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Fabrication of Suspended Nanowire Structures Jason Mast & Xuan Gao

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Fabrication of Suspended Nanowire Structures Jason Mast & Xuan Gao. Summer 2009 REU Program at Case Western Reserve University. Nano == 1 / billion Nanometer == 1 meter / billion Nanowire == wire with diameter between 1-100 nm Suspended Nanowire == A nanowire suspended over a gap. - PowerPoint PPT Presentation
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Fabrication of Suspended Nanowire Structures Jason Mast & Xuan Gao Summer 2009 REU Program at Case Western Reserve University
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Page 1: Fabrication of Suspended Nanowire Structures Jason Mast & Xuan Gao

Fabrication of Suspended Nanowire Structures

Jason Mast & Xuan Gao

Summer 2009 REU Program at Case Western Reserve University

Page 2: Fabrication of Suspended Nanowire Structures Jason Mast & Xuan Gao

Introduction Nano == 1 / billion Nanometer == 1 meter / billion

Nanowire == wire with diameter between 1-100

nm

Suspended Nanowire == A nanowire suspended

over a gap.

Top – Nanowire on substrate

Bottom – Nanowire suspended over

gapBlack == MetalGreen == NanowireGray == Si/SiO2 substrate

Page 3: Fabrication of Suspended Nanowire Structures Jason Mast & Xuan Gao

Applications

Cell Device

Biology & MedicineElectrical Circuits

ω ω'

Sensors

Page 4: Fabrication of Suspended Nanowire Structures Jason Mast & Xuan Gao

Goals

1. Fabricate suspended nanowire devices- Simple but not easy.

2. Test the devices and look at the I-V curves.

- Should be different because the substrate (read heat sink) is not in contact with the wire.

Page 5: Fabrication of Suspended Nanowire Structures Jason Mast & Xuan Gao

Method IBasic Idea

1. Carve trenches out of top SiO2 layer.2. Drop nanowires over the trenches.3. Evaporate metallic contact pads.

Step 1 - Start

Blue == 100 nm SiO2 Gray == Silicon

Page 6: Fabrication of Suspended Nanowire Structures Jason Mast & Xuan Gao

Step 2 – Spin Coat Photoresist

Photoresist layers act like sacrificial layers. We use them to mold our devices.

Purple == LOR-3A Yellow == S 1805

Page 7: Fabrication of Suspended Nanowire Structures Jason Mast & Xuan Gao

Step 3 – Carve out Trenchesi. Place wafer under photomask, and expose the sample to UV light.

ii. Submerge in CD-26. Iiii. Submerge in HF for 60 sec.

Top View

Rate ~ 1 nm / sec

Page 8: Fabrication of Suspended Nanowire Structures Jason Mast & Xuan Gao

Step 4 – Drop nanowires

This can be done using either wet or dry transfer.

Page 9: Fabrication of Suspended Nanowire Structures Jason Mast & Xuan Gao

Step 5 – Contact Padsi. Expose 2nd pattern to UV light.

ii. Submerge in CD-26 for 60 sec.

Page 10: Fabrication of Suspended Nanowire Structures Jason Mast & Xuan Gao

Step 5 - cont.

Iiii. Evaporate metal (5 nm Ti & then 50 nm Al).

Different shades of gray represent different elevations of metal.

iv. Let the wafer sit in Remover PG overnight.

Page 11: Fabrication of Suspended Nanowire Structures Jason Mast & Xuan Gao

Method IIBasic Ideas

1. Embed nanowires between layers of photoresist.2. Create metallic contacts.

Step 1 – Get Started

Blue == 100 nm SiO2 Gray == Silicon

Page 12: Fabrication of Suspended Nanowire Structures Jason Mast & Xuan Gao

Step 2 – Spin coat photoresist

Yellow == Photoresist

Step 3 – Drop nanowires

Green == Nanowires

Page 13: Fabrication of Suspended Nanowire Structures Jason Mast & Xuan Gao

Step 4 – Spin coat photoresist

Nanowires are now embedded between two layers of photoresist.

Page 14: Fabrication of Suspended Nanowire Structures Jason Mast & Xuan Gao

Step 5 – Contact Pads

i. Place under photomask, and expose to UV light.

ii. Submerge in CD-26 for 60 sec.

Page 15: Fabrication of Suspended Nanowire Structures Jason Mast & Xuan Gao

Step 5 - cont

Iiii. Evaporate metal (5 nm Ti & 300 nm Al).

vi. Submerge in Remover PG overnight.

Page 16: Fabrication of Suspended Nanowire Structures Jason Mast & Xuan Gao

Results – Method I

I was able to perform alignment.

However, alignment was far too complicated to implement.

Page 17: Fabrication of Suspended Nanowire Structures Jason Mast & Xuan Gao

Results – Method II

I was able to get suspended nanowire structures.

I was able to get a few I-V curves, and a resistance measurement.

Page 18: Fabrication of Suspended Nanowire Structures Jason Mast & Xuan Gao
Page 19: Fabrication of Suspended Nanowire Structures Jason Mast & Xuan Gao
Page 20: Fabrication of Suspended Nanowire Structures Jason Mast & Xuan Gao

AcknowledgmentsSpecial Thanks To: Case Western Reserve University Physics Department National Science Foundation Bob Mike McDonald Professor Kash Reza Sharghi-Moshtaghin

NSF REU grant DMR-0850037


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