Solution based molecular circuit assembly

Chemically directed surface assembly

Molecular Circuits

Local Wiring

Contact hole for global wiring

Metallization of wiring templates

Chemical surface patterning including local wiring template

50 nm

MC

MC

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CD

Chemically Directed Surface Alignment and Wiring of Self-Assembled Nanoelectrical CircuitsChemically Directed Surface Alignment and Wiring of Self-Assembled Nanoelectrical CircuitsChemically Directed Surface Alignment and Wiring of Self-Assembled Nanoelectrical CircuitsChemically Directed Surface Alignment and Wiring of Self-Assembled Nanoelectrical Circuits

High-resolution chemical surface patterning

Molecular circuit assembly

References

‡ Department of Chemical Engineering, † Department of Chemistry and Biochemistry, § Department of Physics and Astronomy Brigham Young University, Provo, Utah 84602

MetallizationAbstract

Tasks• Molecular circuit assembly• High-resolution chemical surface patterning• Chemically directed assembly and

integration of MC’s on surfaces• High-selectivity, high-precision metallization

Overview

1) Enables creation of direct, strong covalent bonds to surfaces

2) Able to pattern in a liquid environment

3) Flexible for use with a range of surfaces and surface chemistries

4) Low cost5) Potential for making 10 nm features6) Parallel modification of substrates

possible with tip arrays

Techniques Capable of Patterning < 100 nm Features

Direct Strong Covalent Bonding of Molecules

Controllable Liquid Environment

Wide Range of Surfaces and Surface Chemistries

Inexpensive Possibility of Making a 10 nm Feature

Chemomechanical Patterning/Nanografting

Yes Yes Yes Yes Yes

Dip Pen Nanolithography Usually Not No Yes Yes Diffusion Limited?

Microcontact Printing Usually Not No Yes Yes UnlikelyAFM Mechanical Scribing and Nanoindending

No No No Yes Yes

c-AFM Oxidation No No No Yes Yes

UHV STM Patterning No No No No Yes

E-beam Lithography No No Yes No Unlikely

UV Photolithography No No Yes No Unlikely

• APDES Nanografted onto SiO2

• Selective metallization by electroless copper on scribed lines

• 80nm line width, possibility for 10-20nm widths exists

• Assembling in situ discrete circuits • Electroless plating for metallization of interconnects between circuit

elements• Metallization will occur preferentially on either DNA templates or on

chemomechanically modified regions

Results

AFM height image of a low- background ssDNA‑templated Ag nanowire

Broader Impacts Summary

J. Liu‡, K. A. Nelson‡, E. Bird‡, H. Conley§, T. Pearson§, T. Wickard†, L. Hutchins‡, D. R. Wheeler‡, R. C. Davis§, A. T. Woolley†, M. R. Linford†, and J. N. Harb‡

Chemically directed assembly and integration of MC’s

A high yield of individual properly aligned MCs at each site is desired. The assembly can be tuned using several molecular parameters including molecule flexibility, ligand length, induced steric constraints, and partial attachment binding affinity differences. Temperature cycling, selective ligation, and the use of multiple attach/rinse cycles will be explored to achieve the desired yield.

e'

f 'g'

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• Education of graduate students in a truly multidisciplinary environment.

• Education of undergraduate students in a positive mentoring environment.

• Involvement of local minority students in an outreach program focused on nanoscience and engineering.

• Development of a method for producing wiring and metallization at a density unmatched by any present or near-future process.

• Development, demonstration and dissemination of novel and transferable processes and enabling tools for nanotechnology.

Vcc

Vin1

Vout

Vin2

Vout

GND

Molecular NOR Gate

GND

Source

Gate

Drain

e-b-a' and a-d-h pFETs

g-d'-c and c'-b'-f nFETs

Gate

Source

Drain

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e

fg

h

DNA assembly of MC

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Vcc

Vin1

Vout

Vcc

Vin2

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Molecular NAND Gate

Results

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250 nm

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Results (single transistor template)

TEM images after metallization(A) Copper (B) SilverScale bars are 25 nm

(1-3) ~120 base oligonucleotides with complementary regions

(4) Internally biotinylated poly-T sequence (5) Streptavidin (A) Three-branched DNA assembly (B) Streptavidin-labeled three-armed DNA complex

AFM images of • (A-C) Three-branched DNA

structures• (D-F) Complexes with

streptavidin localized in the center

• White bar represents 25 nm in all images

Chemomechanically pattern DNA-Templates

This poster describes nanofabrication efforts underway at BYU by an interdisciplinary research group, ASCENT (ASsembled nanoCircuit Elements by Nucleic acid Templating) under NIRT funding (2007). This group seeks to combine the complementary advantages of bottom-up self-assembly with top-down patterning, with the goal of providing a process for fabrication of nanoelectronic circuits. Efforts are focused on the development and refinement of four key technologies: (1) solution-phase assembly of structures and templates, (2) high-resolution chemical surface patterning, (3) high-precision metallization of molecular templates, and (4) chemically directed assembly and integration of nanostructures on surfaces. Molecular circuits are self-assembled in solution using customized DNA templates (“test-tube circuits”). DNA self-assembly is particularly powerful because of the large number of possible nucleic-acid sequences that enable highly selective bonding of DNA strands to each other and to other molecules. Chemomechanical patterning, a method that we have developed, is used to chemically modify the SiO2 substrate. This chemical patterning will provide anchor points to attach and align the molecular circuits on the surface, as well as provide a means for local wiring to the anchored circuit, all with a resolution < 10 nm. Electroless metal plating of both the exposed DNA and chemically templated lines is used to electrically connect active circuit elements to each other and to the larger-scale architecture. The net result will be DNA-templated molecular circuits that have been aligned and wired locally on an oxide surface. Interconnect technology similar to that used currently in the semiconductor industry can then be applied to create the larger global wiring needed for practical devices based on the molecular circuits under development.

DNA-templated nanotube positioning

Solution assembly of DNA-based MC templates

Chemomechanical patterning

• H.A. Becerril, R.M. Stoltenberg, D.R. Wheeler, R.C. Davis, J.N. Harb, and A.T. Woolley, "DNA-Templated Three-Branched Nanostructures for Nanoelectronic Devices", JACS, vol. 127, (2005), p. 2828.

• K.A. Nelson, S.T. Cosby, J.C. Blood, M.V. Lee, D.R. Wheeler, R.C. Davis, A.T. Woolley, M.R. Linford, J.N. Harb, "Substrate Preparation for Nanowire Fabrication by Selective Metallization of Patterned Silane Monolayers", ECS Trans., vol. 1 (12), (2006), p. 17.

• H.A. Becerril and A.T. Woolley, "DNA Shadow Nanolithography", Small, vol. 3, (2007), p. 1534.

• M.V. Lee, K.A. Nelson, L. Hutchins, H.A. Becerril, S.T. Cosby, J.C. Blood, D.R. Wheeler, R.C. Davis, A.T. Woolley, J.N. Harb, M.R. Linford, "Nanografting of Silanes on Silicon Dioxide with Applications to DNA Localization and Copper Electroless Deposition," Chem. Mater. vol. 19 (2007), p. 5052

• “BYU” nanoshaved in C18DMS surface on SiO2

• Letters are indented approximately 2-4 Å

• Hydrophilic patterns created by nanografting a neat trifunctional silane through a monochlorosilane monolayer

• Features as small as ca. 10 nm are created

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Funding• National Science Foundation (CTS-0457370)• ACS Petroleum Research Fund (42461-G5)• U.S. Army Research Office (DAAD19-02-1-0353)

• National Science Foundation (NIRT) “Chemically Directed Surface Alignment and Wiring of Self-Assembled Nanoelectrical Circuits,” 2007 – 2011

I-V curve measured for a DNA-templated copper nanowire spanning electrodes separated by 7 microns

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