[en] Adhesion of a 10-nm Au film on a Ta substrate is enhanced with 10-MeV Si ion irradiation at room temperature. The modifications of surface topography on a Au film are investigated by Scanning Tunneling Microscopy (STM). Surface craters and defects have been observed in this metal/metal system. It is shown that the higher the dose of ion irradiation, the higher the density and the bigger the size of the craters. The craters which are several nanometers in diameter extend from the surface into the interfacial region. A threshold dose at which the Au film can pass the Scotch tape test is determined, and the mechanism of the adhesion enhancement by ion bombardment is discussed

[en] Using vicinal Si(001) surfaces with a 4⁰ miscut angle towards the [110] direction as templates, an approach to fabricating well-aligned nanowires of Er silicide is demonstrated. At Er coverage of 0.1-0.3 nm and annealing temperature of 600-700 deg. C, ordered nanowires are obtained on the surface several hundreds of nanometres in length. STM images and LEED patterns reveal that the nanowires are all oriented along the [11-bar0] direction. The size, shape and density of the nanowires depends upon annealing temperature and duration as well as coverage. The experimental evidence also suggests a transition of bulk atomic structures between AlB₂ and ThSi₂ for Er silicide nanostructures. The alignment of the Er nanowires will make the measurements of their physical properties practicable

[en] Current-voltage electrical characteristics of Er silicide/Si(001) nanocontacts are measured in situ in a scanning tunneling microscopy system. Introduced as a new technique to suppress surface leakage conduction on Si(001), a silver wetting layer is evaporated onto the substrate surface kept at room temperature with ErSi ₂ nanoislands already existing. The effects of the silver layer on the current-voltage characteristics of nanocontacts are discussed. Our experimental results reveal that the silver layer at coverage of 0.4–0.7 monolayer can suppress effectively the current contribution from the surface conduction path. After the surface leakage path of nanocontacts is obstructed, the ideality factor and the Schottky barrier height are determined using the thermionic emission theory, about 2 and 0.5 eV, respectively. The approach adopted here could shed light on the intrinsic transport properties of metal-semiconductor nanocontacts. (paper)

[en] We report the diffusion behavior of dimer vacancies on a Si(100)-(2×1) surface by using ultrahigh-vacuum scanning tunneling microscopy. The dimer vacancies are created by oxygen etching of Si atoms at elevated temperatures. By annealing the sample at 600–750 °C, the dimer vacancies uniformly distribute on the terrace nucleate to form larger elongated voids of one atomic layer deep. The long axis of these voids is parallel to the Si dimer rows. During annealing, the surface morphology evolves in a way dominantly caused by the anisotropic diffusion of the dimer vacancies. A difference of diffusion barriers of 0.17±0.09eV is obtained between the [110] and [11-bar0] directions. (condensed matter: structure, mechanical and thermal properties)

[en] The turn-on time of ordinary thyristors is affected by the distribution parameters and the positive feedback process, and the turn-on time is longer. At the same time, due to the saturation of the internal transistors, the carriers in the three conductive regions accumulate, which results in a long carrier recombination time during turn-off, so the thyristor turn-off time is also very long. In order to solve the problem of slow speed of common thyristor switch, this paper designs an analog ultra-high-speed thyristor with thyristor characteristics. The analog ultra-high-speed thyristor is composed of fully discrete devices, using symmetric Baker anti-saturation clamp. The circuit clamps the tube voltage drop of both transistors to about 1.4V, and the transistor does not enter saturation, which greatly increases the switching time. The measured results show that the analog ultra-high-speed thyristor has an on-time of less than 30 ns and a turn-off time of less than 50 ns. The switching speed is about two orders of magnitude higher than that of the high-frequency thyristor, and provides an idea for the design of high speed power devices and the tube drop clamp of transistors. (paper)

[en] Erbium silicide nanowires are self-assembled on vicinal Si(001) substrates after electron beam evaporation and post annealing at 630°C In-situ scanning tunneling microscopy investigations manifest that the nanowires will successively shrink and transform into a nanoisland with annealing prolonged. Meanwhile, a structural transition from hexagonal AlB₂ phase to tetragonal ThSi₂ phase is revealed with high-resolution transmission electron microscopy. It is also found that the nanowires gradually expand to embed into the substrates during the growth process, which has much influence on the shape instability of nanowires. Additionally, a multiple deposition-annealing treatment is given as a novel growth method to strengthen the controlled fabrication of nanowires. (condensed matter: structure, mechanical and thermal properties)

[en] The morphology and crystalline structure of Er silicide nanocrystals self-assembled on the Si(001) substrate were investigated using scanning tunneling microscopy (STM) and transmission electron microscopy (TEM). It was found that the nanowires and nanorods formed at 630 deg. C has dominant hexagonal AlB₂-type structure, while inside the nanoislands self-organized at 800 deg. C the tetragonal ThSi₂-type structure is prevalent. The lattice analysis via cross-sectional high-resolution TEM demonstrated that internal misfit strain plays an important role in controlling the growth of nanocrystals. With the relaxation of strain, the nanoislands could evolve from a pyramid-like shape into a truncated-hut-like shape.

[en] Erbium silicide nanoislands on Si(001) surface are fabricated by novel multiple depositions and annealing treatments method. The morphological investigations determine that the islands could grow with stable square shapes rather than the shape transformation exhibited in the traditional single time evaporation growth. Size distributions analyses further elucidate the effect of multiple depositions and annealing treatments on the nanoisland growth. It is suggested that strain relaxation and static coalescence play important roles in the cyclic growth. Specifically, after 15 times of the cycles, the larger islands are found to undergo the Ostwald ripening, which make the shape of nanoislands irregular. This gives us the direction to adjust the growth parameters to control the island morphology. Furthermore, the crystalline structure of the Er silicide nanoislands is efficiently characterized by grazing incidence synchrotron x-ray diffraction

[en] In this work, an ultra-high vacuum scanning tunneling microscopy has been utilized to study the effects of Si atoms to the formation and growth evolution of Er silicide nanostructures. Si evaporation is performed on the vicinal Si(0 0 1) surface as well as Er growth under different growth conditions: growth procedure, annealing temperature and duration time. The experimental results show that the Si evaporation performed at a high temperature plays a key role on the growth of Er silicide nanostructures. The deposited Si atoms become a significant source of the Si reactant and mainly affect the early growth stage of the nanostructures. It is also shown that Er atom is possibly another diffusing species during the growth of Er silicide nanostructures on the Si(0 0 1) surface