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Biography

Prof. Venkatesan has been a Physicist and manager for 17 years with Bell Labs and Bellcore and in the last 17 years has been with the Center for Superconductivity Research at University of Maryland, College Park. He founded the Surface Center at Rutgers University where he was a Professor for about five years (85-90). Most recently he was leading an effort in Oxide Electronics at UMD. Since 2008 he is directing the NanoCore Research Center at the National University of Singapore. He pioneered the Pulsed Laser deposition process and was the first to elucidate the intricacies of the process to make this a reproducible laboratory technique for the growth of high quality multi-component oxide thin films. He is an ISI highly cited Physicist (>20,000 citations ranked 66) has over 450 papers and 27 patents in the area of oxides involving superconductors, magnetic and optical materials. He is a Fellow of the American Physical society, World Innovation Forum, winner of the Bellcore award of excellence and the UMD graduate Board award. He was a member of the Physics Policy Committee and is the founding member of the International Oxide Electronics Workshop. In 1989 he founded Neocera, a company specializing in pulsed laser and electron deposition equipments and also commercialized the HTS SQUID based magnetic microscope MAGMA for semiconductor failure analysis used by virtually all leading semiconductor manufacturers in the world today. A technology based on the scanning microwave near field microscope for silicon low K metrology was commercialized and sold to Solid State Measurements (SSM). He has helped many of his students and post docs in starting companies and 8 of them have started small companies or are holding executive positions in entrepreneurial ventures. He has raised venture capital money over several rounds and has been on the advisory board of the New Market Venture fund of UMD Dingman Center, the UMD incubator and has been involved in promoting entrepreneurship among young researchers. He holds a PhD from the University of New York and Bell Laboratories, USA and an MSc and a BSc (Honors) from the Indian Institute of Technology in Kanpur, India.

Contact

Faculty of Engineering, Department of Electrical and Computer Engineering, 4 Engineering Drive 3, National University of Singapore, 117576 Singapore. Email.

Currently Available PhD Projects

Novel Magnetic Phenomena in Oxides (Diluted magnetic oxides and multiferroics) 

Doping wide bandgap oxides can lead to high temperature ferromagnetism. Our group has been a pioneer in the area and we have extensively studied a number of host materials such as TiO2, HfO2, Cu2O, SnO2, ZnO. While the field is some what clouded by controversy arising from sample related artifacts, a successful process for the development of Oxide based ferro-magnets would have a significant impact on the field of Spintronics, where spin based electronic devices would be used for computation, optical communication and memory. We will end up with transparent ferromagnets with a variety of applications. 

The researchers involved in this program will learn to make ceramic target materials for the Pulsed laser deposition (PLD) process and learn to make atomically controlled films on a variety of substrates. They will learn a number of characterization tools (XRD, RBS/ Channeling, electron microscopy, STM/ AFM, UV-Vis Spectrometry, Photo- luminescense for studying the chemical, physical, electronic and magnetic property of the films at a variety of temperatures. These skills would be of great value for industrial research and would prepare the students for a future career in the industry, academia or as entrepreneurs. 

(1) S.X. Zhang, W. Yu, S.B. Ogale, S.R. Shinde, D.C. Kundaliya, W.K. Tse, S.Y. Young, J.S. Higgins, L.G. Salamanca-Riba, M. Herrera, L.F. Fu, N.D. Browning, R.L. Greene, T.  Venkatesan, ‘Magnetism and anomalous hall effect in Co-(La,Sr)TiO3â€? Phys. Rev. B 76, 085323 (2007).

 (2) T. Venkatesan, D.C. Kundaliya, T. Wu, S.B. Ogale, ‘Novel approaches to field modulation of electronic and magnetic properties of oxidesâ€? Phil. Mag. Lett. 87, 279-292 (2007).

 (3) L.F. Fu, N.D. Browning, S.X Zhang, S.B Ogale Ogale, D.C Kundaliya, T. Venkatesan, ‘Defects in Co-doped and (Co, Nb)-doped TiO2 ferromagnetic thin filmsâ€?

J. Appl. Phys. 100,123910 (2006).

 (4) S.X. Zhang, S.B. Ogale, D.C Kundaliya, L.F. Fu, N.D. Browning, S. Dhar, W. Ramadan, J.S Higgins, R.L Greene, T. Venkatesan, ‘Search for ferromagnetism in conductive Nb : SrTiO3 with magnetic transition element (Cr, Co, Fe, Mn) dopantsâ€?/p>

Appl. Phys. Lett. 89, 012501 (2006).

 (5) M.S.R Rao, D.C. Kundaliya, S.B. Ogale, L.F. Fu, S.J. Welz, N.D. Browning, V. Zaitsev, B. Varughese, C.A. Cardoso, A. Curtin, S. Dhar, S.R. Shinde, T. Venkatesan, S.E. Lofland, S.A. Schwarz, ‘Search for ferromagnetism in undoped and cobalt-doped HfO2-deltaâ€?Appl Phys. Lett. 88, 142505 (2006).

(6) D.C. Kundaliya, S.B. Ogale, S. Dhar, K.F. McDonald, E. Knoesel, T. Osedach, S.E  Lofland, S.R. Shinde, T. Venkatesan, ‘Large second-harmonic kerr rotation in GaFeO3 thin films on YSZ buffered siliconâ€?J. Magn. Magn. Mater. 299, 307-311 (2006).

 (7) S.X. Zhang, S.B. Ogale, L.F. Fu, S. Dhar, D.C. Kundaliya, W. Ramadan, N.D  Browning, T. Venkatesan, ‘Consequences of niobium doping for the ferromagnetism and microstructure of anatase Co : TiO2 filmsâ€?Appl. Phys. Lett. 88, 012513 (2006).

 (8) T. Zhao, S.R. Shinde, S.B. Ogale, H. Zheng, T. Venkatesan, R. Ramesh, S. Das Sarma, ‘Electric field effect in diluted magnetic insulator anatase Co : TiO2â€? Phys. Rev. Lett. 94, 126601 (2005).

 (9) S.R. Shinde, S.B. Ogale, J.S. Higgins, H. Zheng, A.J. Millis, V.N. Kulkarni, R. Ramesh, R.L. Greene, T. Venkatesan, ‘Co-occurrence of superparamagnetism and anomalous Hall effect in highly reduced cobalt-doped rutile TiO2-delta filmsâ€? Phys. Rev. Lett. 92, 166601 (2004).

(10) D.C. Kundaliya, S.B. Ogale, S.E. Lofland, S. Dhar, C.J. Metting, S.R. Shinde,  Z. Ma, B. Varughese, K.V. Ramanujachary, L. Salamanca-Riba, T. Venkatesan, ‘On the origin of high-temperature ferromagnetism in the low-temperature-processed Mn-Zn-O systemâ€?, Nat. Mater. 3, 709-714 (2004).

(11) S.B. Ogale, R.J. Choudhary, J.P. Buban, S.E. Lofland, S.R. Shinde, S.N. Kale, V.N.  Kulkarni, J. Higgins, C. Lanci, J.R. Simpson, N.D. Browning, S. Das Sarma, H.D. Drew, R.L. Greene, T. Venkatesan, ‘High temperature ferromagnetism with a giant magnetic moment in transparent Co-doped SnO2-deltaâ€? Phys Rev. Lett. 91, 077205 (2003).

 

Wide bandgap Oxides and nitrides (ZnMgO, TiO2 and AlN) 

GaN has become the material of choice for wide bandgap optical devices, LEDs and lasers. While GaN is truly a wonder material an alternate material would have a significant impact on the filed of home lighting and high power electronics by spurring competition and innovation. ZnO has been the canonical material to champion this role for the following reasons:   

·        ZnO has a large exciton binding energy making this a super luminescent material and attractive for optical applications

·        ZnMgO alloys can take the bandgap to 7.8 eV the largest bandgap spread possible. For example, GaAlN system saturates at 6 eV

·        The terrestrial abundance of ZnO and the availability of large ZnO crystals as substrates for homo epitaxy gives a compelling reason to develop such a technology in the ZnO system for scalability and cost reduction.

 However, ZnO has not lived up to the expectation simply because p-ZnO is highly unstable and difficult to make. We are focusing on an alternate system which is TiO2 and we believe that PN junctions may be possible in this system. We have made two different n-type transparent conductors in TiO2 based on Nb and Ta doping but work is on to produce a p-Type dopant in this system. 

The researchers involved in this program will learn to make ceramic target materials for the Pulsed laser deposition (PLD) process and learn to make atomically controlled films on a variety of substrates. They will learn a number of characterization tools (XRD, RBS/ Channeling, electron microscopy, STM/ AFM, UV-Vis Spectrometry, Photo-luminescense for studying the chemical, physical, electronic and magnetic property of the films at a variety of temperatures. These skills would be of great value for industrial research and would prepare the students for a future career in the industry, academia or as entrepreneurs. 

References

(1) A. Lussier, J. Dvorak, S. Stadler, J. Holroyd, M. Liberati, E. Arenholz, S.B. Ogale, T. Wu, T. Venkatesan, Y. U. Idzerda, ‘Stress relaxation of La1/2Sr1/2MnO3 and La2/3Ca1/3MnO3 at solid oxide fuel cell interfaces� Thin Solid Films 516, 880-884 (2008).

 (2) S.X. Zhang, S. Dhar, W. Yu, H. Xu, S.B. Ogale, T. Venkatesan,‘Growth parameter-property phase diagram for pulsed laser deposited transparent oxide conductor anatase Nb : TiO2â€? Appl. Phys. Lett. 91, 112113 (2007).

 (3) S.X. Zhang, D.C.  Kundaliya, W. Yu, S. Dhar, S.Y. Young, L.G. Salamanca-Riba, S.B Ogale, R.D. Vispute, T. Venkatesan, ‘Niobium doped TiO2: Intrinsic transparent metallic anatase versus highly resistive rutile phaseâ€? J. Appl. Phys. 102, 013701 (2007).

 (4) L.F. Fu, N.D. Browning, W. Ramadan, S.B. Ogale, D.C  Kundaliya, T. Venkatesan, â€?Interface and defect structures in YBa2Cu3O7-delta and Nb : SrTiO3 heterojunctionâ€? J. Phys. D-Appl. Phys, 40, 187-191 (2007).

 (5) S. Kharrazi, D.C. Kundaliya, S.W. Gosavi, S.K. Kulkarni, T. Venkatesan, S.B. Ogale, J. Urban, S. Park, S.W. Cheong,â€? Multiferroic TbMnO3 nanoparticlesâ€? Solid State Comm. 138, 395-398 (2006).

 (6) W. Ramadan, S.B. Ogale, S. Dhar, S.X. Zhang, D.C.  Kundaliya, I. Satoh, T. Venkatesan, â€?Substrate-induced strain effects on the transport properties of pulsed laser-deposited Nb-doped SrTiO3 filmsâ€? Appl. Phys. Lett. 88, 142903 (2006).

 (7) W. Ramadan, S.B. Ogale, S. Dhar, L.F. Fu, N.D. Browning, T. Venkatesan,â€?Room temperature rectifying characteristics of epitaxial Y1Ba2Cu3-xZnxO7-delta (x=0.0,0.2) and Nb : SrTiO3 (Nb : 0.05%, 0.1%, 0.5%) heterojunctionsâ€? J. Appl. Phys. 99, 043906 (2006).

 (8) S. Dhar, M.S.R Rao, S.B. Ogale, D.C. Kundaliya, S.R. Shinde, T. Venkatesan, S.J.  Welz, R. Erni, N.D. Browning, â€?Growth of highly oriented HfO2 thin films of monoclinic phase on yttrium-stabilized ZrO2 and Si substrates by pulsed-laser depositionâ€? Appl. Phys. Lett. 87, 241504 (2005).

 (9) W. Ramadan, S.B. Ogale, S. Dhar, L.F. Fu, S.R. Shinde, D.C. Kundaliya, M.S.R Rao, N.D. Browning, T. Venkatesan, ‘Electrical properties of epitaxial junctions between Nb : SrTiO3 and optimally doped, underdoped, and Zn-doped YBa2Cu3O7-deltaâ€? Phys. Rev. B 72, 205333 (2005).  

 

Atomically layered Oxides for Novel Functionality 

Using pulsed laser deposition process and reflection high energy electron diffraction, atomic layer-by-layer growth of oxides is possible today. When insulators such as LaAlO3 and SrTiO3 are grown in such alternating layer structures, an interface electron cloud is formed with extremely high mobilities and unusual magnetic properties. This architecture may be the route to novel material functionalities. By varying the oxides we may be able to produce novel superconductors, thermoelectric materials and so on. This is one of the hottest research areas in condensed matter today. 

The researchers involved in this program will learn to make ceramic target materials for the Pulsed laser deposition (PLD) process and learn to make atomically controlled films on a variety of substrates. They will learn a number of characterization tools (XRD, RBS/ Channeling, electron microscopy, STM/ AFM, UV-Vis Spectrometry, Photo-luminescense for studying the chemical, physical, electronic and magnetic property of the films at a variety of temperatures. These skills would be of great value for industrial research and would prepare the students for a future career in the industry, academia or as entrepreneurs. 

References:

(1) A. Brinkman, M. Huijben, M. Van Zalk, J. Huijben, U. Zeitler, J.C. Maan, W.G. van der Wiel, G. Rijnders, D.H.A. Blank, and H. Hilgenkamp, ‘Magnetic effects at the interface between non-magnetic oxides� Nature Materials 6, 493-496 (2007).

(2) I.S. Elfimov, A. Rusydi, S.I. Csiszar, Z. Hu, H.H. Hsieh, H.-J. Lin, C.T. Chen, R. Liang and G.A. Sawatsky, ‘Magnetizing oxides by substituting nitrogen for oxygen� Phys. Rev. Lett. 137202 (2007).

(3) Y. Hotta, T. Susaki and H.Y. Hwang, ‘Polar discontinuity doping of the LaVO3/SrTiO3 interface� Phys. Rev. Lett. 99, 236805 (2007).

(4) A. Ohtomo and H.Y. Hwang, ‘A high-mobility electron gas at the LaAlO3/SrTiO3 heterointerface� Nature 427, 423-426 (2004).

(5) J. Osorio-Guillén, S. Lany, S.V. Barabash and A. Zunger, ‘Magnetism without magnetic ions: percolation, exchange and formation energies of magnetism-promoting intrinsic defects in CaO� Phys. Rev. Lett. 96, 107203 (2006).

(6) N. Reyren, S. Thiel, A.D. Caviglia, L.F. Kourkoutis,G. Hammerl, C. Richter, C.W. Schneider, T. Kopp, A.S. Ruetschi, D. Jaccard, M. Gabay, D.A. Muller, J.M. Triscone, and J. Mannhart, ‘Superconducting interfaces between insulating oxides� Science 317, 1196-1199 (2007).

(7) Science Magazine, �span lang="EN-GB">Breakthroughs of the year: The Runners-Up� Science 318, 1844-1849 (2007).

  

Superhydrogenic Dopants in Oxides 

A hydrogen atom in free space has a radius of 0.5A. What happens if we put this hydrogen atom in a medium with a large dielectric constant? E.g., in medium with a dielectric constant of 20, the Rhydberg radius will be 10A. Such super hydrogens can be created in wide band gap oxides, with large dielectric constant by doping them with n or p type dopants. At concentrations of about 1% these super hydrogenic orbitals will overlap to give a band and the predictions are that these bands will either be antiferro magnetic or ferromagnetic both of which are interesting materials. In addition, one may be able to make unusual optical materials as well. We are working with a dozed binary oxides chosen for their simplicity, band gap and dielectric constants and have started to dope them and study them. The research here is truly exploratory and the outcome is unpredictable but the potential for impact making research is very high. 

The researchers involved in this program will learn to make ceramic target materials for the Pulsed laser deposition (PLD) process and learn to make atomically controlled films on a variety of substrates. They will learn a number of characterization tools (XRD, RBS/ Channeling, electron microscopy, STM/ AFM, UV-Vis Spectrometry, Photo-luminescense for studying the chemical, physical, electronic and magnetic property of the films at a variety of temperatures. These skills would be of great value for industrial research and would prepare the students for a future career in the industry, academia or as entrepreneurs. 

References: 

S.X. Zhang, S.B. Ogale, W. Yu, X. Gao, T. Lin, A.T.S. Wee, R.L. Greene, T. Venkatesan, ‘Magnetic effect in a non-magnetic transparent oxide semiconductor with non-magnetic ion doping: anatase Nb:TiO2â€? subm. to Phys. Rev. Lett. 

  

Approach to sub-nm ion beam imaging and nanostructuring 

Ion beams can be focused just like electron beams and photons. As of today the most popular ion beam systems have been based on liquid metal ion sources (predominantly Gallium) and the state of the art machine can produce a focused spot of Ga to a size of about 4-5nm. A revolutionary technology based on field emission source has enabled the helium ion microscope where the ion beam has a focus spot of 0.5 nm with a theoretical limit of 0.25nm. A helium ion microscope will be delivered and installed in Nanocore by the end of September. These are the following research goals:

  1. Develop Rutherford backscattering images with the highest spatial resolution possible
  2. Develop techniques to image biological systems in the secondary electron mode with resolutions approaching sub-10nm
  3. Develop techniques to use the ion beam to pattern a variety of organic and inorganic materials to get to feature sizes approaching a nm
  4. Deposit metals and insulators from the gas phase by ion induced chemistry and explore the limits to the pattern resolution

 The researchers will primarily develop expertise in the use of a beam microscope, beam optics, ion-solid interaction and lithography. In addition they will learn a number of characterization tools (XRD, RBS/ Channeling, electron microscopy, STM/ AFM, UV-Vis Spectrometry, Photo-luminescense for studying the chemical, physical, electronic and magnetic property of the nano- and quantum structures created at a variety of temperatures. These skills would be of great value for industrial research and would prepare the students for a future career in the industry, academia or as entrepreneurs.

References:

1.            High-energy ion-beam modification of polymer-films. Venkatesan T Nuclear Instruments & Methods in Physics research section b-beam interactions with Materials and Atoms   Volume: 7-8   Issue: Mar   Pages: 461-467   Published: 1985

2.         Structural and chemical-analysis of ion-beam produced conductive regions on highly resistive organic films. Venkatesan T, Forrest SR, Kaplan ml, et al. Journal of Applied Physics   Volume: 56   Issue: 10   Pages: 2778-2787   Published: 1984

3.         Gas-phase-functionalized plasma-developed resists - initial concepts and results for electron-beam exposure. Taylor GN, Stillwagon LE, Venkatesan T. Journal of the Electrochemical Society   Volume: 131   Issue: 7   Pages: 1658-1664   Published: 1984

4.         The scope and mechanism of new positive tone gas-phase-functionalized plasma-developed resists. wolf tm, Taylor GN, Venkatesan T, et al.  Journal of the Electrochemical Society   Volume: 131   Issue: 7   Pages: 1664-1670   Published: 1984

5.                  Ionization induced decomposition and diffusion in thin polymer-films Venkatesan T, Edelson D, Brown WL. Nuclear instruments & methods in physics research section b-beam interactions with materials and atoms   Volume: 229   Issue: 2-3   Pages: 286-290   Published: 1984

6.                  Comparison of conductivity produced in polymers and carbon-films by pyrolysis and high-energy ion irradiation. Venkatesan T, Dynes RC, Wilkens B, et al. Nuclear instruments & methods in physics research section b-beam interactions with materials and atoms   Volume: 229   Issue: 2-3   Pages: 599-604   Published: 1984

7.                  Secondary-electron, ion and photon-emission during ion-beam irradiation of polymer and condensed gas films. Venkatesan T, Brown WL, Wilkens BJ, et al. Nuclear instruments & methods in physics research section b-beam interactions with materials and atoms   Volume: 229   Issue: 2-3   Pages: 605-609   Published: 1984

8.                  Ion-beam irradiated via-connect through an insulating polymer layer Venkatesan T, Feldman M, Wilkens BJ, et al. journal of applied physics   Volume: 55   Issue: 4   Pages: 1212-1214   Published: 1984

9.                  Optical and electrical-properties of ion-beam-irradiated films of organic molecular-solids and polymers. Kaplan ML, Forrest SR, Schmidt PH, et al. Journal of Applied Physics   Volume: 55   Issue: 3   Pages: 732-742   Published: 1984

10.              Structural and morphological investigation of the development of electrical-conductivity in ion-irradiated thin-films of an organic material Lovinger AJ, Forrest SR, Kaplan ML, et al. Journal of Applied Physics   Volume: 55   Issue: 2   Pages: 476-482   Published: 1984

11.              Dynamics of ion-beam modification of polymer-films. Venkatesan T, Brown WL, Murray CA, et al. Polymer engineering and science   Volume: 23   Issue: 17   Pages: 931-934   Published: 1983

12.              Synthesis of novel inorganic films by ion-beam irradiation of polymer-films. Venkatesan T, Wolf T, Allara D, et al. Applied physics letters   Volume: 43   Issue: 10   Pages: 934-936   Published: 1983

13.              Ion-beam-induced conductivity in polymer-films. Venkatesan T, Forrest SR, Kaplan ML, et al. Journal of Applied Physics   Volume: 54   Issue: 6   Pages: 3150-3153   Published: 1983

14.              Species and deposition angle dependence of ion-beam induced densification of germanium selenide films. Venkatesan T, Wilkens BJ.  Applied physics letters   Volume: 41   Issue: 9   Pages: 839-841   Published: 1982

15.              Large conductivity changes in ion-beam irradiated organic thin-films Forrest SR, Kaplan ML, Schmidt PH, et al. Applied physics letters   Volume: 41   Issue: 8   Pages: 708-710   Published: 1982

16.              Obliquely deposited germanium selenide films photo and ion-beam induced contraction. Venkatesan T, Wilkens B, Fisher K. Journal of the Electrochemical Society   Volume: 129   Issue: 3   Pages: C97-C97   Published: 1982

17.              Ion-beam lithography. Brown WL, Venkatesan T, Wagner A. Nuclear instruments & methods in physics research   Volume: 191   Issue: 1-3   Pages: 157-168   Published: 1981

18.              Germanium selenide - a resist for low-energy ion-beam lithography Wagner A, Barr D, Venkatesan T, et al. Journal of vacuum science & technology   Volume: 19   Issue: 4   Pages: 1363-1367   Published: 1981

19.              The chemical-reactivity and lithographic sensitivity of obliquely deposited germanium selenide films used as low-energy ion-beam resists Venkatesan T. Journal of vacuum science & technology   Volume: 19   Issue: 4   Pages: 1368-1373   Published: 1981

20.              Plasma-developed ion-implanted resists with sub-micron resolution Venkatesan T, Taylor GN, Wagner A, et al. Journal of vacuum science & technology   Volume: 19   Issue: 4   Pages: 1379-1384   Published: 1981

Venky Venkatesan - NanoCore Director