by Alan L. Porter and Scott Cunningham[1]
Examination of activity patterns in the literature ("bibliometrics") provides a useful set of indicators of the development of a field. We share with you some interesting indicators that suggest that nanotechnology is emerging -- rapidly; in multifaceted ways; and with a diverse cast of participants.
We draw on analyses of two major databases -- INSPEC and SCI -- the Science Citation Index.[2] Preliminary scans of two other electronic databases found very few U.S. Patents explicitly mentioning nanotechnology and roughly 10 percent as many abstracts in Engineering Index as in INSPEC.
Searches in INSPEC
We began in INSPEC with a broadly cast search. This identified several thousand "nano-related" items. At that point, Chris Peterson began to help us separate out the research more closely akin to "bottom-up" nanotechnology. Several iterations convinced us that this is a tough task! The result is a report distinguishing four levels of activity:
A. "Nano-related" -- the most encompassing scan[3]
B. "Nanotechnology" -- items explicitly including the term
C. "Scanning probe Nanotechnology" -- items mentioning STM or AFM and nano[4]
D. "Bottom-up" -- the most restrictive search seeking bottom-up nanotechnology research.[5]
Table 1 profiles nanotechnology-related activity in INSPEC. Table 1-A offers an INSPEC activity tally for the four levels. Column A, Nano-related, shows that interest in various facets of nanotechnology is booming (so much so that we limit further "nano-related" tabulations to the 1896 abstracts appearing in 1993 and 1994. This also shows how "hot" nano is -- the literature is burgeoning. In contrast, Column D, Bottom-up Nano, is much more limited.
Table 1-B shows which countries are leading contributors to the nano literature. Note that the USA and Japan are #1 and #2 from Bottom-up to the most encompassing "nano-related" searches. For "bottom-up," the total number is so small that one should not put much stock in the implications. For interest, Yugoslavia ranks #3 with 4 abstracts. We found it particularly interesting to see how active China is in general nano-related research.
At one step finer (not shown in Table 1), one can profile publication activity by state. For "scanning probe nano" research (C), New York yields the most abstracts (8), followed by Illinois (5) and Arizona (4), with California trailing (2) . In the other three tabulations, California leads. For "nano-related" (A), California shows 83 items, followed by New York (57) and Illinois (42), with 6 other states publishing 22 or more. For "nanotechnology" (B), California (40) is followed by New York (24) and Texas (16). For "bottom-up nano," California shows 9 with no others publishing more than 2.
Table 1-C lists "Top 10" institutional contributors to this literature for (A) " nano-related" and (B) "nanotechnology." Items with affiliations linked to a given company (e.g., NEC) from all sites (various countries) are consolidated here. Nano-related work is coming mostly from universities, followed by research labs, and several notable industrial firms. Again, the prominence of certain Chinese groups is notable. Note how different list (B) is -- testimony to the fact that "nano" covers a considerable range of research activities that are relatively distinct from each other. The UK strength in B is notable. Activity in C and D is more limited and widely dispersed. For D, "bottom-up nano," the only institutions linked to more than a single item are:
* Bodenkultur Univ, Austria (3)
* Belgrade Univ, Yugoslavia (3)
* Utah Univ, USA (2)
* Caltech, USA (2)
* Matsushita, Japan (2)
* Xerox PARC (2 -- or 4 if one combines with the Inst. for Molecular Manuf . and the Foresight Inst.).
Table 1-D profiles the keywords (subject index terms) most frequently given in these items. Such profiles suggest the relationship of methods and substantive areas of inquiry. In the interest of space and sanity, Table 1-D provides a simple cut at this based on "Top 10" keyword cumulations for each of the four levels , also showing how the other nano levels relate to each cumulation.
The first Top 10 is for "nanotechnology." Excepting the term "nanotechnology," excluded from the Top 10 because it was an explicit search term, note that these are the top 10 in Column B. Note that the emphasis is overwhelmingly on semiconductors, with prominence to STM and AFM, presumably as observational tools. Mo ving down Column B, note that the 584 "nanotechnology" items do touch lightly into other domains.
The second Top 10 is for the "nano-related" search, of which 8 appear here with two in the previous list (silicon and elemental semiconductors). We interpret this broad "nano-related" search to show strongest interest in materials science with significant reach into semiconductors and relatively little in general chemical and biological domains.
The third Top 10 is for "scanning-probe nano"; 4 of this Top 10 appear in the "n anotechnology" (B) Top 10 too. Scanning-probe-based nanotechnology taps into surface and biological domains in addition to semiconductor issues; it seems to skirt the materials issues of (A).
Recognizing the relatively small sample, the "bottom-up nano" profile is still striking in the extent to which it differs from the others. Table 1-D gives its Top 10 -- distinctly biologically oriented.
Searches in SCI
The following counts are based on a search in the Science Citation Index, years 1986 - 1995. It duplicates the INSPEC search (Table 1-A).[6]
Nano-Related: 912
Nanotechnology: 82
Scanning Probe Nano: 150
Bottom-Up Nano: 32
The Science Citation Index shows considerably less technology or applied
science content than does INSPEC. Where the INSPEC search emphasizes
semiconductors, lithography, and materials science, SCI has relatively greater coverage
in
areas of basic research such as microscopy, biophysics, films, and surface sciences. SCI
also is known to have a strong emphasis on the life sciences, and therefore more strongly
highlights "bottom-up nanotechnology," as it relates to organic chemistry, biochemistry and
clinical chemistry.
In addition, while there is considerable content in INSPEC using the term
"nanotechnology," in SCI, nanotechnology is a relatively infrequent term (82 occurrences in 10 years). More common usages found in SCI that seem to relate to nanotechnology include:
SELF-ASSEMBLY 514NANOCRYSTAL(s) and NANOCRYSTALLINE 1127
NANOSTRUCTURE(s) 613
NANOSIZE$ and NANOSCALE$ 488
NANOPARTICLE(s) 392
SUPRAMOLECULAR and (CHEMISTRY, ASSEMBL$, SYSTEM(s),STRUCTURE(s) 350
NANOTUBE(s) or NANOTUBULE(s) 205
In particular, "self-assembly" appears to be a rich area of research with strong kinship to nanotechnology.
SCI offers a unique capability to track citation patterns. That is, this database tabulates references between articles. Impressively, 246 articles in SCI cite Drexler and his works on nanotechnology. This number is increasing over time: about 10 citations per year for 1987-89, about 20 per year for 1990 -92, 49 in 1993, and 88 in 1994. The top journals in which Drexler is cited are:
1. Journal of Molecular Biology
2. Journal of the American Chemical Society
3. Science
4. Journal of the Minerals, Metals & Materials Society
5. Proceedings of the National Academy of Science (USA)
The articles citing Drexler appear in diverse journals, led by the following gro upings:
* biochemistry, organic chemistry, and genetic engineering - accounting for about 42% of the citations to Drexler;
* general interest scientific journals (such as Science and Nature, which are typically considered to be interdisciplinary in content) - 19% ;
* chemical journals of broad coverage - 13%.
Areas of solid-state physics, computers and engineering, together, follow in their citation of Drexler's works (17% of his citations).
It is interesting to note that of those articles that cite Drexler, a substantial number (44) also cite J. M. Lehn, a prolific and Nobel-Prize winning scientist . Over the past decade Lehn has written at least 187 articles indexed in SCI . These articles are in the areas of supramolecular chemistry, the directed self-assembly of molecules, and molecular devices. The single most frequently co-cited paper with Drexler is:
Lehn, J. M. (1988), "Supramolecular Chemistry- Scope and Perspectives:
Molecules, Supermolecules, and Molecular Devices," Angewandte Chemie -
International Edition in English, Vol. 27, p. 89-112.
Other frequently co-cited authors with Drexler include I. Riede, D. J. Cram, B. Dietrich, and P. R. Ashton. All five of these authors publish heavily in Angewandte Chemie, which is notable for its absence of citations to Drexler.
In conclusion, by comparing the nanotechnology content of INSPEC and the Science Citation Index, we see evidence of divergent development. The results suggest substantial and growing differences among researchers interested in the "nanosciences." In SCI nanotechnology coverage is less applied and more oriented towards basic research, so much so that the word "nanotechnology" itself is only infrequently used. Secondly, in SCI, nanotechnology research relates much more closely to the life sciences and most particularly to bio - and organic chemistry. "Bottom-up nanotechnology" items in INSPEC share this orientation. Thirdly, there is evidence that different indexing terms are being developed in the basic and life sciences to refer to items of research that are nonetheless nanotechnology-related. Fourthly, distinct citation patterns are emerging where Drexler's "big picture" of nanotechnology development is being worked by authors performing significant and detailed work in the emerging problems of a new discipline. Distinctive terminology is emerging for various forms of nanotechnology research. Indeed, it appears that "nanotechnology" research is maturing, as indicated by the appearance of divergent research areas.
Table 1. Nanotechnology in the INSPEC Database
A B C D
Nano-related Nanotechnology Scanning probe Nano Bottom-up Nano
A. Abstracts 3208[7] 584 122 42
B. Countries[8] [rank - %] [rank - %] [rank - %] [rank -
%]
USA 1 - 30.8 1 - 33.7 1 - 28.7 1 - 48.6
Japan 2 - 14.5 2 - 23.1 2 - 23.5 2 - 14.3
UK 6 - 5.0 3 - 14.7 4 - 10.4 4 - 8.6
Germany 3 - 9.9 4 - 10.1 3 - 11.3 7 - 2.9
Switzerland 9 - 2.4 5 - 3.2 7.5 - 4.3 - - 0.0
France 5 - 5.4 6 - 3.0 5.5 - 5.2 - - 0.0
Russia 7 - 3.1 7 - 2.0 7.5 - 4.3 6 - 5.7
China 4 - 8.7 8 - 1.3 5.5 - 5.2 - - 0.0
Italy 8 - 2.4 9.5 - 1.1 9.5 - 1.7 - - 0.0
Austria 24 - 0.5 9.5 - 1.1 - - 0.0 5 - 8.6
C. Institutional Affiliation[9]
A Nano-related [rank - #]
Chinese Acad of Sci, Shenyang, China 1 - 41
IBM 2 - 36
Naval Research Labs, USA 3 - 30
Tohoku Univ, Jpn 4 - 29
Hitachi, Jpn 5 - 24
MIT, USA 6 - 24
Max Planck Inst, Stuttgart, Ger 7 - 23
Tokyo Univ, Jpn 8 - 22
Chinese Acad of Sci, Hefei 9 - 20
Illinois Univ, USA 10 - 19
B. Nanotechnology [rank - #]
IBM 1 - 19
Warwick Univ, UK 2 - 15
Cambridge Univ, UK 4 - 12
Aberdeen Univ, UK 4 - 12
Hitachi, Jpn 4 - 12
Glasgow Univ, UK 7 - 10
Cornell Univ, USA 7 - 10
NEC, Jpn 7 - 10
College of Tech, Ibaraki, Jpn 9.5 - 9
NIST, USA 9.5 - 9
D.Related Keywords[10]
A B C D
Nano-related Nanotechnology Scanning probe Nano Bottom-up Nano
B - "Nanotechnology Top 10"
STM 6.4 19.3 77.0 7.1
Electron beam lithography 4.4 18.2 9.8 0
Silicon 10.9 12.0 10.7 0
AFM 4.1 11.8 30.3 9.5
Integrated circuit technology 2.3 11.5 5.7 0
Sputter etching 3.1 11.0 4.9 0
III-V semiconductors 5.4 10.8 3.3 0
Elemental semiconductors 11.3 10.4 10.7 0
Gallium arsenide 4.5 9.1 3.3 0
Semiconductor technology 1.9 8.6 6.6 0
A - "Nano-related Top 10"
Nanotechnology 16.4 77.6 79.5 14.3
Transmission electron microscope 13.9 2.2 0 0
Iron alloys 11.4 0.2 0 0
X-ray diffraction 11.3 0 0 0
Grain size 9.6 0.2 0 0
Annealing 9.0 1.2 0.8 0
Luminescence of inorganic solids 8.1 3.3 1.6 0
Boron alloys 7.8 0 0 0
C - "Scanning probe Nano Top 10"
Surface structure 3.5 3.6 13.1 0
Organic compounds 0.6 1.7 12.3 2.4
Molecular biophysics 0.3 2.4 8.2 35.7
Etching 2.7 8.2 8.2 0
Langmuir-Blodgett films 0.9 1.2 8.2 0
D - "Bottom-up Nano Top 10"
Proteins 0.1 1.5 1.6 28.6
Biomolecular electronics 0.3 1.9 1.6 23.8
Micromechanical devices 1.2 5.7 4.1 14.3
Biological techniques & instruments 0.3 1.7 3.3 11.9
Macromolecular configurations 0.1 0.9 4.9 9.5
Cellular biophysics 0.05 0.3 0.8 9.5
Cellular transport & dynamics 0 0 0 9.5
Molecular electronics 0.3 2.9 7.4 9.5
[2] INSPEC is produced by the Institution of Electrical Engineers (IEE). It corresponds to the three Science Abstracts print publications: Physics Abstracts, Electrical and Electronics Abstracts, and Computer and Control Abstracts. As of January, 1995, INSPEC contains 1.98 million abstracts on line, dating from 1986. About 84 percent of the source publications are in English. SCI is produced by the Institute for Scientific Information.
[3] Boolean searches were performed in INSPEC. Search abbreviations include: "adj" - adjacent to; "and" - both terms occur; "or" - either term occurs; "near#" - terms appear within # words of each other; "with" - terms both appear in the same field (e.g., abstract); "not" - the indicated terms does not appear; "(s)" - singular or plural; $ - truncation (any extensions). Search includes items for which the following terms appear (in keywords, abstract, etc., not just in titles): (atomic adj scale) near1 structure(s); (molecular adj control) near1 structure(s); nanoelec$; nanoma$; nanotechn$; nanoproc$; nanoprob$; nanofab$; or nanostructur$.
[4] Search includes: [(scanning adj (tunnelling or tunneling)) or ((atomic adj force) with (microscope(s) or microscopy or spectroscopy))] and [nanotechnology or (molecular adj electronics) or (molecular adj (modeling or m odelling or simulation)).
[5] Search consists of: (molecular or computational) adj nanotechnology; or molecular adj (machine(s) or manufacturing). We attempted various other searches without notable success -- e.g., linking construction or device with STM/AFM generated items primarily about device construction; linking deposition with STM/AFM got predominantly to items that entailed both deposition (e.g. , chemical vapor) and observation (e.g., STM), but rarely STM usage for deposition of molecules.
[6] Searching by abstract and content fields is limited in this database from the years 1991 to the present. Searches from the years 1986 - 1990 are therefore based on titles only.
[7] "Nano-related" tabulations in Parts 1-B to 1-D are based on only the 1896 abstracts published in 1993 and 1994.
[8] Countries are the "Top 10" in order of "Nanotechnology" (C olumn B) frequency. "%" is based on total abstracts for which a country of author origin is identifiable.
[9] The "Nano-related" "Top 10" reflect only 1993 and 1994 abstracts out of 1896 (66 with no affiliation noted). The "Nanotechnology" "Top 10 " are based on 584 abstracts (46 with no affiliation noted).
[10] Shown are a compilation of the most frequent keywords. The compilation is clustered into "Top 10" lists from each of the levels, excluding the search terms used to construct that level and not repeating terms appearing in the other clusters. Values are the % of the items in which this explicit keyword appears; for "Nano-related," the tabulation is limited to the 1896 abstracts for 1993 and 1994. These terms are standardized in this database. So, for instance, many related terms could be noted -- "semiconductor technology" is included, but "semiconductor materials" or "semiconductor growth" are not.