Stretchable, single crystalline Si for high performance electronics on elastomer

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Stretchable, single crystalline Si for high
performance electronics on elastomer
Technical Approach
Objectives - generation of stretchable,
single crystalline Si on elastomeric substrate
- understanding the mechanics/physics involved
- response of wavy Si/PDMS upon external strain
i.e., stretching/compression -
high-performance, stretchable single crystalline
Si electronic devices (diodes, transistors)
Stretchable Si elements
SOI
Peel-off PDMS Flip over
Box etching Bond pre-strained PDMS
Technical Accomplishments ? successfully
fabricated stretchable, wavy Si on PDMS, with
controllable wave properties ? good agreements
bet. experiments and mechanics models, both for
initial- and post- buckling ? high level of
strain (tension/compression), up to 25, is
applicable reversibly, without damaging the Si
? high performance, stretchable Si electronic
devices on elastomeric substrate (pn-diodes,
transistors)
dark
n
p
Al
Al
light
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A Stretchable Form of Single Crystal Si for High
Performance Electronics on Elastomeric Substrate
D.-Y. Khang and J. A. Rogers
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Table of Contents

• Introduction
• Generation of wavy, single crystalline Si on
  elastomeric substrate
• Buckling mechanics experiments and modeling
• Stretching/Compression of wavy Si/PDMS
  post-buckling analysis
• Stretchable electronic devices diode
  transistor
• Conclusions

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Flexible electronics
High performance electronic devices (circuits)
on large-area, unconventional substrate !
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Flexible electronics

• Materials
• Substrate plastics
• Semiconductor/Dielectric/interconnection
• organics oligomer, or polymer
• inorganics a-Si, p-Si, nanowires,
  nanoparticles
• Carbon nanotube
• Processings
• Non-flat substrate
• Large-area, low-cost processing methods
• Low temperature
• Devices
• Consistent (or, controllable) performances with
  folding, bending or rolling-up
• Interconnection (or, wiring) among devices for
  functional circuits
• stretchable metal wires for interconnection

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Stretchable, wavy Si/PDMS Fabrication
Fabricate thin ribbon Si elements
Si devices on SOI
Wavy Si devices on PDMS
Bond elements to prestrained elastomeric substrate
Pick-up onto PDMS at RT
PDMS
LdL
Peel off flip over
Flip-over
Peel back elastomer flip over
L
stretchable Si elements
Contact partially-cured PDMS cure at high T
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Stretchable, wavy Si Fabrication
15mm
15?
2?
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Wavy Si Buckling mechanics
Stiff material layer on soft substrate wrinkling
instability
EPDMS2 MPa, ESi130 GPa, vPDMS0.48, vSi0.27
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Wavy Si Buckling mechanics
Si thickness (h) effect
Built-in strain L ?/ ? L arc-length
(calculated from contour integral)
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Wavy Si Buckling mechanics
Stress (s) effect
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Wavy Si stretching/compression mechanics
Compression Initial
wavy state Stretching
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Wavy Si stretching/compression mechanics
Post-buckling analysis
Stretching
Compression
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Wavy Si stretching/compression mechanics
Maximum strain in wavy Si bending strain at
peak or trough of wavy Si radius of curvature
calculated from sine wave approximation
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Stretchable electronic devices pn diode
stretch/compr.
Al
Al
dark
p
n
stretch/compr.
light
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Stretchable electronic devices photodetector,
photovoltaics
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Stretchable electronic devices transistor (not
yet completed)
source
gate
drain
Si ribbon devices on SOI
How to transfer these devices onto PDMS ? (in
reliable, reproducible manner)
Effective passivation method(s) for Si devices
during HF etching ?
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Conclusions
? Fabrication of stretchable, wavy Si on PDMS ?
Good agreements between experiments and mechanics
model, for both initial- and post-
buckling behaviors of wavy Si/PDMS ? High level
of strain (tension/compression), up to 25,
could be achieved reversibly, without damaging
the Si ? High performance, stretchable single
crystalline Si electronic devices on
elastomeric substrate (pn-diodes, transistors)
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Acknowledgements
Mechanics modeling analysis Prof. Yonggang
Young Huang (Mech. Industrial Eng., UIUC) Dr.
Hanqing Jiang ( ) Schematic drawings Etienne
Menard Financial support DARPA