Extension of nuclear magnetic resonance (NMR) to nanoscale samples has been a longstanding challenge because of the insensitivity of conventional detection methods. We demonstrated the use of an ...individual, near-surface nitrogen-vacancy (NV) center in diamond as a sensor to detect proton NMR in an organic sample located external to the diamond. Using a combination of electron spin echoes and proton spin manipulation, we showed that the NV center senses the nanotesla field fluctuations from the protons, enabling both time-domain and spectroscopic NMR measurements on the nanometer scale.
Nanoscale magnetic resonance imaging Degen, C.L; Poggio, M; Mamin, H.J ...
Proceedings of the National Academy of Sciences - PNAS,
02/2009, Letnik:
106, Številka:
5
Journal Article
Recenzirano
Odprti dostop
We have combined ultrasensitive magnetic resonance force microscopy (MRFM) with 3D image reconstruction to achieve magnetic resonance imaging (MRI) with resolution <10 nm. The image reconstruction ...converts measured magnetic force data into a 3D map of nuclear spin density, taking advantage of the unique characteristics of the "resonant slice" that is projected outward from a nanoscale magnetic tip. The basic principles are demonstrated by imaging the ¹H spin density within individual tobacco mosaic virus particles sitting on a nanometer-thick layer of adsorbed hydrocarbons. This result, which represents a 100 million-fold improvement in volume resolution over conventional MRI, demonstrates the potential of MRFM as a tool for 3D, elementally selective imaging on the nanometer scale.
Nonvolatile RAM using resistance contrast in phase-change materials or phase-change RAM (PCRAM) is a promising technology for future storage-class memory. However, such a technology can succeed only ...if it can scale smaller in size, given the increasingly tiny memory cells that are projected for future technology nodes (i.e., generations). We first discuss the critical aspects that may affect the scaling of PCRAM, including materials properties, power consumption during programming and read operations, thermal cross-talk between memory cells, and failure mechanisms. We then discuss experiments that directly address the scaling properties of the phase-change materials themselves, including studies of phase transitions in both nanoparticles and ultrathin films as a function of particle size and film thickness. This work in materials directly motivated the successful creation of a series of prototype PCRAM devices, which have been fabricated and tested at phase-change material cross-sections with extremely small dimensions as low as 3 nm × 20 nm. These device measurements provide a clear demonstration of the excellent scaling potential offered by this technology, and they are also consistent with the scaling behavior predicted by extensive device simulations. Finally, we discuss issues of device integration and cell design, manufacturability, and reliability. PUBLICATION ABSTRACT
Magnetic resonance imaging, with its ability to provide three-dimensional, elementally selective imaging without radiation damage, has had a revolutionary impact in many fields, especially medicine ...and the neurosciences. Although challenging, its extension to the nanometre scale could provide a powerful new tool for the nanosciences, especially if it can provide a means for non-destructively visualizing the full three-dimensional morphology of complex nanostructures, including biomolecules. To achieve this potential, innovative new detection strategies are required to overcome the severe sensitivity limitations of conventional inductive detection techniques. One successful example is magnetic resonance force microscopy, which has demonstrated three-dimensional imaging of proton NMR with resolution on the order of 10 nm, but with the requirement of operating at cryogenic temperatures. Nitrogen-vacancy (NV) centres in diamond offer an alternative detection strategy for nanoscale magnetic resonance imaging that is operable at room temperature. Here, we demonstrate two-dimensional imaging of (1)H NMR from a polymer test sample using a single NV centre in diamond as the sensor. The NV centre detects the oscillating magnetic field from precessing protons as the sample is scanned past the NV centre. A spatial resolution of ∼12 nm is shown, limited primarily by the scan resolution.
We discuss multipulse magnetometry that exploits all three magnetic sublevels of the S=1 nitrogen-vacancy center in diamond to achieve enhanced magnetic field sensitivity. Based on dual frequency ...microwave pulsing, the scheme is twice as sensitive to ac magnetic fields as conventional two-level magnetometry. We derive the spin evolution operator for dual frequency microwave excitation and show its effectiveness for double-quantum state swaps. Using multipulse sequences of up to 128 pulses under optimized conditions, we show enhancement of the SNR by up to a factor of 2 in detecting NMR statistical signals, with a 4× enhancement theoretically possible.
Vibrational Promotion of Electron Transfer Huang, Yuhui; Rettner, Charles T.; Auerbach, Daniel J. ...
Science (American Association for the Advancement of Science),
10/2000, Letnik:
290, Številka:
5489
Journal Article
Recenzirano
By using laser methods to prepare specific quantum states of gas-phase nitric oxide molecules, we examined the role of vibrational motion in electron transfer to a molecule from a metal surface free ...from the complicating influence of solvation effects. The signature of the electron transfer process is a highly efficient multiquantum vibrational relaxation event, where the nitrogen oxide loses hundreds of kilojoules per mole of energy on a subpicosecond time scale. These results cannot be explained simply on the basis of Franck-Condon factors. The large-amplitude vibrational motion associated with molecules in high vibrational states strongly modulates the energetic driving force of the electron transfer reaction. These results show the importance of molecular vibration in promoting electron transfer reactions, a class of chemistry important to molecular electronics devices, solar energy conversion, and many biological processes.
Patterned magnetic structures with sizes ranging from 30 nm to 5 /spl mu/m have been fabricated to investigate the magnetization reversal of Co/Pd islands with perpendicular anisotropy. The ...nucleation field for reversal in islands capable of supporting a multidomain ground state (size ranging from 200 nm to 5 /spl mu/m) is higher than the domain wall propagation field and is characterized by a Stoner-Wohlfarth-like angle dependence. Pre-reversed nucleation sites in the islands leads to the 1/cos(/spl theta/) switching behavior indicative of domain wall motion.
The Stereodynamics of a Gas-Surface Reaction Hou, H.; Gulding, S. J.; Rettner, C. T. ...
Science (American Association for the Advancement of Science),
07/1997, Letnik:
277, Številka:
5322
Journal Article
Recenzirano
Measurements of the influence of reactant alignment on the rates of chemical reactions provide direct information concerning the atomic motions necessary for chemical transformation. Data presented ...here show that at low collision energy, the dissociative adsorption of deuterlum (D$_2$) on the (111) surface of copper has a much higher probability for broadside than for end-on collisions. Furthermore, this steric preference is sensitive to the kinetic energy of the incident molecule, almost disappearing as the energy increases to 0.8 electron volt. This study shows that the dynamic conditions of a surface chemical reaction can profoundly influence the associated steric requirements.
Magnetic resonance force microscopy (MRFM) makes use of the spectroscopic nature of magnetic resonance to add unambiguous elemental selectivity to scanning probe microscopy. We show isotopic ...selectivity of MRFM for three nuclei, 1H, 31P, and 13C, in organic materials. We also detect a roughly 1 nm thick layer of naturally occurring adsorbates on a gold surface by measuring the magnetic resonance signal of the hydrogen contained in the layer. Finally, we detect the signal from hydrogen present on a carbon nanotube and use it to perform a three-dimensional magnetic resonance image of the 10 nm diameter object.
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