Vol 19 No 2 & 3

Asian

Journal of Physics

____________________________________________________________________________

Volume 19 Numbers 2 & 3 2010

____________________________________________________________________________

Special issue

Physical Deposition of

Thin Films and Nanostructures

Edited By

S K Gupta

Shashwati Sen

In recent years considerable research effort has been focoused on Min films and nanostructures because of new phenomenon displayed by them, as well as their growing applications in electronic, optical, optoelectronic, magnetic. sensor and other devices. Thin films have been at the forefront of techniques that have enabled revolution in electronic device technology and development of nanomaterials is expected to enable continued progress in electronics and other device applications. Importance of thin films and nanomaterials arises from their small size and novel properties arising from reduced dimensionality and their non-equilibrium structures and phases. As an example thin films and superlattices have led to discovery of Giant magnetoresistance (GMR), Tunnel magnetoresistance (TMR) and quantum Hall efect. Of various techniques available for the growth of thin films and nano-structures, physical deposition techniques are of significant importance, as these yield controlled growth of materials with high purity and with possibility of wide variation in growth conditions.

Molecular beam epitaxy is one most important techniques used for the growth of thin films. nanostructures and multilayers. This technique allows acute control over thickness and deposition rate which are important for the growth of high quality heterostructure and quantum devices. Other physical vapour deposition techniques employed for growth of thin films and nanostructures are thermal and e-beam evaporation, sputtering, pulse laser deposition (PLD) and inert gas condensation technique etc.

This special issue of Asian Journal of Physics will focus on Physical deposition of thin films and nano-structures from the point of preparation, characterisation and applications. Characterisation techniques such as atomic force microscopy, transmission electron microscopy, Optical and magnetic characterisation and diverse applications of these materials will be discussed.

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

____________________________________________________________________________________________________________________________________

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

____________________________________________________________________________________________________________________________________

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

____________________________________________________________________________________________________________________________________

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

____________________________________________________________________________________________________________________________________

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

____________________________________________________________________________________________________________________________________

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

____________________________________________________________________________________________________________________________________

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

____________________________________________________________________________________________________________________________________

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

____________________________________________________________________________________________________________________________________

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

____________________________________________________________________________________________________________________________________

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

____________________________________________________________________________________________________________________________________

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

____________________________________________________________________________________________________________________________________

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

____________________________________________________________________________________________________________________________________

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

____________________________________________________________________________________________________________________________________

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

____________________________________________________________________________________________________________________________________

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

____________________________________________________________________________________________________________________________________

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

____________________________________________________________________________________________________________________________________

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

____________________________________________________________________________________________________________________________________

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

____________________________________________________________________________________________________________________________________

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

____________________________________________________________________________________________________________________________________

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

____________________________________________________________________________________________________________________________________

1 2

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

____________________________________________________________________________________________________________________________________

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

____________________________________________________________________________________________________________________________________

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.

____________________________________________________________________________________________________________________________________

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

____________________________________________________________________________________________________________________________________

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

____________________________________________________________________________________________________________________________________

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

____________________________________________________________________________________________________________________________________

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

____________________________________________________________________________________________________________________________________

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

____________________________________________________________________________________________________________________________________

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.

____________________________________________________________________________________________________________________________________

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

____________________________________________________________________________________________________________________________________

Asian Journal of Physics Vol. 19, No. 2 & 3 (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

____________________________________________________________________________________________________________________________________

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

____________________________________________________________________________________________________________________________________

Asian Journal of Physics Vol. 19, No. 2 & 3 (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.

____________________________________________________________________________________________________________________________________

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

____________________________________________________________________________________________________________________________________

Asian Journal of Physics Vol. 19, No. 2 & 3 (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

____________________________________________________________________________________________________________________________________

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

____________________________________________________________________________________________________________________________________

ASIAN JOURNAL OF PHYSICS