Papers by Keyword: Scanning Tunneling Microscopy

Abstract: An approach based on statistical analysis is proposed for the processing of data obtained using scanning tunneling microscopy of grain boundaries, which allows a numerical estimation of the relative energy of grain boundaries. The proposed statistical model also gives a possibility to separate groups of grain boundaries depending on their average relative energy and fraction in general distribution. Scanning tunneling microscopy data analyses have been carried out on data obtained by investigating copper and nanostructured copper were analyzed coarse-grain commercially pure copper and on copper nanostructured by the equal-channel angular pressing (ECAP) method. Obtained results were compared with available in literature experimental data for these types of materials, received by other methods. It is established that the grain boundaries in coarse-grain copper have significantly lower relative energy in contrast to the grain boundaries of ECAP-treated copper. Besides, there is, except for boundaries with high relative energy, a fraction of boundaries in the deformed sample with energy corresponding to those in coarse-grain copper.

Abstract: Nanoscale experiments with diamond tip that include processing, visualization and tunneling spectroscopy of the surface are presented. Single crystal diamond synthesized by the temperature gradient method under high pressure–high temperature (HPHT) conditions is proposed as a multifunctional tip for scanning tunneling microscopy (STM). Sequence of the procedures covering growing crystals with predetermined physical properties, selection of the synthesized crystals with the desired habit and their precise shaping have been developed. The original STM’s peculiarity is the electromagnetic probe-to-surface load measuring system. The results of fabrication and characterization of nanostructures for nanoelectronics, data storages and biology are demonstrated and discussed.

Abstract: Adsorption of pyrrole on the Si(111)-7×7 surface was investigated using scanning tunneling microscopy (STM). Template-induced molecular corral structure was observed at room temperature though the N-H bond cleavage. At the substrate temperature of 130 °C, the pyrrolyl adsorbates were observed by STM with reserving the 7×7 substrate. However, the self-assembly of the molecular corral structure was disarranged at 130 °C. Then, pyrrolyl group was decomposed or desorbed from the surface at the substrate temperature of 200 °C. The defect-induced attachment of pyrrole was also observed.

Abstract: Semiconductor and metal carbon nanotubes were studied by scanning tunneling microscopy (STM) and spectral ellipsometry. STM measurements with spatial resolution up to 0.15 nm reveal spatially complicated structure of semiconductor nanotube-substrate interface layer. The measurements also registered graphene nanoclusters with hexagonal rings structure on copper. Quantum mechanical numerical calculations of electron density were performed on a carbon nanotube containing 40 atoms.

Abstract: A major obstacle facing III-V semiconductor based metal oxide semiconductor field effect transistors (MOSFETs) is the large density of trap states that exist at the semiconductor/oxide interface.[1] These trap states can pin the Fermi level preventing the MOSFET from acting as a switch in logic devices. Several sources of Fermi level pinning have been proposed including oxidation of the III-V substrate.[2, 3] In order to minimize the presence of III-V oxides it is crucial to employ either an ex-situ etch or to use an in-situ method such as atomic hydrogen cleaning.[4, 5] Although atomic H cleaning of III-V surfaces is well known, it has never been demonstrated on InGaAs (110) crystallographic faces. Furthermore, tri-gate field effect transistors (finFETs) have recently been employed in commercially available logic chips.[6] This unique device architecture allows for a reduction in short channel effects, minimization of the subthreshold swing, and a higher transconductance.[7] The InGaAs (110) surface would be the sidewalls of a vertically aligned (001) based finFETs.[8] Therefore, it is essential to find an in-situ method to efficiently remove any oxides or contamination from the (110) surfaces that is also compatible with the (001) surface. In this study, STM was employed to determine if atomic hydrogen can be used to remove the native oxide from air exposed InGaAs (110) samples. A post clean anneal was used to restore the surface to molecular beam epitaxy (MBE) levels of cleanliness.

Abstract: We investigated the effect of ion-beam irradiation of the 3C-SiC(111) surface on the growth of graphene by the SiC surface-decomposition method. When a 3C-SiC(111) surface was irradiated by 1 keV Ar⁺ ions at a dose of 4.5 × 10¹⁵ cm² in an ultra-high-vacuum chamber and then annealed at 1200 °C for 1 min, the formation of graphene layers was promoted in comparison with that in the absence of ion-beam irradiation. X-ray photoelectron spectroscopy studies showed that Ar ion bombardment of the 3C-SiC(111) caused breakage of surface bonds and helped Si atoms to desorb from the surface.

Abstract: The critical phenomena on cobalt monolayer films were studied by means of computersimulation. Proposed approach on the base of data of scanning tunneling microscopy gives possibilityestimate of critical concentration needed for concentration transition into ferromagnetic state. Assumptionabout presence of critical switching field allowed simulated hysteresis loops for given 1.5,2.0, 2.5 and 3.0 ML cobalt samples in frame of Ising model, which ones have qualitative agreementwith magnetometric data.

Abstract: External micro vibration is an important obstacle factor for the measuring result of scanning tunneling microscopy. In order to achieve better result, the influence of vibration must be eliminated. In this study, a large range new sensor with two nano stages is built up to detect the micro vibration for the compensation of the results. Finnaly, the vibration detection experiments are made to illustrate the rationality of the sensor.

Abstract: Scanning tunneling microscopy is one of the surface measurement instruments in micro and nano field, and the Z-direction resolution is 0.01nm. So it is easily affected by the external factor in the course of measurement. The influence of vibration has already become one of main obstacles for improving the nano measuring accuracy. In this article, micro vibration measurement based on the tunneling effect is referred. A new sensor design of double displacement stages is brought to study the micro vibration, and both stages have the nano level displacement and resolution. Using this sensor, the tunneling effect is realized and the micro vibration is measured. The experiment results show this design has stable performance, and the results can be used to be a reference for the compensation of scanning tunneling microscopy.

Abstract: A brief review is presented of quasicrystal surfaces and their use as templates for exotic epitaxial structures. The review is illustrated with several examples from the work of the Liverpool quasicrystal group.