NSF Org:	DMR Division Of Materials Research
Recipient:	PRESIDENT AND FELLOWS OF HARVARD COLLEGE
Initial Amendment Date:	June 19, 1997
Latest Amendment Date:	July 26, 2000
Award Number:	9701487
Award Instrument:	Continuing Grant
Program Manager:	H. Hollis Wickman DMR  Division Of Materials Research MPS  Directorate for Mathematical and Physical Sciences
Start Date:	July 1, 1997
End Date:	December 31, 2000 (Estimated)
Total Intended Award Amount:	$543,000.00
Total Awarded Amount to Date:	$543,000.00
Funds Obligated to Date:	FY 1997 = $193,000.00 FY 1998 = $175,000.00 FY 1999 = $175,000.00
History of Investigator:	Michael Tinkham (Principal Investigator) tinkham@rsj.harvard.edu
Recipient Sponsored Research Office:	Harvard University 1033 MASSACHUSETTS AVE STE 3 CAMBRIDGE MA  US  02138-5366 (617)495-5501
Sponsor Congressional District:	05
Primary Place of Performance:	Harvard University 1033 MASSACHUSETTS AVE STE 3 CAMBRIDGE MA  US  02138-5366
Primary Place of Performance Congressional District:	05
Unique Entity Identifier (UEI):	LN53LCFJFL45
Parent UEI:
NSF Program(s):	CONDENSED MATTER PHYSICS
Primary Program Source:	app-0197  app-0198  app-0199
Program Reference Code(s):	9161, AMPP
Program Element Code(s):	171000
Award Agency Code:	4900
Fund Agency Code:	4900
Assistance Listing Number(s):	47.049

ABSTRACT

w:\awards\awards96\num.doc 9701487 Tinkham Experimental and theoretical work will be performed to elucidate the physical properties of superconducting and normal-metal devices fabricated on micron and nanometer length scales. In such mesoscopic structures, the Coulomb charging energy of a single electron exceeds thermal energies below 1K, allowing one to control the number of electrons one-by-one on the island in a single-electron transistor (SET). If the island is superconducting, the PI's previous work has shown that the pairing energy leads to even-odd electron number effects. One ongoing project will utilize this even-odd effect as the basis for developing a microwave detector device of unprecedented sensitivity, in which each individual microwave photon absorbed in enabling the photon-assisted tunneling of a single electron will trigger a microsecond long current pulse containing hundreds of electrons. The SET electrometers coupled to wide-band cryogenic amplifiers developed for this experiment will also make possible new types of experiments monitoring the motion of single electronic charges with microsecond time resolution. If the mesoscopic island is as small as 5nm, the PI's previous work has shown that individual electronic energy levels can be resolved, and that a spectroscopic even-odd effect exists even in the normal state because of the two-fold spin degeneracy. Such measurements will be extended to new types of mesoscopic systems such as chemically prepared metallic nanospheres of controlled size (which should allow more systematic probing of energy level statistics than is possible with random sized grains), carbon nanotubes, and possibly even individual large organic molecules. Another experiment in preparation seeks to observe the change in the spectrum of a superconducting nanograin when it is doped with 0,1,2 or more magnetic impurities, to compare with theoretical predictions. %%% There is a practical need to understand better the new basic physics which will govern attempts to devise ever more compact computers and memories. With this general motivation, the research which will be performed under this grant will focus on various forms of the single-electron transistor, or SET. An SET device consists of a small conducting island coupled to electrical leads by ultramall tunnel junctions and capacitively coupled to a gate electrode which controls the number of electrons on the island. Such SET devices can easily detect a single excess electron charge, in principle making possible an ultracompact memory element in which the binary "zero" and "one" are represented by the presence or absence of a single extra electron. Development of a technology from this concept is complicated by the sensitivity of the devices to background charge noise and the difficulty of reliable fabrication of such small devices. The proposed research may lead to progress in overcoming these difficulties. A possible approach which will be explored involves joining the fabrication technology of physics, for making connections, with the molecular engineering of organic chemistry, to make small charge storage elements. At such small length scales, classical physics must be replaced by quantum physics, in which the wave properties of electrons become important in understanding the electrical properties of the device. The research to be performed will probe the relation between the discrete set of quantum energy levels in a small conducing grain with the charging energies of classical electrostatics. Special attention will be paid to phenomena which arise from the pairing energy of electrons if the grain is superconducting, and to the coupling of the electron spins with d eliberately introduced magnetic impurity atoms. ***

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