Powder Target Research Articles

Sterilization for Bacillus Subtilis var. natto by Low Pressure Sputtering and Laser Ablation Plasma using Metal Powder Target

Sterilization for Bacillus Subtilis var. natto by Low Pressure Sputtering and Laser Ablation Plasma using Metal Powder Target

Ni-doped ZnO films deposited by RF magnetron sputtering using raw powder target

Pure and nickel-doped zinc oxide thin films were deposited by radio-frequency magnetron sputtering on glass substrates at room temperature using raw powder targets. The dopant concentration was varied from 0 to 4 wt%. Structural characterization of the samples performed with X-ray diffraction confirmed that all films exhibit the hexagonal wurtzite crystal structure with (002) preferred orientation. The average transmittance of all the films is higher than 80% in the visible wavelength region. PL analysis revealed that the ultraviolet emission intensity decreased and exhibited a redshift with increasing Ni concentration. This was consistent with the energy band values (3.35–3.28). A lowest electrical resistivity of 8.42 × 10−4 Ω cm was observed for the pure ZnO films, and by increasing Ni content, the electrical resistivity increases, which was subsequently affected by a decrease in charge carrier concentration. AC and DC conductivities were studied to explore the conduction mechanism. The temperature dependence of both ac conductivity and the parameter s is reasonably well interpreted by the correlated barrier hopping model. Activation energy values deduced from both dc conductivity and relaxation frequency are in the range of 0.49–0.61 eV. The analysis of the parameter s leads to the barrier height Wm values which are in agreement with that proposed by the theory of hopping of charge carriers over the potential barrier between the defect states in the band tail as suggested by Elliott.

Reactive sputter deposition of CoCrCuFeNi in nitrogen/argon mixtures

Thin films of (CoCrCuFeNi)Nx were deposited by direct current reactive magnetron sputtering. Two different targets were used. Thin films deposited from a solid near-equimolar target showed a Cu excess with segregation of Cu in the film resulting in the formation of a nanocomposite film. It was also not possible to reach fully stoichiometric nitride thin films with this target. To overcome this problem, a powder target with adjusted composition was used in a second series of experiments. As derived from longitudinal and transversal sound velocity measurements, a transition from the metallic face-centred cubic lattice to the nitride B1 (NaCl) structure is observed. The observed transition corresponds with the process change from the metallic regime at low nitrogen partial pressure to the poisoned regime at high nitrogen partial pressure. TEM measurements show a typical zone T growth with a strong (100) texture in the nitride regime, and reveal a mixing of the constituent metals at the nanometer scale. This study demonstrates that the constituent metals do not form binary nitrides, but a complex nitride is formed.

Formation of the thin film heterostructures CuO/ZnO by RF magnetron sputtering powder targets

Method for forming thin film heterostructures ZnO/CuO in a single technological cycle with vacuum circuit with use RF magnetron reactive sputtering of copper powder and zinc oxide was offered. The resulting film CuO had band gap of 1.6…1.7 eV and possessed stability up to 350°C. ZnO film had a transparency of 85% in the wavelength range of 400…1100 nm. Selection of medium temperatures for forming the heterostructure (200…250°C) allowed to reduce its series resistance, and the addition of the thin heterojunction structure of the intermediate layer i-ZnO allowed to improve nonlinearity voltage characteristics and improve the photoresponse.

Complex oxide thin films: Pyrochlore, defect fluorite and perovskite model systems for structural, spectroscopic and catalytic studies

Well-ordered thin films of different defect fluorite and perovskite materials, namely lanthanum zirconate (La2Zr2O7), cerium zirconate (Ce2Zr2O7), lanthanum cerate (La2Ce2O7) and lanthanum strontium ferrite (La0.4Sr0.6FeO3), have been prepared by sputtering the respective powder targets onto vacuum-cleaved NaCl(0 0 1) single crystal facets. Characterization specifically also includes the sophisticated preparation of the initial target materials. For the defect fluorite materials, the target materials are the respective pyrochlore compounds, which reproducibly transform to the respective defect fluorite structures upon sputtering. At template temperatures of around 573 K, well-crystallized epitaxial thin films of the defect fluorite compounds La2Zr2O7 and Ce2Zr2O7 result, whereas for the perovskite compound post-annealing procedures at 973 K in air are necessary to obtain epitaxial ordering of orthorhombic structures. Epitaxial relations for the well-ordered defect fluorite thin films are determined to be La2Zr2O7(0 0 1)//NaCl(0 0 1) and Ce2Zr2O7(0 0 1)//NaCl(0 0 1), respectively. Structural and spectroscopic characterization of the films by (high-resolution) electron microscopy (HR-TEM), selected-area electron diffraction (SAED) and depth-profiling X-ray photoelectron spectroscopy (XPS) reveal that the structures and compositions of the initial target materials are well-preserved during the sputtering process. Following this preparation routine, access to well-ordered thin films of complex oxide materials with defined stoichiometry is therefore granted, which can subsequently be used as model systems for studies of their material’s or catalytic properties, as presented for simpler systems earlier. As a primary example, we show that for the defect fluorite thin films of Ce2Zr2O7 the defect fluorite-pyrochlore phase transformation can be observed at around 1123 K as detected by in situ electron diffraction.

Preparation of metal doped SiO<sub>2</sub> films by magnetron sputtering deposition using metal oxide mixture powder target

Metal doped SiO2 thin films, which show strong luminescence by UV excitation, were prepared by a sputtering deposition method using metal oxide and SiO2 powder mixed targets. Electron density and temperature of the plasma using powder target was almost same independent for the mixture of powder target. However, peak intensity ratio of the plasma depends on the intensity of the powder target mixture. XPS measurements suggest that metal doped SiO2 thin films can be prepared using metal oxide and SiO2 mixture powder target, and their concentration ratio also depend on the powder target mixture.

Growth and characterization of indium doped zinc oxide films sputtered from powder targets

Indium doped ZnO films were grown on quartz glass substrates by radio frequency magnetron sputtering from powder targets. Indium content in the targets varied from 1at% to 9at%. In doping on the structure, optical and electrical properties of ZnO thin films were studied. X-ray diffraction shows that all the films are hexagonal wurtzite with c-axis perpendicular to the substrates. There is a positive strain in the films and it increases with indium content. All the films show a high transmittance of 86% in the visible light region. Undoped ZnO thin film exhibits a high transmittance in the near infrared region. The transmittance of indium doped ZnO thin films decreases sharply in the near infrared region, and a cut-off wavelength can be found. The lowest resistivity of 4.3×10-4 Ω·cm and the highest carrier concentration of 1.86×1021 cm-3 can be obtained from ZnO thin films with an indium content of 5at% in the target.

Structural and optical properties of ZnO thin films prepared by laser ablation using target of ZnO powder mixture with glue

ZnO thin films were deposited on ITO/glass substrates by pulsed laser deposition (PLD) using two different kinds of targets. One of the targets was made of pure ZnO powder and the other one consisted of a mixture of ZnO powder with cyanoacrylate glue. The structural and morphological properties of the films obtained using both targets were compared, in order to determine which one produces samples with properties more suitable for their use as buffer and antireflective layer in CdTe-based solar cells, also different heterostructures were deposited to study the optical properties of the obtained thin films and their utility in the applications mentioned before. The films deposited with the mixture powder target were polycrystalline with preferential orientations in the planes (100) and (101) with a high transmittance in the range of 70–90% in the 540–850 nm wavelength region and showed a high resistivity of \({\sim }1.30 \times 10^{2} \,\Omega \hbox { cm}^{-1}\), such properties are considered to be appropriate for thin films that are wanted to be used as a buffer and antireflective layer in CdTe solar cells.

Combinatorial screening of halide perovskite thin films and solar cells by mask-defined IR laser molecular beam epitaxy

As an extension of combinatorial molecular layer epitaxy via ablation of perovskite oxides by a pulsed excimer laser, we have developed a laser molecular beam epitaxy (MBE) system for parallel integration of nano-scaled thin films of organic–inorganic hybrid materials. A pulsed infrared (IR) semiconductor laser was adopted for thermal evaporation of organic halide (A-site: CH3NH3I) and inorganic halide (B-site: PbI2) powder targets to deposit repeated A/B bilayer films where the thickness of each layer was controlled on molecular layer scale by programming the evaporation IR laser pulse number, length, or power. The layer thickness was monitored with an in situ quartz crystal microbalance and calibrated against ex situ stylus profilometer measurements. A computer-controlled movable mask system enabled the deposition of combinatorial thin film libraries, where each library contains a vertically homogeneous film with spatially programmable A- and B-layer thicknesses. On the composition gradient film, a hole transport Spiro-OMeTAD layer was spin-coated and dried followed by the vacuum evaporation of Ag electrodes to form the solar cell. The preliminary cell performance was evaluated by measuring I-V characteristics at seven different positions on the 12.5 mm × 12.5 mm combinatorial library sample with seven 2 mm × 4 mm slits under a solar simulator irradiation. The combinatorial solar cell library clearly demonstrated that the energy conversion efficiency sharply changes from nearly zero to 10.2% as a function of the illumination area in the library. The exploration of deposition parameters for obtaining optimum performance could thus be greatly accelerated. Since the thickness ratio of PbI2 and CH3NH3I can be freely chosen along the shadow mask movement, these experiments show the potential of this system for high-throughput screening of optimum chemical composition in the binary film library and application to halide perovskite solar cell.

Preparation of tris(8-hydroxyquinolinato)aluminum thin films by sputtering deposition using powder and pressed powder targets

Tris(8-hydroxyquinolinato)aluminum (Alq3) thin films, for use in organic electroluminescence displays, were prepared by a sputtering deposition method using powder and pressed powder targets. Experimental results suggest that Alq3 thin films can be prepared using powder and pressed powder targets, although the films were amorphous. The surface color of the target after deposition became dark brown, and the Fourier transform infrared spectroscopy spectrum changed when using a pressed powder target. The deposition rate of the film using a powder target was higher than that using a pressed powder target. That may be because the electron and ion densities of the plasma generated using the powder target are higher than those when using pressed powder targets under the same deposition conditions. The properties of a thin film prepared using a powder target were almost the same as those of a film prepared using a pressed powder target.

Sn doping effects on properties of ZnO thin films deposited by RF magnetron sputtering using a powder target

In the present study, tin doped ZnO thin films (ZnO:Sn) at different contents (0–3 wt%) were deposited onto glass substrates by RF magnetron sputtering using a powder compacted target at room temperature. The effect of Sn concentration on the structural, optical and electrical properties of the ZnO:Sn thin films were investigated. The X-ray diffraction analysis shows that the pure ZnO thin film exhibits a strong intensity of the (002) peak indicating a preferential orientation along the c-axis. For Sn doped ZnO thin films, there is a change in the orientation from the (002) plane to the (101) one. The undoped ZnO thin films have transmittance 85% in the visible range and slightly increased for 0.5 wt% of Sn, while it get decreased with further increasing the Sn doping concentration. The optical band gap energy get increased with increasing the doping concentration. Moreover, the electrical conductivity and conduction mechanism are also studied by impedance spectroscopy in the frequency range of 1KHz–13 MHz at various temperatures (633–743 K). The AC conductivity in ZnO thin films increased with angular frequency. The frequency exponent S decreases with increasing temperature. Such behavior suggests that the correlated barrier hopping (CBH) model may be suitable to explain the conduction mechanism in ZnO thin films. The activation energy values calculated from angular frequency and DC conductivity are in good agreement confirming that the conduction mechanism is thermally activated by hopping between localized states.

Transparent NaGdF4:Nd3+ colloid prepared by femtosecond laser ablation as a liquid laser medium

By using femtosecond-pulsed laser to ablate the larger nanosized target in liquid, stable transparent NaGdF4:Nd3+ colloid has been successfully fabricated. The X-ray diffraction (XRD) spectra reveal that the colloidal nanoparticles remain the hexagonal phase crystal structure of NaGdF4 powder target. SEM and TEM images results indicate that the size of these colloidal nanoparticles decreases sharply. FT-IR results indicate that the number of O–H and C–H groups on the surface is decreased. The emission properties of the colloid have been investigated using 794nm pulsed wave laser radiation, and it is found that the colloid exhibits near-infrared luminescent emissions in the spectral range of 850–1400nm, and the decay time for 4F3/2→4I11/2 (1058nm) Nd3+ ion transitions is lengthened than that of powder target, these results are probably due to the reduced nonradiative relaxation assisted by high energy oscillators. The observed near-infrared emission of the stable transparent colloid makes it a good candidate for application in liquid laser.

Study on the influence of powder size on the properties of BTS/ITO thin film by RF sputtering from powder target

BaSn0.15Ti0.85O3 (BTS) thin films were deposited on a tin-doped indium oxide (ITO)/glass substrate by RF sputtering from a powder target using BTS powders of different particle sizes, the structural and electrical properties of the BTS thin film investigated. The results indicate that deposition rate and electrical properties of the BTS film are strongly related to the particle size of BTS powder, with the deposition rate increasing with a decrease in the powder particle size. When the particle size of the BTS powder is 70nm, a deposition rate of 40nm/min was achieved. The leakage current density decreases with increasing the deposition rate when depositing the BTS thin film. Further, the leakage current density of the BTS thin film by the nano-powder is one order of magnitude higher than that of the micron powder, while the leakage current density is lower than 7.83×10−9A/cm2, the dielectric tunability reaches 57.8% and dielectric loss remains only 0.017 at bias voltage of 5V.

Investigation into the optoelectrical properties of TiO2thin films, deposited by RF magnetron sputtering using powder target

TiO2 thin films were deposited at different deposition times and argon flows, onto glass substrates by radio-frequency (RF) magnetron sputtering technique, using a powder target. The X-ray diffraction analysis shows that the increase in the deposition time introduces an improvement in crystallinity of the deposited films with the formation of a rutile phase. This rutile phase is maintained for the samples elaborated at different argon flows. The optical transmittance for all the samples is found to be higher than 75% in the visible region. A slight decrease of the band gap values is observed for all the studied films. The electrical conductivity and conduction mechanism are also studied by means of the impedance spectroscopy technique. The activation energy values calculated from angular frequency and DC conductivity are in good agreement, indicating that the conduction mechanism is thermally activated by hopping between localized states. Additionally, the investigation of the frequency and temperature dependence of AC conductivity agrees with the correlated barrier hopping model.

Low temperature pulsed direct current magnetron sputtering technique for single phase β-In2S3 buffer layers for solar cell applications

This work explores the possibilities of using the pulsed direct current (dc) magnetron sputtering (PDCMS) process to deposit an alternative to the cadmium sulphide buffer layer in copper indium gallium diselenide – based solar cells. The main problems with the CdS layer are its toxic nature and its deposition using a chemical bath technique. These factors make it difficult to incorporate into in-line production and significant effort has been expended to find a suitable alternative buffer layer with in-line manufacturing capability. Towards this aim, the material properties of an In2S3 film, sputtered from a powder target, have been investigated. Films were deposited at different substrate temperatures ranging from “no additional substrate heating” to 250°C. The deposition of a single phase β-In2S3 without substrate heating/annealing has not previously been reported. The films deposited by the ion-enhanced PdcMS technique without any additional heating were found to be single phase. The grain size increased with increase in substrate temperature. However, this led to a decrease in the sulphur content; as a result the band gap decreased. For solar cell applications, the CdS buffer layer (optical band gap ∼2.4eV) needs to be replaced with a material which has a band gap wider than 2.4eV for improved performance and reduction of absorption loss in the blue wavelength region. Ideally the band gap should be between 2.6 and 3.0eV. Our PdcMS room temperature deposited In2S3 had a measured band gap of 2.77eV.

Superhydrophobic photocatalytic PTFE – Titania coatings deposited by reactive pDC magnetron sputtering from a blended powder target

The production of photocatalytic coatings with superhydrophobic properties, as opposed to the conventional hydrophilic properties, is desirable for the prevention of adhesion of contaminants to photocatalytic surfaces with subsequent deterioration of photocatalytic properties. In this work polytetrafluoroethylene (PTFE) – TiO2 composite thin films were deposited using a novel method of reactive pulsed direct current (pDC) magnetron sputtering of a blended PTFE – titanium oxide powder target. The surface characteristics and photocatalytic properties of the deposited composite coatings were studied. The as-deposited coatings were annealed at 523 K in air and analysed with Raman spectroscopy, optical profilometry and scanning electron microscopy. Hydrophobicity was assessed though measurements of water contact angles, and photocatalytic properties were studied via methylene blue dye degradation under UV irradiation. It was found that variations of gas flow and, hence, process pressures allowed deposition of samples combining superhydrophobicity with stable photocatalytic efficiency under UV light irradiation. Reversible wettability behaviour was observed with the alternation of light-dark cycles.

Preparation of Sn doped SiO<sub>2</sub> films using SiO<sub>2</sub> and SnO<sub>2</sub> mixture powder target by magnetron sputtering deposition

Preparation of Sn doped SiO<sub>2</sub> films using SiO<sub>2</sub> and SnO<sub>2</sub> mixture powder target by magnetron sputtering deposition

Thin-film preparation by back-surface irradiation pulsed laser deposition using metal powder targets

Several kinds of functional thin films were deposited using a new thin-film preparation method named the back-surface irradiation pulsed laser deposition (BIPLD) method. In this BIPLD method, powder targets were used as the film source placed on a transparent target holder, and then a visible-wavelength pulsed laser was irradiated from the holder side to the substrate. Using this new method, titanium oxide and boron nitride thin films were deposited on the silicon substrate. Surface scanning electron microscopy (SEM) images suggest that all of the thin films were deposited on the substrate with some large droplets irrespective of the kind of target used. The deposition rate of the films prepared by using this method was calculated from film thickness and deposition time to be much lower than that of the films prepared by conventional PLD. X-ray diffraction (XRD) measurement results suggest that rutile and anatase TiO2 crystal peaks were formed for the films prepared using the TiO2 rutile powder target. Crystal peaks of hexagonal boron nitride were observed for the films prepared using the boron nitride powder target. The crystallinity of the prepared films was changed by annealing after deposition.

Structural, optical and electrical investigations on Nb doped TiO2 radio-frequency sputtered thin films from a powder target

Pure and Nb doped TiO2 (TNO) thin films were deposited onto glass substrates by RF magnetron sputtering technique using a Nb and TiO2 mixture powder target at room temperature to explore the possibility of producing sputtered TNO films by a low cost process. The effect of Nb doping on the structure, morphology, optical and electrical properties of the prepared films was studied by systematically varying the Nb content from 2 to 6 wt%. GXRD results show that the deposited films mainly possess rutile phase with the (110) orientation. Raman spectra confirm that the deposited films are predominantly rutile phase. Surface roughness increases with the increase of Nb doping concentration , which may be attributed to the structural changes in the film due to the incorporation of Nb into the TiO2 lattice. Optical transmittance in the visible range reaches 85 % for the undoped films then it decreases as the doping content increases. Doping by niobium resulted in a slight increase in the optical band gap energy of the films due to the Burstein–Moss effect. The resistivity measurement of TNO films reveals that the Nb doping improves the electrical conductivity of the deposited films compared to the undoped one. The best value was observed for films deposited at 4 wt% Nb.

Investigation of physico-chemical properties of conductive Ga-doped ZnO thin films deposited on glass and silicon wafers by RF magnetron sputtering

We report on the physico-chemical properties of Undoped and Ga-doped ZnO films fabricated on glass and p-Silicon wafers at room temperature by RF magnetron sputtering using a ZnO and Ga2O3 mixture raw powder target without sintering procedure. X-ray diffraction (XRD) and energy dispersion spectroscopy (EDS), scanning electronic microscopy, Raman scattering, ultraviolet–visible spectroscopy, photoluminescence (PL), Hall effect and impedance spectroscopy technique have been applied for the comparative study of ZnO and ZnO:Ga thin films. XRD and Raman studies have shown that the deposited films have a preferred orientation growth with Ga atoms both in substitutional and interstitial positions. EDS analyses have allowed to show that the metallic Ga atoms have been incorporated in the ZnO films. Doping by gallium resulted in a slight increase in the optical band gap energy of the films while the optical transmittance remains about 80 %. The PL analysis at room temperature revealed violet, blue, green and red emissions. Room temperature Hall measurements show that the lowest resistivity was 3.40 × 10−4 Ω cm with an electron mobility of 18.56 cm2/V.s for an optimum Ga concentration of 4 wt%. Impedance spectroscopy study showed that σac obeys the relation \(\sigma_{ac} = A\omega^{s}\). The exponent ‘‘s’’ was found to decrease with increasing the temperature. It is found that, the AC conductivity of all samples follow the correlated barrier hopping model. The Nyquist plots showed a single semicircle, indicating an equivalent circuit with a single parallel resistor R and capacitance C network. The values of the activation energy E a deduced from both DC conductivity and relaxation frequency for all the studied samples ranged from 0.51 to 0.73 eV and the results are explained on the basis of the induced defects due to the addition of Ga into the ZnO films.