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Nanowires

Nanowires Zhong Lin Wang Semiconductor nanowires (NWs) are wires only a few nanometers in size that do not occur naturally. They represent an important broad class of nanometer-scale wire structures, which can be rationally and predictably synthesized in single-crystal form with all their key parameters controlled during growth: chemical composition, diameter, length, doping, and so on. Semiconductor NWs thus represent one of best-defined and best-controlled classes of nanoscale building blocks, which correspondingly have enabled a wide range of devices and integration strategies. For example, semiconductor NWs have been assembled into nanometer-scale field effect transistors (FETs), p-n diodes, light-emitting diodes (LEDs), bipolar junction transistors, complementary inverters, complex logic gates, and even computational circuits that have been used to carry out basic digital calculations. It is possible to combine distinct NW building blocks in ways not possible in conventional electronics. Leveraging the knowledge base of chemical modifications of inorganic surfaces can produce semiconductor NW devices that achieve new functions and produce novel device concepts.

Carbon Nanotubes

Carbon Nanotubes Brent Segal Since their discovery in 1991 by Sumio Iijima, carbon nanotubes have fascinated scientists with their extraordinary properties.[1] Carbon nanotubes are often described as a graphene sheet rolled up into the shape of cylinder. To be precise, they are graphene cylinders about 12nm in diameter and capped with end-containing pentagonal rings. One would imagine that a new chemical such as this would be discovered by a chemist, slaving away in front of a series of Bunsen burners and highly reactive chemicals, with a sudden epiphany being revealed in a flurry of smoke or precipitation from a bubbling flask. However, carbon nanotubes were discovered by an electron microscopist while examining deposits on the surface of a cathode; he was performing experiments involving the production of fullerenes, or buckyballs. This discovery presents one of the key tenets of nanotechnology. Novel tools allow researchers to observe materials and properties at the nanoscale that often have existed for hundreds or thousands of years and to exploit the properties of such materials. After Iijima's fantastic discovery, various methods were exploited to produce carbon nanotubes in sufficient quantities to be further studied. Some of the methods included arc discharge, laser ablation, and chemical vapor deposition (CVD).[2] The general principle of nanotube growth involves producing reactive carbon atoms at a very high temperature; these atoms then accumulate in regular patterns on the surface of metal particles that stabilize the formation of the fullerenes, resulting in a long chain of assembled carbon atoms. The arc-discharge methodology produced large quantities of multiwalled nanotubes (MWNTs), typically greater than 5nm in diameter, which have multiple carbon shells in a structure resembling that of a Russian doll. In recent years, single-walled nanotubes (SWNTs) using this method also have been grown and have become available in large quantities. The laser ablation method of carbon nanotube growth produced SWNTs of excellent quality but requires high-powered lasers while producing small quantities of material. The CVD method was pioneered by Nobel Laureate Richard Smalley and colleagues at Rice University, whose experience with fullerenes is nothing short of legendary. This growth technique is aided by a wealth of well-known inorganic chemicals specifically involving the formation of highly efficient catalysts of transition metals to produce primarily single-walled nanotubes. Novel Properties Although carbon nanotubes have a suitably interesting structure, there are a multitude of important properties that impart the potential for novel applications of significant commercial value. Multiwalled and single-walled nanotubes have similar properties, and for illustration, focusing on single-walled nanotubes provides a reasonable primer of the primary features. Some of these properties include remarkable strength, high elasticity, and large thermal conductivity and current density. Several reports have determined that SWNTs have a strength of between 50 and 100 times that of steel.[3] The elasticity of SWNT is 11.2 terrapascal (TPa), a measure of the ability of a material to return to its original form after being deformed. Imagine a molecule that, on the atomic scale, is as strong as steel but flexible like a rubber band! Despite these structural properties, SWNTs have a thermal conductivity almost as great as twice that of diamond, which is known to be one of the best conductors of heat. Perhaps one of the most impressive properties of SWNTs involves their electrical conductivity, which is reported to be 109 Amps per square centimeter, which is about 100 times that reported in copper, the conductor of choice for nearly every electrical device in common use today. SWNTs have two types of structural forms, which impart an additional set of electrical characteristics. Depending upon the alignment of the carbon atoms in the cylindrical form, SWNTs can be either achiral (having atomic uniformity along its axis) or chiral (having a twisted alignment from the uniform case). Achiral and chiral forms can act as metals or semiconductors and yet retain the same basic nanotube structural motif. In addition to these well-known properties, SWNTs have other features that make them attractive beyond their scientific novelty. SWNTs have a density approximately half that of aluminum, making them an extremely light material. SWNTs are stable at temperatures up to 2700°C under vacuum. This is truly impressive considering the melting point of Ruthenium, Iridium, and Niobium metals are about the same temperature.[4] Although nanotubes have structural uniformity, the carbon atoms within them have the same precise features as a typical graphene sheet. These atoms can be derivitized to alter the structure of the SWNTs, allowing their properties to be tailored. This allows nanotubes to be subject to literally hundreds of years of rich organic chemistry. Carbon nanotubes not only can be functionalized to change their structure but also can interact beneficially with organic chemicals that have biological usefulness. Fullerene materials have been explored for use as antioxidants, drug-delivery agents, and amino acid replacements; the latter could lead to new drug candidates. Reports have been published of their benefits in enhancing virus-specific antibody responses or as a scaffold for growing retinal epithelial cells to be transplanted into the retina to treat macular degeneration.[5] Manufacturing and Scaling Issues Carbon nanotube synthesis in recent years has been driven by yields and cost. To move nanotubes from scientific curiosity to practicality, they must be available in sufficient quantities at a reasonable cost with high uniformity and reproducibility. In the case of MWNTs, the arc-discharge method provides a good alternative, yielding large quantities of material at a good cost. In the case of SWNTs, while generating large quantities of material, the purity is often unacceptable for a subset of applications because of excessive carbonaceous contamination. Instead, the CVD method and a recent alternative, plasma-enhanced chemical vapor deposition (PECVD), have burst onto the scene as the methods of choice for producing large quantities of SWNTs with micron lengths, purity, and reliability within specifications for certain applications. PECVD has been reported to lower the temperature of nanotube growth significantly by using a plasma to generate the reactive carbon atoms instead of very high temperatures, as in standard CVD growth. In the case of nanoelectronicsperhaps one of the early applications for which SWNTs will be adoptedextremely high purity nanotubes are required, and only a few providers have managed to generate such materials at a reasonable cost. The key issue with respect to commercial use of nanotubes for most applications comes in placing wafers on silicon or silicon on insulators, which are typical substrates for making circuits or devices. To the extent that alignment or specific orientation is required, applicability has been limited. Two general methodologies exist for proceeding toward manufacturability of devices: specific growth using prepatterned catalysts , or patterning of nonoriented fabrics using application of solutions. In the former case catalysts are placed in specific regions of a substrate onto which nanotubes grow in either a vertical or a horizontal direction. Vertically oriented growth has been demonstrated by several groups and is especially valuable for field emitting devices. Many potential CNT device approaches using CVD growth of SWNTs suffer from manufacturability and scalability issues, primarily because typical CVD temperatures are >800°C for SWNTs. At such high temperatures, other steps in a fabrication process can be adversely affected, causing the yields of working devices to be lower. Indeed this a serious limitation if the underlying substrate or control electronics cannot withstand such temperatures. Some reports have presented data on lower-temperature methods of growing SWNTs using techniques such as PECVD. These techniques are still in their infancy but could represent a reasonable pathway for certain types of devices or applications. Horizontal fabrics have been applied to substrates whose thickness can be controlled by solution concentration and application procedure. Such methods have conquered the issues of purification of nanotube solutions, distribution of networks of nanotubes of uniform density over large substrates, and patterning of traces of conductive nanotubes into shapes that can be further integrated into complicated process flows. SWNTs can be obtained in bulk from various suppliers, which have exploited advanced CVD techniques to grow SWNTs in large scale of excellent quality. These nanotubes can then be purified to remove metallic contaminants (for example, Group IA and IIA elements) used in the growth process and carbonaceous species that serve as a potential source of contamination. The processed SWNTs are solubilized and can then be applied to device substrates for further processing. Potential Applications A variety of potential applications exist for carbon nanotubes. MWNTs have been reported for use primarily as a composite for batteries and as field emitters for television monitors.[6] As the price for these materials continues to drop, other potential applications, especially as additives in composites, are likely. The molecular nature of carbon nanotube fabrics allows various CNT physical properties, including electromagnetic, mechanical, chemical, and optical behaviors, to be exploited to create integrated electronic devices (including nonvolatile memory devices); chemical, biological, and radiation sensors; passive low-resistance, low-capacitance conformal interconnects; and electromagnetic field emission devices, scaffolds for cell growth, antioxidants, and near infrared imaging tags for biological samples and cells, to name a few. Table 13-1 summarizes a number of proposed applications that could use SWNT fabrics as an enabling component.[7] Table 13-1. Sample applications of single-walled carbon nanotube fabrics. Semiconductors Life Sciences Instrumentation Nonvolatile and volatile memory Membranes Mechanical relays and switches Programmable logic devices Chemical absorption Thermal sensors and actuators Global and local interconnects Valves Acceleration sensors Inductors Nanomixers Bolometers Radio frequency (RF) components Heat exchangers Gyroscopes Micromirrors Nanochannels Field emission tips displays Chip-to-chip interconnects Reaction chambers Acoustic/Pressure sensors Transistors Nanofluidics devices Radiation detectors One existing application for which SWNTs are particularly useful is in the arena of electronics, specifically to create nonvolatile memory.[8] In the case of nonvolatile memory applications, significant progress has been made in using fabrics, or assemblages of SWNTs, as electrical traces within integrated circuits.[9] These fabrics retain their molecular-level properties while eliminating the need for nanoscale physical control. These monolayers are created by room-temperature spin-coating of a solution of SWNTs in a semiconductor-grade solvent. After evaporation of the solvent, the resulting monolayer fabric is lithographically patterned and etched in an oxygen plasma. The process of spin-coating SWNT solutions can be used to produce monolayer fabric of very steep aspect ratios, which allows coverage of fabrics over sharp edges or tall structures. Such diversity in the coating of nanotube fabrics on three-dimensional structures has the potential to support traditional horizontal integration schemes in electronics as well as a novel set of devices oriented in a vertical fashion that could lead to significantly more dense electronics. The combination of patterned nanotube fabrics and the use of fabricated sacrificial layers around the fabric allows the formation of an open cavity, in which a suspended patch of fabric can be mechanically drawn into electrical contact with an electrode. These devices, called molecular microswitches (MMSs), can be used as storage elements for memory or logic applications. The SWNT fabric approach uses a 12-nm thick patterned SWNT fabric and can be interconnected monolithically with additional standard semiconductor (for example, CMOS) circuitry above or below, providing buffering and drive circuitry to address and control the MMS devices. When this technique is used, the limit to the scalability of the hybrid nanotube/ CMOS system depends only on the available photolithographic node. Hence, the CMOS fabrication, and not the inclusion of nanotubes, remains the limiting factor in scaling. Indeed, the ultimate physical limit to the integration density of this approach scales down to two individual metallic nanotubes and their electromechanical interaction.

Venture Capital Investing

Venture Capital Investing

Venture Capital Investing

Daniel V. Leff

Venture capital is money that is typically invested in young, unproven companies with the potential to develop into multibillion-dollar industry leaders, and it has been an increasingly important source of funds for high-technology start-up companies in the last several years. Venture capitalists are the agents that provide these financial resources as well as business guidance in exchange for ownership in a new business venture. VCs typically hope to garner returns in excess of 3050 percent per year on their investments. They expect to do so over a four- to seven-year time horizon, which is the period of time, on average, that it takes a start-up company to reach a liquidity event (a merger, acquisition, or initial public offering).

Very few high-tech start-up companies are attractive candidates for VC investment. This is especially true for nanotechnology start-ups, because the commercialization of nanoscience is still in its nascent stages. Companies that are appropriate for VC investment generally have some combination of the following five characteristics: (1) an innovative (or disruptive) product idea based on defensible intellectual property that gives the company a sustainable competitive advantage; (2) a large and growing market opportunity that is greater than $1 billion and is growing at more than 2030 percent per year; (3) reasonable time to market (one to three years) for the first product to be introduced; (4) a strong management team of seasoned executives; and (5) early customers and relationships with strategic partners, with a strong likelihood of significant revenue.

An early-stage start-up company rarely possesses all of these characteristics and often does not need to in order to attract venture financing. Indeed, early-stage start-ups are often funded without complete management teams, strategic partners, or customers. Absent these characteristics, however, there should be, at a minimum, a passionate, visionary entrepreneur who helped develop the core technology and wants to play an integral role in building the company.

The Commercialization of Nanotechnology

The Commercialization of Nanotechnology Nanotech is often defined as the manipulation and control of matter at the nanometer scale (critical dimensions of 1 to 100nm). It is a bit unusual to describe a technology by a length scale. We certainly didn't get very excited by "inch-o technology." As venture capitalists, we start to get interested when there are unique properties of matter that emerge at the nanoscale and that cannot be exploited at the macroscale world of today's engineered products. We like to ask the start-ups that we are investing in, "Why now? Why couldn't you have started this business ten years ago?" The responses of our nanotech start-ups have a common thread: Recent developments in the capacity to understand and engineer nanoscale materials have enabled new products that could not have been developed at larger scale. Various unique properties of matter are expressed at the nanoscale and are quite foreign to our "bulk statistical" senses (we do not see single photons or quanta of electric charge; we feel bulk phenomena, like friction, at the statistical or emergent macroscale). At the nanoscale, the bulk approximations of Newtonian physics are revealed for their inaccuracy and give way to quantum physics. Nanotechnology is more than a linear improvement with scale; everything changes. Quantum entanglement, tunneling, ballistic transport, frictionless rotation of superfluids, and several other phenomena have been regarded as "spooky" by many of the smartest scientists, even Einstein, upon first exposure. For a simple example of nanotech's discontinuous divergence from the "bulk" sciences, consider the simple aluminum soda can. If you take the inert aluminum metal in that can and grind it down into a powder of 2030nm particles, it will spontaneously explode in air. It becomes a rocket fuel catalyst. In other words, the energetic properties of matter change at that scale. The surface-area-to-volume ratios become relevant, and even the distances between the atoms in a metal lattice change from surface effects. Innovation from the Edge Disruptive innovation, the driver of growth and renewal, occurs at the edge. In start-ups, innovation occurs out of the mainstream, away from the warmth of the herd. In biological evolution, innovative mutations take hold at the physical edge of the population, at the edge of survival. In complexity theory, structure and complexity emerge at the edge of chaosthe dividing line between predictable regularity and chaotic indeterminacy. And in science, meaningful disruptive innovation occurs at the interdisciplinary interstices between formal academic disciplines. Herein lies much of the excitement about nanotechnology: in the richness of human communication about science. Nanotech exposes the core areas of overlap in the fundamental sciences, the place where quantum physics and quantum chemistry can cross-pollinate with ideas from the life sciences. In academic centers and government laboratories, nanotech is fostering new discussions. At Stanford, UCLA, Duke, and many other schools, the new nanotech buildings are physically located at the symbolic hub of the schools of engineering, computer science, and medicine. Nanotech is the nexus of the sciences, but outside the sciences and research itself, the nanotech umbrella conveys no business synergy whatsoever. The marketing, distribution, and sales of a nanotech solar cell, memory chip, or drug delivery capsule will be completely different from each other and will present few opportunities for common learning or synergy. Market Timing As an umbrella term for a myriad of technologies spanning multiple industries, nanotech will eventually disrupt these industries over different time framesbut most are long-term opportunities. Electronics, energy, drug delivery, and materials are areas of active nanotech research today. Medicine and bulk manufacturing are future opportunities. The National Science Foundation predicts that nanotech will have a trillion-dollar impact on various industries within 15 years. Of course, if one thinks far enough in the future, every industry eventually will be revolutionized by a fundamental capability for molecular manufacturingfrom the inorganic structures to the organic and even the biological. Analog manufacturing will become digital, engendering a profound restructuring of the substrate of the physical world. Futuristic predictions of potential nanotech products have a near-term benefit. They help attract some of the best and brightest scientists to work on hard problems that are stepping-stones to the future vision. Scientists relish exploring the frontier of the unknown, and nanotech embodies the tangible metaphor of the inner frontier. Given that much of the abstract potential of nanotech is a question of "when" and not "if," the challenge for the venture capitalist is one of market timing. When should we be investing, and in which subsectors? It is as if we need to pull the sea of possibilities through an intellectual filter to tease apart the various segments into a time line of probable progression. That is an ongoing process of data collection (for example, the growing pool of business plan submissions), business and technology analysis, and intuition. Two touchstone events for the scientific enthusiasm for the timing of nanotech were the decoding of the human genome and the dazzling visual images output by the scanning tunneling microscope (such as the arrangement of individual xenon atoms into the IBM logo). These events represent the digitization of biology and mattersymbolic milestones for accelerated learning and simulation-driven innovation. More recently, nanotech publication has proliferated, as in the early days of the Internet. In addition to the popular press, the number of scientific publications on nanotech has grown by a factor of 10 in the past ten years. According to the U.S. Patent and Trademark Office (USPTO), the number of nanotech patents granted each year has skyrocketed by a factor of 3 in the past seven years. Ripe with symbolism, IBM has more lawyers working on nanotech than engineers. With the recent codification of the National Nanotech Initiative into law, federal funding will continue to fill the pipeline of nanotech research. With $847 million earmarked for 2004, nanotech was a rarity in the tight budget process; it received more funding than was requested. Now nanotech is second only to the space race for federal funding of science. And the United States is not alone in funding nanotechnology. Unlike many previous technological areas, we aren't even in the lead; Japan outspends the United States each year on nanotech research. In 2003, the U.S. government spending was one-fourth of the world total. Federal funding is the seed corn for nanotech entrepreneurship. All of our nanotech portfolio companies are spin-offs (with negotiated intellectual property [IP] transfers) from universities or government labs, and all got their start with federal funding. Often these companies need specialized equipment and expensive laboratories to do the early tinkering that will germinate a new breakthrough. These are typically lacking in the proverbial entrepreneur's garage. Corporate investors have discovered a keen interest in nanotechnology, with internal R&D, external investments in start-ups, and acquisitions of promising companies, such as chipmaker AMD's recent acquisition of Coatue, a molecular electronics company. Despite all this excitement, there are a fair number of investment dead ends, and so we continue to refine the filters we use in selecting companies to back. All entrepreneurs want to present their businesses as fitting an appropriate time line to commercialization. How can we guide our intuition to determine which of these entrepreneurs are right? The Question of Vertical Integration Nanotech involves the reengineering of the lowest-level physical layer of a system, and so a natural business question arises: How far forward do you need to vertically integrate before you can sell a product on the open market? For example, in molecular electronics, if you can ship a DRAM-compatible chip, you have found a horizontal layer of standardization, and further vertical integration is not necessary. If you have an incompatible 3-D memory block, you may have to vertically integrate to the storage subsystem level, or farther, to bring a product to market. That may require that you form industry partnerships, and it will, in general, take more time and money as change is introduced farther up the product stack. Three-dimensional logic with massive interconnectivity may require a new computer design and a new form of software; this would take the longest to commercialize. And most start-ups on this end of the spectrum would seek partnerships to bring their vision to market. The success and timeliness of that endeavor will depend on many factors, including IP protection, the magnitude of improvement, the vertical tier at which that value is recognized, the number of potential partners, and the needed degree of tooling and other industry accommodations. Product development time lines are impacted by the cycle time of the R&D feedback loop. For example, outdoor lifetime testing for organic light-emitting diodes (LEDs) will take longer than in silicon simulation spins of digital products. If the product requires partners in the R&D loop or multiple nested tiers of testing, it will take longer to commercialize. The Interface Problem As we think about the start-up opportunities in nanotechnology, an uncertain financial environment underscores the importance of market timing and revenue opportunities over the next five years. Of the various paths to nanotech, which of them are 20-year quests in search of a government grant, and which are market-driven businesses that will attract venture capital? Are there co-factors of production that require a whole industry to be in place before a company ships products? As a thought experiment, imagine that I could hand you today any nanotech marvel of your designa molecular machine as advanced as you would like. What would it be? A supercomputer? A bloodstream submarine? A matter compiler capable of producing diamond rods or arbitrary physical objects? Pick something. Now imagine some of the complexities: Did it blow off my hand as I offered it to you? Can it autonomously move to its intended destination? What is its energy source? How do you communicate with it? These questions draw the interface problem into sharp focus: Does your design require an entire nanotech industry to support, power, and interface to your molecular machine? As an analogy, imagine that you have one of the latest Intel Pentium processors. How would you make use of the Pentium chip? You then need to wire-bond the chip to a larger lead frame in a package that connects to a larger printed circuit board, fed by a bulky power supply that connects to the electrical power grid. Each of these successive layers relies on its larger-scale precursors (which were developed in reverse chronological order), and the entire hierarchy is needed to access the potential of the microchip. Where Is the Scaling Hierarchy for Molecular Nanotech? To cross the interface chasm, today's business-driven paths to nanotech diverge into two strategies: the biologically inspired bottom-up path, and the top-down approach of the semiconductor industry. The developers of nonbiological micro-electromechanical systems (MEMS) are addressing current markets in the micro world while pursuing an ever-shrinking spiral of miniaturization that builds the relevant infrastructure tiers along the way. Not surprisingly, this path is very similar to the one that has been followed in the semiconductor industry, and many of its adherents see nanotech as inevitable but in the distant future. On the other hand, biological manipulation presents numerous opportunities to effect great change in the near term. Drug development, tissue engineering, and genetic engineering are all powerfully impacted by the molecular manipulation capabilities available to us today. And genetically modified microbes, whether by artificial evolution or directed gene splicing, give researchers the ability to build structures from the bottom up. The Top-Down "Chip Path" This path is consonant with the original vision of physicist Richard Feynman (in a 1959 lecture at Caltech) of the iterative miniaturization of our tools down to the nanoscale. Some companies are pursuing the gradual shrinking of semiconductor manufacturing technology from the MEMS of today into the nanometer domain of nanoelectromechanical systems (NEMS). MEMS technologies have already revolutionized the automotive industry with air-bag sensors, and the printing sector with ink-jet nozzles, and they are on track to do the same in medical devices and photonic switches for communications and mobile phones. In-StatJMDR forecasts that the $4.7 billion in MEMS revenue in 2003 will grow to $8.3 billion by 2007. But progress is constrained by the pace (and cost) of the semiconductor equipment industry, and by the long turnaround time for fab runs. Many of the nanotech advances in storage, semiconductors, and molecular electronics can be improved, or in some cases enabled, by tools that allow for the manipulation of matter at the nanoscale. Here are three examples: Nanolithography: Molecular Imprints is commercializing a unique imprint lithographic technology developed at the University of Texas at Austin. The technology uses photo-curable liquids and etched quartz plates to dramatically reduce the cost of nanoscale lithography. This lithography approach, recently added to the ITRS Roadmap, has special advantages for applications in the areas of nanodevices, MEMS, microfluidics, and optical components and devices, as well as molecular electronics. Optical traps: Arryx has developed a breakthrough in nanomaterial manipulation. Optical traps generate hundreds of independently controllable laser tweezers that can manipulate molecular objects in 3-D (move, rotate, cut, place), all from one laser source passing through an adaptive hologram. The applications span from cell sorting, to carbon nanotube placement, to continuous material handling. They can even manipulate the organelles inside an unruptured living cell (and weigh the DNA in the nucleus). Metrology: Imago's LEAP atom probe microscope is being used by the chip and disk drive industries to produce 3-D pictures that depict both the chemistry and the structure of items on an atom-by-atom basis. Unlike traditional microscopes, which zoom in to see an item on a microscopic level, Imago's nanoscope analyzes structures, one atom at a time, and "zooms out" as it digitally reconstructs the item of interest at a rate of millions of atoms per minute. This creates an unprecedented level of visibility and information at the atomic level. Advances in nanoscale tools help us control and analyze matter more precisely, which in turn allows us to produce better tools. To summarize, the top-down path is designed and engineered with the following: Semiconductor industry adjacencies (with the benefits of market extensions and revenue along the way and the limitation of planar manufacturing techniques) Interfaces of scale inherited from the top The Biological, Bottom-Up Path In contrast to the top-down path, the biological bottom-up archetype is Grown via replication, evolution, and self-assembly in a 3-D, fluid medium Constrained at interfaces to the inorganic world Limited by gaps in learning and theory (in systems biology, complexity theory, and the pruning rules of emergence) Bootstrapped by a powerful preexisting hierarchy of interpreters of digital molecular code To elaborate on this last point, a ribosome takes digital instructions in the form of mRNA and manufactures almost everything we care about in our bodies from a sequential concatenation of amino acids into proteins. The ribosome is a wonderful existence proof of the power and robustness of a molecular machine. It is roughly 20nm on a side and consists of only 99,000 atoms. Biological systems are replicating machines that parse molecular code (DNA) and a variety of feedback to grow macroscale beings. These highly evolved systems can be hijacked and reprogrammed to great effect. So how does this help with the development of molecular electronics or nanotech manufacturing? The biological bootstrap provides a more immediate path to nanotech futures. Biology provides us with a library of prebuilt components and subsystems that can be repurposed and reused, and research in various labs is well under way in reengineering the information systems of biology. For example, researchers at NASA's Ames Research Center are taking self-assembling heat shock proteins from thermophiles and genetically modifying them so that they will deposit a regular array of electrodes with a 17nm spacing. This could be useful for making patterned magnetic media in the disk drive industry or electrodes in a polymer solar cell. At MIT, researchers are using accelerated artificial evolution to rapidly breed an Ml3 bacteriophage to infect bacteria in such a way that they bind and organize semiconducting materials with molecular precision. At the Institute for Biological Energy Alternatives (IBEA), Craig Venter and Hamilton Smith are leading the Minimal Genome Project. They take Mycoplasma genitalium from the human urogenital tract and strip out 200 unnecessary genes, thereby creating the simplest organism that can self-replicate. Then they plan to layer new functionality onto this artificial genome, such as the ability to generate hydrogen from water using the sun's energy for photonic hydrolysis. The limiting factor is our understanding of these complex systems, but our pace of learning has been compounding exponentially. We will learn more about genetics and the origins of disease in the next ten years than we have in all of human history. And for the minimal genome microbes, the possibility of understanding the entire proteome and metabolic pathways seems tantalizingly close to achievable. These simpler organisms have a simple "one gene, one protein" mapping and lack the nested loops of feedback that make the human genetic code so rich. An Example: Hybrid Molecular Electronics In the near term, a variety of companies are leveraging the power of organic self-assembly (bottom-up) and the market interface advantages of top-down design. The top-down substrate constrains the domain of self-assembly. Based in Denver, ZettaCore builds molecular memories from energetically elegant molecules that are similar to chlorophyll. ZettaCore's synthetic organic porphyrin molecule self-assembles on exposed silicon. These molecules, called multiporphyrin nanostructures, can be oxidized and reduced (their electrons removed or replaced) in a way that is stable, reproducible, and reversible. In this way, the molecules can be used as a reliable storage medium for electronic devices. Furthermore, the molecules can be engineered to store multiple bits of information and to maintain that information for relatively long periods before needing to be refreshed. Recall the water-drop-to-transistor-count comparison, and add to that the fact that these multiporphyrins have already demonstrated as many as eight stable digital states per molecule. The technology has future potential to scale to 3-D circuits with minimal power dissipation, but initially it will enhance the weakest element of an otherwise standard 2-D memory chip. To end customers, the ZettaCore memory chip looks like a standard memory chip; nobody needs to know that it has "nano inside." The input/output pads, sense amps, row decoders, and wiring interconnect are produced via a standard semiconductor process. As a final manufacturing step, the molecules are splashed on the wafer, where they self-assemble in the predefined regions of exposed metal. From a business perspective, this hybrid product design allows an immediate market entry because the memory chip defines a standard product feature set, and the molecular electronics manufacturing process need not change any of the prior manufacturing steps. Any interdependencies with the standard silicon manufacturing steps are also avoided, thanks to this late coupling; the fab can process wafers as it does now before spin-coating the molecules. In contrast, new materials for gate oxides or metal interconnects can have a number of effects on other processing steps, and these effects need to be tested. That introduces delay (as with copper interconnects). Generalizing from the ZettaCore experience, the early revenue in molecular electronics will likely come from simple 1-D structures such as chemical sensors and self-assembled 2-D arrays on standard substrates, such as memory chips, sensor arrays, displays, CCDs for cameras, and solar cells. IP and Business Model Beyond product development time lines, the path to commercialization is dramatically impacted by the cost and scale of the manufacturing ramp. Partnerships with industry incumbents can be an accelerant or an albatross for market entry. The strength of the IP protection for nanotech relates to the business models that can be safely pursued. For example, if the composition of matter patents afford the nanotech start-up the same degree of protection as for a biotech start-up, then a "biotech licensing model" may be possible in nanotech. A molecular electronics company could partner with a large semiconductor company for manufacturing, sales, and marketing, just as a biotech company partners with a big pharmaceutical partner for clinical trials, marketing, sales, and distribution. In both cases, the cost to the big partner is on the order of $100 million, and the start-up earns a royalty on future product sales. Notice how the transaction costs and viability of this business model option pivot on the strength of IP protection. A software business, on the other end of the IP spectrum, would be very cautious about sharing its source code with Microsoft in the hopes of forming a partnership based on royalties. Manufacturing partnerships are common in the semiconductor industry, with the "fabless" business model. This layering of the value chain separates the formerly integrated functions of product conceptualization, design, manufacturing, testing, and packaging. This has happened in the semiconductor industry because the capital cost of manufacturing is so large. The fabless model is a useful way for a small company with a good idea to bring its own product to market, but the company then must face the issue of gaining access to its market and funding the development of marketing, distribution, and sales. Having looked at the molecular electronics example in some depth, we can now move up the abstraction ladder to aggregates, complex systems, and the potential to advance the capabilities of Moore's Law in software.

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Carbon nanotubes introcution from IBM

Carbon nanotubes
	Here, we focus on our recent work on carbon nanotubes; their structure, properties and uses in nano-electronic devices. Carbon nanotubes are extremely thin (their diameter is about 10,000 times smaller than a human hair), hollow cylinders made of carbon atoms.
	This site consists of the following sections (to access them you may also use the navigation bar on the left): Nanotube manipulation: We can manipulate the nanotube positions, change their shape, cut them and place them on electrodes. Molecular mechanics: We can simulate the mechanical behavior of nanotubes by calculating the forces acting between nanotubes and other objects such as the substrate. Nanotube Field-Effect Transistor: We have successfully used semiconducting single and multi-walled nanotubes as channels of field-effect transistors. Nanotube rings: While normally nanotubes are straight, we have devised ways to prepare them in a ring form. Nanotube theory: Computation and theory of the electrical and mechanical properties.
		Nanotubes, depending on their structure, can be metals or semiconductors. They are also extremely strong materials and have good thermal conductivity. The above characteristics have generated strong interest in their possible use in nano-electronic and nano-mechanical devices. For example, they can be used as nano-wires or as active components in electronic devices such as the field-effect transistor shown in this site.

Introduction to CNT from wikipedia

Carbon nanotubes (CNTs) are allotropes of carbon. A single wall carbon nanotube is a one-atom thick graphene sheet of graphite (called graphene) rolled up into a seamless cylinder with diameter of the order of a nanometer. This results in a nanostructure where the length-to-diameter ratio exceeds 10,000. Such cylindrical carbon molecules have novel properties that make them potentially useful in many applications in nanotechnology, electronics, optics and other fields of materials science. They exhibit extraordinary strength and unique electrical properties, and are efficient conductors of heat. Inorganic nanotubes have also been synthesized.

Nanotubes are members of the fullerene structural family, which also includes buckyballs. Whereas buckyballs are spherical in shape, a nanotube is cylindrical, with at least one end typically capped with a hemisphere of the buckyball structure. Their name is derived from their size, since the diameter of a nanotube is in the order of a few nanometers (approximately 50,000 times smaller than the width of a human hair), while they can be up to several millimeters in length. There are two main types of nanotubes: single-walled nanotubes (SWNTs) and multi-walled nanotubes (MWNTs).

The nature of the bonding of a nanotube is described by applied quantum chemistry, specifically, orbital hybridization. The chemical bonding of nanotubes are composed entirely of sp² bonds, similar to those of graphite. This bonding structure, which is stronger than the sp³ bonds found in diamond, provides the molecules with their unique strength. Nanotubes naturally align themselves into "ropes" held together by Van der Waals forces. Under high pressure, nanotubes can merge together, trading some sp² bonds for sp³ bonds, giving great possibility for producing strong, unlimited-length wires through high-pressure nanotube linking