confirm that the Fe ions occupied the Co site in the cubic frame of the skutterudite and exist in the 3+ oxidation state in this structure.

Crystallization by laser annealing of amorphous SnO2 films on the Si (100) surface

Thin films of SnO2 were fabricated on Si wafer (100) substrates in a vacuum chamber at 10−5 Torr using the pulsed laser deposition technique. An excimer laser was used to ablate a SnO2 polycrystalline target and deposit thin films on a Si support which was maintained at 300 °C. The deposited amorphous films were analyzed using X-ray diffraction and scanning electron microscopy. To convert the films to crystalline form, two approaches were used: oven annealing and pulsed laser annealing. Both annealing techniques resulted in crystalline thin films of SnO2 in the rutile structure, with oven annealing resulting in higher quality crystalline films. Thickness of the as-deposited SnO2 film can determine crystalline phase of the annealed film.

Crystallographic orientation dependence of the sputtering yields of nickel and copper for 4-keV argon ions determined using polycrystalline targets

Abstract A novel approach for revealing the crystallographic orientation dependences of sputtering yields was developed; this approach used 3D surface profiling and the crystallographic orientation imaging of polycrystalline targets. The sputtering yields of Ni and Cu for normally incident 4-keV Ar+ ions were measured over practically all possible crystallographic orientations. They were found to be low around the directions parallel to the [0 0 1] and [1 0 1] axes and around the directions parallel to the ( 1 1 1 ¯ ) and (0 1 0) planes. The Onderdelinden model for the crystallographic orientation dependences of sputtering yields was extended such that it could include planar channeling. The crystallographic orientation dependence determined experimentally was in semi-quantitative agreement with the dependences calculated using the extended Onderdelinden model; this demonstrated that the non-channeling probability dominantly controls the sputtering yield.