Ar+ ion beam induced silicide formation mechanism at the Pd-Si interface

Evaporated palladium films of 45 nm thickness on Si(1 1 1) were irradiated using 78 keV Ar⁺ ions with doses in the range of 1×10¹⁵ to 1.5×10¹⁶ cm^–2 for the purpose of studying silicide formation. Rutherford backscattering analysis shows that intermixing has occurred across the Pd-Si interface at room temperature. The mixing behaviour increases with increasing dose of the bombarding ions, which agrees well with a theoretical model of isotropic cascade mixing for palladium, and radiation-enhanced diffusion associated with an interstitial mechanism for silicon.     

Interdiffusion and phase formation at room temperature in evaporated gold-tin films

Interdiffusion at room temperature in evaporated Au-Sn films was studied by the in situ backscattering of 2.0 MeV ⁴He ions. The interdiffusion resulted in the formation and growth of an AuSn phase region. The growth of the phase followed a parabolic growth rate law, and the growth rate constant was found to be about 9 × 10^?15 cm²s^?1 at room temperature.     

Spontaneous phase and morphology transformations of anodized titania nanotubes induced by water at room temperature

We report a spontaneous phase transformation of titania nanotubes induced by water at room temperature, which enables the as-anodized amorphous nanotubes to be crystallized into anatase mesoporous nanowires without any other post-treatments. These mesoporous TiO(2) nanomaterials have a markedly improved surface area, about 5.5 times than that of the as-anodized TiO(2) nanotubes, resulting in a pronounced enhanced photocatalytic activity. The present approach not only allows a flexible control over the morphology of TiO(2) nanostructures but can fundamentally eliminate the need for high temperature operations for crystallizing amorphous TiO(2).     

Deposition of copper sulfide hollow nanospheres in aqueous solution at room temperature

Uniform copper sulfide hollow nanospheres were obtained in high yield by reacting copper nitrate with thioacetamide in water at room temperature under the assistance of sodium dodecyl sulfate (SDS). The spheres (average diameter of ca. 200 nm) displayed big cavity while their surface were constructed by randomly stacked nanoflakes. The products were characterized by X-ray diffraction (XRD), energy-dispersive X-ray spectrometry (EDX), field-emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). SDS was found to play a key role in the synthesis process while a four-step mechanism was proposed to explain the formation of hollow nanospheres. The influence of SDS concentration on the size and shape of the product has also been investigated in detail.     

Low-energy Ar ion-beam induced vanadium silicide formation at V/Si interfaces

Vanadium/silicon interfaces produced by V thin film deposition on Si substrates were ion-beam mixed using 2 and 3 keV Ar⁺ ions at room temperature. The ion-beam mixing (IBM) has been studied by means of X-ray photoelectron spectroscopy, factor analysis and TRIDYN simulations. Comparison of the experimental results with those obtained from TRIDYN simulations suggests that, in addition to pure ballistic ion mixing mechanisms, other radiation-enhanced diffusion processes could contribute to the IBM of V/Si interfaces by low-energy Ar⁺ bombardment at room temperature. The kinetics of interface formation by IBM is characterized by two stages. During the first stage, a strong decrease of metallic V species is observed due not only to sputtering but also to the formation of vanadium silicide. The concentration of vanadium silicide related species reaches a maximum at the end of this first stage, decreasing subsequently. Finally, with increasing sputtering time, the signals associated with the silicide slowly decrease, and pure silicon species begin to appear, since no free metallic vanadium atoms are available to react with the unlimited silicon supply from the substrate.     

Abnormal structure of titanium formed by ion beam sputtering at room temperature

Stable fcc modification of titanium (a=0.420 nm) has been observed in ion beam sputtered films at room temperature. When the deposition rates are above 0.8 Å/s, the normal hcp structure is obtained.     

Coordination-induced formation of nanobelts of organic-inorganic hybrid materials at room temperature

The unexpected finding that the direct mix of o-phenylenediamine and H₂PdCl₄ aqueous solution at room temperature leads to supramolecular nanobelts of coordination polymers was reported. The morphology of the structures was characterized by scanning electron microscopy (SEM) and the chemical composition was examined by energy-dispersed spectrum (EDS) and X-ray maps analysis. The possible formation process of such supramolecular nanobelts is given and the influence of the molar ratio of reactants on the formation of these nanobelts is also examined. It is also found that the molar ratio of reactants has strong influence on the formation of the supramolecular structures.     

Electrical characteristics of mixed Zr-Si oxide thin films prepared by ion beam induced chemical vapor deposition at room temperature

Mixed Zr-Si oxide thin films have been prepared at room temperature by ion beam decomposition of organometallic volatile precursors. The films were flat and amorphous. They did not present phase segregation of the pure single oxides. A significant amount of impurities (-C-, -CH_x, -OH, and other radicals coming from partially decomposed precursors) remained incorporated in the films after the deposition process. This effect is minimized if the Ar content in the O₂/Ar bombarding gas is maximized. Static permittivity and breakdown electrical field of the films were determined by capacitance-voltage and current-voltage electrical measurements. It is found that the static permittivity increases non-linearly from ~ 4 for pure SiO₂ to ~ 15 for pure ZrO₂. Most of the dielectric failures in the films were due to extrinsic breakdown failures. The maximum breakdown electrical field decreases from ~ 10.5 MV/cm for pure SiO₂ to ~ 45 MV/cm for pure ZrO₂. These characteristics are justified by high impurity content of the thin films. In addition, the analysis of the conduction mechanisms in the formed dielectrics is consistent to Schottky and Poole-Frenkel emission for low and high electric fields applied, respectively.     

Electrical control of the ferromagnetic phase transition in cobalt at room temperature

Electrical control of magnetic properties is crucial for device applications in the field of spintronics. Although the magnetic coercivity or anisotropy has been successfully controlled electrically in metals as well as in semiconductors, the electrical control of Curie temperature has been realized only in semiconductors at low temperature. Here, we demonstrate the room-temperature electrical control of the ferromagnetic phase transition in cobalt, one of the most representative transition-metal ferromagnets. Solid-state field effect devices consisting of a ultrathin cobalt film covered by a dielectric layer and a gate electrode were fabricated. We prove that the Curie temperature of cobalt can be changed by up to 12 K by applying a gate electric field of about ±2 MV cm(-1). The two-dimensionality of the cobalt film may be relevant to our observations. The demonstrated electric field effect in the ferromagnetic metal at room temperature is a significant step towards realizing future low-power magnetic applications.     

Precursor compound enabled formation of aqueous-phase CdSe magic-size clusters at room temperature

The formation pathway of aqueous-phase colloidal semiconductor magic-size clusters(MSCs)remains unrevealed.In the present work,we demonstrate,for the first time...     

CuO nanostructures on copper foil by a simple wet chemical route at room temperature

Uniform CuO nanostructures have been synthesized on copper foil substrates by oxidation of Cu in alkaline condition by a simple wet chemical route at room temperature. By controlling the alkaline condition (pH value) different CuO nanostructures like nanoneedles, self-assembled nanoflowers and staking of flake-like structures were achieved. The phase formation and the composition of the films were characterized by X-ray diffraction and energy dispersive analysis of X-ray studies. X-ray photoelectron spectroscopic studies indicated that the samples were composed of CuO. The morphologies of the films were investigated by scanning electron microscopy. A possible growth mechanism is also proposed here. Band gap energies of the nanostructures were determined from the optical reflectance spectra. The different CuO nanostructures showed good electron field emission properties with turn-on fields in the range 6-11.3 V μm⁻¹. The field emission current was significantly affected by the morphologies of the CuO films.     

四方相纳米氧化锆低温稳定机制的研究现状

介绍了近几十年t-ZrO2纳米晶在室温下稳定机制的研究现状,并且重点分析表面能理论和氧空位理论等主要机制,在此基础上对镀膜、水蒸气、杂质离子、形核位置以及结构相似对其稳定性的影响进行进一步的讨论.     

Ion-assisted deposition of oxide materials at room temperature by use of different ion sources

Thin films of SiO(2), TiO(2), Ta(2)O(5), ZrO(2), and the mixed oxide H4 (Merck) have been deposited onto nonheated glass substrates by electron-beam evaporation in commercial coating plants. All depositions have been carried out with ion assistance provided by three different ion or plasma sources (end-hall, plasma, and cold-cathode sources). The optical film properties such as index of refraction, extinction coefficient, light scattering, and absorption have been examined by spectrophotometry, laser calorimetry, and total integrated light-scatter measurements. Surface morphology has been investigated by atomic force microscopy studies. Furthermore, films have undergone sand erosion tests for the determination of relative wear resistance. The film properties are compared for the three different ion sources.     

Ilmenite phase nickel titanate nanowhiskers as highly sensitive LPG sensor at room temperature

The NiTiO₃ nanoparticles with ilmenite phase were synthesized by the sol gel method and investigated for sensing of various volatile organic compounds. The resistive type sensing by NiTiO₃ towards LPG was not reported earlier where the sensor showed fair response towards hydrogen sulfide gas, but the sensitivity towards LPG was very high. The response % for 150 ppm of LPG was approximately 3200% at room temperature. The high response towards LPG was due to the presence of some amount of rutile TiO₂ in the composites. The response and recovery times of these sensors were very less (about 2 s) which could be attributed to the whiskers like structure of NiTiO₃.     

Effects of carbon readsorption on tungsten under high-flux, low-energy Ar ion irradiation at elevated temperature

The erosion kinetics under irradiation by Ar ions extracted from plasma by 300 V negative bias voltage of 2 μm-thick W film contaminated by redeposited carbon atoms was investigated in dependence on the Ar-working gas pressure in the range 0.2-10 Pa at 410 K. The erosion and deposition parameters were deduced from the dependence of the sample's weight change on irradiation time. Two regimes were distinguished which contributed differently to the carbon transport efficiency from the surface towards the bulk, namely, the weight-decrease regime, when sputtering prevailed redeposition, and the weight-increase regime, when redeposition prevailed sputtering. Carbon distribution profiles measured by the SIMS technique showed that carbon was efficiently transported into the W film when its surface was not covered by a continuous amorphous C layer. The C transport efficiency decreased when W was covered by a continuous amorphous C film.These results were qualitatively explained by dynamic mixing of atoms on the surface. It was assumed that surface chemical potential increased under irradiation and that C adatoms were driven into grain boundaries of nanocrystalline W film. The continuous amorphous C film on tungsten blocked the access of activated C atoms to the grain boundaries.     

Divacancies at room temperature in germanium

We have studied the annealing of vacancy defects in neutron and proton irradiated germanium. After neutron irradiation the Sb-doped samples were annealed at 473, 673 and 773 K for 30 min. The positron lifetime was measured as a function of temperature (30 - 295 K). A lifetime component of 330 ps with no temperature dependence is observed in as irradiated samples, identified as the positron lifetime in a neutral divacancy. The average positron lifetime in the samples annealed at 473 K has a definite temperature dependence, suggesting that the divacancies become negative as the crystal recovers and the Fermi level moves upward in the band gap. Proton irradiation of germanium at 37 K with subsequent room temperature annealing also resulted in a similar lifetime component 315 ps, in good agreement with the neutron irradiation experiment.     

Silicide formation by Ar+ ion bombardment of Pd/Si

Palladium films, 45 nm thick, evaporated on to Si(111) were irradiated to various doses with 78 keV Ar⁺ ions to promote silicide formation. Rutherford backscattering spectroscopy (RBS) shows that intermixing has occurred across the Pd/Si interface at room temperature. The mixing behaviour is increased with dose which coincides well with the theoretical model of cascade mixing. The absence of deep RBS tails for palladium and the small area of this for silicon spectra indicate that short-range mixing occurs. From the calculated damage profiles computed with TRIM code, the dominant diffusion species is found to be silicon atoms in the Pd/Si system. It is also found that the initial compound formed by Ar⁺ irradiation is Pd₂Si which increases with dose. At a dose of 1×10¹⁶ Ar⁺ cm^–2, a 48 nm thickness of Pd₂Si was formed by ion-beam mixing at room temperature.     

掺铁氧化锌室温磁性半导体

采用溶胶-凝胶法制备了Zn0.98Fe0.02O块材样品,利用XRD检测了样品的结构.结果表明样品具有ZnO的六角结构,并且只有ZnO的衍射峰出现,没有Fe或Fe的化合物等杂相存在,说明样品只包含单相ZnO.结果还进一步说明掺杂的部分Fe替代了部分Zn的位置.利用VSM所作的分析测量表明,样品是铁磁性的,且居里温度高于室温.