Chemically Directed Surface Alignment and Wiring of Self-Assembled Nanoelectrical Circuits
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‡
‡ Department
of Chemical Engineering, † Department of Chemistry and Biochemistry, § Department of Physics and Astronomy
Brigham Young University, Provo, Utah 84602
Abstract
High-resolution chemical surface patterning
Chemomechanical patterning
1)
2)
3)
4)
5)
6)
Enables creation of direct, strong
covalent bonds to surfaces
Able to pattern in a liquid
environment
Flexible for use with a range of
surfaces and surface chemistries
Low cost
Potential for making 10 nm features
Parallel modification of substrates
possible with tip arrays
Techniques Capable of
Patterning < 100 nm
Features
Tasks
• Molecular circuit assembly
• High-resolution chemical surface patterning
• Chemically directed assembly and
integration of MC’s on surfaces
• High-selectivity, high-precision metallization
Results
Yes
Inexpensive Possibility
of Making
a 10 nm
Feature
Yes
Yes
Usually Not
No
Yes
Yes
Microcontact Printing
AFM Mechanical Scribing
and Nanoindending
c-AFM Oxidation
Usually Not
No
No
No
Yes
No
Yes
Yes
Diffusion
Limited?
Unlikely
Yes
No
No
No
Yes
Yes
UHV STM Patterning
No
No
No
No
Yes
E-beam Lithography
No
No
Yes
No
Unlikely
UV Photolithography
Direct Strong
Covalent
Bonding of
Molecules
Yes
Controllable
Liquid
Environment
No
No
Yes
No
•
•
•
APDES Nanografted onto SiO2
Selective metallization by electroless
copper on scribed lines
80nm line width, possibility for 10-20nm
widths exists
AFM height image of a lowbackground ssDNA-templated Ag
nanowire
80
Unlikely
Results
B
DNA-Templates
Chemomechanically pattern
Wide Range
of Surfaces
and Surface
Chemistries
Yes
Chemomechanical
Patterning/Nanografting
Dip Pen Nanolithography
Overview
A
• 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
Current (pA)
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 selfassembly 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 selfassembly 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.
Metallization
Before Cut
After Cut
60
A
40
B
20
0
-1.0
-0.5
-20 0.0
0.5
1.0
-40
-60
-80
Solution based
assembly
molecular
Chemical
surface
patterning
including
local wiring template
circuit
Volts
I-V curve measured for a DNAtemplated copper nanowire spanning
electrodes separated by 7 microns
MC
Broader Impacts Summary
D
C
MC
Molecular Circuits
50 nm
• 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.
Local Wiring
Contact hole for
global wiring
Chemically directed
assembly
surface
•
Metallization of wiring templates
•
Molecular circuit assembly
e-b-a' and a-d-h pFETs
Source
DNA assembly of MC
Molecular NOR Gate
Vcc
Hydrophilic patterns created by nanografting a neat
trifunctional silane through a monochlorosilane
monolayer
Features as small as ca. 10 nm are created
Results (single transistor template)
Vout
Vin1
Drain
a a'
h
d
d'
g-d'-c and c'-b'-f
nFETs
Source
g
Vin2
e
GND
b
b'
f
c c'
C
Gate
B
Drain
Vout
•
•
“BYU” nanoshaved in C18DMS
surface on SiO2
Letters are indented approximately
2-4 Å
Chemically directed assembly
and integration of MC’s
D
Gate
A
GND
Molecular NAND GateE
Vout
Vcc
Vcc
Vin1
Vin2
GND
Vout
(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
Solution assembly of DNA-based MC templates
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.
B
B
A
A
•
•
1000 nm
250 nm
DNA-templated nanotube positioning
•
TEM images after metallization
(A) Copper (B) Silver
Scale bars are 25 nm
•
•
•
•
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
Funding
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
References
h'
e'
g'
f'
• 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