Improved electrical and optical properties of ITO/Ag/ITO films by using electron beam irradiation and their application to ultraviolet light-emitting diode as highly transparent p-type electrodes

We have investigated the effect of insertion of a Ag layer in ITO film as well as electron beam irradiation to the multilayer films on the electrical and optical properties of the ITO-based multilayer deposited by magnetron sputtering method at room temperature. Inserting a very thin Ag layer between ITO layers resulted in a significant decrease in sheet resistance and increased the optical band gap of the ITO/Ag/ITO multilayer to 4.35 eV, followed by a high transparency of approximately 80% at a wavelength of 375 nm. We have also fabricated ultraviolet light-emitting diodes (LED) by using the ITO/Ag/ITO p-type electrode with/without electron beam irradiation. The results show that the UV-LEDs having ITO/Ag/ITO p-electrode with electron beam irradiation produced 19% higher optical output power due to the low absorption of light in the p-type electrode.     

Effect of electron beam irradiation on structure and properties of SiCN thin films prepared by plasma assisted radio frequency magnetron sputtering

Silicon carbon nitride thin films were deposited on Si (100) substrate at room temperature by plasma assisted radio frequency magnetron sputtering. The bonding structure and properties of SiCN films irradiated by pulsed electron beams were studied by means of X-ray photoelectron spectroscopy and nano-indentation. The results showed that electron beam irradiation had a great effect on the structure and property of the films. Under sputtering gas pressure of 3.7 Pa, a transition from the (Si,C)N_x bonded structure to the (Si,C)₃N₄ bonded structure was found in the SiCN thin film with electron beam irradiation. At sputtering gas pressure of 6.5 Pa, the enhancement of hardness in the SiCN film after treatment with electron beam irradiation resulted from the promotion of the sp³-hybridization of carbons bonds.     

Influence of electron beam irradiation on nonlinear optical properties of Al doped ZnO thin films for optoelectronic device applications in the cw laser regime

We present the studies on third-order nonlinear optical properties of Al doped ZnO thin films irradiated with electron beam at different dose rate. Al doped ZnO thin films were deposited on a glass substrate by spray pyrolysis deposition technique. The thin films were irradiated using the 8 MeV electron beam from microtron ranging from 1  kG y to 5  kG y. Nonlinear optical studies were carried out by employing the single beam Z-scan technique to determine the sign and magnitude of absorptive and refractive nonlinearities of the irradiated thin films. Continuous wave He–Ne laser operating at 633 nm was used as source of excitation. The open aperture Z-scan measurements indicated the sample displays reverse saturable absorption (RSA) process. The negative sign of the nonlinear refractive index n₂ was noted from the closed aperture Z-scan measurements indicates, the films exhibit self-defocusing property due to thermal nonlinearity. The third-order nonlinear optical susceptibility χ(3) varies from 8.17 × 10⁻⁵ esu to 1.39 × 10⁻³ esu with increase in electron beam irradiation. The present study reveals that the irradiation of electron beam leads to significant changes in the third-order optical nonlinearity. Al doped ZnO displays good optical power handling capability with optical clamping of about ∼5 mW. The irradiation study endorses that the Al doped ZnO under investigation is a promising candidate photonic device applications such as all-optical power limiting.     

Effects of oxygen flow rate on microstructure and optical properties of aluminum oxide films deposited by electron beam evaporation technique

Reactive evaporation technique has been used to deposit thin films of alumina (Al₂O₃) on crystalline Si substrates at ambient temperatures in an electron beam (e-beam) evaporation system using alumina granules as evaporant material. The loss of oxygen due to dissociation of alumina has been compensated by bleeding high purity oxygen gas into the system during evaporation. A set of samples were prepared at different flow rates of oxygen and the films have been characterized by Spectroscopic Ellipsometry (SE), Atomic Force Microscopy (AFM), Grazing Incidence X-ray Reflectivity (GIXR) and X-ray Photoelectron Spectroscopy (XPS) measurements. The density and optical properties of the films showed interesting variation with oxygen flow rates.     

Thermal and optical properties of electron beam irradiated cellulose triacetate

Cellulose triacetate (CTA) is a polymer which is widely used in a variety of applications in the field of radiation dosimetry. In the present work, CTA samples were irradiated by electron beam in the dose range 10–200 kGy. The modifications in the electron irradiated CTA samples as a function of dose have been studied through different characterization techniques such as thermogravimetric analysis, differential thermal analysis and color-difference studies. The electron irradiation in the dose range 80–200 kGy led to a more compact structure of CTA polymer, which resulted in an improvement in its thermal stability with an increase in activation energy of thermal decomposition.

Also, the variation of melting temperatures with the electron dose has been determined using differential thermal analysis (DTA). The CTA polymer is characterized by the appearance of one endothermic peak due to melting. The results showed that the irradiation in the dose range 10–80 kGy causes defects generation that splits the crystals depressing the melting temperature, while at higher doses (80–200 kGy), the thickness of crystalline structures (lamellae) is increased, thus the melting temperature increased.

In addition, the transmission of these samples in the wavelength range 200–2500 nm, as well as any color changes, was studied. The color intensity ΔE^* was greatly increased with increasing the electron beam dose, and accompanied with a significant increase in the blue color component.     

Optical and electrical properties of TiOx thin films deposited by electron beam evaporation

The TiO_x thin films were prepared by electron beam evaporation using TiO as the starting material. The effect of the annealing temperature on the optical and electrical properties was investigated. The spectra of X-ray photoelectron spectroscopy reveal that Ti in the films mainly exist in the forms of Ti²⁺ and Ti³⁺ below 400 °C 24 h annealing. The charge transfer between different titanium ion contribute greatly to the color, absorption, and electrical resistance of the films.     

Effect of annealing on the electrical and optical properties of electron beam evaporated ZnO thin films

Zinc oxide thin films have been grown on (100)-oriented silicon substrate at a temperature of 100 °C by reactive e-beam evaporation. Structural, electrical and optical characteristics have been compared before and after annealing in air by measurements of X-ray diffraction, real and imaginary parts of the dielectric coefficient, refractive index and electrical resistivity. X-ray diffraction measurements have shown that ZnO films are highly c-axis-oriented with a full width at half maximum (FWMH) lower than 0.5°. The electrical resistivity increases from 10⁻² Ω cm to reach a value about 10⁹ Ω cm after annealing at 750 °C. The FWHM decreases after annealing treatment, which proves the crystal quality improvement. Ellipsometer measurements show the improvement of the refractive index and the real dielectric coefficient after annealing treatment at 750 °C of the ZnO films evaporated by electron beam. Atomic force microscopy shows that the surfaces of the electron beam evaporated ZnO are relatively smooth. Finally, a comparative study on structural and optical properties of the electron beam evaporated ZnO and the rf magnetron deposited one is discussed.     

Stability of Ag nanoparticles fabricated by electron beam lithography

The stability of silver nanoparticles on indium tin oxide coated glass substrates under atmospheric condition was investigated. These nanoparticles were fabricated using electron beam lithography. Energy dispersive spectroscopy analysis revealed a high concentration of sulfur in the silver nanoparticles exposed to laboratory air for 12 weeks at room temperature. Morphological changes in the silver nanoparticles were also observed for nanoparticles stored under the same conditions. In contrast, silver nanoparticles kept in vacuum did not show chemical or morphological changes after 12 weeks. The present work clearly shows the need to consider ambient exposure when using Ag nanoparticles for sensors.     

Structural and optical properties of electron beam evaporated CdSe thin films

Thin films of cadmium selenide (CdSe) as a semiconductor is well suited for opto-electronic applications such as photo detection or solar energy conversion, due to its optical and electrical properties, as well as its good chemical and mechanical stability. In order to explore the possibility of using this in optoelectronics, a preliminary and thorough study of optical and structural properties of the host material is an important step. Based on the above view, the structural and optical properties of CdSe films have been studied thoroughly in the present work. The host material, CdSe film, has been prepared by the physical vapour deposition method of electron beam evaporation (PVD: EBE) technique under a pressure of 5 × 10⁻⁵ mbar. The structural properties have been studied by XRD technique. The hexagonal structure with a preferred orientation along the (0 0 2) direction of films has been confirmed by the X-ray diffraction analysis. The films have been analysed for optical band gap and absorbed a direct intrinsic band gap of 1·92 eV.     

Characterization of ITO/CdO/glass thin films evaporated by electron beam technique

A thin buffer layer of cadmium oxide (CdO) was used to enhance the optical and electrical properties of indium tin oxide (ITO) films prepared by an electron-beam evaporation technique. The effects of the thickness and heat treatment of the CdO layer on the structural, optical and electrical properties of ITO films were carried out. It was found that the CdO layer with a thickness of 25 nm results in an optimum transmittance of 70% in the visible region and an optimum resistivity of 5.1×10⁻³ Ω cm at room temperature. The effect of heat treatment on the CdO buffer layer with a thickness of 25 nm was considered to improve the optoelectronic properties of the formed ITO films. With increasing annealing temperature, the crystallinity of ITO films seemed to improve, enhancing some physical properties, such as film transmittance and conductivity. ITO films deposited onto a CdO buffer layer heated at 450 °C showed a maximum transmittance of 91% in the visible and near-infrared regions of the spectrum associated with the highest optical energy gap of 3.61 eV and electrical resistivity of 4.45×10⁻⁴ Ω cm at room temperature. Other optical parameters, such as refractive index, extinction coefficient, dielectric constant, dispersion energy, single effective oscillator energy, packing density and free carrier concentration, were also studied.     

Characterization of ITO/CdO/glass thin films evaporated by electron beam technique

Abstract

A thin buffer layer of cadmium oxide (CdO) was used to enhance the optical and electrical properties of indium tin oxide (ITO) films prepared by an electron-beam evaporation technique. The effects of the thickness and heat treatment of the CdO layer on the structural, optical and electrical properties of ITO films were carried out. It was found that the CdO layer with a thickness of 25 nm results in an optimum transmittance of 70% in the visible region and an optimum resistivity of 5.1×10^?3 Ω cm at room temperature. The effect of heat treatment on the CdO buffer layer with a thickness of 25 nm was considered to improve the optoelectronic properties of the formed ITO films. With increasing annealing temperature, the crystallinity of ITO films seemed to improve, enhancing some physical properties, such as film transmittance and conductivity. ITO films deposited onto a CdO buffer layer heated at 450 °C showed a maximum transmittance of 91% in the visible and near-infrared regions of the spectrum associated with the highest optical energy gap of 3.61 eV and electrical resistivity of 4.45×10^?4 Ω cm at room temperature. Other optical parameters, such as refractive index, extinction coefficient, dielectric constant, dispersion energy, single effective oscillator energy, packing density and free carrier concentration, were also studied.     

Effect of substrate temperature on the electrical and optical properties of electron beam evaporated indium antimonide thin films

Thin films of non-stoichiometric indium antimonide (In_0.66Sb_0.34) have been deposited by electron beam evaporation technique on glass substrates at different substrate temperatures, (300?C473 K). The films have polycrystalline nature with zinc blende structure. The decrease in electrical resistivity with increasing temperature shows semiconducting behavior. Hall measurements indicate that the films are of n-type. Optical transmission spectra of as deposited thin films have been measured at different substrate temperatures. All the electrical parameters i.e. electron mobility (??), carrier concentration (n), resistivity (??), activation energy and band gap (E _g ) have been found to be temperature dependent. Suitable explanations are given in the paper.     

Effects of electron beam irradiation on tin dioxide gas sensors

In this paper, the effects of electron beam irradiation on the gas sensing performance of tin dioxide thin films toward H₂ are studied. The tin dioxide thin films were prepared by ultrasonic spray pyrolysis. The results show that the sensitivity increased after electron beam irradiation. The electron beam irradiation effects on tin dioxide thin films were simulated and the mechanism was discussed.     

Control of the electron beam active zone position in electron beam welding processes

It is known that charged particles emitted from the region of electron beam (EB) interaction with the material being processed, are an important source of information for the understanding of EB welding processes. Measurements for the three largest groups of charged particles, namely, backscattered electrons, true secondary electrons and ions are presented here. It was estimated that only the signals of the direct component amplitude of these particles’ currents, processed by neural networks, could be used to effectively control the EB welding process. Computer simulations of various models of neural networks are described. The best result was obtained for a network that determines an optimal value of focusing current for the weld being made, based on the amplitude of signals measured with a moderately defocused EB.     

Direct evidence for electron beam irradiation-induced phenomena in nanowired ZnO thin films

In-situ electron beam induced microstructural transformation experiments, leading to porosity in nanowires of ZnO, have been performed under a TEM operated at an electron accelerating voltage of 200 kV. For this purpose, nanowired (diameter: 20 to 80 nm) films of ZnO with thickness ~ 100 to 120 nm, were grown via metal-catalyst free-vapor phase mechanism. The evolved porosity (pore size about 2 to 20 nm) in nanowires, under electron beam irradiation, has been attributed to different bond-breaking phenomena at molecular Zn-O. Such nanoporous objects of ZnO are beneficial for various optical and sensing devices.     

Comparison study of microstructure, chemical composition and optical properties between resistive heating and electron beam evaporated LaF3 thin films

LaF₃ thin films were deposited by electron beam (EB) and resistive heating (RH) evaporation, respectively. Properties such as microstructure, chemical composition, surface morphology and optical constants of the LaF₃ thin films were characterized by measurements of X-ray diffraction, X-ray photoelectron spectroscopy, atomic force microscopy and spectrophotometer, then comparison was made between this two deposition methods. It's found that the microstructure properties of the LaF₃ films deposited by these two methods were different, and slight content of oxyfluoride films was formed during deposition according to the result of chemical composition analysis. The microstructure of LaF₃ bulk materials after interaction with electron beam and resistive heating was also characterized to analyze how the two deposition processes affect the formation of LaF₃ thin films and their microstructure properties. When it was for the laser resistance of the films, although the EB evaporated LaF₃ thin films occupied lower absorption and optical loss than those of the RH films, they showed slightly smaller laser induced damage thresholds at 355 nm, which was thought to be related to their much more rougher surface and higher tensile stress.     

Effect of interlayer addition on microstructure and mechanical properties of NiTi/stainless steel joint by electron beam welding

NiTi/Stainless Steel(SS) sheets have been welded via a vacuum electron beam welding process, with three methods(offsetting electron beam to SS side without interlayer, adding Ni interlayer and adding Fe Ni interlayer), to promote mechanical properties of the Ni Ti/SS joints. The joints with different interlayers are all fractured in the weld zone near the Ni Ti side, which is attributed to the enrichment of intermetallic compounds including Fe2 Ti and Ni3 Ti. The fracture mechanisms of different joints are strongly dependent on the types of interlayers, and the joints without interlayer, adding Ni interlayer and adding Fe Ni interlayer exhibit cleavage fracture, intergranular fracture and mixed fracture composed of cleavage and tearing ridge, respectively. Compared with the brittle laves phase Fe2 Ti, Ni3 Ti phase can exhibit certain plasticity, block the crack propagation and change the direction of crack propagation. The composite structure of Ni3 Ti and Fe2 Ti will be formed when the Fe Ni alloy is taken as the interlayer, which provides the joint excellent mechanical properties, with rupture strength of 343 MPa.     

Effect of high-energy electron beam irradiation on the properties of AZO thin films prepared by rf magnetron sputtering

We investigated that high-energy electron beam irradiation (HEEBI) performed in air at room temperature affected remarkably the properties of Al-doped ZnO (AZO) films grown on SiO₂ substrates by radio frequency magnetron sputtering techniques. Hall and photoluminescence measurements revealed that the n-type conductivity was preserved in HEEBI treated films with low dose up to 10¹⁵ electrons/cm² and converted to p-type conductivity with further increase in the amount of dose. X-ray photoelectron spectroscopy confirmed the conversion of conductivity by showing that in-diffusion of O₂ from the ambient as well as out-diffusion of Zn from the films took place as a result of HEEBI treatment at high dose of 10¹⁶ electrons/cm². X-ray diffraction analysis indicated that all as-grown films were found to have compressive stress, which was enhanced by HEEBI treatment with the increase of doses. It was also found that worse crystallinity with a smaller grain size was observed in HEEBI treated films with a higher dose, which was correlated with rougher surface morphologies of films observed by an atomic force microscope.     

Effect of isothermal deformation on microstructure and properties of electron beam welded joint of Ti2AlNb/TC11

Abstract

The present paper reports the influence of hot work (isothermal deformation accompanied with heat treatment) on microstructure and properties of electron beam welded dissimilar joint. Ti₂AlNb alloy and TC11 alloy were used to fabricate the joints. Isothermal deformation and heat treatment were performed under certain conditions. The structures were analysed using optical microscopy, X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The results show that the as welded metal of Ti₂AlNb/TC11 joint is mainly composed of α₂ and β phases. The metastable β phase transformed into α+β phases during deformation and heat treatment processes. There are no big differences in tensile strength of joints under different conditions. However, the impact toughness of the weld has improved 72% after hot work.