Dr.Mangalampalli S R N Kiran

Publications

• 4.18

  Impact points

  Effect of dehydration on the mechanical properties of sodium saccharin dihydrate probed with nanoindentation

  M.S.R.N Kiran, S. Varughese, U. Ramamurty, Gautam R. Desiraju

  CrystEngComm. 07/2012; 14(7):2489.

  Nanoindentation is used to explore the variation of mechanical properties associated with the dehydration process in sodium saccharin dihydrate. Upon indenting using a Berkovich tip, (011) and (101) faces exhibit explicit mechanical anisotropy that is consistent with the underlying crystal structure... [more] Nanoindentation is used to explore the variation of mechanical properties associated with the dehydration process in sodium saccharin dihydrate. Upon indenting using a Berkovich tip, (011) and (101) faces exhibit explicit mechanical anisotropy that is consistent with the underlying crystal structure and intermolecular interactions. For freshly grown crystals, (011) is stiffer than (101) by 14%, while (101) is harder than (011) by 8%. Being a heavily hydrated system, the measured mechanical responses contain information pertinent to the fluidity associated with lattice water. Indentation on (011) with a sharp cube-corner tip induces a fluid flow; this observation is uncommon in molecular crystals. The crystals effloresce over a period of time with the generation of a more compact crystal structure and consequently increasing H and E.
• 1.62

  Impact points

  Structure and mechanical properties of Ti-C films deposited using combination of pulsed DC and normal DC magnetron co-sputtering

  K. H. T. Raman, M. S. R. N. Kiran, U. Ramamurty, G. Mohan Rao

  Applied Surface Science. 05/2012;

  Titanium-carbon (Ti-C) thin films of different compositions were prepared by a combination of pulsed DC (for Ti target) and normal DC (for graphite target) magnetron co-sputtering on oxidized silicon and fused quartz substrates. At 33.7 at.% of C content, pure hcp Ti transforms into fcc-TiC with a p... [more] Titanium-carbon (Ti-C) thin films of different compositions were prepared by a combination of pulsed DC (for Ti target) and normal DC (for graphite target) magnetron co-sputtering on oxidized silicon and fused quartz substrates. At 33.7 at.% of C content, pure hcp Ti transforms into fcc-TiC with a preferential orientation of (220) along with (111) and (200). A clear transformation in the preferential orientation from (220) to (111) has been observed when the C content was increased to 56 at.%. At 62.5 at.% of C, TiC precipitates in an amorphous carbon matrix whereas further increase in C leads to X-ray amorphous films. The cross-sectional scanning electron microscope images reveal that the films with low carbon content consists of columnar grains, whereas, randomly oriented grains are in an amorphous carbon matrix at higher carbon content. A dramatic variation was observed in the mechanical properties such as hardness, H, from 30 to 1 GPa and in modulus, E, from 255 to 25 GPa with varying carbon content in the films. Resistance to plastic deformation parameter was observed as 0.417 for films containing 62.5 at. % of C. Nanoscratch test reveals that the films are highly scratch resistant with a coefficient of friction ranging from 0.15 to 0.04.
• 4.37

  Impact points

  Nanoindentation as a Probe for Mechanically Induced Molecular Migration in Layered Organic Donor-Acceptor Complexes

  S. Varughese, M. S. R. N. Kiran, U. Ramamurty, G.R. Desiraju

  Chemistry - An Asian Journal. 04/2012;

  Nanoindentation and scratch experiments on the 1:1 donor-acceptor complexes, 1 and 2, of 1,2,4,5-tetracyanobenzene with pyrene and phenanthrene respectively reveal long-range molecular layer gliding and large interaction anisotropy. Due to the layered arrangements in these crystals, these experiment... [more] Nanoindentation and scratch experiments on the 1:1 donor-acceptor complexes, 1 and 2, of 1,2,4,5-tetracyanobenzene with pyrene and phenanthrene respectively reveal long-range molecular layer gliding and large interaction anisotropy. Due to the layered arrangements in these crystals, these experiments that apply stress in particular directions result in the breaking of interlayer interactions, allowing molecular sheets to glide over one another with ease. Complex 1 has a layered crystal packing wherein the layers are 68o skew under the (002) face and the interlayer space is stabilized with van der Waals interactions. Upon indenting this surface with a Berkovich tip, pile-up of material was observed on just one side of the indenter due to the close angular alignment of the layers with the half angle of the indenter tip (65.35o). The interfacial difference in the elastic modulus (21%) and hardness (16%) demonstrate the anisotropic nature of crystal packing. In 2, the molecular stacks are arranged in a staggered manner; there is no layer arrangement, and the interlayer stabilization involves C–H…N hydrogen bonds and π…π interactions. This results in a higher modulus (20%) for (020) as compared to (001), although the anisotropy in hardness is minimal (4%). The anisotropy within a face was analyzed using AFM image scans and the coefficient of friction of four orthogonal nanoscratches on the cleavage planes of 1 and 2. A higher friction coefficient was obtained for 2 as compared to 1 even in the cleavage direction due to the presence of hydrogen bonds in the interlayer region making the tip movement more hindered.
• 1.82

  Impact points

  Reactive biased target ion beam deposited W-DLC nanocomposite thin films - Microstructure and its mechanical properties

  P. V. Bharathy, Q. Yang, M.S.R.N. Kiran, JongJoo Rha, D. Nataraj, D. Mangalaraj

  Diamond and Related Materials. 01/2012;

  Tungsten incorporated diamond like carbon (W-DLC) nanocomposite thin films with variable fractions of tungsten were deposited by using reactive biased target ion beam deposition technique. The influence of tungsten incorporation on the microstructure, surface topography, mechanical and tribological ... [more] Tungsten incorporated diamond like carbon (W-DLC) nanocomposite thin films with variable fractions of tungsten were deposited by using reactive biased target ion beam deposition technique. The influence of tungsten incorporation on the microstructure, surface topography, mechanical and tribological properties of the DLC were studied using X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, Atomic force microscope (AFM), transmission electron microscopy (TEM), nano-indentation and nano-scratch tests. The amount of W in films gets increases with increasing target bias voltage and most of the incorporated W reacts with carbon to form WC nanoclusters. Using TEM and FFT pattern, it was found that spherical shaped WC nanoclusters were uniformly dispersed in the DLC matrix and attains hexagonal (W2C) crystalline structure at higher W concentration. On the other hand, the incorporation of tungsten led to increase the formation of C-sp2 hybridized bonding in DLC network and which is reflected in the hardness and elastic modulus of W-DLC films. Moreover, W-DLC films shows very low friction coefficient and increased adhesion to the substrate than the DLC film, which could be closely related to its unique nanostructure of the W incorporated thin films.

• Interaction anisotropy and shear instability of aspirin polymorphs established by nanoindentation

  Sunil Varughese, M. S. R . N. Kiran, Katazyna Solonko, Andrew D Bond, U. Ramamurty, Gautam R Desiraju

  Chemical Science (Royal Society of Chemistry). 01/2011; Chemical Science, Vol. 2, pp. 2236-2242, 2011.

  Nanoindentation is applied to the polymorphs of aspirin to examine and differentiate their interaction anisotropy and shear instability. Aspirin provides a key test system for the technique because large single crystals of the metastable polymorph cannot be grown, and because shear instability has b... [more] Nanoindentation is applied to the polymorphs of aspirin to examine and differentiate their interaction anisotropy and shear instability. Aspirin provides a key test system for the technique because large single crystals of the metastable polymorph cannot be grown, and because shear instability has been previously proposed. Different elastic moduli and hardness for the two polymorphs can be correlated with their crystal structures. The stress induced transformation of the metastable polymorph to the stable one, brought about by mechanical milling, proceeds via a slip mechanism. This work demonstrates the potential of nanoindentation to quantify stability relationships and phase transformations in molecular crystals, enabling a deeper understanding of polymorphism in the crystal engineering context.

• Substrate-dependent structure, microstructure, composition and properties of nanostructured TiN films

  M.S.R.N. Kiran, M.Ghanashyam Krishna, K.A.Padmanabhan

  Solid State Communications. 01/2011; 151:561-563.

  Titanium nitride films of thickness of ~ 1.5 µm were deposited on amorphous and crystalline substrates by DC reactive magnetron sputtering at ambient temperature with 100% nitrogen in the sputter gas. The growth of nanostructured, i.e. crystalline nano-grain sized, films at ambient temperature is de... [more] Titanium nitride films of thickness of ~ 1.5 µm were deposited on amorphous and crystalline substrates by DC reactive magnetron sputtering at ambient temperature with 100% nitrogen in the sputter gas. The growth of nanostructured, i.e. crystalline nano-grain sized, films at ambient temperature is demonstrated. The microstructure of the films grown on crystalline substrates reveals a larger grain size/ crystallite size than that of the films deposited on amorphous substrates. Specular reflectance measurements on films deposited on different substrates indicate that the position of the Ti-N 2s band at 2.33 eV is substrate-dependent, indicating substrate-mediated stoichiometry. This clearly demonstrates that not only structure and microstructure, but also chemical composition of the films is substrate-influenced. The films deposited on amorphous substrates display lower hardness and modulus values than the films deposited on crystalline substrates, with the highest value of hardness being 19 GPa on a lanthanum aluminate substrate.

• Bioactivity and mechanical properties of nickel incorporated amorphous hydrogenated carbon thin films prepared by biased target ion beam deposition method

  P. Vijai Bharathy, D. Nataraj, Q. Yang, M. S. R. N. Kiran

  Surfce and Interface Analysis (Wiley CH). 01/2011; DOI 10.1002/sia.3800.

  In this paper, the influence of nickel incorporation on the mechanical properties and the in-vitro bioactivity of hydrogenated carbon thin films were investigated in detail. Amorphous hydrogenated carbon and nickel incorporated hydrogenated carbon (Ni/a-C:H) thin films were deposited onto the Si sub... [more] In this paper, the influence of nickel incorporation on the mechanical properties and the in-vitro bioactivity of hydrogenated carbon thin films were investigated in detail. Amorphous hydrogenated carbon and nickel incorporated hydrogenated carbon (Ni/a-C:H) thin films were deposited onto the Si substrates by using reactive biased target ion beam deposition technique. The films chemical composition, surface roughness, microstructure and mechanical properties were investigated by using XPS, AFM, TEM, nanoindentation and nanoscratch test, respectively. XPS results confirmed that the film surface was mainly composed of nickel, nickel oxide and nickel hydroxide, but at the core, most of the nickel reacted with carbon to form nanocrystalline nickel carbide (Ni3C). The presence of Ni3C in the Ni/a-C:H films has a great influence on the sp2 carbon bonding fraction and therefore the mechanical hardness of the film get greatly reduced. However, Ni/a-C:H films shows very low friction coefficient with higher scratch resistance behaviour than that of pure a-C:H film. In addition to that in-vitro bioactivity study confirms the growth of dense bone-like apatite layer formation on Ni/a-C:H films. These results indicate that the Ni/a-C:H nanocomposite film has great potential and highly suitable for bone related implant coatings.

• Influence of tungsten content in W-DLC nanocomposite thin films prepared by hybrid target biased ion beam assisted deposition technique

  P.V.Bharathy, D.Nataraj, D.Mangalraj, M.S.R.N. Kiran, J.S.Albero, Q.Yang

  International Journal of Nanoscience. 01/2011; Vol. 10, pp. 1-5, 2011.

  Tungsten incorporated diamond like carbon nanocomposite ¯lms were deposited onto Si substrate by using target biased ion beam assisted deposition. The e®ect of W target bias voltage on the chemical bonding, structure, surface morphology and mechanical properties of DLC ¯lms were investigated by mean... [more] Tungsten incorporated diamond like carbon nanocomposite ¯lms were deposited onto Si substrate by using target biased ion beam assisted deposition. The e®ect of W target bias voltage on the chemical bonding, structure, surface morphology and mechanical properties of DLC ¯lms were investigated by means of XPS, Raman spectroscopy, AFM and Nanoindentation. It was found that the content of W in the ¯lms increased from 6 to 13.7 at.% due to the increase in target bias voltage from �300 V to �700 V. XPS analysis revealed that most of the tungsten starts to react with carbon to form WC nanoparticles. Raman analysis shows that with the increase of W fraction in the DLC matrix, the intensity ratio ID/IG increases and the G band shifts to higher wavenumber. Thus it proves that the incorporation of tungsten leads to increase in sp 2 hybridized carbon content, and hence decrease in the hardness of W-DLC ¯lms compared to that of the pure DLC ¯lms. The result of AFM indicates that the surface roughness of the DLC gets modi¯ed with the incorporation of tungsten

• Drug polymorphism: Aspirin headache solved (doi:10.1038/nchem.1186)

  S. Varughese, M. S. R. N. Kiran, K. A. Solonko, A. D. Bond, U. Ramamurty, G. R. Desiraju

  NATURE Chemistry Research Highlights. 01/2011; Vol. 3:p. 835.

  Polymorphism — the existence of different crystal structures of the same compound — is a problem in the pharmaceutical industry, because different polymorphs of the same drug may have different physical properties. Monitoring these subtle differences at each stage of a rigorous production process is... [more] Polymorphism — the existence of different crystal structures of the same compound — is a problem in the pharmaceutical industry, because different polymorphs of the same drug may have different physical properties. Monitoring these subtle differences at each stage of a rigorous production process is a huge expense. Obtaining high-quality crystal structures is not always possible or practical in these circumstances.

• Magnetic and Mechanical Anisotropy in a Manganese 2-Methylsuccinate Framework Structure

  W.Li, T.P.Barto, M.S.R.N. Kiran, R.P.Burwood, U.Ramamurty, Anthony. K. Cheetham

  Chemistry-A European Journal. 01/2011; Vol. 17, pp. 12429- 12436, 2011.

  Hybrid inorganic-organic framework materials exhibit unique properties that can be advantageously tuned through choice of the inorganic and organic components and by control of the crystal structure. We present a new hydrothermally prepared 3D hybrid framework, [Mn(2-methylsuccinate)]n (1), comprisi... [more] Hybrid inorganic-organic framework materials exhibit unique properties that can be advantageously tuned through choice of the inorganic and organic components and by control of the crystal structure. We present a new hydrothermally prepared 3D hybrid framework, [Mn(2-methylsuccinate)]n (1), comprising alternating 2D manganese oxide sheets and isolated MnO6 octahedra, pillared via syn, anti-syn carboxylates. Powder magnetic characterization shows that the compound is a homospin Mn(II) ferrimagnet below 2.4 K. The easy-axis is revealed by single-crystal magnetic studies and a magnetic structure is suggested. Anisotropic elastic modulus and hardness, observed through nanoindentation on differing crystal facets, were correlated with specific structural features. Such measurements of anisotropy are not commonly undertaken, yet allow for a more comprehensive understanding of structure-property relationships.

• Preparation and Nanomechanical Characterisation of Metal Containing Amorphous Hydrogenated Carbon Nanocomposite Films

  P. Vijai Bharathy, D. Nataraj, Q. Yang, D. Mangalaraj, M.S.R.N. Kiran

  , Advanced Materials Research (Trans Tech Publications). 01/2010; 123-125:431-434.

  The relationship between metal-induced chemical bonding and the mechanical properties of Me/a:C-H (Me- Ti and Ni) films are discussed. Nanocomposite films were deposited onto the Si substrates via biased target ion beam sputtering of metal combined with reactive ion beam deposition of a:C-H using CH... [more] The relationship between metal-induced chemical bonding and the mechanical properties of Me/a:C-H (Me- Ti and Ni) films are discussed. Nanocomposite films were deposited onto the Si substrates via biased target ion beam sputtering of metal combined with reactive ion beam deposition of a:C-H using CH4/Ar gas mixture. The chemical composition, microstructure and mechanical properties were characterized using X-ray photoelectron spectroscopy (XPS), Raman spectroscopy and nanoindentation. XPS analysis revealed that both Ti and Ni atoms were preferentially bonded to carbon to form its metal carbide phase. Irrespective of its kind, both the metal carbide clusters induces more graphite like bondings in a:C-H matrix. From the nanoindentation analysis it was found that there is no crack propagation and damage around the indent region even at very high indentation loads. Additionally, it was found that a:C-H film shows higher hardness compared to that of Ti/a:C-H and Ni/a:C-H films.

• Nanomechanical properties of excimer laser nanostructured silicon surfaces

  P. Kumar, M.S.R.N. Kiran

  Science and Technology of Advanced Materials (IOP Science). 01/2010; 11:025003-025010.

  Excimer laser irradiation at ambient temperature has been employed to produce nanostructured silicon surfaces. Nanoindentation was used to investigate the nanomechanical properties of the deformed surfaces as a function of laser parameters, such as the angle of incidence and number of laser pulses a... [more] Excimer laser irradiation at ambient temperature has been employed to produce nanostructured silicon surfaces. Nanoindentation was used to investigate the nanomechanical properties of the deformed surfaces as a function of laser parameters, such as the angle of incidence and number of laser pulses at a fixed laser fluence of 5 J cm−2. A single-crystal silicon [311] surface was severely damaged by laser irradiation and became nanocrystalline with an enhanced porosity. The resulting laser-treated surface consisted of nanometer-sized particles. The pore size was controlled by adjusting the angle of incidence and the number of laser pulses, and varied from nanometers to microns. The extent of nanocrystallinity was large for the surfaces irradiated at a small angle of incidence and by a high number of pulses, as confirmed by x-ray diffraction and Raman spectroscopy. The angle of incidence had a stronger effect on the structure and nanomechanical properties than the number of laser pulses.

• Nanomechanical properties of indium nano/microwires

  P. Kumar, M.S.R.N Kiran

  Nanoscale Research Letters (Spinger Netherlands). 01/2010; 5:1085-1092.

  Nanomechanical properties of indium nanowires like structures fabricated on quartz substrate by trench template technique, measured using nanoindentation. The hardness and elastic modulus of wires were measured and compared with the values of indium thin film. Displacementburst observed while indent... [more] Nanomechanical properties of indium nanowires like structures fabricated on quartz substrate by trench template technique, measured using nanoindentation. The hardness and elastic modulus of wires were measured and compared with the values of indium thin film. Displacementburst observed while indenting the nanowire. `Wire-only hardness' obtained using Korsunsky model from composite hardness. Nanowires have exhibited almost same modulus as indium thin film but considerable changes were observed in hardness value.

• (US PATENT) A process for the development of transparent, large band gap, low refractive index and high temperature stable Titanium Nitride thin film of different compositions for optical and optoelectronic applications.

  Prof. K. A. Padmanabhan, Dr. M. Ghanashyam Krishna, M.S.R.N Kiran

  Ref. No: http://www.wipo.int/pctdb/en/ia.jsp?ia=IN2008%2F000789&IA=IN2008000789&DISPLAY=DESC

  Year: 01/2010

  This invention encompasses the use of titanium nitride (TiNx 0.4_x_0.5) in optical and optoelectronic devices. The thin films are formed by the RF magnetron sputtering process in a pure nitrogen atmosphere at power ranging from 0.5 to 3 Watts/cm2. Thin films are defined as materials with thickness i... [more] This invention encompasses the use of titanium nitride (TiNx 0.4_x_0.5) in optical and optoelectronic devices. The thin films are formed by the RF magnetron sputtering process in a pure nitrogen atmosphere at power ranging from 0.5 to 3 Watts/cm2. Thin films are defined as materials with thickness in the range 10 to 1000 nm. The films can withstand substrate temperatures between ambient temperature and 873 K during deposition and up to 873 K after deposition. The composition is controlled by varying the nitrogen pressure during deposition. The porosity is controlled to achieve almost full theoretical density by changing the gas pressure from 12 to 25 mTorr, the substrate temperature and thickness. These films have high transmission, up to 80%, in the visible region of the spectrum; large band gap (3.7 to 4.5 eV) and refractive index between 1.6 and 1.8 at 600 nm wavelength. These properties are stable up to a temperature of 873 K. These properties make them suitable as one of the layers in Optical interference and Optical band pass filters, UV detectors etc. for space, defense and medical applications. As an example, an optical interference filter consists of alternate high refractive index and low refractive index materials. These compositions are suitable for both types of uses (i.e. high and low index). High temperature stability of the optical properties makes them suitable for high temperature optoelectronic applications. The films can be tailored to exhibit hardness in the range of 5 to 7.5 GPa by varying the gas pressure from 12 to 25 mTorr.

• Structural, optical and nanomechanical properties of (111) oriented nanocrystalline ZnTe thin films

  M.S.R.N Kiran, S.Ksheerasagar, M.Ghanashyam Krishna, S.P.Tewari

  European Physics Journal of Applied Physics (EDP Sciences). 01/2010; 51:10502-9.

  Structural, optical and nanomechanical properties of nanocrystalline Zinc Telluride (ZnTe) films of thickness upto 10 microns deposited at room temperature on borosilicate glass substrates are reported. X-ray diffraction patterns reveal that the films were preferentially oriented along the (1 1 1) d... [more] Structural, optical and nanomechanical properties of nanocrystalline Zinc Telluride (ZnTe) films of thickness upto 10 microns deposited at room temperature on borosilicate glass substrates are reported. X-ray diffraction patterns reveal that the films were preferentially oriented along the (1 1 1) direction. The maximum refractive index of the films was 2.74 at a wavelength of 2000 nm. The optical band gap showed strong thickness dependence. The average film hardness and Young’s modulus obtained from loaddisplacement curves and analyzed by Oliver-Pharr method were 4 and 70 GPa respectively. Hardness of (1 1 1) oriented ZnTe thin films exhibited almost 5 times higher value than bulk. The studies show clearly that the hardness increases with decreasing indentation size, for indents between 30 and 300 nm in depth indicating the existence of indentation size effect. The coefficient of friction for these films as obtained from the nanoscratch test was ∼0.4.

• Investigation of structure and mechanical properties of diamond like carbon thin films incorporated with low content of titanium for biomedical application

  P. Vijai Bharathy, D. Nataraj, Paul K. Chu, Huaiyu Wang, M.S.R.N. Kiran, Q. Yang, D. Mangalaraj, Yin-Yu Chang, Sheng-Min Yang

  Applied Surface Science (Elsevier). 01/2010; 257:143-150.

  Amorphous diamond like carbon (DLC) and titanium incorporated diamond like carbon (Ti-DLC) thin films were deposited by using reactive-biased target ion beam deposition method. The effects of Ti incorporation and target bias voltage on the microstructure and mechanical properties of the as-deposited... [more] Amorphous diamond like carbon (DLC) and titanium incorporated diamond like carbon (Ti-DLC) thin films were deposited by using reactive-biased target ion beam deposition method. The effects of Ti incorporation and target bias voltage on the microstructure and mechanical properties of the as-deposited films were investigated by means of X-ray photoelectron spectroscopy, Raman spectroscopy, transmission electron microscopy and nano-indentation. It was found that the Ti content in Ti-DLC films gets increased with increasing target bias voltage. At about 4.2 at.% of Ti, uniform sized well dispersed nanocrystals were seen in the DLC matrix. Using FFT analysis, a facility available in the TEM, it was found that the nanocrystals are in cubic TiC phase. Though at the core, the incorporated Ti atoms react with carbon to form cubic TiC; most of the surface exposed Ti atoms were found to react with the atmospheric oxygen to form weakly bonded Ti–O. The presence of TiC nanocrystals greatly modified the sp3/sp2 hybridized bonding ratio and is reflected in mechanical hardness of Ti-DLC films. These films were then tested for their biocompatibility by an in vitro cell culturing test. Morphological observation and the cell proliferation test have demonstrated that the human osteoblast cells well attach and proliferate on the surface of Ti incorporated DLC films, suggesting possible applications in bone related implant coatings.

• Studies on sub-stoichiometric and stoichiometric Titanium Nitride thin films

  M.S.R.N Kiran

  01/2009

  Degree: Ph.D

  Supervisor: Dr.M.Ghanashyam Krishna

• Growth, surface morphology, optical properties and electrical resistivity of ε-TiNx (0.4 < x ≤ 0.5) films

  M.S.R.N Kiran, M.Ghanashyam Krishna, K.A.Padmanabhan

  Applied Surface Science (Elsevier). 01/2008; 255:1934-1941.

  The growth, structure, surface morphology, optical properties and electrical resistivity studies on TiNx (0.4 < x ≤ 0.5) films is presented. The films of thickness 116–230 nm were grown on fused silica substrates by RF magnetron sputtering in 100% pure nitrogen atmosphere at ambient temperature a... [more] The growth, structure, surface morphology, optical properties and electrical resistivity studies on TiNx (0.4 < x ≤ 0.5) films is presented. The films of thickness 116–230 nm were grown on fused silica substrates by RF magnetron sputtering in 100% pure nitrogen atmosphere at ambient temperature and pressures from 12 to 25 mTorr. For the as-deposited films, the refractive index decreased from 1.86 to 1.6 with increasing N2 pressure from 12 to 25 mTorr. The absorption edge for the film deposited at 12 mTorr was 4.7 eV and it decreased to 3.5 eV on increasing the N2 pressure to 25 mTorr. Post-deposition annealing of the films at 873 K for 1 min did not cause any variation in the optical properties. The film deposited at 25 mTorr and annealed at 873 K showed a nanocrystalline peak corresponding to var epsilon-Ti2N (3 1 1) with a crystallite size of 60 nm. Surface morphologies varied dramatically with N2 pressure. The electrical resistivity of the film deposited at 12 mTorr was 37 MΩ cm whereas it is 270 kΩ cm for the films deposited at 25 mTorr. Therefore, the current work provides signatures for the var epsilon-Ti2N phase in terms of refractive index, optical absorption edge and electrical resistivity, that can be used to identify the presence of the sub-stoichiometric forms in a TiN film.

• Interfacial engineering of nanostructured Titanium nitride thin films

  M.S.R.N Kiran, M.Ghanashyam Krishna, K.A.Padmanabhan

  International Journal of Nanomanufacturing (Inderscience). 01/2008; 2(5):420-441.

  The properties of TiN films grown on Borosilicate Glass, quartz, MgO (100) and nuclear grade 316LN Stainless Steel (SS) substrates by RF Magnetron sputtering in 100% pure nitrogen plasma are reported. The optical reflectance of the films was 5% on SS 316LN substrates and 35% on glass in the visible ... [more] The properties of TiN films grown on Borosilicate Glass, quartz, MgO (100) and nuclear grade 316LN Stainless Steel (SS) substrates by RF Magnetron sputtering in 100% pure nitrogen plasma are reported. The optical reflectance of the films was 5% on SS 316LN substrates and 35% on glass in the visible region. The colour of the films could be varied from blue to golden yellow through red. It is demonstrated that the titanium and nitrogen reaction is film-substrate interface-dependent. Independent of processing conditions, the films were X-ray amorphous on glass, quartz and MgO substrates. On the SS substrates the films showed a nanocrystallite size of 16 nm at a substrate temperature of 553 K. The crystallite size, even at 623 K, was only 40 nm. The grain size on amorphous substrates decreased with increasing nitrogen pressure, while on crystalline MgO and SS substrates, it showed the reverse trend. Similarly, roughness increased with an increase in working pressure on amorphous substrates, while it decreased with an increase in working pressure on the crystalline substrates.

• Nanomechanical properties of nanocrystalline TiN films on 316LN steel substrates

  M.S.R.N Kiran, M.Ghanashyam Krishna, K. A. Padmanabhan

  Advanced Processing of Novel nanofunctional materials, Dresden Germany; 01/2008

  Titanium nitride (TiN) films have been fabricated on mirror polished 316LN nuclear grade steel substrates by RF magnetron sputtering in 100% nitrogen plasma. The films deposited at 15 mTorr N2 pressure and at different substrate temperatures starting from 300K to 473K. The thicknesses of the films w... [more] Titanium nitride (TiN) films have been fabricated on mirror polished 316LN nuclear grade steel substrates by RF magnetron sputtering in 100% nitrogen plasma. The films deposited at 15 mTorr N2 pressure and at different substrate temperatures starting from 300K to 473K. The thicknesses of the films were varied from 250nm to 650nm with increasing the substrate temperature. The onset of nanocrystallinity i.e. amorphous to nanocrystalline phase in TiN films was observed very clearly on 316LN steel substrates at 423K. Surface roughness and grain size were determined by atomic force microscope. The specular reflectance has been selected as a tool to investigate stoichiometry of the films. Nanoindentation, nanoscratch and wear analysis were performed on these films at ultra low loads to investigate the nanomechanical properties. A very rare correlation between optical and nanomechanical properties was established. In this paper, our result constitutes one of the rare cases in which an Inverse Hall- Petch effect has been observed at room temperature in a ceramic material.