ASIAN JOURNAL OF PHYSICS

Asian Journal of Physics                                                                                               Vol. 19, Nos. 2 & 3 (2010) 109-124

Soft x-ray multilayer by ion beam sputtering process

 

A Biswas*, D Bhattacharyya and N K Sahoo

Applied Spectroscopy Division, Bhabha Atomic Research Centre, Mumbai – 400 085, India

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An Ion Beam Sputtering system, which uses a commercial ECR microwave based plasma ion source, has been fabricated indigenously for deposition of W/Si soft X-ray multilayer devices. Initially, W, Si single layer thin films and W/Si/W tri-layer samples have been deposited on c-Si substrates at different Ar+ ion energies. The films have been characterized by specular and diffused Grazing Incidence X-ray Reflectivity (GIXR) and Spectroscopic Ellipsometry (SE) techniques to find out thickness and roughness of the individual layers for the single layer samples and interface roughness and interface diffusion for the tri-layer samples. Finally with the optimized ion energy, several W/Si multilayer devices upto 25-layer have been fabricated for application in soft X-ray wavelength < 150 Å and for 30º grazing angle of incidence and have been characterised.

Keywords: IBS, GIXR, SE

Total Refs : 42

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Asian Journal of Physics                                                                                               Vol. 19, Nos. 2 & 3 (2010) 125-140

Optical properties and microstructure evolution in electron beam co-deposited

composite hafnia-silica thin films

N K Sahoo, N M Kamble, R B Tokas, S Thakur and A Biswas

Applied Spectroscopy Division, Bhabha Atomic Research Centre

 Trombay, Mumbai 400 085, India

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Composite hafnia-silica thin-films have generated significant interests for the applications pertaining to the development of multilayer high energy laser damage threshold multilayer coatings and high-k gate oxides. In this work, the optical and microstructural properties of these vapour phase mixed composite thin films achieved through reactive electron beam co-depositions were probed by various techniques, viz., ellipsometry, grazing incidence X-ray reflectivity (GIXR), X-ray diffraction (XRD), atomic force microscopy (AFM) and atomic force acoustic microscopy (AFAM). In spite of different methodologies adopted in these techniques, the optical and microstructural information obtained through measurements have stunning resemblances. It was distinctly observed that by adding a small fraction of silica (5-15%), it is possible to dramatically improve the optical properties, density, grain structure and morphologies in the composite oxide thin films enhancing its application domain in multilayer and semiconductor devices.

Total Refs : 33

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Asian Journal of Physics                                                                                               Vol. 19, Nos. 2 & 3 (2010) 141-146

Annealing effects on structural and electrical properties of Fe/Si interface

Chhagan Lal, Renu Dhunna and I P Jain

Centre for Non-conventional Energy Resources, University of Rajasthan, Jaipur, 302004, India

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Fe films of 80 nm thickness were deposited onto Si (111) substrate using electron beam evaporation technique at 2 × 10–7 torr vacuum. Samples were annealed in 3 × 10–5 torr vacuum at 500 and 600 °C temperatures for one hour for the formation of silicide phases. GIXRD results have revealed the formation a stable FeSi2 disilicide at the interface on annealing at 600 °C temperature. The Schottky Barrier Height (SBH) is calculated from I-V curves and Norde method [F(V)-V]. It is concluded that the SBH decreases with increasing the annealing temperature.

Total Refs : 36

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Asian Journal of Physics                                                                                                Vol. 19, Nos. 2 & 3 (2010)147-154

The growth and electrochemical properties of rf sputtered LiCoO2 thin film cathodes 

P Jeevan Kumar, K Jayanth Babu and O M Hussain*

Thin Film Laboratory, Department of Physics, Sri Venkateswara University, Tirupati-517 502, India

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Thin films of LiCoO2 were grown by rf magnetron sputtering technique and the influence of deposition conditions on the growth, microstructural and electrochemical performance was studied. The LiCoO2 films deposited on metalized silicon substrates maintained at 523 K in an oxygen to argon ratio of 1:9 and subsequently annealed at 923 K exhibited (104) out of plane texture representing R3m structural symmetry with an average grain size of 500 nm. The Chronopotentiometry test performed on Pt/LiCoO2 aqueous cell with a current density of 160 µA/cm2 showed a discharge capacity of 113 µAh/cm2. Cyclic Voltammogram comprises of perfectly redox peaks at certainly very near voltage regions determines no drift in peak voltage and no change in internal resistance. These sputtered LiCoO2 films exhibited excellent electrochemical reversibility and can be used as a binder free cathode material in the fabrication of all solid state microbatteries. Total Refs : 22

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Asian Journal of Physics                                                                                               Vol. 19, Nos. 2 & 3 (2010) 155-186

Ion beam modification of magnetic thin films grown by physical vapour deposition technique

J K Tripathi^1,5, Sanjukta Ghosh^1,6, Maciej Oskar Liedke², A Kanjilal², B Satpati³, A Gupta⁴, and T Som¹, 

¹Institute of Physics, Sachivalaya Marg, Bhubaneswar-751 005, India

²Institute of Ion Beam Physics and Materials Research, Forschungszentrum Dresden-Rossendorf,

 P.O. Box 510119, 01314 Dresden, Germany

³Center for Advanced Material Processing, Central Mechanical Engineering Research Institute,

 Mahatma Gandhi Avenue, Durgapur - 713 209, India

⁴UGC-DAE Consortium for Scientific Research, Khandwa Road, Indore – 452 017, India

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This review reports on the changes in structural and magnetic properties of Pt/Cr/Co multilayers and Co/Pt bi- and multi-layers modified under wide range of ion-energy, -species, and -fluences. We observe irradiation induced CoCrPt ternary alloy phase formation and CoPt ordered/disordered phase formation for Pt/Cr/Co and Co/Pt system, respectively. Phase formation is accompanied by an enhancement in the coercivity. These findings are explained in the light of ion beam induced recoil mixing and ionization events using TRIDYN_FZD and Monte Carlo SRIM simulations.

Keywords: Pt/Cr/Co multilayer, Co/Pt thin films, magnetic property, ion irradiation, coercivity, RBS

PACS: 61.80.Ac, 61.80.Jh, 75.70.Cn, 61.72.Cc, 82.80.Yc; 75.60.-d         

Total Refs : 116

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Asian Journal of Physics                                                                                               Vol. 19, Nos. 2 & 3 (2010) 187-194

Thermally evaporated copper phthalocyanine films for photovoltaic applications

R K Bedi, Himani Gupta, Rajan Saini and Aman Mahajan

¹Material Science Laboratory, Department of Physics,Guru Nanak Dev University, Amritsar-143 005, India

²Department of Applied Sciences, Amritsar College of Engineering & Technology,
Amritsar-143 005, India

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Copper phthalocyanine (CuPc) films have been prepared using thermal evaporation technique onto glass substrate under different experimental conditions. The samples have been studied for their structural, optical and electrical properties. The X-ray diffraction and SEM studies of these films show their crystalline behaviour. The activation energy of the films found to lie in 0.44 – 0.85 eV. Analysis of optical absorption measurements on the films indicates that the interband transitions energies lie in 4.12 – 4.14 eV. Devices have been fabricated under different experimental conditions. The J-V relationship of single layer (Fluorine doped tin oxide/CuPc/Aluminium) and double layer (Fluorine doped tin oxide/Crystal violet/CuPc/Aluminium) devices are found to be in good agreement with standard diode equation. The double layer devices show comparatively higher power conversion efficiency.

Total Refs : 17

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Asian Journal of Physics                                                                                              Vol. 19, Nos. 2 & 3, (2010) 195-208

Effect of thermal oxidation temperature on electrical properties of

amorphous rutile TiO2 thin films

P Chowdhury*, Harish C Barshilia, K C Yogananda, and K S Rajam, Ayan Roy Chaudhuri and S B Krupanidhi

Surface Engineering Division, National Aerospace Laboratories, Bangalore-560 017, India

Material Research Center, Indian Institute of Science, Bangalore-560 012, India

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Amorphous TiO2 thin films were grown by thermal oxidation of sputter deposited Ti thin films on n-type Si(100) substrates. Phase purity of TiO2 thin films was confirmed by X-ray diffraction and Raman spectroscopy. Secondary ion mass spectroscopy depth profiles for the TiO2 thin films demonstrate uniformity of Ti and O atoms and the inter-facial composition on Si surface. Metal oxide semiconductor capacitors with Al top and bottom electrodes were fabricated and both C-V and I-V characterization were carried out to evaluate the effect of thermal oxidation temperature on electrical properties of TiO2 thin films. High temperature annealing at different temperatures from 480 to 740°C under O2 ambient indicates that films oxidized at 580°C have low trap and leakage current densities and can be treated as the optimal oxidation temperature. Frenkel-Poole conduction was observed for films prepared under optimal conditions, while for other conditions, Schottkey emission was found to be the main conduction mechanism.

Total Refs : 26

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Asian Journal of Physics                                                                                               Vol. 19, Nos. 2 & 3 (2010) 209-216

Role of central metal atom and chemisorbed oxygen in gas sensing mechanism for

cobalt-phthalocyanine thin films

Arvind Kumar, Ajay Singh, A K Debnath, Soumen Samanta, D K Aswal, S K Gupta and J V Yakhmi

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

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Chlorine (Cl₂) gas sensing has been studied in polycrystalline cobalt phthalocyanine (CoPc) thin films grown on sapphire substrate by molecular beam epitaxy (MBE). By comparing the gas sensitivity (at room temperature) in ambient and after annealing the films under argon atmosphere we demonstrate that after desorption of chemisorbed oxygen, the gas sensitivity strongly enhances. The chemical interaction between Cl₂ gas and CoPc has been investigated by x-ray photoelectron spectroscopy, UV-visible spectroscopy and impedance spectroscopy. It has been shown that central metal atom of the CoPc molecules at the grain boundaries is primarily responsible for oxidation on exposure to Cl₂.

Total Refs : 21

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Asian Journal of Physics                                                                                              Vol. 19, Nos. 2 & 3 (2010)  217-222

Effect of interface structures on the growth of Ag on Si(111) surfaces

 

Dipak K Goswami

Indian Institute of Technology Guwahati, Guwahati - 781 039, India

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Thin Ag films of different thicknesses are grown on Si(111)-(7 × 7) surfaces at room temperature and then annealed at 700ºC for 5 minutes. Ag films morphology evolution upon annealing has been investigated by scanning tunneling microscopy and interface structures are characterized by reflection high energy electron diffraction studies. Here we report the effect of interface structures on the growth of Ag films.Ag islands formed on Si(111)-(7×7) surfaces at room temperature with strongly preferred heights of even atomic layers keeping (7× 7) reconstructed structure at the buried interface unaltered. However, upon annealing interface structures changes to (1 × 1) and Ag layer with single atomic layer heights following the Si steps are observed.

Total Refs : 27

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Asian Journal of Physics                                                                                               Vol. 19, Nos. 2 & 3 (2010) 223-232

ECR plasma assisted growth of metal oxide nanoparticles

Avinash S Bansode¹, K R Patil², S V Bhoraskar¹ and V L Mathe¹

¹Department of Physics, University of Pune, Pune-411 007, India

²National Chemical Laboratory, Pune-411 008, India

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A new method of synthesizing nanocrystalline particles of metal oxides on a flat substrate by using chemical sputtering assisted by ECR plasma has been explored. Langmuir double Probe method is used to carry out the plasma diagnosis. Nanocrystalline particles of titanium dioxide and iron oxide were grown on the glass substrate by depositing the metals by ECR plasma and then oxidizing them at room temperature. Nanocrystallites were seen to have different facetting depending on the deposition conditions. Structural and morphological analyses were carried out for understanding the characteristic properties. 

Total Refs : 22

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