Leslie H Allen

Associate Professor Emeritus, Materials Science and Eng.

(217) 333-7918

l-allen9@illinois.edu

182 Engineering Sciences Building

For More Information

Professional Highlights

Professor Allen received his BS degree in mathematics (University of North Dakota, 1975), MS degree in physics (Clarkson University, New York, 1979), and PhD degree in materials science and engineering (Cornell University, 1990, under the guidance of Jim Mayer). In the six years before beginning his PhD program, he was engaged in research and development within the electronics industry. At Shell Oil Company, he helped develop CuS/CdS large-scale photovoltaic devices, concentrating on device modeling and processing to increase efficiency and reliability. He developed analytical models describing the material and device characteristics during Cu electromigration. This work led to a general theory of the phenomena and to processing solutions to the problem. At McDonnell Douglas (St. Louis, Mo.), he continued his work in photovoltaics in the development of HgCdTe IR detectors. These optoelectronic detectors were designed into focal plane arrays, thus creating a microelectronic imaging device. He holds a zero-time appointment as a Research Associate Professor in the Microelectronics Lab.

Research Statement

I have several areas of research which focus mainly on the basic materials processes such as nucleation and growth processes in metal/semiconductor systems. We work on problems which have a direct connection to microelectronics applications. Some examples include the following:

Silicides for Silicon Source/Drain contacts

Phys. Rev. B 49,13501-13511 (1994), Appl. Phys. Lett. 65, 561-563 (1994), J. Appl. Phys. 77, 4384-4388(1995), "Symposium for Microelectronic Silicides," MRS (1996).

Ohmic contacts

GaN [APL 64, pg.1003, 1994]; GaAs [APL. 51, pg. 326, 1987]

Diffusion Barriers

US Patent #5,023,201 (1991), US Patent #5,138,432 (1992), JAP, 79, 2446-2457 (1996), APL, 60 3179 (1996), Patent Filed #96-096, (1996).The second area of research involves the development of a new tool for materials studies:

Nanocalorimetry

Our group has invented a new Thin Film Scanning Calorimetry TDSC device. TDSC is the most sensitive scanning calorimetry device yet reported being 100-1000 times more sensitive than conventional systems. Our objective is to use the technique in two new areas: dynamic energy measurements at surfaces and sensor technology. The first steps toward these objectives have been extremely successful.

Scanning Nano-Calorimetry

Differential Scanning Calorimetry (DSC) is a technique to measure heat exchange during chemical reactions or phase transformations. We have taken the old concept of scanning calorimetry and transformed it into a new powerful characterization/sensor device using micro-machining techniques. This has expanded DSC from traditional 3-D bulk systems to 2-D surface systems. Our TDSC is built upon the idea of the micro-heater, a thin strip of metal which we heat at extremely fast rates ~ 1,000,000 C/s by pulsing large currents through it. The TDSC is the most sensitive calorimetry system yet reported (0.2 nJ), capable of measuring the energy equivalent to melting 0.1 monolayer of atoms.

Size-Dependent Melting Point

We demonstrated the power of TDSC in our melting point study of Sn nanostructures. We are the first to show that both the melting point Tm and the heat of fusion Hm decrease when the physical size of the Sn structures decreases (<20nm). When 1è of Sn is deposited onto an inert substrate, the Sn atoms self-assemble into small islands (nanostructures) consisting of ª 1000 atoms. We found that these islands melt at Tm = 110C, far below the bulk value of 232C. At this stage, our TDSC technique is posed to answer key questions about the basic nature of the melting process, especially regarding surface pre-melting. Melting point depression of small particles has two strong implications for microelectronics technology: (i) control of crystallographic texture for metals during the early stages of film growth during island formation, and (ii) the stability/reliability of aluminum interconnect lines which will have dimensions of only 70 nm by the year 2002. Will these lines be solid or liquid at these dimensions?

Undergraduate Research Opportunities

Scott Andrews (1997) Calorimetry Noise

Desmond Low (1998) Calorimetry Electronics (Amplifier)

Tim Wisleder (1998-2000) Calorimetry Fabrication/Electronics

Paige Reardon (1999-2000) Fabrication Stress Measurement System

Carl Dohrman (2000 – present) Photonics Filters (Paul Braun’s student - EOH)

Chris Ariagno (2000-present) Nanocalorimetry Studies

Wojciech Wolski (2001-2002) Thermal Stability of Polystyrene on Nanocalorimeter

Amanda Habas (2002) Nanocalorimetry

Jonathan Hollander (2002-2003) Nanocalorimeter Thermal Modeling

Lynsa Nguyen (2003) Nanocalorimetry

Brian Bertram (2005) In-situ Resistance during Evaporation (2005)

Darcy Barron (2004-2006) Heat Transfer Modeling Nanocalorimetry

John Naber (2009-2010)

Abigail Chanda (2011)

Yiran Yan (2011-2013)

Rui Ning (2014)

Anisa Nuanes (2014)

Selected Articles in Journals

Z. Ye, L. de la Rama, M. Efremov, A. Sutrisno, L. Allen “Critical Size for Bulk-to-discrete Transition in 2D Aliphatic Layers: Abrupt Size Effect Observed via Calorimetry and Solid-state 13C NMR”, J. Phys. Chem C, 2017, 121 (25), 13916-13929. (2017)
Z. Ye, L. de la Rama, M. Efremov, J-M. Zuo, L. Allen, “Approaching the Size Limit of Organometallic Layers: Synthesis and Characterization of Highly Ordered Silver-Thiolate Lamellae with Ultra-short Chain Lengths”, Dalton Transactions, 2016, 45, 18954-18966.
Z. Ye, Z. Ma, L. Allen, Book Chapter: “Application of In Situ Resistance and Nanocalorimetry Measurements for Nanoelectronic Thin Film Materials”, Book Title: “Metrology and Diagnostic Techniques for Nanoelectronics”, edited by Z. Ma, D. Seiler, CRC Press, 2016, ISBN 978-981-4745-08-6
Z. Ye, L. de la Rama, L. Hu, M. Efremov, L. Allen, “Nanocalorimetry Study of the Evolution of Melting Characteristics of Single Layer Silver Alkanethiolate Lamella: Fast Heating/Cooling and Electrical Annealing”, Thermochimica Acta, Chip Calorimetry Special Issue, 2015, 603, 69-78
L. P. de la Rama, L. Hu, Z. Ye, M. Efremov, L. H. Allen, "Size Effect and Odd–Even Alternation in the Melting of Single and Stacked AgSCn Layers: Synthesis and Nanocalorimetry Measurements", Journal of the American Chemical Society, Vol. 135 (38), 14286-14298 (2013).
M. Zhang, Jianguo Wen, M. Yu. Efremov, E. A. Olson, L. Hu, K. L. Kavanagh, Z. Ma, B. Blanpain, and L. H. Allen, “Metastable Phase Formation in the Au-Si System”, Journal of Applied Physics, Vol. 111, 093516 (2012).
L. P. de la Rama, L. Hu, M. Efremov, E. Olson, P. Nealey, M. McLean, S. Sligar and L. H. Allen, "Anomalous transitions of DODAB using fast scanning liquid calorimetry, Thermochimica Acta, Vol. 522(1-2) 72-76 (2011).
L. Hu, L. P. de la Rama, M. Y. Efremov,Y. Anahory, F. Schiettekatte, and L. H. Allen, "Synthesis and Characterization of Single-Layer Silver-Decanethiolate Lamellar Crystals," Journal of the American Chemical Society, Vol 133, p4367 (2011).
Y. Anahory, M. Guihard, D. Smeets, R. Karmouch, F. Schiettekatte, P. Vasseur, P. Desjardins, L.A. Hu, L.H. Allen, E. Leon-Gutierrez and J. Rodriguez-Viejo, "Fabrication, characterization and modeling of single-crystal thin film calorimeter sensors," Thermochimica Acta, 510(1-2), 126-136 (2010).
R. K. Kummamuru, L. P. de la Rama, L. Hu, M. D. Vaudin, M. Y. Efremov, M. L. Green, D. A. LaVan and L. H. Allen, "Measurement of heat capacity and enthalpy of formation of nickel silicide using nanocalorimetry," Appl. Phys. Lett., Vol. 95, n18, (2009).
L. Hu, Z. Zhang, M. Zhang, M. Y. Efremov, E. A. Olson, L. P. de la Rama, R. K. Kummamuru and L. H. Allen, "Self-assembly and ripening of polymeric silver-alkanethiolate crystals on inert surfaces," Langmuir, Vol. 25, 9585-9595 (2009).
R.K. Kummamuru, L. Hu, L. Cook, M.Y. Efremov, E.A. Olson and L.H. Allen, "A close proximity self-aligned shadow mask for sputter deposition onto a membrane or cavity," Journal of Micromechanics and Microengineering, Vol 18 (9) 095027 (2008).
M. Zhang, E. A. Olson, R. D. Twesten, J. G. Wen, M. Marshall, L. H. Allen, I.M. Robertson and I. Petrov, "In situ transmission electron microscopy studies enabled by microelectromechanical system technology," J. Mat. Res., Vol 20, 802 (2005).
E. A. Olson, M. Yu. Efremov, M. Zhang, Z. Zhang and L. H. Allen, "Size-dependent melting of Bi nanoparticles," J. Appl. Phys., Vol 97 034304 (2005).
Z. S. Zhang, O.M. Wilson, M. Y. Efremov, E. A. Olson, M. Zhang, P. V. Braun, C. Ober, W. Senaratne and L. H. Allen, "Heat capacity measurements of two-dimensional self-assembled monolayers on polycrystalline gold," Appl. Phys. Lett., Vol 84 , 5198 (2004).
M. Y. Efremov, E. A. Olson, M. Zhang, Z. Zhang and L. H. Allen, "Glass transition in ultra-thin polymer films: calorimetric study: annealing study," Macromolecule, Vol 37, 4607 (2004).
M. Yu. Efremov, E. A. Olso n, M. Zhang, S. L. Lai, F. Schiettekatte, Z. S. Zhang and L. H. Allen, "Thin-Film Differential Scanning Nanocalorimetry: Heat Capacity Analysis," Thermochimica Acta., Vol 412, p13 (2004).
M. Y. Efremov, Eric A. Olson, Ming Zhang, Zishu Zhang, F. Schiettekatte and Leslie H. Allen, RSI "Ultra-sensitive thin-film differential scanning calorimeter," Rev. of Sci. Inst., Vol 75,179 (2004).
M. Y. Efremov, E. A. Olson, M. Zhang, Z. Zhang and L. H. Allen. "Glass transition in ultra-thin polymer films: calorimetric study," Phys. Rev. Lett., Vol 91, p85703 (2003).
M. Yu. Efremov, E. A. Olson, M. Zhang and L. H. Allen, "Glass transition of thin films of Poly (2-vinyl pyridine) and Poly(methyl methacrylate): nanocalorimetry measurements," Thermochimica Acta., Vol 403, 37 (2003).
E. A. Olson, M. Yu. Efremov, M. Zhang, Z. S. Zhang and L. H. Allen, "The Design and operation of a MEMS differential scanning nanocalorimeter for high-speed heat capacity measurements of ultrathin films," IEEE J. Microelectromech. Sys., Vol 13, 355 (2003).
M. Zhang, M. Yu. Efremov, E. A. Olson, Z. S. Zhang and L. H. Allen, "Real-time heat capacity measurement during thin-film deposition by scanning nanocalorimetry," Appl. Phys. Lett., Vol 81, p3801 (2002).
M. Yu. Efremov, J. T. Warren, E. A. Olson, M. Zhang, A. T. Kwan and L. H. Allen, "Thin-film differential scanning calorimetry: a new probe for assignment of the glass transition of ultra thin polymer films," Macromolecules, Vol 35, p1481, 26 (2002).
A. T. Kwan, M. Yu. Efremov, E. A. Olson, F. Schiettekatte, M. Zhang, P. H. Geil and L. H. Allen, "Nanoscale calorimetry of isolated polyethylene single crystals," Journal of Polymer Science Part B: Polymer Physics, Vol 39, no. 11, pp. 1237-1245 (2001).
E. A. Olson, M. Yu. Efremov, A. T. Kwan, S. Lai, F. Schiettekatte, J. T. Warren, T. Wisleder, M. Zhang, V. Petrova, and L. H. Allen, “Scanning Nanocalorimeter for Nanoliter Scale Liquid Samples”, Appl. Phys. Lett., Vol 77, 2671 (2000).
M. Zhang, M. Y. Efremov, F. Schiettekatte, E. A. Olson, A. T. Kwan, L. S. Lai, J. E. Greene and L. H. Allen, “Melting Point Depression of Nanostructures using Heat Capacity Measurements: Nanocalorimetry Technique,” Phys. Rev. B., Vol 62, 10548 (2000).
M. Y. Efremov, F. Schiettekatte, M. Zhang, E. A. Olson, A. T. Kwan, R. S. Berry and L. H. Allen, “Discrete Periodic Melting Points in Nanostructure,” Phys. Rev. Lett., Vol 85, 3560 (2000).
G. Ramanath, J. E. Greene, I. Petrov, J. E. Baker, G. Gillen and L. H. Allen, "Channeling-induced asymmetric distortion of depth profiles from polycrystalline-TiN /Ti /TiN(001) trilayers during secondary ion mass spectrometry," Journal Vacuum Science and Technology B, JVST B, Vol 18, 1369 (2000).
G. Ramanath, J. E. Greene, J. R. A. Carlsson, V. C. Hornback, D. J. Allman and L. H. Allen, “W deposition and titanium fluoride formation during WF/sub 6/ reduction by Ti: Reaction path and mechanisms," J. Appl. Phys., Vol 85, 1961 (1999).
L. H. Allen and S. L. Lai, “MEMS-based scanning calorimeter for thermodynamic properties of nanostructures," Microscale Thermophysical Engineering, Vol 2, 11 (1998).
S. L. Lai, J. Carlsson and L. H. Allen, "Melting point depression of Al clusters generated during the early stages of film growth: nanocalorimetry measurements," Appl. Phys. Lett., Vol 72, 1098 (1998).
S. L. Lai, J. Y. Guo, V. Petrova, G. Ramanath and L. H. Allen, "Size-dependent melting properties of small tin particles: nanocalorimetric measurements," Phys. Rev. Lett., Vol 77, 99-103 (1996).

Teaching Honors

UIUC College of Engineering, Advisor's List for Advising Excellence (1999, 2002)

Research Honors

NSF Sponsored “Cornell Nanofabrication Facility (CNF)” Review Board. (2000-2003)
Program committee, Annual AVS Microelectronics and Interfaces, Santa Clara, CA. (2000-2003)
NSF Sponsored “Cornell Nanofabrication Facility (CNF)” Review Board. (1999)
Alpha Delta Pi "Outstanding Scholar Faculty Recognition Banquet", UIUC. (1999)
Program committee, 1st Annual AVS Spring Meeting, San Jose, CA. (1999)
Co-chairman of AVS-ICMCTF96: “Silicide” Session, San Diego, CA. (1994-1998)
Selected as co-chairman of 1995 MRS "Silicide" Symposium, Boston, MA. (1995)
Racheff Professor of Materials Science (1991-1993)