Low Energy Ar Ion Research Articles

A New Method for the Simultaneous Detection of Mammalian Cells and Ion Tracks on a Surface of CR-39

The geometric locations of ion traversals in mammalian cells constitute important information in the study of heavy ion-induced biological effects. We employed a contact microscopy technique, which was developed for boron imaging in boron neutron capture therapy to the irradiation mammalian cells by low-energy heavy ions. This method enables the simultaneous visualization of mammalian cells as a relief on a plastic track detector, CR-39, and the etch pits which indicate the positions of ion traversals. This technique provides visual geometric information about the cells and ion traversal, without any specially designed devices or microscopes. Only common laboratory equipment, such as a conventional optical microscope, a UV lamp, and commercially available CR-39 is required. To validate this method, CHO-K1 and HeLa cells were cultured on the CR-39 surface and then irradiated with low-energy Ar and Ne ions, respectively. The positions of induced DNA double strand breaks were detected as gamma-H2AX fluorescent spots, which coincided with the positions of the etch pits in the cell relief image.

Quantitative Analysis of 2-D Electrostatic Potential Distributions in 90-nm Si pMOSFETs Using Off-Axis Electron Holography

Off-axis electron holography has been used for quantitative analysis of 2-D electrostatic potential distributions in 90-nm Si p-channel MOSFETs (pMOSFETs). The sample preparation for electron holography is based on focused-ion-beam (FIB) and low-energy (3 keV) Ar-ion backside milling. The measured electrostatic potentials from two pMOSFETs with different offset spacer oxide widths are compared in terms of the separation of extension junctions and source/drain (S/D) junctions. The metallurgical gate length (L <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">met</sub> ) and the S/D junction encroachment (deltaL) under the gate are measured and compared for the two devices. The electrostatic potential abruptness and electric field intensity are investigated around the drain side, and the lateral and vertical electric field intensities are also compared.

Sputtering of Fe(1 0 0) due to low-energy ion bombardments: Molecular dynamics simulation

Molecular dynamics simulations were carried out to investigate the sputtering of Fe(1 0 0) due to low-energy (⩽10 keV) Ar ion bombardments. Bohr potentials fitted to the results of ab initio calculations for diatomic pairs (Ar–Fe, Fe–Fe) were used as the repulsive screened Coulombic potentials in sputtering simulations. The sputter yields predicted by molecular dynamics were in good accordance with the available experimental data. The threshold energy for sputtering, distributions of kinetic energies of sputtered atoms and their depth of origins could also be obtained.

The initial stages of graphite formation on the diamond (1 0 0) 2 × 1 surface

A precursor site which is likely to be involved in the formation of graphite on the diamond (1 0 0) 1 × 2 surfaces has been created by bombardment with low energy Ar ions and characterised by high resolution X-ray photoelectron spectroscopy (XPS) of the C 1s photoelectron line.

A study of the stress and resistivity of Al/Ti films deposited by an ion beam assisted process for surface acoustic wave devices applications

A highly textured Al/Ti films were deposited on 128° Y– X LiNbO 3 substrates by ion beam assisted deposition. Influence of low energy Ar ion beam bombardment on the residual stress and resistivity of the Al/Ti films was investigated. It was found that the residual stress of the Al/Ti films varied from tensile to compressive with increases in ion energy or flux. The films fabricated at 0.5 keV and 3 μA/cm 2 possessed zero residual stress. An increase in the compressive stress resulted in a decrease in resistivity. By controlling the ion incident energy and flux, we were able to control the film stress and resistivity that were related to the reliability of SAW devices.

Nanostructuring polymers by soft lithography templates realized via ion sputtering

We demonstrate that a combination of ion sputtering and soft lithography is an alternativeand effective way of nanostructuring soft matter. We create self-organized nanoscalestructures on a glass template by irradiating the surface with a defocused, low energy Arion beam. Capillary force lithography is then used to transfer the pattern, exploiting theglass transition of polymeric layers. In particular, we demonstrate the pattern transfer of aperiodic 150 nm ripple structure onto an organic compound. This new, unconventionalcombination is then a low-cost strategy that opens the way to a variety of applications inthe field of organic-based devices.

Ion bombardment-induced high orientation of Al/Ti films for surface acoustic wave device applications

Al/Ti films were deposited on 128° Y-X LiNbO3 substrates by electron-beam (e-beam) deposition. Low-energy Ar ion beam bombardment was employed during the Ti underlayer deposition. Influence of low-energy beam bombardment on the texture of Al/Ti films was investigated by x-ray diffraction (XRD) analysis. It was found that Al films deposited on Ar-ion bombarded Ti underlayers possessed excellent (111) texture. With the textured Al/Ti films, a 2.3-GHz range image-impedance connection surface acoustic wave (SAW) filter was successfully fabricated.

Influence of the low energy ion beam milling on the electrical properties of InSb

The paper presents preliminary results of the experiments performed to study the influence of low energy Ar ions on the electrical properties of p-InSb under ion beam milling. We demonstrate that this treatment causes the 2-layer structure with electron conductivity to emerge at the p-InSb surface. The first layer with low mobility electrons is created through the surface amorphisation by ion bombardment. The second layer with higher mobility electrons is a result of crystal lattice damages. The properties of the second layer are time-dependent that indicates the gradual relaxation of damages. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Molecular Dynamics Simulation of the Interaction of Low-Energy Ar and Xe Ions with Copper Clusters on a Graphite Surface

A molecular-dynamics simulation of sputtering of isolated clusters consisting of 13, 27, and 195 Cu atoms from the (0001) graphite surface by 200-eV Ar and Xe ions is carried out. The angular and energy parameters of sputtered Cu atoms and scattered ions are discussed.

Influence of Low Energy Ar Ion Irradiation Treatment on Surface Properties of Deposited Metal Thin Films

Influence of Low Energy Ar Ion Irradiation Treatment on Surface Properties of Deposited Metal Thin Films

2406 低エネルギーイオン照射による金属薄膜の機械特性の改善(J22-2 材料特性計測とマイクロ機構,J22 マイクロメカトロニクス,2005年度年次大会)

A method of improving mechanical properties of Nickel (Ni) thin films was proposed in this study. Ni thin films were electroplated on the Silicon (Si) substrate. The film with which some kinds of film thickness differs was formed, and it investigated about the difference in the influence of low energy Ar ion irradiation. Irradiation conditions were Ar ion acceleration voltage 30 V, ion current density 0.15mA/cm^2 and irradiation time 10 minutes. Young modulus of Ni thin film which was electroplating time is 5 min were increased by the irradiation, but Ni thin film which was electroplating time is 20 min is not increased. It is found that the irradiation effect changes with crystalline state of film before the irradiation.

A molecular dynamics model for the Coulomb explosion

The impact of positively charged Arn+ ions, n=1,4,8, incident normally on the (100) surface of NaCl is studied by Molecular Dynamics (MD) simulations for energies up to 1keV. The model assumes fixed charges on the ions and the effect of projectile charge is investigated as a function of energy. It is shown that there is a significant enhancement in the sputtering yield at low impact energies due to the attachment of Cl ions to the impacting Ar, which is subsequently ejected from the lattice. The low energy Ar ions can also experience acceleration towards the NaCl crystal due to Coulombic attraction. At energies greater than a few hundred eV the Ar ions implant within the crystal which accommodates the extra charge from these ions. As a result the sputtering yield from the initial impact is reduced but as the dose increases, the yield rises as Na+ ions are preferentially ejected from the lattice. A large proportion of the ejected material is in the form of clusters.

Alignment of liquid crystal on a polyimide surface exposed to an Ar ion beam

In this paper properties of nematic liquid crystals aligned on polyimide surfaces exposed to a low-energy Ar ion beam are investigated. We studied how the pretilt angle of a liquid crystal cell is affected by ion-beam conditions, such as the energy of the incident ions, the angle of incidence, and the exposure time. X-ray photoelectron spectroscopy data indicate that ion-beam exposure changes the chemical bonding states of the polyimide surface, which may be one of the main causes of anisotropic liquid crystal alignment. We also found that twisted-nematic cells fabricated by the ion-beam alignment method have the voltage holding time enough for application to thin-film-transistor liquid crystal displays.

Core-level photoemission and near-edge x-ray absorption fine-structure studies of GaN surface under low-energy ion bombardment

We have investigated compositional changes on GaN surfaces under low-energy Ar ion bombardment using synchrotron-based high-resolution core-level photoemission measurements and near-edge x-ray absorption fine-structure (NEXAFS) spectroscopy. The low-energy ion bombardment of GaN produces a Ga-rich surface layer which transforms into a metallic Ga layer at higher bombarding energies. At the same time, the photoemission spectra around the N 1s core level reveal the presence of both uncoordinated nitrogen and nitrogen interstitials, which we have analyzed in more detail by x-ray absorption measurements at the N K-edge. We have proposed a mechanism for the relocation and loss of nitrogen during ion bombardment, in agreement with some recent experimental and theoretical studies of defect formation in GaN. We have also demonstrated that photoemission spectroscopy and NEXAFS provide a powerful combination for studying compositional changes and the creation of point defects at GaN surface.

Postgrowth Irradiation of Hydrogenated Amorphous Carbon thin Films by Low-Energy Ion Beam

Liquid crystal (LC) alignment property was investigated on hydrogenated amorphous carbon (a-C:H) thin films. a-C:H thin films were deposited by a remote plasma-enhanced chemical vapor deposition (RPECVD) method with C2H2 and He gases. The surface property of a-C:H thin films was controlled by low-energy Ar ion beams. Ion beam irradiation results in the decrease in optical band gap and transmittance, and the increase in the ID/IG ratio of a-C:H thin films. LC alignment was generated by ion beam irradiation on the surface of a-C:H thin films. LC alignment property was affected by ion-beam-induced anisotropic sp2 structures on the surface of a-C:H thin films.

Improvement of adhesion between plastic substrates and antireflection layers by ion-assisted reaction

Enhanced adhesion was observed between antireflection (AR) layers and polycarbonate (PC) substrates by irradiating the substrates with low-energy Ar ions in an O 2 environment. The AR coating consisted of SiO 2/TiO 2 multi-layers that were deposited by ion-beam sputtering. Improved adhesion was evidenced by a peeling test. Ion irradiation caused the surface characteristics to become more hydrophilic as measured by the water contact angle, which decreased from 76° to 18° after the ion irradiation. X-ray photoelectron spectroscopy analysis showed that the concentration of hydrophilic groups such as CO and CO increased as a result of the ion irradiation. The changes in surface roughness and in optical transmittance were negligible. The optical reflectance of the AR/PC structure was below 1% in the visible range.

Temperature and bias-voltage dependent transport in magnetic tunnel junctions with low energy Ar-ion irradiated barriers

Magnetic tunnel junctions $({\mathrm{Mn}}_{83}{\mathrm{Ir}}_{17}{/\mathrm{C}\mathrm{o}}_{70}{\mathrm{Fe}}_{30}{/\mathrm{A}\mathrm{l}\mathrm{O}}_{x}{/\mathrm{N}\mathrm{i}}_{80}{\mathrm{Fe}}_{20})$ are investigated, whose barriers are irradiated by a low energy ${\mathrm{Ar}}^{+}$ ion beam immediately after plasma oxidation of the aluminum film. The tunneling magnetoresistance prior to irradiation is up to 71% at 10 K. The ion irradiation increases the area resistance product up to a factor of 40 for ion energies up to 150 V. Further, the tunneling magnetoresistance and the dielectric stability is strongly reduced with increasing ion energies. From the analysis of the temperature and the voltage dependence of the tunneling magnetoresistance we conclude that this is due to an irradiation induced local change of the coordination of the Al and O atoms in the barrier. This leads to a thicker barrier and an increase of the precursor density for the dielectric breakdown. Further, an increase of hopping conductance through localized states is discussed. At energies larger than 150 V the resistance breaks down rapidly and the tunneling magnetoresistance vanishes completely. This results from the enhanced intermixing and sputtering of the barrier and electrode material. The results are also supported by investigations of the magnetic and the noise properties of the junctions and the Cu-${\mathrm{K}}_{\ensuremath{\alpha}}$-reflectivity of ${\mathrm{AlO}}_{x}$ multilayers.

Modification of Hg1−xCdxTe and related materials by ion-beam treatment

Modification of ternary Hg1−xCdxTe alloys with 0.21≤x≤0.55 and quaternary Hg1−y−zZnyCdzTe alloys by treatment with low-energy (E<800eV) Ar ions was studied. It is shown that for conductivity type conversion in Hg1−xCdxTe with 0.28≤x≤0.39, it is essential to use a neutralised ion beam. The observed dependence of the conversion depth on x agrees with the diffusion conversion model. The effect of self-compensation of intrinsic acceptor defects by intrinsic donors during the annealing prior to ion treatment is confirmed. This effect provides the possibility of controlling the carrier concentration in the n-region of p–n junctions fabricated by ion-beam treatment in vacancy-doped Hg1−xCdxTe.

Sputtering of SiC with low energy He and Ar ions under grazing incidence

The effect of low energy sputtering under grazing incidence upon the surface composition of SiC was investigated by Auger electron spectroscopy. The energy of the sputtering projectiles (He, Ar) varied from 200 to 1500 eV. Peak shifts to the higher energies with increasing argon ion energy were observed for all silicon and carbon Auger transitions. These shifts were explained by enhanced damage of the surface region within the sampling depth of the Auger electrons. The insensitivity of the Auger peak position to the energy of helium ions indicates that the damage state in the surface region does not change with the increasing energy of helium ions. An increase of the carbon concentration with the decrease of the argon energy was observed. The experiments were accompanied by dynamic Monte Carlo simulations by the TRIDYN code.

Influence of MgO surface conditions on the in-plane crystal orientation and critical current density of epitaxial YBCO films

Abstract The effect of magnesium oxide (MgO) surface conditions on in-plane grain orientation and critical current density of epitaxial YBa 2 Cu 3 O 7 (YBCO) films was systematically investigated. The MgO substrates were either “as received” or stored for some time, cleaned using different methods and lithographically prepared for our step-edge junction devices. The YBCO films were grown via reactive thermal co-evaporation by Theva, GmbH. The surface characterisation of MgO substrates was studied using X-ray photoelectron spectroscopy (XPS). The in-plane grain orientation of the YBCO films was studied by means of X-ray diffraction (XRD) φ -scan and the critical current density was measured for the XRD scanned samples. The surface condition of the MgO substrates was found to have a strong influence on the in-plane grain orientation and the critical current density of the YBCO films. The MgO substrates with a degraded or contaminated surface gave rise to 45° grain misorientation in YBCO films and reduced the critical current density. A final process step using a low energy Ar ion beam etching (IBE) of the MgO substrates prior to the YBCO film deposition was found effective in removing the in-plane grain misorientation and promoting the growth of perfectly aligned c -axis YBCO films.