Interaction between ethanol cluster ion beam and silicon surface

The interaction between an ethanol cluster ion beam and a silicon surface was investigated. The sputtering depth of a silicon surface irradiated with an ethanol cluster ion beam increased with acceleration voltage. The number of disordered atoms on the silicon surface irradiated with an ethanol cluster ion beam initially showed a small dependence on retarding voltage and then a steep decrease with a further increase in retarding voltage.     

Molecular dynamics simulations for gas cluster ion beam processes

Molecular dynamics (MD) simulations of large argon clusters impacting on silicon targets were performed. The characteristics of crater formation, a typical collisional effect with large cluster impact were examined from the viewpoint of incident energy, cluster size and incident angle. The MD simulation results suggested that the condition where an incident cluster penetrates into the solid target and causes a crater is mainly dominated by the incident energy-per-atom rather than total incident energy of the cluster. Additionally, the MD simulations of sequential multiple cluster impacts and grazing-angle cluster irradiation on irregular surface structures were studied to characterize the surface modification effects with large cluster ion beam process.     

Angular dependence of sputtering effects by ethanol cluster ion irradiation on solid surfaces

In order to clarify the interactions of ethanol cluster ions with solid surfaces such as Si(100), SiO₂ and Au surfaces, sputtering effects were investigated by changing the acceleration voltage and incident angle (θ) of the cluster ions. The sputtered depth at a normal incidence of θ = 0° increased with an increase of the acceleration voltage. The sputtering ratio of Si to SiO₂ was approximately 10, which suggested that chemical reactions between Si and ethanol produced silicon hydride as a dominant etching material. Furthermore, the sputtered depth of Si surfaces by ethanol cluster ion irradiation had a maximum value at an incident angle between 10° and 60°, and the angle corresponding to the maximum peak increased with an increase of the acceleration voltage. On the other hand, for the physical sputtering of Au surfaces by ethanol cluster ion irradiation, the sputtered depth decreased with the increase of the incident angle, and the change was in accordance with cos θ.With regards to the angular distribution of sputtered particles, Si surface atoms were ejected by ethanol cluster ion irradiation according to a cosine law distribution. This indicated that the Si surfaces were chemically sputtered by ethanol cluster ion irradiation. On the other hand, for the case of Au surfaces, the ejection of the sputtered particles changed to the under-cosine law. This was ascribed to the lateral sputtering effect of ethanol cluster ion irradiation.     

Progress and applications of cluster ion beam technology

Cluster ion beam processing has been extensively developed during the 25 years since the concept originated. Low energy surface interaction effects, lateral sputtering phenomena and high-rate chemical reaction effects have been explored experimentally and have been explained by means of molecular dynamics (MD) modeling. Practical production equipment for a wide range of applications has also been successfully developed. The technology is now advancing rapidly in the fields of sub-nanoscale processing of metals, semiconductors and insulating materials. This paper reviews important events which have taken place during the development with emphasis placed on emerging new advances which have occurred during several recent years.     

Radiation damage of the metal surface as a possible reason for the secondary negative ion emission of pure metals

It is shown that due to different positions of the ground level and affinity level of a target atom relative to the Fermi level for both positive and negative secondary particles, emitted during ion bombardment from pure metals, the known electron-exchange theory of the secondary positive ion emission for pure metals is inapplicable in the case of negative ion formation. Also, the corresponding electron-exchange theory for such metals covered by electropositive films turns out to be inapplicable. A model of the secondary negative ion emission, caused by radiation effects on the surface of those metals, arising during ion bombardment, is presented.     

电子-离子双束纳米工作站

现代微电子工业迅猛发展,对电子设备的精度和功能也提出了新的要求。电子-离子双束纳米工作站是扫描电子束和聚焦离子束技术的独特融合,突破了只能对表层成像和分析的局限,它可以对样品进行三维的、表面下的观察和分析,也可以切割、研磨样品材料和沉积特定的材料,用它可以获得以前无法得到的样品信息。该工作站为研究人员和制造人员提供了一种对多种样品在纳米尺度进行修改、制作和分析的有效工具。     

Photocatalytic properties of Cr-doped TiO2 films prepared by oxygen cluster ion beam assisted deposition

We prepared Cr-doped titanium dioxide (TiO₂) films by oxygen (O₂) cluster ion beam assisted deposition method, and investigated photocatalytic properties of the films as well as crystallographic property, optical property and surface morphology. The films prepared at a substrate temperature below 200 °C were found to be amorphous from the X-ray diffraction measurement. For the substrate temperatures such as 300 °C and 400 °C, the films exhibited rutile and/or anatase structures. The film surface measured by the atomic force microscope (AFM) was smooth at an atomic level. Furthermore, the optical band gap decreased with increase of Cr-composition, and it was approximately 3.3 eV for the non-doped films, 3.2 eV for the 1% Cr-doped films and 3.1 eV for the 10% Cr-doped films, respectively. With regard to the photocatalytic properties of the Cr-doped TiO₂ films, we measured the change of contact angle as well as the photocatalytic degradation of methylene blue by the UV light irradiation. Compared with the non-doped films, the 1% Cr-doped films prepared at a substrate temperature of 400 °C showed high degradation efficiency. In addition, the contact angle of the 1% Cr-doped films with an initial value of 60° decreased to 10° by the UV light irradiation for 20 min, and the films exhibited the predominant properties of photocatalytic hydrophilicity even for the UV light irradiation with longer wavelengths.     

离子束溅射生长Ge纳米薄膜的表面形貌观察

采用离子束溅射技术并按正交试验方案生长了不同厚度以及在不同条件下退火的Ge纳米薄膜,用AFM图谱对薄膜的表面形貌进行了表征.结果表明厚度为2.8nm的Ge膜在600℃下退火10min,出现了高4nm、直径50nm左右的Ge岛,而10nm厚的Ge膜在720℃下退火120min,岛的数量较多且分布比较均匀.通过离子束溅射机理和沉积原子之间的扩散运动,对这些现象进行了较为合理的解释.     

浅析离子辅助光学薄膜镀膜机的特性

真空镀膜产品的质量问题，一直是应用镀膜技术人员探索的课题。人们经过长期探索，采用离子束辅助沉积镀膜技术，改善了镀膜层牢固性，提高了反射率。本技术在通讯技术、太阳能应用、汽车、装潢等领域应用十分广泛。本文介绍了真空离子束辅助沉积镀膜设备特性。     

Focused ion beam production of nanoelectrode arrays

We present a method for the production of nanoelectrodes using focussed ion beam techniques (FIB). The electrodes utilise nanometric holes milled in a silicon nitride based pasivation layer, followed by wet etching of a silicon oxide based pasivation layer, to expose an underlying gold electrode. After functionalisation using a surface assembled monolayer and an electrochemically grown polypyrrole, these gold nanoelectrodes have been tested, via cyclic voltammetry, in the detection of [Fe(CN)₆]^4−/3− ions. The nanoelectrodes will be used to investigate the electrical properties of nanometric biological specimen.     

Measurement of carbon sputtering yield by N ion beam and lifetime dependence of resulting foils on thickness

Carbon stripper foils with a higher nitrogen content were made by ion beam sputtering with reactive nitrogen gas. Such foils seem to be very useful as strippers for high-intensity heavy ion accelerators. To know further characteristics of the lifetime of such carbon foils, we have measured the sputtering yield of the carbon source material at a sputtering voltage of 4–15 kV and the lifetime dependence of such foils on thickness. Lifetime measurement was performed with a 3.2 MeV Ne⁺ ion beam. The sputtering yield on average showed 0.75 atoms/ion at over 9 kV sputtering voltage. The lifetime of the foils noticeably depends on the foil thickness, and the thickness range as practical stripper foil is to be around 15 to 33 μg/cm². Two foils made at 13 kV showed extremely long lifetimes of 6800 and 6000 mC/cm² at maximum and the foils made above 10 kV lived longer than about 900 mC/cm², which correspond to about 270 and 40 times longer than commercially available best foils. We measured the thickness ratio of nitrogen to carbon in each foil made at the different sputtering voltages and at the different irradiation stages (mC/cm²) by RBS method. We also inspected the structure of a nitrided carbon foil by transmission electron microscopy.     

离子束刻蚀机的电源系统

离子束刻蚀机的性能,除主机外,在很大程度上取决于供电电源系统。为了提高离子束刻蚀机整机工作的稳定性,在以往的配套电源的基础上,研制了一套电源系统,用于离子束刻蚀机中。整机工作稳定度达±0.8%/h,每次连续刻蚀器件8h以上,连续运转3年多,电源系统稳定可靠。是国内离子束刻蚀机电源系统性能较好的供电电源系统。     

Fail-safe ion chamber beam loss monitor system for personnel protection

A fail-safe beam loss monitor system has been designed for use in the Los Alamos Neutron Scattering Center (LANSCE) Radiation Security System (RSS). The latest version (Model III) has been in use since 1991. This system has been carefully designed to protect personnel from large radiation doses caused by errant beam conditions during beam transport. Due to limited shielding between the beam transport lines and occupied areas, personnel can safely occupy these areas only if the beam losses in the transport lines are sufficiently low. Although the usual solution is to increase the bulk shielding between the beam lines and the occupied areas, the physical dimensions of the site do not permit additional shielding to be added. In this paper we will discuss the design and implementation of the fail-safe beam loss monitor system.     

Development of a compact angle-resolved secondary ion mass spectrometer for Ar sputtering

A compact angle-resolved secondary ion mass spectrometer with a special geometrical configuration, composing of a differentially pumped micro-beam ion gun, a tiltable sample stage and a time-of-flight (TOF) mass spectrometer, was newly developed. This system enables the measurement of angular distribution (AD) of secondary ions, which are ejected by oblique Ar⁺ sputtering, by a simple tilt operation of the sample stage for ejection angles ranging from 0° to 60° with keeping the ion incidence angle constant 62°±2° from the normal to the surface. Using this system, AD of secondary ions from an HfN film by 3 keV Ar⁺-ion bombardment was measured at room temperature. Since the yield of HfN⁺ dimer ions was almost independent of Hf⁺ and N⁺ monomer ions, it was concluded that the HfN⁺ dimer ions were generated via the “as such” direct emission process.     

In-depth distribution of ion beam damage in SiC

In this paper we report on the ion beam bombardment-induced alteration of SiC measured at different ion energies (300-1700 eV) and at wide range of incident angle (43°-87°). Surface roughening was reduced by sample rotation during sputtering. The change of the concentration was characterized by Auger electron spectroscopy. Both low and high energy Auger peaks of Si were detected, which allowed us to estimate the depth distribution of the components. The observed alteration of Auger peak heights will be explained by simple model of the changed in-depth distribution. The model gives an estimate for the composition of top layer (the real surface) of SiC in different sputtering conditions, as well as the in-depth distribution of Si and C.     

Praseodymium compound formation in silicon by ion beam synthesis

The compound formation in the ternary system Pr-Si-O initiated by ion beam synthesis inside bulk-Si was studied by transmission electron microscopy and X-ray diffraction. The oxygen content was varied by additional O⁺ ion implantation and by oxidation of the bulk-Si. For annealing temperatures of 1100 °C, Pr silicate nanoclusters were observed consisting of Pr_9.33Si₆O₂₆ or Pr₂Si₂O₇. These silicates were the dominating and most stable Pr compounds. The interfaces between Pr silicate and the crystalline Si were atomically abrupt after high-temperature annealing. Pr silicide (PrSi₂) was detected for lower annealing temperatures such as 900 °C and for higher annealing temperatures in minor fraction also in samples with enhanced O content. Pr oxide (Pr₂O₃), the promising high-k material, was not definitely verified. In ion beam synthesis, the energy related to structural reordering during solid-state compound formation is a parameter that controls the proceeding processes in addition to other parameters like chemical reactivity and the compound interface matching.     

Metal cluster complex primary ion beam source for secondary ion mass spectrometry (SIMS)

To develop a solution-type ion beam source utilizing a wide variety of metal cluster complexes that are stable only in organic solvents, we have investigated an electrospray method for transferring ions from solutions to gas phase. As initial experiments, we have studied electrospray characteristics of ethanol solutions containing a room-temperature molten salt (i.e., an ionic liquid) and acetic acid as alternatives to solutions of metal cluster complexes. In electrospray experiments, we used a stainless-steel capillary with an inner diameter of 30 μm. Experimental results showed that electrosprayed currents increased with applied voltage in both positive-ion and negative-ion modes. In addition to positive currents, stable negative currents were also confirmed to be produced. Current exceeding 250 nA was produced at 2 kV with a flow rate of 2 μL/min at a concentration of 1 × 10⁻³ mol/L. It was confirmed that several nA out of electrosprayed currents were delivered through an orifice (120 μm internal diameter) into a vacuum chamber. Experimental results indicate that the electrospray method seems to be applicable to an ion beam source for utilizing massive metal cluster complexes in solutions.     

Proposals for producing novel periodic structures on silicon by ion bombardment sputtering

It is proposed, and confirmed analytically, that if multiple ion fluxes are incident simultaneously, at different oblique polar angles but at the same Azimuthal angle, on to a target, then the individual ripple patterns generated by sputtering are superimposed to produce novel surface structures. It is also shown that multiple focused ion fluxes incident on to rotating targets can produce circular novel patterns.     

双离子束溅射法制备铁氮薄膜

使用双离子束溅射法制得了铁氮薄膜,随着基片温度的变化,薄膜的成分是ε－Fe2-3N,γ′－Fe4N或是二相的混合物,薄膜的晶粒尺寸随基片温度的升高而增大。以振动样品磁强计（VSM）测定了薄膜的磁性能。另外,研究了在基片温度为160℃时,改变主源中通入N2／Ar的比例对薄膜成分的影响。     

低能离子束方法制备磁性Fe-Si合金薄膜

利用质量分离的低能离子束技术．获得了磁性Fe-Si合金薄膜。利用俄歇电子能谱法(AES)、X射线衍射法(XRD)以及交变梯度样品磁强计(AGM)测试了样品的组分、结构以及磁特性。测试结果表明在室温下制备的Fe-Si合金是Fe组分渐变的非晶薄膜,具有室温铁磁性。当衬底温度为300℃时制备的非晶Fe-Si薄膜中有Fe硅化物FeSi相产生．样品的铁磁性被抑制。