Download Free Single Molecule Rotational Inelastic Electron Tunneling Spectroscopy And Microscopy Book in PDF and EPUB Free Download. You can read online Single Molecule Rotational Inelastic Electron Tunneling Spectroscopy And Microscopy and write the review.

The power of rotational spectroscopy has long been demonstrated in the frequency domain by microwave spectroscopy, but its application in real space has been limited. Using a scanning tunneling microscope (STM) and inelastic electron tunneling spectroscopy (IETS), we were able to conduct real-space measurements of rotational transitions of gaseous hydrogen molecules physisorbed on surfaces at 10 K. The j=0 to j=2 rotational transition for para-H 2 and HD were observed by STM-IETS. It is also found that the rotational energy is very sensitive to its local environment, we could precisely investigate how the environmental coupling modifies the structure, including the bond length, of a single molecule with sub-Angstrom resolution. Due to this high sensitivity, the spatial variation in the potential energy surface can be quantified by the rotational and vibrational energies of the trapped H 2. The ability of the tip to drag along a hydrogen molecule as it scans over another adsorbed molecule combined with the sensitivity of the hydrogen rotational excitation recorded by IETS to its immediate environment lead to the implementation of rotational spectromicroscopy. Hydrogen rotational spectroscopy and microscopy provides novels approach toward visualizing and quantifying the intermolecular interaction as well as the intermediate processes of chemical reactions.
The goal of the studies presented in this dissertation is to continuously expand the capability of a scanning tunneling microscope (STM) by improving its chemical sensitivity and temporal resolution. It has been demonstrated that the combination of STM with other techniques gains insight into the physical and chemical properties of single molecules. Single molecule rotational spectroscopy and microscopy is demonstrated using STM inelastic tunneling spectroscopy (IETS). We conduct real-space measurements of rotational transitions of gaseous hydrogen molecules physisorbed on surfaces at 10 K. The j = 0 to j = 2 rotational transition for para-H2 and HD were observed by STM-IETS. It is also found that the rotational energy is very sensitive to its local environment, we could precisely investigate how the environmental coupling modifies the structure, including the bond length, of a single molecule with sub-Angstrom resolution. Due to this high sensitivity, the spatial variation in the potential energy surface can be quantified by the rotational and vibrational energies of the trapped H2. The ability of the tip to drag along a hydrogen molecule as it scans over another adsorbed molecule combined with the sensitivity of the hydrogen rotational excitation recorded by IETS to its immediate environment lead to the implementation of rotational spectromicroscopy, which helps us reveal the intermolecular interaction and charge transfer between H2 and a large molecule. Furthermore, we demonstrate that the H 2 in the STM junction can be dissociated by the mechanical motion of the STM tip. Hydrogen rotational spectroscopy and microscopy provides novels approach toward visualizing and quantifying the local potential energy surface as well as the potential landscape of chemical reactions.Joint Angstrom-femtosecond resolution is achieved by the combination of an STM with a femtosecond laser. We demonstrate the bond-selected, photo-assisted activation of a single C-H bond in an azulene molecule adsorbed on a Ag(110) surface. When the junction is illuminated by femtosecond laser, the electrons in the tip can be photo-excited into higher energy states and dissociate the molecule through a photo-assisted tunneling process. The photon-electron coupling at the junction enables the investigation of coherence molecular transformation with joint fs-A resolution. We also show the band bending and laser induced band flattening at a molecule-semiconductor interface. More importantly, we observe the photo-induced, reversible conformational change between two structures for a single pyrrolidine molecule on a Cu(001) surface. The conductance changes of the STM junction associated with the structural transitions exhibits oscillates in time with periods corresponding to specific molecular vibrations. The vibrational frequencies and decay time are observed in real-space and real-time. Our laser-STM technique enables the investigation of inhomogeneous environmental effect on the molecular dynamics. We have found that the intermolecular interaction between two pyrrolidine molecules can increase the vibrational period while shortening its decay time. We anticipate that this novel technique would lead to a broad impact in physics and chemistry through direct visualization of coherently driven reactions resolved in space and time.
Scanning Tunneling Microscope (STM) has become a powerful tool in nanoscience for imaging, manipulation and electronic spectroscopy. STM inelastic electron tunneling spectroscopy (IETS) first achieved chemical identification of molecular species by characterizing vibrational energies. Recently, with the STM itProbe and H2 rotational spectromicroscopy, molecular structure and chemical bonds are observed with the STM. Despite these successes in spatial resolution, various efforts have been made to combine fs laser with STM to overcome the temporal resolution limitation of STM, there is so far no clear evidence of simultaneous fs and Å resolution. Electronic properties of organic molecules are of central importance to applications such as molecular electronics, organic LEDs, and solar cells. Properties of these molecules can be probed by the scanning tunneling microscope (STM) at the single molecule level and with sub-Å spatial resolution. The molecular orbital of 4, 7-Di ([2, 20-bithiophen]-5-yl) benzo[c] [1, 2, 5] thiadiazole (4T-BTD) with intramolecular donor-acceptor-donor sites is probed with the electronic state dI/dV imaging and H2 rotational and vibrational spectromicroscopy. 1, 4-Phenylene Diisocyanide (PDI) is probed by imaging with a CO-terminated tip and H2. PDI can self-assemble on noble metal surfaces to form nanostructures, which could have potential applications in molecular electronics and catalysis. Further combination of a RF-STM with a tunable femtosecond laser enables the investigation of light-molecule interactions. In this dissertation, efforts are spent to setup a new tunable fs laser (220 nm∼1040 nm) to couple with the RF-STM. The effects of the femtosecond laser are followed by detecting photo induced electron emission and photochemistry. A new double lock-in technique is applied to detect the weak laser-induced signal in the tunneling regime. To sharpen the energy width and increase the lifetime of the excited states of molecules, thin aluminum oxide and copper oxide are grown on metal surfaces to provide electronic isolation of the metal substrate and adsorbed molecules. Metal nanoclusters are grown on metal and oxide to improve laser-induced signal through plasmonic enhancements.
With a 600mk homebuilt UHV STM system, we studied molecular vibration at the solid surface with inelastic electron tunneling spectroscopy (IETS) of Acetylene single molecules adsorbed on Cu(100) surface and revealed five new vibrational modes that were previously inaccessible to STM-IETS at 8K temperature. The identification of vibrational IETS features with normalized conductance change (Î4Ï3/Ï3) as low as 0.24% was demonstrated. Facilitated by the high energy resolution, we also revealed the anisotropic vibrational energy of carbon0́3monoxide (CO) molecule induced by substrate surface symmetry. The discrepancy in vibrational energy as small as 0.8meV can be resolved by STM-IETS. Our results also showed that the change in vibrational behavior of CO can be used to understand its environment. CO can be vertically transferred from substrate surface to STM tip and creates a scanning probe which has the characteristic vibrational signal of CO contained in the inelastic component of the tunneling current; i.e. the inelastic tunneling probe (itProbe). The itProbe senses the local potential energy landscape by imaging the spatial variations of CO hindered-translational mode and resolves the skeletal structure and bonding details of a surface adsorbed Cobalt-Phthalocyanine molecule (CoPc). The image contrast of itProbe also reveals the interaction between one CoPc and the substrate surface as well as the interaction paths between neighboring CoPcs.
This dissertation discusses the theoretical basis and experimental applications to improving the capability of the STM in chemical and optical sensitivity. Traditional STM methods have achieved unprecedented spatial resolution, but suffer from a lack of sensitivity to chemical structure and composition. A new method of imaging, based on inelastic electron tunneling spectroscopy (IETS) measurement of hydrogen molecules is developed. The interaction of plasmon excitations to electronic states of a metal nano-cluster is also studied, allowing for better understanding of the mechanisms involved in the plasmon --- electron coupling.Since its application at the single molecule level in the STM was realized, IETS has been used to identify different molecules through their vibrational signal. In recent experiments, rotational excitation of H2 was detected on metal and insulator surfaces. It was found that the energy of these excitations depend sensitively on the local chemical environment. By monitoring the rotational and vibrational IETS signal of the H2 across the molecule, a more chemically sensitive image can be constructed. When the method is applied to imaging magnesium porphyrin (MgP) on Au (110), different components of the molecule can be observed at different energies. These differences are indication of how the various components interact with the H2.Optical sensitivity of the STM manifests in the detection of photons emitted from the tunnel junction. Previous experiments have shown that we can map the excitation of molecular fluorescence with sub-Angstrom resolution. For applications in photochemistry and catalysis, understanding how plasmons interact with photons and electrons is crucial. Light emission from Au nanoclusters on oxide shows strong correlation with their electronic states. The interaction between plasmon mode in the junction and electronic states of the nano-clusters is further studied through clusters of different sizes and dimers. Emission of light from molecular orbitals is also investigated in panhematin and azulene molecules. Coupling of molecular orbital and vibronic states to junction plasmon is found and visualized through light emission spectrum and imaging.
This handbook delivers an up-to-date, comprehensive and authoritative coverage of the broad field of surface science, encompassing a range of important materials such metals, semiconductors, insulators, ultrathin films and supported nanoobjects. Over 100 experts from all branches of experiment and theory review in 39 chapters all major aspects of solid-state surfaces, from basic principles to applications, including the latest, ground-breaking research results. Beginning with the fundamental background of kinetics and thermodynamics at surfaces, the handbook leads the reader through the basics of crystallographic structures and electronic properties, to the advanced topics at the forefront of current research. These include but are not limited to novel applications in nanoelectronics, nanomechanical devices, plasmonics, carbon films, catalysis, and biology. The handbook is an ideal reference guide and instructional aid for a wide range of physicists, chemists, materials scientists and engineers active throughout academic and industrial research.
The goal of this book is to provide a general overview of the rapidly developing field of novel scanning probe microscopy (SPM) techniques for characterization of a wide range of functional materials, including complex oxides, biopolymers, and semiconductors. Many recent advances in condensed matter physics and materials science, including transport mechanisms in carbon nanostructures and the role of disorder on high temperature superconductivity, would have been impossible without SPM. The unique aspect of SPM is its potential for imaging functional properties of materials as opposed to structural characterization by electron microscopy. Examples include electrical transport and magnetic, optical, and electromechanical properties. By bringing together critical reviews by leading researchers on the application of SPM to to the nanoscale characterization of functional materials properties, this book provides insight into fundamental and technological advances and future trends in key areas of nanoscience and nanotechnology.
This thesis presents a series of experimental techniques based on scanning probe microscopy, which make it possible access the degree of freedom of protons both in real and energy space. These novel techniques and methods allow direct visualization of the concerted quantum tunneling of protons within the hydrogen-bonded network and quantification of the quantum component of a single hydrogen bond at a water–solid interface for the first time. Furthermore, the thesis demonstrates that the anharmonic quantum fluctuations of hydrogen nuclei further weaken the weak hydrogen bonds and strengthen the strong ones. However, this trend was reversed when the hydrogen bond coupled to the local environment. These pioneering findings substantially advance our understanding of the quantum nature of H bonds at the molecular level.