Molecular Electronics
Molecular Electronics
A Seminar Report submitted in partial fulfillment of the requirement for the award of the
degree of
BATCHELOR OF TECHNOLOGY
in
ELECTRONICS & COMMUNICATION ENGINEERING
by
i
CERTIFICATE
submitted by Manchala Ankitha Sai (20211A04C6) in partial fulfilment of the requirement for the award
of the degree of B.Tech in Electronics and Communication Engineering by Jawaharlal Nehru Technological
University (JNTU), Hyderabad is a record of bonafide work carried out by him/her under my guidance and
The summary and findings presented in this Seminar Report have been verified and found to be
satisfactory.
EXTERNAL EXAMINER
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CENTER FOR VLSI DESIGN
Dept of Electronics and Communication Engineering
B.V Raju Institute of Technology
Vishnupur, Narsapur, Medak Dist.
CERTIFICATE
This is to certify that the following student of B.V. Raju Institute of technology
have undertaken the project titled “MOLECULAR ELECTRONICS” at the Center
for VLSI Design (CVD) under the esteemed guidance of “Dr. Pavan Kumar Bikki,
Ph.D.” from to and have completed the project successfully.
The results presented in this mini project have been verified and are found to be
satisfactory.
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ACKNOWLEDGEMENTS
We take this opportunity to express our indebt gratitude to the persons who contributed for our work, for
being our inspiration and guide which led to the successful completion of the Seminar Report.
We are grateful towards our College Management and our beloved Principal Dr. Sanjay Dubey, Ph.D., for
providing us the necessary infrastructure and facilities that ensured smooth and satisfactory execution of the
Seminar Report.
We would like to express our profound gratitude to our head of the department Dr. B R. Sanjeeva Reddy,
Ph.D., Professor & HOD, Department of Electronics and Communication Engineering, for his
encouragement, inspiration, close monitoring and guidance he gave me during the execution of the Seminar
Report.
We express our sincere thanks to Dr. Pavan Kumar Bikki, Ph.D., Assistant Professor, Dept. of ECE, our
guide, for his valuable suggestions and motivation in successful completion of the Seminar report. We also
wish to express our thanks to all the faculty members and laboratory staff that were helpful both directly and
Regards
Manchala Ankitha Sai(20211A04C6)
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DECLARATION
We hereby declare that the Seminar entitled “MOLECULAR ELCETRONICS” submitted to B V Raju
Institute of Technology, affiliated to Jawaharlal Nehru Technological University (JNTU), Hyderabad, for
the degree of Bachelor of Technology (B.Tech) in Electronics and Communication Engineering (ECE) is a
It is further declaring that the Seminar Report on any part, therefore, has not been previously submitted to
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ABSTRACT
The pursuit of molecular electronics seeks to overcome the limitations posed by traditional semiconductor-
based technology. By leveraging molecular diversity and exploiting quantum effects at the molecular level,
researchers envision revolutionary electronic components offering unparalleled computational density,
reduced power consumption, and potential biocompatibility. These advancements hold promise for
applications in nanoelectronics, quantum computing, wearable technology, and biomedical devices.
However, the field encounters challenges in precise assembly techniques, understanding electron transport
within molecules, and integrating molecular-scale components into scalable and practical devices. Despite
these hurdles, the potential for molecular electronics to reshape electronics as we know it, fostering smaller,
faster, and more energy-efficient devices, propels ongoing research and positions it at the forefront of
technological innovation. As advancements continue, molecular electronics holds the promise of
transforming various industries and catalyzing the development of next-generation electronic technologies.
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CONTENTS
CERTIFICATE II
ACKNOWLEDGEMENTS IV
DECLARATION V
ABSTRACT VI
CONTENTS VII
INTRODUCTION 01
LITERATURE SURVEY 02
CHAPTERS:
1. MOLECULAR ELECTRONICS 03
2. METHODOLOGY 04
9. DISADVANTAGES 15
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10. CONCLUSION 16
11. REFERENCES 17
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INTRODUCTION
Molecular electronics stands at the frontier of scientific exploration, merging disciplines like
nanotechnology, chemistry, and electronics to revolutionize the landscape of electronic device fabrication.
This groundbreaking field delves into leveraging individual molecules as building blocks for creating novel
electronic components and circuits at the molecular scale. By harnessing the distinctive properties of
molecules – their size, shape, and electronic behavior – researchers aim to transcend the limitations of
conventional silicon-based technology.
At the heart of molecular electronics lies the aspiration to craft ultra-miniaturized, high-performance
electronic systems that hold the promise of unmatched computational power and energy efficiency.
Molecular-scale components, including switches, wires, diodes, and transistors, herald a new era of
electronic devices capable of operating at the nanoscale.
However, realizing the full potential of molecular electronics requires overcoming challenges in
precise molecular assembly, understanding electron transport within molecules, and integrating these tiny
components into scalable and practical devices. Despite these obstacles, the prospects of molecular
electronics remain incredibly promising, driving ongoing research and paving the way for transformative
advancements in electronics, computing, and various industries reliant on technological innovations.
1
LITERATURE SURVEY
5. A brief history of molecular 05 june 2003 Mark Ratner Learnt how molecular
electronics electronics was
invented.
CHAPTER-1
MOLECULAR ELECTRONICS
2
Molecular Electronics is also called as Moletronics. Molecule is small particle of chemical element
or compound that has the chemical properties of that element. Molecular electronics is a branch of applied
physics which aims at using molecules as passive or active electronic components. These molecules will
perform the functions currently performed by semiconductors.
Molecular electronics involves the designing of molecular systems that are capable of long-distance electron
transport through donor-bridge-acceptor (D-B-A) systems. In these systems, charge transport has been
extensively studied with different bridge molecules such as DNA, proteins, porphyrins, and saturated and
unsaturated hydrocarbons.
Three scientists, namely Alan Heeger, Hideki Shirakawa, and Alan MacDiarmid have made noteworthy
contributions to the growth in electric conductive polymers and were also awarded the Nobel Prize
in Chemistry for their significant work in the field of molecular electronics. Many interesting areas, for
example, molecular switches, molecular rectifiers, DNA electronics, and negative differential-resistance
junctions have also been described in molecular electronics, but it is still uncertain whether these can find
commercial-level applications or not.
3
CHAPTER-2
METHODOLOGY
The methodology of molecular electronics involves several key steps and approaches:
3. Assembly Techniques:
Developing methods to assemble individual molecules into functional electronic components and
circuits. Techniques may include self-assembly processes, nanolithography, and chemical deposition
to precisely position molecules in desired configurations.
4
7. Theoretical Modeling and Simulation:
Employing computational models and simulations to predict and understand molecular behavior,
aiding in the design and optimization of molecular-scale components and devices.
This multidisciplinary approach involves collaboration between chemists, physicists, materials scientists,
and engineers to advance the field of molecular electronics, aiming to create ultra-miniaturized, high-
performance electronic systems with potential applications in various industries.
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CHAPTER-3
WORKING PRINCIPLE OF MOLECULAR ELECTRONICS
When a molecule or molecular wire structure contacts a metal, one deals with a mix of continuous
energy states in extended structures (the macroscopic electrodes) and discrete energy levels in nanoscale
structures (the molecule). After contact, a single common Fermi level will be defined, such that states with
energies below that Fermi level will be occupied, and states above will be empty (at zero temperature). The
molecular eigenstates, the energy levels that describe the isolated molecule, will shift and broaden as they
come into equilibrium with the metal.
Figure 1
From Figure 1 Schematics of (a) a molecular light emitting diode (LED) and (b) a molecular wire junction
(MJW). The continuum electrodes are the same for each, and in each there is an interface problem labeled
by IC at the cathode and IA at the anode end. In the MWJ, the molecule can pass current, and that current
can be modulated either by an external gating potential (noted G) or by binding a substrate molecule
(denoted by S). In the LED structure, the light is emitted from a molecular structure labeled em, and the
holes and electrons pass through specific organic transport layers HTL and ETL, respectively. MA and MC
are respectively thin modulation layers at cathode and anode, which substantially change the character and
balance of the photoemission structure.
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Figure 2
From Figure . 2 Energy level diagrams for the simple MWJ of Fig. 1b. The continuous hemispherical
structures are metallic bands, with the Fermi level indicated by the solid dark line. In (a), the lines represent
atomic orbitals within the molecular wire, and the double headed arrows are potential Hamiltonian
interactions between these localized orbitals. In (b), the molecular Hamiltonian has been diagonalized, and
the energy levels correspond to the molecular orbitals.
Figure 2a is an energy level diagram showing local energy levels along the molecular wire that mix
with one another and with the continuous levels of the electrodes (here indicated as hemispherical band
structures). The Fermi level separating the occupied and unoccupied levels of the metal lies between the
highest energy molecular orbital and the lowest unoccupied molecular level. If an electron were placed in
one of the unoccupied orbitals in Figure 2b it would have a finite lifetime, before relocalizing in the metal.
The lifetime associated with the molecular states is equivalent to the mixing of those molecular states
with the electrode. Since that process will mediate electron transfer between the discrete molecule and the
continuous electrode, knowledge of the self-energy is equivalent to knowledge of the electronic
mixing/injection. This is important, because work on metal/molecule binding self-energies is called
Molecular electrons. A given molecule will have different energy levels, denoted by Es . A given interface
will be characterized by the mixing matrix τ. Generally, Hm(described by an electronic structure model
Hamiltonian) describes not an isolated molecule, but ‘an extended molecule’ that incorporates several
surface atoms. This is necessary because the covalent bonding and charge transfer at the interface must be
described with great accuracy. Self-consistency must be attained between electrode and molecule – both
charge flows and potential must be equilibrated. Geometric change upon forming the molecular junction
may be very significant. In MWJs with thickness less than a few nanometers, such injection cannot occur. In
molecular optoelectronic devices, characteristic dimensions are substantially larger (nanometers to microns),
and injection processes will dominate.
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CHAPTER-4
REGIMES FOR TRANSPORT IN MOLECULAR JUNCTION
Transport in molecular junctions can manifest in various regimes due to the distinct electronic properties of
molecules and their interactions with electrodes. Some different regimes include:
Understanding and characterizing these different transport regimes are crucial for designing and optimizing
molecular electronic devices and exploring their diverse applications in fields like nanoelectronics, sensing,
and quantum computing.
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CHAPTER-5
MOLECULAR ELECTRONIC DEVICES
Molecular electronic devices encompass a wide range of devices where individual molecules or
molecular assemblies serve as functional elements or building blocks. These devices utilize the unique
electronic properties of molecules to perform specific functions. Some notable examples include:
1. Molecular Wires:
Single molecules or chains of molecules that act as conductive pathways for electron transport,
forming the basis of molecular-scale wires in nanoelectronics.
2. Molecular Diodes:
Devices based on asymmetric molecular structures that enable the preferential flow of electrical
current in one direction, analogous to semiconductor diodes but at the molecular scale.
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3. Molecular Transistors:
Utilizing individual molecules or molecular assemblies as the active elements for amplification,
switching, or controlling electron flow in electronic circuits, resembling the functionality of traditional
semiconductor transistors.
4. Molecular Sensors:
Sensing devices employing specific molecules or molecular structures to detect and respond to
external stimuli such as light, gases, or biomolecules. These sensors find applications in healthcare,
environmental monitoring, and chemical analysis.
5. Molecular Memories:
Non-volatile memory devices utilizing molecular-scale properties to store and retrieve information,
offering potential advantages in data storage density and energy efficiency.
6. Molecular Machines:
Nanoscale devices or machines constructed from molecular components that perform mechanical
tasks or logic operations. These could include molecular motors, switches, and logic gates operating
at the molecular level.
Research and development in molecular electronics aim to exploit the unique properties of molecules to
create ultra-small, high-performance, and energy-efficient electronic devices. These devices hold promise
for a wide array of applications in various fields, ranging from traditional electronics to quantum computing
and biotechnology.
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CHAPTER-6
SEMICONDUCTOR DEVICES VS MOLECULAR ELECTRONICS
Semiconductor devices and molecular electronics represent two distinct approaches to electronic device
fabrication, each with its unique characteristics:
Semiconductor Devices:
1. Materials:
Semiconductor devices are typically fabricated using crystalline materials like silicon, germanium, or
compound semiconductors (such as gallium arsenide).
2. Scaling:
They operate at a larger scale, using microscale or macroscale structures, allowing for the integration
of millions to billions of transistors on a single chip.
3. Manufacturing:
The manufacturing process involves lithography, doping, etching, and deposition techniques in
cleanroom environments, following well-established semiconductor fabrication processes.
4. Properties:
They exhibit stable and predictable electronic behaviors, offering high performance, reliability, and
well-understood characteristics, enabling the foundation for modern electronics.
5. Applications:
Widely used in conventional electronics for various applications, including computers, mobile
devices, sensors, and power devices.
Molecular Electronics:
1. Materials:
Molecular electronics utilizes individual molecules or molecular assemblies as functional components,
exploiting the unique electronic properties of molecules.
2. Scaling:
Operates at the molecular or nanoscale, allowing for the creation of highly compact and potentially
more energy-efficient electronic components.
3. Manufacturing:
Involves techniques like self-assembly, molecular deposition, and nanolithography to assemble and
manipulate individual molecules to create devices.
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4. Properties:
Molecules offer diverse electronic properties, enabling the design of customizable, energy-efficient,
and potentially highly functional electronic components.
5. Applications:
Still in research stages, molecular electronics hold promise for future applications in quantum
computing, nanoelectronics, biosensors, and other novel technologies.
While semiconductor devices have dominated the electronics industry for decades due to their scalability,
reliability, and established manufacturing processes, molecular electronics offer exciting possibilities for
highly miniaturized, energy-efficient devices with potential applications in emerging fields such as quantum
computing and nanotechnology. Both approaches contribute to advancing electronic technology, each
catering to specific needs and exploring different frontiers in device fabrication and functionality.
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CHAPTER-7
WHY USE MOLECULAR ELECTRONICS?
1. Speed:
Molecular electronics, operating at the nanoscale, potentially enable faster operations due to the
shorter distance electrons need to travel within molecular circuits, leading to reduced propagation
delays.
2. Power:
Molecular electronics, leveraging reversible and quantum-compatible properties, may dissipate
minimal energy, contributing to reduced power consumption and dissipation compared to traditional
semiconductor-based electronics.
3. Size:
The small size of molecules allows for ultra-compact electronic components and circuits at the
nanoscale. This potential miniaturization enables higher device density and the ability to pack more
functionalities within a smaller space.
5. Ease of Manufacturing:
The potential use of self-assembly and bottom-up techniques in molecular electronics could simplify
manufacturing processes compared to the complex and costly procedures involved in traditional
semiconductor fabrication. This might lead to more streamlined and cost-effective production
methods.
6. Miniaturization:
Molecules are inherently small, enabling the creation of ultra-compact electronic components and
circuits at the nanoscale, potentially surpassing the limitations of conventional semiconductor-based
technology in miniaturization.
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CHAPTER-8
APPLICATIONS OF MOLECULAR ELECTRONICS
1. Quantum Computing:
Leveraging molecules' quantum properties for qubits and quantum information processing.
Molecules could offer advantages in maintaining quantum coherence, enabling advancements in
quantum algorithms and computing.
These applications showcase the broad potential of molecular electronics in revolutionizing various
industries, from electronics and computing to healthcare, energy, and environmental sustainability.
However, the practical realization of these applications requires addressing technological challenges and
advancing research in molecular assembly, integration, scalability, and reliability.
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CHAPTER-9
DISADVANTAGES
1. Fabrication Challenges:
Precise assembly and fabrication of molecular-scale components into functional devices at scale is
extremely challenging.
2. Stability and Reliability:
Ensuring the stability and reliability of molecular devices, especially under varying environmental
conditions, remains a significant hurdle.
3. Molecular electronics must still be integrated with Silicon.
4. The transition from traditional silicon-based technology to molecular electronics may face resistance
and require substantial retooling in existing industries.
5. Integration with Existing Technology:
Integrating molecular-scale components into existing semiconductor-based technologies may require
significant modifications and compatibility issues, impacting widespread adoption.
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CHAPTER-10
CONCLUSION
Continued research and development are crucial to overcoming current limitations and realizing the
transformative potential of molecular electronics. Collaborative efforts in molecular assembly techniques,
interface engineering, and understanding molecular behaviors will pave the way for practical applications.
With sustained innovation and strategic advancements, molecular electronics holds the promise of reshaping
the future of electronics, offering highly efficient, versatile, and miniaturized devices that could redefine the
boundaries of electronic engineering.
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CHAPTER-11
REFERENCES
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[3] Ratner, Mark. "A brief history of molecular electronics." Nature nanotechnology 8.6 (2013): 378-381.
[4] Carroll, R. Lloyd, and Christopher B. Gorman. "The genesis of molecular electronics." Angewandte
Chemie International Edition 41.23 (2002): 4378-4400.
[5] Flood, Amar H., et al. "Whence molecular electronics?." Science 306.5704 (2004): 2055-2056.
[6] Cuevas, Juan Carlos, and Elke Scheer. Molecular electronics: an introduction to theory and experiment.
2010.
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