Effect of copper ions implantation on corrosion behavior of zircaloy-4 in 1 M H2SO4

In order to study the effect of copper ion implantation on the aqueous corrosion behavior, samples of zircaloy-4 were implanted with copper ions with fluences ranging from 1 × 10¹⁶ to 1 × 10¹⁷ ions/cm², using a metal vapor vacuum arc source (MEVVA) operated at an extraction voltage of 40 kV. The valence states and depth distributions of elements in the surface layer of the samples were analyzed by X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES), respectively. Glancing angle X-ray diffraction (GAXRD) was employed to examine the phase transformation due to the copper ion implantation. The potentiodynamic polarization technique was employed to evaluate the aqueous corrosion resistance of implanted zircaloy-4 in a 1 M H₂SO₄ solution. It was found that a significant improvement was achieved in the aqueous corrosion resistance of zircaloy-4 implanted with copper ions when the fluence is smaller than 5 × 10¹⁶ ions/cm². The corrosion resistance of implanted samples declined with increasing the fluence. Finally, the mechanism of the corrosion behavior of copper-implanted zircaloy-4 was discussed.     

Influence of titanium ions implantation on corrosion behavior of zirconium in 1 M H2SO4

In order to study the effect of titanium ion implantation on the aqueous corrosion behavior of zirconium, specimens were implanted with titanium ions with fluence ranging from 1 × 10¹⁶ to 1 × 10¹⁷ ions/cm², using a metal vapor vacuum arc (MEVVA) source at an extraction voltage of 40 kV. The valence states and depth distributions of elements in the surface layer of the samples were analyzed by X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES), respectively. The potentiodynamic polarization technique was employed to evaluate the aqueous corrosion resistance of implanted zirconium in a 1 M H₂SO₄ solution. It was found that a significant improvement was achieved in the aqueous corrosion resistance of zirconium implanted with titanium ions. The larger the fluence, the better is the corrosion resistance of implanted sample. Finally, the mechanism of the corrosion behavior of titanium-implanted zirconium was discussed.     

Annealing effects on structural, optical and electrical properties of e-beam evaporated CuIn0.5Ga0.5Te2 thin films

CuIn_0.5Ga_0.5Te₂ (CIGT) thin films have been prepared by e-beam evaporation from a single crystal powder synthesized by direct reaction of constituent elements in a stoichiometric proportion. Post-depositional annealing has been carried out at 300 and 350 °C. The compositions of the films were determined by energy dispersive X-ray analysis (EDXA) and it was found that there was a remarkable fluctuation in atomic percentage of the constituent elements following to the post-depositional annealing. X-ray diffraction analysis (XRD) has shown that as-grown films were amorphous in nature and turned into polycrystalline structure following to the annealing at 300 °C. The main peaks of CuIn_0.5Ga_0.5Te₂ and some minor peaks belonged to a binary phase Cu₂Te appeared after annealing at 300 °C, whereas for the films annealed at 350 °C single phase of the CuIn_0.5Ga_0.5Te₂ chalcopyrite structure was observed with the preferred orientation along the (1 1 2) plane. The effect of annealing on and near surface regions has been studied using X-ray photoelectron spectroscopy (XPS). The results indicated that there was a considerable variation in surface composition following to the annealing process. The transmission and reflection measurements have been carried out in the wavelength range of 200-1100 nm. The absorption coefficients of the films were found to be in the order of 10⁴ cm⁻¹ and optical band gaps were determined as 1.39, 1.43 and 1.47 eV for as-grown and films annealed at 300 and 350 °C, respectively. The temperature dependent conductivity and photoconductivity measurements have been performed in the temperature range of −73 to 157 °C and the room temperature resistivities were found to be around 3.4 × 10⁷ and 9.6 × 10⁶ (Ω cm) for the as-grown and annealed films at 350 °C, respectively.     

Composition dependent structural modification in relaxed Si1−xGex films by 100 MeV Au beam

We report the modification of molecular beam epitaxy grown strain-relaxed single crystalline Si_1−xGe_x layers for x=0.5 and 0.7 as a result of irradiation with 100 MeV Au ions at 80 K. The samples were structurally characterized by Rutherford backscattering spectrometry/channeling, transmission electron microscopy (TEM) and high-resolution X-ray diffraction before and after irradiation with fluences of 5×10¹⁰, 1×10¹¹ and 1×10¹² ions/cm², respectively. No track formation was detected in both the samples from TEM studies and finally, the crystalline to amorphous phase transformation at 1×10¹² ions/cm² was examined to be higher for Si_0.3Ge_0.7 layers compared to Si_0.5Ge_0.5 layers.     

SHI induced silicide formation and surface morphology at Co/Si system

Ion beam mixing is a useful technique to produce modifications at the surface and interface of the solid material. In the present work, ion beam induced modifications at Co/Si interface using 120 MeV Au-ion irradiation has been studied at ion fluences in the range of 10¹² to 10¹⁴ ions/cm² by secondary ion mass spectroscopy (SIMS) technique and calculated mixing efficiency at the interface. Silicide formation has been discussed on the basis of swift heavy ion (SHI) irradiation induced effects. Surface morphology and roughness of irradiated system with fluence 5 × 10¹³ and 1 × 10¹⁴ ions/cm² is studied by scanning tunneling microscopy (STM). Roughness of the surface shows marks of melting process and confirms the appearance of some pinholes in the reacted Co/Si system. Comparative study was also undertaken on annealed sample at 300 °C and then irradiated at a dose 1 × 10¹⁴ ions/cm².     

NbTi0.5Ni0.5O4 as anode compound material for SOFCs

NbTi_0.5Ni_0.5O₄ (NTNO) has been prepared using solid state synthesis and investigated as a potential anode material. The oxide form of NTNO has single phase rutile-type structure with tetragonal (P42/mnm) space group. The reduced form is a composite of nano-scaled particles of metallic Ni and Nb_1.33Ti_0.67O₄ phase. Reduced NTNO showed high electronic conductivity up to 280 S.cm^− 1 at 900 °C in reducing atmosphere, but suffers from low CTE equal to 3.78 10^− 6 K^− 1. Studies of NTNO as anode material were carried out in a three electrode - electrochemical half cell configuration under pure humidified H₂ at 900 °C using a 2 mm thick zirconia electrolyte and without any additional current collector material. The results show a reasonable series resistance (R_s) equal to 2.7 Ωcm² (about 50% higher than for metallic gold layers) indicating a good current collection performance for a 10 μm layer of material. The polarization resistance (R_p) was equal to 33 Ωcm² and is attributed to a poor density of three phase boundaries (TPB) and shortage of oxide ion conduction in the anode layer. The results show the potential of NTNO as an anode material, especially after optimization of the microstructure towards the increase of TPB length.     

Properties of K0.5Bi0.5TiO3 thin films deposited on different substrates

K_0.5Bi_0.5TiO₃ thin films were deposited on fused quartz, n-type Si(100) and Pt/TiO₂/SiO₂/Si substrates by repeated coating/dying cycles. X-ray diffraction analysis shows that the films annealed at 700 °C for 10 min present perovskite phase. Atomic force microscopy reveals that the surface morphology is smooth, the grain sizes of the films on Si(100) are quite larger than on fused quartz. The capacitance-voltage hysteresis loops at various sweeping speed are collected as are polarization types. The films in the ON and OFF states are relatively stable. The films also exhibit a hysteresis loop at an applied voltage of 4 V, with a remanent polarization of 9.3 μC/cm² and a coercive voltage of 2 V. The insulating property of negative bias voltage is better than that of positive bias voltage. The transmittance of the films is between 74 and 82% in the wavelength range of 200-2000 nm.     

Creation of nanoparticles and luminescence in Al2O3 crystal by Zn ion implantation

Single crystal α-Al₂O₃ wafers were implanted with 45 keV Zn ions up to a fluence of 1×10¹⁷ ions/cm², and were then subjected to furnace annealing in oxygen atmosphere at different temperatures. Various techniques have been applied to study the creation of nanoparticles (NPs), defects and their thermal evolutions, as well as their effects on optical properties of Al₂O₃. Our results clearly show that Zn NPs have been synthesized in the as-implanted sample and they begin to be oxidized at 500 °C. Two broad photoluminescence bands appear in the Zn ion-implanted samples and their intensities depend on the annealing temperatures. The results have been interpreted in view of creation of the defects and NPs, Zn atoms diffusion as well as their thermal evolution during annealing.     

Low energy Ar-ion bombardment effects on the CeO2 surface

The structure and electronic properties of epitaxial grown CeO₂(1 1 1) thin films before and after Ar⁺ bombardment have been comprehensively studied with synchrotron radiation photoemission spectroscopy (SRPES). Ar⁺ bombardment of the surface causes a new emission appearing at 1.6 eV above the Fermi edge which is related to the localized Ce 4f¹ orbital in the reduced oxidation state Ce³⁺. Under the condition of the energy of Ar ions being 1 keV and a constant current density of 0.5 μA/cm², the intensity of the reduced state Ce³⁺ increases with increasing time of sputtering and reaches a constant value after 15 min sputtering, which corresponds to the surface being exposed to 2.8 × 10¹⁵ ions/cm². The reduction of CeO₂ is attributed to a preferential sputtering of oxygen from the surface. As a result, Ar⁺ bombardment leads to a gradual buildup of an, approximately 0.69 nm thick, sputtering altered layer. Our studies have demonstrated that Ar⁺ bombardment is an effective method for reducing CeO₂ to CeO_2−x and the degree of the reduction is related to the energy and amount of Ar ions been exposed to the CeO₂ surface.     

Structural and electrical properties of (Na0.85K0.15)0.5Bi0.5TiO3 thin films deposited on LaNiO3 and Pt bottom electrodes

(Na_0.85K_0.15)_0.5Bi_0.5TiO₃ thin films were deposited on LaNiO₃(LNO)/SiO₂/Si(1 0 0) and Pt/Ti/SiO₂/Si(1 0 0) substrates by metal-organic decomposition, and the effects of bottom electrodes LNO and Pt on the ferroelectric, dielectric and piezoelectric properties were investigated by ferroelectric tester, impedance analyzer and scanning probe microscopy, respectively. For the thin films deposited on LNO and Pt electrodes, the remnant polarization 2P_r are about 22.6 and 8.8 μC/cm² under 375 kV/cm, the dielectric constants 238 and 579 at 10 kHz, the dielectric losses 0.06 and 0.30 at 10 kHz, the statistic d_33eff values 95 and 81 pm/V. The improved piezoelectric properties could make (Na_1−xK_x)_0.5Bi_0.5TiO₃ thin film as a promising candidate for piezoelectric thin film devices.     

Luminescence studies on swift heavy ion irradiated nanocrystalline aluminum oxide

Pellets of nanocrystalline aluminum oxide synthesized by a combustion technique are irradiated with 120 MeV Au⁹⁺ ions for fluence in the range 5×10¹¹-1×10¹³ ions cm⁻². Two photoluminescence (PL) emissions, a prominent one with peak at ∼525 nm and a shoulder at ∼465 nm are observed in heat treated and Au⁹⁺ ion irradiated aluminum oxide. The 525 nm emission is attributed to F₂²⁺-centers. The PL intensity at 525 nm is found to increase with increase in ion fluence up to 1×10¹² ions cm⁻² and decreases beyond this fluence. Thermoluminescence (TL) of heat-treated and swift heavy ion (SHI) irradiated aluminum oxide gives a strong and broad TL glow with peak at ∼610 K along with a weak shoulder at 500 K. The TL intensity is found to increase with Au⁹⁺ ion fluence up to 1×10¹³ ions cm⁻² and decreases beyond this fluence.     

Characterization of laser waveguides in Nd:CNGG crystals formed by low fluence carbon ion implantation

We report on Nd:CNGG active planar waveguides produced by 6.0 MeV carbon ion implantation at fluence from 1 × 10¹⁴ ions/cm² to 8 × 10¹⁴ ions/cm². The refractive index profiles, which were reconstructed according to the measured dark mode spectroscopy, showed that the refractive indices had negative changes in the surface region, forming typical barrier waveguide. The width of waveguide structure induced by carbon ion implantation is ∼3.8 μm. The typical barrier-shaped distribution may be mainly due to the nuclear energy deposition of the incident ions into the substrate. By performing a modal analysis on the observed TE modes, it was found that the TE₀ and TE₁ modes can be well-confined inside the waveguide.     

Well-confined Yb:GdVO4 laser waveguide formed by MeV C ion implantation

The planar waveguide in x-cut Yb:GdVO₄ crystal has been fabricated by 6.0 MeV carbon ion implantation with the fluence of 1 × 10¹⁴ ions/cm² at room temperature. The modes of the waveguide were measured by the prism-coupling method with the wavelength of 633 nm and 1539 nm, respectively. An enhanced ordinary refractive index region was formed with a width of about 4.0 μm beneath the sample surface to act as a waveguide structure. By performing a modal analysis on the observed transverse magnetic polarized modes, it was found that all the transverse magnetic polarized modes can be well-confined inside the waveguide. Strong Yb-related photoluminescence in Yb:GdVO₄ waveguide has been observed at room temperature, which reveals that it exhibits possible applications for integrated active photonic devices.     

Analyses of surface coloration on TiO2 film irradiated with excimer laser

TiO₂ film of around 850 nm in thickness was deposited on a soda-lime glass by PVD sputtering and irradiated using one pulse of krypton-fluorine (KrF) excimer laser (wavelength of 248 nm and pulse duration of 25 ns) with varying fluence. The color of the irradiated area became darker with increasing laser fluence. Irradiated surfaces were characterized using optical microscopy, scanning electron microscopy, Raman spectroscopy and atomic force microscopy. Surface undergoes thermal annealing at low laser fluence of 400 and 590 mJ/cm². Microcracks at medium laser fluence of 1000 mJ/cm² are attributed to surface melting and solidification. Hydrodynamic ablation is proposed to explain the formation of micropores and networks at higher laser fluence of 1100 and 1200 mJ/cm². The darkening effect is explained in terms of trapping of light in the surface defects formed rather than anatase to rutile phase transformation as reported by others. Controlled darkening of TiO₂ film might be used for adjustable filters.     

Manipulating Ge quantum dots on ultrathin SixGe1−x oxide films using scanning tunneling microscope tips

Germanium quantum dots (QDs) were extracted from ultrathin Si_xGe_1−x oxide films using scanning tunneling microscope (STM) tips. The extraction was most efficiently performed at a positive sample bias voltage of +5.0 V. The tunneling current dependence of the extraction efficiency was explained by the electric field evaporation transfer mechanism for positive Ge ions from QDs to STM tips. Ge QDs (∼7 nm) were formed and isolated spatially by extracting the surrounding Ge QDs with an ultrahigh density of >10¹² cm⁻². Scanning tunneling spectroscopy of the spatially-isolated QDs revealed that QDs with an ultrahigh density are electrically-isolated from the adjacent dots.     

Investigation of FIB irradiation damage in La0.7Sr0.3MnO3 thin films

In this work we analyse systematically how morphological and magnetotransport properties of manganite thin films are affected by the damage induced by focused ion beam (FIB) irradiation. We irradiate different areas of the same sample with doses ranging from 5×10¹² to 3×10¹⁷ ions/cm² and we find that the film becomes swollen for doses up to 10¹⁶ ions/cm² and is eventually eroded by ion milling for further irradiation. On the other hand, transport properties are much more sensitive to FIB irradiation: the metal–insulator transition temperature is found to decrease monotonically with increasing doses up to 1.8×10¹³ ions/cm². At doses higher than 5.6×10¹³ ions/cm² the metallic state is completely suppressed and likely, also ferromagnetism.     

Change of sheet resistance of high purity alumina ceramics implanted by Cu and Ti ions

High purity alumina ceramics (99% Al₂O₃) was implanted by copper ion and titanium ion in a metal vapour vacuum arc (MEVVA) implanter, respectively. The influence of implantation parameters was studied varying ion fluence. The samples were implanted by 68 keV Cu ion and 82 keV Ti ion with fluences from 1 × 10¹⁵ to 1 × 10¹⁸ ions/cm², respectively. The as-implanted samples were investigated by scanning electron microscopy (SEM), glancing X-ray diffraction (GXRD), scanning Auger microscopy (SAM), and four-probe method. Different morphologies were observed on the surfaces of the as-implanted samples and clearly related to implantation parameters. For both ion implantations, the sheet resistances of the alumina samples implanted with Cu and Ti ion fluences of 1 × 10¹⁸ ions/cm², respectively, reached the corresponding minimum values because of the surface metallization. The experimental results indicate that the high-fluence ion implantation resulted in conductive layer on the surface of the as-implanted high purity alumina ceramics.     

Characteristics of sandwich-structured Al2O3/HfO2/Al2O3 gate dielectric films on ultra-thin silicon-on-insulator substrates

Sandwich-structure Al₂O₃/HfO₂/Al₂O₃ gate dielectric films were grown on ultra-thin silicon-on-insulator (SOI) substrates by vacuum electron beam evaporation (EB-PVD) method. AFM and TEM observations showed that the films remained amorphous even after post-annealing treatment at 950 °C with smooth surface and clean silicon interface. EDX- and XPS-analysis results revealed no silicate or silicide at the silicon interface. The equivalent oxide thickness was 3 nm and the dielectric constant was around 7.2, as determined by electrical measurements. A fixed charge density of 3 × 10¹⁰ cm⁻² and a leakage current of 5 × 10⁻⁷A/cm² at 2 V gate bias were achieved for Au/gate stack /Si/SiO₂/Si/Au MIS capacitors. Post-annealing treatment was found to effectively reduce trap density, but increase in annealing temperature did not made any significant difference in the electrical performance.     

Synthesis and surface modified hard magnetic properties in Co0.5Pt0.5 nanocrystallites from a rheological liquid precursor

Small crystallites of a metastable phase Co_0.5Pt_0.5 are precipitated by heating a rheological liquid precursor of cobalt–hydrazine complex and platinum chloride H₂PtCl₆·xH₂O in polymer molecules of poly(vinylpyrrolidone) (PVP) in ethylene glycol. The hydrazine co-reduces nascent atoms from the Co²⁺ and Pt⁴⁺ that recombine and grow as Co_0.5Pt_0.5. The PVP molecules cap a growing Co_0.5Pt_0.5 as it achieves a critical size so that it stops growing further in given conditions. X-ray diffraction pattern of a recovered powder reveals a crystalline Co_0.5Pt_0.5 phase (average crystallite size D∼8 nm) of a well-known Fm3m-fcc crystal structure with the lattice parameter a=0.3916 nm (density ρ=14.09 g/cm³). A more ordered L1₀ phase (ρ=15.91 g/cm³) transforms (D≥25 nm) upon annealing the powder at temperature lesser than 700 °C (in vacuum). At room temperature, the virgin crystallites bear only a small saturation magnetization M_s=5.54 emu/g (D=8 nm) of a soft magnet and it hardly grows on bigger sizes (D≤31 nm) in a canted ferromagnetic structure. A rectangular hysteresis loop is markedly expanded on an optimally annealed L1₀ phase at 800 °C for 60 min, showing a surface modified coercivity H_c=7.781 kOe with remnant ratio M_r/M_s=0.5564, and M_s=39.75 emu/g. Crystallites self-assembled in an acicular shape tailor large H_c from ideal single domains and high magnetocrystalline anisotropy of a hard magnet L1₀ phase.     

Synthesis and photoluminescence properties of aqueous CdWO4 quantum dots with WO6 luminescence center

Aqueous CdWO₄ QDs were synthesized by the reaction of CdCl₂ and Na₂WO₄ in the presence of mercaptoacetic acid (TGA) as capping reagent. The crystal morphology, particle size and its distribution of as-prepared products were characterized by transmission electron microscopy (TEM, SAED) atomic force microscopy (AFM), high-resolution transmission electron microscopy (HRTEM), and photon correlation spectroscopy (PCS), respectively. Qualitative assays for functional groups on the QDs’ surface were measured by fourier transform infrared spectroscopy (FTIR). Photoluminescence properties of QDs were studied by photoluminescence spectroscopy (PL). The results showed that the single QD with diameter of about 8 ± 2 nm was single-crystal. The particle size distribution of QDs was normal. Infrared absorption bands of carboxylic group on the surface of CdWO₄ QDs were observed around 1610-1550 cm⁻¹ (nonsymmetrical vibration of -COO⁻) and 1400 cm⁻¹ (symmetric vibration of C-O). With reaction-time going, PL peak position shifted from 498 to 549 nm and intensity of PL increased first and then decreased. PL peak position of QDs was blue-shift compared with 570 nm WO₆⁶⁻ luminescence center of bulk CdWO₄.