Low energy O2 and N2O ion beam modification of polyimide for improving adhesive strength of Cu/PI in roll-to-roll process

To enhance the weak mechanical durability of directly deposited copper layers on polyimide (PI) film due to their poor adhesive strength, a continuous roll-to-roll process involving surface modification using a reactive ion beam irradiation and in-situ deposition process is studied. The polyimide film is modified by an ion source with a linear stationary plasma thruster (LSPT) in the vacuum roll-to-roll process. An O₂ ion beam, with beam energy of 214 eV and beam current density of 0.78 mA/cm², and N₂O ion beam, with 220 eV and 0.69 mA/cm², irradiate PI film in winding speed of 0.5 m/min. The surface energy increases from 38 mN/m for the pristine PI film to 80 mN/m after beam irradiation at an ion fluence of 3.5 × 10¹⁶ ions/s. After beam irradiation, a 10 nm thick tie layer and 200 nm thick copper layer are successively deposited by in-situ DC magnetron web coating. The peel strength of the copper layer on the PI film is enhanced from 0.4 kgf/cm without ion beam treatment to 0.71 kgf/cm after O₂ beam treatment and to 0.75 kgf/cm after N₂O beam treatment. This enhancement is closely related to the increase in the polar force originating from the formation of hydrophilic CO (carbonyl) groups on the modified PI surface.     

Effect of intense laser and energetic ion irradiation on Raman modes of Multiwalled Carbon Nanotubes

The effects of intense laser and energetic ion irradiation on Raman vibrational modes of Multiwalled Carbon Nanotubes have been investigated. The intensity ratio of D and G modes decreases with increase in laser power density and remains almost constant with decrease of laser power density. The intensity ratio of D mode to G mode for ion irradiated Multiwalled Carbon Nanotubes decreases at low fluence (4 × 10¹¹ ions/cm²) and increases further with increase in ion fluence. The results show that ion irradiation at low fluence and laser irradiation lead to purification/ordering of the nanotubes.     

Ag and O ion irradiation induced improvement in dielectric properties of the Ba(Co1/3Nb2/3)O3 thin films

We present the preliminary results of temperature and frequency dependent dielectric measurements on Ba(Co_1/3Nb_2/3)O₃ (BCN) thin films. These films were prepared on indium tin oxide (ITO) coated glass substrates by the pulse laser deposition (PLD) technique. It exhibits single-phase hexagonal symmetry. These films were irradiated with Ag¹⁵⁺ (200 MeV) and O⁷⁺ (100 MeV) beams at the fluence 1 × 10¹¹, 1 × 10¹², and 1 × 10¹³ ions/cm². On irradiating these films, its dielectric constant (?′) and dielectric loss (tan δ) parameters improve compared to un-irradiated film. Compared to O⁷⁺ irradiation induced point/cluster defects Ag¹⁵⁺ induced columnar defects are more effective in reducing/pinning trapped charges within grains. The present paper highlights the role of swift heavy ion irradiation in engineering the dielectric properties of conductive samples to enable them to be useful for microwave device applications.     

Effect of ion bombardment on the optical properties of LDPE/EPDM polymer blends

Ion bombardment is a suitable tool to improve the physical properties of polymers. In the present study, the effect of ion bombardment on the optical properties of low density polyethylene (LDPE)/Ethylene propylene diene monomer (EPDM) blend (LDPE/EPDM) was studied. Polymer samples was bombarded with 130 keV He and 320 keV Ar ions at fluencies levels ranging from 1 × 10¹³ to 2 × 10¹⁶ ions/cm². The untreated and ion beam bombarded samples were investigated using ultraviolet-visible (UV-Vis) spectrophotometry. The optical band gap (E_g), was decreased from ∼2.9 eV for the pristine sample down to 1.7 eV for the samples bombarded with He and Ar ions at the highest fluences. Change in the optical gap indicates the presence of a gradual phase transition for the polymer blends. Activation energy has been investigated as a function of the ion fluences. With increasing ion fluence, a decrease in both the energy gap and the activation energy was observed. The number of carbon atoms (N) in a formed cluster is determined according to the modified Tauc's equation.     

Diffusion of Pb in carbon ion-implanted silicon: Discovery of a new crystalline phase after electron beam annealing

A novel phase has been discovered by dual low-energy ion implantation and high vacuum electron beam annealing. (100) p-type Si was implanted with (a) 20 keV ¹²C⁺ ions to the fluence of 6 × 10¹⁶ cm⁻² and (b) 7 keV Pb⁺ ions to the fluence of 4 × 10¹⁵ cm⁻². The ¹²C ion implantation results in an understoichiometric shallow SiC_x layer that intersects with the surface. The implanted Pb ions decorate a shallow subsurface region. High vacuum electron beam annealing at 1000 °C for 15 s using a temperature gradient of 5 °C s⁻¹ leads to the formation of large SiC nanocrystals on the surface with RBS measurements showing Pb has diffused into the deeper region affected by the ¹²C implantation. In this region, a new crystalline phase has been discovered by XRD measurements.     

Surface analysis of argon-implanted zircalloy-2 and influence of bubble formation on the corrosion behavior

In order to simulate the irradiation damage, argon ions were implanted into zircalloy-2 alloy with a fluence ranging from 1×10¹⁶ to 1×10¹⁷ ions/cm², using an implanter at an extraction voltage of 190 kV, at liquid nitrogen temperature. Then the effect of argon ion implantation on the aqueous corrosion behavior of zircalloy-2 alloy was studied. The valence states of elements in the surface layer of the samples were analyzed by X-ray photoelectron spectroscopy (XPS). Transmission electron microscopy (TEM) was used to examine the microstructure of the argon-implanted samples. Glancing angle X-ray diffraction (GAXRD) was employed to examine the phase transformation due to the argon ion implantation. The potentiodynamic polarization technique was employed to evaluate the aqueous corrosion resistance of implanted zircalloy-2 alloy in a 1 M H₂SO₄ solution. It was found that the bubbles were formed on the surface of implanted samples; the bubbles grew larger with increasing argon fluence. The microstructure of argon-implanted samples changed from amorphous to partial amorphous, then to polycrystalline and finally to amorphous. The bubble forming and changing and microstructure changes affected the corrosion properties of implanted samples. Finally, the mechanism of the corrosion behavior of argon-implanted zircalloy-2 alloy is discussed.     

Study of SHI induced recrystallization effects in SOI structures synthesized by nitrogen and oxygen ion implantation in silicon

Silicon oxynitride (Si_xO_yN_z) buried insulating layers were synthesized by implantation of nitrogen (¹⁴N⁺) and oxygen (¹⁶O⁺) ions sequentially in the ratio 1:1 at 150 keV to ion-fluences ranging from 1 × 10¹⁷ to 5 × 10¹⁷ cm⁻² to prepare silicon on insulator (SOI) structures. The as implanted samples were held at 270 °C and irradiated to total fluence of 1 × 10¹⁴ cm⁻² by 60 MeV Ni⁺⁵ to study the structural changes/recrystallization of SOI structures induced by swift heavy ion (SHI) irradiation. Fourier transform infrared (FTIR) measurements on the as implanted samples (≤1 × 10¹⁸ cm⁻²) show a single absorption band in the wavenumber range 1300-750 cm⁻¹ attributed to the formation of silicon oxynitride (Si-O-N) bonds in the implanted silicon. It is observed that a nitrogen rich silicon oxynitride structure is formed after SHI irradiation. The study of X-ray rocking curves on the samples show the formation of small silicon crystallites due to swift heavy ion irradiation.     

Ion sputtering rates of C, CrxCy, and Cr at different Ar ion incidence angles

To study the ion sputtering of a layered structure with different layer densities and ion sputtering yields a trilayer structure of C-graphite(46 nm)/Cr_xC_y(60 nm)/Cr(69 nm) was sputter deposited onto smooth silicon substrates. The ion sputtering rates of amorphous carbon, amorphous Cr_xC_y and polycrystalline Cr were determined by means of Auger electron spectroscopy depth profiling as a function of the angle of incidence of two symmetrically inclined 1 keV Ar⁺ ion beams in the range between 22° and 82°. The sputtering rates were calculated from the known thicknesses of the layers and the sputtering times necessary to remove the individual layers. It was found that the sputtering rates of C-graphite, Cr_xC_y carbide and Cr were strongly angle dependent. The experimental sputtering yields were in agreement with the theoretical results obtained by calculation of the transport of ions in solids, but the sputtering yields of C-graphite measured at ion incidence angles larger than 29° were smaller than the simulated ones.     

Ion irradiation induced amorphization of SnO2 nanoparticles embedded in SiO2

SnO₂ nanoparticles (NPs) of average diameter of ∼10.5 nm, synthesized in SiO₂ using Sn⁻ ions implantation combined with thermal annealing, were irradiated with 1.5 MeV Au²⁺ ions at room temperature. The NP structure was studied as a function of ion fluence by transmission electron microscopy and micro-Raman spectroscopy. Prior to ion irradiation, SnO₂ NPs have been found to exhibit the rutile crystal structure. Upon irradiation, amorphization in the nanocrystals has been seen to increase with increase in ion fluence. In particular, at a fluence of 1 × 10¹⁴ ions cm⁻² we argue for the presence of an amorphous SnO₂ phase. Beyond this fluence, the NPs have been found to dissolve in the matrix. The observed results are explained in the frame work of ion irradiation induced defects production in the NPs as well as in the NP/matrix interface.     

Ion beam modification of TiO2 films prepared by Cat-CVD for solar cell

The effects of nitrogen ion bombardment on TiO₂ films prepared by the Cat-CVD method have been studied to improve the optical and electrical properties of the material for use in Si thin film solar cells. The refractive index n and the dark conductivity of the TiO₂ film increased with irradiation time. The refractive index n of the TiO₂ film was changed from 2.1 to 2.4 and the electrical conductivity was improved from 3.4 × 10^− 2 to 1.2 × 10^− 1 S/cm by the irradiation. These results are due to the formation of Ti-N bonds and oxygen vacancies in the film.     

Effects of oxygen addition on electrochromic properties in low temperature plasma-enhanced chemical vapor deposition-synthesized MoOxCy thin films for flexible electrochromic devices

Electrochromic organomolybdenum oxide (MoO_xC_y) films are deposited onto 60 Ω/□ flexible polyethylene terephthalate/indium tin oxide substrates by low temperature plasma-enhanced chemical vapor deposition (PECVD) using a precursor of molybdenum carbonyl vapor, which is carried by argon gas, mixed with oxygen gas and synthesized by radio frequency power at room temperature (23 °C). The MoO_xC_y films with modified surface morphology and compositions of varying oxygen contents are proven to offer noteworthy electrochromic performance. Porous surface of the MoO_xC_y film (398 nm thick) provides Li⁺ ion diffusion coefficient value of 1.7 × 10^− 10 cm²/s for Li⁺ de-intercalation at a potential scan rate of 2 mV/s. High x/y value at high surface composition of oxygen to carbon in the MoO_xC_y film offers light modulation with transmittance variation of up to 63% and coloration efficiency of 36 cm²/C at a wavelength of 800 nm for 200 cycles of Li⁺ intercalation and de-intercalation. PECVD-synthesized MoO_xC_y thin films show promising electrochromic properties for applications in flexible electrochromic devices.     

Polypyrrole thin films for gas sensors prepared by Matrix-Assisted Pulsed Laser Evaporation technology: Effect of deposition parameters on material properties

Thin films of polypyrrole (PPY) were prepared by Matrix-Assisted Pulsed Laser Evaporation (MAPLE) technology from two matrices: water and dimethylsulfoxide (DMSO). The deposition was carried out using a KrF excimer laser (laser fluence F ranged from 0.1 to 0.6 J cm^− 2). This work deals with optimization of two deposition parameters - laser fluence and number of pulses - for both matrices. From the deposition curves, the fluence thresholds, F_th, and maximum growth rates were subsequently determined (water matrix: F_th ~ 0.40-0.45 J cm^− 2, maximum growth rate 0.16 nm pulse^− 1; DMSO matrix: F_th ~ 0.25-0.30 J cm^− 2; maximum growth rate 0.20 nm pulse^− 1). The changes in chemical composition of deposited layers were studied by Attenuated Total Reflection Fourier Transform Infrared spectroscopy. Surface morphology was characterized by Atomic Force Microscopy. A discussion is also presented concerning relationships between laser fluence and chemical composition of deposited layers with respect to their potential application in gas sensors. Finally, the response of a sensor with a MAPLE deposited PPY active layer to air humidity is presented.     

Irradiation-induced gold silicide formation and stoichiometry effects in ion beam-mixed layer

The irradiation-induced silicide formation in ion beam-mixed layer of Au/Si(1 0 0) system was investigated by using 200 keV Kr⁺ and 350 keV Xe⁺ ions to fluences ranging from 8×10¹⁴ to 1×10¹⁶ ions/cm² at room temperature. The thickness of Au layer evaporated on Si substrate was ∼500 Å. Rutherford backscattering spectrometry (RBS) experiments were carried out to study the irradiation effects on the mixed layers. We observed that at the fluence of 1×10¹⁶ Kr⁺/cm² and starting from the fluence of 8×10¹⁴ Xe⁺/cm², a total mixing of the deposited Au layer with Si was obtained. RBS data corresponding to the fluences of 1×10¹⁶ Kr⁺/cm² and 8×10¹⁴ Xe⁺/cm² clearly showed mixed layers with homogenous concentrations of Au and Si atoms which can be attributed to gold silicides.The samples irradiated to fluences of 1×10¹⁶ Kr⁺/cm² and 1×10¹⁶ Xe⁺/cm² were also analyzed by X-ray photoelectron spectroscopy (XPS). The observed chemical shift of Au 4f and Si 2p lines confirmed the formation of gold silicides at the surface of the mixed layers. Au₂Si phase is obtained with Kr⁺ irradiation whereas the formed phase with Xe⁺ ions is more enriched in Si atoms.     

Synthesis and crystal structure of triphosphate RbPrHP3O10

Crystals of RbPrHP₃O₁₀ have been grown by the flux technique and characterized by single-crystal X-ray diffraction. RbPrHP₃O₁₀ crystallizes in the triclinic space group with lattice parameters: a = 7.0655(5), b = 7.7791(4), c = 8.6828(6) Å, α = 74.074(3), β = 74.270(3), γ = 82.865(2)°, V = 441.09(5) ų, Z = 2. The crystal structure has been solved yielding a final R(F²) = 0.0443 and R_w(F²) = 0.1426 for 1955 independent reflections (F_o² ≥ 2σ(F_o²)). The structure of RbPrHP₃O₁₀ consists of PrO₈ polyhedra and P₃O₁₀⁵⁻ groups sharing oxygen atoms to form a two-dimensional framework; the PrO₈ polyhedra form infinite chains by edge-sharing. Each Rb⁺ ion is bonded to 10 oxygen atoms, these ions are located between chains formed of (HP₃O₁₀)⁴⁻. The energies of the vibrational modes of the crystal were obtained from measurements of the infrared spectrum.     

Ni silicide formation on epitaxial Si1 − yCy/(001) layers

The formation of Ni silicides on Si_1 − yC_y (y = 0.01 and 0.018) epilayers grown on Si(001) has been investigated. The presence of C atoms was found to significantly retard the growth kinetics of NiSi and enhances the thermal stability of thin NiSi films. For Ni(11 nm)/Si_0.982C_0.018 samples, the process window of NiSi was shifted and extended to 450-700 °C. Moreover, there was an additional strain introduced into the Si_1 − yC_y epilayers during Ni silicidation. This work shows the potential of Ni silicidation on Si_1yC_y for device applications.     

Surface morphology analysis of natural single crystal diamond chips bombarded with Ar ion beam

We have studied the surface morphology of natural single crystal diamond chips machined by 0.5-3.0 keV Ar⁺ ion beam irradiation at ion incidence angles of 0°, 30°, 45°, 60°, and 80° with ion doses from 3.4 × 10¹⁸ ions/cm² to 6.8 × 10¹⁸ ions/cm². The surface of diamond chips machined with 0.5 and 1.0 keV Ar⁺ ion beam, at angles of ion incidence from 0° to 45° can be made smooth. Results show that the machined surface at ion dose of 6.8 × 10¹⁸ ions/cm² and beam energy of 0.5 and 1.0 keV become ultra-smooth (surface roughness SR = 0.1 nm rms) compared with unprocessed surface (SR = 0.15-2.1 nm rms). Results also confirm the ripple formation on diamond surface at ion incidence angles of 60°-80° by 0.5-3.0 keV Ar⁺ ion beam. Therefore, the technique of smoothing by choosing ion beam irradiation parameter can be applicable to nano-finishing of diamond tools without ripple formation. This technique can also be applicable in mass production if the diamond surface is mechanically pre-finished.     

100 keV nitrogen ion beam implanted polycarbonate: A possibility for UV blocking devices

Polycarbonate samples were implanted with 100 keV N⁺ ions at fluences 10¹⁵, 10¹⁶ and 5 × 10¹⁶ ions cm⁻². Drastic alterations in UV-Visible transmittance spectra were observed which are interrelated with change in surface color and optical absorption of the implanted samples. UV-Visible transmission studies show that at ion fluence of 10¹⁶ ions cm⁻², transmission approaches to zero at about λ = 427 nm and below up to 200 nm. Optical band gap (E_OPT) reduces with increase in fluence and at maximum ion fluence of 5 × 10¹⁶ N⁺ cm⁻², E_OPT was determined to be 1.56 eV whereas for pristine its value was 3.00 eV. Raman analysis indicates the formation of amorphous carbon on the surface of polycarbonate at an ion fluence of 10¹⁶ N⁺ cm⁻². Rise in fluence to 5 × 10¹⁶ N⁺ cm⁻² results in enhancement in disorder on the surface of the host polymer. Modifications in the structural arrangements were found to be in strong association with changes in optical properties with increase in ion fluence and the same is discussed.     

Eu-Mössbauer spectroscopic and X-ray diffraction study on EuyM1−yO2−x (0 ≤ y ≤ 1.0) (M = Th, U)

¹⁵¹Eu-Mössbauer spectroscopic and powder X-ray diffraction (XRD) study has been performed for the Eu_yM_1−yO_2−x (M = Th and U) systems over the entire composition range of 0 ≤ y ≤ 1.0. The XRD results of the Eu-Th system showed that a very wide defect-fluorite (DF) type phase in which oxygen vacancies (V_O) are disordered (x = y/2) is formed for 0 ≤ y < 0.5 and that two-phase regions sandwitching a narrow C-type (C) single phase around y ≈ 0.8 appear for 0.5 < y < 0.8 (DF + C) and 0.82 < y < 1.0 (C + B-type (monoclinic) Eu₂O₃). The Mössbauer results show that the isomer shifts (ISs) of Eu³⁺ in this system smoothly increase with Eu composition, y. The decrease of average coordination number (CN) of O²⁻ around Eu³⁺ with increasing y (CN = 8 − 2y) (x = y/2) results in the decrease of the average EuO bond length, which is due to the decrease of repulsion force between O²⁻ anions. This result confirms that the IS of Eu³⁺ correlates well with the average EuO bond length in oxide systems. For the Eu-U system, the lattice parameter, a₀, of the system decreases almost linearly with y, in accordance with the calculated a₀ versus y curve for the oxygen-stoichiometric (i.e. x = 0) fluorite-type dioxide (CN = 8). The ISs of Eu³⁺ in this composition range remain almost constant around 0.5 mm/s, which is comparable to those of pyrochlore oxides (Eu₂Zr₂O₇ and Eu₂Hf₂O₇ (y = 0.5)) with O²⁻-eight-fold coordinated Eu³⁺(CN = 8).     

Electrical and morphological properties of poly(3-hexyl thiophene) irradiated with 100 MeV silver ions

Poly(3-hexyl thiophene) has been prepared by a chemical oxidation process. The pristine polymer was irradiated with various fluences of (silver (Ag⁸⁺)) swift heavy ions viz. 10¹⁰, 10¹¹, and 10¹² ions/cm². All the samples, irradiated and without irradiation, have been characterized by various techniques such as surface electron microscopy (SEM), atomic force microscopy (AFM), X-ray diffraction (XRD), FT-IR and UV spectroscopy. The dc conductivity of all the samples has been investigated in 77-300 K. The room temperature conductivity of pristine samples is 2.39 × 10⁻⁸ which increases to 1.65 × 10⁻⁶ Ohm⁻¹ cm⁻¹ at the fluence of 10¹¹ ions/cm². The observed conduction mechanism for all the samples could be explained in terms of Mott's variable range hopping model.