Polyimide: From Radiation-Induced Degradation Stability to Flat, Flexible Devices

Polyimide (PI, PMDA-ODA, C22H11N2O5, Kapton-H), is a class of polymer, extensively used in microelectronics and space technology, due to its exceptional mechanical, dielectric, and chemical properties. In space, PI heat shield experiences a harsh environment of energetic electrons, ultra-violet radiation, and atomic oxygen, causing degradation and erosion. Radiation-assisted physicochemical surface modulations in PI, in view of understanding and reducing the degradation in laboratory-based systems, are discussed in the chapter. Strategies for the design and development of 2D, flat, and flexible electromechanical devices by swift heavy ion induced bulk modifications in PI are also described. Fabrication of a couple of such devices, including their performance analysis, is presented

Design of electron beam bending magnet system for electron and photon therapy: A simulation approach

The doubly achromatic electron beam bending magnet system using two sector magnets has been designed for the medical applications to treat the cancer. The aim of electron beam bending magnet system is to focus an electron beam having a spot size less than 3 mm × 3 mm, energy spread within 3% and divergence angle ≤ 3mrad at the target position. To achieve these parameters, the simulation has been carried out using Lorentz-3EM software. The beam spot, divergence angle and energy spread have been observed with respect to the variation in angles of sector magnets and drift distance. Based on the simulated results, it has been optimized that the first and second magnet has an angle 206° and 35° and the drift distance 80 mm. It is also observed that at the 1125, 1762, 2570, 3265 and 4155 Amp-turn, the optimized design produces 3369, 4972, 6384, 7584 and 9568 Gauss of magnetic field at median plane which require to bend 6, 9, 12, 15 and 18 MeV energy of electron, respectively, for the electron therapy application. The output beam parameters of the optimized design are energy spread ±3%, divergence angle ~3 mrad and spot size 2.6 mm. Moreover, for 6 MV and 15 MV photon therapy applications, an electron beam of energy 6.5 MeV and 15.5 MeV extracted from magnet system and focused on the bremsstrahlung target. Various materials have been studied for photon generation using Monte Carlo based Fluka code and Tungsten material has been optimized as bremsstrahlung target which produces continuous energy bremsstrahlung spectrum. For the photon therapy, the 1233 and 3327 amp-turn, in an optimized design produces 3616 and 7785 Gauss of magnetic field at median plane require to bend 6.5 and 15.5 MeV energy of electron, respectively, which further produces bremsstrahlung radiation from Tungsten target

Depth profiling of sodium and lithium doped samples using Rutherford backscattering spectrometry

650-652Various samples of Teflon chemically doped with lithium and sodium have been irradiated with hydrogen ions in order to study the depth profile using Rutherford backscattering (RBS) spectrometry which can detect even microgram of sample. Studies have also been done to see the effects of irradiation on the samples after and before doping them with sodium or lithium. Co-60 gamma-rays (1.17 and 1.33 MeV) and 1 MeV electrons have been used for irradiation

Detection of surface states in GaAs and InP by thermally stimulated exoelectron emission spectroscopy

The energy distribution and relative densities of electronically active surface defects have been studied using thermally stimulated exoelectron emission (TSEE) spectroscopy. This novel and relatively simple technique has high sensitivity for detecting the surface states which are difficult to assess by other techniques. Here this technique is successfully used for detecting the pinned positions of the Fermi level in n-GaAs and n-InP which are, respectively, 0.91 and 0.43 eV below the conduction bands corresponding to 2Eg/3 and Eg/3 as expected. Antisite and oxygen related defects in these semiconductors are also identified at the surface. The relative TSEE peak intensities correlate very closely to the reported surface recombination velocities for these materials which are two to three orders of magnitude higher for GaAs. The effect of chromium on the surface states in these semiconductors, studied using semi-insulating GaAs, showed partial passivation of the surface defects in semi-insulating GaAs resulting in unpinning of the Fermi levels. Fe doped InP did not, however, show any sign of dopant induced deep levels

Electron emissive properties of Pb and Bi containing glasses

Secondary electron emission (SEE) has been investigated for reduced Pb glass and bismuth containing V2O5-P2O5 and silicate glasses. The measurements of SEE coefficient, surface work function and ionization potential are reported. The systematic analysis of these results using Dionne's theory is given in view of their application in an electron multiplier. X-ray diffraction studies are also presented to confirm the metallic contents in these glasses

Design, development and characterization of tetrode type electron gun system for generation of low energy electrons

482-485A tetrode type electron gun system for the generation of low energy electrons has been designed, developed and characterized. The electron gun, designed for irradiation experiments, has four electrodes namely, cathode, focusing electrode, control electrode and anode. This electron gun is capable to provide electrons of energy over the range of 1 keV to 20 keV, with current maximum 100 μA. The electron gun and a Faraday cup are mounted in the evacuated cylindrical chamber. The samples are fixed on the Faraday cup mounted at a distance of 200 mm from the anode in the chamber and irradiated with low energy electrons at a pressure around 10<span style="font-family:Symbol; mso-ascii-font-family:" times="" new="" roman";mso-hansi-font-family:"times="" roman";="" mso-char-type:symbol;mso-symbol-font-family:symbol"="" lang="EN-GB">-6 mbar. In this electron gun system, at any electron energy over the entire range, the electron beam diameter can be varied from 5 to 120 mm on the Faraday cup. Also, the circular shape of the beam spot was maintained, even though the beam current and beam diameter are varied. The uniformity of the electron beam over the entire beam area was measured with a multi-electrode assembly and found to be 15%. This system is being used for the synthesis and diffusion of metal and semiconductor nanoparticles in polymeric and glass materials

Chemically modified teflon as an effective humidity sensor

Humidity-sensing characteristics of Teflon&#174; (PTFE) after etching its surface with sodium-naphthalene complex are reported. The change in impedance with relative humidity of the treated films is studied in various extremely dry gaseous atmospheres, viz. Ar, N2, H2 and O2 and also in the presence of moist air. It was observed that the electrical conduction of the films increases by four orders of magnitude as the relative humidity varied from 20% to 80%. The results were analysed using X-ray photoelectron spectroscopy and infra-red techniques. Possible models of the reaction and the chemical behaviour of the sample in humid conditions are discussed