摘要:

Many device scientists believe that current Ultra Large Scale Integration (ULSI) technology will face technical and economic difficulties in further miniaturization. It has been predicted that 1‐dimensional (1‐D) transistors with connecting wires in three‐dimensionally stacked structures may replace current field effect transistors in planar integration structures. We propose a new scheme to fabricate and integrate 1‐D active devices. As a first step, we show the way to form 1‐D wires with spatially variable electronic structures and the way to characterize them. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1639681

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

We examine properties of boron nitride nanotubes and contrast them to those of carbon nanotubes. Boron nitride nanotubes are expected to be as desirable for application as carbon nanotubes. Although boron nitride nanotubes are wide band gap semiconductors and electrically nearly insulating, scanning tunneling microscopy can be used to image and characterize them. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1639682

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

We use a novel low‐temperature scanning tunneling microscope to study the motion of individual CO molecules in molecule cascades on a copper (111) surface. The microscope has a base temperature of 1K in continuous circulation of3He and 0.5K in a single shot mode with a hold time of about 10 hours. The initial liquefaction of3He is achieved by utilizing Joule‐Thomson expansion of3He gas which eliminates the need for a pumped4He reservoir. Samples can be prepared and transferred into the microscope in ultra high vacuum. We found a strong dependence of the hopping rate on the carbon isotope, which leads us to the conclusion that CO molecules tunnel from initial to final state at temperatures below 6K. At higher temperatures a thermally activated process contributes to the hopping rate and several models for this process are discussed. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1639683

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

We present a detailed investigation of the manipulation of Ag and Au atoms with a STM tip on the Ag(111) surface at 5K. The interpretation of the feed‐back loop signal gives a precise picture of the movement of the atom during manipulation. The threshold tunnelling resistance and tip‐height to move a Au/Ag atom have been determined using automated manipulation measurements. The results show that at low biases chemical forces dominate in the manipulation process. Above ≈ ±70 mV tunnelling voltage Au atoms start to move already at greater tip‐atom separation, which can be attributed to a current effect. Tip‐induced diffusion was used to measure the influence of the electric field which can be ruled out at low biases. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1639684

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

The scanning tunneling microscope is not only a well‐established tool for a topographic characterization of the sample surface on the atomic scale. It also provides a variety of spectroscopic techniques to examine electronic, magnetic, vibrational and optical properties of a localized system. The following presentation gives an overview, how scanning tunneling spectroscopy, inelastic electron tunneling spectroscopy and photon emission spectroscopy with the STM can be employed to investigate spatially confined metal systems and their interaction with molecular gases. The experiments were performed on single Pd and Au atoms, mono‐atomic chains and individual Ag clusters on a NiAl support and a Al2O3thin film. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1639685

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

We have applied a new method to localize single dye molecules with nanometer resolution in three dimensions by means of the Stark effect. With this method we were able to resolve two molecules which were so close to each other that they underwent a strong dipole‐dipole interaction. A quantitative spectral study of this system allowed us to determine the coupling parameters. In the second part of this paper we discuss our research on metal nanoparticles. We have developed a method to mount single nanoparticles at the very end of a fibre tip. We have used such probes as well defined scattering centers for apertureless scanning near‐field optical microscopy. In this article we also discuss our efforts to examine the interaction of a single metal nanoparticle and a single molecule in a controlled manner. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1639686

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

Vibrational excitation of single molecules at surfaces will open an ultimate way of the reaction control in nano‐meter scale. Direct excitation along the reaction coordinate coupled with the multiple excitations will lead to molecule‐to‐molecule chemistry. For the indirect process, anharmonic coupling between the excited vibrational state and the reaction coordinate plays an important role. Action spectrum for cic‐2‐butene on Pd(110) exhibits low frequency vibrational modes are excited by inelastic tunneling but are not clearly visible in STM‐IETS. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1639687

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

We report the construction of complex metal‐organic assemblies at surfaces using concepts from coordination chemistry. Well‐ordered supramolecular assemblies and metal‐organic coordination networks with specific topologies and a high structural stability have been fabricated under ultra‐high vacuum conditions by sequential deposition of polyfunctional organic molecules and Fe atoms onto an atomically clean Cu(100) substrate. The structures were investigated at the molecular level byin‐situscanning tunneling microscopy. The precise control of the concentration ratio of the components and the annealing treatment allow for the assembly of distinct architectures. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1639688

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

Minute patterns have been fabricated on organosilane self‐assembled monolayers (SAMs) based on scanning probe surface modification. An SAM was prepared on Si substrates from an organosilane precursor. First, using an atomic force microscope (AFM) with a conductive probe, current was injected from the probe into the SAM‐covered Si substrate so that the SAM was locally degraded at the probe‐contacting point. The patterning could be conducted in air while, in vacuum at the order of 10−6Torr, or in an atmosphere purged with nitrogen, no detectable patterns were fabricated. The presence of adsorbed water at the probe/sample junction was confirmed to be crucial for the patterning of the SAM/Si. Its mechanism was, thus, ascribed to electrochemical reactions of the SAM with adsorbed water. Furthermore, we demonstrated the chemical conversion of terminal functional groups on the SAM by the current injecting AFM. The results were confirmed through surface potential imaging by Kelvin probe force microscopy and a chemical labeling method. An SAM terminated with −CH3groups was found to be converted to a COOH‐terminated SAM due to anodic oxidation. The tip‐induced electrochemical reduction from −NO to −NH2was successfully conducted as well. Both the oxidation and reduction reactions have been shown applicable to scanning probe surface modification. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1639689

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

Biological life may be viewed as a hierarchy of molecular processes, where complexity is further compounded by the fact that individual biological nanomachines (i.e. nucleic acids, proteins, molecules) can have many different functions. Conventional biological techniques, however, only detect sufficient signals from large assemblies of cellular machines. Consequently, the measured function of a species is commonly enveloped by a Gaussian distribution. However, why do these nanomachines behave and function individually? Which reaction pathways do they choose? What are their trajectories and how do they interact with each other? What aspects of their structure give rise to variance in their behavior? The exceptionally high spatial resolution and signal‐to‐noise ratio of the atomic force microscope (AFM) allows the substructure of individual molecules to be observed. In contrast to other microscopic methods, biological specimens prepared for AFM remain in a plastic state amenable to the direct observation of molecular dynamics, creating unique opportunities to access the structure‐function relationships of proteins and their functionally relevant assemblies. This review presents recent advances in method and the application of AFM to investigate biological nanomachines in means of their structure‐function relationship, of their controlled manipulation and of interactions within their functional three‐dimensional structure. It is clear, that AFM and relatives to this technique will become an increasingly important tool for probing both the structural and kinetic properties of biological macromolecules. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1639690

出版商:AIP    

年代:1903

数据来源: AIP