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May 27, 2002
Volume 80, Number 21
CENEAR 80 21 p. 17
ISSN 0009-2347


Similarities in seminal molecular electronics papers raise suspicions

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Claims made in a series of high-profile papers appear to be based on data of questionable validity, say scientists in the U.S. Their suspicions--if proved correct--could set back the field of nanoelectronics significantly.

In question are several key figures published in Science, Nature, and Applied Physics Letters over the past few years by Jan Hendrik Schön and coworkers at Lucent Technology's Bell Labs. In all cases, Schön--who did not respond directly to C&EN's request for comment--is the corresponding author. The data, which were widely reported in the press, show the performance characteristics of electronic devices made from field effect transistors (FETs) based on organic materials.

The data plots appear to show identical noise levels--blip for blip--in studies of related but nonidentical systems. The suspicious pattern was flagged by Harvard chemistry professor Charles M. Lieber and physics professors Lydia Sohn of Princeton, Paul L. McEuen of Cornell, and others, who notified the relevant journals and Bell Labs management of the similarities.

Nanoelectronics researchers have found themselves increasingly puzzled by some findings initially felt to be "beautiful and remarkable," Lieber notes. For example, identical-looking background signals are shown for electronic devices based on single-crystal pentacene FETs [Science, 287, 1022 (2000)] and for two FET devices fabricated from distinct types of self-assembled monolayer FETs [Nature, 413, 713 (2001) and Science, 294, 2138 (2001)].

It is difficult to understand, Lieber says, why noise levels are identical at different temperatures and for devices based on a single layer of molecules and one made from an organic crystal.

Likewise, suspicions have been raised over identical-looking data curves, shown right, published for circuits made from p-type (positive-charge-carrying) perylene FETs [Appl. Phys. Lett., 77, 3776 (2000)] and negative-type a-sexithiophene FETs [Science, 290, 963 (2000)].

"We are quite concerned and want to get the facts on the table," says Cherry Murray, vice president of physical sciences research at Bell Labs. Upon learning of the issue, Murray notes, Bell Labs responded immediately by establishing an external scientific review panel. The panel, chaired by Stanford University physics professor Malcolm Beasley, convened its first meeting on May 17.

"It's a blue-ribbon panel," Murray says, "and we are very encouraged that they will conduct a fair, objective, and thorough independent scientific review."

Sohn remarks that "we need to wait for the committee to sift through all the data and report its findings." The panel does not expect to produce a report until September.

STRIKING RESEMBLANCE Close inspection reveals that signal shapes and noise levels observed in performance measurements of a device made from negative-charge-carrying a-sexithiophene FETs (bottom) look remarkably similar to a positive-type perylene system.


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Copyright © 2002 American Chemical Society

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