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Published June 1, 2008 | public
Journal Article Open

An optical NMR spectrometer for Larmor-beat detection and high-resolution POWER NMR


Optical nuclear magnetic resonance (ONMR) is a powerful probe of electronic properties in III-V semiconductors. Larmor-beat detection (LBD) is a sensitivity optimized, time-domain NMR version of optical detection based on the Hanle effect. Combining LBD ONMR with the line-narrowing method of POWER (perturbations observed with enhanced resolution) NMR further enables atomically detailed views of local electronic features in III-Vs. POWER NMR spectra display the distribution of resonance shifts or line splittings introduced by a perturbation, such as optical excitation or application of an electric field, that is synchronized with a NMR multiple-pulse time-suspension sequence. Meanwhile, ONMR provides the requisite sensitivity and spatial selectivity to isolate local signals within macroscopic samples. Optical NMR, LBD, and the POWER method each introduce unique demands on instrumentation. Here, we detail the design and implementation of our system, including cryogenic, optical, and radio-frequency components. The result is a flexible, low-cost system with important applications in semiconductor electronics and spin physics. We also demonstrate the performance of our systems with high-resolution ONMR spectra of an epitaxial AlGaAs/GaAs heterojunction. NMR linewidths down to 4.1 Hz full width at half maximum were obtained, a 10^3-fold resolution enhancement relative any previous optically detected NMR experiment.

Additional Information

©2008 American Institute of Physics. Received 22 March 2008; accepted 3 May 2008; published 11 June 2008. We thank A. Ksendov, J. Liu, and F. Grunthaner of the NASA Jet Propulsion Laboratory Center for Space Microelectronics for providing the sample and preliminary PL characterization, and L. Burnett and A. Perry for cryogenics advice. This work was supported by the NSF Program in Materials Synthesis and Processing (Grant No. CHE-9612226) and by NASA through the Caltech President's Fund.


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