Structural disorder in sapphire induced by 90.3 MeV xenon ions

In our previous work [15], we have evidenced, using RBS-C, two effects in the aluminium sublattice of sapphire irradiated with 90.3 MeV xenon ions: a partial disorder creation that saturates at ∼40% followed above a threshold fluence by a highly disordered layer appearing behind the surface. In this work, by RBS-C analysis of the oxygen sublattice, we have observed only one regime of partial disorder creation that saturates at ∼60% in tracks of cross-section double of that found for the aluminium sublattice. Complementary analysis by X-ray diffraction shows that the lattice strain increases with the fluence until a maximum is reached about 7.5 × 10¹² ions/cm². For higher fluences, strain decreases first indicating a little stress relaxation in the material and tends afterwards, to remain constant. This stress relaxation is found to be related to the aluminium sublattice high disorder.     

快重离子在石墨中引起表面及体径迹的STM研究

用多种快重离子辐照高定向石墨（HOPG），借助扫描隧道显微镜（STM）系统地研究了表面及体内缺陷，结果表明，离子在表面及解理面上都形成了小丘状的缺陷，且在表面较容易形成，可以用非连续损伤径迹结构来对其进行解释。     

In~+离子注入蓝宝石(α-A1_2O_3单晶)的表面改性研究

研究了＜０００１＜和＜１２１０＞晶向蓝宝石（α－Ａｌ２Ｏ３单晶）在注入３６０ｋｅＶ．１×１０￣１６ｃｍ￣－２或１００ｋｅＶ、６×１０￣１６ｃｍ￣－２的Ｉｎ￣＋后产生的损伤、注入层的性能变化和退火行为。实验结果表明，退火过程中损伤的恢复和Ｉｎ的分布与退火气氛有关：在１００ｋｅＶ、６×１０￣１６ｃｍ￣－２的Ｉｎ￣＋注入时，注入层电阻率降低了１０个量级，大小为６．８×１０￣３·ｃｍ，表面损伤层的显微硬度提高了９２％；在３６０ｋｅＶ，１×１０￣１６ｃｍ￣－２的Ｉｎ＋注入时，其表面损伤层的显微硬度提高了４５％，在空气中不同温度下退火后，其显微硬度的变化和损伤的变化具有相同的规律。     

Irradiation effects in polycarbonate induced by 2.1 GeV Kr ions

Polycarbonate foil stacks were irradiated with 2.1 GeV Kr ions under vacuum at room temperature. The modifications in chemical structure induced by the irradiation were studied by means of Fourier transform infrared (FTIR) and ultraviolet visible (UV/VIS) spectroscopies. FTIR measurements reveal that material degradations through bond breaking are the main effects. Alkyne end groups are produced by the irradiation. UV/VIS measurements indicate a shifting of the absorption edge from ultraviolet towards visible, and a strong increase of absorbance in the ultraviolet and visible regions. The changes in absorbance induced by the irradiation at wavelengths of 380 nm, 450 nm and 500 nm scale well with Sc"(Sc is electronic energy loss) where the value of n increases from 1.69 to 2.02 with increasing of the wavelength. The results are briefly discussed.     

Surface characterization with keV clusters and MeV ions

Desorption of atomic and molecular species from solids can be achieved by bombardment with keV and MeV projectiles. In the studies described here, the secondary ions (SIs) are identified by time-of-flight mass spectrometry (TOF-MS) in an event-by-event counting mode. In this paper, desorption induced by two types of projectiles, viz. particle desorption mass spectrometry (PDMS) and secondary-ion mass spectrometry with keV clusters as projectiles (cluster-SIMS), is discussed.

PDMS uses fast heavy ions as projectiles (i.e., ions of E ≥ 0.1 MeV/amu and m ≥ 40 amu fission fragments are well suited for PDMS). The features of PDMS can be summarized as follows: it is suitable for isotopic and molecular analysis by virtue of the TOF-MS procedure; the desorption yield (ratio [%] of ions desorbed vs primary projectiles) can reach and even exceed 100%; thus mass spectra are obtained with a very low total primary-ion dose of ≤ 10⁶ ions. PDMS has a shallow sampling depth (5–100 monolayers, depending on the target), i.e. the technique is suitable for outermost-surface analysis without interference from the substrate.

Cluster-SIMS opens new perspectives for surface characterization. Clusters are attractive as projectiles because they are quasineutral, yet they can be accelerated, steered and focused. Their size, mass velocity and chemical composition can be selected to yield maximum SI emission. A new experimental approach has been devised to implement cluster-SIMS. We have observed up to 30-fold enhancement in the SI yield for cluster- vs monoatomic projectiles of equal velocities. Generally, the SI yields increase with the mass of the projectile and its velocity. The technique has particular promise for the surface mapping of organics.

Event-by-event coincidence counting can be combined with TOF-MS. This allows one to determine which masses are desorbed together from a primary impact size. Surface homogeneity is thus revealed with high planar resolution.     

Irradiation damage of uridine molecules with MeV heavy ions

In order to study the mechanism of the nucleotide directly damaged by energetic heavy ions, the residual ratio of uridine molecules after irradiation was measured by means of High Performance Liquid Chromatography (HPLC). The experimental results show that the irradiation damage probability depends on the electronic energy loss rate (S_e) of incident ions: first it increases quickly with S_e, then becomes stable when S_e reaches 800 eV/nm. The contribution of the nuclear collisions can be neglected compared with that of the electronic process. This is not only because that the nuclear energy loss rate (S_n) is much smaller than S_e for MeV heavy ions, but also because the energy deposition through the electronic process is more efficient in damaging molecules than through the nuclear process.     

Defects creation in sapphire by swift heavy ions: A fluence depending process

Single crystals of sapphire (α-Al₂O₃) were irradiated at GANIL with 0.7 MeV/amu xenon ions corresponding to an electronic stopping power of 21 keV/nm. Several fluences were applied between 5 × 10¹¹ and 2 × 10¹⁴ ions/cm². Irradiated samples were characterized using optical absorption spectroscopy. This technique exhibited the characteristic bands associated with F and F⁺ centers defects. The F centers density was found to increase with the fluence following two different kinetics: a rapid increase for fluences less than 10¹³ ions/cm² and then, a slow increase for higher fluences. For fluences less than 10¹³ ions/cm², results are in good agreement with those obtained by Canut et al. [B. Canut, A. Benyagoub, G. Marest, A. Meftah, N. Moncoffre, S.M.M. Ramos, F. Studer, P. Thévenard, M. Toulemonde, Phys. Rev. B 51 (1995) 12194]. In the fluences range: 10¹³-10¹⁴ ions/cm², the F centers defects creation process is found to be different from the one evidenced for fluences less than 10¹³ ions/cm².     

170MeV硫离子入射引起的反冲氩离子产额

利用１７０ＭｅＶ的Ｓ＾９＋与Ａｒ原子气体靶发生碰撞反应,采用高能离子引起的多重电离的飞行时间技术,测量了反冲击离子相对产额,并与多体经典轨道蒙特卡罗理论的计算结果进行了对比分析,发现理论低估了较高电荷态反冲离子的产额。     

Energy of secondary ions desorbed from insulating films by MeV heavy ions as a function of projectile velocity

The influence of projectile velocity on the axial energy distribution and mean axial energy of secondary ions was measured with a double-field time-of-flight method at the GSI accelerator-system. The secondary ions were ejected from thin layers ( ~ 150 nm) of CsI, MgO, CaF2, valine and phenylalanine irradiated with Sn and U projectiles.The mean energy of ions like Cs⁺ and Mg⁺ clearly increases in the velocity range from 0.3 to 1.5 cm/ns, whereas the energy of cluster ions remains almost constant. In most cases an influence of the cluster size on the mean ion energy was not observed. The results are discussed in relevance to desorption models and their significance for the optimum design of time-of-flight mass spectrometers.     

高剂量铂和钇离子注入Al2O3单晶的表面改性

研究了〈０００１〉和〈１２↑－１０〉晶向α－Ａｌ２Ｏ３单晶在高剂量的Ｙ、Ｐｔ离子注入后产生的损伤,注入层的性能变化和退火行为。实验结果表明,在室温,１７１ｋｅＶ、１×１０＾１７／ｃｍ＾２Ｙ离子注入的〈１２↑－１０〉α－Ａｌ２Ｏ３单晶的表面层约有１３９ｎｍ厚被无定形化。而１５８ｋｅＶ、９×１０＾１７／ｃｍ＾２Ｐｔ离子注入的〈０００１〉α－Ａｌ２Ｏ３单晶的表面层不产生无定形,且实际离子注入进衬底的剂量     

重离子单粒子效应实验研究

在HI—l3串列加速器上建立了对微电子器件进行单粒子效应模拟实验的辐照和检测技术。利用该Q3D磁谱仪获得种类和能量单一、强度分布均匀且足够弱的重离子辐照源，利用散射室内的半导体探测器和焦面上的位置灵敏半导体探测器监测辐照离子。用该装置和技术测量了在8个传能线密度(LET)值的重离子辐照下引起的几个存储器器件的单粒子翻转（SEI）截面o(L)。从测得的o(L)——LET曲线，结合空间重离子和质子辐照环境模型以及离子与微电子器件相互作用模型计算，预言了器件在空间的单粒子翻转率。     

Surface erosion induced by heavy ion backscattering analysis

Material removal induced by HIBS (Heavy Ion Backscattering Spectrometry) analysis has been investigated. For this purpose the thickness of thin metal films deposited on graphite was measured as a function of fluence of the Si and Ti projectile ion beam. Steady state erosion rates are in fair agreement with surface sputtering rates calculated by SRIM. For some layers however, the first few monolayers are removed at a much faster rate. A comparison with standard He RBS is made and consequences for the applicability of HIBS are discussed.     

Surface topography induced by swift heavy ion impacts

Classical molecular dynamics simulations have been carried out to investigate the development of surface topographies following irradiation by swift heavy ions. Two models were used: a thermal spike model in which atoms within a cylinder surrounding the path of the ion are given kinetic energy due to the electronic energy loss of the particle; and an electron stripping with recombination model. Both models give qualitatively similar results and show the formation of hillocks on the surface above the ion track and a less dense track core near to the surface.     

Irradiation damage induced on polyethylene terephtalate by 1.6 MeV deuteron ions

The irradiation damage caused on polyethylene terephtalate (Mylar, PET) samples by 1.6 MeV deuteron ions has been measured using simultaneously the nuclear reaction analysis (NRA) and the transmission energy loss (TEL) techniques. The irradiation was carried out at normal incidence relative to the target surface with the irradiation beam being used as the analysis beam. The evolution of the overall damage during irradiation was evaluated by measuring the variation of the energy loss of the deuteron beam passing through the target. For this purpose, a solid state Si detector placed at a forward angle of 30° relative to the incident beam direction was used. The NRA spectra recorded by a second Si detector located backward at 150° allowed the evaluation of the carbon and the oxygen depletion. The beam spot size was circular in shape and 1 mm in diameter and the beam current was set at 5 nA. The ion fluence was increased up to the value of 2.5 × 10¹⁶ deuterons/cm². It was observed that the target energy loss decreased steadily as the fluence increased and levelled off at high fluence. The ¹⁶O(d,p₀)¹⁷O, ¹⁶O(d,p₁)¹⁷O^* and ¹²C(d,p₀)¹³C reactions were used for monitoring the evolution of the oxygen and carbon content as a function of the deuteron fluence. A monotonic decrease of the oxygen content with the increase of ion fluence was observed. At the highest fluence the oxygen depletion reached a value of about 75%. For carbon, a weak depletion was observed at fluence ranging from 2.5 × 10¹⁵ d/cm² to 1.0 × 10¹⁶ d/cm² followed by a levelling-off with a total loss around 20%.     

Modification of N-doped carbon induced by 30 MeV C60 ions

In the present work, 120 keV N-ion doped and 30 MeV C₆₀ ion irradiated graphite-like-carbon samples were characterized by RBS, micro-FTIR, micro-Raman, XPS spectroscopy and the variation of the properties of the samples with the N-dopant and/or C₆₀ irradiation fluence have been studied. The RBS spectra showed that C₆₀ irradiation can induce a partial diffusion of N atoms to the surface and the amount of the diffused N atoms increases slightly with increasing C₆₀ irradiation fluence. The FTIR and Raman spectra exhibit characteristic bands of carbon nitrogen bonds showing that the C and N atoms are chemically bonded. The amount of chemically bonded C and N atoms increases with increasing N-dopant. By deconvolution of the XPS spectra, the atomic concentration of N and C atoms were obtained and it was identified that the samples mainly consist of three phases, namely, C₃N₄, CN_x and tetrahedral amorphous carbon. The effect of N-dopant and C₆₀ irradiation fluence on the modification of the properties of the samples is also discussed.     

Surface nanostructuring of SrTiO3 single crystals by slow highly charged ions and swift heavy ions

Single crystals of strontium titanate have been irradiated with both slow highly charged Xe ions extracted from an Electron Beam Ion Trap and swift heavy Xe ions. After irradiation, the crystals were investigated by scanning force microscopy in air. In both cases nanohillocks due to impact of individual projectiles were observed. This similarity originates from the fact that both swift heavy ions and slow highly charged ions initially transfer their energy to the electronic system of the target, leading to a localized region of high electronic excitation. This electronic excitation is subsequently transferred to the lattice atoms by electron-phonon coupling, leading to pronounced lattice heating. The formation of surface hillocks can then be ascribed to a melting process. We also present first evidence for the existence of a potential energy threshold for nanohillock formation on strontium titanate surfaces by slow highly charged ions.     

Interface mixing induced by swift heavy ions at metal-oxide/silicon interfaces

It was observed previously that ceramic/ceramic bilayers were very sensitive with respect to the electronic stopping power S_e, i.e. strong interface mixing, scaling with , occurred if a threshold S_ec was exceeded. The threshold seemed to be determined by the higher track formation threshold of two constituents forming the bilayer. Although no track formation has been observed in crystalline Si even for Uranium projectiles, interface mixing was observed previously for some Si-multilayers.

In this paper we report on the interface mixing of NiO, Fe₂O₃, TiO₂ on Si due to irradiation with 90–350 MeV Ar-, Kr-, Xe- and Au-ions at 80 K at fluences up to 9E15 ions/cm². Interface mixing, analyzed by means of Rutherford Backscattering Spectrometry (RBS), is found for these bilayers, too. But the threshold for intermixing is significantly higher compared to the ceramic/ceramic bilayers. This observation could be an evidence for the threshold being determined by the Si-layer. In contrast to NiO/Si and Fe₂O₃/Si, where an usual random walk mixing Δσ² = kΦ was observed, the interface broadening Δσ² for TiO₂/Si is found to scale nonlinearly with the ion fluence, which indicates that mixing is driven by a chemical solid-state reaction. At higher fluences plateaus form at the low energy Ni-edge of the RBS spectra. The plateaus indicate phase formation. X-Ray diffraction spectra does not show any evidence for new crystalline phases.     

快重离子在聚合物潜径迹中引起的损伤效应研究

在室温和真空环境下利用不同的快重离子(1.158GeV Fe56、1.755GeV Xe136及2.636GeV U238)对多层堆叠的聚对苯二甲酸乙二醇酯(PET)、聚碳酸脂(PC)和聚酰亚胺(PI)进行了辐照,结合X射线衍射(XRD)、傅立叶红外光谱(FTIR)及紫外可见光谱测量技术,在较宽的电子能损(1.9-19.0 keV·nm-1)和注量范围(1×1010-6×1012 cm-2)研究了离子在不同聚合物潜径迹中引起的损伤过程,观测到了主要官能团的降解、炔基生成、非晶化及紫外吸收边缘的红移等现象随辐照注量及电子能损的变化趋势.通过对损伤过程的定量分析,应用径迹饱和模型假设,分别给出了Fe、Xe和U离子在不同电子能损下辐照PC时的平均非晶化径迹半径和炔基形成半径,并用热峰模型对实验结果进行了检验.     

Transmission sputtering of titanium by 114 MeV fluorine ions

A perturbed hard core equation of state, applicable to both spherical and non-spherical cores, is described and tested with both molecular fluids and liquid metals (Na and U). The theory was found to be particularly accurate in describing the vapour pressure curve of molecular fluids but provides only a qualitative picture for liquid metals. The applicability of the equation to describe the thermodynamic properties of liquid UO₂ has been studied and a full set of thermodynamic data is reported.     

MeV离子辐照拟南芥的萌发规律研究

利用不同能量的F离子和H离子分别辐照拟南芥干种子,通过种子发芽率实验研究了低能离子生物效应与离子种类、离子能量和辐照注量之间的关系。实验结果表明,H离子的辐照效率高于F离子;F离子辐照的种子发芽率曲线,随F离子注量的增加,均呈现先下降后升高再下降的马鞍曲线形状,达到马鞍峰值需要的注量随离子能量的增加而减少。文中对上述现象的可能机理进行了讨论。