Powder Target Research Articles

Production of Thin Pb<sub>x</sub>Sn<sub>1–x</sub>Te Films by “Hot Wall” Method for Creating IR-Photodetectors

Alloys of lead and tin telluride (PbxSn1–xTe) are materials with good thermoelectric properties, as well as semiconductors that can be used as long-wave infrared detectors. Polycrystalline telluride of PbxSn1–xTe (0.05 £ x £ 0.80) alloys has been synthesized by direct fusion technique. Thin films of these materials have been obtained by the hot wall method depositing Сorning 7059 on glass substrates at Tsub = (200–350) oC and vacuum of about 10–5 Torr. The microstructure of the films has been investigated by XRD, SEM and EDX methods. The X-ray spectra of thin films have been in satisfactorily agreement with the spectra of the powder target and indicated the absence of binary phases. The films have shown a natural cubic crystalline structure. While increasing the lead content, the unit cell parameter of the crystal also increases. The established linear relationship between the unit cell parameter and the elemental composition corresponds to Vegard's law. The SEM analysis has shown that the films are polycrystalline, have a columnar structure, are tightly packed and have good mechanical adhesion. The grain size depends on the chemical composition and temperature of the substrate. The electrical measurements have shown that the grown films are non-degenerate semiconductors of p-type conductivity. The conductivity of the films was in the range of σ = (3 × 101)–(1 × 104) Ω–1×cm–1. An increase of lead concentration leads to a decrease in electrical conductivity. Hall mobility in the grown thin films increases in the range of changes in the lead content from ~10 to ~23 at. %, and decreases with a further increase to ~33 at. %. At the same time, the strongest dependence of the decrease in mobility on an increase in temperature increase is observed for films with a high lead content and is explained by the predominant scattering of charge carriers by vibrations of the crystal lattice. For a sample with an average lead concentration, an alternative effect of two scattering mechanisms is observed in the temperature dependence of the mobility: by impurity ions and by phonons.

Charge and elemental composition of plasma generated by sputtering of powder target from amorphous boron

One of the effective and widespread methods of surface hardening of metal products is an ion-plasma saturation of the surface of machine parts and mechanisms with various elements (nitrogen, oxygen, carbon). Less investigated method is the process of ion-plasma saturation of the metals and alloys surface with boron. The purpose of the present work is to develop a method for the formation and study of parameters (electron temperature, plasma potential and concentration), elemental and charge composition of plasma generated at sputtering of a target from amorphous boron powder. To achieve the stated goal, a discharge system with a hot anode made of powder boron, as well as a pulse arc evaporator with a hot cathode made of sintered boron powder, was developed, designed, created and tested. Charge and elemental composition of boron-containing plasma generated during powder target sputtering from amorphous boron are defined by optical spectrometry method. It is shown that the generated plasma contains mainly neutral atoms and single-charge boron ions, as well as iron, silicon, copper and argon particles.

Deposition of boron films using a discharge system with a hot boron anode

This work describes a discharge system for heating and evaporation of a boron powder target based on a non-self-sustained arc discharge with a filament, a hollow cathode and a hot combined anode. The measurements of the current-voltage characteristics of the discharge with a hot anode and the dependence of the anode temperature on the discharge parameters are presented. The modes of deposition of boron films have been determined.

(Invited) Halide Perovskite Thin Films via Alternate Laser Deposition: Change in the Physical Properties with the Layered Structures

We have formed methylammonium lead iodide (MAPbI3) perovskite by alternating irradiation of PbI2 and CH3NH3I (MAI) with an infrared laser in an ultra-high vacuum to elucidate the growth mechanism and realize structural control of MAPbI3 [1]. In this study, we found that MAPbI3 contains both tetragonal and orthorhombic phases, and the ratio of these phases systematically changes depending on the thickness of alternating layers of PbI2 film.In the sample preparation, the PbI2 and MAI powder targets were alternately irradiated with an infrared laser (λ = 808 nm) to convert them into molecular beams, and then alternately deposited on a synthetic fused silica substrate at room temperature. The deposition rate of PbI2 was controlled to be about 0.1 nm/s using a quartz crystal microbalance thickness monitor. The deposition amount of MAI was adjusted by changing the deposition time while the evaporation pressure was fixed at 4×10-4 Pa. Four different multilayer samples consisting of [PbI2/MAI] × n (n = 1, 2, 5, 10) were prepared under the condition that the total thickness of PbI2 was 300 nm.By analyzing the crystal structures by X-ray diffraction measurements, the prepared samples were found to have the following two unique features: (1) In the samples with n = 1, unreacted PbI2 was present in addition to MAPbI3, while in the samples with n = 2, 5, and 10, only MAPbI3 was observed, indicating a complete solid-phase reaction. (2) The full width at half maximum and peak position of the diffraction peak for MAPbI3 at 2θ = 14.0° ~ 14.1° were different among the samples, and thus we performed the analysis by peak separation. As a result, it was determined that the tetragonal (002) and orthorhombic (020) diffraction peaks were included.Defining r tetra and r ortho as the ratio of the tetragonal and orthorhombic diffraction peak areas to the total peak area, it was found that r tetra : r ortho changes significantly with the thickness of the PbI2 layer. Specifically, r tetra : r ortho =[0.64 : 0.36], [0.39 : 0.61], [0.20 : 0.80], and [0.25 : 0.75] for n =1, 2, 5, and 10, respectively. It is noteworthy that the orthorhombic MAPbI3, which usually appears below 161 K due to the phase transition [2], is contained in the MAPbI3 film formed at room temperature, and that the mixing ratio of tetragonal and orthorhombic phases varies systematically with the thickness of the alternating deposited PbI2 films.[1] K. Kawashima et al., Sci. and Tech. of Adv. Mater. 18, 307 (2017).[2] N. Onoda-Yamamuro et al., J. Phys. Chem. Solids 51, 1383 (1990).

Effect of deposition time on the photocatalytic activity of sputtered mixed ZnO–SnO2 thin films under visible light irradiation

In this work, transparent conducting ZnO–SnO2 oxide thin films have been prepared on glass substrates by radio-frequency RF magnetron sputtering at different deposition times dt using powder targets. The structural, optical, electrical and photocatalytic properties of the deposited films were studied based on the increased deposition time (1 h, 2 h, 3 h and 4 h). X-ray diffraction (XRD) results showed an amorphous aspect for all sputtered layers, while the Raman study proved the presence of characteristic modes of spinel phase Zn2SnO4. UV visible Spectroscopy results revealed good homogeneity and high transparency of the films within the visible wavelength. The estimated values of the optical band gap decreased from 3.77 to 3.59 eV as deposition time increased. The films’ thickness ranged from 60 to 400 nm. Hall effect measurements exhibited that the conduction of all films was n-type and electrons represented the majority of free charge carriers. The lowest electrical resistivity, highest mobility and highest charge carrier concentration were obtained for dt = 1 h. The test of the catalytic efficiency of these ZnO–SnO2 thin films indicated that the best degradation of the methylene blue (MB) dye under solar irradiation was obtained for 210 min.

Structure, Optical and Electrical Properties of the High Doped ZnO Thin Films Deposited By RF Magnetron Sputtering of Powder Target in Methane Ambient

The ZnO thin films were deposited by RF-magnetron sputtering of ZnO powder target using pure argon, argon with hydrogen and argon with methane as reactive gas. Surface morphology and crystalline structure of the films were studied by SEM, XRD and XRR techniques. Chemical composition and optical properties were investigated by SIMS, Raman scattering spectroscopy (RSS), PL spectroscopy and spectral ellipsometry. Electrical measurements were performed on the ZnO films deposited on SiO2-Si and silicon wafers n- and p-type with Ni contacts by TLM, IV, CV characteristics, admittance spectroscopy, Van der Pauw and Hall methods. It was found that growth morphology, crystalline structure, optical and electrical properties of the films are strongly affected by adding methane to argon during the deposition process. Adding of methane resulted in a destruction of hexagonal phase texture and considerable increase a size of ZnO nanocrystallites (from 50 nm for argon to 200 nm for argon/methane working gas). SIMS measurements demonstrated that methane promoted hydrogen incorporation into the ZnO film that was more than an order of magnitude larger in comparison with adding molecular hydrogen in the gas mixture at the same concentration. Adding of methane resulted in a high energy shift of near band edge ultraviolet photoluminescence band, quenching of deep level emission in the visible spectral range and increase of optical band gap from 3.24 to 3.45 eV. The strongest effect of methane has been found for electrical resistivity that reduced by 3 orders of magnitude in comparison with films deposited in pure argon. Additionally, electrical conductance of the ZnO film deposited at high methane concentration does not depend on measurement temperature. Hall method with combination with Van der Pauw resistivity measurements shows: strong n-type doping of the film; donor concentration more than 1020 cm-3 slightly depending on methane concentration; maximum electron mobility about 7 cm2/V s. The direct comparison of resistivity and donor concentration of the films deposited using methane and molecular hydrogen as doping precursors has demonstrated that doping efficiency of methane is about an order of magnitude larger than that of molecular hydrogen under similar deposition conditions. On the other hand, methane addition in working gas resulted in an intensity decrease of the E2L (100 cm-1) and E2H (438 cm-1) lines in the RSS that can be associated with some disturbance of the ZnO structure. Additionally a peak at 71 cm-1 was observed in some films that can be related to the metallic Zn. The possible mechanisms of the ZnO film formation, nature of the doping and electron transport mechanisms will be discussed.

Nitride formation during reactive sputter deposition of multi-principal element alloys in argon/nitrogen mixtures

Nitrides based on multi-principal element alloys have been deposited by reactive magnetron sputtering from powder targets. All deposited nitrides were based on alloys of which the majority of the constituent metals have a low chemical affinity to molecular nitrogen (Co, Cu, Fe, Ni, Mn, and Zn). Some more reactive metals (Al, Cr, Ti, Mo, and V) were also added. The nitrogen incorporation in these alloys was investigated based on two different approaches. The incorporation efficiency is calculated based on the chemical composition of the deposited layer, and the metal flux towards the substrate. The calculations are based on a previous published model to simulate the reactive magnetron sputtering process. The observed trends are compared with results obtained from (energy resolved) mass spectrometry measurements. Both methods proof that the nitrogen incorporation is dominated by sputtered nitrogen from the (partially) poisoned target. The composition weighted electronegativity average of the alloy constituent elements is used to asses the target poisoning level. It is shown that this electronegativity average correlates with the incorporation efficiency. The nitrogen incorporated in these alloys is mainly atomic nitrogen which affects the texture development. In contrast to nitrides based on highly reactive metals such as Ti which exhibit a cubic 〈111〉 fiber texture, a cubic 〈001〉 fiber texture is observed for the studied alloys.

Correlating the properties of RF sputtered ZnO nanocrystalline films deposited using sintered and powder targets

ZnO thin films were deposited by RF magnetron sputtering using commercial sintered and in-house made powder targets. The structural, optical, chemical composition and surface morphology of the ZnO thin films were characterized by X-ray diffraction (XRD), Atomic Force Microscopy (AFM), Field Emission Scanning Electron Microscopy (FESEM), X-ray Photoelectron Spectroscopy (XPS), UV–Visible spectroscopy, Photoluminescence (PL) and Raman Spectroscopy. XRD data established that both films were c-axis oriented and the appearance of E2H mode in Raman spectra confirmed the hexagonal wurtzite structure of the films. AFM micrographs revealed the homogeneity and nanocrystalline nature of the films. XPS and EDX studies confirmed that the films contained only Zn and O elements. Both the films showed superior optical properties and > 90% transmittance in the visible region. The results conclude that powder targets can be used to achieve complex/mixed metal oxide films having optical/electronic quality thereby overcoming the limitation of choice as in the case of commercial targets.

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ZnO thin films were deposited by RF magnetron sputtering using commercial sintered and in-house made powder targets. The structural, optical, chemical composition and surface morphology of the ZnO thin films were characterized by X-ray diffraction (XRD), Atomic Force Microscopy (AFM), Field Emission Scanning Electron Microscopy (FESEM), X-ray Photoelectron Spectroscopy (XPS), UV–Visible spectroscopy, Photoluminescence (PL) and Raman Spectroscopy. XRD data established that both films were c-axis oriented and the appearance of E2H mode in Raman spectra confirmed the hexagonal wurtzite structure of the films. AFM micrographs revealed the homogeneity and nanocrystalline nature of the films. XPS and EDX studies confirmed that the films contained only Zn and O elements. Both the films showed superior optical properties and > 90% transmittance in the visible region. The results conclude that powder targets can be used to achieve complex/mixed metal oxide films having optical/electronic quality thereby overcoming the limitation of choice as in the case of commercial targets.

Development of sputtered nitrogen-doped Li1+xAlxGe2-x(PO4)3 thin films for solid state batteries

Nitrogen-doped Li1+xAlxGe2-x(PO4)3 (LAGP) thin films were prepared by magnetron sputtering in a mixture of Ar + N2 using an LAGP powder target. The as-deposited films were amorphous, but could be crystallised into the NASICON LAGP phase after annealing at temperatures above 550 °C. The introduction of nitrogen to the sputtering gas has two effects on the deposited films; incorporation of a low concentration of nitrogen into the LAGP phase but also reduction of the rate of deposition. The former leads to improvements in Li ion conductivity whereas the latter can cause porosity and discontinuities in the films and limits their application in solid state devices. Up to 23% nitrogen in the sputtering gas the first effect is dominant and the total ionic conductivity improves without introducing morphological defects. However if the nitrogen content is increased further, the porosity decreases the measured conductivity. Optimised nitrogen doping in the sputtered LAGP films results in ionic conductivities as high as 2.3 × 10−4 S cm−1 in films only 1 μm thick (2.7 times higher than undoped LAGP films) and activation energies below 0.38 eV.

ZnO:Al thin films from (Al2O3)x(ZnO)(1-x) powder targets by magnetron sputtering

In the present work we prepared Aluminum doped Zinc Oxide (AZO) thin films from powder targets. Various concentrations (W/W percentages) of Al2O3 such as1%, 2%, 3%, 4%, 5%, 6%, 7% and 8% were mixed in ZnO powder and made in the form of a 3 inch disc target. These ceramic targets are sputtered in RF magnetron sputtering unit for the deposition of AZO thin films. Optical and electrical properties are analyzed to get an optimized percentage of mixing for achieving high transparency and low resistivity. At Al2O3 percentage of 3% there is a considerable decrement in the resistivity, and at 7% there is a considerable decrease in the optical transmittance. Mobility and carrier concentration are increasing with Al2O3 percentage. Bandgap of the films is observed to be decreasing with increasing the Al2O3 percentage.

Influence of magnesium and strontium substitutions in the structure of hydroxyapatite lattice on the deposition rate and properties of the CaP coatings formed via RF-sputtering of the powder targets

This work is dedicated to studying of the properties of the calcium phosphate (CaP) coatings deposited on Ti substrates by radio-frequency magnetron sputtering (RFMS) of three hydroxyapatite-based powder targets: pure hydroxyapatite (HA), Mg-substituted HA (Mg-HA, Mg = 0.93 ± 0.13 at.%) and Sr-substituted HA (Sr-HA, Sr ∼ 0.47 at.%). The influence of ionic substitutions in the structure of the sputtered targets on the surface morphology, physicochemical properties of the coatings and their wettability were studied. It is revealed that Mg and Sr ionic substitutions in the crystal lattice of HA at these concentrations don’t affect deposition rate, however, it influences morphology, wettability and elemental and phase composition of deposited coatings.

Effect of the Grain Size of Powder Targets on the Spectra of Parametric X-Ray Radiation of Relativistic Electrons

The results of measurements of the dependence of the full width at half-maximum and the relative intensity of spectral peaks of parametric X-ray radiation (PXR) for various crystallographic planes on the grain size of a micrometer diamond powder are presented.

The potential of transparent sputtered NaI:Tm[formula omitted], CaBr[formula omitted]:Tm[formula omitted], and CaI[formula omitted]:Tm[formula omitted] thin films as luminescent solar concentrators

The parameters governing the performance of a luminescent solar concentrator (LSC) are determined for sputtered thin-films of NaI:Tm2+, CaBr2:Tm2+, and CaI2:Tm2+. These parameters are determined by using six gradient thin film material libraries, combinatorially sputtered from metallic and pressed powder targets. These films show strong 4f13→4f12d1 absorption of maximally 752cm−1 at.%−1 for NaI:Tm2+, 31cm−1 at.%−1 for CaBr2:Tm2+, and 473cm−1 at.%−1 for CaI2:Tm2+. This absorption covers the entire visible spectrum and does not overlap with the infrared 4f-4f emission at 1140nm. Decay measurements are used to estimate the quantum yields of the thin-films. These quantum yields can be as high as 44% for NaI:Tm2+, when doped with 0.3at.% Tm. Even at doping percentages as low as 0.3at.%, the films appear to show luminescence quenching. The concentration-dependent absorption and quantum yield are combined with the index of refraction, resolved from transmission measurements, to simulate the optical efficiency of a thin film Tm2+-doped halide LSC. These simulations show that LSCs based on Tm2+ can display excellent color rendering indices of up to 99%, and neutral color temperatures, between 4500K and 6000K. Under optimal conditions, thin-films constrained to a thickness of 10μm and 80% transmission of the visible spectrum, would be able to display optical efficiencies of 0.71%. This optical efficiency compares favorably to the maximally achievable 3.5% under these constraints. This efficiency is largely independent of the size of LSC itself.

Preparation of Ni-doped stainless steel thin films on metal to prevent hydrogen entry via sputter deposition with a powder target

Nickel-doped stainless steel thin films with high hydrogen-entry resistance were prepared on a metal and Si surface via sputter deposition. For this, mixed nickel oxide (NiO) and stainless steel (SUS304) powders were used as the sputtering target. The experimental results indicated that nickel-doped stainless steel thin films could successfully be prepared both on the stainless steel and Si substrate surface. XPS measurements demonstrated that the deposition rate was dependent on the processing conditions such as input RF power, and the thin-film Ni/SUS304 concentration ratio strongly depended on the powder target composition.

Porous CaP Coatings Formed by Combination of Plasma Electrolytic Oxidation and RF-Magnetron Sputtering

The porous CaP subcoating was formed on the Ti6Al4V titanium alloy substrate by plasma electrolytic oxidation (PEO). Then, upper coatings were formed by radio frequency magnetron sputtering (RFMS) over the PEO subcoating by the sputtering of various CaP powder targets: β-tricalcium phosphate (β-TCP), hydroxyapatite (HA), Mg-substituted β-tricalcium phosphate (Mg-β-TCP) and Mg-substituted hydroxyapatite (Mg-HA), Sr-substituted β-tricalcium phosphate (Sr-β-TCP) and Sr-substituted hydroxyapatite (Sr-HA). The coating surface morphology was studied by scanning electron and atomic force microscopy. The chemical composition was determined by X-ray photoelectron spectroscopy. The phase composition of the coatings was studied by X-ray diffraction analysis. The Young’s modulus of the coatings was studied by nanoindentation test. RF-magnetron sputtering treatment of PEO subcoating resulted in multileveled roughness, increased Ca/P ratio and Young’s modulus and enrichment with Sr and Mg. Sputtering of the upper layer also helped to adjust the coating crystallinity.

Sputter deposition with powder targets: An overview

To accommodate to the current trend to study chemically more complex materials, several strategies have been developed to increase the flexibility to deposit these materials by magnetron sputtering. Among these strategies, sputtering from loosely packed powders as a target material, takes a special place as it abandons the requirement of a high density target as a source. The low thermal conductivity, and the inherent presence of impurities, are the major disadvantages of powder targets, and are boundary conditions that always need to be considered when these targets are used. Nevertheless, the easiness to produce any target composition often overrules these disadvantages. Some fundamental aspects specific for these targets, such as sputter yield and angular distribution of the sputtered atoms, are discussed. The use of powder targets is compared to alternative methods to deposit complex thin films.

Preparation of Multielements Mixture Thin Film by One-Step Process Sputtering Deposition Using Mixture Powder Target

Thin films consisting of a mixture of indium, gallium, zinc, and oxygen were fabricated for use as transparent conductive films for liquid crystal and/or electroluminescent displays. The thin films were produced in one step by a sputtering deposition method using mixed powder targets with different proportions of indium oxide, gallium oxide, and zinc oxide. The deposition rate of the films strongly depended on the composition of the target. X-ray photoelectron spectroscopy results revealed that mixed indium, gallium, zinc, and oxygen thin films can be prepared and their element concentration ratio is controlled by the concentration ratio of the powder target.

Combinatorial study of the phase development of sputtered Pb(Zr,Ti)O3 films

For a comprehensive study of the growth mechanisms of Pb(Zr,Ti)O3 (PZT), we employed a combinatorial sputtering method that enabled us to fabricate films with composition and substrate temperature gradients in-plane. The gradient of the amount of Pb supply was created using PZT ceramic and Pb3O4 powder targets. The substrate temperature gradient was generated in an orthogonal direction by inserting a shadow mask between the heater and substrate. The PZT film was deposited on uniformly deposited (001)LaNiO3/Si in a substrate temperature range of 490 °C–570 °C. It was determined that although the growth condition of PZT films has a relatively large process window, the orientation is easily changed by the temperature and the amount of Pb supply. In addition, the range of the growth temperature, where the films show ferroelectricity decreases with decreasing the amount of Pb supply.

Cyclotron production of no carrier added 186gRe radionuclide for theranostic applications

186gRe (T1/2 = 3.7183 d, E(β−)mean = 346.7 keV, I(β−)mean = 92.59%), a mixed beta and γ-emitter shows great potential for use in theranostic applications. The dominant 185Re(n,γ) route, via use of a nuclear reactor, provides 186gRe in carrier added form with low specific activity, while cyclotrons offer no carrier-added (NCA) high specific activity production of 186gRe. However, to be able to select the best possible nuclear reaction and to optimize the production route via the use of a cyclotron, information on the excitation function for the reaction of interest as well as for the competing reactions is necessary. Accordingly, we have conducted a detailed study of the excitation functions for natW(d, x) reactions in seeking optimized parameters for the NCA production of 186gRe. Noting a discrepancy among the experimental data, we made an evaluation of the available literature, finally selecting optimum parameters for the production of 186gRe via the 186W(d,2n)186Re reaction. These beam parameters were then used for batch production of 186gRe by irradiating an enriched 186W metallic powder target, followed by a subsequent automated chemical separation process. The preliminary results show 98.1% radionuclidic purity of 186gRe at 8 h subsequent to the End of Bombardment (EOB), offering the potential for use in clinical applications.