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Thesis Luzma

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Transcript of Thesis Luzma

Outline
Assembly of Highly-Conjugated Organic Molecules with Potential Applications in Molecular Electronics
Ensamblaje de Moléculas Orgánicas Altamente Conjugadas con Aplicaciones en Electrónica Molecular
Luz Marina Ballesteros Rueda
December 12 , 2012
th
Introduction
Collateral Issues
Physical

Lithographical

Economic

Advantages
Efficient
Stable
Reaserch group Background
Molecular Electronic Devices
Sandwich Devices
(Metal-Molecule-Metal)
Top Electrode
Several Deposition Methods Cause Different Problems
Conductor or Semiconductor
Assembly of Molecules
Self-assembly

Covalently Bonded Molecules on Carbon and Silicon

Langmuir-Blodgett
Scanning Probe Microscopy
Only Efficient for Research Purposes Not Suitable for the Market

Au NPs Generation by Hybrid LB Films
Direct and Indirect Metal Evaporation
Transfer Top Contact (Nanotransfer Printing, LOFO, PALO and MoPALO)
Surface-Diffusion-Mediated Deposition
Small Size

Speed

Assembly and Recognition

Synthetic Tailorability

Potential Low Cost
ITRS Challenges
New Metal-Molecule Interfaces

Top Electrode

Electrical Behavior
Reaserch group Background
Requirements and Protocols
Characterization Techniques
Langmuir-Blodgett Technique
Oligomeric Phenylene-Ethynylene
(OPE)
Highly Conjugated Structure
LB Films
Molecular Electronics
Restricted Metal-Molecule Interfaces
Different Terminal Groups can be Linked to the Substrate
NOPES
Metal-Molecule Interfaces
Top
Electrode

Molecular Nanostructures
Br-OPE-Br
Conclusions
Compound without Aliphatic Chains

Directionally Oriented Films

Influence of Asymmetry Molecular Contacts
Solvent:
3

CHCl :EtOH (4:1)
-5

1·10 M
C =
UV-vis Reflection
Blue-shift:
H-type 2D Aggregates
LB Film Characterization
QCM
Checking Directionality
LB Film Electrical Properties
STM
Appropriate Distance STM tip-Substrate
Directionally Oriented Films
at 0.10 nA
at 0.75 nA
at 1.50 nA
> 1.77 nm
1.77 nm
1.66 nm
Film Thickness: 1.77 nm
Molecular Contact Asymmetry
Highlights
HOPEA
New Group for Contacting with the Metal: Acetylene


Electrical Behavior: Asymmetric Contacts
Interest
Interest
Solvent:

C H :EtOH (2:1)
-5

1·10 M
C =
6
4
UV-vis Reflection
H-type 2D Aggregates: Blue-shift
LB Film Characterization
LB Film Electrical Properties
Non-resonant Tunneling Mechanism
Highlights
OPE2A
Interest
LB Film Electrical Properties
Non-resonant Tunneling Mechanism
QCM and XPS Experiments Showed that Bathochromic Shift of Films with Respect to the Solution is Due to the Presence of Lateral H-bond Interactions


XPS experiments Revealed that the Exterior Group is:



The Conductance Can Be Modulated by pH (Molecular Structure Control)
Highlights
A Supramolecular Structure
G-PEA
IBERO
UV-vis Characterization
Au(0) Generation
Photolysis
Thermolysis
Organic Fraction Elimination Checking
Au NPs Distribution
Distributed over the Whole Surface
Au(0) Verification
Existence of Au(0):
Confirmed
Pristine Film
after annealing
Electrode Generation does not Cause Any Short Circuit
Photolysis Method is not Reliable for Generation of the Metallic Top Electrode.

Thermolysis Method is Appropriate for the Rupture of the G-PEA to Produce Au(0).

C.V. Experiments Demonstrated that the Annealing does not Cause any Short Circuit or Damage in the Device.

AFM Images Showed that The NPs are Distributed over the Film Surface.
Highlights
Thermolysis Method (150 °C - 4 Hours) Produces a Break-up of C-Au-C Bond Leading to the Formation of Au (0).


AFM and SEM Experiments showed the Generation of NPs over the Whole Surface.
Highlights
STM: Nanosource
Light Generator
Polymerize Br-OPE-Br

Cut Bromine off and Lift Oligomer Chain

Measure STM-LE Spectrum
Procedure
Polymerize and STM-LE
Polymerization
LT-STM

Thermal Activation

Ag (111) Surface
Vertical Manipulation
Br-(OPE)n-Br on Ag(111): Cutting
Br-(OPE)n-Br on Ag(111): Lifting
STM-LE Measurements
Chemisorption and Physisorption interactions

to control thickness and molecular orientation
Localized Surface Plasmon (LSP) Spectrum Excited by Inelastic Tunneling Electrons

LSP Resonances Strongly Vary with Tip Shape and Tip-sample Distance
.
Photons above Electron Energy Threshold Emitted from a Molecular Junction
Two Possible Inelastic Tunneling Mechanisms:

Heat Generation
Electron Inelastic Scattering with Molecular Vibrations

Heat Absorption
Electron Absorbs Energy from Hot Vibrons
Successfully Polymerized on Ag(111) Surface Using Thermal Activation Method


Bromine Atom was Easily Dissociated from the Phenyl Group in the Nanowires Structures.


STM-LE Experiments for Molecular Junctions have Shown a Photon Emission Characteristic of the polymer chain.
Highlights
The Objectives Proposed at the Beginning of this Work has been Fulfilled:
Metal-Molecule Interface
Remarkable Results
Quality of Films
Electrical Properties
161.7
160.5
163.4
164.8
PM-IRRAS
All Molecules Directionally Oriented
Collapse
0.18 nm
2
84.1
87.8
+ 2.2 V
2005: "More than Moore"
2009: To Transform Molecular Electronics
into the State-of-the-Art Electronics
Close the Circuit
Surface Pressure vs. Area Isotherm
Compressing Process
Spreading Process
Substrate is Withdrawn from the Subphase.

The Hydrophilic Segment Interacts with Substrate
Substrate is Immersed into the Subphase.

The Hydrophobic Segment Interacts with Substrate
Transfer Process
Objectives of this Work
New Metal-Molecule Interfaces:
Nanowires Fabrication:
Br-OPE-Br
NOPES
Asymmetric and Symmetric Molecular Wires
Top Electrode:
Easy and Low Cost Alternative Methodology
To Polymerized and To Determine its Optoelectronic Properties
OPE2A
HOPEA
G-PEA
IBERO
Our Research Group Background
-1
Optimal Surface Pressure
of Transference:
15 mN·m
Cyclic
Voltammetry
XPS
Stretching
Phenyl ring
Scissoring
NH
2
Linear in the Low Voltage Region (-0.5 to 0.5 V)

Good Agreement with the Conductance Value by others OPEs Derivatives
Symmetrical and Sigmoidal Profile
Langmuir Film Characterization
Langmuir Film Characterization
Optimal Surface Pressure
of Transference:
18 mN·m
-1
Transference only Possible on Substrate Emergence.
Bathochromic Shift
Lateral H-bond
Interactions
Conjugation
Length
Increasing
Unexpected Result
Does the Terminal Carboxylic Group near the Substrate Have an H-bond?
Both Carboxylic Groups are in their Deprotonated Form.
C1s
AR-XPS
C1s
Advantages:
Increasing the Number of Metal-Molecule Interfaces.
Powder
Subphase pH = 5.9
(Water)
Subphase pH = 11.4
(Basic Aqueous)
More Effective Electrical Junctions Formed between Carboxylate Groups and the STM Tip
Photolysis or Thermolysis
Chemical Bonds between Gold and Organic Counterparts Broken
Au NPs: Generated
Suggested Strategy
160-168 °C in UHV conditions
Asymmetric Contact: Non-rectifying Behavior (NOPES and HOPEA)

New Metal Junction: Acetylene Group (HOPEA)

Modulation of Conductance by pH: Achieved (OPE2A)
Top Electrode
The rupture of the G-PEA and IBERO compounds:

Soft, Simple and Safe Alternative for Top Contact Problem in Metal-Monolayer-Metal Devices.
Molecular Nanostructure
The Fabrication of Nanostructures were Possible by Polymerization in LT-STM of Br-OPE-Br.


Molecular Junctions Have Shown a Photo Emission Characteristic of the Organic Material.
Advantanges
For SAM, 66% of Terminal Groups are Amine.
Biggest Challenge in M.E.
ITRS: International Technology Roadmap for Semiconductors
Sophisticated Nanotechnology Bottom-up Procedure
Fabrication of Well-ordered Films in 2D Systems
Freeing up the Fabrication of Metallic Top Electrode
Chemisorption and Physisorption Interactions
Permiting the Fabrication of Directionally Oriented Films
Molecular Electronics
The Use of
Molecules
or
Molecular

Assemblies

as Components in Electronic Devices

Stable
Devices
Rigid and Linear Structure
Interesting Physicochemical Properties
Traditionally Assembled by SA Method
> 54.7 º
LB Film Prepared on
Water Subphase
LB Film Prepared on
Basic Subphase
Compounds with a Gold Atom in the Structure

Soft and Simple Methodology
NOPES Forms Homogeneous, Stable and Directionally Oriented Films.

XPS, PM-IRRAS, and QCM Experiments Showed that:




Non-rectifying Behavior in spite of Asymmetric contacts.
It Was Effectively Linked to Substrate Through the Amine Terminal Group (Substrate–H N–OPE–SH)
It Was Effectively Linked to Substrate Through the Thiol Terminal Group (Substrate–S–OPE–NH )
2
HOPEA Forms Homogeneous and Stable L and LB Films

I-V Curves showed that Terminal Acetylene Moiety:




Metal-HOPEA-STM Tip Junction
An Efficient Linker for Electron Transport through Molecular Junctions

For Coupling Conjugated Molecular Backbones to Gold Terminals
Non-rectifying Behavior

Non-resonant Tunneling Mechanism
Symmetric Molecular Wire


Stable and Reproducible L and LB Films Prepared (using Water Subphase)
31 nm
61º
d = 1.77 0.05
XPS
d = 1.71 0.05
58º
Powder
Au-H N-OPE-SH
2
Au-S-OPE-NH
2
Experimental Data
U = 0.6 V
t
Practically identical Curves
Non-resonant Tunneling Mechanism
An Efficient Linker for Electron Transport through Molecular Junctions
Carboxylic Group when LB Film is Prepared on Water Subphase
Carboxylate Group when LB Film is Prepared on Basic Subphase
Chico et al. Inorganic Chemistry, 50, 2011
Photolysis or Thermolysis
Solution Characterization
351 nm
Au4f
Au4f
Do not Show
Au Plasmon
Au4f
Powder
Pristine
Film
After
Annealing
Lifted Molecule at 1.8 V
Confirming the Proposed Structure
Confirming the Proposed Structure
Supramolecular
Structure
H-bond
Interactions
π-π Stacking
QCM
LB Film Prepared on
Water Subphase
LB Film Prepared on
Basic Subphase
at 150 °C for 4 Hours
2
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