Bombardment Of High-energy Particles Research Articles

Preparation of SiOx and SiOxNy Films on PEN using Facing Target Sputtering System

In this study, facing target sputtering(FTS) apparatus was fabricated and its process characteristics were investigated to estimate possibility to thin film passivation for optoelectronics. We report that the FTS system can prepare a high quality silicon oxide(SiOx) and silicon oxynitride(SiOxNy) films with a dense micro structure and an excellent uniformity less than 5%. In addition, the low temperature deposition is possible because the bombardment of high energy particles can be restrained. Thus, we suggest that the FTS is one of the suitable deposition techniques for the thin film passivtion layer and the gas barrier layer for optoelectronics.

Effect of tin concentrations on properties of indium tin oxide films deposited on PET substrate under various conditions

This study examined the effect of the Sn concentration on the electrical and mechanical properties of ITO films. ITO films, 150–160 nm in thickness, were deposited on polyethylene terephthalate (PET) substrates by DC magnetron sputtering under various deposition conditions using one of three different high density ITO targets (10 wt%, 7 wt% and 5 wt% SnO 2) without substrate heating. Deposition was carried out under the following conditions: DC power; total gas pressure; distance between target and substrate; and O 2 or H 2 addition ratio. The lowest resistivity of 3.19 × 10 −4 Ω cm and relatively small change in resistance in dynamic stress mode was obtained for the film deposited from an ITO target doped with 7wt% SnO 2. These results can be explained by the effect of the kinetic energy of sputtered atoms (In, Sn, O) and the bombardment of high energy particles (Ar 0, O −) arriving at the film surface during deposition.

Hydrogen Plasma Annealing of ZnO Films Deposited by Magnetron Sputtering with Third Electrode

Al doped zinc oxide (AZO) films were deposited using a radio frequency (rf) magnetron sputtering apparatus with a mesh grid electrode. Improvement of crystalline uniformity was achieved by the use of an appropriate negative grid bias to effectively suppress the bombardment of high-energy charged particles onto the film surface. The uniformity of the film's electronic properties, such as resistivity, carrier concentration and Hall mobility, was also improved using the sputtering method. Hydrogen plasma annealing was investigated to further decrease the resistivity of the ZnO films and the carrier concentration was increased by 1-2×1020cm-3 without decrease in the Hall mobility.

Influence of irradiation by 24 GeV protons on the properties of 4H–SiC radiation detectors

We had investigated the effects of the irradiation by 24 GeV protons with the doses from 10 13 cm − 2 up to 10 16 cm − 2 on the properties of radiation detectors fabricated as Schottky diodes on 4H–SiC. Numbers and activities of radionuclides and isotopes produced after the irradiation were analysed. Activities of 7Be and 22Na were found to be proportional to the irradiation dose and ranged from 1.3 up to 890 Bq and from 1.9 up to 950 Bq, respectively. The total amount of formed stable isotopes was from 1.2 × 10 11 cm − 2 up to 5.9 × 10 13 cm − 2 . 390 days after the irradiation the number of radiated electrons with different energies ranged from 1.0 up to 600 per second, respectively. The contact properties were investigated by means of the current–voltage analysis. At lower irradiation doses a slight decrease of the effective potential barrier height from about 0.74 eV down to < 0.7 eV took place. The reverse current of the diodes grew by up to one order of magnitude. At the doses above 3 × 10 15 cm − 2 opposite changes were observed. Irradiation by up to 1 × 10 16 protons/cm − 2 , resulted in the increase of the potential barrier height up to ∼ 0.85 eV, followed by the drop of the reverse current by up to two orders of magnitude. The observed effects were explained by the appearance of the disordered material structure because of the high-energy particle bombardment.

Transparent Conductive Thin Film for Top Emitting Organic Light Emitting Diodes by Sputtering Method

The indium tin oxide (ITO) cathode electrode of top emitting organic light emitting diodes (TOLEDs) was deposited by facing targets sputtering (FTS) method which can deposit thin films with low substrate damage. And it also use a plasma-free sputtering method in which substrate is located apart from plasma. So the temperature increase of substrate due to the bombardment of high-energy particles can be restrained. The ITO thin film which is a transparent electrode was deposited on the cell (Mg:Ag/LiF/EML/HTL/ITO) using two magnetic field such as concentrated magnetic field type and distributed magnetic field type, respectively. Also, the ITO thin films were deposited by sputtering current at working gas (Ar:O2 mixture gas) pressure 1 mTorr. Electrical and optical properties of ITO thin films which deposited on amorphous glass were measured and current–voltage (I–V) characteristics of ITO thin film on the cell were measured. In the results, the leakage-current density of ITO/cell prepared at concentrated magnetic filed type and distribution magnetic filed type showed about 1×10-3 mA/cm2 at -6 V and 1×10-5 mA/cm2 at -6 V, respectively.

Damage-Less Sputter Depositions by Plasma Charge Trap for Metal Gate Technologies

Damage-free sputter deposition process has been developed for metal gate complementary metal-oxide-semiconductor technology. A plasma charge trap (PCT) was introduced in order to eliminate high-energy particle bombardment during sputter deposition processes. Molybdenum (Mo)-gated PMOSFETs were fabricated using a conventional gate-first process. It is shown that the PCT technology yields excellent characteristics in current drivability, as well as in gate oxide integrity (GOI) such as gate leakage current and charge-to-breakdown (Q/sub BD/). The metal gate was also applied to a nonvolatile memory (NVM), which would require most stringent damage control, and good retention characteristics were demonstrated.

Molybdenum Gate Technology for Ultrathin-Body MOSFETs and FinFETs

Damage-free sputter deposition and highly selective dry-etch processes have been developed for molybdenum (Mo) metal gate technology, for application to fully depleted silicon-on-insulator ( devices such as the ultrathin body (UTB) MOSFET and double-gate FinFET. A plasma charge trap effectively eliminates high-energy particle bombardment during Mo sputtering; hence the gate-dielectric integrity (TDDB, Q/sub BD/) is significantly improved and the field-effect mobility in Mo-gated MOSFETs follows the universal mobility curve. The effects of etch process parameters such as chlorine (Cl/sub 2/) and oxygen (O/sub 2/) gas flow rate, and source and bias radio frequence powers, were investigated in order to optimize the Mo etch rate and selectivity to SiO/sub 2/. A highly selective etch process was successfully applied to pattern Mo gate electrodes for UTB MOSFETs and FinFETs without leaving any residue or stringers. Measured electrical characteristics and physical analysis results are discussed.

Crystallinity of Gallium-Doped Zinc Oxide Films Deposited by DC Magnetron Sputtering Using Ar, Ne or Kr Gas

Gallium-doped zinc oxide (GZO) films were deposited at RT by dc planar magnetron sputtering under various total gas pressures (Ptot) ranging from 0.25 Pa to 2.5 Pa using Ar as the sputtering gas and a GZO ceramic oxide target. The GZO films showed highest crystallinity at Ptot = 2.0 Pa and showed clear degradation at a lower or higher Ptot. For a comparative study, Ne or Kr was also used as a sputtering gas. The mechanisms of degradation were investigated, considering the effects of bombardment of high-energy particles on the growing film surface and the energy of sputtered particles, where kinetic energies of these particles were estimated by Monte Carlo simulation. It was shown that sputtered particles lost sufficient energy for surface migration to form a crystalline structure at a higher Ptot. The high-energy neutrals of the sputtering gas (Ar0, Ne0, and Kr0) which recoiled from the target surface should be primarily responsible for the structural damage in the film at a lower pressure.

New sputter-deposition processes for the formation of thin films with desired structure for magnetic recording

Two new sputter-deposition techniques, low voltage sputtering (LVS) and kinetic energy controlled particle deposition (KECD), are proposed to obtain a thin film with the desired microstructure. The LVS, RF–DC coupled magnetron sputtering with RF frequency above 30 MHz, is useful for sputtering at a sputtering voltage below 100 V and has a reasonable deposition rate. Indium tin oxide (ITO), Ti and CoCrTa films were deposited by using the LVS. Compared with conventional sputtering, LVS is effective in reducing high-energy particle bombardment of film surfaces during sputtering, which results in the formation of films with much smoother surfaces, although crystallization in the film is suppressed. On the other hand, KECD can control the kinetic energy and incidence angles of the depositing particles on the substrate. With KECD, it was confirmed that crystal growth is suppressed as the kinetic energy decreases in ITO film and the crystal orientation of Ti film depends remarkably on the kinetic energy of the deposition particles. Films with extremely smooth surface are obtained by KECD.

その場観察・計測技術 １ 高エネルギー粒子照射下の金属疲労挙動

その場観察・計測技術 １ 高エネルギー粒子照射下の金属疲労挙動

Thin film properties by facing targets sputtering system

In this study, film thickness distribution and c-axis crystalline orientation of deposited thin films were studied after preparing Co–Cr thin films, a promising ultra-high density perpendicular magnetic recording media, with a facing targets sputtering (FTS) apparatus. Electrical discharge characteristics needed for the optimum operation of sputter device was also studied in order to prepare thin films of superior c-axis crystalline orientation with FTS method (apparatus) in which thin film of fine quality can be formed because temperature increase of substrate due to the bombardment of high-energy particles can be restrained. As a result of the study, it is confirmed that the FTS method can give stable working under broad magnetic field and range of gas pressure and stable electrical discharge under low Ar gas pressure. Film thickness of prepared thin film shows fairy regular distribution and could obtain good thin films whose dispersion angle of c-axis crystalline orientation is about 3.5°.

Performance improvement of CIGS-based modules by depositing high-quality Ga-doped ZnO windows with magnetron sputtering

Improvement of the performance of Cu(InGa)Se 2 (CIGS)-based thin film submodules by depositing high-quality ZnO:Ga (GZO) window layers with sputtering method is performed to aim for establishing deposition technology of GZO windows of CIGS submodules. In order to reduce damage onto CIGS absorber/Zn(O,S,OH) x buffer interface due to the bombardment of high-energy particles during DC sputtering process of GZO window layers, growth of multilayered GZO window layers is developed. By using RF/DC/DC sputtered GZO window layers instead of the conventional DC sputtered GZO window layers, fill factor (FF) and conversion efficiency are increased over 10%. Increasing short-circuit current density ( J sc) of CIGS submodules is also investigated by improving the transparency of GZO window layers. Furthermore, damp heat test of the sputtered GZO films is carried out, and it is found that the GZO films have good stability of electrical properties.

Reactive magnetron sputtering of indium tin oxide films on acrylics – morphology and bonding state

Indium tin oxide (ITO) films were deposited on acrylics by low temperature reactive magnetron sputtering. The effects of oxygen flow and bias voltage on the microstructure, surface morphology and bonding state of films were evaluated. In this investigation, X-ray photoelectron spectroscopy, X-ray diffraction, Atomic force microscope were used. It was found that the grain size of ITO films increased and surface roughness decreased with the increase of oxygen flow rate. The XPS spectra of In 3d and Sn 3d indicated that the oxygen flow had little effect on the binding energy of ITO films. The relative strength of O 2− II increased, while that of O 2− I decreased with increasing oxygen flow rate. The grain size increased with the bias voltage. However, at a maximum voltage of −90 V fine grains were detected due to the formation of numerous nuclei resulting from bombardment of high energy particles. The bias voltage had little effect on the bonding state of In, Sn and O ions.

Electrical and Structural Properties of Tin-Doped Indium Oxide Films Deposited by DC Sputtering at Room Temperature

Tin-doped indium oxide (ITO) films were deposited on soda-lime glass plates without substrate heating by dc magnetron sputtering. Crystallinity and electrical properties of the films were investigated by X-ray diffraction and Hall-effect measurements, which showed clear dependence on target–substrate distance (T–S) and on total gas pressure (Ptot) during deposition. Degradation in crystallinity was observed at relatively high or low Ptot, where the upper or lower Ptot level for depositing films with high crystallinity was increased with decreasing T–S. Based on a hard sphere collision model, the crystallinity of the films was considered to be strongly affected both by the kinetic energy of sputtered In (or Sn) particles and by the bombardment of high energy particles arriving at the growing film surface. The former could enhance the crystallinity, whereas the latter degraded both the crystallinity and conductivity. Such degradation in electrical properties was mainly due to a decrease in carrier density.

Computer simulation of particle bombardment of alkanethiol chains adsorbed on gold surface

Molecular dynamics (MD) simulations have been used to model the high energy particle bombardment process of deuteated alkanethiol chains chemisorbed on a gold surface. The model involves the use of sophisticated many-body potential energy functions to represent the chemical interactions among atoms. We have investigated the dependence of the fragmentation pattern upon two different angles of the Ar incidents, namely in the direction parallel (−35°) and orthogonal (+55°) to the tilt chain. It is found that surface thiol chains are likely to be hit for Ar at +55° so that more fragmentation occurs. In contrast, collisions with substrate atoms are more likely when Ar impacts at −35°. This leads to less fragmentation and more molecular species are sputtered. We also found that hydrocarbon fragments such as C2D5, C3D7, and C4D9 are prominent for both angles of incidence although the suggested mechanisms leading to their ejections are different.

Computer Simulation of Sputter-Deposition Processes

Sputter deposition process was investigated by computer simulation in order to clarify the effects of sputter-deposition parameters (sputtering gas pressure, substrate temperature, and high-energy particle bombardment of the film surface) on the microstructure of the film. Changes in sputtering gas pressure lead not only to changes in the distributions of the incidence angles and energy distribution of deposition particles, but also to changes in the film composition. The gas pressure dependence of the film composition in magnetron sputtering differs significantly from that in facing target sputtering. The surface migration of the deposited atoms due to thermally activated hopping leads to a considerable increase in film density. The bombardment of the film surface by high energy particles induces a significant migration of the deposited atoms and results in a dense structure.

Magnetron facing target sputtering system for fabricating single-crystal films

This paper introduces a magnetron facing target sputtering (FTS) system in detail. The facing arranged targets, the especially applied magnetic field, and the substrate placed outside the plasma region make this kind of apparatus convenient to fabricate metallic films free of the bombardment of high-energy particles. Large-area uniformity, high and uniform deposition rate, low substrate temperature, relatively free of inert incorporation and composition deviation are achieved. Compared with the conventional magnetron sputtering system, the FTS is of great advantage for sputtering ferromagnetic materials. By using the FTS system, we have been able to obtain iron and Fe 16N 2 single-crystal films.

Pulsar Death at an Advanced Age

Not long ago Rankin (1990) presented strong evidence in favor of a low altitude (r≈R*) dipole geometry for the site of the core component of pulsar radio emission. Arons (1993) gave evidence that spun up millisecond pulsars must have a substantially dipolar large scale field at low altitute. Electron-positron pair creation at low altitude above the polar caps has long been hypothesized to be an essential ingredient of pulsar radio emission. If so, all observed pulsars must lie in the region ofP−Ṗspace where polar cap acceleration has sufficient vigor to lead to the copious pair production. Yet, to date, allinternally consistenttheories of polar cap pair creation have required hypothesizing a large scale (eg, quadrupole) component of the magnetic field with strength comparable to that of the dipole, in contradiction with the evidence in favor of an apparently dipolar low altitude geometry. The internally consistent theories also violate other observational constraints. The discharge models of Ruderman and Sutherland (1975), Gurevich and Istomin (1985), and Jones (1977, 1978, 1979) all accelerate equal, counterstreaming flows of electrons and positrons, thus putting one half of the particle acceleration energy into high energy particle and photon bombardment of the polar caps. The heating causes pulsed thermal X-ray emission from hot spots in excess of what is seen (Ogelman 1993). While the Arons and Scharlemann (1979) model does not have this problem, since the space charge in the starvation zone above the polar cap is made up almost entirely of the outbound beam, in star centered dipole geometry it dramatically fails to account for pulsar emission over most of theP−Ṗdiagram and predicts radio polarization variations in contradiction to the observations (Narayan and Vivekanand 1982).

A microscopic view of particle bombardment of organic films

The high energy particle bombardment of molecular films adsorbed upon a metal substrate has been investigated via molecular dynamics computer simulations with an empirical many-body potential function constructed for studying reactive dynamics. These calculations identify lateral motion of fragments in the overlayer as giving rise to fragmentation and direct abstraction type reactions. In addition, the importance of substrate mass for particle ejection is identified. These concepts are discussed in detail and experiments are proposed to test these ideas.

Molecular Dynamics Simulations of Reactions between Molecules: High-Energy Particle Bombardment of Organic Films

High energy bombardment mass spectrometric techniques are becoming ever more important for organic and biological samples. Before the molecule can be detected, though, it must first be ejected. The authors have developed a molecular dynamics prescription for examining the fundamental processes important for the ejection of organic molecules during the particle bombardment event. The major advance here over previous simulations is the use of an empirical many-body potential energy function constructed for studying reactive dynamics. Specifically, bonds can be broken and reformed. For the first time, one can examine the possibility of reactions among the organic molecules. As an initial test system, the authors have investigated the 500 eV Ar bombardment of ethylidyne, C{sub 2}H{sub 3}, on Pt (111). This specific system has been studied experimentally by White and co-workers using SIMS. The authors have modeled both 0.25 and 0.50 monolayer ethylidyne coverage in order to test density effects. They find that approximately 80% of the ejected hydrocarbon species originate from a single C{sub 2}H{sub 3} adsorbate, while the others result from reactions between two C{sub 2}H{sub 3} adsorbates. A study of the internal energies of all of the ejected hydrocarbon aggregates reveals that those originating from a single C{submore » 2}H{sub 3} adsorbate are generally stable to any further fragmentation or rearrangement. Examples of common ejection mechanisms for species which originate from a single adsorbate, such as CH{sub 3}, C{sub 2}H{sub 3}, HCCH, and those which originate from more than one adsorbate, such as CH{sub 4} and H{sub 2} will be discussed.« less