The effect of KI on the formation of Tl2E (E=S, Se) nanorods via solvothermal route

Tl₂E (E=S or Se) nanorods were synthesized via solvothermal route with the addition of KI. The products were characterized with X-ray powder diffraction patterns and transmission electron microscope images. Their optical properties were studied by UV-vis transmittance and photoluminescence spectrum. The band gap of direct forbidden transitions was found larger than that of bulk materials, because of the blue shift caused by nanometer-scale crystalline particles due to quantum confinement effects. A possible growth mechanism is proposed.     

Formation of Charged Particle Tracks in Solids

A criterion for formation of etchable tracks in solids is suggested using the well-known concepts of ionization and thermal spikes, diffusion process with useful and justified assumptions, and present or published experimental and theoretical investigations on the same subject. The suggested criterion is useful for a wide spectrum of researchers including development and applications of track recording materials, ions implantation, sputtering and other areas, which include interactions of charged particles with solids.     

Manipulation of nanoparticles using dynamic force microscopy: simulation and experiments

82 , M = Sc, Y, La) are discussed. The first ¹³C hyperfine structure has been analyzed in detail and at least seven electronically different groups of carbon atoms could be assigned by simulations of the ESR spectra. The strong similarity of the ¹³C satellite structure suggests the preference of one cage isomer for the scandium group C₈₂ endohedrals. The geometric structure and the electronic structure of all nine fullerene cage isomers of La@C₈₂ were studied by approximate density-functional-based theoretical calculations. A C_3v isomer was found as the most stable one. The manifold of ¹³C hyperfine coupling constants could be interpreted on the basis of the calculated spin density distributions. Received: 15 September 1997/Accepted: 16 October 1997     

Fabrication and characterization of In2O3 nanowires

In₂O₃ nanowires were successfully fabricated through a simple gas-reaction route in argon atmosphere. These nanowires have diameters ranging from 20 nm to 50 nm and lengths up to tens of micrometers. High-resolution transmission electron microscopy observations and the electron-diffraction (ED) pattern reveal that the In₂O₃ nanowires are formed by the stacking of (2) planes along the [1] direction, which is parallel to the wire axis. A strong and wide ultraviolet (UV) emission band centered at around 392 nm is observed for the first time in the room-temperature photoluminescence measurement in addition to the usual blue emission (468 nm). Moreover, five discrete fine peaks (372 nm, 383 nm, 406 nm, 392 nm and 413 nm) are further identified in this broad UV band. Received: 10 April 2002 / Accepted: 12 April 2002 / Published online: 19 July 2002     

Limiting fragmentation from scale-invariant merging of fast partons

Exploiting the idea that the fast partons of an energetic projectile can be treated as sources of colour radiation interpreted as wee partons, it is shown that the recently observed property of extended limiting fragmentation implies a scaling law for the rapidity distribution of fast partons. This leads to a picture of a self-similar process where, for fixed total rapidity Y  , the sources merge with probability varying as 1/y$1/y$.     

A new in-situ surface treatment during MBE-grown PbSe on CaF2/Si(1 1 1) heterostructure

The continual improvement of IV-VI materials grown by molecular beam epitaxy (MBE) is a key step in the development of IV-VI infrared semiconductor devices on silicon substrates. This study presents a novel surface-treatment method which is carried out during MBE growth of monocrystalline PbSe on Si(1 1 1)-oriented substrates. Details of the experimental procedures are described and supported by reflection high-energy electron diffraction (RHEED) patterns. The effect of the in-situ surface-treatment method is exhibited in the forms of improved electrical and morphological properties of PbSe thin films. Specially, the carrier mobility increases almost three-fold at 77 K and nearly two-fold at 300 K. The density of the growth pits undergoes almost three-fold reduction, whereas the density of the threading dislocations decreases around four-fold.     

Synthesis and ammonia sensing property of Ag3CuS2 nanocages obtained from Cu7S4 18-facet hollow nanopolyhedra

Ag₃CuS₂ nanocages were successfully fabricated for the first time via a convenient ion-exchange route by Ag⁺ reacting with Cu₇S₄ 18-facet hollow nanopolyhedra. The average size and shell thickness of Ag₃CuS₂ nanocages were around 400 and 30 nm, respectively. Room-temperature response of Ag₃CuS₂ nanocages to ammonia was investigated by photoluminescence-type sensor. Sensing results suggested that these hollow-structured Ag₃CuS₂ exhibited better performances including higher sensitivity, shorter response and recovery time than their rod-shape counterparts. A possible hole trapping mechanism was proposed.     

Ordered arrays of high-quality single-crystalline α-Si3N4 nanowires: Synthesis,properties and applications

Ordered arrays of high-quality single-crystalline α-Si₃N₄ nanowires (NWs) have been synthesized via thermal evaporation and detailed characteristics of the NWs have been analyzed by employing scanning electron microscope (SEM) along with energy dispersive spectroscopy (EDS), high-resolution transmission electron microscope (HRTEM), X-ray diffraction (XRD), X-ray photospectroscopy (XPS), infrared (IR), photoluminescence (PL) and in situ I–V measurements by STM/TEM holder. The microscopic results revealed that the NWs having diameter in the range of ~30–100 nm and length in microns. Furthermore, the NWs are found to be single crystalline grown along [0 0 1] direction. The elemental composition and valence states of elements are analyzed by EDS and XPS. The room temperature PL spectra exhibit a broad range visible emission band. The electron transport property of a single NW illustrates the symmetric I–V curve of a semiconductor. The possible growth mechanism is also briefly discussed.     

Spontaneous and field-induced magnetic transitions in YBaCo2O5.5

A detailed study of magnetic properties of cobaltite YBaCo₂O_5.5 has been performed in high (up to 35 T) magnetic fields and under hydrostatic pressure up to 0.8 GPa. The temperatures of paramagnet-ferromagnet (PM-FM) and ferromagnet-antiferromagnet (FM-AF) phase transitions and their pressure derivatives have been determined. It has been revealed that in the compound with yttrium, in contrast to those with magnetic rare earth atoms, the AF-FM field-induced magnetic phase transition is accompanied by a considerable field hysteresis below 240 K, and the magnetic field of 35 T is not sufficient to complete this transition at low temperatures. The hysteresis value depends on the magnetic field sweep rate, which considered as an evidence of magnetic viscosity that is especially strong in the region of coexistence of the FM and AF phases. High values of susceptibility for the field-induced FM phase show that Co spin state in these compounds changes in strong magnetic field.     

Sequential double Auger decay in atoms: A quantum informatic analysis

We theoretically show that the process of inner-shell photoionization in an atom A, followed by the spontaneous sequential emission of two Auger electrons, produces various kinds of spin-entangled states of three flying electronic qubits. All properties of these states are completely pre-determined by the total spin quantum numbers of the electronic states of four atomic species (i.e., A, A^+∗, A2^+∗, A3+) participating in this process in the Russell-Saunders coupling. These tripartite states are readily characterized experimentally by measuring only energies of the three emitted electrons, without requiring any entanglement witness or other such protocols.