Annealing of γ-ray irradiated lithium compensated p-type silicon

Abstract

Annealing behavior of electrical properties and photoluminescence spectra both at 77 °K in electron-irradiated melt-grown n-GaAs were investigated. Defects electrically active in the Hall mobility and carrier removal anneal through two stages centered at 250° and 460 °K. From the temperature dependence of carrier concentration the existence of a defect level located near 0.15 eV below the conduction band is supposed. Several emission bands are resolved at 1.51, 1.47, 1.415, 1.305 and ～1.2 eV in photoluminescence experiments. Electron irradiation (1.5–2.0 MeV) causes a remarkable decrease in emission intensity of 1.51 and ～1.2 eV bands. Recovery of emission intensity occurs remarkably when samples are annealed to 520 °K which would correspond to the 460 °K annealing stage for carrier concentration and Hall mobility. The 250 °K annealing stage is not observed in photoluminescence experiments. The 1.415 eV peak appears clearly after irradiation and grows remarkably with the 520 °K annealing, especially in Si-doped samples, resulting in large reverse annealing. This band is tentatively speculated to be a complex of Si on As site with As vacancy. Moreover, in samples doped with Te a new emission band at 1.305 eV (9500 Å) is observed after 470°–620 °K annealing.     

Optical properties of oxygen-deficiency related centers in amorphous SiO 2 investigated by synchrotron radiation

We report an investigation of the photoluminescence activity at 4.4 v eV in g -irradiated silica under UV and vacuum-UV excitation by synchrotron radiation. Our results evidence two iso-energetic contributions which can be related to two oxygen-deficient centers variants: ODC(I) and ODC(II). The first, excited within the 7.6 v eV absorption, is detected only at low temperature and has a lifetime of about 2 v ns. The second exhibits two excitation maxima peaked at 5.0 and 6.8 v eV, its amplitude decreases by a factor 2 on increasing the temperature whereas its lifetime has a value of about 4 v ns. These features give new insights on the excitation pathway of the 4.4 v eV emission involving the conversion from ODC(I) towards ODC(II).     

Photoluminescence in γ-irradiated α-quartz investigated by synchrotron radiation

We report an experimental investigation of the photoluminescence, under excitation by synchrotron radiation within the absorption band at 7.6 eV, induced in γ-irradiated α-quartz. Two emissions centered at 4.9 and 2.7 eV are observed at low temperature: the former decreases above 40 K, whereas the second band exhibits an initial slight increase and its quenching is effective above 100 K. Furthermore, the decay kinetics of both emissions occur in a time scale of nanoseconds: at T=17.5 K we measured a lifetime τ1.0 ns for the photoluminescence at 4.9 eV and τ3.6 ns for that at 2.7 eV. These results give new insight on the optical properties associated with defects peculiar of crystalline matrix, also on the basis of their comparison with previous studies on silica.     

Ge：SiO2的光敏缺陷的研究

研究了Ｇｅ；ＳｉＯ２光敏缺陷的特性，分别在４８８ｎｍＡｒ离子激光与１９３ｎｍＡｒ准分子激光作用下，由紫外吸收带，激光荧光的测量实验及电子自旋共振实验，发现光纤中５．１ｅＶ锗缺陷吸收带实验上是由５．０６ｅＶ可光致漂白带与５．１７ｅＶ不可漂白带组成；２９５ｎｍ的激发荧光与５．０６ｅＶ的缺氧锗缺陷对应，随５．０６ｅＶ缺陷吸收带的漂白而衰减；     

Surface modification of Makrofol-DE induced by α-particles

In the present work, Makrofol DE samples were irradiated with different doses of alpha particles. The optical and mechanical modifications in the alpha-irradiated Makrofol samples as a function of alpha irradiation time have been investigated. Different characterization techniques, UV–vis spectroscopy, photoluminescence spectroscopy and Vickers micro hardness tester have been used. UV–vis spectra of bombarded samples reveal that the optical absorption increases with increasing the irradiation time. The direct and indirect optical band gap was found to decrease from 3.4 and 2.81?eV for pristine sample to 3.1 and 2.35?eV for that bombarded with alpha particles at the highest irradiation time (15?h), respectively. The number of carbon atoms per conjugated length (N) and the number of carbon atoms per cluster (M) have been estimated. An increase in both N and M with increasing the irradiation time was noticed. A remarkable decrease in PL intensity with increasing the alpha irradiation time was observed. This decrease is attributed to ion beam-induced change in molecular structure and/or defects in the modified layer. The surface hardness for unmodified and modified polymeric material has been studied.     

Spectral,X-ray diffraction,surface morphological and thermal studies of gamma-irradiated potassium bis(oxalato)zincate(II)dihydrate

ABSTRACT

Potassium bis(oxalato)zincate(II)dihydrate was prepared and characterized. The sample was irradiated with ⁶⁰Co gamma rays up to 900?kGy. Infrared, Raman and photoluminescence spectra, X-ray diffraction pattern, surface morphology by AFM and SEM and non-isothermal decomposition of the complex were studied before and after irradiation. Spectral studies suggested significant radiation damage. X-ray diffraction studies showed reduction in unit cell volume and average crystallite size. Both unirradiated and irradiated samples of the complex belong to the hexagonal crystal system. Surface morphology of the complex changed upon irradiation. Thermal decomposition was enhanced.     

Room temperature photoluminescence from Zr-doped sol-gel silica

Intense room-temperature photoluminescence (PL) from the UV to the green region was observed from Zr⁴⁺-doped silica synthesized by a sol-gel process using tetraethoxysilane as the precursor, followed by thermal treatment at 500 °C in air. The wide PL band can be resolved into three components centered at 3.70, 3.25, and 2.65 eV, respectively. The intensity of the 3.25 and 2.65 eV PL bands was greatly enhanced compared with pure sol-gel silica. The 3.70 eV emission was assigned to non-bridging oxygen hole centers, while the 2.65 eV one originated from neutral oxygen vacancies (V_O). The 3.25 eV PL band was most likely associated with E′ centers, as supported by electron spin resonance measurement. It was proposed that the Zr⁴⁺-doping leads to oxygen deficiency in the silica, thus resulting in enhancement of the density of V_O and E′ center defects.     

Photoluminescence and positron annihilation spectroscopic investigation on a H(+) irradiated ZnO single crystal

Low temperature photoluminescence and room temperature positron annihilation spectroscopy have been employed to investigate the defects incorporated by 6?MeV H(+) ions in a hydrothermally grown ZnO single crystal. Prior to irradiation, the emission from donor bound excitons is at 3.378?eV (10?K). The irradiation creates an intense and narrow emission at 3.368?eV (10?K). The intensity of this peak is nearly four times that of the dominant near band edge peak of the pristine crystal. The characteristic features of the 3.368?eV emission indicate its origin as a 'hydrogen at oxygen vacancy' type defect. The positron annihilation lifetime measurement reveals a single component lifetime spectrum for both the unirradiated (164?±?1?ps) and irradiated crystal (175?±?1?ps). It reflects the fact that the positron lifetime and intensity of the new irradiation driven defect species are a little higher compared to those in the unirradiated crystal. However, the estimated defect concentration, even considering the high dynamic defect annihilation rate in ZnO, comes out to be ～4?×?10(17)?cm(-3) (using SRIM software). This is a very high defect concentration compared to the defect sensitivity of positron annihilation spectroscopy. A probable reason is the partial filling of the incorporated vacancies (positron traps), which in ZnO are zinc vacancies. The positron lifetime of ～175?ps (in irradiated ZnO) is consistent with recent theoretical calculations for partially hydrogen-filled zinc vacancies in ZnO. Passivation of oxygen vacancies by hydrogen is also reflected in the photoluminescence results. A possible reason for such vacancy filling (at both Zn and O sites) due to irradiation has also been discussed.     

Electrical characteristics of ion-implanted laser-annealed silicon

The present paper summarizes recent experiments at the JRC, aiming to determine the relative damage effects produced in a-SiO2 by particles of different mass and energy, so as to correlate typical defects with specific production mechanisms. By systematic analysis of optical absorption spectra, the main colour centres that are currently associated with primary irradiation effects were characterized. Centres responsible for the B₂-band (5.04 eV) and E'-band (5.78 eV) were quantitatively investigated with respect to particle type, production yield and saturation behaviour. Arguments taken from energy loss and dpa seem to suggest that the E' centre is based on a stable structural substrate, which is not reconciled with simple ideas of a broken bond. The B₂ centre is confirmed to be associated with atomic defects produced by collisions. New determinations in the vacuum u.v., performed on heavy-ion irradiated samples, seem to put this centre in quantitative relationship to a centre responsible for a 7.15 eV absorption.     

Analysis of 1 MeV electron irradiation-induced performance degradation in the germanium bottom cell of triple-junction solar cells using temperature-dependent photoluminescence measurements

Abstract

Temperature-dependent photoluminescence spectra of the germanium bottom cell of triple-junction solar cells unirradiated and irradiated with 1?MeV electrons were measured in the 10–300?K temperature range. In unirradiated germanium bottom cell, the spectra show that the PL intensity increases with temperature but slightly decreases at around 250?K because of the intrinsic defect. However, in irradiated germanium bottom cell, the spectra show that there are two negative thermal quenching processes (10–90?K and 200–270?K) and two usual thermal quenching processes (90–200?K and 270–300?K) as a result of the radiation-induced defects E_c ? 0.37?eV and E_c ? 0.12?eV.     

Radiation damage produced in quartz by energetic ions

Abstract

Present work deals with atomic and electronic alterations of the quartz structure by high energy ion irradiation. The atomic structure of irradiated quartz is probed by means of X-ray absorption spectroscopies (XANES, EXAFS). Electronic structure modifications are investigated by XPS and bulk paramagnetic point defects by ESR. The experimental data suggest that for light ions (O), irradiated quartz targets preserve their long range order. E' point defects, i.e. oxygen vacancy defects, are created along the ion path with a poor efficiency (2 GeV/E'), close to the efficiency of y rays. For heavier ions (Kr, Pb), irradiation damage consists of a trail of extended defects. These extended defects are composed of an amorphous SiO₂ state. The density of these amorphized regions is about 4% larger than the common relaxed silica. This poorly densified silica appears similar to that obtained by neutron irradiation of quartz. E’ defects are mostly located inside these amorphous zones (>85%).     

Controlling surface states and photoluminescence of porous silicon by low-energy-ion irradiation

Porous silicon (PS) was irradiated by three kinds of low-energy ions with different chemical activity, namely argon ions, nitrogen ions and oxygen ions. The chemical activity of ions has significant effect on the surface states and photoluminescence (PL) properties of PS, The photoluminescence quenching after argon ions and nitrogen ions irradiation is ascribed to the broken Si-Si bonds, while the PL recovery is attributed to the oxidation of Si-H back bonds. Oxygen ions irradiation leads to the formation of a SiO_x layer with oxygen defects and PS shows different PL evolution than PS irradiated by argon ions and nitrogen ions.     

Transient optical absorption of excited F -centres in BeO

Time-resolved spectra, decay kinetics and polarization of the transient optical absorption induced by irradiation of additively colored BeO crystals with electron pulses have been studied. It has been established that the two bands at 3.8 and 4.3 v eV of the transient optical absorption are due to the transitions between triplet and singlet excited states of F -centres in BeO. The polarization of excited F -centres absorption is discussed on the basis of analysis of the splitting of singlet and triplet states in crystalline field of the C 3v symmetry.     

Creation of paramagnetic defects by gamma irradiation in amorphous silica

An electron spin resonance (ESR) study of the defects induced by γ-rays in various types of natural and synthetic silica is reported. Three main structures were identified: the E′ center and two doublets with field splitting of 7.4 and 11.8 mT, respectively, both centered around the E′ center signal. Another structure partially overlapping the E′ center line was also detected, consisting in three peaks with a maximum field splitting of 1.36 mT. We have investigated the growth kinetics of these centers on increasing the y-ray accumulated dose. In all investigated materials the growth of E′ centers can be interpreted as caused by γ-activated conversion of one or more precursors. The 1.36 mT structure can be considered as a hyperfine structure of the E′ centers generated by the same precursors but interacting with a nuclear spin. The 7.4 mT doublet features a sublinear growth with the γ dose in the whole investigated range (from 0.01 to 1000 Mrad) and a strict correlation with the γ-induced photoluminescence band at 4.4 eV. Finally the 11.8 mT doublet is generated only in natural silica samples and can be related to the γ-induced bleaching of the emission bands at 3.1 and 4.2 eV.     

Ultrasonic detection of the pinning of dislocations by point defects in lead-I determination of migration energies

The ultrasonic attenuation of a γ-irradiated, deformed, single-crystal of lead has been measured between 77 and 270 K. Constant heating rate and isothermal anneals after low temperature irradiation yielded two dislocation pinning stages centered at 140 and 200 K and two dislocation depinning stages centered about 170 and 250 K. For an unirradiated sample one pinning stage centered at 170 and one depinning stage centered at 250 K were observed. Activation energies were calculated from isothermal anneals using an eigenfunction expansion model to be 0·16±0·04 and 0·36±0·05 eV for the pinning stages in the irradiated crystal and 0·28±0·05 eV for the pinning stage in the unirradiated crystal. The activation energy calculated from the same isothermal anneals using a Cottrell-Bilby analysis was 0·23±0·03 eV for the low temperature pinning stage in the irradiated crystal. The other activation energies were not changed. The discrepancy is discussed in Part II.     

Influences of KrF laser irradiation on the structure and luminescence of ZnO single crystal

<正>In this paper,we investigate the laser irradiation of ZnO single crystals and its influence on photoluminescence.Our study shows that the photoluminescence of ZnO single crystals strongly depends on surface morphologies.The ultraviolet emissions of laser treated-ZnO under 200 mJ/cm~2 become stronger,whereas for those deteriorated by irradiation above 200 mJ/cm~2,the green emissions centred at 2.53 eV are significantly enhanced with a red-shift to 2.19 eV,probably due to the changes in the charge states of the defects.Enhanced yellow-green emissions are well resolved into four peaks at around 1.98,2.19,2.36,and 2.53 eV due to a shallow irradiation depth.Possible origins are proposed and discussed.     

UV cathodoluminescence of crystalline α-quartz at low temperatures

Two luminescence bands in the UV range were detected in crystalline α-quartz under electron beam excitation (6 kV, 3-5 μA). One band is situated at 5 eV and could be observed in pure samples. Its intensity increases with cooling below 100 K and undergoes saturation below 40 K alongside a slow growth with the time of irradiation at 9 K. The decay curve of the band at 5 eV contains two components, a fast (<10 ns) and a slow one in the range of 200 μs. The photoluminescence band at 5 eV with a similar temperature dependence was found in previously neutron-irradiated crystalline α-quartz. Therefore, the band at 5 eV was attributed to host material defects in both irradiation cases. The creation mechanism of such defects by electrons, the energy of which is lower than the threshold for a knock-out mechanism of defect creation, is discussed. Another band at 6 eV, containing subbands in different samples, appears in the samples containing aluminum, lithium and sodium ions. This luminescence is ascribed to a tunnel radiative transition in an association of (alkali atom)⁰-[AlO₄]⁺ that is formed after the trapping of an electron and a hole by Li⁺ (or Na⁺) and AlO₄.     

Spectral heterogeneity of oxygen-deficient centers in Ge-doped silica

We report an experimental investigation of the emission spectra of a 1000 mol ppm sol–gel Ge-doped silica by fine tuning the excitation energy in the ultraviolet (UV) range, around 5 eV, and in the vacuum-UV range, around 7.3 eV, at room temperature and at 10 K. The sample is characterized by a blue (centered at 3.2 eV) and an UV (centered at 4.3 eV) bands. We have found that the ratio between the area of the blue and the UV bands depends on the temperature and on the excitation energy in both the vacuum-UV and the UV range. At both temperatures the spectral features of the blue and the UV bands are weakly affected when the excitation is varied in the vacuum-UV. At variance, under UV excitation the peaks of the bands are shifted and also their widths are changed. These results are interpreted in terms of distinct excitation channels of the luminescence that are influenced in a different way by the structural inhomogeneity of point defects.     

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.     

Latent track creation in fused silica by 200 MeV silver beam

Studies of formation of latent tracks in swift heavy ion irradiated SiO₂ are presented. Fused silica (SiO₂) were irradiated with 200 MeV silver (Ag) ion beam at varying fluences. Radiation-induced effects were studied by ultraviolet(UV)/Visible optical absorption spectroscopy and transmission electron microscopy (TEM). UV/Visible absorption study indicated E′ centers and oxygen deficiency centers having characteristic absorption occurred at 5 eV. The density of these color centers calculated from the absorption peak intensity showed Poisson-type variation with irradiation fluence. The defects are thus entirely confined to the latent tracks created by swift heavy ions in SiO₂. The track radius estimated from optical absorption study was found to be 5.1 nm. Similar results were obtained from TEM studies of the irradiated samples.