Probing charge carrier compensation in high energy ion irradiated III–V semiconductor by Raman spectroscopy and Hall measurements

Raman spectroscopy and Hall measurements have been carried out to investigate the differences in near‐surface charge carrier modulation in high energy (~100 MeV) silicon ion (Si⁸⁺) and oxygen ion (O⁷⁺) irradiated n‐GaAs. In the case of O ion irradiation, the observed decrease in carrier concentration with increase in ion fluence could be explained in the view of charge compensation by possible point defect trap centers, which can form because of elastic collisions of high energy ions with the target nuclei. In Si irradiated n‐GaAs one would expect the carrier compensation to occur at a fluence of 2.5 × 10¹³ ions/cm², if the same mechanism of acceptor state formation, as in case of O irradiation, is considered. However, we observe the charge compensation in this system at a fluence of 5 × 10¹² ions/cm². We discuss the role of the complex defect states, which are formed because of the interaction of the primary point defects, in determining carrier concentration in a Si irradiated n‐GaAs wafer. The above results are combined with the reported data from the literature for high energy silver ion irradiated n‐GaAs, in order to illustrate the effect of both electronic and nuclear energy loss on trap creation and charge compensation. Copyright © 2016 John Wiley & Sons, Ltd.     

DLTS and in situ C–V analysis of trap parameters in swift 50 MeV Li3+ ion-irradiated Ni/SiO2/Si MOS capacitors

Ni/SiO₂/Si MOS structures were fabricated on n-type Si wafers and were irradiated with 50 MeV Li³⁺ ions with fluences ranging from 1×10¹⁰ to 1×10¹² ions/cm². High frequency C–V characteristics are studied in situ to estimate the build-up of fixed and oxide charges. The nature of the charge build-up with ion fluence is analyzed. Defect levels in bulk Si and its properties such as activation energy, capture cross-section, trap concentration and carrier lifetimes are studied using deep-level transient spectroscopy. Electron traps with energies ranging from 0.069 to 0.523 eV are observed in Li ion-irradiated devices. The dependence of series resistance, substrate doping and accumulation capacitance on Li ion fluence are clearly explained. The study of dielectric properties (tan δ and quality factor) confirms the degradation of the oxide layer to a greater extent due to ion irradiation.     

Temperature dependent capacitance and DLTS studies of Ni/n-type 6H-SiC Schottky diode

Ni/n-type 6H-SiC Schottky barrier diode (SBD) has been characterized by the capacitance–voltage (C–V) technique as a function of temperature (120–500 K). The barrier height (BH) was determined as 1.36 eV at the temperature of 300 K and frequency of 50 kHz from C–V measurements, respectively. The BH for the Ni/n-type 6H-SiC does not exhibit temperature dependence between 260 and 500 K, while it changes slightly with decreasing temperature between 120 and 240 K. Deep level transient spectroscopy (DLTS) has been used to investigate deep levels in Ni/n-type 6H-SiC SBD. The four electron trap centers to be present at temperatures 120, 200, 350 and 415 K have been realized. The origin of these defects has been decided to be intrinsic nature and it has been found the correlation between C–V and DLTS measurements quite interesting.     

Effect of nitrogen ions on the structural,optical, and thermal properties of polyvinyl alcohol/starch blend

This work examines the properties of polyvinyl alcohol (PVA)/starch film containing glycerol as a plasticizer under exposure to different nitrogen ion fluence. The prepared PVA/starch blend was irradiated with ion fluence from 3 × 10¹⁷ to 12 × 10¹⁷ ions.cm⁻². From FTIR, the ion beam irradiation attack and weakens the C–H bond in PVA/starch blend. From XRD findings, the crystallite size of the blend decreased at 3 × 10¹⁷ ions/cm² while it increased at higher fluence up to 9 × 10¹⁷ ions/cm². This indicates the degradation of the blend at low ion fluence compared to crosslinking at high ion fluence. Also, the optical bandgap of the blend was decreased with an increase in ion fluence. Furthermore, the effect of N⁺ ions on some optical dispersion parameters is studied. The thermal stability of the PVA/starch blend shows a decrease in thermal stability upon irradiation with 3 × 10¹⁷ ions/cm² compared to higher thermal stability at higher doses up to 9 × 10¹⁷ ions/cm².     

Optical and electrical properties of swift heavy ion beam-irradiated polycarbonate/polystyrene bilayer films

Polycarbonate/polystyrene bilayer films prepared by solvent-casting method were irradiated with 55 MeV carbon ion beam at different fluences ranging from 1×10¹¹ to 1×10¹³ ions cm^?2. The structural, optical, surface morphology and dielectric properties of these films were investigated by X-ray diffraction (XRD), UV–visible spectroscopy, Fourier-transform infrared (FTIR) spectroscopy, optical microscopy and dielectric measurements. The XRD pattern shows that the percentage of crystallinity decreases while inter-chain separations increase with ion fluence. UV–visible spectroscopy shows that the energy band gap decreases and the number of carbon atoms in nanoclusters increase with the increase in ion fluences. The refractive index is also found to decrease with the increase in the ion fluence. Optical microscopy shows that after irradiation polymeric bilayer films color changes with ion fluences. The FTIR spectra evidenced a very small change in cross-linking and chain scissoring at high fluence. Dielectric constant decreases while dielectric loss and AC conductivity increase with ion fluences.     

Dielectric relaxation in NH4HSO4 above room temperature

The dispersion curves of the dielectric response of NH₄HSO₄ show that the corrected imaginary part of permittivity, εʺ, and its real part ε′ versus frequency reveal a dielectric relaxation around 9.1 × 10⁵ Hz at 31 °C, which shifts to higher frequencies (∼ 10⁶ Hz) as the temperatures increases. The relaxation frequency shows an activated relaxation process over the temperature range 31–83 °C with activation energy E_a = 0.14 eV, which is close to that derived from the dc conductivity. We suggest that the observed dielectric relaxation could be produced by the H⁺ jump and SO₄⁻ reorientation that cause distortion and change the local lattice polarizability inducing dipoles like HSO₄⁻.     

Dielectric relaxation properties of tysonite-type solid solutions La1−xBaxF3−x

Dielectric relaxation properties of solid solutions La_1?xBa_xF_3?x (x ? 0105) have been studied by thermally stimulated depolanzation current (TSDC)- and a c. dielectric loss (DL) techniques.For x < 30 × 10^?3 the dielectric spectra show a relaxation peak which is ascribed to a simple associate of a substitutional dopant ion and a fluoride ion vacancy (Ba_LaV_F)^x in nearest-neighbour position, the vacancy being confined to the B sublattice For x values of about 1.3 × 10^?2 a relaxation peak appears which is tentatively attributed to a similar type of defect associate with the vacancy now confined to the A sublattice of the tysonite anion array One broad relaxation peak dominates the TSDC and DL spectra over the whole concentration range This peak is due to the relaxation of macroscopic space charge, i e ionic conductivity The low-temperature ion conductivity has been determined for several solid solutions, and extrapolates to the high-temperature conductivity determined previously with impedance spectroscopy Below liquid-nitrogen temperature three relaxations are observed, and ascribed to electronic transitions in cenum impurities. A computer programme has been developed to analyse TSDC relaxation peaks, taking dipole-dipole interactions into account Relaxation parameters and dipole concentrations are presented.     

Thermo,Iono and photoluminescence properties of 100 MeV Si7+ ions bombarded CaSiO3:Eu3+ nanophosphor

This paper reports on the thermo (TL), iono (IL) and photoluminescence (PL) properties of nanocrystalline CaSiO₃:Eu³⁺ (1–5 mol %) bombarded with 100 MeV Si⁷⁺ ions for the first time. The effect of different dopant concentrations and influence of ion fluence has been discussed. The characteristic emission peaks ⁵D₀→⁷F_J (J=0, 1, 2, 3, 4) of Eu³⁺ ions was recorded in both PL (1×10¹¹–1×10¹³ ions cm^?2) and IL (4.16×10¹²–6.77×10¹² ions cm^?2) spectra. It is observed that PL intensity increases with ion fluence, whereas in IL the peaks intensity increases up to fluence 5.20×10¹² ions cm^?2, then it decreases. A well resolved TL glow peak at ～304 °C was recorded in all the ion bombarded samples at a warming rate of 5 °C s^?1. The TL intensity is found to be maximum at 5 mol% Eu³⁺ concentration. Further, TL intensity increases sub linearly with shifting of glow peak towards lower temperature with ion fluence.     

Corrosion behavior of tin ions implanted zirconium in 1N H2SO4

In order to study the effect of tin ion implantation on the aqueous corrosion behavior of zirconium, specimens were implanted with tin ions to a fluence ranging from 1 × 10²⁰ to 5 × 10²¹ ions/m², using a metal vapor vacuum arc source (MEVVA) at an extraction voltage of 40 kV. The valence states and depth distributions of elements in the surface layer were analyzed by X-ray photoelectron spectroscopy (XPS) and auger electron spectroscopy (AES) respectively. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to examine the micro-morphology and microstructure of tin-implanted samples. When the fluence was greater than 1 × 10²⁰ ions/m², many small tin balls were produced in the implanted surface. The potentiodynamic polarization technique was employed to evaluate the aqueous corrosion resistance of implanted zirconium in a 1N H₂SO₄ solution. It was found that a significant improvement was achieved in the aqueous corrosion resistance of zirconium implanted with 1 × 10²⁰ ions/m². When the fluence is higher than 1 × 10²⁰ ions/m², the corrosion resistance of zirconium implanted with tin ions decreased compared with that of the non-implanted zirconium. Finally, the mechanism of the corrosion behavior of the tin-implanted zirconium is discussed.     

Dielectric relaxation and AC conduction of an AgTlSe2 semiconductor in the solid and liquid states

Measurements of the dielectric properties of AgTlSe₂ in the solid and liquid states were carried out in a wide range of frequencies and temperatures. The material displayed dielectric dispersion, and a loss peak was observed. Cole-Cole diagrams have been used to determine the distribution parameter (a) and the molecular relaxation time (). The process of dielectric relaxation (loss) and ac conduction was attributed to the correlated barrier hopping model suggested by Elliott for amorphous solids, where two carriers simultaneously hop over a barrier between charged defectD ⁺ andD ^– states.     

Effect of H ion implantation on structural, morphological, optical and dielectric properties of l-arginine monohydrochloride monohydrate single crystals

l-arginine monohydrochloride monohydrate (LAHCl) single crystals have been implanted with 100 keV H⁺ ions at different ion fluence ranging from 10¹² to 10¹⁵ ions/cm². Implanted LAHCl single crystals have been investigated for property changes. Crystal surface and crystalline perfection of the pristine and implanted crystals were analyzed by atomic force microscope and high-resolution X-ray diffraction studies, respectively. Optical absorption bands induced by colour centers, refractive index and birefringence, mechanical stability and dielectric constant of implanted crystals were studied at different ion fluence and compared with that of pristine LAHCl single crystal.     

Nanostructures on GaAs surfaces due to 60 keV Ar+-ion beam sputtering

The effect of 60 keV Ar⁺-ion beam sputtering on the surface topography of p-type GaAs(1 0 0) was investigated by varying angle of incidence of the ion (0–60°) with respect to substrate normal and the ion fluence (2 × 10¹⁷–3 × 10¹⁸ ions/cm²) at an ion flux of 3.75 × 10¹³ ions/cm²-s. For normal incidence and at a fluence of 2 × 10¹⁷ ions/cm², holes and islands are observed with the former having an average size and density of 31 nm and 4.9 × 10⁹ holes/cm², respectively. For 30° and 45° off-normal incidence, in general, a smooth surface appears which is unaffected by increase of fluence. At 60° off-normal incidence dots are observed while for the highest fluence of 3 × 10¹⁸ ions/cm² early stage of ripple formation along with dots is observed with amplitude of 4 nm. The applicability and limitations of the existing theories of ion induced pattern formation to account for the observed surface topographies are discussed.     

Effect of swift heavy ion irradiation on thermal,optical and structural properties of poly vinylidene chloride

Poly vinylidene chloride (PVDC) irradiated with lithium (50 MeV), carbon (85 MeV), nickel (120 MeV) and silver ions (120 MeV) having fluence range of 1 × 10¹¹ ions/cm² to 3 × 10¹² ions/cm² have been studied using different techniques i.e. XRD (X-ray diffraction), FTIR (Fourier transform infrared), UV–Visible and TGA (thermo-gravimetric analysis). In XRD analysis, the intensity of diffraction peaks of PVDC irradiated with lithium ions was enhanced at lower fluence as compared to pristine. The shift in optical absorption edge in irradiated PVDC was correlated with the decrease in optical band gap energy. The distinguishable characteristic peaks were observed due to UV–Vis analysis, in lithium irradiated samples of PVDC at higher fluences. The % age decrease in optical band gap energy for the respective ions were 30.9%, 34.16%, 81.1%, 87.02% respectively. Formation of double carbon bonds and breaking of C–O and C–Cl bonds with the release of Cl in irradiated PVDC was observed in FTIR spectra. In Thermogravimetric analysis (TGA), the % age weight loss observed for irradiated samples with increase in ion fluence was lesser than the % age weight loss observed in pristine sample.     

Modification of the dielectric properties of copper-doped CdIn2S4 single crystal

The study of the dielectric properties of a CdIn₂S₄〈3 mol % Cu〉 single crystal in alternating-current (ac) electric fields with frequencies f = 5 × 10⁴?3.5 × 10⁷ Hz has revealed the origin of dielectric loss (relaxation loss that is changed by the through current loss at high frequencies). It has been found that CdIn₂S₄〈Cu〉 has permittivity increment Δ?′ = 123, relaxation frequency f _r = 2.3 × 10⁴ Hz, and relaxation time τ = 43 μs. The doping of CdIn₂S₄ single crystal with copper (3 mol %) is established to substantially increase the permittivity (?′), dielectric loss tangent (tanδ), and ac conductivity (σ_ac). In this case, the frequency dispersion of ?′ and tanδ increases and that of σ_ac decreases.     

The influence of annealing temperature and tellurium (Te) on electrical and dielectrical properties of Al/p-CIGSeTe/Mo Schottky diodes

p-CuIn_0.7Ga_0.3(Se_(1?x)Te_x)₂ type thin films were synthesized by thermal evaporation method on Mo coated glass substrates. To obtain Al/CuIn_0.7Ga_0.3(Se_(1?x)Te_x)₂/Mo Schottky diode structure for two compositions of x = 0.0 and 0.6, Al metal was evaporated on upper surface of CuIn_0.7Ga_0.3(Se_(1?x)Te_x)₂ as a front contact. Al/p-CuIn_0.7Ga_0.3(Se_(1?x)Te_x)₂/Mo structures were annealed temperature range from 150 °C to 300 °C for 10 min under vacuum. The electrical and dielectrical properties of Al/p-CuIn_0.7Ga_0.3(Se_(1?x)Te_x)₂ (CIGSeTe) Schottky barrier diodes (SBD) have been investigated. Capacitance–Voltage (C–V) characteristics, Conductance–Voltage (G/w–V) characteristics and interface state density were studied in order to obtain electrical and dielectrical parameters. The effects of interface state density (N_ss), series resistance (R_s), the dielectric constant (?′), dielectric loss (?″), dielectric loss tangent (tan δ), ac electrical conductivity (σ_ac) and carrier doping densities were calculated from the C–V and G/w–V measurements and plotted as a function of annealing temperature. It was observed that the values of carrier doping density N_A for annealing temperature at 150 °C decreased from 2.83 × 10⁺¹⁵ cm^?3 to 2.87 × 10⁺¹⁴ cm^?3 with increasing Te content from x = 0.0 to 0.6. The series resistance for x = 0.0 found to be between 10 and 75 Ω and between 50 and 230 Ω for x = 0.6 in the range of annealing temperature at 150–300 °C.     

The distribution of trapping states at the Al/InP-oxide interface

The volume density of trapping states is derived throughout the metal-dielectric interface. This has been facilitated by equating the dielectric loss component to the tunneling conductance using a new relaxation time formulation. Subsequently, the trap distribution at the Al/InPO₄ interface has featured a peak of 1.15×10¹⁹ cm^–3 at about 15 Å from the Al contacting electrode. The new approach could be extended to deal with semiconductor-dielectric interfaces.     

Effects of swift heavy ion irradiation on the electrical characteristics of Au/n-GaAs Schottky diodes

Metal-semiconductor diode of Au/n-GaAs is studied under the irradiation of swift heavy ion (SHI) beam (80 MeV ¹⁶O⁶⁺), using in situ current-voltage characterization technique. The diode parameters like ideality factor, barrier height, and leakage current are observed to vary with irradiation fluence. Significantly, the diode performance improves at a high fluence of 2 × 10¹³ ions cm⁻² with a large decrease of reverse leakage current in comparison to the original as deposited sample. The Schottky barrier height (SBH) also increases with fluence. At a high irradiation fluence of 5 × 10¹³ ions cm⁻² the SBH (0.62 ± 0.01 eV) is much larger than that of the as deposited sample (0.55 ± 0.01 eV). The diode parameters remain stable over a large range of irradiation up to fluence of 8 × 10¹³ ions cm⁻². A prominent annealing effect of the swift ion beam owing to moderate electronic excitation and high ratio of electronic energy loss to the nuclear loss is found to be responsible for the improvement in diode characteristics.     

Photostimulated luminescence properties of BaFBr:Eu under ion irradiation

The photostimulated luminescence (PSL) properties of the phosphor BaFBr:Eu after ion beam irradiation was analyzed; in particular, the PSL intensity dependent on ion fluence. The PSL intensity increased linearly with the ion fluence up to 10¹² ions/cm², and subsequently decreased gradually. The ion fluence dependence was observed to be similar among samples containing different F centers or different Eu concentrations. The fluence dependence was quantitatively analyzed based on a trapping model, in which competition between the trapping processes to storage centers and radiation defects is assumed; the model explained the experimental data quantitatively. The results indicate that radiation defects influence the PSL properties via the trapping of photostimulated electrons.     

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.     

Capacitance–voltage and conductance–voltage characteristics of Ag/n-CdO/p-Si MIS structure prepared by sol–gel method

The frequency dependent electrical properties of Ag/n-CdO/p-Si structure has been investigated using capacitance–voltage (C–V) and conductance–voltage (G/ω–V) characteristics in the frequency range 10 kHz–1 MHz in the room temperature. The increase in capacitance at lower frequencies is observed as a signature of interface states. The presence of the interfaces states (N_SS) is also evidenced as a peak in the capacitance–frequency characteristics. Furthermore, the voltage and frequency dependence of series resistance were calculated from the C–V and G/ω–V measurements and plotted as functions of voltage and frequency. The distribution profile of R_S–V gives a peak in the depletion region at low frequencies and disappears with increasing frequencies. The values of interface state densities and series resistance from capacitance–voltage-frequency (C–V-f) and conductance–voltage-frequency (G/ω–V-f) measurements were obtained in the ranges of 1.44×10¹⁶–7.59×10¹² cm^?2 eV^?1 and 341.49–8.77 Ω, respectively. The obtained results show that the C–V-f and G/ω–V-f characteristics confirm that the interface states density (N_SS) and series resistance (R_S) of the diode are important parameters that strongly influence the electrical parameters in Ag/n-CdO/p-Si structures.