高能Ar离子辐照PET膜引起的表面改性研究

采用傅立叶转换的红外光吸收技术在反射方式下分析研究了35MeV/u Ar离子辐照半晶质PET膜引起的表面改性及其对吸收剂量的依赖性。结果表明，辐照导致PET膜中与晶态区域相关的吸收带强度随吸收剂量增加普遍减弱，而与非晶区域相关的吸收带强度随吸收剂量增加逐渐增加，表明辐照使PET膜发生了非晶化转变。化学键断裂主要发生在苯环的对位和酯的C－O键上，而苯环的基本结构在整个辐照过程中变化较小。非晶化效应和化学键断裂同时依赖于离子的照射剂量和样品表面的电子能量沉积。此外，在约5．0MGy以上的吸收剂量，辐照还引起了炔端基团的形成，炔端基团浓度随吸收剂量的增加显著增加。对实验结果进行了定性解释。     

Ar16+与Zr作用产生的X射线谱

本工作对超导离子源(SECRAL)上的10～20 kV/q Ar16 和Ar17 入射到金属Zr表面进行实验研究.实验结果表明,高电荷态Ar16 在金属表面存在着多电子激发过程.Ar空心原子的K层发射X射线强度随入射离子的动能减少,靶原子Zr的L壳层发射X射线强度随入射离子动能的增加而增强.Ar17 单离子的Kα-X射线产额比Ar16 单离子的Kα-X射线产额大5个数量级.     

同步辐射软X射线对单细胞的辐射损伤

应用国家同步辐射实验室软X射线显微术光束线的光学系统,搭建了适合软X射线单细胞辐照损伤效应研究的实验装置,选择氧元素K吸收边能量对Hela细胞进行单细胞辐照,运用单细胞凝胶电泳技术进行辐照损伤评价.实验结果表明,辐射损伤效应与辐射剂量有依赖性关系.     

高能氩离子在钇铁柘榴石中引起的非晶化研究(英文)

用倾斜样品X-射线衍射学(STD)和饱和磁化强度测量,研究了960MeV氩离子低温(195K)辐照多晶钇铁柘榴石Y_3Fe_5O_(12)(YIG)所引起的非晶化过程。分析结果表明,960MeV氩离子引起YIG晶态→非晶态转变是一个逐步的过程,在这个过程中电子能损起主导作用,但也需要一定的辐照剂量。并在辐照剂量0≥1×10~(14)Ar/cm~2时,在电子能损S_e=8.3MeV处,首次观察到了几乎完全的非晶态。     

Kovar封装CMOS器件X射线剂量增强效应研究

在器件的金属化层及封装等结构中，高原子序数材料在低能X射线的辐照下，会在相邻的低原子序数材料中产生剂量增强效应，从而使得器件性能严重退化。主要介绍了柯伐封装的CMOS器件，在X射线和γ射线辐照下，其辐照敏感参数阈值电压和漏电流随总剂量的变化关系。并对实验结果进行了比较，得出低能X射线辐照对器件损伤程度大于γ射线，对剂量增强效应进行了有益的探讨。     

电子束辐照PET薄膜制备有序多孔阵列高分子模板

本文用掩膜工艺电子束蚀刻技术产生具有潜影的聚酯(PET)薄膜,经强氧化液(浓硫酸与重铬酸钾的混合液)腐蚀,产生有序微米多孔阵列PET模板.讨论了辐照剂量、腐蚀时间以及腐蚀温度等因素对基膜蚀刻和腐蚀的影响.结果表明:随着辐照剂量、腐蚀温度和腐蚀时间的增加,PET基膜更易被腐蚀.IR、DSC测量结果表明:辐照导致化学键的断裂、非晶化转变,是导致辐照PET薄膜的腐蚀失重率增加的原因.用此方法制备了孔径大小一致的微米级有序多孔阵列PET模板.     

CMOS器件X 射线与γ射线辐照效应比较

介绍了低能X射线和γ射线的辐照剂量及器件阈电压漂移的测试方法。讨论了不同偏置条件和辐照方向对器件效应的影响。结果表明,对镀金Kovar合金封装的器件,在背向辐照的最劣辐照偏置下,X射线产生的阈电压漂移是^60Coγ射线的13.4倍。     

同步辐射软X射线引起小麦根尖细胞凋亡的研究

采用不同剂量的软X射线辐照小麦种子,利用DAPI荧光染色和TUNEL原位标记对种子萌发后的根尖细胞进行细胞凋亡的检测。结果表明,在剂量为0-288J／cm^2范围内的软X射线辐照能引起小麦根尖细胞的凋亡现象（如细胞形态学变化及细胞核内DNA的断裂等）发生,细胞凋亡率与同步辐射软X射线辐照剂量呈正相关性。     

单细胞凝胶电泳法检测研究同步辐射软X射线辐照引起的DNA损伤

本实验采用单细胞凝胶电泳方法定量检测了不同辐照剂量的同步辐射软X射线对小麦根尖细胞造成的DNA单链损伤.通过测定核DNA的迁移效应表明,在剂量为0-288 J·cm-2范围内的软X射线辐照下,有20%-92%的小麦根尖细胞产生了DNA单链的损伤效应,同时DNA的损伤程度也与辐照剂量呈显著正相关.     

高电荷态离子Ar13+轰击Mo金属表面形成靶原子X射线谱测量

本工作实验研究低能高电荷态Ar¹³⁺离子与金属Mo表面作用过程中Mo原子受激发射X射线和X射线强度随入射能量的变化。实验结果表明，低速高电荷离子与金属表面原子相互作用可有效地激发靶原子或靶离子内壳层电子而发射X射线。     

Swift heavy ion irradiation induced modification of the microstructure of NiO thin films

NiO nanoparticle films (200 nm thick) grown on Si substrates by pulsed laser deposition method were irradiated by 200 MeV Ag¹⁵⁺ ions. The films were characterized by glancing angle X-ray diffraction, atomic force microscopy and optical absorption spectroscopy. Though electronic energy loss of 200 MeV Ag ions in NiO matrix was higher than the threshold electronic energy loss for creation of columnar defects, films remained crystalline with the initial fcc structure even up to a fluence of 5 × 10¹³ ions cm⁻², where ion tracks are expected to overlap. Irradiation however modified the microstructure of the NiO films considerably. The grain size decreased with increasing ion fluence, which led to reduced surface roughness and increased optical band gap due to quantum confinement. These results correlate well with variation of the power spectral density exponent with ion fluence, which indicate that at high ion fluences, the evolution of surface morphology is governed by surface diffusion.     

Velocity effect of swift heavy ions in graphite studied by Raman spectroscopy

Highly oriented pyrolytic graphite (HOPG) samples were irradiated with swift heavy ions (Ar, Kr, Bi, U) of fluences between 10¹¹ and 10¹³ ions/cm² in energy range MeV-GeV. The irradiated samples were analyzed by Raman spectroscopy with laser wavelength of 532.2 nm. It is shown that the ratio between the integrated intensities of the disorder-induced D and the original G Raman bands which denotes the degree of the damage induced by ion irradiation increases as a function of ion fluence as well as the electronic energy loss. This agrees with the previous reports. However, quantitative analysis of the peak intensity at a fixed fluence discloses that ion velocity is also a significant parameter in determination of damage. The conclusion is that the extent of discontinuity of ion track may change with ion velocity besides the electronic energy loss. Considering the radial distribution of the energy deposited on the matter being velocity dependent, the energy density which combines the influence of the electronic energy loss and ion velocity may be more suitable for explaining the effect induced by swift heavy ions.     

Structural characterization of swift heavy ion irradiated polycarbonate

Makrofol-N polycarbonate thin films were irradiated with copper (50 MeV) and nickel (86 MeV) ions. The modified films were analyzed by UV-VIS, FTIR and XRD techniques. The experimental data was used to evaluate the formation of chromophore groups (conjugated system of bonds), degradation cross-section of the special functional groups, the alkyne formation and the amorphization cross-section. The investigation of UV-VIS spectra shows that the formation of chromophore groups is reduced at larger wavelength, however its value increases with the increase of ion fluence. Degradation cross-section for the different chemical groups present in the polycarbonate chains was evaluated from the FTIR data. It was found that there was an increase of degradation cross-section of chemical groups with the increase of electronic energy loss in polycarbonate. The alkyne and alkene groups were found to be induced due to swift heavy ion irradiation in polycarbonate. The radii of the alkyne production of about 2.74 and 2.90 nm were deduced for nickel (86 MeV) and copper (50 MeV) ions respectively. XRD analysis shows the decrease of the main XRD peak intensity. Progressive amorphization process of Makrofol-N with increasing fluence was traced by XRD measurements.     

The effect of MeV ion irradiation on the hydrogen content and resistivity of direct ion beam deposited diamondlike carbon

Diamondlike carbon films fabricated by direct ion beam deposition have been irradiated with 6.4 MeV fluorine and 1 MeV gold ions. Both beams reduce the hydrogen content with the fluorine beam being much more efficient than the gold beam. The resistivity of the materials is also reduced by both beams with the fluorine beam producing a much larger drop in resistivity and a lower fluence than the gold beam. It is concluded that defects produced by electronic energy loss of the bombarding ions are responsible for both the loss of hydrogen and the change in resistivity. The magnitude of both of these effects is reduced with increasing ion mass as the proportion of nuclear to electronic energy loss is increased. This is due to the production of retrapping centers in the case of hydrogen and ion induced annealing in the case of resistivity. There is a threshold in fluence for both effects and this may be associated with fluctuations in the rate of deposition of the electronic energy loss along an individual ion track.     

Color center formation in silica glass induced by high energy Fe and Xe ions

Silica glass samples were implanted with 1.157 GeV ⁵⁶Fe and 1.755 GeV ¹³⁶Xe ions to fluences range from 1 × 10¹¹ to 3.8 × 10¹² ions/cm². Virgin and irradiated samples were investigated by ultraviolet (UV) absorption from 3 to 6.4 eV and photoluminescence (PL) spectroscopy. The UV absorption investigation reveals the presence of various color centers (E′ center, non-bridging oxygen hole center (NBOHC) and ODC(II)) appearing in the irradiated samples. It is found that the concentration of all color centers increase with the increase of fluence and tend to saturation at high fluence. Furthermore the concentration of E′ center and that of NBOHC is approximately equal and both scale better with the energy deposition through processes of electronic stopping, indicating that E′ center and NBOHC are mainly produced simultaneously from the scission of strained Si-O-Si bond by electronic excitation effects in heavy ion irradiated silica glass. The PL measurement shows three emissions peaked at about 4.28 eV (α band), 3.2 eV (β band) and 2.67 eV (γ band) when excited at 5 eV. The intensities of α and γ bands increase with the increase of fluence and tend to saturation at high fluence. The intensity of β band is at its maximum in virgin silica glass and it is reduced on increasing the ions fluence. It is further confirmed that nuclear energy loss processes determine the production of α and γ bands and electronic energy loss processes determine the bleaching of β band in heavy ion irradiated silica glass.     

Low temperature resistivity study of nanostructured polypyrrole films under electronic excitations

The synthesis of nanostructured polypyrrole (Ppy) films by electrochemical process and their modifications by electronic excitations induced by swift heavy ion irradiations is reported in this paper. The electrical property of ion beam irradiated polypyrrole was investigated at low temperature by resistivity measurements. The structural and optical properties were also studied using X-ray diffraction (XRD), UV-vis spectroscopy and scanning electron microscopy (SEM). At low temperature, the polypyrrole films show the metallic behaviour after ion beam irradiation. UV-vis spectroscopy shows a red shift in the absorbance edge and thus reduction in band gap with increasing ion fluence. The structural studies show that the percentage crystallinity improves with increase in ion fluence. The SEM study corroborates the results of structural analysis and shows the formation of rod type structures along with the evolution of amorphous phase with increasing ion fluence.     

Atomic force microscopy and Raman scattering studies of femtosecond laser-induced nanohillocks on CR-39

The phenomenon of nanohillock-like defect formation on the surfaces of CR-39 by ultra-short laser irradiation is investigated using an Atomic Force Microscope (AFM) and Raman Scattering. A polymer CR-39 target was exposed to Ti:sapphire 25-fs laser pulses with a central wavelength at 800 nm. Samples were irradiated for different laser fluences both in air and vacuum. Detailed surface topographical features of the bombarded samples were characterized by atomic force microscopy in contact mode in air at room temperature. AFM reveals that the growth of nanohillocks and their features are strongly dependent on the ambient condition, target position from focus, and irradiation fluence. The appearance of these nanohillocks in the range 1–20 nm in height and 10–90 nm in diameter are regarded as typical features for fast electronic processes (correlated with existence of hot electrons) and are explained on the basis of Coulomb explosion. These nanostructures due to localization of laser energy deposition in small areas provide a possible pathway from dense electronic excitation to atomic motion causing permanent structural modification which are well correlated to structural alterations, like crosslinking and chain scissions, inferred from Raman spectroscopy.     

Sputtering and crystalline structure modification of bismuth thin films deposited onto silicon substrates under the impact of 20-160 keV Ar ions

The sputtering of bismuth thin films induced by 20-160 keV Ar⁺ ions has been studied using Rutherford backscattering spectrometry, scanning electron microscopy and X-ray energy dispersive and diffraction spectroscopy. These techniques revealed increasing modifications of the Bi film surfaces with increasing both ion beam energy and fluence up to their complete deterioration under irradiation conditions E = 160 keV and φ = 1.5 × 10¹⁶ cm⁻², leaving isolated islands of preferred (0 1 2) orientation on the Si substrate. The observed surface morphology and crystalline structure evolutions are likely due to a complex interplay of interaction mechanisms involving both elastic nuclear collisions and inelastic electronic ones. The measured Bi sputtering yields versus Ar⁺ ion fluence for a fixed ion energy exhibit a significant depression at very low φ-values followed by a steady state regime above ∼2.0 × 10¹⁴ cm⁻². Measured sputtering yields versus Ar⁺ ion energy with fixing ion fluence to 1.2 × 10¹⁶ cm⁻² in the upper part of the yield saturation regime are also reported. Their comparison to theoretical model and SRIM 2008 Monte Carlo simulation predictions is discussed.     

高能重离子在聚合物中的辐照效应研究

Ion irradiation of polymers can induce irreversible changes in their macroscopic properties such as electrical and optical properties and the surface-related mechanical properties. Electronic excitation, ionization, chains scission, cross-links and mass losses are accepted as the fundamental events that give rise to the observed macroscopic changes. Detailed and systematic study of radiation induced effects in polymers enriches not only the knowledge of ion-material interactions but also supplies new bases for polymeric materials synthesis through ion-beam technologies. Previous work has concentrated mainly on effects induced by low-ionization particles such as γ-rays and electrons. Since 1980,s the application of high energy heavy ion accelerators enables the use of high energy heavy ion as an irradiation source, and many new and exciting effects and phenomena have been revealed.Energetic heavy ions in matter lose energy mainly through electronic excitation and ionization. Compared to low-ionization particles, high energy heavy ion possesses higher LET(linear energy transfer) values which can reach several to several tens keV/nm. As most of the primary ionizations and excitations occur close to the ion trajectory in a core of a few nanometers in diameter, a continuous damaged zone along the ion path can be induced,in which all bonds inside the zone can be destroyed due to the high rate energy deposition. Studies on this particularity of high energy heavy ion irradiation and its effects in materials will cause great influence on industry as well as on our daily life.The previous work has revealed the great difference in the effects induced by high energy heavy ions compared to the other particles. It has been shown that under irradiation with lower LET particles gas release depends on molecular structure and material composition, whereas under irradiation with high LET particles, such as high energy heavy ions, it is not the case. Some materials that undergo degradation under γ-irradiation can be cross-linked by irradiation with high energy heavy ions. In some cases new molecular structures were induced by high energy heavy ions with sufficiently high LET values. In recent years we have irradiated polyethylterephthalate (PET), polystyrene (PS), polycarbonate (PC) and polyimide (PI) with high energy Ar, Kr, Xe and U ion beams.Chemical and physical changes of the materials induced by the high energy heavy ion beams were investigated by Fourier-transform infrared ray spectroscopy, ultraviolet and visible transmission spectroscopy and X-ray diffraction measurements, from which damage cross-sections of various functional groups were determined[1]. An energy loss threshold for damage of phenyl ring in PET has been derived and difference in amorphization of PET under high and low LET irradiations was observed. It is found that alkyne end groups can be induced in all the materials above a certain electronic energy loss threshold, which is found to be about 0.8 keV/nm for PS and 0.4 keV/nm for PC. The production cross-section of alkyne end group increases with increasing electronic energy loss and shows saturation at high electronic energy loss values.