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2016 Material Science Series http://bit.ly/2016MaterialScienceSeries
Thursday, March 10, 2016
Chemistry of Hello: Lithium Ion Batteries Challenges and Opportunities for Personal Electronics Applications Dee Strand, Chief Scientific Officer, Wildcat Discovery Technologies Mark Jones, Executive External Strategy and Communications Fellow, Dow Chemical
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“Exploratory Chemistry Research in US Industry: The Rise and Fall of DuPont Central Research” Bill Nugent, Visiting Scholar, Ohio State University (Formerly of DuPont CR&D) Alexander Tullo, Senior Editor, Chemical & Engineering News
Thursday, February 18, 2016
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2016 Material Science Series “Chemistry of Hello: The Next Generation of Circuitry”
Tobin Marks
Mark Jones
Professor of Catalytic Chemistry, Materials Science and Engineering, and Applied Physics at Northw estern University
Executive External Strategy and Communications Fellow, Dow Chemical
Co-Founder and Member of Scientific Advisory Board at the Polyera Corporation
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GOAL: FLEXIBLE ELECTRONIC CIRCUITRY RF ID tags, display backplanes, e-books, sensors, “smart” packaging, “smart” displays, photovoltaics, “internet of things”
Science Needed: Versatile, Unconventional Materials • • •
n-Type Organic Conductors for CMOS Better Gate Dielectrics Better Understanding of Charge Transport, Interfaces
Basic Building Block: Field-Effect Transistor (FET) NRC/National Academies, “The Flexible Electronics Opportunity” National Academies Press, 2014
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Transistor Structure & Function Output plot
VD VG
semiconductor source charge carriers drain dielectric
gate / substrate
NO CHARGE CARRIERS BETWEEN s AND d => ID = 0
OFF VG = 0
ON VG 0
CREATES CHARGE CHANNEL IN SEMICONDUCTOR LAYER => ID 0
New Materials Must Optimize: • Carrier mobility () & Stability • Current on/off ratio (Ion/Ioff) • Threshold voltage (VT) • Subthreshold swing (SS) • Dielectric capacitance (Ci)
Transfer plot
LCD Display Backplanes use a-Si:H ~ 0.5 cm2/V∙s-1Ion/Ioff > 106 n-type only, poor current carrier
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Lecture Outline I. Introduction, Challenges, Opportunities II. New n-Type Organics Rylenedimides source
III. Nanoscopic Dielectrics Self-Assembled Nanodielectrics (SAND)
drain
Semiconductor
Dielectric
Gate
IV. Amorphous Oxides Transistors
V. Conclusions, Acknowledgments 14
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Materials Design for n-Type Semiconductors Enablers of Organic CMOS p-Type = Radical cation (h+) conductor through highest occupied MOs (HOMOs) n-Tyep = Radical anion (e-) conductor through lowest unoccupied MOs (LUMOs)
R
R
Substituents Enhance solubility
X
Molecule
X
Substituents Lower HOMO, LUMO energies for electron transport, environmental stability
Flat architecture - stacking Extended system to minimize Marcus reorganization energy
High-yield coupling chemistry
R
R
Linker
X
Polymer
X
n
Reviews: MRS Bulletin, 2010, 35, 1018; Accts. Chem. Res. 2011, 44,501; Chem. Rev. 2014, 114, 8943.
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Cyanoperylenes. Completely Air-Stable n-Type Semiconductors High-yield syntheses Good packing for efficient transport Reduction potentials close to 0 V !(vs SCE) Low-lying LUMO (est. -4.77 eV) Smooth, interconnected films
CN O
O
R N
N R
O
O NC
R = fluoroalkyl, alkyl, etc.
General : air stability, Ion:Ioff, Vth tunable via CN, R substituents Suitable molecular packing, electrochemistry, film formation Crystal Structure
AFM
Electrochemistry Current (e-6)
1.0
0.5
0.0
-0.5
-1.0
1.5
1.0
0.5
0.0
-0.5
-1.0
-1.5
Voltage
Rylene review: Advanced Materials, 2011, 23, 268.
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Status of n-Type Molecule, Polymer Development Best: Printable n-type air-stable polymer, μ > 2.0 cm2/Vs
AMBIPOLAR N-TYPE AMBIPOLAR P-TYPE
N-TYPE AMBIPOLAR
P-TYPE AMBIPOLAR
Northwestern Start-up
Nature 2009, 457, 679
Theoretical Guidance. Molecular Cluster, Band Structure Approaches Band Structure
n- vs. p- related to LUMO and Homo energies HOMO, LUMO bandwidths comparable Twisting from cofacial orientation energetically favorable, greater bandwidths
Marcus reorganization energies very important M. Ratner, G. Hutchison, S. Koh, R. Ortiz, A. Freeman J. Am. Chem. Soc., 2005, 127, 2339 ; 2005, 127,16866; Advan. Funct. Mater, 2008, 18, 332; J. Phys. Chem. C, 2016, submitted t18
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Inkjet-Printed Bithiophene-Imide-Based Air-Stable Complementary Polymer Inverters Gain ~ 40 at VDD = - 100V
Guo, X.; Ortiz, R. P.; Noh, Y.-Y.; Baeg, K.-J.; Facchetti, A.; Marks, T. J. J. Am. Chem. Soc..2015, in press.
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Audience Survey Question ANSWER THE QUESTION ON BLUE SCREEN IN ONE MOMENT
Which of the following statements are TRUE? 1. All that is needed for an organic semiconductor is a molecular π system 2. Whether an organic semiconductor is p-type or n-type is largely a function of the associated HOMO and LUMO energies 3. Electrical conductivity = mobility x carrier concentration
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Audience Survey Question ANSWER THE QUESTION ON BLUE SCREEN IN ONE MOMENT
Which of the following statements are TRUE? 1. All that is needed for an organic semiconductor is a molecular π system 2. Whether an organic semiconductor is p-type or n-type is largely a function of the associated HOMO and LUMO energies 3. Electrical conductivity = mobility x carrier concentration
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Need for Better Gate Dielectrics Motivates Self-Assembled Nanodielectric (SAND) Importance Low mobility of unconventional semiconductors Lower operating voltages crucial for practical electronics Large densities of trapped charge → hysteresis
Typical Organic FET Data
Gate Dielectric Functions as capacitor Stabilizes charged carriers induced by gate electric field + ++ ++ ++ ++ ++ +
Semicond.
Parallel plate capacitor model
Ci
k d
Intel: HfO2
0
D
S
ISD~ VG Ci
G
Dielectric - - -- - - -- - - -- - - - -
SAND
Ci = capacitance per area, k = dielectric constant ε0 = vacuum permittivity, d = thickness
How to increase Ci : Increase dielectric constant (κ) Reduce thickness (d) ReviewsAdvan. Mater. 2009; Chem. Rev. 2010; Accts. Chem. Res. 2014
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SAND Gate Dielectrics Enhance Organic & Inorganic Transistor Performance •
n- and p-Type Organic Semiconductors: Molecular and Polymer
•
Sorted Carbon Nanotubes, Graphene
•
ZnO and In2O3 Nanowires ( μ = 3000 cm2/Vs)
•
GaAs, MoS2
•
Oxide Thin Films
•
Conventional Si and Nanomembrane Si
Si Nanomembrane TFTs
Radiation-Hard SAND TFTs
Active Matrix ZnO NW/SAND OLED Display
Materials module deployed on the International Space Station. Inset: SAND-based transistors fabricated by Northwestern scientists Reviews: Advan. Mater. 2009, 21, 1407; Chem. Rev., 2010, 110, 205; Accts. Chem. Res. 2014
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Next-Generation SANDs Customized for Specific Function Type III SAND Non-Ambient Growth Hydrocarbon Solvents
V-SAND Zr-SAND & Hf-SAND VA-SAND Ambient Growth Vapor Growth Vapor Growth Avoid Solvents Avoid Solvents Alcohol Solvents ALD Al2O3
ALD Al2O3 MRS Bulletin, 2010, 35, 1018; J. Am. Chem. Soc., 2011, 133, 10239; ACS Nano, 2012; Accts. Chem. Res. 2014 24
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Zr, Hf-SAND Self-Assembled Nanodielectrics TEM Cross-section
• Organic/inorganic hybrid multilayer • Solution processable under ambient • Controllable thickness, large-area uniformity, well-defined nanostructure • High capacitance, superior insulating properties • 350° C thermal stability
Fabrication • Self-assemble phosphonic acid-based polarizable π-molecule • Spin coat ultra-thin ZrOx primer & interlayers
Organic/Inorganic TFTs Pentacene
Capacitance characteristics
Zn-Sn-O
800
2
Capacitance (nF/cm )
600 800 2
400
Capacitance (nF/cm )
Properties M-SAND-4 (4 layer) • Leakage: 10 -7 A/cm2 @2 MV/cm • C: 465 nF/cm2 (Zr), 1 μF/cm2 • k ≈ 11 (Zr), 20 (Hf) • Roughness(RMS): 1
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Sangwan, Hersam, Marks, APL, 2014, 104, 083503
SAND Design. First-Principles Calculation of Dielectric Response in Molecule-Based Materials Scheme for plane-wave DFT computation of static dielectric response:
ηstatic(z) ηstatic(z) w/ substitution
ηstatic(z) versus coverage
ε = 2.39; Experiment: ε = 2.34
•
Benzene Crystal: Computation:
•
First powerful tool for the design of new hybrid dielectric materials Heitzer, Marks, Ratner, JACS, 2013; JACS, 2015
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Materials Design. First-Principles Calculation of Dielectric Response in SAND-Type Materials How to increase dielectric constant (ε) and capacitance (C) of molecular films?
Typical organic films have ε ≈ 3.0, C < 1.0 μF/cm2
High Surface Coverage Low Polarizability
Low Surface Coverage Large Polarizability
ε ~ 3.0
ε ~ 3.0
High Surface Coverage Computed dielectric constant of polyenes with polarizable substituents achieve ε > Large Polarizability 12 at 4 molecules/nm2 coverage dielectric constant of alkane & ε =Computed Dielectric Constant ε > 12.0Heitzer, Marks, Ratner, ACS Nano 2014; JACS 2015. alkyne chains at varying surface coverages. ε > 7.0 (C > 3.0 μF/cm2)
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Technology Motivation
Transparent Electronics Will Use Oxide TFTs + Organics Transparent Displays
Heads-up Displays Artefactgroup.com
Samsung Transparent OLED TV
Xconomy.com Sharp IGZO Displays
Amorphous Oxide Driving Electronics: In-Ga-Zn-O? Can We Hybridize with Organic Materials?
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Audience Survey Question ANSWER THE QUESTION ON BLUE SCREEN IN ONE MOMENT
Which of the following statements are TRUE? 1. Any polarizable substance will be a good gate dielectric for transistors 2. HfO2 is superior to SiO2 as a transistor gate dielectric because it is denser
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Audience Survey Question ANSWER THE QUESTION ON BLUE SCREEN IN ONE MOMENT
Which of the following statements are TRUE? NONE 1. Any polarizable substance will be a good gate dielectric for transistors 2. HfO2 is superior to SiO2 as a transistor gate dielectric because it is denser
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TRANSPARENT CONDUCTING OXIDE (TCO) ELECTRONIC STRUCTURE MODEL J. Goodenough
Energy
Metal Cation Conduction Band np
• Lies above top of O-2pπ VB by ΔEgap ≥ 3.1eV • Low enough in energy to accept electrons
ns
CB
εF
• Itinerant electrons cannot be excited into higher
ED
band by light absorption
Dope to make conductive (e.g., Sn in In2O3)
Cation Requirements Usually Met by VB
O2-: 2p6
• 5s CB of Cd2+, In3+, Sn4+
N(ε) (DOS)
• Burstein-Moss increase in ΔEgap with doping
What are the Limitations and Implications of this Picture? Can We Use These for TFTs? Freeman, Medvedeva Zunger PNAS 2002, JACS, 2007, MRS Bulletin, 2010, 35, 1018
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Attractions of Amorphous Oxide Semiconductors (AOSs) for High-Performance TFTs Disordered Crystal Structures
•
High Mobility
•
Low Deposition &
Processing Temperatures •
Very Smooth Surfaces, No Grain Boundaries
•
Mechanical Flexibility
•
Optical Transparency
•
Properties Tunable between
Film XRD and Electron Diffraction
Insulating, Semiconducting, Highly Conducting by Doping
Bellingham, Hosono, Fortunato, Mason, Wager
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Transparent a-Zn-In-Sn-O TFTs Grown by Pulsed Laser Deposition
Protective Layer
Transmittance ~75% (glass ~90%) TFT Performance: μ ~160 cm 2/V·s (~20 on SiO2) VG & VDS ~1.0 V VT ~0.2 V Ion:Ioff ~105 Chang, Marks Advan. Mater. 2010, 22, 2333; J. Am. Chem. Soc. 2010, 132, SS ~0.13 V/decade 11934.
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Low Temperature Combustion Synthesis of a-Oxide Films
Solution Precursors Reaction Characterization Conventional Combustion
Product DTA (V/mg)
Combustion Condensed Oxide Lattice
Conventionalll
Reaction Coordinate
2
(cm /Vs)
1
10
In2O3
Exo
20
20
0 100
100
0
In2O3
75
50
50
25 200 400 600 o Temp ( C)
1
10
-1
10
-3
10
-5
10
-7
10
-1
10
-3
10
-3
Al2O3
10
dielectric -7
200 300 400 o Temp ( C)
10
-5
10
ZTO 200 300 o 400 Temp ( C)
-5
10
200 400 600 o Temp ( C)
TCO Conductivity
Combustion
1
IZO
75
25
10
-1
10
40
10
Transistor Performance (Si/SiO2 Substrates)
Conventional
60
30
IZO 200 300 400 o Temp ( C)
Conductivity (S/cm)
Ignition
Mass (%)
Energy
Oxidizer + Organic Fuel
3
10
1
10
-1
10
ITO
200 300 400 500 o Temp ( C)
Kim, Fachetti, Kanatzidis, Marks Nature Materials 2011,10, 382; JACS 2016, in press.
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Result: Inkjet Printed, Combustion-Processed Flexible Amorphous In2O3 Transistors on Plastic Transistor Characterization Printed a-In2O3
VDS = 1V
VG =1.00V
2.0 1E-7
I DS IG
1E-8
IDS (A)
IDS & IG (A)
1E-6
500 m
3.0
1E-5
1.0 0.80V
1E-9 1E-10 -0.5 0.0 0.5 1.0 VG (V)
Research Agenda • Materials Scope • Microstructure Evolution • Performance Limits, SAND
0.0
0.60V
0.0
0.5 1.0 VDS (V)
Plastic: μ = 8 cm2/V·s Ion:Ioff ~ 104 Glass: μ = 40 cm2/V·s Ion:Ioff ~105 a-Al2O3 Gate Dielectric SAND Also Works 37
Kim, Fachetti, Kanatzidis, Marks Nature Materials 2011,10, 382; JACS 2015, in press.
Inkjet-Printed Combustion a-IGZO on Hf-SAND Dramatic operating voltage reduction
SiO2 Dielectric μ ≈ 5 cm 2/Vs High operating voltage
Hf-SAND Dielectric μ MAX > 40 cm2/Vs All-solution processed
