B. R. Shub

Isotope effect in the vibrational spectra of water measured in experiments with a scanning tunneling microscope

The vibrational frequencies of adsorbed H2O and D2O molecules are measured under high-vacuum conditions by in-cavity scanning tunneling spectroscopy. An isotope effect is observed.

SCANNING TUNNELING VIBRATIONAL SPECTROSCOPY

Abstract A new method for studying of vibronic transitions by scanning tunneling microscope (“nitraresonator electron-vibronic scanning tunneling spectroscopy of adsorbates”) is proposed. Results of experiments carried out by STM “Omicron” where electron-vibronic series of field emission resonances were observed are presented. Frequencies of the resonances correspond to ones of local vibrations of titan oxide and adsorbed hydroxil particles.

Single spin ESR

On the basis of classical scanning tunneling microscopy a new technique, single spin tunneling spectroscopy, is developed and experimentally illustrated. It allows to detect singlet and triplet channels of the tunneling current corresponding to the spin states of the pair of tunneling and unpaired electrons. The current of polarized tunneling electrons emitted by ferromagnetic tip may be controlled by resonance microwaves and allows to monitor the ESR spectrum of a single paramagnetic center. Theory of the new phenomenon is developed as a guide to the single spin ESR experimental devices.

Singlet–triplet transitions of physisorbed molecule O2 in scanning tunneling microscope

Abstract Theory is developed of inelastic spin-dependent electron tunneling through the nanocontacts containing single adsorbed molecules. This theory consistently takes into account the subbarrier elastic and inelastic electron scattering including exchanging one. Estimates are made for the probabilities of different transitions in the adsorbed molecule, which interacts with the tunneling current. At low temperatures, the threshold features of conductivity were shown to have the shape of discontinuities (conductance jumps), whose scale depends on two parameters: the relative probability of inelastic tunneling and the ratio of the spontaneous relaxation to electron-current-induced transition rates. The general analytical expressions are obtained for the shape of the STM conductance threshold features. The STM threshold features can carry the information about the relaxation time of single electron-excited adsorbed particles. As an example, the excitation of the singlet state in the physically adsorbed oxygen molecule is analyzed in details. Our calculations show that the singlet–triplet relaxation time for a single molecule O 2 adsorbed on semiconductor surface can be determined by varying the distance between the surface and the STM tip.

On the experimental possibilities of observing single spins in a STM

A method is proposed for observing the spins of individual particles by combining ESR and STM methods using a ferromagnetic needle or paramagnetic tip.

Physicochemical Properties of Nanoparticles: Interaction of Supported Platinum Nanoparticles with Gaseous Reactants

The shapes, sizes, and electronic structures of platinum nanoparticles supported onto highly oriented pyrolytic graphite and oxidized silicon by different methods and their adsorptive properties with respect to hydrogen, oxygen, water, and ammonia were established. The apparent activation energy of the reduction of single oxidized platinum nanoparticles with molecular hydrogen was determined. The possibility of controlling the rate of ammonia decomposition by a nanostructured platinum coating by the application of electric potentials of different values and polarities to it was demonstrated.