ABSTRACT
Facile approaches for creating thin-film scintillators with high spatial resolutions and variable shapes are required to broaden the applicability of high-resolution X-ray imaging. In this study, a transparent nano-polycrystalline ZnWO4 thin-film scintillator was fabricated by thermal evaporation for high-resolution X-ray imaging. The scintillator is composed of nano-sized grains smaller than the optical wavelength range to minimize optical scattering. The high transparency of the scintillators affords a sufficiently high spatial resolution to resolve the 2 µm line and space patterns when used in a high-resolution X-ray imaging system with an effective pixel size of 650 nm. The thermal evaporation method is a convenient approach for depositing thin and uniform films on complex substrates. ZnWO4 thin-film scintillators with various shapes, such as pixelated and curved, were fabricated via thermal evaporation. The results show that the transparent nano-polycrystalline ZnWO4 thin-film scintillator deposited through thermal evaporation has a potential for use in various high-resolution X-ray imaging applications.
ABSTRACT
A simple one-step approach to producing a distributed feedback (DFB) laser through selective irradiation of the gain medium, MEH-PPV, is presented. Electron irradiation alters the refractive index of MEH-PPV, thus, direct patterning by electron irradiation can be applied to create a periodic diffraction grating. The non-irradiated regions of MEH-PPV serve as the primary gain medium, while the irradiated regions of MEH-PPV provide the refractive index difference required to fabricate a DFB laser. This method was successfully applied to achieve lasing with a relatively low lasing threshold of 3â kW/cm2or 1.8 µJ/cm2 (pulse width: 600 ps). Furthermore, the lasing wavelength can be finely tuned by simply adjusting the grating period. In stark contrast to the simple one-step process described in this work, conventional procedures for the fabrication of DFB lasers involve multiple steps of varying complexity, including mold creation and careful coating of the substrate with the gain medium.
ABSTRACT
Nanocomposites comprising high-density polyethylene (HDPE) and boehmite (BA) nanoparticles were prepared by melt blending and subsequently irradiated with electrons. Electron irradiation of HDPE causes crosslinking and, in the presence of BA, generates ketone functional groups. The functional groups can then form hydrogen bonds with the hydroxyl groups on the surface of the BA. Additionally, if the BA is surface modified by vinyltrimethoxysilane (vBA), it can covalently bond with the HDPE by irradiation-induced radical grafting. The strong covalent bonds generated by electron beam irradiation allow the desirable properties of the nanofiller to be transferred to the rest of the nanocomposite. Since EB irradiation produces a great number of strong covalent bonds between vBA nanoparticles and HDPE, the modulus of elasticity, yield strength, and resistance to thermal shrinkage are enhanced by electron irradiation.
ABSTRACT
A facile route to producing non-stoichiometric silicon suboxide nanoparticles (SiOx NPs, 0 < x < 1) with an adjustable oxygen content is proposed. The process is based on electrochemical anodization involving the application of a strong electric field near the surface of a Si electrode to directly convert the Si electrode into SiOx NPs. The difference in ion mobility between oxygen species (O2- and OH-), formed during anodization, causes the production of non-stoichiometric SiOx on the surface of the Si while, simultaneously, fluoride ions in the electrolyte solution etch the formed SiOx layer, generating NPs under the intense electric field. The adjustment of the applied voltage and anodization temperature alters the oxygen content and the size of the SiOx NPs, respectively, allowing the characteristics of the NPs to be readily controlled. The proposed approach can be applied for mass production of SiOx NPs and is highly promising in the field of batteries and optoelectronics.
ABSTRACT
The effect of scintillator particle size on high-resolution X-ray imaging was studied using zinc tungstate (ZnWO4) particles. The ZnWO4 particles were fabricated through a solid-state reaction between zinc oxide and tungsten oxide at various temperatures, producing particles with average sizes of 176.4 nm, 626.7 nm, and 2.127 µm; the zinc oxide and tungsten oxide were created using anodization. The spatial resolutions of high-resolution X-ray images, obtained from utilizing the fabricated particles, were determined: particles with the average size of 176.4 nm produced the highest spatial resolution. The results demonstrate that high spatial resolution can be obtained from ZnWO4 nanoparticle scintillators that minimize optical diffusion by having a particle size that is smaller than the emission wavelength.
