High-energy heavy-ion induced physical and surface-chemical modifications in polycrystalline cadmium sulfide thin films

The effect of high electronic energy deposition on the structure, surface topography, optical properties, and electronic structure of cadmium sulfide (CdS) thin films have been investigated by irradiating the films with 100 MeV Ag⁺⁷ ions at different ion fluences in the range of 10¹²–10¹³ ions/cm². The CdS films were deposited on glass substrate by thermal evaporation, and the films studied in the present work are polycrystalline with crystallites preferentially oriented along (002)-H direction. It is shown that swift heavy ion (SHI) irradiation leads to grain agglomeration and hence an increase in the grain size at low ion fluences. The observed lattice compaction was related to irradiation induced polygonization. The optical band gap energy decreased after irradiation, possibly due to the combined effect of change in the grain size and in the creation of intermediate energy levels. Enhanced nonradiative recombination via additional deep levels, introduced by SHI irradiation was noticed from photoluminescence (PL) analysis. A shift in the core levels associated with the change in Fermi level position was realized from XPS analysis. The chemistry of CdS film surface was studied which showed profound chemisorption of oxygen on the surface of CdS.     

Influence of the defect state of samples on the luminescence spectra of CdS single crystals irradiated by electrons

The photoluminescence spectra of CdS single crystals irradiated by electrons (E = 1.2 MeV, Φ = 2×10¹⁷ cm^?2) are investigated in the visible and near-infrared regions of electromagnetic radiation. Some samples of the CdS single crystals are preliminarily irradiated by neutrons (E = 2 MeV, Φ = 2 × 10¹⁸ cm^?2) with the aim of increasing the concentration of initial structural defects. From analyzing the peak intensities of photoluminescence in the irradiated single crystals at the wavelengths λ_m = 0.720, 1.030, and 0.605 μm, it is concluded that the CdS samples with a low concentration of structural defects in the initial state possess the highest resistance to electron radiation. It is assumed that the observed transformation of the photoluminescence spectra of the imperfect CdS single crystals subjected to electron irradiation is determined by either the mechanisms of subthreshold defect formation or the transformation of the defect complexes in elastic and electric fields near the large structural damages of the crystal lattice.     

Anti-biofilm efficiency of 120 MeV Fe+9 SHI-irradiated polyimide film

ABSTRACT

Polyimide (PI) films were irradiated by 120 MeV iron (Fe⁺⁹) ions and variations in its optical, chemical, surface morphology and anti-bacterial properties were studied. UV-Visible spectroscopic results showed the decrease in the optical band gap of PI after irradiation due to the chain scission mainly at the carbonyl group which is corroborated by Fourier Transform Infrared spectroscopic results. The scanning electron microscopic results showed the surface roughening, surface structure broken and micro-porous formation in PI after irradiation. These results are also corroborated by the decrease in contact angle as studied by the contact angle measurement. PI films irradiated by 120 MeV Fe⁺⁹ ions showed increased anti-biofilm efficacy against the human pathogen, Salmonella typhi. In addition to this, the morphological changes were also observed due to the stress of Fe-irradiated PI. Biofilm formation was inhibited ≈ 35% at 1?×?10¹¹ ion/cm² and 80% at 5?×?10¹² ion/cm² in irradiated PI films. Thus, surface modification of PI films help in the inhibition of biofilm formation.

Highlights

1. Polyimide (PI) films were irradiated by 120?MeV Fe⁺⁹ ions.

2. Optical band gap of PI decreased after ion irradiation.

3. Surface roughening and micro-pores formation in PI after ion irradiation.

4. Surface modification of PI films helps in the inhibition of bio-film formation.

     

Low temperature electron irradiation of tellurium

Abstract

Tellurium single crystal samples with a hole concentration of 3 × 10¹⁴/cm² were irradiated at 10 K with electrons with an energy of 0.6 and 1 MeV. In the range investigated resistivity and Hall-coeficient R_H both decreased linearly with the integrated electron flux. The hole generation rate was 0.09 cm^?1 and 0.47 cm^?1 for 0.6 and 1 MeV electrons, respectively. The Hall-mobility R_H/P increased with irradiation.

Annealing of the radiation damage by raising the temperature clearly revealed three recovery stages in the resistivity- and Hall-data. At 180K p and R_H returned to their pre-irradiation values. The original Hall-mobility was already restored close to 90 K.

A more detailed study of the first recovery stage, which occurs at about 50 K, revealed an activation energy of 170±40meV. It is most likely, that the observed lattice defects are Frenkel-defects. There are indications, that the point defects interact with dislocations.     

Formation and growth of dislocation loops in ZnTe under irradiation of low energy Ar+-Ions

Abstract

Defects produced in ZnTe single crystals by Ar⁺ bombardment during ion milling for transmission electron microscopy studies are investigated in detail. The defects have been identified to be interstitial type Frank loops. Influences of ion energy and specimen temperature during the irradiation on the defect geometry are investigated. A model is proposed to describe the growing up of the loops.     

Study on the dynamic energy spectra of mev heavy ions penetrating biological sample

In order to study the probability for heavy ions to have a long projectile range in botanic sample, transmission energy spectra of 1.5 MeV F⁺, 3 MeV F²⁺ and 1.5 MeV H⁺ penetrating 100 µm seed cotyledon samples were measured as a function of ion dose. Results show that very fewer ions can penetrate through the samples, though their theoretical ranges are much shorter than sample thickness. Besides, the measured energy spectra of 1.5 MeV and 3.0 MeV F ions change dynamically while increasing the ion dose, they extend to the high energy direction and the count rates of the transmission ions increases quickly. These phenomena can be understood with the special composition and structure of the biological material.     

Accelerator irradiations of minerals: Implications for track formation mechanisms and for studies of lunar and meteoritic materials

Abstract

Natural crystals of feldspars, pyroxenes, quartz and apatite have been irradiated in the Berkeley HILAC with neon and argon ions of up to 10.2 MeV/amu with maximum doses of 1.6 × 10¹³ argon ions/cm² and 4.0 × 10¹³ neon ions/cm² respectively. The samples were thinned to thicknesses near 30 microns, stacked to form the target and then bathed completely in the ion beams. X-ray and optical observations revealed: (a) a crystal distortion and curvature with the argon irradiation similar to that produced in mica; (b) a lesser effect from neon bombardment; (c) a fracturing of the crystal samples which depended on the total dose and energy of the incident ion; (d) polygonized structures produced when either neon or argon ions (with sufficiently high concentration) were trapped within the crystals. The interpretation of the measurements, their correlation with the mechanism of track formation and implications concerning the alteration of the lunar surface due to solar particles and the exposure of lunar and meteoritic material in the ancient solar flare cosmic rays are discussed.     

Spatial distribution, build-up, and annealing of radiation defects in silicon implanted by high-energy krypton and xenon ions

An x-ray diffraction study of defect formation in silicon irradiated by Kr⁺ (210 MeV, 8×10¹²−3×10¹⁴ cm⁻²) and Xe⁺ (5.6 BeV, 5×10¹¹−5×10¹³ cm⁻²) ions is reported. It has been established that irradiation produces a defect structure in the bulk of silicon, which consists of ion tracks whose density of material is lower than that of the host. The specific features of defect formation are discussed taking into account the channeling of part of the ions along the previously formed tracks and the dominant role of electron losses suffered by the high-energy ions. It is shown that the efficiency of incorporation of stable defects by irradiation with high-energy ions is lower than that reached by implanting medium-mass ions with energies of a few hundred keV. Fiz. Tverd. Tela (St. Petersburg) 40, 1627–1630 (September 1998)     

Electrical and structural properties of the swift heavy ion irradiated Au/n-GaAs schottky barrier diodes

Abstract

Au/n-GaAs Schottky Barrier Diodes (SBDs) have been fabricated on LEC grown silicon doped (100) GaAs single crystals. The SBDs were irradiated using high energy (120 MeV) silicon ion with fluences of 1 × 10 ¹¹ and 1 × 10¹² ions/cm². Current-Voltage (I-V) characteristics of unirradiated and irradiated diodes were analyzed. The change in the reverse leakage current increases with increasing ion fluence. This is due to the irradiation induced defects at the interface and its increase with the fluence. The diodes were annealed at 573 and 673 K. to study the effect of annealing. The rectifying behavior of the irradiated (fluence of 1 × 10¹² ions/cm¹²) SBDs improves upon as the annealing temperature increases and is attributed to the in situ self-annealing during irradiation. Scanning Electron Microscopic analysis was carried out on the irradiated samples to delineate the projected range and to observe defects.     

Radiation damage in triglycine sulphate due to fast neutron irradiation

Abstract

The change in electrical properties of TGS crystals due to induced defects created by fast neutron irradiation of two different energies (2 and 14 MeV) and different integrated neutron fluxes have been studied in the vicinity of phase transition. It is observed that the electrical conductivity increases with increase of neutron fluence up to 1.7 × 10¹⁰ n · cm^?2 and the values of the relative change of electrical conductivity in case of 2 MeV are higher than that of 14 MeV neutrons at the same neutron fluence (φ)     

Structure of crystallized layers by laser annealing of 〈100〉 and 〈111〉 self-implanted silicon samples

Channeling effect techniques with a 2.0 MeV He⁺ Rutherford backscattering and transmission electron microscopy were used to characterize the crystallized layers after Q-switched ruby laser irradiation of 4000 Å thick amorphous layer on 〈100〉 and 〈111〉 underlined crystal substrates. At a laser energy density of 2.5 J/cm² the crystal layer on the 〈111〉 specimen contains a large density of stacking-faults, that on 〈100〉 specimen contains a very small amount of screw dislocation lines. High quality single-crystal layers have been obtained after irradiation at 3.5 J/cm². From a comparison with the growth rate and defect structure observed in thermally annealed implanted-amorphous layers, we propose that crystal growth by 50 ns pulse laser annealing occurs by melting the amorphous layer.     

Induced absorption in yttrium aluminium perovskite crystals irradiated by 12C and 235U ions

The present work is devoted to investigation of optical absorption in pure and neodymium-doped YAlO₃ (YAP) single crystals in the spectral range 0.2–1.1 μm induced by the influence of ¹²C ions irradiation with energy 4.50 MeV/u (MeV per nucleon) and a fluence 2 × 10⁹ cm^?2 or of ²³⁵U ion irradiation with energy 9.35 MeV/u and a fluence 5 × 10¹¹ cm^?2. The induced absorption in the case of ¹²C ions irradiation is caused by recharging of point growth defects and impurities under the radiation influence. After irradiation by ²³⁵U ions with fluence 5 × 10¹¹ cm^?2 the strong absorption rise is probably caused by contribution of the lattice destruction as a result of heavy ion bombardment.     

Convoy electrons produced at glancing angle scattering of MeV HeH+ ions from a crystal surface

Abstract

Convoy electrons produced at glancing angle scattering of MeV HeH⁺ ions from an atomically clean (001) surface of SnTe crystal are observed. Energy spectrum of the convoy electrons shows a peak broader than that at scattering of atomic projectiles and the most probable energy of convoy electrons at HeH⁺ scattering is larger than those at scattering of isotachic He ions. This acceleration of convoy electrons is qualitatively explained by the force due to surface wake induced by Coulomb exploding fragment He²⁺ and H⁺.     

Effect of Si ion irradiation on polycrystalline CdS thin film grown from novel photochemical deposition technique

CdS thin films have been deposited from aqueous solution by photochemical reactions. The solution contains Cd(CH₃COO)₂ and Na₂S₂O₃, and pH is controlled in an acidic region by adding H₂SO₄. The solution is illuminated with light from a high-pressure mercury-arc lamp. CdS thin films are formed on a glass substrate by the heterogeneous nucleation and the deposited thin films have been subjected to high-energy Si ion irradiations. Si ion irradiation has been performed with an energy of 80 MeV at fluences of 1×10¹¹, 1×10¹², 1×10¹³ and 1×10¹⁴ ions/cm² using tandem pelletron accelerator. The irradiation-induced changes in CdS thin films are studied using XRD, Raman spectroscopy and photoluminescence. Broadening of the PL emission peak were observed with increasing irradiation fluence, which could be attributed to the band tailing effect of the Si ion irradiation. The lattice disorder takes place at high Si ion fluences.     

Fundamental analysis of defects induced by energetic ions implantation in AgCl

The effects of the energetic ions implantation in AgCl can be related to two types of perturbation due to: the electronic energy losses observed, essentially with H⁺ (2 MeV) implantation and the collision energy losses illustrated in K⁺ (0.5 MeV) implantation.

The ionization influence is essentially the sensibilization of AgCl (print-out) at RT and at LNT. We discuss the the photolysis mechanism regarding the one postulated under action of light.

The defects related to collision losses are characterized by a new optical absorption band with a characteristic length independent of the implanted ion (Na⁺ and K⁺). The nature of those defects are analysed by thermal and optical bleaching and by EPR. Those collision effects do not contribute to the print-out phenomena.     

Structural phase transformation in ZnS nanocrystalline thin films by swift heavy ion irradiation

Zinc sulfide (ZnS) thin films in zinc-blende (ZB) and wurtzite (W) phases have been fabricated by pulsed laser deposition. 150 MeV Ni ion beam irradiation has been carried out at different fluences ranging from 10¹¹ to 10¹³ ions/cm² at room temperature for ion induced modifications. Structural phase transformation in ZnS from W to ZB phase is observed after high energy ion irradiation which leads to the decrease in bandgap. Generation of high pressure and temperature by thermal spike during MeV ion irradiation along the ion trajectory in the films is responsible for the structural phase transformation.     

Aggregation of radiation defects in AIN ceramics under He+ ion irradiation

Abstract

The aggregation of F-type defects in AIN has been observed for the first time under He⁺ ion irradiation by using in-situ luminescence measurement. The concentration of aggregation of F-type defects shows a strong dependence on irradiation temperature (300–773 K) under He⁺ ion irradiation. The mechanism of growth and annihilation of the aggregation of F-type defects was discussed.     

Combined field ion microscopy and transmission electron microscopy of heavy ion damage in tungsten

Abstract

A field ion microscopy (FIM) and transmission electron microscopy (TEM) investigation of radiation damage in tungsten after heavy ion bombardment has been carried out. Field ion specimens of tungsten were irradiated with 180–230 keV Xe⁺ ions. The irradiation doses were varied between 4 × 10¹¹ and 4 × 10¹² ions/cm². The irradiated specimens were examined in FIM. Experiments combining both TEM and FIM were performed in order to compare the results obtainable by these two methods. The distribution of defects visible by TEM was inhomogeneous. The influence of the imaging field in FIM on the defects visible in TEM is discussed.     

Interplay of native defect-related photoluminescence response of ZnO nanosticks subjected to 80 keV Ar ion irradiation

We report on the effect of 80 keV Ar⁺ ion irradiation on the luminescence response of zinc oxide (ZnO) nanosticks synthesized using a simple microemulsion route. The formation of nanoscale rods was confirmed from the transmission electron microscopy, whereas the hexagonal wurtzite phase of the nanorods was detected in an X-ray diffraction pattern. The photoluminescence pattern of the nanorods was dominated by various native defect states of ZnO, which are responsible for the quenching of the typical band edge emission of ZnO. Under Ar⁺ ion irradiation at a fluence of 1×10¹³ ions/cm², the band edge emission was recovered owing to the suppression of oxygen vacancy defects. In addition, the formation of new zinc vacancy and ionized zinc interstitial defects were also evident. Conversely, the band edge emission was found to be quenched as a result of the creation of more oxygen vacancy (V_O) defects due to ion irradiation (fluence: 1×10¹⁵ ions/cm²). The nuclear energy loss of the Ar⁺ ions in ZnO is responsible for the formation of point (vacancy-related) defects, while relatively small amount of electronic energy loss of the Ar⁺ ion results in the ionization of the neutral zinc interstitial (Zn_i) defects. The energy deposition scheme of the energetic ions has been elaborated with the help of theoretical modeling that explains the observed features quite satisfactorily.     

Time-resolved defect production and annealing during electron-beam processing of silicon

In (100)p-Si radiation damage was produced by implanting B⁺ ions with an energy of 80keV, 90keV and 1.6MeV. The specimens were annealed by scanned electronbeam irradiation (20keV, 1–2mAcm^–2). The formation, evolution and annihilation of defects during the irradiation process were investigated by employing DLTS and RBS measuring techniques. The results show a minimum of defect concentration and an efficiency of the electrical activation of B higher than 80% at an annealing time of 4.5 s. For irradiation times longer than 5 s it becomes evident, that the crystal surface acts as source of defects and contributes to an increase in defect concentration.