强流脉冲电子束轰击对单晶Si表面形貌的影响

用强流脉冲电子束技术对两种取向的单晶Si片进行了表面轰击,对电子束诱发的表面形貌进行了分析.实验结果表明,当能量密度～3 J/cm2时,轰击表面开始形成大量的熔坑.能量密度～4 J/cm2时,表面开始出现微裂纹,微裂纹的形态与单晶Si的晶体取向密切相关;强流脉冲电子束轰击能够诱发表层强烈的塑性变形,[111]取向单晶Si表面出现剪切带结构,而[001]取向单晶Si表面变形结构则以微条带为主;此外,变形区域内还出现大量<100 nm的微孔洞形貌,这些微孔洞的形成为制备表面多孔材料提供了可能.     

Ion bombardment induced changes in the optical and electrical properties of polycarbonate

The changes in the optical and electrical properties of polycarbonate (PC) films, bombarded with He and Ar ion beams, have been studied. The PC films were divided into two groups where the first group was bombarded with 130 keV He ions of fluences ranged from 1 × 10¹⁴ cm⁻² to 2 × 10¹⁶ cm⁻², while the second one was bombarded with 320 keV Ar of fluences (1 × 10¹³ cm⁻² and 1 × 10¹⁵ cm⁻²). The surface morphology of the unirradiated and irradiated PC films was studied using scanning electron microscopy (SEM) technique. The optical properties of the two groups have been carried out using UV-Vis spectrophotometer and the direct current (DC) electrical conductivity was also performed. The obtained results showed a decrease in the optical energy gap, the optical activation energy and the electrical activation energy with increasing the fluence of both He and Ar ions. Meanwhile, an increase in the DC conductivity was obtained with increasing the fluence of the ions. The bombardment of the PC films with He and Ar ion beams induced formation of carbon clusters near the polymer surface and, also, resulted in scission in the polymer chains.     

Ion bombardment induced surface electrical degradation monitoring by means of luminescence in aluminas

Oxide ceramics for use as electrical insulators in future fusion devices, will be exposed to ionization and displacement damage (neutrons, gammas, ion bombardment). Enhanced oxygen loss due to ion bombardment increases surface electrical conductivity, and at the same time the surface emits light due to ion beam induced luminescence (IBIL). Results for 3 types of α-alumina and sapphire measuring electrical surface conductivity and IBIL as a function of dose at different temperatures between 20 and 200 °C, show a clear correlation between luminescence and surface electrical degradation. This indicates the potential to remotely monitor insulating material degradation not only in ITER and beyond, but also in the more immediate in-reactor experiments required for materials testing. Partial reduction of degradation by heating in air suggests the possibility for in situ recovery of the insulating properties.     

Electron beam induced charging of Cu/MgO surfaces

The Auger beam surface charge build-up during deposition of thin layers of Cu upon MgO(100) and MgO(111) crystal surfaces was investigated. A three step model is proposed: 1) copper induced electron trapping, 2) formation of local conduction band in a thin metal film, and 3) formation of continuous isolated metal.     

Ion beam induced luminescence of polyethylene terephthalate foils under MeV H and He ion bombardment

The evolution of the ion beam induced luminescence (IBIL) of the polyethylene terephthalate (PET) foils was studied under the irradiation of H and He ions of MeV energy. The optical and chemical changes of the samples were also examined by photo-stimulated luminescence and optical absorption measurements after the irradiation. A prominent broad emission peak of IBIL appeared at around 380 nm, and its intensity monotonically decreased during the ion irradiation. The decay curves of the emission intensity were quantitatively explained as a function of the electronic energy deposition of the incident H and He ions. On the contrary, to the decrease of the main emission peak, a growth of new peaks was observed in the wavelengths between 500 and 600 nm.     

Ion angular distribution of species desorbed from single crystal surfaces by electron impact

The measurement of the angular distribution of desorbing positive ions produced by electron impact desorption (ESDIAD) is of fundamental importance in understanding molecular structure in the chemisorbed layer. In this short review, two applications of ESDIAD to structural problems in the adsorbed layer will be described. Examples of strong chemisorption and weaker physical adsorption effects will be discussed. In addition, interactions between adsorbed species, leading to changes in bonding geometry will be described. The apparatus used for this work allows digitized acquisition of ion angular distributions in the absence of background effects due to soft X-ray emission stimulated by electron impact.     

The angular distribution of particles sputtered from Cu,Zr, and Au surfaces by ion bombardment at grazing incidence

The angular distribution of particles sputtered from polycrystalline Cu, Zr, and Au targets has been measured for bombardment with Ar⁺- and Xe⁺-ions at perpendicular and grazing ion incidence (80° and 85° with respect to the surface normal). The ion energy was varied between 100 keV and 900 keV. The measured distributions follow approximately a cosine-squared curve rather than the cosine function, they are found to be symmetric with respect to the surface normal and almost independent of the ion species, the ion energy and the angle of incidence. Values of sputtering yield of Cu, Au and Zr are also presented.     

Ion channeling investigation of oxygen sublattice in YBa2Cu3O7 crystal film

The features of the oxygen sublattice in a crystal YBa₂Cu₃O₇ are investigated by channeling technique. It has been measured the angular dependence of resonant reaction yield of 3.055 MeV He⁺ ions channeled from oxygen nuclei along 〈0 0 1〉 direction. The best agreement of the calculated angular dependence of the reaction yield with experimental data is achieved with the assumption that the oxygen sublattice is partly disordered. About 20% of oxygen atoms are situated in the plane (1 1 0) randomly; the oxygen atoms in oxygen chains are displaced from crystal sites at ∼0.3 Å in the (1 1 0) plane.     

Analysis of the Auger neutralization of He at Cu surfaces in low energy ion scattering

Recently, strong crystal effects in P⁺ were observed for He⁺ and Cu in the Auger neutralization regime, with differences in the ion fraction by up to a factor of three non-equivalent Cu surfaces. In this contribution, it is shown that these findings can quantitatively be described within the jellium model assuming perpendicular velocity scaling of P⁺.     

Nanoscale self-affine surface smoothing by ion bombardment and the morphology of nanostructures grown on ion-bombarded surfaces

Surface smoothing by ion-bombardment with the concomitant formation of self-affine fractal surfaces at nanometer length scales is reviewed. Results of investigation of the dependence of surface smoothing on ion fluence and the threshold fluence for the formation of self-affine surfaces are presented. Finally, the morphology of self-assembled nanostructures grown by molecular beam epitaxy on surfaces of different fractal dimensions is investigated via studies of the roughness scaling exponent and the correlation length. While the self-assembled Ge islands grown on a pristine Si(1 0 0) surface are square or rectangular shaped, those on the ion-irradiated surface are nearly diamond-shaped.     

Ar离子辐照PET膜引起的表面结构和组分变化研究

用35MeV/u的Ar离子室温下辐照多层堆叠的半晶质的聚酯（PET）膜,采用X射线衍射技术和X射线光电子谱仪分析研究了辐照引起的表面结构和组分的变化。结果表明：Ar离子辐照PET膜引起了明显的非晶化转变和化学键断裂、断裂主要发生在甲氧基和羰基功能团上,并使这两个功能团中的C和O的比分相对减少。非晶化效应和化学键断裂同时依赖于离子的照射剂量和离子在样品表面的电子能量损失、剂量越高,表面电子能量损失越大,效应就明显。同时定性地讨论了结果。     

Growth of TiO2 surfaces following low energy (<40 eV) atom and small cluster bombardment

Low energy (10-40 eV) interaction of small Ti_xO_y clusters with a rutile (1 1 0) substrate was investigated using molecular dynamics with the aim of determining the influence of various parameters on surface growth and defect formation. Rutile growth was simulated through depositing randomly selected clusters with energies in the tens of eV range. Long time scale evolution was approximated through heating the substrate. A modified second-moment-Buckingham-QEq (SMB-Q) empirical potential was developed for the purpose. Crystal growth on amorphous and anatase TiO₂ substrates was also considered. Grown lattice layers were compared by visual inspection along with radial distribution function (RDF) plots. Bombardment at an energy of around 20 eV in an oxygen rich atmosphere with a high proportion of bombarding clusters, TiO, TiO₂, as opposed to single atoms, was found to produce rutile growth with the best crystallinity.     

Depth profiling study on the migration of tritium in titanium induced by deuterium-ion bombardment

A thin titanium layer with uniformly absorbed tritium (T/Ti ˜1.0) was bombarded by 390 keV D₃⁺ ions (130 keV per deuteron). Bombardment was performed at low (111 K) and room temperatures up to fluences of 5.9 × 10¹⁸ D/cm² and 3.0 × 10¹⁸ D/cm², respectively. Depth profiles of tritium up to a depth of 0.8 mg/cm² (˜1.8 μm) were measured and the change of the profile with fluence was investigated by means of the T(d, )n nuclear reaction. At both of the temperatures, a dip was formed on the depth profile of tritium at the depth around the projected range, indicating that the deuteron bombardment induced the migration of tritium against the concentration gradient. At the low temperature, the dip showed a gradual growth with fluence and saturation of the growth at the higher fluences, which could not be described by the existing model for isotope mixing. The spectrum of protons from the D(d, p)T reaction obtained in the same measurement suggested that the release of deuterium suddenly started at the final stage of the present bombardment. The dip formed at room temperature was larger than that at the low temperature. The migration of tritium induced by the bombardment is discussed on the basis of the experimental results obtained.     

Dose and microstructural effects on surface topography change and sputtering yield in polycrystalline molybdenum bombardment with 2 keV Ne+ions

The topographic change and sputtering yield in polycrystalline molybdenum due to the bombardment with normally incident 2 keV Ne⁺ ions have been investigated to study dose and microstructural effects at room temperature in three differently fabricated molybdenum samples. The surface topography changes with increasing dose and depends on the microstructure of the samples. The cones were formed at a dose above $\text{4 × 10}{}^{18}\text{ions/cm}{}^2$, and the number density and height of the cone increased with increasing dose. The distribution of cones was localized, and the aggregation of impurities including implanted neon atoms on cones was not observed. The sputtering yields in the three molybdenum samples were found to be the same value ($\text{0.90 ± 0.10}$) atoms/ion for 2 keV Ne⁺ ions, in spite of different surface topography changes caused by sputtering.     

Secondary electron emission from the entrance and exit surfaces of thin carbon foils under fast ion bombardment

The total secondary electron emission (SEE) yield from the entrance and exit surfaces of thin carbon foils under fast ion (¹⁶O, ¹⁹F, ³⁵Cl) bombardment has been measured as a function of the ion energy and the ion beam current intensity. Using a retarding field, the energy distribution of secondary electrons integrated over almost all angles of emission in the backward and forward directions has also been measured. It is found that total forward emission is larger than backward emission by factors of up to 2.5, 2.7 and 3.4 for ¹⁶O⁺³, ¹⁹F⁺³ and ³⁵Cl⁺⁵, respectively. It is suggested that the enhancement of forward SEE may be partly due to effects from the instantaneous charge state of the heavy ion beam in the solid in addition to the binary collisions of the projectile with individual electrons in the target. It is also shown that the total SEE yield from the entrance and exit surfaces of the target foils decreases with ion beam current intensity; this may be a beam-induced temperature effect. The total SEE yield in both the forward and backward directions is less sensitive to surface conditions for high velocity ions than for low velocity ions and the total yield from both surfaces of the foils is proportional to the ion stopping power in the target, where the constant of proportionality depends on the properties of material.     

Formation of thin silicon nitride layers on Si by low energy N2+ ion bombardment

The formation of nitride layers in silicon due to low-energy implantation of nitrogen in a wide range of ion bombardment parameters (energy E and angle of incidence θ) and for different temperatures of subsequent annealing (T) has been studied using Auger Electron Spectroscopy (AES), Secondary Ion Mass Spectrometry (SIMS) and Fourier Transform InfraRed Spectroscopy (FTIRS). Bombardment at angles θ < 40° produces an amorphous layer of stoichiometric Si₃N₄ the thickness of which depends on implantation energy and incidence angle. Annealing of the samples at 1000°C produces layers with rather sharp interfaces.     

应用同步辐射白光形貌术研究Nd:SGG晶体的缺陷

应用同步辐射X射线形貌术对坩埚下降法生长的Nd：SGG晶体的缺陷进行了研究。观察到该晶体中存在较为明显的镶嵌结构晶界缺陷和位错缺陷,并分析了上述缺陷的形成原因。对提高Nd：SGG晶体质量、改进生长工艺具有一定的参考价值。