ASIAN JOURNAL OF PHYSICS

Asian Journal of Physics                                                                                               Vol. 19, Nos. 2 & 3 (2010) 233-238

Thin film of ternary transition metals in alloy form: Path to achieve very low vacuum

 R K Sharma, Jagannath, Sovit Bhattacharya, S C Gadkari, R Mukund and V K Handu

Technical Physics Division, Bhabha Atomic Research Centre , Mumbai-400 085, India

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Non evaporable getter (NEG) thin film of TiVZr were deposited by sputtering on ss substrates. After characterizing with surface techniques, activation temperature of this alloy has been found in the range of 160 – 180°C for 2 hrs heating with well defined composition range. In this paper characterization of the activation behavior of the NEG film has been reported. X-ray Photoelectron Spectroscopy (XPS) technique provides the evolution of the chemical composition of surfaces. TiVZr NEG films were deposited by magnetron sputtering from a single TiZrV target. The NEG performance and morphology dependence on deposition pressure, sputtering conditions, and substrate surface roughness have been investigated. Change in the surface morphology is depicted by Scanning Electron Spectroscopy. Energy dispersive X-ray spectroscopy provides the stoichiometry of the surfaces. However, film topography and density were shown to depend very much on the substrate surface roughness. 

Total Refs : 10

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Asian Journal of Physics                                                                                               Vol. 19, Nos. 2 & 3 (2010) 239-244

Effect of thermal annealing on the formation of silicon nanoclusters in SiOX films grown by PLD

Nupur Saxena^†, A Agarwal^† and D Kanjilal⁺

^†Department of Physics, Bareilly College, Bareilly-243 005, India.

⁺Inter University Accelerator Center, Aruna Asaf Ali Marg, New Delhi - 110 067, India.

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Silicon nanoclusters formation in pulsed laser deposited (PLD) silicon suboxide (SiOX) films by thermal annealing is reported. The SiOX films are prepared by ablation of silicon target at different oxygen partial pressures. The different deposition conditions are employed to study the effect of oxygen concentration on the size of the nanoclusters. Post deposition thermal annealing of the films leads to the phase separation in silicon suboxide films. Fourier transform infrared spectroscopy (FTIR), micro Raman spectroscopy and UV-Vis absorption spectroscopy studies were carried out to characterize the formation of silicon nanoclusters in SiOX films.  

Total Refs : 24

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Asian Journal of Physics                                                                                                Vol. 19, Nos. 2 & 3 (2010)245-262

Thickness and iodization time dependence of photoluminescence in ultrathin Ag films

M Gnanavel and C S Sunandana

School of Physics, University of Hyderabad, Hyderabad-500 046, India

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Silver thin films in the thickness range 5-15 nm prepared by vacuum thermal evaporation onto glass substrates were systematically iodized and carefully characterized by XRD, AFM, UV/Visible optical absorption and photoluminescence. While the un-iodized Ag films are X-ray quasi amorphous in keeping with their quasi-continuous nature and 2D islanded structure, briefly iodized (5-60 minutes) 5, 10, and 15 nm films showed phases characteristic of both g (zincblende) and b (Wurtzite) structures perhaps due to local iodine excess [(Ag/I) < 1] of silver iodide island nanoparticles. Most interestingly, DFM image of as deposited Ag films revealed uniform spherical shaped average particles of 25 nm whose size and shape change appreciably upon iodization. Optical absorption spectra of uniodized Ag films show surface plasmon resonance (SPR) features with SPR peak maxima at 430, 439 and 457 nm for the films of thickness 5, 10 and15 nm, respectively. Finally an interesting and unique surface plasmon-exciton phase transition is observed as the ultra-thin films are progressively iodized at 60 minutes. Red shift observed with increasing iodization time and films thickness which could be the effect of increasing particle size thereby weak quantum confinement effects shows the decreases in the band gap. Photoluminescence of these films are essentially excitonic assisted by donor-acceptor recombination with rates enhanced by thickness and particle size reduction also indicating formation of intrinsic Frenkel defects.  

Total Refs : 80

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Asian Journal of Physics                                                                                               Vol. 19, Nos. 2 & 3 (2010) 263-268

Fabrication and characterization of p-NiO-n-ITO transparent

p-n junction thin film nanostructures

 

B V Mistry^†, P Bhatt^#, K H Bhavsar^†, S J Trivedi^†, U N. Trivedi^# and U S Joshi^†

^†Department of Physics, School of Sciences, Gujarat University, Ahmedabad-380 009, India

^#Department of Instrumentation & Control, Vishwakarma Government Engineering College

 Chandkheda, Gandhinagar-382 424, India

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We have grown "all oxide" transparent p-n junction thin film nanostructure device by using chemical solution deposition (CSD) and e-beam evaporation onto SiO2 substrate. The oxide p-n junction consisting of p-NiO and n-ITO was characterized by GIXRD, AFM, UV-Vis. spectroscopy and I-V measurements. Combined GIXRD and AFM confirm phase pure, mono-disperse 30 nm NiO and ITO nanocrystallites. Better than 70% optical transparency is achieved across 160 nm thick p-n junction. The optical band gap across the junction was found to decrease as compare to the intrinsic ITO and NiO. The current voltage (I-V) characteristics show rectifying nature with dynamic transfer resistance ratio of the order of 103 in the forward bias condition. Very small reverse leakage current with appreciable beakdown was observed under the reverse bias. The observed optical and electrical properties of oxide transparent diode are attributed to the heteroepitaxial nature and carrier diffusion at the junction interface.

Total Refs : 27

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Asian Journal of Physics                                                                                               Vol. 19, Nos. 2 & 3 (2010) 269-272

ZnO Nanocrystals: Magnetic Study

 

S Majumdera, V Solanki^a, A Gupta^b and Shikha Varma^a

^aInstitute of Physics, Bhubaneswar – 751 005, India

^bUGC-DAE CSR, Indore Centre, Indore, India.

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The present study shows the presence of room temperature ferromagnetism in undoped ZnO nanostructures. The ZnO nanostructures have been deposited by physical vapor deposition technique. The magnetic results demonstrate the presence of asymmetric Kerr loop. Results also indicate that these nanostructures are semiconductive in nature and show a PL of 376nm. The ferromagnetism observed in these crystals may arise from the oxygen vacancies at the surface and interfaces. Keywords: AFM, ZnO, MOKE. PACS: 68.37.Ps, 77.55.hj, 75.75.q  

Keywords: AFM, ZnO, MOKE. PACS: 68.37.Ps, 77.55.hj, 75.75.q 

Total Refs : 13

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Asian Journal of Physics                                                                                                       Vol. 19, No. 2 (2010) 273-278

Investigation of SnO2 nanowire based gas sensors

Niranjan Ramgir, Shashwati Sen, Manmeet Kaur, Satyendra Kumar Mishra, Vallabharao Rikka, Rashmi Choukikar and Kunal Muthe

Thin Films and Devices Section, Technical Physics Division,

Bhabha Atomic Research Centre, Trombay, Mumbai 400 085, India 

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Gas sensing characteristics of SnO₂ nanowires in two configurations namely isolated nanowires (Type I) and mat type nanowires thin films (Type II) have been investigated. Interestingly, Type I sensor exhibited anomalous behavior on exposure to Cl₂ in that the resistance reduced on exposure while response of type II sensors showed normal behavior with increase in resistance. Response to reducing gas, H₂S was found to be normal for both type of sensors. Results have been understood in terms of different interactions of chlorine. Temperature dependence of response also showed that maximum response for Type II sensors occurs at 150°C towards both reducing (H₂S) and oxidizing (Cl₂) gases while type I sensors have good response at room temperature. The results indicate different behavior of change in resistance of intragrain and intergrain regions. Isolated SnO₂ nanowires are found to be promising for detection of gases at room temperature. 

Total Refs : 14

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Asian Journal of Physics                                                                                                       Vol. 19, No. 2 (2010) 279-286

Electron field emission from Diamond like carbon films deposited by microwave ECR plasma CVD

S B Singh, P Rai, S A Barve, R Kar, Jagannath, M Pandey, R B Tokas, D S Misra and D S Patil*

¹Laser and Plasma Technology Division,

³Technical Physics Division,

 ⁴High Pressure and Synchrotron Radiation Physics Division,

⁵Applied Spectroscopy Division,

Bhabha Atomic Research Center, Trombay, Mumbai 400 085, India.

²Department of Physics, Indian Institute of Technology, Powai, Mumbai, 400 076.

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Diamond like carbon films (DLC) are deposited on Si (111) substrates by microwave ECR plasma CVD process using plasma of methane and argon gases. A 13.56 MHz RF generator capacitively coupled to a water-cooled substrate holder is used to vary the negative dc self-bias (–25 to –200 V) that is developed on the substrate during deposition. Deposited films were characterized by Raman spectroscopy, X ray photoelectron spectroscopy (XPS) and atomic force microscopy. Field emission characteristics of the deposited films were investigated. Field emission behavior of the deposited films is found to be dependent on the substrate bias during the deposition.  It is also observed that the field emission from the DLC film depends on the sp3/sp2 ratio of carbon bonding, sp2 cluster size and hydrogen content in the film. 

Total Refs : 19 

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Asian Journal of Physics                                                                                                       Vol. 19, No. 2 (2010) 287-300

Magnetron sputtering based x-ray multilayer deposition system at Indus SR facility

M Nayak, P N Rao and G S Lodha

X-ray Optics Section, Indus Synchrotrons Utilization Division, Raja Ramanna
Centre for Advanced Technology, Indore-452013, India

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At Indus synchrotron radiation (SR) facility, we have recently installed a DC/RF magnetron sputtering system, for the development of large area x-ray multilayer (ML) optics. A brief description of the system configuration, automation and operating conditions are presented. The system has the capability of fabricating large area (300 100 mm2) x-ray MLs with required accuracy, uniformity and reproducibility. The sputtering process parameters are optimized for thin film growth, suitable for fabrication of x-ray multilayer optics. The representative results on Mo-Si system are presented. 

Total Refs : 22

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