Confined Pulsed Diffuse Layer Charging for Nanoscale Electrodeposition with a Scanning Tunnelling Microscope

Regulating the state of the solid-liquid interface by means of electric fields is a powerful tool to control electrochemistry. In scanning probe systems, this can be confined closely to a...

Redox-addressable single-molecule junctions incorporating a persistent organic radical

The integration of radical (open-shell) species into single-molecule junctions at non-cryogenic temperatures is a key to unlocking the potential of molecular electronics in further applications. While many efforts have been devoted to this issue, in the absence of a chemical or electrochemical potential the open-shell character is lost when in contact with the metallic electrodes. Here, the organic 6-oxo-verdazyl radical, which is stable at ambient temperatures and atmosphere, has been functionalised by aurophilic 4-thioanisole groups at the 1,5-positions and fabricated into a molecular junction using the scanning tunnelling microscope break-junction technique. The verdazyl moiety retains open-shell character within the junction even at room temperature, and electrochemical gating permits in-situ reduction of the verdazyl to the closed-shell anionic state in a single-molecule transistor configuration. In addition, the bias-dependent alignment of the open-shell resonances with respect to the electrode Fermi levels gives rise to purely electronically-driven rectifying behaviour. The demonstration of a verdazyl-based molecular junction capable of integrating radical character, transistor-like switching behaviour, and rectification in a single molecular component under ambient conditions paves the way for further studies of the electronic, magnetic, and thermoelectric properties of open-shell species.

Testing short distance anisotropy in space

The isotropy of space is not a logical requirement but rather is an empirical question; indeed there is suggestive evidence that universe might be anisotropic. A plausible source of these anisotropies could be quantum gravity corrections. If these corrections happen to be between the electroweak scale and the Planck scale, then these anisotropies can have measurable consequences at short distances and their effects can be measured using ultra sensitive condensed matter systems. We investigate how such anisotropic quantum gravity corrections modify low energy physics through an anisotropic deformation of the Heisenberg algebra. We discuss how such anisotropies might be observed using a scanning tunnelling microscope.

Nanotechnology and Nanoparticles in Contemporary Sciences

Nonotechanology has been a rapidly growing field of advanced science at the inception of this century. Many problematic endeavours in sciences have been successfully overcome using nanoparticles. For example, a low risk solution using antibody modified bismuth nanoparticle, in combination with an X-ray dose equivalent to a chest X-ray specifically, has been shown to kill the common bacterium Pseudomonas aeruginosa in a set up designed to resemble a deep wound in human tissue. Nanosized gold particle could catalyse the oxidation of carbon monoxide better than anything previously known. Heparin functionalized nanoparticles have been use for targeted delivery of anti-malarial drugs. Heparin is abundant and cheap compared to treatments that involve antibodies, an important consideration, since malaria is most common in developing countries. A bone repairing nano-particle paste has been developed that promises faster repair of fractures and breakages. DNA containing two growth genes is encapsulated inside synthetic calcium phosphate nanoparticles. In a remarkable demonstration of the extreme limits of nanoscale engineering, researchers have used the tip of a scanning tunnelling microscope to cleave and form selected chemical bonds in a complex molecule. Many medicinal and industrial endeavours have seen the use of Nanotechnology. These and other more recent advances in nanotechnology will be presented at this conference

Introduction to Scanning Tunneling Microscopy

The scanning tunnelling microscope (STM) was invented by Binnig and Rohrer and received a Nobel Prize of Physics in 1986. Together with the atomic force microscope (AFM), it enables non-destructive observing and mapping atoms and molecules on solid surfaces down to a picometer resolution. A recent development is the non-destructive observation of wavefunctions in individual atoms and molecules, including nodal structures inside the wavefunctions. STM and AFM have become indespensible instruments for scientists of various disciplines, including physicists, chemists, engineers, and biologists to visualize and utilize the microscopic world around us. Since the publication of the first edition in 1993, this book has been recognized as a standard introduction for everyone that starts working with scanning probe microscopes, and a useful reference book for those more advanced in the field. After an Overview chapter accessible for newcomers at an entry level presenting the basic design, scientific background, and illustrative applications, the book has three Parts. Part I, Principles, provides the most systematic and detailed theory of its scientific bases from basic quantum mechancis and condensed-metter physics in all available literature. Quantitative analysis of its imaging mechanism for atoms, molecules, and wavefunctions is detailed. Part II, Instrumentation, provides down to earth descriptions of its building components, including piezoelectric scanners, vibration isolation, electronics, software, probe tip preparation, etc. Part III, Related methods, presenting two of its most important siblings, scanning tunnelling specgroscopy and atomic force miscsoscopy. The book has five appendices for background topics, and 405 references for further readings.

Single-charge transport through hybrid core–shell Au-ZnS quantum dots: a comprehensive analysis from a modified energy structure

We examined the modified electronic structure and single-carrier transport of individual hybrid core–shell metal–semiconductor Au-ZnS quantum dots using a scanning tunnelling microscope.

The Nature of CVC Nonlinearity in Low-Voltage Scanning Tunneling Spectroscopy of Semiconductors

A new model of field emission in a scanning tunnelling microscope was developed. The model describes the tunnelling current from a surface of semiconductor (semimetal) and allows estimating the preexponential factor in the expression for the tunneling probability. It is shown that this factor is directly related to the degree of localization of the electron density and determines the shape of the local tunnel current-voltage characteristics (LTCVCs) at low voltages. The model allows separating the contributions of surface electronic states of different symmetry (dimension) of the tunnelling current. The practical application of the model is demonstrated by the example of mathematical processing of the LTCVCs of HOPG surface containing different structural defects.

On-Surface Chemistry Using Local High Electric Fields

Dihydrotetraazapentacene (DHTAP) molecules can be dehydrogenated on the surface to form tetraazapentacene (TAP), by applying a high electric field between the tip of a scanning tunnelling microscope (STM) and a...