Oxygen Ion Beam Bombardment Research Articles

Influence of different stoichiometric Cr-oxides created via oxygen ion-beam bombardment on the magnetism of the NiFe/Cr-oxide exchange-biased systems

In exchange-biased systems, antiferromagnetic Cr2O3 has drawn intensive attention because of its highly anisotropic structure. However, other Cr-oxide phases can be formed during fabrication. The influence of different stoichiometric Cr-oxides on the magnetism of the NiFe/Cr-oxide bilayers was studied. We find that paramagnetic CrO3 grains could promote the formation of domain states in the Cr-oxide layer by magnetically isolating antiferromagnetic domains. These domain states gave rise to an excess of irreversible magnetic moments at the NiFe/Cr-oxide interface, causing a nontrivial increase in the exchange bias. The presence of ferromagnetic CrO2 grains in the Cr-oxide layer introduced abundant magnetic disorders. These magnetic disorders acted as pinning sites and impeded the domain-wall motion, which resulted in an increase of the coercivity. These results indicate that the magnetism of the NiFe/Cr-oxide bilayers can be remarkably affected by different Cr-oxide phases, enabling control of both the coercivity and exchange bias and providing a possible route to improve the performance of exchange-biased devices.

Effect of oxygen ion beam bombardment on depth resolved hydrogen distribution in stoichiometric alumina thin films, deposited by e-beam evaporation

Effect of oxygen ion beam bombardment on the hydrogen impurity distribution (as a function of depth) in alumina thin films is discussed. It is shown that the bombardment of oxygen ion beam during electron beam evaporation significantly decreases the hydrogen content in the films. The observed peak of hydrogen distribution at the silica alumina interface is explained on the basis of morphological changes happening to the silica alumina interface due to the oxygen ion beam bombardment. It is also shown that stoichiometry of these films, irrespective of the oxygen ion beam energy, remains same as that of sapphire crystal.

The effect of oxygen ion beam bombardment on the properties of tin indium oxide/polyethylene terephthalate complex

The tin indium oxide (ITO) films were deposited onto the polyethylene terephthalate (PET) surface that has been bombarded by an O ion beam. The variation of the O bombardment time resulted in the production of ITO/PET complex with different properties. Characterization by four-point probe measurement after the bending fatigue test showed that the adhesion property of the ITO/PET complex could be improved by the increase of O bombardment time while little change of electrical resistivity was observed. Scanning electron microscopy results showed that after the bending fatigue test, the nano scale seams and micro scale trenches appeared at the surface of the ITO/PET complex. The former was only the cracks of ITO film, which has little influence on the continuity and electrical resistivity of ITO film. On the contrary, the micro scale trenches were caused by the peeling off of ITO chips at the cracks, which mainly influenced the continuity and electrical resistivity of ITO film. With the increase of O bombardment time, the number and length of the micro scale trenches decreased. X-ray photoelectron spectrometry characterization showed that with the increase of O bombardment time, parts of the methylene C bonds were transformed into CO bonds, which could be broken to form COIn(Sn) bonds at the initial stage of ITO film growth. By these COIn(Sn) crosslink bonds, the ITO film could adhere well onto the PET and the ITO/PET complex display better anti-bending fatigue property. Finally, in the context of the application of the ITO/PET complex as a flexible electrode substrate, the present work reveals a simple way to crosslink them, as well as the physicochemical mechanism happening at the interface of complex.

Facet and ripple formations on single crystal diamond tools machined by low energy oxygen ion beam

In this paper, we have studied the facet and ripple formation on a hemispherical diamond stylus by low energy (0.3–3.0 keV) oxygen ion beam bombardment at different ion incidence angle. The sputtered stylus was observed by SEM. From SEM image, we measured the ion incidence angle θ max where the etching rate is maximum and compared them with the theoretical values of θ max derived from Witcomb formula. From experimentally and theoretically obtained values of θ max, we measured the facet angles of the processed hemispherical diamond stylus. Our result shows increasing discrepancy between theoretical and experimental values of both θ max and facet angle towards lower ion energy (< 2 keV) due to dominance of chemical sputtering over physical sputtering. From our observation we found a diamond stylus can be sharpened at 3 keV ion energy if the original apex angle is > 70°. We also observed surface morphology of the processed hemispherical diamond stylus machined by 0.3–3 keV oxygen ion beam at different tilted conditions. Our observation confirms the formation of ripple on the processed diamond stylus at higher angles of ion incidence. The ripple orientation at ion incidence 40°–60° processed by 3 keV oxygen ion beam is in well agreement with the predictions of linear BH model. However, ripples were not observed at near normal incidence and grazing incidence in contrast to BH model. In order to avoid ripple formation, the diamond stylus needs to be processed within the region of low ion incidence angles. The smoothing region is broader in the low ion energy range but some etch pits are seen to form in this region due to chemical sputtering of the impurities present in the diamond stylus.

Internal energy distribution change of sputtered Al atom under several hundreds of eV oxygen ion-beam bombardment by resonant laser ionization sputtered neutral mass spectroscopy

It is important to evaluate the internal energy of the sputtered neutral particles to optimize their resonant ionization efficiency. In this study, the internal energy of the sputtered Al atom, especially the ground state P1∕22 and the lowest-lying excited state P3∕22 (112cm−1), was monitored by using resonant laser postionization sputtered neutral mass spectrometry. The results of the authors showed the density of the ground state of the sputtered Al atom drastically decreased due to surface oxidation, as well as the enhancement of the secondary Al+ yield.

Fabrication of antireflection structures on glassy carbon surfaces using electron beam lithography and oxygen dry etching

Glassy carbon (GC) substrate was used for the fabrication of antireflection (AR) structures as this material has high thermal stability, thereby being suitable for a quartz mold. In order to fabricate the AR structures on the GC surface, electron beam lithography (EBL) and oxygen dry etching were carried out. EBL was used for the fabrication of submicron order mask patterns on the GC surface. By oxygen ion beam bombardment, the GC surface was sharpened and conical-shaped structures were fabricated. Almost zero reflection was observed on this surface in the visible light region.

Surface characteristics and adhesive strengths of metal on O 2 ion beam treated polyimide substrate

A polyimide surface was modified by oxygen ion beam bombardment to improve its adhesion to a subsequently deposited NiCr (nickel-chromium alloy) overlayer. The changes in the chemical composition, morphology and adhesion property of the modified polyimide surface were characterized by X-ray photoelectron spectroscopy, scanning electron microscopy, atomic force microscopy and the 90° peel test. The results show that the oxygen ion beam treatment of the polyimide induces the formation of oxygen functional groups and the rearrangement of the imide groups in the polyimide substrate film. An increase in its surface roughness resulted in a substantial improvement in the adhesion strength between the polyimide and NiCr overlayer. The improved adhesion strength, however, was found to be reduced after thermal aging at 150 °C for 168 hrs, which was attributed to the thermal oxidative degradation of the polyimide at the interface. We also observed that the ion beam treatment was effective in retarding the adhesion loss caused by the thermal aging.

Ion and electron bombardment-related ion emission during the analysis of diamond using secondary ion mass spectrometry

In recent years, the ability to grow single crystal layers of both doped and pure diamonds has improved, and devices for applications in high power electronics and microelectronics are being developed, most of them based on boron doped diamond. In this work, convoluted angular and energy spectra (so-called secondary ion mass spectrometry energy spectra) have been measured for B+11, C+12, O+16, CO+ and CO2+ ions ejected from a single crystal boron doped diamond layer under ultralow energy oxygen and electron beam bombardment. A low energy tail was observed in the C+12, CO+, and CO2+ signals, corresponding to ions produced in the gas phase. Changing the bombardment conditions, we have identified interaction with the electron beam as the main ionization mechanism. In the case of C+12 it appears that the gas phase ions are produced by electron stimulated desorption and postionization of surface species created by the oxygen beam. We have detected high signals for CO+ and CO2+ ionized in the gas phase, which supports a mechanism previously suggested to explain the anomalously fast diamond erosion under oxygen ion beam bombardment. We also observe that some species appearing in the mass spectrum are produced by electron stimulated desorption and this needs to be remembered when analyzing these on insulating diamond with charge compensation.

In situ XPS and SIMS analysis of O2+ beam‐induced silicon oxidation

AbstractThe chemical composition variation of silicon under 4 keV O2+ ion beam bombardment at different incident angles was studied by in situ small‐area XPS. The changes in secondary ion profile (30Si+, 44SiO+, 56Si2+, 60SiO2+) during oxygen ion beam bombardment also have been monitored. We present a direct correlation of the changes in secondary ion depth profile with surface composition during sputtering. Evolution of the secondary ion profile obtained from SIMS shows similar trends with variation of oxygen concentration in the crater surface measured by XPS. It is shown that when the oxygen ion beam incidence angle is &lt; 40° silicon dioxide is the dominant species on the crater surface and the matrix ion species ratio (MISR) value for 44SiO+/56Si2+ is higher than for 30Si+/56Si2+. For incidence angles of &gt;40°, the formation of sub‐oxide is favoured and thus the MISR value for 44SiO+/56Si2+ is lower than for 30Si+/56Si2. At 40° bombardment there are similar amounts of SiO2 and sub‐oxides present on the crater surface and the MISR values for 44SiO+/56Si2+ and 30Si+/56Si2+ are also similar. Copyright © 2004 John Wiley &amp; Sons, Ltd.

Evaporation and ion assisted deposition of HfO2 coatings: Some key points for high power laser applications

Optical interference filters made by layers of optical coatings are used to shape and transport laser beams. If a defect is present in the stack (cosmetic defect, stoichiometry defect, absorption band…), and high laser power density is reached, a strong energy into the material can be deposited involving the destruction of the coatings (either by melting or mechanical failure). One of the key methods to achieve high performance coatings is to reduce such defects as much as possible. Hafnia (HfO2) coatings are undoubtedly one of the most successful materials for high power laser applications. Associated with a low index material such as silica, high laser induced damage threshold (LIDT) interference filters can be achieved. Hafnia is often the LIDT limiting factor. During the evaporation HfO2 particles create buried defects in the deposited material. These defects are sources of the coating damage during laser irradiation. To avoid this phenomenon we have evaporated metallic hafnium that was oxidized by oxygen inlet into the vacuum chamber or use an oxygen ion beam bombardment during the film growth. Argon or, better, xenon ions in the beam produced densities as high as 99% of the bulk, with low water content, and an improved optical transmission in the mid infrared window. This article deals with the optimization of such a deposition process regarding coating density, mechanical stresses, and optical properties (optical absorption). Films deposited by HfO2 evaporation are compared especially using photothermal mapping. The stoichiometry of the defects determined thanks to localized Auger spectroscopy clearly indicates how injurious such defects could be for high laser flux applications. Finally, laser damage thresholds of the films at 1.06 μm are measured and possible damage mechanism discussed.

Ion beam sputtering of SnO 2 with low energy oxygen ion beams

The effects of oxygen ion bombardment on tin oxide films during ion beam sputtering of SnO 2 targets at room temperature have been systematically investigated with the variation in oxygen ion beam energy in the range of 0–150 eV directed onto the growing film. The results have been compared with those of ion beam sputtering of SnO 2 targets without oxygen ion beam bombardment. Chemical, compositional and structural analyses have been performed on these films. The results indicate that, by the use of oxygen ion-beams with low energy in ion beam sputtering of SnO 2 targets, stoichiometric and crystalline stannic oxide films can be obtained on Si(100) substrates at room temperature and that the crystallographic structure and the phase of the films are functions of the energy of the oxygen ion beam.

Stoichiometry changes during low energy oxygen bombardment

A basic understanding of the sputter induced artifacts during low energy oxygen ion beam bombardment is of great importance for a correct evaluation of the results of suptter depth profiling in SIMS. In this paper the sputter depth profiling of Si, CoSi 2 and TiSi 2 under normal oxygen bombardment has been investigated. With the combined sputter/RBS set-up and in combination with ex-situ XPS measurements, the oxidation and near-surface compositional changes in the transient region have been explained.

A quantitative study of copper segregation in silicon under oxygen ion beam bombardment using SIMS

Abstract The segregation of Cu in Si under oxygen ion bombardment has been investigated using secondary ion mass spectrometry (SIMS). The decay length of the Cu signal observed when depth profiling a Cu implanted (100) n-type Si wafer has been measured as a function of the angle of incidence and the primary beam energy. The decay length at normal incidence is found to vary linearly as a function of energy, between 2.5 and 14 keV O 2 atom. The dependence with angle was measured at 14 keV O 2 atom and is found to be much stronger. From normal incidence to 20° the decay length decreases rapidly from 3000 to 311 nm. From 20 to 30° another order of magnitude drop in decay length is observed with most of the drop occurring between 20 and 25°. Past 30° the decay length is almost constant with a value of approximately 32 nm. These changes in decay length with energy and angle are discussed with reference to the nature of the altered layer formed under oxygen bombardment of Si.

Multi-ion-beam reactive sputter deposition of ferroelectric Pb(Zr,Ti)O3 thin films

A multi-ion-beam reactive sputter (MIBERS) deposition technique was devised to grow ferroelectric lead zirconate titanate (PZT) thin films of different compositions (Zr/Ti ratios of 50/50 and 56/44) from individual metal targets of Pb, Zr, and Ti. This technique offers a highly controllable deposition process allowing excellent uniformity in composition and thickness over a large area (7.5 cm diameter) on a reproducible basis. The PZT films were deposited on a variety of unheated substrates and annealed by two different techniques, rapid thermal annealing and conventional furnace annealing. Both techniques induced a perovskite phase with good morphology. The effect of the excess Pb content was observed in terms of the crystallization and morphology. It was seen that the presence of excess Pb tends to enhance perovskite phase formation but degrades the morphology. The effect of the substrates was observed in terms of crystallization and orientation. A low-energy oxygen ion beam was employed to modify the film growth. Secondary-ion bombardment seems to be a promising approach to optimize the film quality as it showed a variety of effects such as enhancing crystallization, inducing preferred orientation, and improving the film morphology. The present MIBERS-grown PZT films showed fairly high dielectric constants, about 850 for PZT (50/50) and about 1150 for PZT (56/44), and low dielectric losses. Ferroelectricity of these films was established with the values of the remnant polarization and the coercive field for PZT (50/50) of 23 μC/cm2 and 80 kV/cm and for PZT (56/44) of 20 μC/cm2 and 60 kV/cm, respectively. The low-energy oxygen ion-beam bombardment during the growth of PZT (50/50) films caused an increase in the dielectric constant to about 1000, reduction in the dissipation factor to 0.02, increase in the remnant polarization to about 26 μC/cm2, and decrease in the coercive field to about 60 kV/cm. The C-V characteristics of PZT (50/50) films in a metal-ferroelectric-metal configuration also indicated a clear dielectric polarization hysteresis.

Surface damage of PET sheet in rf bias ion plating

Surface damage of PET substrates caused by ion bombardment in ion plating has been studied by ESCA. It was found that in rf bias ion plating, even brief (2 s) bombardment prior to deposition causes very substantial damage of the plastic surface and the films are formed on that modified surface. The damaged layer is mainly composed of free carbons or hydrocarbons produced by the decomposition of PET, although its structure depends on bombardment conditions. Small amounts of new carbon-oxygen species are also produced, which are a characteristic feature of ion plating. The interactions between the plasma and the polymer surface are discussed, and compared with the results of in situ oxygen ion beam bombardment and electron beam bombardment experiments carried out in the ESCA spectrometer.

Potassium and titaniumKX-ray de-excitation induced by ion bombardment

KX-ray de-excitation spectra have been produced for K and Ti by proton, alpha and oxygen ion beam bombardment. These spectra have been measured with a crystal spectrometer of resolution (FWHM) of 10 and 13 ev for theKα1,2 line in K and Ti respectively. The additional lines not found in the normal X-ray spectra are attributed to multiple inner shell ionization. The energy shifts and relative intensities of these lines are compared to theoretical predictions.