Investigation of the interface trap density and series resistance of a high-k HfO2-based MOS capacitor: before and after 50 MeV Li3+ ion irradiation

This is the first investigation on the effects of 50 MeV Li³⁺ ions on interface trap density (D _it) and series resistance (R _s), which reveal the improvement of the dielectric properties of RF-sputtered HfO₂-metal oxide semiconductor (MOS) capacitors. The samples were irradiated and characterized at room temperature. The D _it and R _s were determined from the capacitance–voltage (C–V) and conduction–voltage (G–V) characteristics at 1 MHz. The measured capacitance and conductance were corrected for series resistance. It is found that the series resistance of Al/HfO₂/p? Si MOS capacitors increases with ion fluence, calculated at a strong accumulation region before and after irradiation. The interface state density of MOS devices before and after irradiation is found to decrease with increasing ion fluence.     

Structural,optical and electrical properties of 60 MeV C5+ ion-irradiated poly(3-methylthiophene) films

The structural, optical and electrical properties of 60 MeV C⁵⁺ ion-irradiated poly(3-methylthiophene) (P3MT) synthesized by the chemical oxidation polymerization method have been studied. The P3MT powder was dissolved in chloroform (CHCl₃), and thin films of thickness 2 μm were prepared on glass and Si substrates. The polymerization was confirmed by the FTIR spectrum. Then films were irradiated by 60 MeV C⁵⁺ ions at different fluences. FTIR spectra show methyl group evolution after irradiation. The optical band gap decreases slightly after irradiation and the DC conductivity increases by about one order of magnitude after irradiation at the highest fluence. The role of S _e has also been discussed when compared with 60 MeV Si⁵⁺ ion irradiation of P3MT. The morphological changes are observed using SEM.     

Temperature and frequency dependent electrical properties of 50 MeV Li3+ ion irradiated polymeric blends

The polymeric blends of polyvinyl chloride (PVC) and polyethylene terephthalate (PET) with equal composition by weight have been irradiated with 50 MeV Li³⁺ ions at different fluences. The AC electrical properties of polymeric blends were measured in the frequency range 0.05–100 kHz, and at temperature range 40–150 ^°C using LCR meter. There is an exponential increase in conductivity with log of frequency and effect is significant at higher fluences. The value of tan δ and dielectric constant are observed to change appreciably due to irradiation. The loss factor (tan δ) versus frequency plot suggests that the capacitors of polymeric blend of PVC and PET may be useful below 10 kHz. No change in dielectric constant was observed over a wide temperature range up to 150 ^°C. Thermal stability was studied by thermogravimetric analysis. Thermal analysis revealed that chain scission is the dominant phenomena in the polymeric blends resulting in the reduction of its thermal stability. It appears from differential scanning calorimetry studies that the melting temperature decreases as fluence increases. FTIR spectra measurements also revealed that the material suffered severe degradation through bond breaking beyond the fluence of 2.3×10¹³ ions/cm².     

Controlled synthesis and analysis of He–H+3 in a 3.7 K ion trap

Complexes of the triatomic hydrogen ion with helium were synthesised in a low-temperature 22-pole rf ion trap at He number densities of up to 10¹⁶ cm^?3. Absolute ternary rate coefficients for sequentially attaching He atoms have been determined from the growth of complexes with increasing storage time. The number of helium-tagged ions is significantly reduced when increasing the nominal temperature from 4 to 25 K. Competition between attachment and dissociation via collisions leads to stationary He_n–H⁺₃ (n up to 9) distributions. State-specific excitation of the trapped H⁺₃ ions via IR transitions significantly reduces the formation of complexes. Tuning the laser to Δv₂ = 1 transitions in the range of 2726 cm^?1 leads to LIICG lines, i.e., to spectra caused by laser-induced inhibition of complex growth. In addition, almost 100 lines have been found between 2700 and 2765 cm^?1, which are attributed to laser-induced dissociation of the in situ formed He–H⁺₃ complex ions. These lines are not yet assigned; however, their absorption strength, statistics and predissociation lifetimes provide interesting information on both the stable complexes as well as on scattering resonances in low-energy H⁺₃+He collisions. New calculations of the potential energy surface will help to analyse the dissociation spectrum. There are some indications that para-H⁺₃ is enriched under the conditions of the present experiment.     

Effect of 100 MeV swift Si8+ ions on structural and thermoluminescence properties of Y2O3:Dy3+nanophosphor

Nanoparticles of Y₂O₃:Dy³⁺ were prepared by the solution combustion method. The X-ray diffraction pattern of the 900°C annealed sample shows a cubic structure and the average crystallite size was found to be 31.49?nm. The field emission scanning electron microscopy image of the 900°C annealed sample shows well-separated spherical shape particles and the average particle size is found to be in a range 40?nm. Pellets of Y₂O₃:Dy³⁺ were irradiated with 100?MeV swift Si⁸⁺ ions for the fluence range of 3?×?10^11_3?×?10¹³ ions cm^?2. Pristine Y₂O₃:Dy³⁺ shows seven Raman modes with peaks at 129, 160, 330, 376, 434, 467 and 590?cm^?1. The intensity of these modes decreases with an increase in ion fluence. A well-resolved thermoluminescence glow with peaks at ～414?K (T_m1) and ～614?K (T_m2) were observed in Si⁸⁺ ion-irradiated samples. It is found that glow peak intensity at 414?K increases with an increase in the dopant concentration up to 0.6?mol% and then decreases with an increase in dopant concentration. The high-temperature glow peak (614?K) intensity linearly increases with an increase in ion fluence. The broad TL glow curves were deconvoluted using the glow curve deconvoluted method and kinetic parameters were calculated using the general order kinetic equation.     

Enhancement in electrochemical properties of ionic liquid-based nanocomposite polymer electrolytes by 100 MeV Si9+ swift heavy ion irradiation

Swift heavy ion (SHI) irradiation has been used as a tool to enhance the electrochemical properties of ionic liquid-based nanocomposite polymer electrolytes dispersed with dedoped polyaniline (PAni) nanorods; 100 MeV Si⁹⁺ ions with four different fluences of 5?×?10¹⁰, 1?×?10¹¹, 5?×?10¹¹, and 1?×?10¹² ions cm^?2 have been used as SHI. XRD results depict that with increasing ion fluence, crystallinity decreases due to chain scission up to fluence of 5?×?10¹¹ ions cm^?2, and at higher fluence, crystallinity increases due to cross-linking of polymer chains. Ionic conductivity, electrochemical stability, and dielectric properties are enhanced with increasing ion fluence attaining maximum value at the fluence of 5?×?10¹¹ ions cm^?2 and subsequently decrease. Optimum ionic conductivity of 1.5?×?10^?2 S cm^?1 and electrochemical stability up to 6.3 V have been obtained at the fluence of 5?×?10¹¹ ions cm^?2. Ac conductivity studies show that ion conduction takes place through hopping of ions from one coordination site to the other. On SHI irradiation, amorphicity of the polymer matrix increases resulting in increased segmental motion which facilitates ion hopping leading to an increase in ionic conductivity. Thermogravimetric analysis (TGA) measurements show that SHI-irradiated nanocomposite polymer electrolytes are thermally stable up to 240–260 °C.     

50 MeV Li3+ ion irradiation effect on structural, electrical, and dielectric properties of PVA-based nanocomposite polymer electrolytes

Nanocomposite polymer electrolyte thin films of polyvinyl alcohol (PVA)-orthophosphoric acid (H₃PO₄)-Al₂O₃ have been prepared by solution cast technique. Films are irradiated with 50 MeV Li³⁺ ions having four different fluences viz. 5?×?10¹⁰, 1?×?10¹¹, 5?×?10¹¹, and 1?×?10¹² ions/cm². The effect of irradiation on polymeric samples has been studied and characterized. X-ray diffraction spectra reveal that percent degree of crystallinity of samples decrease with ion fluences. Glass transition and melting temperatures have been also decreased as observed in differential scanning calorimetry. A possible complexation/interaction has been shown by Fourier transform infrared spectroscopy. Temperature-dependent ionic conductivity shows an Arrhenius behavior before and after glass transition temperature. It is observed that ionic conductivity increases with ion fluences and after a critical fluence, it starts to decrease. Maximum ionic conductivity of ～2.3?×?10^?5 S/cm owing to minimum activation energy of ～0.012 eV has been observed for irradiated electrolyte sample at fluence of 5?×?10¹¹ ions/cm². The dielectric constant and dielectric loss also increase with ion fluences while they decrease with frequency. Transference number of ions shows that the samples are of purely ionic in nature before and after ion irradiation.     

Effect of 50 MeV Li+3 and 80 MeV C+5 ions’ beam irradiation on the optical,structural, chemical and surface topographic properties of PMMA films*

The self-standing films of polymethyl methacrylate (PMMA) were irradiated under vacuum with 50?MeV lithium (Li³⁺) and 80?MeV carbon (C⁵⁺) ions to the fluences of 3?×?10¹⁴, 1?×?10¹⁵, 1?×?10¹⁶ and 1?×?10¹⁷ ions µm^?2. The pristine and irradiated samples of PMMA films were studied by using ultraviolet–visible (UV–Vis) spectrophotometry, Fourier transform infrared, X-ray diffractrometer and atomic force microscopy. With increasing ion fluence of swift heavy ion (SHI), PMMA suffers degradation, UV–Vis spectra show a shift in the absorption band from the UV towards visible, attributing the formation of the modified system of bonds. E_g and E_a decrease with increasing ion fluence. The size of crystallite and crystallinity percentage decreases with increasing ion fluence. With SHI irradiation, the intensity of IR bands and characteristic bands of different functional groups are found to shift drastically. The change in (E_g) and (N) in carbon cluster is calculated. Shifting of the absorption band from the UV towards visible along with optical activity and as a result of irradiation, some defects are created in the polymer causing the formation of conjugated bonds and carbon clusters in the polymer, which in turn lead to the modification in optical properties that could be useful in the fabrication of optoelectronic devices, gas sensing, electromagnetic shielding and drug delivery.     

Degradation behaviors and failure analysis of Ni–BaTiO3 base-metal electrode multilayer ceramic capacitors under highly accelerated life test

The degradation in insulation resistance under highly accelerated test conditions was investigated in terms of micro-structural and micro-chemical changes in dielectric layer of multilayer ceramic capacitor. The ceramic capacitors were prepared by using BaTiO₃ powder with different size of 0.52 μm, 0.55 μm, and 0.58 μm. As the particle size of BaTiO₃ powder was increased, the capacitance and the dissipation factor were decreased. According to the result of highly accelerated test conducted at 150 °C, 75 V, and 20 h, failure in insulation resistance was increased with the particle size and the calculated FITs (failure in term) were 1.10 at 0.52 μm, 2.11 at 0.55 μm, and 6.69 at 0.58 μm, respectively. The failure was examined by X-ray photoelectron spectroscopy and transmission electron microscopy, which was attributed to the oxidation of Ni inner electrode that could create oxygen vacancies and increase electric conduction of the ceramic capacitors.     

Investigations of the optical band positions,EPR parameters and defect structure for the trigonal Cr3+–Li+ centre in CsMgCl3 crystal

A unified calculation of optical band positions and electron paramagnetic resonance (EPR) (or spin-Hamiltonian) parameters for the trigonal Cr³⁺–Li⁺ centre in CsMgCl₃ crystal is made by using the complete diagonalisation (of energy matrix) method based on the two-spin–orbit-parameter model. In this model, the contributions from the spin–orbit parameter of central dⁿ ion and that of ligand ion are included. From the calculation, the 11 observed optical and EPR data (eight optical band positions and three EPR parameters g_//, g_⊥, D) are reasonably explained with five adjustable parameters and the defect structure of the Cr³⁺–Li⁺ centre (which is consistent with the expectation based on the electrostatic interaction) in CsMgCl₃ is acquired. The results are discussed.     

Manifestation of up-conversion in Yb3+/Tm3+ doped Li2O–Y2O3–SiO2 glass system

In this study, we have investigated the principal role of Y₂O₃ on the emission features of Tm³⁺ ion and up-conversion phenomenon in Tm³⁺ and Yb³⁺ co-doped Li₂O–Y₂O₃–SiO₂ glass system. The concentration of Y₂O₃ is varied from 0 to 5 mol% while that of Yb³⁺ and Tm³⁺ is fixed. When the glasses are doped with Tm³⁺ ions, the intense blue and red emissions were observed, whereas Yb³⁺ doped glasses exhibited NIR emission at about 980 nm. When the glasses are co-doped with Tm³⁺ and Yb³⁺ ions and excited at 900 nm, the blue and red emission lines were observed to be reinforced and strengthened with increase in the concentration of Y₂O₃. The IR emission band detected at about 1.8 μm due to ³F₄ → ³H₆ transition of Tm³⁺ ions is also observed to be strengthened due to co-doping. The reasons for enhancement in the intensity of various emission bands due to co-doping have been identified and discussed with the help of rate equations for various emission transitions.     

Structural analysis and band gap tailoring of Fe3+-doped Zn–TiO2 nanoparticles

We report on the analysis of morphology and electronic structure of Fe³⁺-doped Zn–TiO₂ nanoparticles. Crystalline nature, phase, and preferred growth direction of the nanoparticles were all determined. Due to size effects and OH⁻–(TiO₄) ⁿ complexes, variation in the energy gap with metallic and semiconducting characters on the same sample was found. The variation in the energy gap decreased, and the bang gap decayed exponentially with Fe doping and independent of the supporting substrates. Simultaneous effect of the OH⁻ ligands on the electronic structure and the formation mechanism of nanorods and nanosheets as manifested by the rutile TiO₆ octahedra units edge- and corner-shared bonding was discussed.     

Cross-sections of large-angle hadron production in proton–and pion–nucleus interactions V: lead nuclei and beam momenta from ±3 GeV/c to ±15 GeV/c

We report on double-differential inclusive cross-sections of the production of secondary protons, charged pions, and deuterons, in the interactions with a 5% λ _int thick stationary lead target, of proton and pion beams with momentum from ±3 GeV/c to ±15 GeV/c. Results are given for secondary particles with production angles 20°<θ<125°. Cross-sections on lead nuclei are compared with cross-sections on beryllium, copper, and tantalum nuclei.     

Temperature and metal composition dependence of lateral photovoltaic effect in Al-Alq3/SiO2/Si structures

By using PDM-OFDM-16QAM modulation, all-Raman amplification, coherent detection, and 7% forward error correction （FEC） threshold, we successfully demonstrate 63-Tb/s （368× 183.3-Gb/s） signal over 160- km standard single mode fiber （SSMF） transmission in the C- and L-bands with 25-GHz channel spacing. 368 optical channels with bandwidth spacing of 25 GHz are generated from 16 external cavity laser sources. After 160-km SSMF transmission, all tested bit error rate （BER） are under 3.8×10^-3, which can be recovered by 7% FEC threshold. Within each channel, we achieve the spectral efficiency of 6.85 bit/s/Hz in C/L band.     

Spectroscopic ellipsometric evidence of the solid-state reactions in Ni/Si multilayered films,induced by ion-beam mixing and thermal annealing

Solid-state reactions, induced by ion-beam mixing (IBM) and thermal annealing, in Ni/Si multilayered films (MLF) with an overall stoichiometry of Ni2Si, NiSi and NiSi2, while keeping the nominal thickness of Ni sublayer constant (3.0 nm), were studied by using spectroscopic ellipsometry as well as X-ray diffraction (XRD). The mixing was performed with Ar+ ions of an energy of 80 keV and a dose of 1.5× 1016 Ar+/cm2. Unlike the results of our previous study on Fe/Si MLF [Y.V. Kudryavtsev et al., Phys. Rev. B 65, 104417 (2002)], it was shown that an amorphous phase of NiSi in the B20 phase was formed during deposition independent of the overall stoichiometry of MLF, i.e., the nominal thickness of Si sublayer. IBM leads to some structural changes in the Ni/Si MLF, which cannot be detected by XRD but are confidently recognized by optical tools. A thermal annealing at 673 K of the Ni/Si MLF with an overall stoichiometry of NiSi and NiSi2 causes formation of the -NiSi phase. The first trace of NiSi2 phase on the background of the -NiSi phase was detected by XRD after an annealing at 1073 K, while, according to the optical results, NiSi2 turned out to be the dominant phase for the annealed Ni/Si MLF with an overall stoichiometry of NiSi2.     

Temperature-Dependent Current–Voltage (I–V) and Capacitance–Voltage (C–V) Characteristics of Ni/Cu/n-InP Schottky Barrier Diodes

The current-voltage (I–V) and capacitance-voltage (C–V) characteristics of Ni/Cu/n-InP Schottky barrier diodes are studied over a wide temperature range, from 210 K to 420 K. The I–V characteristics display anomalous thermal behavior. The apparent barrier height decays, and the ideality factor grows at low temperatures, and the series resistances resulting from Cheung’s and Norde’s procedures are markedly temperature dependent. The nonlinearity of the Richardson plot and the strong temperature dependence of the Schottky-barrier parameters indicate that the interface is spatially inhomogeneous. Plots of the zero-bias barrier height as a function of 1/(2kT) points to a Gaussian distribution of barrier heights with 0.90 eV mean height and 0.014 eV standard deviation. When this distribution is accounted for, a Richardson of 6.5 A/(cm K)² results, relatively close to the 9.4/(cm K)² predicted by theory. We conclude that, combined with a Gaussian distribution of barrier heights, the thermionic-emission mechanism explains the temperature-dependent I–V and C–V characteristics of the studied Schottky-barrier diodes.     

Development and characteristic analysis of a field-plated Al2O3/AlInN/GaN MOS–HEMT

We present an AlInN/AlN/GaN MOS–HEMT with a 3 nm ultra-thin atomic layer deposition (ALD) Al₂O₃ dielectric layer and a 0.3 μm field-plate (FP)-MOS--HEMT. Compared with a conventional AlInN/AlN/GaN HEMT (HEMT) with the same dimensions, a FP-MOS--HEMT with a 0.6 μm gate length exhibits an improved maximum drain current of 1141 mA/mm, an improved peak extrinsic transconductance of 325 mS/mm and effective suppression of gate leakage in both the reverse direction (by about one order of magnitude) and the forward direction (by more than two orders of magnitude). Moreover, the peak extrinsic transconductance of the FP-MOS--HEMT is slightly larger than that of the HEMT, indicating an exciting improvement of transconductance performance. The sharp transition from depletion to accumulation in the capacitance--voltage (C--V) curve of the FP-MOS--HEMT demonstrates a high-quality interface of Al₂O₃/AlInN. In addition, a large off-state breakdown voltage of 133 V, a high field-plate efficiency of 170 V/μ m and a negligible double-pulse current collapse is achieved in the FP-MOS--HEMT. This is attributed to the adoption of an ultra-thin Al₂O₃ gate dielectric and also of a field-plate on the dielectric of an appropriate thickness. The results show a great potential application of the ultra-thin ALD-Al₂O₃ FP-MOS--HEMT to deliver high currents and power densities in high power microwave technologies.     

Cross-sections of large-angle hadron production in proton– and pion–nucleus interactions II: beryllium nuclei and beam momenta from ±3 GeV/c to ±15 GeV/c

We report on double-differential inclusive cross-sections of the production of secondary protons and charged pions, in the interactions with a 5% λ _abs thick stationary beryllium target, of proton and pion beams with momentum from ±3 GeV/c to ±15 GeV/c. Results are given for secondary particles with production angles 20° <θ<125°.     

Theoretical investigation of electron paramagnetic resonance parameters and lattice distortion in α-Al2O3 crystal doped with V3+ ions

The electron paramagnetic resonance parameters D, g _∥ and g _⊥ for V³⁺ ions in α-Al₂O₃ crystals are calculated on the basis of the complete diagonalization method and the superposition model. In the calculation, the contributions of the variation of the cation–ligand bond lengths and bond angles are taken into consideration. The calculated results agree well with the experimental data. Our investigation shows that the local structure around the V³⁺ ions possesses a compressed trigonal distortion above the O^2?-triangle and an elongated trigonal distortion in the lower one.     

Cross-sections of large-angle hadron production in proton– and pion–nucleus interactions VI: carbon nuclei and beam momenta from ±3 GeV/c to ±15 GeV/c

We report on double-differential inclusive cross-sections of the production of secondary protons, charged pions, and deuterons, in the interactions with a 5% λ _int thick stationary carbon target, of proton and pion beams with momentum from ±3 GeV/c to ±15 GeV/c. Results are given for secondary particles with production angles 20°<θ<125°. Cross-sections on carbon nuclei are compared with cross-sections on beryllium, copper, tantalum and lead nuclei.