We investigated the microstructure of the iron selenide superconductor (K0.7Na0.3)Fe2−ySe2 with a Tc = 32 K and a near 100% Meissner screening volume fraction. Topography and electron transport properties were studied using electron microscopy and ultra-high vacuum scanning tunneling microscopy (STM) techniques. Room temperature STM measurements reliably identify spatial variations of the local electronic properties of this material. The studied crystals consist of continuous regions with significantly different shapes of current-voltage curves reflecting different electronic transport properties of these regions. Fitting of the local current-voltage curves with the Simmons model for metal-dielectric-metal structure confirmed a phase separation in the sample to a metal and semiconducting phases. The observed regions have dimensions in the range of several tenths of a micrometer and indicate a phase separation in the sample.

Using a carbon nanotube (CNT) bundle tip as a field emitter, we have observed both Coulomb blockade and interference fringes in consecutive measurements. When Coulomb blockade is observed, decoherence of the electron wave occurs. This was observed using a double-tunnel junction consisting of a CNT tip and a CNT sample. When the CNT sample was projected onto a screen by an electron wave from the CNT tip, interference fringes were observed. This shows that the electron is first observed at the central electrode as a Coulomb blockade, next it is observed at the CNT sample as current when the electron leaves from the central electrode (the CNT tip) and finally observed as fringes passing through the CNT sample. These results show that the system's wave function cannot be written as a direct product of independent substates.

While previous books about nanometer scale phenomena have dealt with either electronic states or electromagnetic fields, this book is concerned with both as a unified whole. The characteristics of electrons or electromagnetic fields apparent at nanometer scales are quite different from those at the macroscopic scale. Nowadays these areas are called nanoscience or nanotechnology. They attract the interest of a wide range of people for their applications to new branches of technology [1–15].

Atomically ordered array of Cu atoms on the Cu(100) surface was observed by a scanning tunneling microscope (STM) in ultrahigh vacuum (UHV) at room temperature. STM-induced photon emission spectra from the Cu(100) surface were investigated by a photon detection system combined with the UHV-STM. The starting bias voltage of the detectable photon emission is 2.2 V. The spectrum shape is dominated by the imaginary part of the dielectric function of copper and exhibits a characteristic peak around 2.0 eV. The emission intensity increases almost linearly with tunneling currents but not monotoniously with bias voltages. No apparent bias-polarity dependence in the emission spectra was found. The spectral features are interpreted on the basis of the radiative decay of localized plamons excited by inelastic tunneling electrons.

Atomically ordered array of Cu atoms on a clean single-crystal Cu (100) surface has been observed on both occupied and empty sample states by scanning tunneling microscopy in ultrahigh vacuum at room temperature. An average corrugation amplitude of ∼0.4 Å is found in the empty state while it is only ∼0.06 Å in the occupied state. Atomic spacing is measured and the results are in good agreement with the known copper interatomic distance of 2.6 Å.

Highly conductive and transparent indium tin oxide (ITO) thin films, each with a thickness of 100 nm, were deposited on glass and Si(100) by direct current (DC) magnetron sputtering under an argon (Ar) atmosphere using an ITO target composed of 95% indium oxide and 5% tin oxide for photon-STM use. X-ray diffraction, STM observations, resistivity and transmission measurements were carried out to study the formation of the films at substrate temperatures between 40 and 400 °C and the effects of thermal annealing in air between 200 and 400 °C for between1 and 5 h. The film properties were highly dependent on deposition conditions and on post-deposition film treatment. The films deposited under an Ar atmosphere pressure of ∼1.7×10-3 Torr by DC power sputtering (100 W) at substrate temperatures between 40 and 400 °C exhibited resistivities in the range 3.0–5.7×10-5 Ω m and transmissions in the range 71–79%. After deposition and annealing in air at 300 °C for 1 h, the films showed resistivities in the range 2.9–4.0×10-5 Ω m and transmissions in the range 78–81%. Resistivity and transmission measurements showed that in order to improve conductive and transparent properties, 2 h annealing in air at 300 °C was necessary. X-ray diffraction data supported the experimental measurements of resistivity and transmission on the studies of annealing time. The surface roughness and film uniformity improve with increasing substrate temperature. STM observations found the ITO films deposited at a substrate temperature of 325 °C, and up to 400 °C, had domains with crystalline structures. After deposition and annealing in air at 300 °C for 1 h the films still exhibited similar domains. However, after deposition at substrate temperatures from 40 °C to 300 °C, and annealing in air at 300 °C for 1 h, the films were shown to be amorphous. More importantly, the STM studies found that the ITO film surfaces were most likely to break after deposition at a substrate temperature of 325 °C and annealing in air at 300 °C for 2 or 3 h. Such findings give some inspiration to us in interpreting the effects of annealing on the improvement of conductive and transparent properties and on the transition of phases. In addition, correlations between the conductive/transparent properties and the phase transition, the annealing time and the phase transition, and the conductive/transparent properties and the annealing time have been investigated.

Conductive and transparent indium tin oxide (ITO) films with a thickness of 100 nm were deposited onto glasses and Si(100) wafers by direct current (DC) and radio frequency (RF) magnetron sputtering. The formation and the annealing effect of films were studied by the measurements of resistivity, optical-transmission, X-ray diffraction and scanning tunneling microscopy (STM). Experimental studies indicated those films deposited by DC sputtering in a 1% O2 in an O2/Ar gas mixture, without annealing, have the lowest resistivity and the highest transmission. In addition, the films deposited by RF sputtering in a 3% O2 in an O2/Ar gas mixture, with annealing in air at 300°C for 2 h, have better resistivity and transmission.

Self-assembled monolayers (SAMs) of 1,5-pentanedithiol and 1,9-nonanedithiol on Au (111) surfaces were used to adsorb copper ions (Cu2+) from an ethanolic solution of cupric chloride (CuCl2) by chemical interaction of thiol groups and copper ions assembling multilayer structures. Ellipsometry, contact angle measurement and X-ray photoelectron spectroscopy (XPS) confirmed that the alkanedithiol molecules formed SAMs with only one-ended thiol groups attached to the gold surface, leaving the other-ended thiol groups free, which is supported by the molecular mechanics calculation. XPS and X-ray Auger electron spectroscopy (XAES) not only indicate that copper ions deposited onto SAMs from the solution by the chemical reaction of copper ions with ended free thiol groups of SAMs, but more importantly demonstrate that copper is present in the +1 oxidation state in the multilayer system. Atomic Force microscopy (AFM) was used to observe SAMs and multilayer structures.

Photon emission induced by tunneling electrons has been observed from a submonolayer of Cu-tetra-[3,5-di-t-butylphenyl]porphyrin (Cu-TBPP) molecules chemisorbed on a Cu(100) surface in ultrahigh vacuum. Near-field photons generated in a nanometer-scale region with Cu-TBPP molecules were collected effectively through the apex of a conductive optical fiber tip. The photon emission mechanism can be attributed to the inelastic tunneling events involving the tip, the Cu-TBPP molecules, and the Cu(100) substrate.

On chemically modified surfaces of highly oriented pyrolytic graphite and gold-coated mica, the self-assembly of cyanine dye molecules was studied by scanning tunneling microscopy. Through the aid of a polyelectrolyte, which is oppositely charged compared with the dye, the molecules form individual ropes with lengths up to a few hundred nanometers, widths on the order of 10 nm and a few nanometers in height. Scanning tunneling spectroscopy at low temperature reveals a gap region followed by distinctive current steps in the current-voltage characteristics at some positions on the cyanine ropes. In a further experiment, the cyanine ropes were successfully attached to substrates with a gold-palladium electrode pattern.

We have observed atomically flat gold surfaces deposited on Si (111) 7×7 surfaces. These films are deposited by conventional evaporative deposition at a pressure below 2×10−6 Pa. The surface topography was taken by scanning tunneling microscopy. Atomically flat terraces as large as 100 Å separated by steps were observed. This surface should provide a good substrate for scanning tunneling microscopy studies.

Vertical and adiabatic electronic spectra have been investigated by means of combined density functional and multi-reference configuration interaction methods. Spin–orbit coupling has been determined employing a non-empirical spin–orbit mean-field operator. In the vertical absorption spectrum of isolated 7H-adenine, the transitions to the lowest 1(n→πL∗) state, the optically bright 1(πH→πL∗) state, and a so far unknown 1(πH → (Ryd, σ∗)) state are predicted to lie very close to each other. The strong 1(πH→πL∗) transition at 4.8 eV is the lowest excitation of 1(π → π∗) type in 7H-adenine. It is red shifted by about 0.3 eV with respect to the corresponding excitation in the 9H-tautomer. We find the global minimum on the S1 potential energy hypersurface at about 4.2 eV for a 1(n→πL∗) electronic structure. A potential well with a minimum at 4.3 eV exhibits mixed 1(n→πL∗)/1(πH→πL∗) character. A planar 1(πH→πL∗) structure with a potential energy of 4.6 eV constitutes a stationary point on the S1 surface. At the present stage it is unclear whether it corresponds to a minimum or a saddle-point. The lowest-lying 1(π → (Ryd, σ∗)) state is metastable with respect to N7–H14 bond dissociation. Its inner (Rydberg) potential well with an adiabatic excitation energy of 4.6 eV represents another minimum on the S1 PEH. From the theoretical results presented in this work, we conclude that isolated 7H-adenine will be able to emit photons for excitation energies below 4.7 eV(264 nm). Above this threshold singlet excited 7H-adenine can undergo ultrafast non-radiative relaxation to the electronic ground state, either by hydrogen detachment via the 1(π → (Ryd, σ∗)) channel or via a conical intersection of the 1(πH→πL∗) state along a ring puckering mode. The 3(πH→πL∗) T1 state can be efficiently populated via intersystem crossing from one of the S1 potential energy wells. Large-amplitude motions in the T1 state along an out-of-plane distortional coordinate lead to significant configuration interaction of the 1(n→πL∗) and 1(πH→πL∗) structures which lend intensity to the phosphorescence.

Since it was suggested that individual atoms can be manipulated using scanning tunneling microscope (STM), many attempts have been done to control atoms individually, but they were not successful so far. Here we show some methods for fabricating nanometerto atomic-scale structures using STM and atomic force microscope (AFM). Focus is put on how to connect these structures to macroscopic electric pads so that electron transport can be measured along these structures.

Initial growth of In on Si(100)2 × 1 was studied by scanning tunneling microscopy at room and liquid nitrogen temperatures. Indium atoms are found to nucleate preferably around SB steps and grow into one-dimensional ad-dimer chains. The individual In atoms within an ad-dimer are resolved for the first time through two maxima (∼ 3Å apart) for each oblong protrusion in the empty states. Furthermore, the orientation of the ad-dimer is evidently along the chain direction, thereby justifying the parallel ad-dimer model. We also probe the electronic nature of In ad-dimer chains through the I–V characteristics, which shows the existence of a surface-state bandgap (∼ 1.5 eV). The semiconducting property so implied and the ad-dimer chain structure are further rationalized by the Peierls pairing mechanism, that is, the half-filling of the In p-band leads to an electron-phonon coupling that animates the dimerization and opens up a gap just at the Fermi level.

Scanning tunneling microscope image of Au(111) surface shows that the coherent electron propagates more easily along the boundary (domain wall) between fcc and hep regions than fcc and hcp regions. Also, electron wave front follows the direction of this domain wall.