Surface modifications by swift heavy-ion irradiation of indium phosphide

InP (001) samples were irradiated with 200 MeV Au ions at different fluences. The surface nanotopographical changes due to increasing fluence of swift heavy ions were observed by Atomic Force Microscopy (AFM), where the onset of a large increase in surface roughness for fluences sufficient to cause complete surface amorphization was observed. Transmission Electron Microscopy (TEM) was used to observe bulk-ion tracks that formed in InP, and high resolution TEM (HRTEM) revealed that single-ion tracks might not be amorphous in nature. Surface-ion tracks were observed by AFM in the form of ill-defined pits (hollows) of ~12 nm in diameter (width). In addition, Rutherford backscattering was utilized to follow the formation of disorder to amorphization in the irradiated material. The interpretation of the large increase in surface roughness with the onset of amorphization can be attributed to the plastic phenomena induced by the change of states from crystalline to amorphous by ion irradiation. The text was submitted by the authors in English.     

Structural modification of C60 films induced by 300-keY Xe-ion irradiation

The structural modification of C60 films induced by 300-keV Xe-ion irradiation was investigated. The irradiated C60 films were analysed using Fourier transform infrared spectroscopy, the Raman scattering technique, ultraviolet/visible spectrophotometry and atomic force microscopy. The analysis results indicate that the Xe-ion irradiation induces polymerization and damage of the C60 molecule and significantly modifies the surface morphology and the optical property of the C60 films. The damage cross-section for the C60 molecule was also evaluated.     

Softening of phonon modes in C60 crystals induced by laser irradiation: Thermal effects

Reversible softening of the intramolecular A _g(2) pentagonal pinch (PP) mode of a C₆₀ single crystal in the face centered cubic phase has been studied as a function of laser power density by means of Raman scattering. The average temperature rise in the laser excitation spot has been determined using the Stokes to anti-Stokes integrated peak intensity ratio for the H _g(1) phonon mode. Softening of the PP-mode was found to be due to heating of the sample resulting from laser irradiation, in good quantitative agreement with experimental results obtained for uniformly heated samples. These findings are in excellent agreement with results obtained by numerical calculations of the local temperature distribution and average temperature in the laser spot based on calculated integrated intensities of the Stokes and anti-Stokes bands of the PP-mode. These calculations were based on experimental data for the temperature dependence of phonon frequency and width, absorbance, and thermal conductivity in solid C₆₀. Zh. éksp. Teor. Fiz. 114, 1785–1794 (November 1998) Published in English in the original Russian journal. Reproduced here with stylistic changes by the Translation Editor     

Thermal processes in multilayer second-generation HTSC under swift heavy-ion irradiation

On the basis of the thermal spike model, the estimations with regard to tapes of the second-generation Ag/YBaCuO/MgO/Hastelloy HTSC under irradiation with Ar, Kr, and Xe ions of an energy of about 1.2 MeV/amu have been carried out. The results have been compared with the available experimental data. In addition, the possibility of processes such as melting, recrystallization, amorphization, and other phase transitions in multilayer structures under ion irradiation has been studied.     

Effect of ion irradiation on C 60 thin films

We report a new effect of ion irradiation on C₆₀ thin films: C₆₀ thin films irradiated with 7-MeV C²⁺ ions show resistance to photopolymerization. The resistance increases with increasing ion fluence of irradiation. The effect is qualitatively explained by the fact that the number of a C₆₀ pair satisfying the topochemical requirement for photochemical reaction in solids decreases by destruction of C₆₀ molecules accompanied by lattice disorder.     

Influence of light-ion irradiation on the heavy-ion track etching of polycarbonate

We report on the effect of light-ion irradiation on the size distribution of etched tracks produced by medium energy heavy-ions in polycarbonate. Makrofol KG polycarbonate foils were treated with 2 MeV H⁺ ions at different fluences φ either before or after a short irradiation with 18 MeV Au⁷⁺. The heavy ion irradiation was used to produce the latent tracks in the foils and the proton beam acted as a perturbation to the matrix. The proton irradiation causes initially a decrease in the mean etched pore size, as compared to samples only bombarded by Au ions, reaching a minimum at H⁺ fluences around 2–5×10¹³ cm⁻², while at higher φ the pore size starts to grow again. This effect is attributed to the action of two competitive processes that dominate in different fluence regimes. The decrease in the pore radii at low fluences is attributed to an increase in crystallinity induced by the proton beam. As the total dose builds up, this effect is surpassed by chain scission and amorphization that grow at a lower rate and cause the pore radii to increase again.     

Role of thermodynamics in the shape transformation of embedded metal nanoparticles induced by swift heavy-ion irradiation

Swift heavy-ion irradiation of elemental metal nanoparticles (NPs) embedded in amorphous SiO(2) induces a spherical to rodlike shape transformation with the direction of NP elongation aligned to that of the incident ion. Large, once-spherical NPs become progressively more rodlike while small NPs below a critical diameter do not elongate but dissolve in the matrix. We examine this shape transformation for ten metals under a common irradiation condition to achieve mechanistic insight into the transformation process. Subtle differences are apparent including the saturation of the elongated NP width at a minimum sustainable, metal-specific value. Elongated NPs of lesser width are unstable and subject to vaporization. Furthermore, we demonstrate the elongation process is governed by the formation of a molten ion-track in amorphous SiO(2) such that upon saturation the elongated NP width never exceeds the molten ion-track diameter.     

Effect of electron irradiation on the spectra of elementary excitations in C60 fullerite

Electron irradiation produces changes in the spectra of elementary excitations of C₆₀ fullerite, which are manifested by decrease in the π-plasmon energy, bandgap width, and energies of the HOMO-LUMO and other molecular transitions, smoothening of the corresponding spectral features, and significant growth in the quasicontinuous low-energy background intensity, the latter being indicative of an increase in the conductivity. The observed “red shifts” are related to collectivization of a part of the π electrons, the formation of chemical bonds between adjacent molecules (polymerization), and the corresponding increase in the proportion of sp ³-hybridized electrons. Characteristic electron energy loss (EEL) spectra of an intact fullerite sample non-perturbed by the polymerization process were measured. The EEL spectra of fullerite exhibit a multipole structure due to the (σ + π)-plasmon and reveal an exciton feature which is highly sensitive with respect to electron irradiation and can be used to characterize the initial fullerite structure and to indicate the polymerization onset.     

Single event effect in a ferroelectric-gate field-effect transistor under heavy-ion irradiation

The single event effect in ferroelectric-gate field-effect transistor （FeFET） under heavy ion irradiation is investigated in this paper. The simulation results show that the transient responses are much lower in a FeFET than in a conventional metal-oxide-semiconductor field-effect transistor （MOSFET） when the ion strikes the channel. The main reason is that the polarization-induced charges （the polarization direction here is away from the silicon surface） bring a negative surface po- tential which will affect the distribution of carders and charge collection in different electrodes significantly. The simulation results are expected to explain that the FeFET has a relatively good immunity to single event effect.     

C60、C60F60及C60H60“分子滚珠”的压缩特性与电子结构

采用量子分子动力学技术,模拟了C60、C60F60与C60H60分子的压缩过程,计算了这些"分子滚珠"受压变形后的电子结构.根据计算结果,对比、分析了三种分子的压缩力学特性以及压缩变形对其电子结构的影响.研究表明,1)三种分子的抗压缩载荷与能量吸收能力有C60F60＞C60H60＞C60的排序,但抗变形能力相当;2)随着压缩变形的增大,三种分子的化学活性增加,但相同应变下,C60F60和C60H60分子有着比C60更好的化学稳定性.     

Influence of neutron and heavy-ion irradiation on EPR spectra of CuGeO3

The influence of neutron and heavy-ion irradiation on the electron paramagnetic resonance (EPR) spectra of the spin-Peierls compound CuGeO₃ has been investigated in the wide temperature range of 2–300 K. It is found that the neutron irradiation leads to a decrease of the spin-Peierls transition temperature and induces appreciable changes in the EPR signal intensity, resonance line width andg-factor of this material. These changes may be associated with a partial suppression of both the energy gap and dimerization within the Cu chains due to the irradiation-induced changes in the topological and chemical short-range order. In contrast to this, the heavy-ion irradiation induces only an increase in the intensity of the EPR signal and does not produce appreciable changes in the resonance line width,g-factor and spin-Peierls transition temperature. The experimental results show a large increase in the Curie-Weiss component and complete suppression of the spin-Peierls transition for higher irradiation doses.     

Changes in magnetic properties induced by heavy-ion irradiation in magnetic insulators as seen by Mössbauer spectroscopy

Summary The high-energy heavy-ion irradiation of magnetic materials induces not only amorphous matter in the ion tracks but also improvement or even creation of new magnetic properties in a stressed shell surrounding the track core. Two examples are presented in this paper: magnetization creation in the spinel ZnFe₂O₄ after Kr, Xe and Pb irradiations and trapping of magnetic domains in another spinel, the magnetite Fe₃O₄, after lead irradiation. Paper presented at the ICAME-95, Rimini, 10–16 September 1995.     

The oxidation of fullerene[C60] with various amine N-oxides under ultrasonic irradiation

The reaction of C60 with various amine N-oxides such as 3-picoline N-oxide (Aldrich 98.0%), pyridine N-oxide hydrate (Aldrich 95.0%), quinoline N-oxide (Aldrich 97.0%), isoquinoline N-oxide (Aldrich 98.0%) under ultrasonic irradiation in air at 25-43 degrees C causes the oxidation of fullerene[C60(O)n] (n=1-2 or n=1). The MALDI-TOF MS, UV-vis spectra, and HPLC profile confirmed that the products of fullerene oxidation are [C60(O)n] (n=1-2 or n=1).     

紫外激光和压力共同作用下C60-peapod的聚合相变研究

采用气相扩散方法将C60分子填充到单壁碳纳米管(SWNTs)中,制备出高填充比率的豆荚形纳米材料C60@SWNT,又称为peapod.用金刚石对顶砧(DAC)装置获得高压,在高压下同时利用紫外激光处理样品,通过激光和压力的共同作用研究了C60分子在碳管内的聚合相变.在21.5 Gpa高压下,同时紫外激光(325 nm)照射30 min后,拉曼光谱表明C60分子在碳管内发生了聚合,形成一维链状O相聚合结构,且该相变是不可逆的.紫外激光的引入使样品发生O相聚合所需的压力值低于仅由压力诱导的聚合压力.