24-12-2012, 12:35 PM
Moletronics
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INTRODUCTION
Molecular electronics, one of the major fields of current efforts in nanoscience, involves the exploration of the electronic level structure, response and transport, together with the development of electronic devices and applications that depend on the properties of matter at the molecular scale. This includes single molecules, molecular arrays and molecular networks connected to other electronic components. Its major application areas include sensors, displays, smart materials, molecular motors, logic and memory devices, molecular scale transistors and energy transduction devices. Often molecular electronics is envisioned as the next step in device miniaturization. The importance of molecules in device applications stems not only from their electronic properties, but also from their ability to bind to one another, recognize each other, assemble into larger structures, and exhibit dynamical stereochemistry.
MOLECULAR ELECTRONICS AN OVERVIEW
Molecular electronics (sometimes called moletronics) is a branch of applied physics which aims at using molecules as passive (e.g. resistive wires) or active (e.g. transistors) electronic components.
The concept of molecular electronics has aroused much excitement both in science fiction and among scientists due to the prospect of size reduction in electronics offered by such minute components. It is an enticing alternative to extend Moore's Law beyond the foreseen limits of small-scale conventional silicon integrated circuits. As a result, molecular electronics is currently a very active research field.
Among the important issues is the determination of the resistance of a single molecule (both theoretical and experimental). Another problem faced by this field is the difficulty to perform direct characterization since imaging at the molecular scale is often impossible in many experimental devices.
HISTORY
Study of charge transfer in molecules was advanced in the 1940s by Robert Mulliken and Albert Szent-Gyorgi in discussion of so-called "donor-acceptor" systems and developed the study of charge transfer and energy transfer in molecules. Likewise, a 1974 paper from Mark Ratner and Avi Aviram 1 illustrated a theoretical molecular rectifier. Later, Aviram detailed a single-molecule field-effect transistor in 1988.
Apart from the Aviram and Ratner proposal, molecular electronics received an initial boost from the experimental discovery of conducting polymers in the mid-seventies. Before this date, organic molecules (which form crystals or polymers) were considered insulating or at best weakly conducting semi-conductors. In 1974, McGinness, Corry, and Proctor reported the first molecular electronic device in the journal Science. As its active element, this voltage-controlled switch used melanin, an oxidized mixed polymer of polyacetylene, polypyrrole, and polyaniline. The "ON" state of this switch exhibited extremely high conductivity. This device is now in the Smithsonian's collection of historic electronic devices. As Hush notes, their material also showed negative differential resistance, "a hallmark of modern advances in molecular electronics". Melanin is also the first example of a "self-doped" organic semiconductor, though McGinness et al also looked at dopants such as diethyamine.
ABOUT MOLECULAR ELECTRONICS
The guiding principle of this research is that biological systems can provide useful paradigms for developing electronic and computational devices at the molecular level. For example, natural photosynthetic reaction centers are photovoltaic devices of molecular dimensions, and the principles dictating the operation of reaction centers may be useful in the design of synthetic optoelectronic switches. In this project, several classes of molecular photovoltaic species are being synthesized and studied. These include porphyrin-fullerene dyads, carotenoid-fullerene dyads, a carotenoid-porphyrin-fullerene triad, carotene-porphyrin-imide triads, and molecular dyads and triads containing two porphyrin moieties.
The approach involves the design and synthesis of dyads, triads and other super molecular species using the techniques of organic chemistry. The newly-prepared molecules are then studied by a variety of physical methods, including time-resolved laser spectroscopy, NMR spectroscopy, and cyclic voltammetry in order to determine how and how well they functioned as molecular electronic elements. The information gained can then be used to design new generations of these molecules.
MOLECULAR ELECTRONICS TECHNOLOGY
The field of molecular electronics seeks to use individual molecules to perform functions in electronic circuitry now performed by semiconductor devices. Individual molecules are hundreds of times smaller than the smallest features conceivably attainable by semiconductor technology. Because it is the area taken up by each electronic element that matters, electronic devices constructed from molecules will be hundreds of times smaller than their semiconductor-based counterparts. Moreover, individual molecules are easily made exactly the same by the billions and trillions. The dramatic reduction in size, and the sheer enormity of numbers in manufacture, is the principle benefits offered by the field of molecular electronics.
At the heart of the semiconductor industry is the semiconductor switch. Because semiconductor switches can be manufactured at very small scales and in combination can be made to perform all desired computational functions, the semiconductor switch has become the fundamental device in all of modern electronics. California Molecular Electronics Corporation's Chiropticene® Switch is a switchable device that goes beyond the semiconductor switch in size reduction. This switch is a single molecule that exhibits classical switching properties.
TRANSCENDING MOORE’S LAW WITH MOLECULAR ELECTRONICS
The future of Moore’s Law is not CMOS transistors on silicon. Within 25 years, they will be as obsolete as the vacuum tube.
While this will be a massive disruption to the semiconductor industry, a larger set of industries depends on continued exponential cost declines in computational power and storage density. Moore’s Law drives electronics, communications and computers and has become a primary driver in drug discovery and bioinformatics, medical imaging and diagnostics. Over time, the lab sciences become information sciences, and then the speed of iterative simulations accelerates the pace of progress.
[attachment=45090]
INTRODUCTION
Molecular electronics, one of the major fields of current efforts in nanoscience, involves the exploration of the electronic level structure, response and transport, together with the development of electronic devices and applications that depend on the properties of matter at the molecular scale. This includes single molecules, molecular arrays and molecular networks connected to other electronic components. Its major application areas include sensors, displays, smart materials, molecular motors, logic and memory devices, molecular scale transistors and energy transduction devices. Often molecular electronics is envisioned as the next step in device miniaturization. The importance of molecules in device applications stems not only from their electronic properties, but also from their ability to bind to one another, recognize each other, assemble into larger structures, and exhibit dynamical stereochemistry.
MOLECULAR ELECTRONICS AN OVERVIEW
Molecular electronics (sometimes called moletronics) is a branch of applied physics which aims at using molecules as passive (e.g. resistive wires) or active (e.g. transistors) electronic components.
The concept of molecular electronics has aroused much excitement both in science fiction and among scientists due to the prospect of size reduction in electronics offered by such minute components. It is an enticing alternative to extend Moore's Law beyond the foreseen limits of small-scale conventional silicon integrated circuits. As a result, molecular electronics is currently a very active research field.
Among the important issues is the determination of the resistance of a single molecule (both theoretical and experimental). Another problem faced by this field is the difficulty to perform direct characterization since imaging at the molecular scale is often impossible in many experimental devices.
HISTORY
Study of charge transfer in molecules was advanced in the 1940s by Robert Mulliken and Albert Szent-Gyorgi in discussion of so-called "donor-acceptor" systems and developed the study of charge transfer and energy transfer in molecules. Likewise, a 1974 paper from Mark Ratner and Avi Aviram 1 illustrated a theoretical molecular rectifier. Later, Aviram detailed a single-molecule field-effect transistor in 1988.
Apart from the Aviram and Ratner proposal, molecular electronics received an initial boost from the experimental discovery of conducting polymers in the mid-seventies. Before this date, organic molecules (which form crystals or polymers) were considered insulating or at best weakly conducting semi-conductors. In 1974, McGinness, Corry, and Proctor reported the first molecular electronic device in the journal Science. As its active element, this voltage-controlled switch used melanin, an oxidized mixed polymer of polyacetylene, polypyrrole, and polyaniline. The "ON" state of this switch exhibited extremely high conductivity. This device is now in the Smithsonian's collection of historic electronic devices. As Hush notes, their material also showed negative differential resistance, "a hallmark of modern advances in molecular electronics". Melanin is also the first example of a "self-doped" organic semiconductor, though McGinness et al also looked at dopants such as diethyamine.
ABOUT MOLECULAR ELECTRONICS
The guiding principle of this research is that biological systems can provide useful paradigms for developing electronic and computational devices at the molecular level. For example, natural photosynthetic reaction centers are photovoltaic devices of molecular dimensions, and the principles dictating the operation of reaction centers may be useful in the design of synthetic optoelectronic switches. In this project, several classes of molecular photovoltaic species are being synthesized and studied. These include porphyrin-fullerene dyads, carotenoid-fullerene dyads, a carotenoid-porphyrin-fullerene triad, carotene-porphyrin-imide triads, and molecular dyads and triads containing two porphyrin moieties.
The approach involves the design and synthesis of dyads, triads and other super molecular species using the techniques of organic chemistry. The newly-prepared molecules are then studied by a variety of physical methods, including time-resolved laser spectroscopy, NMR spectroscopy, and cyclic voltammetry in order to determine how and how well they functioned as molecular electronic elements. The information gained can then be used to design new generations of these molecules.
MOLECULAR ELECTRONICS TECHNOLOGY
The field of molecular electronics seeks to use individual molecules to perform functions in electronic circuitry now performed by semiconductor devices. Individual molecules are hundreds of times smaller than the smallest features conceivably attainable by semiconductor technology. Because it is the area taken up by each electronic element that matters, electronic devices constructed from molecules will be hundreds of times smaller than their semiconductor-based counterparts. Moreover, individual molecules are easily made exactly the same by the billions and trillions. The dramatic reduction in size, and the sheer enormity of numbers in manufacture, is the principle benefits offered by the field of molecular electronics.
At the heart of the semiconductor industry is the semiconductor switch. Because semiconductor switches can be manufactured at very small scales and in combination can be made to perform all desired computational functions, the semiconductor switch has become the fundamental device in all of modern electronics. California Molecular Electronics Corporation's Chiropticene® Switch is a switchable device that goes beyond the semiconductor switch in size reduction. This switch is a single molecule that exhibits classical switching properties.
TRANSCENDING MOORE’S LAW WITH MOLECULAR ELECTRONICS
The future of Moore’s Law is not CMOS transistors on silicon. Within 25 years, they will be as obsolete as the vacuum tube.
While this will be a massive disruption to the semiconductor industry, a larger set of industries depends on continued exponential cost declines in computational power and storage density. Moore’s Law drives electronics, communications and computers and has become a primary driver in drug discovery and bioinformatics, medical imaging and diagnostics. Over time, the lab sciences become information sciences, and then the speed of iterative simulations accelerates the pace of progress.