Inverted Cylindrical Magnetron Sputtering Research Articles

Ultra-conductive wires with cascaded carbon nanotube/Cu structure

In the present study, ultra-conductive wires were produced by the cascaded Cu/MWCNT wire structure. Cascaded wires were prepared on the industrial 1 mm diameter Cu wire with two steps; Firstly, electrophoretic deposition (EPD) was used to deposit the functionalized MWCNT on the Cu wires. Secondly, a novel inverted cylindrical magnetron sputtering (ICMS) has been built to coat Cu on the MWCNT deposited Cu wire. Different number of cascaded layers up to 13 layers of Cu/MWCNT wires as well as different Cu coating parameter were produced. High deposition rate of MWCNT on Cu wires has been achieved by the EPD method. As can be seen from the cross-sectional SEM images, the intended cascaded structures were successfully formed. The ampacity of the 1 mm industrial Cu wire used in this study has increased by 9.2%. In addition, the temperature of the cascaded wires has shown slow increase compared to that of reference Cu wire. On the other hand, the maximum current able to carry with 1 °C temperature raise has increased by 50%.

Comparative study of discharge characteristics and associated film growth for post-cathode and inverted cylindrical magnetron sputtering

In this study, an experimental investigation of a DC cylindrical magnetron discharge for argon gas in post-cathode (i.e. direct) and hollow-cathode (i.e. inverted) configurations was carried out. The discharge properties at different externally applied magnetic fields and operating pressures were measured and compared for both the configurations. The discharge current (I)–voltage (V) characteristics obey $${I\propto V^n}$$ , where the value of n is in the range of 3–8. The discharge current increases linearly with the magnetic field in the post-cathode configuration, whereas it saturates at higher magnetic fields in the case of inverted configuration. Measurement of plasma potential indicated a considerable anode fall in the inverted magnetron configuration, whereas a negligible anode fall and strong cathode fall were observed in the case of post-cathode configuration. The plasma density and electron temperature, measured using a double Langmuir probe, were observed to be higher in the inverted magnetron configuration. The plasma density was found to be maximum at around 3–4 cm away from the respective inner electrode in both the configurations. A clear change in surface morphology of copper thin film was observed in the case of inverted magnetron configuration, which might be due to the extra ionisation near the anode owing to the anode fall.

High substrate temperature induced anomalous phase transition temperature shift in sputtered VO 2 thin films

Vanadium dioxide (VO 2) thin films were deposited onto Corning glass substrates by rf reactive inverted cylindrical magnetron sputtering at different substrate temperatures ( T s) ranging from 450 to 600 °C. The influence of substrate temperature on the structural and optical properties was systematically investigated. It revealed that the crystallinity of the VO 2 films improved significantly with T s. The substrate temperature to obtain films with transition temperature ( T c ∼ 70 °C) similar to VO 2 bulk single crystal was 450–500 °C, while high substrate temperatures from 550 to 600 °C tend to shift T c towards higher temperatures from 75 to 80 °C keeping the sharpness of the transition unaltered. Even if the variation of the T c of VO 2 is not dramatic “variation from 70 to 80 °C” with increasing T s is substantial for undoped VO 2 thin films. This sizeable variation of ∼10 °C confirms the tunability of the T c of VO 2 through T s.

Thermochromic nanocrystalline Au–VO 2 composite thin films prepared by radiofrequency inverted cylindrical magnetron sputtering

Highly crystalline Au–VO 2 nanocomposite thin films were prepared on Corning glass substrates by reactive radiofrequency inverted cylindrical magnetron sputtering (ICMS). It is a low cost potential coating technology for the production of large area uniform nanocomposite thin films exhibiting plasmonic properties. This paper reports the synthesis and feasibility of reliably reproduced high quality of Au–VO 2 by ICMS. Structural, morphological, interfacial analysis and optical properties of synthesized Au–VO 2 nanocomposite thin films are reported.

Effects of substrate positioning for TiAlN films deposited by an inverted cylindrical magnetron sputtering system

TiAlN films up to 500 nm thick were deposited on glass substrates at three different positions inside an unbalanced inverted cylindrical magnetron sputtering system. The system used two 75 mm tall cylindrical targets (one titanium and one aluminum) separated by about 80 mm. One substrate was located near the titanium target, another near the aluminum target, and a third centered between the targets. In addition, at each location substrates were oriented at three different angles (0, 45, and 60°, measured relative to a horizontal platform). The sputtering power during deposition was maintained at 2 kW with constant argon and nitrogen gas flow rates. The films' elemental compositions at the different locations and orientations were analyzed using energy dispersive X-ray spectroscopy. The X-ray diffraction results showed the presence of a (200) NaCl crystal structure in some of the deposited films; however, the peak intensity varied with the substrate orientation indicating a competition between atom surface diffusion and amorphization. Scanning electron microscope images indicated a grained morphology for all samples.

Thermochromic VO 2 thin films synthesized by rf-inverted cylindrical magnetron sputtering

The novel physical vapor deposition called inverted cylindrical magnetron sputtering (also known as hollow cathode sputtering) is commonly used to coat wires, fibers, ribbons as well as all sides of three-dimensional substrates. It is a reproducible method for the production of nano-structured systems onto complex shapes substrates. This paper reports the first synthesis and feasibility of reliably reproduced stoichiometric pure textured VO 2 nano-structures by the rf-inverted cylindrical magnetron sputtering. Morphological, structural, elemental analysis and optical properties of synthesized VO 2 under optimized conditions are reported.

Effect of deposition conditions on YBa 2Cu 3O 7− δ thin films by inverted cylindrical magnetron sputtering and substrate effects

The dependence of YBCO thin film properties on the deposition conditions was studied for different substrates. The deposition conditions were optimized for the epitaxial growth of high quality YBCO thin films of 1500 Å thickness onto single crystal (100-oriented) SrTiO 3 (STO), MgO and LaAlO 3 (LAO) substrates by DC Inverted Cylindrical Magnetron Sputtering (ICMS). The samples were investigated in detail by means of X-ray diffraction analysis (XRD), EDX, AFM, ρ– T, magnetic susceptibility and current–voltage ( I– V) characterizations. The samples show strong diamagnetic behavior and sharp transition temperatures of 89–91 K with Δ T<0.5 K. XRD of the samples exhibited highly c-axis orientation. The full width at half maximum (FWHM) values of the rocking curves were ranging typically from 0.22 to 0.28°. The samples have smooth surfaces as shown from AFM micrographs. The surface roughness, R a, changed between 5–7 nm. I– V characteristics were obtained from the 20 μm-wide microbridges, which were patterned by a laser writing technique. The critical current densities ( J c, 1.06×10 6 for LAO-based YBCO, 1.39×10 6 for MgO-based YBCO, 1.67×10 6 A/cm 2 for STO based YBCO) of the microbridges were evaluated from I– V curves at 77 K.

The electrical properties of YBa 2Cu 3O 7− δ thin films of various thicknesses grown upon MgO substrates

We have studied the vortex-related phase-transition-like behaviour in high quality YBa 2Cu 3O 7− δ (YBCO) films of thickness ranging from 10 to 200 nm grown upon MgO substrates using a DC inverted cylindrical magnetron sputtering (ICMS) technique. Good scaling collapse of the current–voltage isotherms from the region near the transition has been observed under an algorithm based on the hypothesis that there is a continuous thermodynamic phase transition such as the one proposed for the transition between a vortex-glass and a vortex-liquid. The scaling works for all film thicknesses, and from zero magnetic field through the fields of the order of 1 T. Even though we have not been able to explore the lower scaling branch of the 10 nm film at higher fields, it is noteworthy that the same algorithm, rather than the one proposed for 2D behaviour, collapses the data. For the 30–200 nm thick films, we observe systematic variation of the scaling exponents z and ν with film thickness and magnetic field; in particular, z increases substantially with decreasing film thickness. For the 10 nm film, the exponents found are similar to those of very thick films. We point out that the magnitudes of zν and the range of temperatures over which good scaling collapse is observed are not consistent with an interpretation based on a continuous thermodynamic phase transition, which clearly fails to capture some important elements of the physics.

HTS quasiparticle injection devices with large current gain at 77 K

Recent progress on the development of planar QP-injection devices using YBCO and STO as an epitaxial injection barrier will be discussed. The main problem for HTS injection devices is to grow reliably a well defined, ultra-thin tunneling barrier suitable for QP tunneling. For this purpose, we used inverted cylindrical magnetron sputtering to first optimize the smoothness of our YBCO films by controlling tightly an relevant sputtering conditions. We are able to prepare smooth [001] YBCO films on [001] STO substrates on a routine basis with an average roughness varying between 1 and 2 nm. With these flat YBCO films both planar as well as grain boundary junctions were fabricated using epitaxial STO barriers between 2 and 8 nm thick and a 50 nm of Au counter electrode. Planar junctions with 6 nm STO barriers were in most cases fully insulating, in some cases, a current gain of up to 7.4 at 77 K was obtained. For 3 nm STO barriers, the highest current gain was 15 at 81 K. The injection results also show a scaling behavior with junction size. Based on the present materials development and device understanding, we consider a current gain of up to 20 at 77 K possible.

Fabrication of YBCO step-edge Josephson junctions by inverted cylindrical magnetron sputtering technique

The Inverted Cylindrical Magnetron Sputtering (ICMS) technique been used to fabricate YBCO step-edge dc SQUIDs. Steps are obtained by standard ion milling procedure on LaAlO/sub 3/ (100) substrates using Nb-masks patterned by reactive ion etching. Thin films are then deposited under different conditions (both step and deposition angles) and patterned by standard lithography and wet chemical etching. An analysis of junction properties in terms of step height and film thickness has been carried out. Measurements on current vs magnetic field and SQUID voltage response measurements have been performed. Their temperature dependences have been also considered. Operating temperature as high as 77 K has been achieved. At 4.2 K the SQUIDs show a maximum voltage to flux transfer function (/spl part/V//spl part//spl phi/)/sub max/=870 /spl mu/V//spl Phi//sub 0/ and a good periodicity of the V-/spl phi/ modulation up to 20 /spl Phi//sub 0/ without any sign of hysteresis.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Morphological and structural properties of high quality YBCO thin films

High-quality YBCO thin films have been grown by Inverted Cylindrical Magnetron Sputtering (ICMS) on LaAlO3(100), SrTiO3(100), SrTiO3(110), and MgO(100) substrates. Transition temperatures of c-axis films exceed 90 K, and transition widths are within 1 K. Critical currents range up to 5 × 106 A/cm2 at 77 K. Structural and morphological features analyzed by x-ray diffraction and scanning electron microscopy, respectively, are found to be strongly dependent on film orientation and deposition temperature. In order to understand such dependence, a simple interpretation is proposed in terms of Gibbs energies and growth dynamics of the nucleation process.

Structural and morphological properties of ultrathin YBCO films grown on single-crystal substrates

Epitaxial (001)-oriented ultrathin YBCO films of different thicknesses are deposited by Inverted Cylindrical Magnetron Sputtering (ICMS) on (100) MgO single-crystal substrates. The mean films stoichiometry is determined by Rutherford Backscattering (RBS). Auger Electron Spectroscopy (AES), X-ray Photoemission Spectroscopy (XPS) and Scanning Electron Microscopy (SEM) are employed in order to analyse film growth, and identify spurious phases present in the samples.

YBCO step-edge SQUIDs by magnetron sputtering technique

YBCO step-edge junction d.c. SQUIDs have been realized by using the Inverted Cylindrical Magnetron Sputtering (ICMS) technique. This last represents a novel technology for high-T c Josephson junctions (HTSC). Steps are obtained by standard ion milling procedure on LaAlO3 (100) substrates using Nb-masks patterned by reactive ion etching. Measurements of currentvs. voltage, maximum d.c. Josephson currentvs. magnetic field and SQUID voltage response measurements have been performed, also as a function of the temperature. Operating temperature as high as 77K has been achieved. At 4.2K the SQUIDs show a maximum voltage of flux transfer function ∂V/∂φ max = 870μV/Φ 0and a good periodicity of theV-ϕ modulation up to 20Φ without any sign of hysteresis. The ratio between the step height (h) and the film thickness (d) seems to play a fundamental role in determining Josephson properties of the bridges, these conditions being more severe with respect to most of the data available in literature.