Micromachining using deep ion beam lithography

In recent years the process combining deep X-ray lithography with electroforming and micromoulding (i.e. LIGA), has become an important technique for the production of high aspect-ratio microstructures for the fabrication of micro-electromechanical systems (MEMS). The aim of this paper is to investigate the potential of high energy ion microbeams for carrying out similar micromachining, and in particular for overcoming the geometrical restrictions which are inherent in deep x-ray lithography. Using a scanned 2.0 MeV proton beam of approximately 1 micron diameter, we produced latent microstructures in high molecular weight PMMA resist. These resist microstructures were subsequently developed using a multi-component developer which is highly specific in the removal of exposed resist, while leaving unexposed or marginally exposed material unaffected. A suitable range of exposures has been established, and factors affecting the geometrical fidelity of the produced microstructure have been investigated. The relative advantages and limitations of this technique vis à vis deep X-ray lithography are discussed.     

Extending Bragg peak of heavy ion beam and melanoma cell inactivation measurement

A rotating range modulator was designed and manufactured.which is applied to extend Bragg peak of heavy ion beam.Bragg curves of 75MeV/u ^16O and 75MeV/u ^12C ion beams through this range modulator were measured respectively and two evident spread-out Bragg peaks corresponding to the modulated beams above are shown.In addition,inactivation effect of the modulated 75MeV/u ^16O ion beam at nine different penetration depths on melanoma cells(B16) was measured.Results indicate that lethal effects at the spread-out Bragg peak region are larger than at the plateau of the particle beam entrance.     

Phoswich探测器的重离子束测试

利用一套由１ｍｍ厚的ＰＩＬＯＴ－Ｕ和４０ｍｍ厚的ＮＥ１１５塑料闪烁体组成的Ｐｈｏｓｗｉｃｈ（光叠层望远镜）探测器测量了４０Ａｒ（２５ＭｅＶ／ｕ）＋１９７Ａｕ反应中出射的产物，粒子鉴别采用Ｐｈｏｓｗｉｃｈ的快慢成分方法．结果表明该方法能清楚地分辨出粒子的电荷．对Ｚ＝１的粒子，ｐ、ｄ和ｔ亦能分开．     

The role of autophagy in cell survival from heavy ion irradiation in the plateau region

To study cytotoxic effect of heavy ion irradiation in the plateau region, and investigate whether autophagy in- duced by heavy ion irradiation is cytoprotective, HeLa cells were irradiated with 350 MeV/u carbon ions beams, and the clonogenic survival was analyzed. The results showed that cell survival decreased with increasing doses. It was also found that G2/M-phase cells increased, and the autophagy-related activity was significantly higher than the control. When autophagy was blocked by 3-methyladenine in carbon-ion irradiated cells, G2/M phase arrest and the percentage of apoptosis cells were further elevated, and cell survival decreased significantly, in- dicating the induction of cytoprotective autophagy by carbon-ion irradiation. Our results demonstrated that autophagy induced by carbon ion irradiation provided a self-protective mechanism in HeLa ceils, short-time inhibition of autophagy before carbon-ion irradiation could enhance radiation cytotoxicity in HeLa cells.     

Live cell calcium imaging at the single ion hit facility of GSI

To study the fast intracellular calcium response after ion irradiation in living mammalian cells, a live cell calcium imaging set-up was constructed at the targeted cell irradiation facility at GSI. This work introduces the live cell calcium imaging system, shows its performance, an example of the ratio-metric calcium measurement and its application to on-line study calcium response to targeted ion irradiation in human cells.     

AFM characterization of model nuclear fuel oxide multilayer structures modified by heavy ion beam irradiation

This work explored a potential new model dispersion fuel form consisting of an actinide material embedded in a radiation tolerant matrix that captures fission products (FPs) and is easily separated chemically as waste from the fuel material. To understand the stability of this proposed dispersion fuel form design, an idealized model system composed of a multilayer film was studied. This system consisted of a tri-layer structure of an MgO layer sandwiched between two HfO₂ layers. HfO₂ served as a surrogate fissile material for UO₂ while MgO represented a stable, fissile product (FP) getter that is easily separated from the fissile material. This type of multilayer film structure allowed us to control the size of and spacing between each layer. The films were grown at room temperature by e-beam deposition on a Si(1 1 1) substrate and post-annealed annealing at a range of temperatures to crystallize the HfO₂ layers. The 550 °C annealed sample was subsequently irradiated with 10 MeV Au³⁺ ions at a range of fluences from 5 × 10¹³ to 3.74 × 10¹⁶ ions/cm². Separate single layer constituent films and the substrate were also irradiated at 5 × 10¹⁵ and 8 × 10¹⁴ and 2 × 10¹⁶, respectively. After annealing and irradiation, the samples were characterized using atomic force imaging techniques to determine local changes in microstructure and mechanical properties. All samples annealed above 550 °C cracked. From the AFM results we observed both crack healing and significant modification of the surface at higher fluences.     

Proton beam writing of microstructures at the ion nanoprobe LIPSION

Proton beam writing (PBW) is a direct writing technique which allows the creation of three-dimensional structures with a high aspect ratio in the micrometer and nanometer range in photoresist materials without the use of templates. At the high-energy ion nanoprobe LIPSION of the University of Leipzig this technique was established recently. In this article the latest results concerning this topic are presented. PBW was successfully performed with the positive resist polymethyl methacrylate (PMMA) which is now used at LIPSION in addition to the negative resist SU-8. With the new data acquisition system MICRODAS being commissioned, a new scan program was developed and tested which is dedicated to the creation of arbitrarily shaped structures. Squares with dimensions down to 1.2 μm were created in SU-8 at LIPSION. Furthermore, Ni grids were produced by electroplating, using templates written in PMMA resist. In addition, first structures for studying the growing behavior of Bragg reflectors and the optical characterisation of ZnO nanowhiskers were produced by PBW.     

同步辐射光刻技术研究进展

光刻技术是推动集成电路制造业不断向前发展的关键技术。X射线光刻技术是下一代光刻技术的一种,具有产业化的应用前景。掩模技术是X射线光刻技术的难点,本文报告了国内利用同步辐射源的X射线掩模和光刻技术研究的最新进展。     

尼尔逊离子源重离子束流的发射度

尼尔逊离子源已广泛地应用于重离子加速器、同位素分离器及研究用离子注入机。用于C-600离子注入机的尼尔逊离子源,目前已获得达100μA的三十余种重离子束,其中有近二十种固体元素。     

Intensive irradiation of carbon nanotubes by Si ion beam

Multi-walled carbon nanotubes were irradiated with 40 keV Si ion beam to a dose of 1×10^7 cm^-2. The multiple-way carbon nanowire junctions and the Si doping in carbon nanowires were realized. Moreover, the formation processes of carbon nanowire junctions and the corresponding mechanism were studied.     

Development of function-graded proton exchange membrane for PEFC using heavy ion beam irradiation

The graded energy deposition of heavy ion beam irradiation to polymeric materials was utilized to synthesize a novel proton exchange membrane (PEM) with the graded density of sulfonic acid groups toward the thickness direction. Stacked Poly(tetrafluoroethylene-co-hexafluoropropylene) (FEP) films were irradiated by Xe⁵⁴⁺ ion beam with the energy of 6 MeV/u under a vacuum condition. The induced trapped radicals by the irradiation were measured by electron spin resonance (ESR) spectroscopy. Irradiated films were grafted with styrene monomer and then sulfonated. X-ray photo-electron spectroscopy (XPS) spectra showed that the densities of sulfonic acid groups were controlled for injection “Surface” and transmit “Back” sides of the fabricated PEM. The membrane electrode assembly (MEA) fabricated by the function-graded PEM showed improved fuel cell performance in terms of voltage stability. It was expected that the function-graded PEM could control the graded concentration of sulfonic acid groups in PEM.     

Ion beam induced charge characterisation of a silicon microdosimeter using a heavy ion microprobe

An ion beam induced charge (IBIC) facility has been added to the existing capabilities of the ANSTO heavy ion microprobe and the results of the first measurements are presented. Silicon on insulator (SOI) diode arrays with microscopic junction sizes have recently been proposed as microdosimeters for hadron therapy. A 20 MeV carbon beam was used to perform IBIC imaging of a 10 μm thick SOI device.     

Manipulation of a cooled beam for future heavy ion therapy

In order to deliver a high-quality beam for biophysics experiments, an electron cooler, a wideband rf system, and an extraction kicker have been installed in the Heavy Ion Medical Accelerator in Chiba (HIMAC) at the National Institute of Radiological Sciences (NIRS). A demonstration of beam manipulation during cooling and fast extraction is presented in this paper.     

Diffusion studies using ion beam analysis

The combination of ion implantation with nuclear methods such as Rutherford Backscattering Spectrometry (RBS), Nuclear Reaction Spectroscopy (NRS) or Elastic Recoil Detection Analysis (ERDA) has shown to be well adapted to the study of impurity migration in solids induced by either thermal annealing or irradiation. This paper gives some typical examples studied in more detail in our laboratory. Among them, the determination of thermodynamical data (diffusion coefficients, activation energies) from the analysis of the evolution of implanted species is rather classical. As an illustration the diffusion study of lanthanum implanted into apatite using RBS is presented. This work is of interest with regard to nuclear waste storage in geological sites where apatites are possible migration barriers to radioactivity and lanthanum is a representative fission product. The second study taken from the metallurgical field concerns the determination of the nitrogen diffusion coefficient into aluminium using NRS. Finally, a study concerning hydrogen diffusion in an a-SiC:H material (plasma facing materials) induced by deuterium bombardment will be presented. The hydrogen profiling is performed using ERDA.     

Materials analysis using ion beam techniques

Basic concepts of ion beam analysis techniques for the study of the composition and structure of surfaces, interfaces and thin layers are reviewed. For surface characterization the use of low-energy (1–20 keV) ions is compared with the use of medium-energy (50–200 keV) and high-energy (200 keV-several MeV) ions. Thin-layer analysis with Rutherford backscattering (RBS) and nuclear reaction analysis in combination with channeling is described in detail. Requirements, including the necessary precision demands, for the instrumentation are discussed. The analysis via computer simulations of channeling data, in particular of data for the determination of lattice sites of solute atoms in single crystals, will be treated. As an illustration of the potential of ion beam techniques for structure analysis, a number of examples of lattice site locations is presented.     

Creation mechanism of pores by ion beam modification of fluoropolymer film membranes

Producing structures in membranes at the nanometer scale can serve several applications such as to localize molecular electrical junctions and switches, and to function as masks. In previous work we demonstrated the fabrication of porous membranes in masked fluoropolymer films using scanned ion beam bombardment. The process dispenses the use of time consuming chemical and etching processes. Here we report on the creation mechanism of pores using ion bombardment. Aspects of the ion beam interaction with matter are explained as well as an analysis of the shape of the fabricated structures. The pores were produced using our feedback controlled ion beam apparatus and were analyzed using optical and atomic force microscopic (AFM) analyses.     

Unique capabilities of heavy ion elastic recoil detection with gas ionization detectors

Specific aspects of heavy ion elastic recoil detection (ERD) with gas ionization detectors have been studied using representative measurements. A particular strength of the technique is the detection and direct quantification of elements with atomic numbers in the range Z=2–8, which are often not accessible with other ion beam techniques. Within the wider spectrum of analytical techniques in materials science, heavy ion ERD has unique capabilities, when the particular problem requires in addition the analysis of heavy elements or hydrogen detection. Whenever only heavy element analysis or only hydrogen profiling is of interest, alternative techniques tend to be superior.