Qualification: 
Ph.D
sasangan@amrita.edu

Dr. Sasangan Ramanathan, Dean- Faculty of Engineering and a Professor in the Department of Chemical Engineering and Materials Science, brings with him over 25 years of international research, management and leadership experience. Dr. Ramanathan’s focus and dedication is in preparing the next generation graduates for challenges in Science, Technology, Engineering and Management. He is a strong believer in an educational process that promotes creativity, innovation and entrepreneurship while providing the students with strong fundamentals.

Dr. Ramanathan holds a Ph. D. in Chemical Engineering from Clarkson University (USA) and joined Amrita with a strong background in managing alliances and collaborations with key industry partners/consortia & universities across the globe.

Prior to joining Amrita, he served as the Chief Technology Officer for a large US based semiconductor capital equipment company heading their technology roadmap and strategic business development efforts.

Education

  • 1995: Ph.D. in Chemical Engineering
    Clarkson University, Potsdam, NY, USA
  • 1991: MS in Chemical Engineering
    Clarkson University, Potsdam, NY, USA
  • 1989: B.Tech. in Chemical Engineering
    Regional Engineering College, Trichy

Professional Appointments

Year Affiliation
April 2014 – Present Dean, Faculty of Engineering, Amrita Vishwa Vidyapeetham
Professor, Department of Chemical Engineering and Materials Science, School of Engineering, Amrita Vishwa Vidyapeetham
2008 – 2014 Chief Technology Officer, AIXTRON, Inc., Sunnyvale, CA USA  
2004 – 2008 Vice President, Business Development & Technology, Genus, Inc. USA
2001 – 2004 Director, Technology, Genus, Inc. USA
1999 – 2001 Manager, Process Development, Novellus Systems, Inc. USA
1995 – 1999 Sr. Process Development Engineer, Quester Technology, Inc. USA

Research & Management Experience

  • Has been a significant contributor in defining the technology roadmap for semiconductor capital equipment manufacturers, specifically thin film deposition equipment
  • Demonstrated leadership in product development with special focus in transferring technology & concepts to products
  • Possesses strong fundamental understanding of various thin film deposition techniques - physical vapour deposition, chemical vapour deposition and atomic layer deposition
  • Has initiated and led several industry and academic collaborations to promote advanced semiconductor chip manufacturing
  • Been a significant contributor in various managerial roles spanning from technology and business development, strategic business planning, merger & acquisition and industry-academia partnership
  • Besides the contribution in semiconductor chip manufacturing expert, an excellent materials scientist with significant contribution in developing novel catalyst for shale oil refining, which has led to a boom in the shale oil refining in the US

Major Research Interests

  • Deposition and characterization of materials for advanced CMOS process technology (14nm and beyond)
  • Surface Science and Catalysis
  • Advanced deposition technologies such as Atomic Layer Deposition to “tailor the material properties” for various applications

Membership in Professional Bodies

  1. American Vacuum Society
  2. American Chemical Society
  3. Electrochemical Society

Publications

Publication Type: Patent

Year of Publication Title

2015

W. PARK, Jang, Y. J., Kim, G. Y., Lu, B., Siu, G., Silva, H., and Dr. Sasangan Ramanathan, “Method for Forming TiSiN Thin Film Layer by using Atomic Layer Deposition (Granted)”, U.S. Patent 9159608, US 14/391,2942015.[Abstract]


There is disclosed a method for forming a TiSiN thin film on a substrate according to ALD including a first process of preheating a substrate while supplying Ar or N2 containing inert gas to a chamber, after disposing a substrate in a chamber; a second process of forming a TiN film on the substrate by repeating at least one time a process of purging over-supplied Ti containing gas after supplying Ti containing gas and inert gas after that and a process of purging residual product after supplying N containing gas and inert gas after that; a third process of forming a SiN film by repeating at least one time a process of purging over-supplied Si containing gas after supplying Si containing gas on the TiN film and supplying inert gas after that and a process of purging residual product after supplying N containing gas and supplying inert gas after that; and a fourth process of forming a TiSiN film having a desired thickness by repeating the second and third processes at least one time, a partial pressure range of the gas used in forming the TiSiN thin film is Ti containing gas: 9×10−3 Torr or less, Si containing gas: 1×10−3˜3×10−1 Torr and N containing gas: 7×10−3˜6×10−1 Torr, and a pressure range of the gas is 500 mTorr˜5 Torr and the Si content of the formed TiSiN thin film is 20 atom % or less.

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PDF iconmethod-for-forming-tisin-thin-film-layer-by-using-atomic-layer-deposition.pdf

2011

Kim G. Y., Srivastava A., Seidel T. E., Londergan A. R., and Dr. Sasangan Ramanathan, “Transient Enhanced Atomic layer Deposition (Granted)”, U.S. Patent 79814732011.[Abstract]


A method of enhanced atomic layer deposition is described. In an embodiment, the enhancement is the use of plasma. Plasma begins prior to flowing a second precursor into the chamber. The second precursor reacts with a prior precursor to deposit a layer on the substrate. In an embodiment, the layer includes at least one element from each of the first and second precursors. In an embodiment, the layer is TaN. In an embodiment, the precursors are TaF5 and NH3. In an embodiment, the plasma begins during the purge gas flow between the pulse of first precursor and the pulse of second precursor. In an embodiment, the enhancement is thermal energy. In an embodiment, the thermal energy is greater than generally accepted for ALD (>300 degrees Celsius). The enhancement assists the reaction of the precursors to deposit a layer on a substrate.

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2005

J. Puchacz, Dr. Sasangan Ramanathan, Reyes, M., and Seidel, T., “Multi-single Wafer Processing Apparatus (Filed)”, U.S. Patent File Number 20060137609, US 11/224,7672005.[Abstract]


A wafer processing apparatus includes one or more processing modules, each having multiple, distinct, single-wafer processing reactors configured for semi-independent ALD and/or CVD film deposition therein; a robotic central wafer handler configured to provide wafers to and accept wafers from each of said wafer processing modules; and a single-wafer loading and unloading mechanism that includes a loading and unloading port and a mini-environment coupling the loading and unloading port to the robotic central wafer handler. The wafer processing reactors may be arranged (i) along axes of a Cartesian coordinate system, or (ii) in quadrants defined by said axes, one axis being parallel to a wafer input plane of the at least one of the process modules to which the single-wafer processing reactors belong. Each processing module can include up to four single-wafer processing reactors, each with an independent gas distribution module.

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PDF iconmulti-single-wafer-processing-apparatus.pdf

2005

S. Gopinath, Van Cleemput, P. A., Schulberg, M., Dr. Sasangan Ramanathan, Juarez, F., and Joyce, P., “Method and Apparatus for Introduction of Solid Precursors and Reactants into a Supercritical Fluid Reactor (Granted)”, U.S. Patent US Patent, 6951765, US 10/016,0172005.[Abstract]


The present invention pertains to apparatus and methods for introduction of solid precursors and reactants into a supercritical fluid reactor. Solids are dissolved in supercritical fluid solvents in generator apparatus separate from the supercritical fluid reactor. Such apparatus preferably generate saturated solutions of solid precursors via recirculation of supercritical fluids through a vessel containing the solid precursors. Supercritical solutions of the solids are introduced into the reactor, which itself is charged with a supercritical fluid. Supercritical conditions are maintained during the delivery of the dissolved precursor to the reactor. Recirculation of supercritical precursor solutions through the reactor may or may not be implemented in methods of the invention. Methods of the invention are particularly well suited for integrated circuit fabrication, where films are deposited on wafers under supercritical conditions.

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PDF iconmethod-and-apparatus-for-introduction-of-solid-precursors-and-reactants-into-a-supercritical-fluid-reactor.pdf

2005

S. H. Lee and Dr. Sasangan Ramanathan, “Method for the Formation of Diffusion Barrier (Granted)”, U.S. Patent 6887781, US 10/425,3062005.[Abstract]


Electronic components such as semiconductor wafer VLSI and ULSI integrated circuit devices are provided having a robust barrier layer in the device interconnects. The robust barrier layer provides excellent step coverage, low resistance and enhanced adhesion to CVD copper and the interconnect has a double structure of a layer of a barrier material and a metal layer thereon. The metal layer is preferably tungsten and is formed by replacing silicon or other such atoms on the surface of the barrier layer with tungsten metal. A layer of silicon can be formed on the barrier layer, silicon atoms can be formed on the surface by reacting the barrier layer with a silicon containing reactant or a silicon containing barrier layer can be used.

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PDF iconmethod-for-the-formation-of-diffusion-barrier.pdf

2004

X. Liu, Seidel, T., Lee, E., Doering, K., and Dr. Sasangan Ramanathan, “Methods and Apparatus for Cycle Time Improvements for Atomic Layer Deposition (Filed)”, U.S. Patent File Number 20050016956, 2004.[Abstract]


Different periods of an ALD cycle are performed using different purge flows and, in some cases, different pumping capacities, while maintaining the reactor chamber at a nominally constant pressure. The purge flows may, in some cases, utilize different gasses and/or may be provided through different flow paths. These operations provide for ALD cycle time improvements and economical operation with respect to consumables usage. In some embodiments the use of an annular throttle valve provides a means for controlling downstream flow limiting conductances in a gas flow path from the reactor chamber.

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PDF iconmethods-and-apparatus-for-cycle-time-improvements-for-atomic-layer-deposition.pdf

2004

A. R. Londergan, Dr. Sasangan Ramanathan, Winkler, J., and Seidel, T. E., “Passivation Method for Improved Uniformity and Repeatability for Atomic Layer Deposition and Chemical Vapor Deposition (Granted)”, U.S. Patent 6720259, US 10/262,9922004.[Abstract]


A method to deposit a passivating layer of a first material on an interior reactor surface of a cold or warm wall reactor, in which the first material is non-reactive with one or more precursor used to form a second materials. Subsequently when a film layer is deposited on a substrate by subjecting the substrate to the one or more precursors, in which at least one precursor has a low vapor pressure, uniformity and repeatability is improved by the passivation layer.

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PDF iconpassivation-method-for-improved-uniformity-and-repeatability-for-atomic-layer-deposition-and-chemical-vapor-deposition.pdf

2003

J. Dalton, Powell, R. A., Kailasam, S. K., and Dr. Sasangan Ramanathan, “Formation of Metal-derived Layers by Simultaneous Deposition and Evaporation of Metal (Granted)”, U.S. Patent 65898872003.[Abstract]


The present invention pertains to methods for forming metal-derived layers on substrates. Preferred methods apply to integrated circuit fabrication. In particular, selective methods may be used to form diffusion barriers on partially fabricated integrated circuits. In one preferred method, a wafer is heated and exposed to a metal vapor. Under specific conditions, the metal vapor reacts with dielectric surfaces to form a diffusion barrier, but does not react with metal surfaces. Thus, methods of the invention form diffusion barriers that selectively protect dielectric surfaces but leave metal surfaces free of diffusion barrier.

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PDF iconforming-metal-derived-layers-by-simultaneous-deposition-and-evaporation-of-metal.pdf

2000

S. Sengupta, Stowell, S., Sengupta, L., Joshi, P. C., Dr. Sasangan Ramanathan, and Desu, S. B., “Ferroelectric Thin Film Composites made by Metalorganic Decomposition (Granted)”, U.S. Patent US Patent, 60715552000.[Abstract]


Thin films of ferroelectric composite material comprising barium strontium titanate (BSTO) combined with magnesium oxide additive are produced by metalorganic decomposition. The barium strontium titanate magnesium oxide ferroelectric composite comprises Ba1-x Srx TiO3 /MgO, wherein x is greater than 0.0 but less than or equal to 0.75 and preferably is 0.4, and wherein the weight ratio of BSTO to magnesium oxide may range from 99 to 40 weight percent BSTO to 1 to 60 weight percent magnesium oxide. These films have desirable electronic properties and may have application to both active microwave and dynamic random access memory devices, including low dielectric constant, low loss factor, high tunability, and high resistivity. The films produced are uniformly thick and impurity free, with thicknesses of only 0.4 microns.

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2000

Dr. Sasangan Ramanathan, Khan A., and Foggiato G. A., “Surface Modification of Semiconductors using Electromagnetic Radiation (Granted)”, U.S. Patent 60157592000.[Abstract]


Deposition rates of undoped silicate glass dielectric layers on thermal oxide are increased by pre-treating the thermal oxide layer With electromagnetic radiation in the ultraviolet (UV) and/or vacuum ultraviolet (VUV) Wavelengths. The surface smoothness of the resulting ?lms are also increased by pre-treating ?lms With UV and/or VUV radiation. Furthermore, the gap ?lling abilities of the undoped silicate glass ?lms are increased by pre-treating the thermal oxide With UV and/or VUV radiation. NeW equipment and meth ods are presented for exposing semiconductor devices to UV and/or VUV radiation, and for enhancing the deposition rates and ?lm quality for semiconductor manufacture. Semi conductor devices incorporating the neW methods are also described.

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PDF iconsurface-modification-of-semiconductors-using-electromagnetic-radiation.pdf

1999

Dr. Sasangan Ramanathan, Desu S. B., and Suchicital C.A., “Flash Evaporator (Granted)”, 1999.[Abstract]


A device and method for ?ash evaporating a reagent includes an evaporation chamber that' houses a dome ~on WhlCh evaporation occurs. The dome is solid and of high thermal conductivity and mass, and may be heated to a temperature suf?cient to vaporize a speci?c reagent. The reagent is supplied from an external source to the dome through a noZZle, and may be supplied as a continuous Stream, as a Shower, and as discrete drops_ Acarrier gas may be introduced into the evaporation Chamber and Create a vortex ?ow therewithin, After evaporation, the gas vapor may be removed from the evaporation chamber through a regulating valve to a reaction chamber. Another embodiment of the invention includes a plurality of evaporating domes that separately receive reagent, and may receive reagents of differing composition.

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PDF iconflash-evaporator.pdf

Publication Type: Conference Proceedings

Year of Publication Title

2013

Dr. Sasangan Ramanathan, “Atomic Layer Deposition of Materials for Alternate Non-Volatile Memory Technologies”, Invited Talk at the 13th Atomic Layer Deposition Conference, American Vacuum Society. 2013.

2012

L. Yang, Weber, U., Maumann, P. K., Karim, Z., Dr. Sasangan Ramanathan, Lu, B., Czubatyj, W., Hudgens, S., and Lowrey, T., “Deposition and Electrical Characterization of ALD GexSbyTez for Future Applications”, 12th International Conference on Atomic Layer Deposition, American Vacuum Society. 2012.

2012

Z. Karim, Yang, L., Mack, J., Liu, M., Weber, U., Baumann, P., Dr. Sasangan Ramanathan, Lu, B., Czubatyj, W., Hudgens, S., and , “Advances in ALD GST Process and Equipment for sub-20nm PCRAM Devices: Precursor delivery, GST Gapfill and Electrical Characterization”, Conference Proceedings by the Society for Solid State and Electrochemical Science and Technology. The Electrochemical Society, 2012.

2011

L. Yang, Weber, U., Baumann, P. K., Mack, J., Karim, Z., Dr. Sasangan Ramanathan, and Lu, B., “Atomic Layer Deposition of Smooth Phase Change GexSbyTez Layers on Planar and 3D Structures”, International Conference on Atomic Layer Deposition, American Vacuum Society. 2011.

2011

B. Lu, Karim, Z., and Dr. Sasangan Ramanathan, “Material and Tool Design Challenges for Taking ALD to High Volume Production Beyond 30nm Node”, Symposium on Manufacturing and Technology Section MS2, American Vacuum Society. 2011.

2010

P. Lehnen, Weber, U., Baumann, P. K., Senzaki, Y., Karim, Z., Dr. Sasangan Ramanathan, Lu, B., Reed, J., Czubatyj, W., Hudgens, S., and Dennison, C., “Void Free Gapfill and Phase Change Memory Device Characterization of GeSbTe Films Deposited Using Atomic Vapor Deposition”, 10th Atomic Layer Deposition Conference, American Vacuum Society. 2010.

2009

C. Barelli, . Y Kim, H., . Y Kim, G., Senzaki, Y., Okuyama, Y., Mack, J., Lindner, J., Lu, B., Karim, Z., and Dr. Sasangan Ramanathan, “Highly Conformal ALD of LaOx and La-based High-k Dielectric Films Using Novel Vaporizer Technology”, Materials Research Society Spring Meeting. 2009.

2009

Dr. Sasangan Ramanathan, “Development of Next Generation High-k Filmss – Challenges and Solutions”, European Materials Research Society Spring Meeting. France, 2009.

2009

Z. Karim, Senzaki, Y., . Y Kim, G., Barelli, C., Okuyama, Y., Kim, H. Y., Lu, B., Lindner, J., and Dr. Sasangan Ramanathan, “Needs for Next Generation Memory and Enabling Solutions based on Advanced Vaporizer Technology”, 9th Atomic Layer Deposition Conference, American Vacuum Society. 2009.

2008

C. Choi, Ando, T., Karim, Z., and Dr. Sasangan Ramanathan, “Modulating Work Function for pFET with AVD Ru-based and TaN-based Gate Electrodes”, 39th IEEE Semiconductor Interface Specialist Conference. 2008.

2008

Y. Senzaki, Seidel, T., McCormick, J., Kim, G. Y., Kim, H. Y., Karim, Z., Lu, B., Dr. Sasangan Ramanathan, Lindner, J., Silva, H., and Daulesberg, M., “Atomic Level Solutions for Advanced Microelectronic Applications”, International Conference on Solid State and Integrated Circuit Technology, ICSICT 2008. . 2008.[Abstract]


Atomic Layer Deposition (ALD) has successfully been applied to advanced microelectronic applications importantly for conformal coatings on high aspect ratio devices. However, traditional ALD is limited in deposition rate because the ability to bring precursors rapidly to the surface. In this paper we review recent results for precursor delivery using advanced vaporization (Trijet) as well as recent advances in Pulsed CVD (AVD®) using art elements held in common with ALD technology. These and other advances - such as Multiple Single Wafer configurations allow ALD application for continued scaling under conditions of improved process control and higher productivity. Key applications include: capacitors (dielectrics and electrodes), transistors and contacts. This paper reviews these technological advances in the context of their applications.

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PDF iconatomic-level-solutions-for-advanced-microelectronic-applications.pdf

2008

Z. Karim, Senzaki, Y., Dr. Sasangan Ramanathan, Lindner, J., Silva, H., and Dauelsberg, M., “Advances in ALD Equipment for sub-40nm Memory Capacitor Dielectrics: Precursor delivery, Materials and Processes”, ECS Transactions, vol. 16. The Electrochemical Society, pp. 125–134, 2008.[Abstract]


In DRAM, maintaining the cell capacitance more than 25 fF/cell with shrinking cell capacitance area has been accomplished with the introduction of higher k oxides as the capacitor dielectric. Higher k materials include Al2O3, HfO2, ZrO2 or a combination of HfO2/Al2O3/HfO2 and ZrO2/Al2O3/ZrO2. These materials can satisfy DRAM device requirements down to the 50 nm node. However, for sub 40nm DRAM technology nodes, precursor delivery challenges are far greater and require unique precursor delivery methodology to ensure >90% conformality in high aspect ratio DRAM capacitor structures, while maintaining higher productivity. The precursor delivery problem is due to the very low vapor pressures of the precursors for advanced high k dielectrics.. This paper highlights the progress made in ALD equipment development offering solutions for critical problems facing sub 40nm DRAM technology nodes. Particularly, this paper describes a unique pulsed vaporization technology (TriJet®) coupled with a high performance ALD reactor that offers solution for next generation high k film deposition without compromising productivity.

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2006

M. Schumacher, Dr. Sasangan Ramanathan, Baumann, P. K., J. Linder, Lohe, C., Weber, U., Karim, Z., Londergan, A. R., and Seidel, T. E., “Atomic Vapor Deposition for Next Generation of Advanced Semiconductor Devices”, The Electrochemical Society, Meeting Abstracts, vol. 12. p. 487, 2006.

2005

H. J. Lim, Kim, Y. S., Jung, H. S., Han, S. K., Kim, M. J., Lee, J. H., Lee, N. I., Chung, Y., Kim, H. Y., Lee, N. K., Dr. Sasangan Ramanathan, Seidel, T. E., and Boleslawski, M., “Evaluation od ALD Hafnium Silicate and Improvement of Reliability Characteristics”, Atomic Layer Deposition Conference. 2005.

2004

X. Liu, Dr. Sasangan Ramanathan, Lee, E., and Seidel, T. E., “Atomic Layer Deposition of Aluminum Nitride Thin Films from Trimethyl Aluminum (TMA) and Ammonia”, MRS Proceedings. Cambridge Univ Press, pp. 11-18, 2004.[Abstract]


luminum nitride (AlN) thin films were deposited from trimethyl aluminum (TMA) and Ammonia (NH3) by thermal atomic layer deposition (thermal ALD) and plasma enhanced atomic layer deposition (PEALD) on 200 mm silicon wafers. For both thermal ALD and PEALD, the deposition rate increased significantly with the deposition temperature. The deposition rate did not fully saturate even with 10 seconds of NH3 pulse time. Plasma significantly increased the deposition rate of AlN films. A large number of incubation cycles were needed to deposit AlN films on Si wafers. 100% step coverage was achieved on trenches with aspect ratio of 35:1 at 100 nm feature size by thermal ALD. X-ray diffraction (XRD) data showed that the AlN films deposited from 370 °C to 470 °C were polycrystalline. Glancing angle X-ray reflection (XRR) results showed that the RMS roughness of the films increased as the film thickness increased.

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PDF iconatomic-layer-deposition-of-aluminum-nitride-thin-films-from-trimethyl-aluminum-tma-and-ammonia.pdf

2004

Kim G. Y., Srivastava A., Foote D., Londergan A., Karim Z., Seidel T. E., and Dr. Sasangan Ramanathan, “A High Deposition Rate Process Using Limited Optimized Reaction ALD”, Atomic Layer Deposition Conference”, Atomic Layer Deposition Conference, American Vacuum Society. pp. 1308-1311, 2004.

2003

X. Liu, Dr. Sasangan Ramanathan, and Seidel, T. E., “Atomic layer deposition of hafnium oxide thin films from tetrakis (dimethylamino) hafnium (TDMAH) and ozone”, MRS Proceedings. Cambridge Univ Press, pp. 97-102, 2003.[Abstract]


Hafnium oxide (HfO2) thin films were synthesized from tetrakis(dimethylamino) hafnium (TDMAH) and ozone (O3) by atomic layer deposition (ALD) on 200 mm silicon wafers. Gradual saturation was observed for TDMAH exposure pulse. However O3 showed better saturation behavior for O3exposure. Yet, 100% step coverage was achieved for ~100nm trenches with aspect ratio of 35. Temperature dependence of the deposition rate was studied at susceptor temperature from 160°C to 420°C. The lowest deposition rate was observed at 320°C. Mercury probe measurements indicated the dielectric constant increased from 16 to 20 as susceptor temperature increased from 200°C to 320°C. Selected comparisons with tetrakis (ethylmethylamino) hafnium (TEMAH) were also made. More »»

2003

A. R. Londergan, Dr. Sasangan Ramanathan, Winkler, J., Seidel, T. E., Gutt, J., Brown, G., and Murto, R. W., “PATHWAYS FOR ADVANCED TRANSISTORS USING HAFNIUM–BASED OXIDES BY ATOMIC LAYER DEPOSITION”, Electrochemical Society. pp. 243-264, 2003.

2002

Dr. Sasangan Ramanathan, Seidel, T., Londergan, A., Lee, E., and Jansz, A., “Pathways in Competitiveness for Atomic Layer Deposition”, Proceedings of the AVS 3rd International Conference on Microelectronics and Interfaces. pp. 11-14, 2002.

2002

J. H Lee, Kim J., Kim Y. S., S., J. H., Lee, N. I., Kang, H. K., Suh, K. P., Jeong, M. M., Hyun, K., Baik, H. S., Chung, Y. S., Liu, X., Dr. Sasangan Ramanathan, Seidel, T. E., Winkler, J., Londergan, A., Kim, H. Y., M., J., and Lee, N. K., “Mass Production Worthy HfO2-Al2O3 Laminates Capacitor Technology using Hf Liquid Precursor for sub-100 nm DRAMS”, Techincal Digest, International Electron Devices Meeting. pp. 221-224, 2002.

2002

A. Londergan, Dr. Sasangan Ramanathan, Rassiga,, Hinzay, R., Winkler, J., Velasco, H., Matthysse, L., Seidel, T. E., Ang, C. H., Yu, H. Y., and Li, M. F., “Process Optimization in Atomic Layer Deposition of High-k Oxides for Advanced Gate Stack Engineering”, Conference Proceedings, the Society for Solid State and Electrochemical Science and Technology. pp. 163-176, 2002.

1998

S.T.Oyama, Dr. Sasangan Ramanathan, Schwartz, V., and Dhandapani, B., “Synthesis and Reactivity of Niobium Molybdenum Oxycarbide – A New High Activity Hydroprocessing Catalys”, Abstracts of Papers of the American Chemical Society, vol. 215. p. U228, 1998.

Publication Type: Journal Article

Year of Publication Title

2009

Y. Senzaki, Okuyama, Y., Kim, G., Kim, H. Young, Barelli, C., Lindner, J., Karim, Z., and Dr. Sasangan Ramanathan, “Highly Conformal ALD of ZrO2 at Higher Process Temperatures than the Conventinal TEMAZr-Based Process”, ECS Transactions, vol. 25, pp. 201–209, 2009.[Abstract]


An alternative Zr source to tetrakis(ethylmethylamino)zirconium (TEMAZr) was evaluated in this study to develop more thermally robust 300mm ZrO2 ALD process. It was observed that a transition from ALD to CVD takes place at approximately 340åC susceptor temperature. This temperature is significantly higher than that for the commonly used TEMAZr-based ALD process by approximately 40åC. Excellent step coverage of near 100% of ALD ZrO2 has been achieved in 40:1 aspect ratio structures using this new ZrO2 ALD process. ZrO2 ALD films of 5.5nm thickness demonstrated a low leakage current of 2x10-9A/cm2 at 1.2V. More »»

2007

J. Dalton, Kim, H. Young, Zhang, Z., Seidel, T., Karim, Z., and Dr. Sasangan Ramanathan, “High Performance ALD Reactor for High-k Films”, ECS Transactions, vol. 3, pp. 27–36, 2007.[Abstract]


In this work we discuss the design requirements for achieving higher productivity ALD solutions and we present a single-wafer reactor design that incorporates improvement elements. The effectiveness of this approach is evaluated by examining the improved step coverage, saturation, uniformity and electrical properties of ZrO2 high-k films deposited using this reactor system. More »»

2006

Z. Karim, Biossiere, O., Lohe, C., Zhang, Z., Park, W., Manke, C., Baumann, P. K., Dalton, J., Dr. Sasangan Ramanathan, Lindner, J., and , “Advanced Metal Gate Electrode Options Compatible with ALD and AVD® HfSiOx-based Gate Dielectrics”, ECS Transactions, vol. 3, pp. 363–374, 2006.[Abstract]


We have investigated metal gate electrodes for use with high k HfSiOx gate dielectric films using AVD® and ALD technology. First, we report on the characterization of the AVD® and ALD deposition techniques where both HfO2 and SiO2 are combined for the formation of HfSiOx. Nitrogen is then incorporated using both in-situ and ex-situ methods to form HfSiON and the resulting film properties are compared. Using an AVD process a work-function of >4.7eV for Ru and RuO2 gate electrode metals in combination with HfSiOx was obtained. A TaN-based metal gate was also characterized to target a promising pMOS solution using different compositions. Together with its high flexibility and composition control, both ALD and AVD® can become key processes for advanced high-k dielectrics as well as compatible CMOS metal electrodes. More »»

2005

X. Liu, Dr. Sasangan Ramanathan, Longdergan, A., Srivastava, A., Lee, E., Seidel, T. E., Barton, J. T., Pang, D., and Gordon, R. G., “ALD of Hafnium Oxide Thin Films from Tetrakis (ethylmethylamino) Hafnium and Ozone”, Journal of The Electrochemical Society, vol. 152, pp. G213–G219, 2005.[Abstract]


Hafnium oxide (HfO2)(HfO2) thin films were deposited from tetrakis(ethylmethylamino)hafnium (TEMAH) and ozone (O3)(O3) by atomic layer deposition (ALD) on 200 mm silicon wafers. The O3O3 half-reaction shows good saturation behavior. However, gradual surface saturation is observed for the TEMAH half-reaction. Within wafer non-uniformity of less than 1% and step coverage of about 100% were achieved for trenches with aspect ratio of around 40:1. The film thickness increased linearly as the number of cycles increased. From susceptor temperatures of 160-420°C, the lowest deposition rate (Å/cycle) and the highest refractive index is observed at 320°C. The atomic ratio of hafnium to oxygen determined by Rutherford backscattering is 1:2.04 for the films deposited at 320°C. The carbon and hydrogen content determined by secondary ion mass spectroscopy (SIMS) decreased as the susceptor temperature increased from 200 to 320°C. Lower carbon and hydrogen levels were obtained in the control films made with H2OH2O than the films made with O3.O3. A reaction mechanism of the TEMAH+O3TEMAH+O3 ALD process is discussed. The results show that an O3O3 -based ALD HfO2HfO2 deposition is promising for microelectronic applications. © 2005 The Electrochemical Society. All rights reserved.

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PDF iconald-of-hafnium-oxide-thin-films-from-tetrakis-ethylmethylamino-hafnium-and-ozone.pdf

2003

Tom Seidel, Londergan, A., Winkler, J., Liu, X., and Dr. Sasangan Ramanathan, “Progress and Opportunities in Atomic Layer Deposition”, vol. 46, pp. 67-70, 2003.

2002

H. Y. Yu, Wu, N., Li, M. F., Chunxiang Zhu, Byung Jin Cho, Kwong, D. - L., Tung, C. H., Pan, J. S., Chai, J. W., Wang, W. D., Chi, D. Z., Ang, C. H., Zheng, J. Z., and Dr. Sasangan Ramanathan, “Thermal Stability of (HfO2)x(Al2O3)1−x on Si”, Applied Physics Letters, vol. 81, pp. 3618-3620, 2002.[Abstract]


The kinetics of the interfacial layer (IL) growth between Hf aluminates and the Si substrate during high-temperature rapid thermal annealing (RTA) in either N2 (∼10 Torr) or high vacuum (∼2×10−5 Torr) is studied by high-resolution x-ray photoelectron spectroscopy and cross-sectional transmission electron microscopy. The significant difference of the IL growth observed between high vacuum and relatively oxygen-rich N2 annealing (both at 1000 °C) is shown to be caused by the oxygen species from the annealing ambient. Our results also show that Hf aluminates exhibit much stronger resistance to oxygen diffusion than pure HfO2 during RTA in N2 ambient, and the resistance becomes stronger with more Al incorporated into HfO2. This observation is explained by the combined effects of (i) smaller oxygen diffusion coefficient of Al2O3 than HfO2, and (ii) higher crystallization temperature of the Hf aluminates.

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2002

M. F. Li H. Y. Yu, Dr. Sasangan Ramanathan, Cho, B. Jin, Yeo, C. C., Joo, M. S., Kwong, D. - L., Pan, J. S., Ang, C. H., and Zheng, J. Z., “EnergyGap and Band Alignment for (HfO2)x(Al2O3)1−x(HfO2)x(Al2O3)1−x on (100) Si”, Applied Physics Letters , vol. 81, pp. 376-378, 2002.

1999

S. B. Desu, Vijay, D. P., Dr. Sasangan Ramanathan, Bhatt, H. D., and Tirumala, S., “Stresses in Sputtered RuOx Thin Films”, Thin Solid Films, vol. 350, pp. 21 - 29, 1999.[Abstract]


RuOx thin films have been deposited by reactive sputtering in an O2/Ar atmosphere. The films were characterized for their stress and resistivity as a function of deposition temperature (room temperature, 300°C) and the O2 content (25–100%) in the sputtering gas. Additionally, the stresses in these films were determined as a function of annealing temperature (up to 600°C) using an in-situ curvature measurement technique. The as-deposited films were found to be under a state of compressive stress for all deposition conditions. The compressive stresses sharply increased with increasing deposition temperature from a value of around 200 MPa at 200°C to 1400 MPa at 300°C. This dramatic increase has been attributed to differences in microstructure at these deposition temperatures. The microstructural differences also led to the widely differing stress-temperature behavior during annealing of these films. For films deposited at temperatures lower than 200°C, the annealing process resulted in a decrease in the compressive stress and resistivity of the films. However, films deposited at a temperature of 300°C did not show any changes in the compressive stress or resistivity after annealing. The results of this study can be used to deposit RuOx thin films with low resistivity and minimal stresses.

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1999

S. T. Oyama, C. Yu, C., and Dr. Sasangan Ramanathan, “Transition Metal Bimetallic Oxycarbides: Synthesis, Characterization, and Activity Studies”, Journal of Catalysis, vol. 184, pp. 535 - 549, 1999.[Abstract]


A new family of bimetallic oxycarbide compounds MI–MII–O–C (MI=Mo, W; MII=V, Nb, Cr, Fe, Co, Ni) has been synthesized by carburizing bimetallic oxide precursors using a temperature-programmed method. The oxide precursors are prepared by conventional solid-state reaction between two appropriate monometallic oxides. The synthesis involves passing a 20 mol% \{CH4\} in \{H2\} mixture over the oxide precursors while raising the temperature at a linear rate of 8.3×10−2 K s−1 (5 K/min) to a final temperature (Tmax) which is held for a period of time (thold). The synthesis, chemisorption properties, and reactivation of the materials indicate that the compounds can be divided into two groups of different reducibility (high and low). Their surface activity and surface area are evaluated based on \{CO\} chemisorption and \{N2\} physisorption measurements. It is found that the \{CO\} number density correlates with the reducibility of the compounds. The catalysts were evaluated for hydroprocessing in a three-phase trickle-bed reactor operated at 3.1 \{MPa\} and 643 K. The feed was a model liquid mixture containing 3000 ppm sulfur (dibenzothiophene), 2000 ppm nitrogen (quinoline), 500 ppm oxygen (benzofuran), 20 wt% aromatics (tetralin), and balance aliphatics (tetradecane). The bimetallic oxycarbides had moderate activity for \{HDN\} of quinoline, with Nb–Mo–O–C showing higher \{HDN\} than a commercial sulfided Ni–Mo/Al2O3 catalyst tested at the same conditions. X-ray diffraction of the spent catalysts indicated that the oxycarbides of the early transition metals were tolerant of sulfur, while those involving the late transition metals showed bulk sulfide phases. More »»

1998

P. C. Joshi, Dr. Sasangan Ramanathan, Desu, S. B., Stowell, S., and Sengupta, S., “Characterization of Ba0.6Sr0.4TiO3 Thin Films with Mg Additive Fabricated by Metalorganic Decomposition Technique”, Integrated Ferroelectrics, vol. 19, pp. 141-148, 1998.[Abstract]


Abstract We report for the first time Ba0.6Sr0.4TiO3 (BST 60/40) thin films with Mg additive fabricated by Metalorganic decomposition technique on platinum coated silicon substrates using acetate-alkoxide precursors.[1] The structural and electrical properties of the BST thin films were greatly changed by additions of Mg. The surface morphology of the films was smooth with a dense microstructure. The typical small signal dielectric constant and the loss factor for a 0.4 μm thick undoped BST films were 450 and 0.013, respectively, at an applied frequency of 100 kHz. The dielectric loss was significantly reduced by the Mg content. The tunability (ΔC/C0) was found to change from 20.7% to 5.8% as the Mg additive content was changed from 0 to 20 mol%. The films exhibited high resistivity of the order of 1012 Ω-cm even up to an applied electric field of 100 kV/cm.

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1998

Dr. Sasangan Ramanathan, Oyama, S. T., and C., C., “New Catalysts for Hydroprocessing: Bimetallic Oxynitrides MI-MII-O-N (MI, MII= Mo, W, V, Nb, Cr, Mn, and Co) Part II: Reactivity Studies”, Journal of Catalysis, vol. 173, pp. 10-16, 1998.[Abstract]


Bimetallic oxynitrides of the typeMIMIIOxNywere used as catalysts in hydrotreating reactions at 3.1 MPa and 643 K. The catalysts were prepared by nitriding bimetallic oxide precursors, where MoO3or WO3was one of the components, as described in the companion paper. The reactions were studied in a three-phase trickle-bed reactor operated at 3.1 MPa and 643 K. The feed was a model liquid mixture containing 3000 ppm sulfur (dibenzothiophene), 2000 ppm nitrogen (quinoline), 500 ppm oxygen (benzofuran), 20 wt% aromatics (tetralin), and balance aliphatics (tetradecane). The activities of the bimetallic nitrides were compared to a commercial sulfided Ni–Mo/Al2O3catalyst tested at the same conditions. The bimetallic oxynitrides were active for HDN of quinoline with V–Mo–O–N showing higher HDN activity than the commercial sulfided Ni–Mo–S/Al2O3catalyst. The HDS activity of the bimetallic oxynitrides ranged from 9 to 37% with Co–Mo–O–N showing the highest HDS activity among the oxynitrides tested. X-ray diffraction analysis of the spent catalysts indicated that the oxynitrides consisting of early transition metals (Group 4–Group 6) were tolerant of sulfur, while catalysts involving metals of Group 7 and Group 8 showed bulk sulfide phases. X-ray photoelectron spectroscopic analysis of the catalysts before and after the reaction indicated the incorporation of sulfur on the surface of the catalysts after prolonged exposure to the reactants.

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1998

B. Dhandapani, Dr. Sasangan Ramanathan, Yu, C. C., Frühberger, B., Chen, J. G., and Oyama, S. T., “Synthesis, Characterization, and Reactivity Studies of Supported Mo2C with Phosphorus Additive”, Journal of Catalysis, vol. 176, pp. 61 - 67, 1998.[Abstract]


The effect of phosphorus on Mo2C supported on γ-Al2O3and activated carbon was studied. The catalysts were characterized by \{CO\} chemisorption, \{BET\} surface area measurements, X-ray diffraction, X-ray photoelectron spectroscopy, and near-edge X-ray absorption fine structure, and tested for their reactivity for hydroprocessing reactions, particularly hydrogenation, hydrodesulfurization (HDS) and hydrodenitrogenation (HDN), using model liquid compounds. The P-containing catalysts had higher reactivity for \{HDN\} than those without P. \{HDS\} was higher when the Mo2C was synthesized on γ-Al2O3previously treated with P than when the Mo component and P were added together on γ-Al2O3. Postreaction characterization indicates that the catalysts were tolerant of sulfur. More »»

1998

C. C. Yu, Dr. Sasangan Ramanathan, and Oyama, S. T., “New Catalysts for Hydroprocessing: Bimetallic Oxynitrides MI–MII–O–N (MI, MII=Mo, W, V, Nb, Cr, Mn, and Co): Part I. Synthesis and Characterization”, Journal of Catalysis, vol. 173, pp. 1 - 9, 1998.[Abstract]


A new family of bimetallic oxynitride compounds, MI–MII–O–N (MI, MII=Mo, W, V, Nb, Cr, Mn, and Co), has been synthesized by nitriding bimetallic oxide precursors with ammonia gas via a temperature programmed reaction. The oxide precursors are prepared by conventional solid state reaction between two appropriate monometallic oxides. The synthesis involves passing NH3gas over the oxide precursors at a flow rate of 6.80×102μmol s−1(1000 cm3/min) and raising the temperature at a heating rate of 8.3×10−2K s−1(5 K/min) to a final temperature (Tf) which is held constant for a short period of time (thold). The oxynitrides thus obtained are pyrophoric and need to be passivated before exposing them to air. All these new bimetallic oxynitrides have a face centered cubic crystal structure and high values of surface area. The surface reactivation and the thermal stability of the materials are studied by temperature programmed reduction and this indicates that the compounds can be divided into three groups of different reducibility (high, medium, and low). Their surface activity and surface area are evaluated based on CO chemisorption and N2physisorption measurements. It is found that the chemisorbed CO number density correlates with the reducibility of the compounds.

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1997

Y. Zhu, Desu, S. B., Tingkai Li, Dr. Sasangan Ramanathan, and Nagata, M., “SrBi2Ta2O9 Thin Films made by Liquid Source Metal-organic Chemical Vapor Deposition”, Journal of Materials Research, vol. 12, pp. 783–792, 1997.[Abstract]


A liquid source metal-organic chemical vapor deposition system was installed to deposit SrBi2Ta2O9 (SBT) thin films on sapphire and Pt/Ti/SiO2/Si substrates. The process parameters such as deposition temperature and pressure, and ratio of Sr: Bi: Ta in the precursor solutions were optimized to achieve stoichiometric films with good reproducible ferroelectric properties. It was found that the nucleation of SBT started at a deposition temperature close to 500 °C and grain growth dominated at 700 °C and higher temperatures. With increasing deposition temperatures, the grain size of SBT thin films increased from 0.01 μm to 0.2 μm; however, the surface roughness and porosity of the films also increased. To fabricate specular SBT films, the films had to be deposited at lower temperature and annealed at higher temperature for grain growth. A two-step deposition process was developed which resulted in high quality films in terms of uniformity, surface morphology, and ferroelectric properties. The key to the success of this process was the homogeneous nucleation sites at lower deposition temperature during the first step and subsequent dense film growth at higher temperature. The two-step deposition process resulted in dense, homogeneous films with less surface roughness and improved ferroelectric properties. SBT thin films with a grain size of about 0.1 μm exhibited the following properties: thickness: 0.16–0.19 μm; 2Pr: 7.8–11.4 μC/cm2 at 5 V; Ec: 50–65 kV/cm; Ileakage: 8.0–9.5 × 10−9 Acm−2 at 150 kV/cm; dielectric constant: 100–200; and fatigue rate: 0.94–0.98 after 1010 cycles at 5 V.

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1997

P. C. Joshi, Dr. Sasangan Ramanathan, Desu, S. B., and Stowell, S., “Microstructural and Electrical Characteristics of Rapid Thermally Processed (Ba1—xSrx)TiO3 Thin Films Prepared by Metalorganic Solution Deposition Technique”, physica status solidi (a), vol. 161, pp. 361-370, 1997.[Abstract]


Barium strontium titanate thin films including barium titanate BaTiO3 and strontium titanate SrTiO3 end members were fabricated on Pt-coated silicon and bare silicon substrates by metalorganic solution deposition (MOSD) technique using acetate precursors. Polycrystalline (Ba1—xSrx)TiO3 thin films were obtained by rapid thermal annealing at 700 °C for 60 s. The films were characterized for electrical properties in terms of dielectric permitivity, dissipation factor, and dc leakage current characteristics. A peak in dielectric constant was observed for (Ba0.6Sr0.4)TiO3 composition at room temperature. The typical measured small signal dielectric constant and dissipation factor for 0.5 μm-thick (Ba0.6Sr0.4)TiO3 films at 100 kHz were 450 and 0.012, respectively. (Ba0.6Sr0.4)TiO3 thin films exhibited a high voltage dependent tunability of 47% at an applied electric field of 0.5 MV/cm. The interfacial properties of Au/(Ba0.6Sr0.4)TiO3/Si structure were examined by high frequency C—V measurements. A charge storage density of 39.6 fC/μm2 and leakage current density of less than 10—8 A/cm2 were obtained for (Ba0.6Sr0.4)TiO3 thin films at an applied electric field of 100 kV/cm

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1997

C. C. Yu, Dr. Sasangan Ramanathan, Dhandapani, B., Chen, J. G., and S. Oyama, T., “Bimetallic Nb−Mo Carbide Hydroprocessing Catalysts:  Synthesis, Characterization, and Activity Studies”, The Journal of Physical Chemistry B, vol. 101, pp. 512-518, 1997.[Abstract]


A series of Nb1.0MoxOC (x = 0.67−2.0) catalysts were prepared by a temperature-programmed reaction technique. The catalysts were synthesized from oxide precursors in a flow of 20% CH4/H2 reactant gas mixture, while the temperature was increased linearly at 5 K/min (8.3 × 10-2 K s-1). The samples were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), near-edge X-ray absorption fine structure (NEXAFS), elemental analysis, CO chemisorption, surface area measurements, and temperature-programmed reduction. XRD patterns of the fresh catalysts indicated that Nb1.0Mo1.5OC and Nb1.0Mo1.75OC consisted of pure bimetallic carbide phases, while the other compositions showed impurity phases of NbO2 or Mo2C at high concentrations of Nb and Mo, respectively, in the starting oxide. The hydrodenitrogenation (HDN) and hydrodesulfurization (HDS) activity of these materials was studied in a high-pressure reactor system. The reactions were carried out at 3.1 MPa and 643 K using model liquid compounds containing moderate concentrations of sulfur, nitrogen, oxygen, and aromatics. All the catalysts were found to be active for quinoline HDN, and the activity did not show much variation with changes in the ratio of the two metals (Mo/Nb). However, the HDS activity was found to be more sensitive to the composition (Mo/Nb) and Nb1.0Mo1.75OC showed the highest HDS activity among the catalysts tested. The bimetallic compounds showed enhancement in the activity and stability compared to the corresponding monometallic carbides. X-ray diffraction patterns of the spent catalysts did not show any sulfide, oxide, or metal peaks, indicating that the catalysts were stable and tolerant of sulfur. More »»

1995

S. T. Oyama, Dr. Sasangan Ramanathan, and Yu, C. C., “Synthesis and Reactivity of New Bimetallic Oxynitrides”, Preprints of Papers – American Chemical Society, Division of Fuel Chemsirty, vol. 998, 1995.[Abstract]


A new series of bimetallic oxynitride catalysts, M{sub 1}M{sub 2}O{sub x}N{sub y} (M{sub 1} = V{sub 1}, Nb, Cr, Mn and Co, M{sub 2} = Mo or W), was prepared by nitriding the bimetallic oxide precursors in an ammonia gas stream at 1000 cm{sup 3}/min (6.8x10{sup 2} {mu}mol s{sup -1}) while the temperature was raised at 5 K/min (8.3x10{sup -2} K s{sup -1}). The catalysts were characterized by x-ray diffraction, x-ray photoelectron spectroscopy, CO chemisorption and surface area measurements. The catalytic activity of these catalysts for mixture containing 3000 ppm sulfur (dibenzothiophene), 2000 ppm nitrogen (quinoline), 500 ppm oxygen (benzofuran), 20 wt% aromatics (15 wt% tetralin and 5 wt% amylbenzene) and balance aliphatics (tetradecane). The activities of the bimetallic oxynitrides were compared to a commercial sulfided Ni-Mo/Al{sub 2}O{sub 3} catalyst tested at the same conditions. The bimetallic oxynitrides were active for quinoline HDN and V-Mo-O-N exhibiting higher HDN activity than the commercial Ni-Mo/Al{sub 2}O{sub 3} catalyst. The HDS activity of the bimetallic oxynitrides ranged from 9-37% with Co-Mo-O-N showing the highest HDS activity among the oxynitrides tested.

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1995

Dr. Sasangan Ramanathan and Oyama, S. T., “New Catalysts for Hydroprocessing: Transition Metal Carbides and Nitrides”, The Journal of Physical Chemistry, vol. 99, pp. 16365-16372, 1995.

1994

C. C. Yu, Dr. Sasangan Ramanathan, Sherif, F., and S. Oyama, T., “Structural, Surface, and Catalytic Properties of a New Bimetallic V-Mo Oxynitride Catalyst for Hydrodenitrogenation”, The Journal of Physical Chemistry, vol. 98, pp. 13038-13041, 1994.

Publication Type: Book Chapter

Year of Publication Title

1996

J. Wang, Dr. Sasangan Ramanathan, Castonguay, M., and McBreen, P. H., “Chemisorption of CO and NO on Molybdenum Carbide Foils”, in Book Chapter in The Chemistry of Transition Metal Carbides and Nitrides, Springer, Dordrecht, 1996, pp. 426-438.

1996

J. Wang, Dr. Sasangan Ramanathan, M. Castonguay, McBreen, P. H., and Oyama, S. T., “Monograph of the Chemistry of Transition Metal Nitrides and Carbides”, Chapman and Hall, London, 1996, p. 426.

Student Guidance

Doctoral Students

  1. “Development of Ulta High Temperature Resistance Polymeric Nanocomposites for Long Distance Space Applications”(Mr.P.Mohankumar)-Ongoing - Co-Supervisor
  2. “Development of Metal/Poly Ether Ether Ketone Hybrid Composite Laminates for Nuclear Waste Storage Containers” (Mr. Manu Remanan)-Ongoing-- Co-Supervisor