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Synopsis: Technologies: Nanotechnology: Nanotube:

A three-level framework on the case of nanotubes is presented to analyse and visualise the dynamics in three interrelated context:

the case of nanotubes, Technol. Forecast. Soc. Change 72 (2005) 1094 1111.48 R. O. van Merkerk, D. K. R. Robinson, Characterizing the emergence of a technological field:

and widely accepted as desirable artifacts including high factor sun screens, tennis racquets reinforced with carbon nanotubes,

car body parts incorporating carbon nanotubes, dendrimers and many other artifacts. Regulation, product liability, case law and patent law have existed long

The case of nanotubes Rutger O. van Merkerk T, Harro van Lente 1 Department of Innovation studies, Utrecht University, P o box 80125,3508 TC, Utrecht, The netherlands

and we employ it in our case study. We will show that it is possible to trace emerging irreversibilities for a specific application of nanotubes (Section 3). We will conclude by placing our contribution in a historical perspective of technology assessment

3 The fact that we use the emergence of this specialised journal for this paper is the fact that nanotubes is one of the major topics in this journal.

bresearch contributions on nanoparticles, clusters, nanotubes, nanocrystals, nanolayers, and macromolecules surrounded either by gases, liquids or solids, are brought together in this single publication.

These steps make up the method we employ in this paper to perform the case study. These steps are elaborated on in Section 3. The case we discuss in the next section deals with nonvolatile memories based on nanotubes.

We chose this application of nanotubes in electronic devices because it is as will become apparent a dynamic case among the (still) very few applications of nanotubes in electronic devices that also shows some commercial activity.

How are the technological developments from the scientific viewpoint taken up by society? How are the technological developments from the market viewpoint taken up by society?

nonvolatile memories based on nanotubes Before explaining the details about nonvolatile memories based on nanotubes, we first briefly introduce the area of nanotechnology and nanotubes.

Nanotechnology is a rising star in the set of new and emerging technologies. Many countries and firms feel the need to explore

In this paper we focus on a special kind of nanosized particle, the carbon nanotubes, which has the same basic structure as the bucky ball.

The term nanotube is used generally to refer to the carbon nanotube, which can be visualised as a sheet of chicken wire,

The promising developments of nanotubes, and nanotechnology in general, have led, at least according to some analysts, to a nanotechnology hype 13.

Typical examples are very small robots that can conduct operations inside the human body or an elevator into space based on a nanotube cable.

the nanotubes are formed directly. R. O. van Merkerk, H. van Lente/Technological forecasting & Social Change 72 (2005) 1094 1111 1099 other hand there are growing concerns about the development

After this general introduction of nanotechnology and nanotubes, we now turn to the application that will be the subject for the remainder of the paper.

A promising application of nanotubes is to use them as electromechanical8 components in nonvolatile memories. 9 Nonvolatile means that the data remains intact

In the boffq state (Fig. 6), the nanotubes have a certain distance between them. The lower nanotube is semiconducting,

the upper nanotube is metallic. 10 The metallic nanotube will bend towards the perpendicular semiconducting nanotube

when both are charged electrically (electromechanical process). The nanotubes will then stay in this position due to the Van der waals forces. 11 These forces cause the nanotubes to remain their position,

even when the power is turned off, giving the memory its nonvolatile character. The positions can be determined by measuring the resistance (directly related to the flow of electrons) between the nanotubes.

In the bonq state the resistance is much lower, which allows determination between zero or one.

and patented by Fig. 4. A rolled up single sheet of carbon atoms (graphene) to visualise a single-walled carbon nanotube. 8 Electromechanical means that an electrical current can induce mechanical movement. 9 Memory,

Nanotubes can have both properties which depend on the geometry of the single-walled carbon nanotube 17.11 The Van derwaals forces are the physical forces of attraction

and repulsion existing between molecules, which are responsible for the cohesion of molecular crystals and liquids.

In the hybrid solution the lower nanotube is replaced by a semiconducting structure created by common lithography techniques. 12 Then a layer of nanotubes is deposited

and the unwanted nanotubes are etched away (again with common lithography). G. Schmergel, T. Rueckes and B. M. Segal founded Nantero in 2000 (Rueckes being one of the inventors of the proof of principle.

Nantero is developing NRAMK a high-density nonvolatile random access memory chip using nanotube technology. The company expects to deliver a product that will replace existing forms of memory, such as DRAM, SRAM and flash memory, with a high-density nonvolatile duniversal memoryt 18.

The company plays an important role in the development of nonvolatile memories based on nanotubes. 3. 1. Tracing dynamics of expectations The three levels in the framework can be specified in relation to the case.

nanotubes used in nonvolatile memories, the level of the technological field; nanotubes in electronic devices, the level of the society;

and nanotubes as part of nanotechnology. Such a case specific typology gives a focus for each level

and is therefore useful to distinguish what the boundaries are of the case. 3. 1. 1. Society The scientific developments,

and understanding of nanotubes production and characteristics13 have led to expectations on the level of the society.

A spokesperson in favour of nanotube developments is Richard Smalley (Rice university, Houston, Texas). Considering the following statements from Smalley 21, page 1:

Q With this statement Smalley stipulates (from a scientific point of view) a very bright picture for nanotubes.

Fig. 5. Architecture of suspended nanotube memory 16.12 Lithography is a common method used in the computer chip manufacturing industry to produce desired structures in materials. 13 The research agenda on nanotubes have,

controlled growth and applications of nanotubes. This also implicates that the variety of research topics has broadened.

, production capacity of single-walled carbon nanotubes) to applications and the production of the applications.

bcarbon nanotubes are already found in cars and some tennis rackets, but there is virtually no environmental or toxicological data on them.

which includes nanotubes) and launch a transparent global process for evaluating the socioeconnomic health and environmental implications of the technology.

From the market side the expectations focus on the possibilities that nanotubes might have to improve or revolutionise existing products.

Already nanotubes are used to strengthen materials (e g.,, tyres or tennis rackets) and production facilities are set up to deliver the demand for nanotubes (MWNT

and SWNT) that is expected for the coming years. Arnall 13, page 14 states here (taking a market perspective:

Q Such statements give rise to the belief that nanotubes have much to offer in terms of applications.

when we look at how broad the application areas for nanotubes are addressed generally: pharmaceuticals, electronic devices, material production, energy technologies, etc.

Concluding, the expectations on the societal level show a contradiction in the sense that on the one hand nanotubes are used without regulation

However, the fact that nanotubes offer great promises for various industries is acknowledged. 3. 1. 2. Technological field After the discovery of the single-walled nanotube in 1993,

possible applications of nanotubes for electronic devices came out of the scientific community 21. Using the straight tubes as wires in chips was one of the first options.

Cees Dekker's group 31 at the Delft University of Technology (Netherlands) turned a nanotube into a transistor (the basic building block of computer chips.

This made it theoretically possible to build processors (the central computational unit of personal computers) out of nanotubes.

Nanotubes can also be used to emit electrons. This opens up the possibility to use them as so-called field emitters to produce flat (even flexible) displays.

The electrons emitted by the nanotube are pointed at a layer of phosphor, which as a consequence lights up.

Since the publication of Rueckes et al. 16, where they introduce the architecture of nonvolatile memory based on nanotubes,

it is clear that building these memories is one of the possible applications of nanotubes in electronic devices.

when the opportunities for nanotubes in electronic devices are discussed: bbig markets, apart from materials, in which nanotubes may make an impact,

include flat panel displays (near-term commercialisation is promised here), lighting, fuel cells and electronics. This last is one of the most talked-about areas but one of the farthest from commercialisation, with one exception,

Nanotechnology should give the answers here. 3. 1. 3. Research group The expectations of using nanotubes for nonvolatile memories started with the Nature publication of Charles Lieber's group 16.

In 2002, James Heath's group at the University of California (Los angeles) reported that guiding the growth with an electric field could solve the problem of growing straight nanotubes 25.

This scientific result solved the problem of growing straight nanotubes. Deposition of nanotubes into a parallel array (as is needed to create the hybrid solution) can be done in multiple ways.

One can individually manipulate the nanotubes into the right position however due to huge amount of nanotubes that needs positioning, this is no option.

The second option is to use an electric field to grow the (straight) nanotubes onto the substrate 25 (as discussed above.

A third way is to use a flow to guide the previous made straight nanotubes into position.

Charles Lieber's group 14 Cientifica is the business information and consulting arm of CMP Cientifica, providing global nanotechnology business intelligence and consulting services to industry and investors worldwide.

R. O. van Merkerk, H. van Lente/Technological forecasting & Social Change 72 (2005) 1094 1111 1103 reported the latter method in 2001 26.

These scientific results solved the problem of deposition of the nanotubes onto a substrate. The scientific results,

bthis proof of principle raises hopes that a nanotube lattice could form computer memory, storing one bit of information at each junction.

Here, Nantero being the only company working on this technique tries to mature the given technique (proof of principle) into a usable method for producing nonvolatile memories based on nanotubes.

bcreating this enormous array of suspended nanotubes using standard semiconductor processes brings us much closer to our end goal of mass producing NRAM chips.

buniversal memory has been a dream for the semiconductor industry for decades we fell that Nantero's innovative approach using carbon nanotubes

bthe proprietary manufacturing approach will enable for the first time the ultra-large scale integration (ULSI) of carbon nanotube-based devices in a deep sub-micron semiconductor fabrication line.

Concluding, different developments in basic research have given the building blocks that can be used to develop nonvolatile memories based on nanotubes.

Nanotubes) taken up by policy makers and translated into programmes/regulation that reply to these concerns? Some initiatives have started over the last few years;

when nanotubes are grown, it is until now impossible to determine the electronic character (metallic or semiconductor) beforehand.

Therefore, after growing, you end up with a mixture of metallic and semiconductor nanotubes. This is a problem,

because often you need specific characteristics of the nanotubes in order to get a working application. To specify this example further,

Cees Dekker's group at Delft University, showed in 1998 31 that a single semiconductor nanotube could be turned into a transistor.

Without the ability to grow nanotubes with the right characteristics beforehand a processor based on nanotube transistors is impossible to produce. 3. 2. 3. Research group Restrictive factors in the development of technologies are repeating phenomena that end up on the agenda of research groups.

Scientists observe hurdles for further development of a promising application (guided by the expectations) and start to work on solving the problems at R. O. van Merkerk, H. van Lente/Technological forecasting & Social Change 72 (2005) 1094 1111 1105 hand.

or are still the growth of straight nanotubes, precise deposition of the nanotubes on the substrate,

and the separation of metallic and semiconductor nanotubes. Because not all problems were solved over the last years,

Nantero adapted a (proprietary) hybrid solution that allows for some errors, and metallic and semiconductor nanotubes do need not to be separated.

So, over the last few years some problems were solved and others were overcome by adapting the design.

Q At the same time, basic research groups work on fundamental insights in for example, controlled growth of metallic or semiconductor arrays of nanotubes.

in the matrix in Fig. 7. These findings also give answers to the questions as proposed in Fig. 2. Nanotubes as part of nanotechnology Next to the acknowledgement that nanotubes offer huge possibilities,

there is an open discussion on the possible toxic effects of nanoparticles (incl. nanotubes) on the environment and inside the human body.

Nanotubes as part of nanotechnology Apart from the concerns on the possible toxicity, industry started to produce nanoparticles with a strong growing increase in capacity.

The market then focuses on the possibilities nanotube applications promise to improve or revolutionise existing products.

Nanotubes in electronic devices The market focuses on a selection of promising electronic applications based on nanotubes.

Nanotubes used in nonvolatile memories Nantero tries to mature the technique (proof of concept) into a usable method for producing nonvolatile memories based on nanotubes.

Nanotubes used in nonvolatile memories Step by step the problems around producing predetermined nanotubes and applying them for nonvolatile memories are solved (straight growth and deposition).

Nanotubes in electronic devices The academic community addresses a wide variety of electronic devices based on nanotubes. These options are based on advances in the understanding of

and the control to determine (beforehand) the characteristics of nanotubes. However, existing hurdles also restrain further developments.

that arose around nanotubes and more specifically nanotubes in electronic devices, and nonvolatile memories based on nanotubes (Fig. 8). We have shown that results of research groups directly give rise to expectations for promising applications and change the agendas for the future.

Accumulation of research results (for instance, straight growth and precise deposition of nanotubes) solves the hurdles that before hindered promising applications to become reality.

In the specific application we discussed in this paper this led (on the market side) to the realisation of a prototype of nonvolatile memories of Nantero.

The scientific community (related to the application of nanotubes in electronic devices) changed in the sense that since 1993 more and more attention was drawn to nanotubes.

This indicates a growing attention for various aspects related to nanotubes as part of nanotechnology. This at the societal level held discourse is marked as an emerging irreversibility.

Nanotubes as part of nanotechnology Societal discourse on nanotubes Nanotubes as part of nanotechnology Societal discourse on nanotubes Nanotubes in electronic devices Recognition of a specific set of promising applications Nanotubes

used in nonvolatile memories Nantero as a surviving central player in realising nanotube applications in nonvolatile memories Nanotubes used in nonvolatile memories Possibilities where opened up by scientific research results that took away hurdles in using nanotubes for electronic devices

Nanotubes in electronic devices More research groups work on similar problems related to nanotube applications Society Technological field (Research group Basic research Market Fig. 8. Emerging irreversibilities located within the three-level framework.

Lieber, Carbon nanotube-based nonvolatile random access memory for molecular computing, Science 289 (2000) 94 97.17 T. W. Odom, J.-l. Huang, P

. Kim, C. M. Lieber, Atomic structure and electronic properties of single-walled nanotubes, Nature 391 (1998) 62 64.18 Nantero, Nantero, Inc. announces collaboration

with ASML compatibility of nanotube processes with ASML equipment proven. Nantero Press release (September 2003. 19 Nantero, Nantero, Inc. announces $6mm in funding aims to rapidly develop nanotube-based universal memory.

Nantero Press release (October 2001. 20 Nantero, Nantero, Inc. announces $10. 5mm in funding developing nanotube-based nonvolatile RAM technology for licensing.

Nantero Press release (September 2003. 21 P. Ball, Roll up for the revolution, Nature 414 (2001)( November.

23 P. G. Collins, P. Avouris, Nanotubes for electronics, Scientific American 283 (6)( 2000 (December)) 62 69.24 Cientifica:

25 M. R. Diehl, S n. Yaliraki, R. A. Beckman, M. Barahona, J. R. Heath, Self-assembled, deterministic carbon nanotube wiring

28 Nantero, Nantero, Inc. creates an array of ten billion nanotubes bits on single wafer standard semiconductor processes used.

transistor based on a single carbon nanotube, Nature 393 (1998) 49 52.32 A. Rip, T. J. Misa, T. J.,J. Schot, Managing Technology

The case of nanotubes. Technological forecasting & Social Change 72, no. 9: 1094 112. O'Regan, B,

including fullerenes, synthetic supramolecular systems, nanotubes, and nanobiology. These reports provided information on the technology field

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