Univ. of Florida, Univ. of Illinois, Morgan State Univ., Northwestern Univ. Purdue Univ. Stanford Univ., UTEP nanoHUB.org – Toward On-Line Simulation for “Materials and Nanodevices by Design” 1 Gerhard Klimeck, Mark S Lundstrom, 1 M Korkusinski, H Xu, F Saied, S Goasguen, A Rahman, J Wang 2 TB Boykin, 3 F Oyafuso, S Lee, H Hua, O Lazarankova, RC Bowen, P von Allmen 1 Network for Computational Nanotechnology (NCN), Purdue University 2 University of Alabama in Huntsville 3 NASA Jet Propulsion Laboratory American Physical Society, March 22, 2005, Los Angeles
The NCN: Mission and Vision To support the National Nanotechnology Initiative through: • research • simulation tools • education and outreach • web-based services “To be the place where experiment, theory, and simulation meet and move nanoscience to nanotechnology.” NCN Morgan State University - Northwestern University - Purdue University - Stanford University - University of Florida - University of Illinois - University of Texas at El Paso 2
Simulation is Essential for Nanotechnology Development Hint from the Semiconductor Industry: • No new devices / circuits designed without software! Simulation Problem: • Accepted nano simulation tool suite does NOT exist. Approach: • Conduct research in Modeling and Simulation of: • Nanoelectronics • Nanoelectromechanics • Nano-bio sensors • Computational science • DEVELOP and DEPLOY to nanoscience and nanotechnology community Fabrication Characterization NCN Morgan State University - Northwestern University - Purdue University - Stanford University - University of Florida - University of Illinois - University of Texas at El Paso 3
NCN - Research nano-bio: nanoelectronics: NEMS: switches connecting molecules…. and sensors…. electronics and NEMS to biological systems V lipid 10.0 0.0 …to compact models protein water ….to MOSFETs -10.0 -30 -20 -10 0 10 20 30 Tip position (nm) 5.0 Tip Position (nm) S D 0.0 NCN 0.0 0.5 1.0 DC Bias (V) Morgan State University - Northwestern University - Purdue University - Stanford University - University of Florida - University of Illinois - University of Texas at El Paso 4
electronics at the molecular scale Al Ultra-Scaled CMOS Gate HfO 2 D S 10 nm SiO 2 p ++ Si ~ 2 nm D G S ~ 5 nm SWNT ~1-4nm Molecules NCN Morgan State University - Northwestern University - Purdue University - Stanford University - University of Florida - University of Illinois - University of Texas at El Paso 5
unifying view of small devices gate µ 1 µ 1 [ H ] [ � S ] S D [ � 2 ] [ � 1 ] non-equilibrium Green’s function approach (NEGF) NCN Morgan State University - Northwestern University - Purdue University - Stanford University - University of Florida - University of Illinois - University of Texas at El Paso 6
The NCN: Mission and Vision To support the National Nanotechnology Initiative through: • research • simulation tools (1-D transport, 3-D, Synthesis) • education and outreach • web-based services “To be the place where experiment, theory, and simulation meet and move nanoscience to nanotechnology.” NCN Morgan State University - Northwestern University - Purdue University - Stanford University - University of Florida - University of Illinois - University of Texas at El Paso 7
Resonant Tunneling Diode Current 12 different I-V curves: 2 wafers, 3 mesa sizes, 2 bias directions Voltage 50nm 1e18 InGaAs 7 ml nid InGaAs 7 ml nid AlAs Conduction band diagrams 20 ml nid InGaAs 7 ml nid AlAs for different voltages 7 ml nid InGaAs and the resulting current flow. 50 nm 1e18 InGaAs NCN Morgan State University - Northwestern University - Purdue University - Stanford University - University of Florida - University of Illinois - University of Texas at El Paso 8
NEMO the first Nano CAD Tool originally developed at Texas Instruments Current Atomistic Basis Sets Concepts Voltage p x p p z s y 5x d 2x spin • • • • • • • • • • • Quantitative Design, Analysis, Synthesis NCN Morgan State University - Northwestern University - Purdue University - Stanford University - University of Florida - University of Illinois - University of Texas at El Paso 9
NEMO Key Elements: Current Tight Binding sp 3 d 5 s* Realistically Extended Devices Concepts Non-Equilibrium Green Functions Voltage p x p p z s y 5x d 2x spin Transport / Engineering Quantum Mechanics / Quantitative Physics Design, Analysis, Synthesis NCN Morgan State University - Northwestern University - Purdue University - Stanford University - University of Florida - University of Illinois - University of Texas at El Paso 10
Ultra Thin Body SOI: A traditional Quantum Well? Most basic Five Atomic Layer quantum mechanical problem: Si (001) Particle in a box! 2 nd IEDM, Uchida 2 nd Expect / Remember: 1 st 1 st • State quantization • 2 counter-propagating states • 1 bound state L k 1 = � quantize k Schrödinger Equation E L � E � h 2 d 2 � ( ) = e + ik 1 z 2 propagating ( ) ( ) = 0 dz 2 � V z � z ( ) = e � ik 1 z � z � � � z 2 m * states � � 1 bound ( ) = sin k 1 z ( ) � z E = h 2 k 2 Parabolic state Dispersion k 2 m * NCN Morgan State University - Northwestern University - Purdue University - Stanford University - University of Florida - University of Illinois - University of Texas at El Paso 11
Quantum Wells - Special Considerations in Si Five Atomic layers Five Atomic Layer Si (001) 2 nd IEDM, Uchida TB ∆ E Sub 1 1 st Eff. mass Δ E=150meV= 6k B T effect at T=300K L k 1,2 = π /L k 1,2 = π /L 2 valleys 4 propagating states 2 bound states k 1,2 envelope k m fast oscillations NCN Morgan State University - Northwestern University - Purdue University - Stanford University - University of Florida - University of Illinois - University of Texas at El Paso 12
The NCN: Mission and Vision To support the National Nanotechnology Initiative through: • research • simulation tools (1-D transport, 3-D , Synthesis) • education and outreach • web-based services “To be the place where experiment, theory, and simulation meet and move nanoscience to nanotechnology.” NCN Morgan State University - Northwestern University - Purdue University - Stanford University - University of Florida - University of Illinois - University of Texas at El Paso 13
Quantum Dots: A Material / Device Testbed Multi-Million Atoms Simulations Designed Optical Transitions Sensors Quantum Dot Arrays Nanoscale Quantum States Atomic Orbitals Computing Structure (Artificial Atoms, size 20nm) size: 0.2nm Approach: Problem: •Use local orbital description for individual Nanoscale device simulation requirements: atoms in arbitrary crystal / bonding • Cannot use bulk / jellium descriptions, need configuration description of the material atom by atom •Use s, p, and d orbitals => use pseudo-potential or local orbitals Use GA for material parameter fitting • Consider finite extent/transport, not infinitely •Strain with VFF periodic •Custom eigensolver => local orbital approach • Demonstrated 64 Million Atom System • Need to include > 1 million atoms. Volume of => need massively parallel computers • 110x110x110 nm 3 • The design space is huge: choice of • 15x300x300 nm 3 materials, compositions, doping, size, shape. => need a design tool NCN Morgan State University - Northwestern University - Purdue University - Stanford University - University of Florida - University of Illinois - University of Texas at El Paso 14
Alloy Disorder Results: Problem: • Simulated >1000 dots with random cation • Cations are randomly distributed in alloy distributions. dots. • Inhomogeneous broadening factor of • Does alloy disorder limit electronic ~0.5-5meV due to alloy disorder. structure uniformity for dot ensembles? Impact: Approach: • Fundamental uniformity limit for ensemble • Simulate a statistical ensemble of alloyed of alloy-based quantum dots. dots. • Requires atomistic simulation tool. Simulation of Alloy Dot Ensemble Γ =~0.5-5meV E eh =1.05eV In 0.6 Ga 0.4 As Lense Shaped Dot Diameter=30nm,Height=5nm, GaAs embedded ~1,000,000 Atom Simulation, sp3s * basis In and Ga atoms are randomly distributed Measured Γ =34.6 meV (R. Leon, PRB, 58 , R4262) Inhomegenious Broadening? Examined Theoretical Lower Limit NCN Morgan State University - Northwestern University - Purdue University - Stanford University - University of Florida - University of Illinois - University of Texas at El Paso 15
Computational Nanotechnology NEMO 3-D: Electronic structure for 23 Million Atoms Performed on NSF Teragrid Result / Demonstrations / Impact: • 64 million atom strain - volume (110nm) 3 • 23 million atom electronic structure Volume (78nm) 3 or 15x178x178nm 3 • Determined long range extent of strain in self-assembled quantum dots NCN Morgan State University - Northwestern University - Purdue University - Stanford University - University of Florida - University of Illinois - University of Texas at El Paso 16
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