Solid State Phenomena Vol. 239

Abstract: The irradiation of nanomaterials with energetic particles has significant effects on the properties of target materials. In addition to the well-known detrimental effects of irradiations, they have also some beneficial effects on the properties of nanomaterials. Irradiation effect can change the morphology of the materials in a controlled manner and tailor their mechanical, structural, optical and electrical properties. Irradiation induced modifications in the properties of nanomaterials can be exploited for many useful applications. With the aim of getting better performance of electronic devices, it is necessary to discuss the irradiation induced changes in the nanomaterials. In order to improve the irradiation hardness of electronic components, it is also crucial to have a fundamental understanding of the impact of the irradiation on the defect states and transport properties of the host material. In the present article, we review some recent advances on the irradiation induced effects on the properties of semiconducting nanomaterials. We have reviewed the effect of different types of irradiations which includes γ-irradiation, electron beam irradiation, laser irradiation, swift heavy ion irradiations, thermal induced, and optical induced irradiations, etc. on the various properties of semiconducting nanomaterials. In addition, the irradiation induced defects are also discussed.

Abstract: Silicon bipolar junction transistors (BJTs), Silicon-germanium heterojunction bipolar transistors (SiGe HBTs) and metal oxide semiconductor (MOS) devices are the key components of BiCMOS integrated circuits. The semiconductor devices need to withstand very high total doses (100’s of Mrad) for reliable operation of electronic circuits for 8-10 years of LHC operation. The study of radiation tolerance of semiconductor devices up to 100 Mrad of total dose takes longer time with conventional ⁶⁰Co gamma, proton and electron irradiation facilities and the effects due to these radiations are well understood. Hence it is important to study the effects of heavy ion irradiation on various semiconductor devices. The irradiation time decreases with increasing linear energy transfer (LET) of incident radiation and LET increases with atomic number of the impinging ions. But it is essential to understand the mechanism of energy transfer by different heavy ions in semiconductor devices. Therefore, here we give an overview of different heavy ion interactions with Si BJTs, MOSFETs and SiGe HBTs by primarily focusing on the electrical characteristics of these devices before and after ion irradiation. We show that the irradiation time needed to reach very high total dose can be reduced by using Pelletron accelerator facilities instead of conventional irradiation facilities.

Abstract: The interaction of electron-beam with organic materials (e.g. Polymers, organic solvents, organic acids etc.) is known to modify their physico-chemical properties and, in many cases, these electron-beam modified materials are used for variety of societal applications. In this review article, we first describe the various types of accelerators to generate electron-beams of different energies, i.e. low (0.3 – 0.75 MeV), medium (0.75– 5 MeV) and high (5 – 10 MeV) energies, and emphasis is laid on various accelerators developed by Bhabha Atomic Research Center (BARC), Trombay, India. The energetic electrons on interaction with organic materials create free radicals that lead to modifications in material through various mechanisms such as, cross-linking, scissioning, curing and grafting. An overview of these mechanisms is presented by citing appropriate examples. Applications of electron beam-modified organic materials in different areas including bio-medical, textile, environment protection, electrical, radiation dosimetry, etc. are reviewed. The prospects and challenges involved in the electron-beam processing of organic materials are presented.

Abstract: The effects of gamma radiations on the optical, physical and structural properties of zinc lead borate xZnO-2xPbO-(1-3x)B₂O₃ and zinc lead borosilicate xZnO-2xPbO-1/2(1-3x)B₂O₃-1/2(1-3x)SiO₂ glasses have been investigated. Differential Scanning Calorimetry (DSC), Ultraviolet-Visible (UV-Vis) and Fourier Transmission Infra-red (FTIR) spectroscopic techniques have been used to compare the properties of samples before and after gamma irradiation by a dose of 2.5 kGy. The variation of density, optical band gap (E_g), IR absorption bands and glass transition temperature (T_g) indicates that the structure of glasses changes due to irradiation. The radiation induced changes created by-ray in the optical, physical and thermal parameters in both the prepared series of glasses have been discussed for their possible application as radiation shielding material.

Abstract: Polymers are a class of materials widely used in different fields of applications. With imminent applications of polymers, the study of radiation induced changes in polymers has become an obvious scientific demand. The bombardment by ion beam radiations has become one of the most promising techniques in present day polymer research. When the polymers are irradiated, a variety of physical and chemical changes takes place due to energy deposition of the radiation in the polymer matrix. Scissoring, cross-linking, recombination, radical decomposition, etc. are some of the interesting changes that are obvious in polymers. The modification in polymer properties by irradiation depends mainly on the nature of radiation and the type of polymer used.Polymer electrolytes are obtained by modifying polymers by doping, complexing, or other chemical processes. In general, they suffer from low conductivity due to high crystallinity of the matrix. The effect of radiation on polymer electrolyte is expected to alter their crystalline nature vis-a-vis electrical properties. This review article shall elaborate modifications in the physical and chemical properties of polymer electrolytes and their composites. The variations in properties have been explored on PEO based polymer electrolyte and correlated with the parameters responsible for such changes. Also a comparison with different types of the polymers irradiated with a wide range of ion beams has been established.

Abstract: Ion beam bombardment has shown great potential for improving the surface properties of polymers. In this paper, the ion beam-polymer interaction mechanisms are briefly discussed. The main objective of this research was to study the effects of H-ion beam on physico-chemical properties of Ultra-high-molecular-weight polyethylene (UHMWPE) as it is frequently used in biomedical applications. UHMWPE was bombarded with 65 keV H-ions to fluences ranging from 1x10¹⁴–2x10¹⁶ ions/cm². Changes of surface layer composition produced by ion bombardment of UHMWPE samples were studied. The hydrogen release and oxygen uptake induced by ion beam bombardment were determined by Nuclear reaction analysis (NRA) using the ¹H(¹⁵N, αγ)¹²C and Rutherford backscattering spectrometry (RBS), respectively. Tribological and hardness properties at the polymer near surface region were studied by means of friction coefficient and micro-hardness testers, respectively. Wettability of the bombarded surfaces was determined by measuring the contact angle for distilled water. The obtained results showed that the ion bombardment induced hydrogen release increases with the increasing ion fluence. An important effect observed, was the rapid oxidation of samples, which occurs after exposure of bombarded samples to air. These effects resulted in important modifications of the surface properties of bombarded material such as change of friction coefficient, hardness and improved wettability.

Abstract: The effects of plasma exposure and impingement of energetic particles are now widely used for substrate cleaning as well as to assist and control thin film growth and various applications. Plasma technology is a versatile green technology used for surface engineering technology. Plasma sources have become a very useful tool for surface modification and deposition of various materials. In this work, typical treatments of the surfaces of Mn, Fe, W and Cu metals were carried out using a low-pressure plasma system with argon gas and operating with an aluminum cathode. The plasma ignition was produced by flowing argon gas between two metal electrodes, and the maximum discharge voltage was 3 kV. All the treated metal samples were exposed to the plasma for a constant time of 2 hours. The modified metal surfaces were characterized by in situ X-ray florescence spectroscopy (XRF), contact angle measurements and scanning electron microscopy (SEM). The wetting behavior of the treated metal surfaces was studied by employing the contact angle method. The contact angle is found to be dependable on the surface layer properties of the metals which in turn is affected by the dose time.

Abstract: Passive Solid State Nuclear Track Detectors (SSNTDs) are a versatile tool for neutron studies as has been shown long ago and several good quality materials are commercially available. They are useful for charged particle detection in the linear energy transfer (LET) range above the threshold value of ~10 keV μm^-1. Linacs, operating above 6 MeV up to the energy region where radiotherapy is applied usually up to ~25MeV, induce unwanted photo-neutron field; their spectra shows two components due to reaction dynamics based on evaporation and knock-on mechanisms. Neutrons produced by Linacs are often neglected in health application; however, today it has become necessary to assess the effect on patient, staff and radiation workers. Radiation studies using SSNTDs play a major role in this case. Other fields also take advantage of the passive detectors properties; in fact they are employed with success to measure neutron signals relevant for plasma diagnostics as it was demonstrated at the RFX facility as part of the ITER project. The PADC-NTD techniques provide information on external neutron field values around the RFX-installation during pulsed operation. In any case, converter materials, as charged particles from (n, p) and (n, α) reactions, are required to produce neutron fingerprints through latent tracks. These once etched provide information on neutron fluence spatial values. Track histograms are then employed to determine photo-neutron induced damage in materials as well as radiation dose to both patient and professionally exposed workers. The estimated neutron fluence that can be determined by NTM covers a large range of values, the largest being above 10¹⁰ (± 12%) neutrons/cm².

Abstract: Passage of heavy ions produces radiation-damage trails known as latent tracks in a variety of solid-state nuclear-track detectors (SSNTDs). These tracks are made visible in an optical microscope by a simple process known as chemical etching. It is a well-known fact that latent tracks are radiation damage trails in SSNTDs, which can be annealed by thermal heating. Modgil-Virk formulation of single-activation-energy model of radiation damage annealing was proposed as an empirical approach for explaining the thermal fading of nuclear tracks in SSNTDs. The empirical formulation of this model is based on track annealing data collected from both isothermal and isochronal experiments performed on different types of SSNTDs using a variety of heavy ion beams and fission fragments. The main objective of this empirical model was to resolve some contradictions of variable activation energy derived by using Arrhenius plots to study annealing in mineral SSNTDs. Some equivalent versions of the Modgil-Virk model have been proposed but the concept of single activation energy is vindicated in all empirical formulations. The model always yields a unique value of activation energy independent of the nature of the ion beam used and the degree of annealing. The anisotropy of the mineral SSNTDs is revealed by variation in activation energy along different crystal planes and even with different orientations of the ion beam on the same plane. Some recent experiments are a pointer to the successful exploitation of this model for future cosmic-rays studies using SSNTDs.