Direct Current Magnetron Sputtering Technique Research Articles

Low resistivity Ru1-xTixO2 thin films deposited by hybrid high-power impulse magnetron sputtering and direct current magnetron sputtering technique

The present paper reports on an experimental investigation of the structural, electrical and optical properties of Ru rich Ru1-xTixO2 thin films. Rutile single-phase Ru1-xTixO2 thin films have been deposited by reactive hybrid High-power impulse magnetron sputtering (HiPIMS) and direct current magnetron sputtering (DCMS) at a substrate temperature of 250 °C. The HiPIMS source was applied to the Ru target while the DCMS source was connected to the Ti target in order to vary the Ti content in the films. The films are well crystallized and compact with randomly orientated nanocrystallites. The optical properties have been investigated by ellipsometric measurements in the optical energy range from 1.3 eV to 3.3 eV, while the electrical resistivity has been measured in the Van der Paw configuration at room temperature. The electrical resistivity increases gradually from 70 μΩcm for pure RuO2 to about 243 μΩcm for Ru1-xTixO2 films with x = 0.13. The optical properties are correlated with the Ti doping. The refractive index n changes from a strong dispersion relationship to a moderate one with increasing Ti content.

Internal reflectance from a disordered monolayer of small gold nanoparticles on a glass substrate: Theory vs. experiment

Abstract In this work we study theoretically and experimentally, the reflectance of a monolayer of nanoparticles randomly located onto a substrate, immersed in a homogeneous medium. The system is illuminated with a laser of wavelength λ = 543 nm in an internal incidence configuration and both p and s polarizations are investigated. The samples are prepared by means of the direct current magnetron sputtering technique, using short erosion times to allow the growing of a non-percolated single layer of gold nanoparticles over the surface of a glass substrate. The particles’ average radius is 5.8±1.25 nm and the surface coverage is estimated to be 29.6±1%. We compare the reflectance predicted by five theoretical models—equivalent-volume, Van de Hulst, Maxwell Garnett, dipolar and coherent scattering—with the measured reflectance of the samples, obtaining a good agreement between the prediction of the dipolar and Maxwell Garnett models with the measured data. These results motivate further studies to consider an application of this system as an ultrasensitive sensor.

Fabrication and characterization of Cu/Cu2O/CuO/ZnO/Al–ZnO/Ag heterojunction solar cells

Glass/Cu/Cu2O/CuO/ZnO/Al–ZnO/Ag heterojunction solar cell structures have been successfully constructed by using a direct current magnetron sputtering technique. Photovoltaic (PV) solar cells fabricated as above indicated a conversion efficiency >5.6% and an open-circuit voltage (VOC) ∼0.57 V. Surface modification of CuO during ZnO deposition was identified as the limiting factor for obtaining higher performance heterojunction cells. Magnetron sputtering acted as a promising inexpensive and scalable technique for the fabrication of the above heterojunction for PV application. The diode quality factor for different cells fabricated here varied between 3.35 and 5.6 which were quite high (>2) compared to that for an ideal one. These are connected with mechanisms like interface recombination and tunneling enhanced interface recombination. Series resistance varied between 18.05 and 19.8 Ω cm2 while shunt resistance varied between 495 and 524 Ω cm2. The minority carrier life time ∼7 ms suggested lower recombination losses in our cells culminating in higher short circuit current density compared to copper oxide based cells fabricated by others.

Photovoltaic properties of F:SnO2/CdS/CuO/Ag heterojunction solar cell

Glass/F:SnO2/CdS/CuO/Ag hetero structure has been fabricated using direct current (d.c) magnetron sputtering and thermal evaporation technique. Cupric oxide (CuO) has been synthesized by direct current magnetron sputtering technique and Cadmium sulphide (CdS) has been deposited by thermal evaporation method. The micro-structural and optical studies were carried out by field emission scanning electron microscope, transmission electron microscope, atomic force microscope and UV–vis spectroscopy. The above heterojunction structure shows the efficiency ∼2.1%. Open-circuit voltage of the cells was ∼0.462 V. The efficiency values obtained here are the highest compared to those reported so far for this glass/F:SnO2/CdS/CuO/Ag structure. Sputtering acted as a viable and inexpensive technique for obtaining this glass/F:SnO2/CdS/CuO/Ag cell structure for PV application.

Experimental study of saturated pool boiling heat transfer with FeCrAl- and Cr-layered vertical tubes under atmospheric pressure

This study compares the nucleate boiling heat transfer coefficient (NBHTC) and critical heat flux (CHF) of two candidate coatings, FeCrAl and Cr, being considered for accident-tolerant fuel (ATF) cladding applications. To form an intrinsic surface roughness, the tube surfaces were initially grinded with 800 and 60 grit sandpapers, and then, FeCrAl and Cr were physically deposited using the direct current magnetron sputtering technique. The FeCrAl- and Cr-layered surfaces became hydrophilic on the lumped nanostructures and superhydrophilic on the particulate nanostructures, respectively. When subjected to the pool boiling conditions of vertically-oriented tubes, the NBHTC and CHF of the FeCrAl-layered tube increased by 24% and 34%, respectively, with the exception of the similar NBHTC generated by the 60 grit sandpaper. In contrast, the NBHTC of the Cr-layered tube decreased by 15% due to the suppressed nucleation on the particulate nanostructures, while CHF increased by 27%. The CHF enhancement was analyzed based on the liquid spreading behavior of a water droplet from the morphological changes. The capillary flow rate, which is a product of the liquid spreading rate, us, and arithmetic roughness height, Ra, resulted in a more accurate prediction of the CHF than the equilibrium contact angle. Additionally, the potential boiling performance of the FeCrAl and Cr coatings were discussed by comparing the pool boiling results of the vertical tube and horizontal plate orientations.

Dielectric breakdown of alumina thin films produced by pulsed direct current magnetron sputtering

Alumina films (~2 μm thick) were deposited with a mixed Cu/Al interlayer onto copper. Direct current (DC)/Pulsed DC (PDC) magnetron sputtering techniques were independently compared for reactive alumina sputtering. In DC sputtered films, elemental aluminium of 9.2 at.% and nano-crystallites were present within the x-ray amorphous matrix, resulting from target arcing. Defects lead to premature dielectric breakdown/increased current leakage. PDC sputtering improved film quality by removing crystallites, metallic clusters and through thickness cracking. Time dependent dielectric breakdown (TDDB) measurements were carried out using conductive atomic force microscopy identified an improvement in dielectric strength (166 to 310 V μm−1) when switching from DC to PDC deposition power. TDDB suggested that at high applied field the dominant pre-breakdown conduction mechanism was Fowler-Nordheim tunnelling in DC films. Tensile pull-off adhesion ranged from 56 to 72 MPa and was highest following incorporation of an Cu/Al blended interfacial layer. Scratch testing indicated various cracking/buckling failures.

Multifunctional Property of Graphene Oxide Nanostructures on Silica-Coated Cotton Fabrics

In this article, the hydrophobic nature of colloidal silica sol prepared using the sol-gel method was studied. Uncoated cotton fabrics were impregnated with the prepared nanosols followed by pad-dry-cure method. The internal structure of nanosol was obtained through transmission electron microscopy. Graphene oxide nanostructures were deposited on the silica-coated fabrics by direct current (DC) magnetron sputtering techniques. The structural and morphological analyses of the coated and uncoated fabrics were performed using the X-ray diffraction and scanning electron microscopy techniques, respectively. The elemental analysis using energy-dispersive spectroscopy confirmed the presence of nanoparticles adhered to the cellulose present on the surface of the fabric. The thermal stability and wettability properties of the coated and uncoated fabrics were studied. The graphene oxide-coated cotton fabrics showed better UV properties and antibacterial activity against Staphylococcus aureus and Escherichia coli. The biocompatibility and UV protection of the coated fabrics were in the order of GOSiCF > silica-coated cotton fabrics > uncoated cotton fabrics.

Investigation of top gate GaN thin-film transistor fabricated by DC magnetron sputtering

Top-gate thin-film transistors (TFTs) with an n-type GaN thin film active channel layer have been fabricated and characterized. At a substrate temperature of 550 °C, rather than room temperature, the GaN thin films deposited by the reactive direct current magnetron sputtering technique have an average grain size of 25 nm. Without high temperature postannealing process, the proposed GaN TFTs exhibit good electrical performance with a field effect mobility of 2.5 cm2/V s, a threshold voltage of 4.5 V, an on/off current ratio of 1.5 × 105, and a subthreshold swing of 0.7 V/decade. The proposed GaN thin film is promising for TFT active channel application in active-matrix display.

Structure and optical properties of Ge/Si quantum dots formed by driving the evolution of Ge thin films via thermal annealing

Ge/Si quantum dots (QDs) are fabricated by driving the transformation of a Ge thin film-deposited using the direct current (DC) magnetron sputtering technique by controlling the subsequent in situ annealing processes. The experimental results indicate that, with the increase in annealing temperature, the volume of Ge QDs increases monotonically, while the QD density initially increases then decreases. The maximal QD density can reach 1.1 × 1011 cm−2 after a 10 min annealing at 650 °C. The Ge–Ge peak of Ge QDs obtained by Raman spectroscopy initially undergoes a blue shift and then a red shift with increasing annealing temperature. This behavior results from the competition between the dislocation and the strain relaxation in QDs. Concurrently, a series of photoelectric detectors are fabricated to evaluate the photoelectric performance of these annealed Ge QD samples. A high-photoelectricity response is demonstrated in the QD sample annealed at 650 °C. Our results pave a promising way for whole-silicon-material optical-electronic integration based on a simple and practicable fabrication method.

Density and microstructure of a-C thin films

In this work, we studied amorphous carbon (a-C) thin films deposited using direct current (dc) and high power-impulse magnetron sputtering (HiPIMS) techniques. The microstructure and electronic properties reveal subtle differences in a-C thin films deposited by two techniques. While films deposited with dcMS have a smooth texture typically found in a-C thin films, those deposited with HiPIMS consist of dense hillocks surrounded by a porous microstructure. The density of a-C thin films is a decisive parameter to judge their quality. Often, x-ray reflectivity (XRR) has been used to measure the density of carbon thin films. From the present work, we find that the determination of density of carbon thin films, especially those with a thickness of few tens of nm, may not be accurate with XRR due to a poor scattering contrast between the film and substrate. By utilizing neutron reflectivity in time of flight mode, it has been shown that the density of carbon films can be measured more accurately. Prime novelty statementIn this work, we have studied amorphous carbon (a-C) thin films prepared by direct current and high power impulse magnetron sputtering (dcMS and HiPIMS). We did precise density measurements using time of flight (ToF) neutron reflectivity (NR), a technique seldom used to study carbon thin films. We amply demonstrate limitation of x-ray reflectivity technique generally used for determination of density of thin carbon films. It is expected that our demonstration of NR in density determination of carbon thin film will turn out to be landmark for carbon film community and will certainly be helpful in enriching the related research work.

Structural, electrical, optical and magnetic properties of NiO/ZnO thin films

Nickel oxide/Zinc oxide (NiO/ZnO) thin films have been deposited onto thoroughly cleaned glass substrates by reactive direct current (DC) magnetron sputtering technique and subsequently annealed at 300 °C for 3 h in vacuum. The NiO/ZnO thin films were then studied for their structural, optical and electrical properties. X-ray diffraction (XRD) pattern of ZnO and NiO showed the diffraction planes corresponding to hexagonal and cubic phase respectively. The optical properties showed that with the increase in the deposition time of NiO the energy band gap varied between 3.1 to 3.24 eV. Hence, by changing the deposition time of NiO the tuning of band gap and conductivity were achieved. The magnetic studies revealed the diamagnetic nature of the NiO/ZnO thin films.

Effect of different sputtering time on the formation of copper and copper oxide nano particles by magnetron sputtering system

Synthesis of copper (Cu) and copper oxide nano particles on SiO2 (silicon oxide) substrate by dc (direct current) magnetron sputtering technique are investigated. A copper cylindrical target was used in Ar plasma medium for deposition under 2 · 10−2 m Torr pressure. The changing of structural form of Cu particles in function of sputtering time has been studied. Powder diffraction patterns provided information about the crystal structure of the surface and the lattice parameter values of the particles. The Atomic Force Microscope (AFM) images revealed a homogeneous structure and size of particles and revealed a homogeneous dispersion within the layer. SEM/EDX was applied to characterize the nanostructures of Cu nanoparticles.

Fabrication of nanostructured silicon nitride thin film gas sensors by reactive direct current magnetron sputtering

In this work, high-quality nanostructured silicon nitride films were prepared by reactive direct current magnetron sputtering technique. The properties of the prepared structures were determined by the ratios of gases (argon and nitrogen) in the discharge gas mixture. This parameter was effectively seen important to control the structural characteristics of the prepared nanostructures, especially surface roughness and particle size. The prepared nanostructures were successfully tested for gas-sensing applications and they exhibited reasonably high sensitivity for their resistance changes to gas concentration with increasing temperature (up to 96% at 350 °C). This work can be good attempt to use silicon nitride nanostructures in such important application.

Influence of nitrogen partial pressure on the microstructure and morphological properties of sputtered RuN coatings

In this work, the production of RuN thin films using the reactive direct current magnetron sputtering technique is presented. Samples were grown with varying Ar/N2 ratio with values of 60/40, 80/20, 85/15, 90/10, 95/5, and 100/0. X-ray photoelectron spectroscopy was employed to determine the presence of RuN before and after a sputtering etching process. According to the high-resolution of N1s spectra, 3 peaks were identified at 397.4 ± 0.3 eV, 398.3 ± 0.3 eV, and 398.8 ± 0.3 eV binding energies, corresponding to hybridizations of nitrogen with transition metals, oxynitrides, and oxycarbides. X-ray diffraction analyses were performed, showing the coexistence of the RuN face-centered cubic and Ru hexagonal compact packed phases. After the etching process, the samples grown at nitrogen flow rates greater than 15% continued to show the RuN face-centered cubic phase. Atomic force microscope analyses showed that as the nitrogen concentration increased, the grain size and roughness also tended to increase.

Cupric oxide (CuO) thin films prepared by reactive d.c. magnetron sputtering technique for photovoltaic application

Cupric oxide (CuO) thin films were synthesized by direct current (DC) reactive magnetron sputtering technique. This technique has proved to be a reproducible one. Ratios of Argon and oxygen gas in the plasma and the substrate temperature during deposition were found to be the key parameters for the formation of CuO polycrystalline films. Films were characterized by using X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, optical spectroscopy, photoluminescence, and Raman spectroscopy techniques. Grain sizes in these films varied between 120 and 220 nm. Films were found to be preferentially oriented in (002) direction. Predominant p-type conductivity in the CuO films was confirmed from Hall measurement. CuO/CdS p-n junction solar cell obtained with non-rationalized layer thicknesses showed an open circuit voltage (VOC) ∼421 mV, short circuit current density (JSC) ∼3.6 mA/cm2, Fill Factor (FF) ∼0.46 and efficiency (ɳ) ∼1.2%.

Effect of sputtering parameters on the self-cleaning properties of amorphous titanium dioxide thin films

The aim of this work was to assess the effect of the direct current magnetron sputtering parameters on the photocatalytic activity and photoinduced wettability of amorphous TiO2 films. TiO2 films were deposited on glass using the direct current magnetron sputtering technique, without heating, at different total working pressures. Qualitative analysis using in situ X-ray photoelectron spectroscopy confirmed the TiO2 stoichiometry of the deposited films. Surface structure was studied as a function of working pressure using scanning electron microscopy. The hydrophilicity of the TiO2 surfaces was investigated macroscopically using measurements of the water contact angle. A threshold working pressure was observed, with a strong dependence on the film thickness. A super hydrophilic surface was observed after less than 1 h of UV irradiation. The photocatalytic activity of the films was evaluated under UV light through the degradation of methylene blue ( $$\lambda_{\hbox{max} } \approx 660\;{\text{nm}}$$ ). The effect of UV irradiation on the photocatalytic activity was rapid, strong, and dependent on film thickness and total working pressure. Fifty percent of organic compounds were photodegraded by films with a thickness of 60 nm deposited at 10 mTorr.

Beryllium-tungsten study on mixed layers obtained by m-HiPIMS/DCMS techniques in a deuterium and nitrogen reactive gas mixture

Beryllium-tungsten 2μm thick layers were co-deposited on molybdenum, graphite and silicon substrates in a reactive argon-deuterium/argon-deuterium-nitrogen gas mixture by means of combining multi-pulse High Power Impulse Magnetron Sputtering and Direct Current Magnetron Sputtering techniques. The elemental composition and thickness of the layers were well controlled during the deposition process. Structural and chemical investigations were undertaken by means of X-ray diffraction and Rutherford backscattering methods. The results showed a change in the samples structure with the adding of nitrogen into the sputtering gas mixture, evidenced by the appearance of W2N peaks in the diffraction patterns. The RBS showed in-depth uniformity of beryllium and tungsten concentrations for the deposited coatings. In order to investigate the deuterium retention mechanisms and to make an assessment of the deuterium inventory, thermal desorption spectrometry was performed. The deuterium desorption spectra for the batch of samples obtained with nitrogen showed an obvious behaviour of shifting to higher temperatures. This behaviour may be related to the nitrogen desorption.

Cuprous oxide (Cu2O) thin films prepared by reactive d.c. sputtering technique

Synthesis of cuprous oxide (Cu2O) by direct current (DC) reactive magnetron sputtering technique has been demonstrated. Ar:O2 gas ratios in the plasma and the substrate temperature were the decisive parameters for the formation of unblemished Cu2O polycrystalline films. The optimal deposition parameters are: Ar:O2 ∼90:10; Ts∼623 K and d.c. power ∼0.6 kV at 1.2 mA/cm2. Optical spectroscopy, photo luminescence, X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy and Raman measurements were carried out to characterize the films. Predominant p-type conductivity in the Cu2O films was confirmed from Hall measurement.

Effect of Oxygen Partial Pressure on the Fabrication and Characterization of LaB6-Doped-NiOx Thin Films Produced By Magnetron Sputtering

Nickel oxide (NiOx) thin films doped with LaB6 were deposited and fabricated by direct current magnetron sputtering technique onto ITO glass substrates with various ratio of argon and oxygen. LaB6 target was just back the cathode and stacked on the nickel metal target on which six holes were drilled and punched to make the La3+ deposit on the substrate. The introduction and addition of La3+ are believed forming the defects, substituting the Ni2+ sites by the analysis of X-ray diffraction, scanning electron microscopy and atomic force microscopy. It obviously leads to the most roughness surface and large crystallite size of the thin films with the ratio of argon and oxygen at 45:5. Moreover, the electrochromic (EC) characteristics response for nonstoichiometric LaB6–doped-NiOx films show a strong dependence on crystallite size variations and surface morphology. Therefore, the as-deposited thin films above demonstrate the good optical contrast and excellent durability, especially the lifetime which can last more than 10000 s. The attempt of this work may be helpful for charactering the EC devices with doping NiOx thin films. We think it will be a big step for the smart windows in energy efficient buildings. Key words: LaB6–doped-NiOx films, optical contrast, electrochromic (EC) characteristics Figure 1

Effects of sputtering parameters and separator plates on the structure and stress of W/Si multilayers in x-ray telescope applications

To develop an x-ray focusing telescope for the Chinese x-ray timing and polarization mission, W/Si multilayers were fabricated using a dedicated cylindrical deposition facility with direct current magnetron sputtering technique. To reduce the interface width of the multilayers, separator plates were mounted at both sides of the substrates to collimate the sputtering particles. The average interface width was reduced from 1.03 nm (without separator plates) to 0.29 nm (with separator plates) for a W/Si multilayer with a 3.8-nm d-spacing. To achieve a high reflectivity multilayer mirror with low stress, the effects of different background and working gas pressures on periodic multilayers during the deposition process were studied. The stress of the W/Si multilayer (d=3.8 nm) slightly increased from −294 to −358 MPa as the background pressure increased from 4×10−5 Pa to 8×10−4 Pa and the first-order Bragg peak reflectivity at 8.04 keV (λ=0.154 nm) decreased from 68% to 54%. As the working pressure increased from 0.4 to 0.8 Pa, the stress of the W/Si multilayer significantly changed from −306 to 100 MPa. However, the first-order reflectivity also decreased dramatically from 67% to 8%, and the average interface width increased from 0.29 to 1.2 nm.