Indigenous development of ultra high vacuum (UHV) magnetron sputtering system for the preparation of Permalloy magnetic thin films

We have designed and developed an indigenous ultra high vacuum (UHV) sputtering system which can deposit magnetic thin films with high purity and good uniformity. The equipment consists of state-of the-art technologies and sophistication. With this system it is possible to deposit coatings of various materials on a sample size of 3”3” 3”. The Ni81Fe19 ferromagnetic thin films, with Tantalum (Ta) as a buffer and cap layers have been deposited on silicon substrates using this ultra high vacuum (UHV) sputtering system. The magneto transport measurement study indicated a significant variation in the AMR values of the films for varying thicknesses of tantalum and NiFe layers

Indigenous development of ultra high vacuum (UHV) magnetron sputtering system for the preparation of Permalloy magnetic thin films

We have designed and developed an indigenous ultra high vacuum (UHV) sputtering system which can deposit magnetic thin films with high purity and good uniformity. The equipment consists of state-of the-art technologies and sophistication. With this system it is possible to deposit coatings of various materials on a sample size of 3”3” 3”. The Ni81Fe19 ferromagnetic thin films, with Tantalum (Ta) as a buffer and cap layers have been deposited on silicon substrates using this ultra high vacuum (UHV) sputtering system. The magneto transport measurement study indicated a significant variation in the AMR values of the films for varying thicknesses of tantalum and NiFe layers

Synthesis of Carbon Nanotubes by Single Zone Pyrolysis Technique

Multi-walled carbon nanotube (MWNT) and combination of single-walled (SWNT) and MWNT were synthesized using pyrolysis assisted chemical vapor deposition method. A single hot zone furnace was used for the synthesis of carbon nanotubes at various temperatures in the range of 750-900C. The as-prepared CNT consisted of carbonaceous impurities and traces of transition metal contents. The as-prepared CNT was oxidized at 500C and then treated with hydrochloric acid which resulted in pure CNT with a purity of 95%. The carbon nanotubes were characterized using field emission scanning electron microscopy (FESEM) and micro-Raman spectroscopy techniques. FESEM images clearly showed the presence of carbon nanotubes and the diameters of the MWNT prepared at various temperatures were in the range of 35-100 nm. The Raman spectroscopy data also showed the presence of D, G and 2D peaks which confirm the presence of CNT

Indigenous development of a four-cathode reactive direct current unbalanced magnetron sputtering system for the deposition of hard coatings on small engineering components

Physical vapor deposited hard coatings are routinely being used in many industrial applications. These coatings are mainly deposited using sputtering methods. The commercial sputtering systems are highly expensive. NAL has developed a cost effective semi-industrial magnetron sputtering system to deposit a variety of thin coatings on small engineering components. Using the design inputs given by NAL, a local firm has fabricated a custom-built unbalanced magnetron sputtering facility. This equipment consists of state-of-the-art technologies and sophistication. The indigenous fabrication has resulted in huge savings. The sputtering system has been successfully installed and commissioned in the laboratory and is working satisfactorily. With this system it is possible to deposit thin coatings of various materials on a sample size of 666. This report describes all the technical details of the sputtering system. We discuss in detail various technical problems in designing such kind of sputtering system. Also, presented in the report are the preliminary results of TiN coatings deposited on a variety of small engineering components. Finally, we present the potential applications of the sputtering system for the deposition of hard coatings, nanolayered multilayer coatings, nanocomposite coatings, oxide coatings, magnetic multilayers, smart materials, duplex coatings, gradient coatings, solid lubricant coatings, magnetic thin films, etc

Thermally induced perpendicular magnetic anisotropy in CoFeB/MgO/CoFeB based magnetic tunnel junction

Thin films of CoFeB/MgO/CoFeB based MTJ structure were deposited using UHV magnetron sputtering system and post annealing treatment in the temperature range from 100 to 400 °C has been carried out to understand their magnetic anisotropic properties. Though the as-deposited stack possesses in-plane magnetic anisotropy, the changeover to perpendicular magnetic anisotropy happens at temperature above 200 °C. The PMA is maximum (4.5 x 106 erg/cm3) when annealed at 300°C and the stack retains PMA till 350 °C, which is necessary in CMOS technology. The stack regains in-plane magnetic anisotropy at higher annealing temperatures due to intermixing at interfaces

Design, fabrication, and characterization of giant magnetoresistance (GMR) based open-loop current sensor with U-shaped current carrying conductor

In this work, an open-loop current sensor based on giant magnetoresistance (GMR) effect in magnetic multilayered systems was designed and developed. The whole design of the current sensor consisting of a magnetic field sensing element, a current-carrying conductor, a permanent magnet, and a magnetic shield was conceptualized through FEM analyses. The simulated model was then replicated into a prototype device and the output characteristics were investigated thoroughly under different ambient conditions. It was observed that in an analog mode, the sensor output was linear in the current range of± 50 A over the temperature range of − 40 °C to 125 °C and showed a − 3 dB frequency response at 7.5 kHz. A thermal drift and offset were observed at the analog output which further compensated through a commercial mixed-signal conditioner. The compensated output showed a total error less than 1% F.S. over the operating temperature range of − 25 °C to 105 °C

Performance evaluation of TiN coated high-speed steel drill bits

Usage of stainless steel materials has increased continuously in various industrial applications. However the machinability of these materials is difficult. The stainless steels in general are considered to be difficult to machine materials. This is mainly due to the high plasticity and tendency to work-harden of the stainless steel, which usually results in severe cutting conditions. Additionally, stainless steels have much lower thermal conductivity as compared to structural carbon steels; this inflicts high thermal impact within the chip-tool contact zone, which significantly increases the cutting tool wear rate. High speed steels (HSS) tools are commonly used for drilling/tapping/turning operations. The surface is either untreated or coated with physical vapor deposition (PVD) coatings. In most cases TiN, TiCN or TiAlN coatings are used. The adhesion is of vital importance for the performance of tools coated with titanium nitride. Proper surface treatments (in situ and ex-situ) are required to achieve highly adherent coatings. We have deposited TiN coatings on high-speed steel drill bits and other substrates using a four-cathode reactive DC magnetron sputtering system. Various treatments have been given to the substrates for improved adhesion of the coating. The process parameters have been optimized to achieve thick and highly adherent good quality TiN coatings. These coatings have been characterized using a variety of techniques. The performance of the coated drill bits is evaluated by drilling a 13mm thick 304 stainless steel sheet under wet conditions. The results are compared with the standard commercially available TiN coatings

Tailoring H/E ratio of Ti-TiN nano-composite coatings with improved toughness for tribological applications

Nanocomposite Ti-TiN coatings were deposited on Si (100) substrates using pulsed DC magnetron sputtering as a function of Ti metal content. Structural and microstructural characterizations of the as-deposited coatings were carried out using X-ray diffraction and field emission scanning microscopy. Nano-mechanical properties of the coatings were evaluated using nanoindentation, scratch and wear testing techniques. It was observed that nano-hardness and elastic modulus of the coatings decreased with an increase in Ti content. The H/E ratio, an indicator of wear resistance, was found to vary from 0.074 to 0.101 for the coatings with low Ti content. A linear increase in fracture toughness from 1.19 to 2.75 MPam1/2 with increasing Ti content was observed. However, the coating with highest fracture toughness value did not reveal good wear resistance. The coating with a Ti content of 63.3% was found to be optimised for wear resistant applications with a fracture toughness of 2.12 MPam1/2 and nano-hardness of around 17.5 GPa

Ar+H2 plasma etching for improved adhesion of PVD coatings on steel substrates

Ar+H2 plasma cleaning has been described for the surface modification of the steel substrates, which removes oxides and other contaminants from substrate surface effectively leading to a better adhesion of the physical vapor deposited (PVD) coatings. Approximately 1.1-1.3 μm thick TiAlN coatings were deposited on plasma treated (Ar and Ar+H2) and untreated mild steel (MS) substrates. A mechanism has been put forward to explain the effect of plasma treatment on the substrate surface based upon the data obtained from X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM). The XPS measurements on untreated and Ar+H2 plasma etched MS substrates indicated that the untreated substrate surface mainly consisted of Fe3O¬4, whereas, after etching the concentration of oxides decreased considerably. The FESEM and the AFM results showed changes in the surface morphology and an increase in the substrate roughness as a result of Ar+H2 plasma etching. Removal of oxide/contaminants, formation of coarser surface and increased substrate surface roughness as a result of Ar+H2 plasma etching facilitate good mechanical interlocking at the substrate surface, leading to a better adhesion of the deposited PVD coatings. The adhesion of TiAlN coating could be increased further by incorporating a very thin Ti interlayer

Performance evaluation of pulsed sputter deposited nanostructured TiAlN coated high-speed steel drill bits

We have deposited nanostructured TiAlN coatings on high-speed steel (HSS) drill bits and mild steel substrates using a four-cathode reactive direct current (DC) unbalanced magnetron sputtering system. Asymmetric-bipolar pulsed DC generators have been used to deposit TiAlN coatings from the reactive sputtering of Ti and Al targets in N2+Ar plasma. Various treatments have been given to the substrate for improved adhesion of the TiAlN coatings. The process parameters have been optimized to achieve highly adherent good quality TiAlN coatings. These coatings have been characterized using X-ray diffraction, X-ray photoelectron spectroscopy, nanoindentation, atomic force microscopy, wear tester, Potentiodynamic polarization techniques. The performance of the TiAlN coated HSS drill bits is evaluated by drilling a 13 mm thick 304 stainless steel plate, which is considered to be difficult to machine material. The performance evaluation tests have been carried out with and without coolant. The results show significant improvement in the performance of the TiAlN coated HSS drill bits. Furthermore, it has been shown that dry drilling of 304 stainless steel is possible with TiAlN coated HSS drill bits