In-line Transmittance Research Articles

Unavoidable renaissance of electron metrology in the age of high numerical aperture extreme ultraviolet lithography

Things are drastically changing in the field of metrology. The main reason for that is related to the daunting specification requirements for metrology imposed by high numerical aperture extreme ultraviolet lithography (high NA EUVL). We observe a variety of generation e-beam tools proliferating in imec unique ecosystem, from in-line transmission electron microscope (TEM) to voltage contrast (VC) overlay tools, from die to database (D2DB) large area scanning electron microscope (SEM) to high-voltage SEM, from artificial intelligence (AI)-based inspection tools to massive data acquisition e-beam system. We are facing a renaissance of e-beam metrology. We are going to describe the challenges as well as the latest evolutionary developments of e-beam metrology in the semiconductor industry.

Impact of Sm ions on microstructure and magneto-optical effects of Y2O3 ceramics obtained by arc plasma melting

Faraday materials based on transparent ceramics are regarded for high power magneto-optical isolators. Pure yttria ceramics with high transmittance were prepared using the raw oxide powders. To enhance the magneto–optical performance of the ceramics, samarium oxide were introduced to yttrium oxide matrix as a paramagnetic ions. The Sm-Y2O3 Faraday ceramic was melted above 2700 °C for 10 min. It is noted that as-prepared ceramic presents the highest in-line transmittance above 61.0% at the high spectrum range of wavelengths from 350 to 1110 nm. Physicochemical properties of the sample were characterized by means of numerous techniques. No secondary phase was detected from the sample using X-ray diffraction. The Verdet constant of Sm-Y2O3 ceramic at 532 nm is as high as 20 rad/m*T, which is higher than that of pure Y2O3 ceramic. The good optical quality and magneto-optical properties make Sm-Y2O3 ceramic an attractive magneto-optical material.

Pressureless sintering of highly transparent aluminum oxynitride ceramic by precipitation-coating with sintering aid

AlON transparent ceramic is an ideal material for photoelectric windows, domes, and transparent armor. This ceramic is commonly fabricated by ball-mill mixing of AlON powder with appropriate sintering aids; however, it is difficult to homogeneously disperse trace sintering aids using this method and contamination is easily introduced, which may generate pores and flaws in the ceramic, resulting in degraded properties. To address this problem, we adopted a wet-chemical method to precipitation-coat sintering aids on the surface of AlON powder to achieve homogeneous distribution and enable nano-size sintering aids. Pressureless sintered AlON with 0.5 mass% Y2O3-coating gave in-line transmittance of 83.5% at a wavelength of 1064 nm and flexural strength of 326.3 MPa; the corresponding values for the ball-milled product were 79.3% and 304.6 MPa. Our results demonstrate that this method of sintering-aid coating has potential to fabricate AlON ceramic with excellent performance.

Mode manipulation in a ring–core fiber for OAM monitoring and conversion

Abstract The monitoring and conversion of photonic orbital angular momentum (OAM) play fundamental and important roles for both classic and quantum technologies, especially in low-loss transmission media such as ring-core fibers (RCFs), which make many OAM applications practical or vastly more flexible. However, in a RCF, the modes associated with different OAM states are highly overlapping due to the circular refractive index distribution structure, which makes it difficult to distinguish and monitor the OAM modes and in turn limits its inline conversion. Here, we report the first experimental realization of mode monitoring in a RCF using mode filters (MFs), which takes advantage of the difference in the mode adiabatic evolution and the higher-order mode cutoff conditions in tapered RCFs. Different-order OAM can be filtered using MFs with different geometric parameters, as demonstrated by the linearly polarized mode intensity. Combined the mode manipulations in RCF and single-mode fiber, the fundamental mode coupling efficiency can reach 90%, the RCF mode conversion monitoring through inline transmission spectrum evolution can be realized, and the inline fabrication of RCF grating, which couples one mode to a desired mode, can be demonstrated by the fabricating process of three long-period fiber gratings. The mode conversion efficiency between 0-order and 1, 2- or 3-order OAM modes exceeds 96%. Our work provides an efficient approach to monitor and convert OAM modes in higher-order mode supporting RCFs and even other special fibers and further promotes the improvement of the capacity of OAM transmission in RCFs.

Highly Transparent Polycrystalline MgO via Spark Plasma Sintering.

Optically transparent ceramics and MgO in particular are promising materials for a wide range of optical applications. This study introduces exceptionally highly transparent MgO ceramics produced via spark plasma sintering (SPS) at relatively low temperature and pressure by optimal incorporation of LiF as a sintering additive. The effect of LiF content on the microstructural and optical properties is presented with emphasis on its function as a densification aid and an agent for minimizing residual carbon contamination. Fully dense MgO discs, 20 mm in diameter and 2 mm thick, with ∼80% in-line transmission at 800 nm and >85% transmission in the infrared range (2-6 μm), are attained. These results demonstrate outstanding transparency in SPS polycrystalline MgO in the 800 nm range, only 7% below the theoretical value. In addition, this work strengthens our understanding of the LiF action mechanism during MgO sintering and its influence on texture development in the SPS-pressing direction. These findings pave the way for fabrication of large, fully dense samples with nearly theoretical transparency.

Fabrication and luminescence of highly transparent C12A7:Tb3+ glass-ceramics via in-situ crystallization from aerodynamic levitation processed glasses

Rare earth doped 12CaO·7Al2O3 (C12A7) glass-ceramics are one of attractive photonic materials due to their high transparency, high luminescent efficiency and eco-friendly nature. A series of C12A7 glasses with different Tb3+ doping concentrations was prepared by aerodynamic levitation method. The C12A7:Tb glass-ceramics were obtained via in-situ growth from the glasses with the identical chemical composition at 800 °C. The microstructure observation demonstrates that the elemental distributions of Ca and Al are homogeneous in the glass-ceramics and the grain size of C12A7 is 4–70 nm. The in-line transmittance of glass-ceramics reaches as high as 82% at 1500 nm. The emission spectra of the C12A7:Tb glass-ceramics present characteristic Tb3+ emission peaks at 486 nm (5D4→7F6), 541 nm (5D4→7F5), 585 nm (5D4→7F4) and 621 nm (5D4→7F3). The photoluminescence lifetime of C12A7:0.3%Tb glass-ceramic is 1.9 ms. Compared with the emission intensity of the glasses, that of the glass-ceramics increases due to the reducing in concentration of oxygen vacancy associated with network forming (NWF) cations. The highly transparent C12A7:Tb glass-ceramics may be a promising candidate for green light source in solid state lighting.

The hydrolysis process of γ-AlON powder and preparation of highly transparent ceramics with aqueous gel-casting

The untreated γ-AlON powders were proposed to prepare highly transparent γ-AlON ceramics by aqueous gel-casting technique and two-step sintering process. The related mechanism of hydrolysis of γ-AlON powders was discussed. The surface of the synthesized γ-AlON powders is covered with a layer of aluminum hydroxides compound. As the period of hydrolysis extends, the surface layer dissolved, and the boehmite and bayerite gradually formed, which is characterized by various techniques including XRD, FT-IR, XPS and TEM. The low viscosity slurry with high solids loading (53 vol%) was obtained by γ-AlON powders without any surface modification treatments as a result of the slow hydrolysis process. In addition, compared with the dry pressed sample, the sample (4.12 mm in thickness) prepared by aqueous gel-casting exhibits superior in-line transmittance of 81–83% in the visible region, which could be ascribed to the more homogenous and denser microstructure of the green body. Finally, the Weibull modulus and characteristic strength of γ-AlON transparent ceramic were determined to be 4.85 and 295 MPa, respectively.

Fabrication of 4 at.% La3+ ion doped (TbxLu0.96−x)2O3 transparent ceramics by using NC-PLSH technology and characterisation of their magneto-optical properties

Nanocrystalline powders and pressureless sintering (NC-PLSH) were used in a H2 atmosphere to fabricate 4 at.% La3+ doped (TbxLu0.96−x)2O3 magneto-optical transparent ceramics. La3+ was utilised as a sintering aid, and Lu3+ was used as a phase stabiliser. A component of the (TbxLu0.96−xLa0.04)2O3 magneto-optical material was designed and investigated based on powder sinterability and green compact sintering. Transparent (TbxLu0.96−xLa0.04)2O3 ceramics were obtained by using a one-step sintering process in H2 atmosphere, without the need for subsequent hot isostatic pressing. The in-line transmittance of the as-polished 4 at.% La3+:(Tb0.8Lu0.16)2O3 ceramic was 79% at 1400 nm. The measured Verdet constant at wavelengths of 633 nm and 1064 nm was 354 rad/(T·m) and 100.2 rad/(T·m), respectively. The required length of the (Tb0.8Lu0.16La0.04)2O3 ceramics was 63% less than that of Tb3Ga5O12 ceramics.

Fabrication of sub-micrometer sized Er:CaF2 transparent ceramics for eye-safe lasers

The 1 at.% Er:CaF2 transparent ceramics were prepared by the air pre-sintering and hot isostatic pressing (HIP) using nano-powders synthesized by the co-precipitation method. The influence of pre-sintering temperature and HIP post-treatment on the density, microstructures, optical and photoluminescence properties of Er:CaF2 ceramics were investigated. After HIP post-treatment (650 °C × 2 h, 100 MPa Ar), the pores in the pre-sintering ceramics were gradually eliminated and high transparency was achieved. The maximum in-line transmittance of the HIPed 1 at.% Er:CaF2 reaches 90.5% at 1600 nm (2.8 mm thickness) when the pre-sintered temperature is 625 °C.The absorption cross section was calculated. The strong absorption peak at 1530 nm reveals an unfavorable infrared emission. The main emission peak at 1530 nm, which is derived from the 4I13/2 → 4I15/2 transition of Er3+, can be observed under excitation of 980 nm. Owing to the long lifetime of 4I13/2 (32.3 ms) and large emission cross section, the 1 at.% Er:CaF2 transparent ceramics have great potential to achieve a good NIR laser performance in the 1.5 μm region.

Research on High-Frequency Current Partial Discharge Monitoring Technology of Transmission Lines

Partial discharge (PD) in transmission lines is one of the main causes of line breakdown. At present, PD monitoring is at the technical level and cannot be real-time and accurate monitoring. In this paper, a novel PD monitoring technology is designed by combining a high-frequency current sensor (HFCT) with traditional methods, which can not only accurately and quickly determine the leakage position, but also control the loss of inline transmission. In addition, based on the realization of partial discharge monitoring, this paper proposes a local signal denoising method, to distinguish between partial discharge monitoring of pure noise signal and local signal pulse discharge signal, and improve the efficiency and reliability of the monitoring equipment, the test results show that the sensor was carried out on the common discharge disfigurement detection, location, and recognition, and can be measured through the signal to assess the degree of danger.

High-entropy transparent (Y0.2La0.2Gd0.2Yb0.2Dy0.2)2Zr2O7 ceramics as novel phosphor materials with multi-wavelength excitation and emission properties

High-entropy ceramics have been extensively studied because of their novel intrinsic properties and have significant potential for application in various fields. In this study, a novel high-entropy transparent ceramic phosphor (Y0.2La0.2Gd0.2Yb0.2Dy0.2)2Zr2O7 was successfully prepared via a solid-state reaction and vacuum sintering. X-ray diffraction and scanning electron microscopy analyses were performed to analyze the phases and microstructures of the as-prepared powders and sintered ceramics. The highest in-line transmittance of the developed ceramic was 74 % in both visible and infrared regions. To reveal its luminescent properties as a potential WLED material, the photoluminescence of ceramic samples was analyzed using multi-excitation and emission spectra. Strong emissions originating from Dy3+ and Gd3+ were observed, and the emission color was effectively regulated under multi-wavelength excitation. Combining excellent optical transmittance with unique photoluminescence performance, the (Y0.2La0.2Gd0.2Yb0.2Dy0.2)2Zr2O7 high-entropy transparent ceramics can find potential applications as a novel WLED material with multi-wavelength excitation and tunable emission.

Mixed precipitants derived nanocrystalline powders and RE doped LuAG transparent ceramics

Lu3Al5O12 (LuAG) nanocrystalline powders were synthesized by using ammonium hydroxide (NH4OH, AH) and ammonium hydrogen carbonate (NH4HCO3, AHC) as mixed precipitant. In the absence of sintering aids such as TEOS, MgO or ZrO2, the obtained LuAG powders showed good sinterability in H2 atmosphere (PLSH) at low temperature. The in-line transmittance of LuAG ceramic reached 81% in the whole visible light band from 400 nm to 800 nm. The average grain size of obtained transparent ceramics was ranged in 1–6 μm at different sintering temperatures by PLSH. Various kinds of rare earth ions, such as Nd, Yb, Ce, Pr, and Tm doped RE:LuAG transparent ceramics could be prepared by PLSH technology without sintering aids and HIP post-treatment. Through PLSH technology, RE:LuAG transparent ceramics show high optical quality and large aperture size.

Investigation of up/down-converted luminescence and related mechanisms in Ho3+/Yb3+ co-doped Y2Zr2O7 highly transparent ceramics as phosphor material

Via solid state reaction, Ho3+/Yb3+ co-doped Y2Zr2O7 (YZO) transparent ceramics with different ytterbium concentration were successfully prepared. Highest in-line transmittance of samples reaches over 75% in both visible and near-infrared region. The homogeneity and microstructure of powders and ceramics were investigated through XRD and SEM characterizations. The luminescence results show that under excitation at ultraviolet (UV) and near-infrared (NIR) source, strong green emission peaks were observed and corresponding energy-conversion mechanism such as cooperative energy transfer (CET) were applied to explain the transition mechanism. Combined with the excellent optical properties and high temperature resistance, these results suggest that Ho3+/Yb3+ co-doped Y2Zr2O7 (YZO) transparent ceramics are promising novel phosphor material under different circumstance.

Effects of Nd3+ doping content on microstructure and spectral properties of Nd:SrF2 transparent ceramic

0.5–5 % (atom percent) Nd3+-doped SrF2 transparent ceramics were fabricated by hot-pressed sintering and the effects of Nd3+ doping content on microstructure and spectral properties were studied. With Nd3+ content increased from 0.5 % to 5 %, in-line transmittance of Nd:SrF2 ceramic at 1060 nm increased from 15.8 % to 85.3 %. FE-SEM micrographs showed the grain growth was inhibited and the microstructure became more compact and homogenous. Emission spectra revealed that concentration quenching was occurred at Nd3+ content of 1–2 %. Emission lifetime of 4F3/2 energy level monotonously decreased from 1805.4 μs to 19.6 μs. Evolution profiles of emission intensity and lifetime of Nd:SrF2 transparent ceramic with Nd3+ doping content were proposed. The appropriate Nd3+ content for spectral properties of Nd:SrF2 transparent ceramic was found around 1 %. The results demonstrated Nd:SrF2 transparent ceramic has large emission lifetime and mild concentration quenching effect, indicating that Nd3+-doped SrF2 transparent ceramics could be more promising gain media for all-solid-state lasers than other Nd3+-doped alkaline-earth fluorides.

Samarium doped yttrium zirconate transparent ceramics for highly transparent reddish-orange light emitting applications

Via solid state reaction, Sm3+ doped Y2Zr2O7 transparent ceramics with different samarium concentration were successfully prepared. Highest in-line transmittance of samples reaches over 75% both in visible and infrared region. The homogeneity and microstructure of powders and ceramics were investigated through XRD and SEM characterizations. The luminescence results show that under the excitation of ultraviolet (UV) and blue light source, strong red emission peaks were observed and corresponding energy-conversion mechanism were applied to explain the transition rules. Combined with the excellent optical properties and high temperature resistance, these results suggest that Sm3+ doped Y2Zr2O7 (YZO) transparent ceramics are promising novel red LED material for application such as illumination, digital display, etc.

Preparation of multicomponent A2Zr2O7 transparent ceramics by vacuum sintering

Recently, high-entropy oxide ceramics have become a hot topic in the field of high entropy materials. In this paper, multicomponent pyrochlore A2Zr2O7 transparent ceramics were prepared via vacuum sintering using combustion synthesized nanopowders. The phase analysis results indicate that the powders exhibit defective fluorite structure and the ceramics are in pyrochlore structure. The structural order degree of ceramics varies with the increase of incorporated components. It is found that the grain size of A2Zr2O7 ceramics is related with the component of A-site. The main fracture mode of final ceramics exhibit typical transgranular fracture. The multicomponent A2Zr2O7 ceramics exhibit excellent optical transmittance, and the highest in-line transmittance reaches to 80% for #A2ZO ceramic at 1880 nm.

Effect of solid loading on properties of Y2O3–Al2O3–Nd2O3 powder mixtures obtained by planetary ball milling and ceramics based on them

The effect of the solid loading (41–50 wt%) of the slurry on granulometric composition and physico-chemical characteristics of Y2O3–Al2O3–Nd2O3 powder mixtures obtained by planetary ball milling has been studied for the first time. It was shown that the particle size distribution of powder, its Zeta potential, and specific surface area depend on the solid loading of the milled slurry and, consequently, on the interparticle distance during milling. The interparticle distance decreases from 200 nm to 142 nm with an increase of solid loading in the range of 41–50 wt%. It was shown that for the solid loading of 47 wt%, the convergence of particles to a distance comparable to their median diameter promotes subsequent clustering of particles. This facilitates the sintering of highly-homogenous ceramics. It was found that solid loadings in the 46–50 wt% range is useful for obtaining high-quality Nd:YAG transparent ceramics. The lowest optical losses optical losses of 1 × 10−3 cm−1 and the highest in-line transmittance of 84.1%@1064 nm were obtained for 1 at.% Nd:YAG transparent ceramics (22 × 3 × 4 mm3) prepared from slurries with 47 wt% solid loading (taking all other ball milling parameters fixed). If the interparticle distance in the powder is higher (solid loading of 41 wt%) than the median particle diameter, the ceramics are characterized by significant residual porosity due to the survival of large particles (insufficient milling).

Fabrication of Highly Transparent Y2O3 Ceramics via Colloidal Processing Using ZrO2-Coated Y2O3 Nanoparticles

An easy approach is described for the preparation of ZrO2-coated Y2O3 nanopowder from a solution of zirconium nitrate with commercial Y2O3 nanopowder. The evolution process of the ZrO2 coating layer upon calcination, such as the phase and microstructure of the particles’ surface, was studied. Calcination of the powder at 700 °C resulted in ZrO2-coated Y2O3 nanopowder. The rheological properties of the suspensions of ZrO2-coated Y2O3 powders were studied. A well-dispersed suspension with a solid loading of 35.0 vol% using ZrO2-coated Y2O3 nanopowder was obtained. The consolidated green body obtained by the centrifugal casting method showed improved homogeneity with a relative density of 50.2%. Transparent ceramic with high transparency and an average grain size of 1.7 µm was obtained by presintering at 1500 °C for 16 h in air, followed by post-HIP at 1550 °C for 2 h under 200 MPa pressure. The in-line transmittance at the wavelength of 1100 nm (1.0 mm thick) reached 81.4%, close to the theoretical transmittance of Y2O3 crystal.

Transparent high-strength nanosized yttria stabilized zirconia obtained by pressure-less sintering

This work describes the development of transparent high-strength Yttria-Stabilized Zirconia (YSZ) ceramics with ultra-fine grain size utilizing conventional pressure-less densification. Starting with nanoparticles with diameter < 10 nm, it was possible to achieve full densification (>99.5% of theoretical density) at a sintering temperature of 1100–1200 °C. The average grain size of the resulting dense ceramics was 75 nm in 3 mol. % YSZ and 85 nm in 8 mol. % YSZ, showing in-line light transmission of 38% and 51% at a wavelength of 800 nm and average biaxial strength (piston on three balls test on samples of diameter 12 mm and thickness 1 mm) of 1980 MPa and 680 MPa, respectively. The nano-grained structure, absence of color centers, and miniaturization of residual pores enable the excellent light transmission. The high biaxial strength is attributed to the refined microstructure, but also to the martensitic tetragonal-to-monoclinic phase transformation that remains active even in nano-sized zirconia grains.

Terbium (III) Oxide (Tb2O3) Transparent Ceramics by Two-Step Sintering from Precipitated Powder

As a result of preliminary air calcination and subsequent reduction in a flowing NH3 atmosphere of the precursor from the liquid precipitation method for the first time, pure-phase Tb2O3 powder with an average particle size of 135 nm was prepared. The Tb2O3 magneto-optical transparent ceramics with the average grain size of 1.3 μm were successfully fabricated by vacuum pre-sintering and hot isostatic pressing post-treatment from the as-synthesized Tb2O3 powder. In-line transmittance values of Tb2O3 ceramics reach 70.3% at 633 nm, 78.1% at 1064 nm, and 79.4% at 1400 nm, respectively. Thanks to the high intrinsic concentration of Tb3+, Tb2O3 ceramics present high Verdet constants of −427.3 and −123.7 rad·T−1·m−1 at 633 and 1064 nm, which are about 3.1 and 3.4 times higher than those of commercial Tb3Ga5O12 crystals, respectively. Due to the excellent magneto-optical properties, Tb2O3 ceramics are promising candidates for the development of Faraday isolator toward compaction used in visible and near-infrared bands.