Transparent Wafer Research Articles

Transparent 0D Antimony Halides Glassy Wafer with Near‐Unity Photoluminescence Quantum Yield for High Spatial Resolution X‐Ray Imaging

AbstractLarge‐sized transparent scintillators with a high photoluminescent quantum yield (PLQY) and self‐absorption‐free properties are highly desired to achieve high spatial resolution X‐ray imaging. In this research, a transparent 0D organic–inorganic (ETP)2SbCl5 (ETP = Ethyl triphenylphosphine) amorphous wafer is developed by melting the ETPCl and SbCl3 mixture and then undergoing a quenching process. The obtained amorphous wafer exhibits a high light transmittance of 86% in the range of 450–800 nm. It also shows a light emission peak at 624 nm, a Stokes shift of 259 nm, and PLQY approaching unity (99.3%). These properties enable it to produce X‐ray images with a high spatial resolution of 19.0 lp mm−1 at a modulation transfer function (MTF) value of 0.2, among the best values reported. Additionally, it also shows remarkable stability under continuous X‐ray illumination. Its unique optical properties and ability to be processed in large sizes make the organic–inorganic metal halide transparent wafer a promising scintillator. This also demonstrates the potential application of the melt‐quenching method in fabricating highly luminescent, low‐electronic‐dimensional metal halide wafers.

Direct tape casting of Al2O3/AlN slurry for AlON transparent ceramic wafers via one-step reaction sintering

In this work, transparent aluminate oxynitride (AlON) ceramic wafers were successfully fabricated by the direct non-aqueous tape casting of Al2O3/AlN slurry and the one-step reaction sintering for the first time. The reaction sintered AlON ceramic wafer exhibits high transmittance of 73.2 % at the wavelength of 1600 nm. This fabricating route realizes smooth and flexible tape without cracks or pinholes in Al2O3/AlN system and efficiently shortens the preparation cycle of transparent AlON wafers, which is a feasible way to prepare high-quality transparent AlON ceramics with large lateral sizes and thin thicknesses by reaction sintering, might also promote the application of transparent AlON ceramic wafers.

Effect of Nitrogen Flow Rate on Microstructure and Optical Properties of Ta2O5 Coatings

Ta2O5 coatings were prepared on highly transparent quartz glass and silicon wafer substrates using RF magnetron sputtering technology. Different flow rates (10%, 15%, and 20%) of N2 were introduced during the sputtering process while keeping the total sputtering gas flow rate constant at 40 sccm. The effects of N2 flow rate on the phase structure, micro-morphology, elemental composition, and optical properties of Ta2O5 coatings were investigated. The coatings were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), atomic force microscopy (AFM), electron energy spectroscopy (EDS), and spectrophotometry. The results show that the phase composition of the coating is an amorphous structure when the sputtering gases are pure argon and nitrogen-argon mixed gases, respectively. The coating after the passage of N2 is mainly composed of Ta, N, and O, which confirms that the deposited coating is a composite coating of Ta oxide and nitride. The EDS spectrum indicates that the ratio of O to Ta atoms in the composite coating is greater than the stoichiometric value of 2.5. It may be related to the deposition rate of Ta atoms during the preparation process. The optical properties show that the average transmittance of the composite coating is greater than 75% and the maximum light transmission is 78.03%. The transmittance in the visible range of Ta2O5 coatings prepared under nitrogen-argon mixed gas sputtering conditions is greater than that of those prepared under pure argon sputtering conditions. Finally, the coatings optical direct band gap Edg and indirect band gap Eig are obtained.

Zero‐Dimensional Luminescent Metal Halide Hybrids Enabling Bulk Transparent Medium as Large‐Area X‐Ray Scintillators

AbstractScintillators are critical in medical imaging, non‐destructive security screening, and space exploration applications. However, it still remains a challenge to achieve large‐area and high‐transparency scintillators by a low‐cost and easy‐to‐implement way. Herein, a large transparent medium with a diameter over 10 cm is prepared via a facile melt‐quenching strategy using a stoichiometric mixture of ethyltriphenylphosphonium bromide (ETPBr) and MnBr2 as raw materials. Benefiting from the crystallization behavior of high‐efficiency green‐emitting (ETP)2MnBr4 nanocrystals hybridized with amorphous phase in the transparent wafer, the (ETP)2MnBr4‐based transparent medium as a scintillator evidences a high transparency (over 80%, ranging from 500 to 800 nm), a high light yield of ≈35 000 ± 2000 photon per MeV, a low detection limit of 103 nGy S–1, and a competitive spatial resolution of 13.4 lp mm–1 for X‐ray imaging. This work offers a distinctive simple and fast melt‐quenching methodology to fabricate (ETP)2MnBr4 metal halide X‐ray scintillator wafer with large‐area and shape flexibility, excellent transparency, and high scintillation performance for the medical or industrial X‐ray imaging application.

Wafer-Scale LSPR Substrate: Oblique Deposition of Gold on a Patterned Sapphire Substrate.

Label-free detection of biomolecules using localized surface plasmon resonance (LSPR) substrates is a highly attractive method for point-of-care (POC) testing. One of the remaining challenges to developing LSPR-based POC devices is to fabricate the LSPR substrates with large-scale, reproducible, and high-throughput. Herein, a fabrication strategy for wafer-scale LSPR substrates is demonstrated using reproducible, high-throughput techniques, such as nanoimprint lithography, wet-etching, and thin film deposition. A transparent sapphire wafer, on which SiO2-nanodot hard masks were formed via nanoimprint lithography, was anisotropically etched by a mixed solution of H2SO4 and H3PO4, resulting in a patterned sapphire substrate (PSS). An LSPR substrate was finally fabricated by oblique deposition of Au onto the PSS, which was then applied to label-free detection of the binding events of biomolecules. To the best of our knowledge, this paper is the first report on the application of the PSS used as an LSPR template by obliquely depositing a metal.

Large size growth of terbium doped BaCl2/NaCl/KCl eutectic for radiation imaging

In this study, a large-size eutectic scintillator of Tb-doped BaCl2/NaCl/KCl was grown using the Czochralski (Cz) and halide vertical Bridgman methods (H-VB). The suitability of these two growth methods for growing the eutectic was compared. Finally, 1 inch diameter eutectic bulks were obtained using the H-VB method. The Tb3+-derived strongest intensity peak at approximately 550 nm was observed by X-ray irradiation. An approximately 3 × 3 mm transparent eutectic wafer was cut and polished from the grown eutectic bulk. An imaging test using α-ray was performed using the grown eutectic, a fiber optic plate, and an electron-multiplying CCD camera. The resolution performance for radiation-imaging applications was evaluated.

Rapid fabrication of extremely thin Nano-Al2O3 transparent ceramic wafers through nonaqueous tape casting

Al2O3 transparent ceramics have important applications in electronics, solid-state lighting, military and 5G industries. At present, thin and large-size Al2O3 ceramics are urgently required by enterprises. Tape casting method has emerged as a powerful tool in producing transparent ceramics, but the preparation of the slurries is generally very time consuming. In this study, a one-step ball milling process was proposed to fabricate Al2O3 transparent ceramics through non-aqueous tape casting, in which green tapes were obtained with uniform texture and no distortion. Thickness of the Al2O3 transparent ceramics approached 0.1 mm. The effects of dry pressing on single and double-layer tapes were also compared. It was found that dry pressing has essentially no effect on monolayer samples, but contributed to improve the densification and promoted grain growth of the bilayer samples. Our results could be used as reference for the preparation of extremely thin Al2O3 transparent ceramic wafers.

Possible dimensionality transition behavior in localized plasmon resonances of confinement-controlled graphene devices

We investigated the dimensionality transition behavior of graphene localized plasmon resonances in confinement-controlled graphene devices. We first demonstrated a possibility of dimensionality transition, based on the devices carrier-density dependence, from a two-dimensional plasmon resonance to a one-dimensional plasmon one. We fabricated optical transparent devices and electrical transport devices on the same optical transparent wafer. These devices allow detailed control and analysis between carrier density and plasmon resonance peak positions. The carrier density from (two-dimensional) to constant (one-dimensional) is consistent with the theoretical predictions based on the Dirac Fermion carriers in linear-band structure materials.

Microwell Array Based Opto-Electrochemical Detections Revealing Co-Adaptation of Rheological Properties and Oxygen Metabolism in Budding Yeast.

Microdevices composed of microwell arrays integrating nanoelectrodes (OptoElecWell) are developed to achieve dual high-resolution optical and electrochemical detections on single Saccharomyces cerevisiae yeast cells. Each array consists of 1.6×105 microwells measuring 8µm in diameter and 5µm height, with a platinum nanoring electrode for in situ electrochemistry, all integrated on a transparent thin wafer for further high-resolution live-cell imaging. After optimizing the filling rate, 32% of cells are effectively trapped within microwells. This allows to analyse S. cerevisiae metabolism associated with basal respiration while simultaneously measuring optically other cellular parameters. In this study, the impact of glucose concentration on respiration and intracellular rheology is focused. It is found that while the oxygen uptake rate decreases with increasing glucose concentration, diffusion of tracer nanoparticles increases. The OptoElecWell-based respiration methodology provides similar results compared to the commercial gold-standard Seahorse XF analyzer, while using 20 times fewer biological samples, paving the way to achieve single cell metabolomics. In addition, it facilitates an optical route to monitor the contents within single cells. The proposed device, in combination with the dual detection analysis, opens up new avenues for measuring cellular metabolism, and relating it to cellular physiological indicators at single cell level.

Laser Processing of Transparent Wafers with a AlGaN/GaN Heterostructures and High-Electron Mobility Devices on a Backside.

Sapphire and silicon carbide substrates are used for growth of the III-N group heterostructures to obtain the electronic devices for high power and high frequency applications. Laser micromachining of deep channels in the frontside of the transparent wafers followed by mechanical cleavage along the ablated trench is a useful method for partitioning of such substrates after the development of the electronics on a backside. However, in some cases damage to the component performance occurs. Therefore, the influence of various parameters of the laser processing, such as fluence in the spot size, substrate thickness, orientation, and the polarization of focused laser beam, to the formation of damage zones at both sides of the transparent substrate with thin coatings when ablating the trenches from one side was investigated. The vicinity effect of the ablated trenches on the performance of the electronics was also evaluated, confirming the laser micromachining suitability for the dicing of transparent wafers with high accuracy and flexibility.

Metasurface-based subtractive color filter fabricated on a 12-inch glass wafer using a CMOS platform

Optical color filters are widely applied in many areas including display, imaging, sensing, holography, energy harvest, and measurement. Traditional dye-based color filters have drawbacks such as environmental hazards and instability under high temperature and ultraviolet radiation. With advances in nanotechnology, structural color filters, which are based on the interaction of light with designed nanostructures, are able to overcome the drawbacks. Also, it is possible to fabricate structural color filters using standard complementary metal-oxide-semiconductor (CMOS) fabrication facilities with low cost and high volume. In this work, metasurface-based subtractive color filters (SCFs) are demonstrated on 12-inch (300-mm) glass wafers using a CMOS-compatible fabrication process. In order to make the transmissive-type SCF on a transparent glass wafer, an in-house developed layer transfer process is used to solve the glass wafer handling issue in fabrication tools. Three different heights of embedded silicon nanopillars (110, 170, and 230 nm) are found to support magnetic dipole resonances. With pillar height and pitch variation, SCFs with different displayed colors are achieved. Based on the resonance wavelength, the displayed color of the metasurface is verified within the red-yellow-blue color wheel. The simulation and measurement results are compared and discussed. The work provides an alternative design for high efficiency color filters on a CMOS-compatible platform, and paves the way towards mass-producible large-area metasurfaces.

An Improved Efficiency by Surface Modification Using Pulse Laser for Partial Transparent Bifacial Solar Cell

Bifacial solar cell has symmetrical configuration contacts on front and rear surface that eliminate expansion mismatch, decrease metal usage and improves photon absorption. The limitation of the reflector at the back of bifacial solar panel able to be eliminated by developing special designed partially transparent bifacial solar cell to optimize light trapping on rear surface. Therefore, the partial transparent silicon (Si) wafers were developed to increase light transmission to rear surface. Surface modification on Si wafer was conducted to form partial transparent Si wafer. Surface modification was employed by pulsed laser interaction to create dot marking array on Si wafer. Two pulsed laser power applied were 25.5W and 39.6W to produce pattern, then immersed in 10% KOH solution to etch laser-induced structure and debris to form partial transparent Si wafer. Low power laser was induced 80-85 μm depth of micro-hole, while high power was induced 140-145 μm. KOH treatment was conducted to etch laser region which to form deeper and wide micro-holes. The bifacial solar cells have been fabricated using partial transparent Si wafer and the current-voltage of the devices were tested. The front surface efficiency obtained for both partial transparent bifacial solar cells were 4.36% and 5.59%, while rear surface achieved 1.23% and 1.16%. Fabricated conventional bifacial solar cell has an efficiency of 2.39% for front and 0.64% for rear. The surface modification enhanced the efficiency due to the photon path length transmission to rear surfaces, micro-hole’s dimension and optical absorption in the near-infrared region.

Blister‐Based Laser‐Induced Forward Transfer of Luminescent Diamond Nanoparticles

The possibility of laser printing of luminescent diamond nanoparticles via a blister‐based laser‐induced forward transfer technique is demonstrated. For this purpose, a donor substrate consisting of a transparent sapphire wafer and an absorbing thin titanium film (250 and 550 nm thick) coated with nanoparticles is exposed to the radiation of an ArF excimer laser (λ = 193 nm, τ = 20 ns). Under the optimized thickness of titanium layer and laser fluence, the ejection of nanoparticles from the donor substrate is caused by the blistering of the metal film without its rupture. The luminescence mapping of the donor and acceptor substrates has proved the transfer of luminescent diamond nanoparticles with the same intensity of the signal. Features and prospects of the proposed technique are discussed.

Light transmission and internal scattering in pulsed laser-etched partially-transparent silicon wafers

Continuing trend in silicon wafer thickness directed at cost reduction approaches basic boundaries created by: (a) mismatch between Al paste and Si wafer thermal expansion and (b) incomplete optical absorption. With its symmetrical front and back electrical contacts, the bifacial solar cell setup reduces stress due to mismatch thermal expansion, decreases metal use and increases high temperature efficiency. Efficiency improvement is accomplished in bifacial solar cells by capturing light from the back surface. Partially transparent wafers provide an option to improve near-infrared radiation absorption within Si wafer. To fully absorb optical radiation, three-dimensional texture of these kinds of wafers is essential. Pulsed laser interactions, thermal oxidation, and wet chemical etching are included in this research. A feature of its energy and pattern setup is the interaction of pulsed laser with Si, running at 1.064 μm wavelength and micro-second length. Two experimental settings were explored: (a) post-laser chemical etching with potassium hydro-oxide etching with thermal oxide as etching mask and (b) post-laser heat Si surface oxidation. Due to fast melting and recrystallization, laser pulsed processing inherently produces its own texture. Some of these spherically-shaped, randomly focused characteristics improve inner scattering and boost near-infrared absorption within the wafer. These characteristics are separated during chemical etching with the thermally-grown oxide layer as an etch mask. Comparison of optical absorption in both surfaces shows almost a rise in the magnitude of absorption in non-etched surfaces. Detailed optical (optical microscope and IR absorption), morphological (field emission scanning electron microscope) and heat imaging (far IR camera) analyses were performed to comprehend physical processes that contribute to near-IR absorption improvement. Such kinds of partially-transparent, three-dimensional textured Si wafers are anticipated to discover applications for bifacial solar cells as substrates.

Experimental investigation on the thermodynamic state of vapor plugs in pulsating heat pipes

In the present study, the thermodynamic state of vapor plugs in micro pulsating heat pipes (MPHPs) is experimentally investigated. The experiments are performed using the silicon-based MPHP with 10 turns. The rectangular micro-channels engraved on the silicon wafer form a closed loop and have the width and the depth of 1 mm and 0.5 mm, respectively. The overall dimensions of the MPHP are 50 × 33.5 × 1.7 mm3. Ethanol is used as the working fluid and the filling ratio is 47% on the average. A transparent glass wafer is bonded to the silicon wafer for flow visualization. The temporal variations in temperature and pressure of a vapor plug in the MPHP are obtained using micro-thermocouples and pressure transducers. The measured temperature and pressure data are fully synchronized in real time with the flow characteristics obtained through a high-speed photography. It is experimentally found that the thermodynamic state of a vapor plug in the MPHP depends on the presence of the liquid film surrounding the vapor plug. If a vapor plug is surrounded by the liquid film, the vapor plug is saturated and there is no temperature difference along the vapor plug. On the other hand, if a vapor plug is in direct contact with the dry wall without the liquid film, the vapor plug is superheated and there is a difference in the vapor temperature between the evaporator section and the adiabatic section. These results can pave the way to a thorough understanding of the thermo-hydrodynamic coupling in PHPs.

A Cost Effective Process for Large Area Photonic Array Applied in Light Emitting Diodes for Light Extraction Enhancement

The rise of the electricity-to-light conversion rate in light emitting diodes (LEDs) for energy saving has been constantly demanded. One of the keys to elevate the efficiency is to enhance the light extraction by using photonic structure covering on the window above the LEDs. This involves both designing and replicating the nanophotonic structures on transparent wafers. The techniques for micro-nano structuring should be high efficient and low cost for large volume production. This paper reports our recent progress in developing an industrialization prospective process for a planar photonic crystal in silicone to enhance the light extraction from LEDs in chip scale package (CSP) by template casting and film transfer. Characterizations of light extraction through the crystals and illumination from the LEDs demonstrate the significant improvement of the LED performance.

Experimental investigations of heat transfer mechanisms of a pulsating heat pipe

Experimental work was carried out to clarify the heat transfer mechanism of a pulsating heat pipe (PHP). A micro pulsating heat pipe (MPHP) with five turns was fabricated by engraving an interconnected micro-channel on a 1.1 mm thick transparent glass wafer. The engraved glass wafer and a 500 μm thick silicon wafer were anodically bonded to form a closed-loop MPHP. Ethanol was charged into the MPHP as the working fluid. The MPHP was vertically oriented with a bottom-heating mode. Using infrared (IR) thermometry, the distributions of temperature and heat flux were measured at the fluid-wall interface for the first time over the entire MPHP with high spatial and temporal resolution. High-speed flow visualization, which was synchronized to heat transfer measurements, was utilized to identify the local flow patterns corresponding to the local temperature and heat flux. The heat transfer at the fluid–silicon interface in the channels could be divided into the two parts: sensible heat transfer and latent heat transfer, and quantitative analysis of the data clarified the contributions of sensible/latent heat transfer to overall heat transfer. The overall contribution of latent heat transfer was estimated to be between 66% and 74%. Latent heat transfer not only induces the oscillating flow but also contributes significantly to overall heat transfer, whereas sensible heat transfer is a byproduct of the oscillating flow.

High luminous fluorescence generation using Ce:YAG transparent ceramic excited by blue laser diode

Solid-state laser lighting is an emerging technology, whereby high-brightness white light can be generated using blue laser diodes combined with a yellow-emitting phosphor. In this study, Ce:YAG transparent ceramic wafers with different cerium concentrations and thicknesses are prepared and their optical characteristics are measured. A transmission mode is used, wherein the phosphor ceramic is fixed onto an oxygen-free copper sink, whose temperature is accurately controlled, and excited using the blue laser diode. The recorded spectrum shows that blue laser light is completely converted to yellow light with a wavelength of 565 nm and width of 200 nm. Moreover, with varied temperatures of 10–80 °C, the luminous flux, spectrum, and color coordinates exhibit relatively stable. More importantly, the luminous flux is highest (2690 lm) when irradiated by a 19.5-W blue laser (with a center wavelength of 454 nm) for a Ce3+ dopant concentration of 0.5 mol% and a Ce:YAG thickness of 1.6 mm. Based on these results, the Ce:YAG transparent ceramic can be used as a potential phosphor material in applications of high-power solid-state laser lighting and laser display.

Textured dense zinc oxide layers for active noise canceling windows

AbstractDense ZnO films with a strong c‐axis texture have been deposited on transparent conductive oxide glass, glass, and Si wafers, respectively, with a two‐step pressureless wet chemical method using zinc acetate dihydrate as Zn‐precursor. The crystallographic structure of the films has been studied with XRD and scanning electron microscopy. Optical measurements reveal a high transparency of the ZnO films with a thickness of up to 10 μm. This new cost‐effective route for ZnO film deposition does not require expensive sophisticated equipment and is easily upscaled.

Distributed feedback ridge waveguide lasers fabricated by CNP process

In this work, cost efficient hybrid polymer based Bragg grating ridge waveguide resonators were successfully fabricated by a cost-effective combined nanoimprint and photolithography process. By using this hybrid process, optical features with the size in the scale of nanometers (Bragg gratings) and micrometers (waveguides) could be defined simultaneously in one step. The high quality mask-stamp for the CNP process was fabricated by the combination of electron-beam lithography, reactive ion etching and standard lift-off methods on a UV transparent glass wafer. For the following CNP process, the silicon-containing, inorganic-organic hybrid material OrmoCore® was used as the ridge-type waveguide core material due to its high chemical and physical stability as well as its low optical loss in the visible wavelength region. After depositing the active gain material (Alq3:DCM2) on top of the duplicated Bragg grating area, an optically pumped distributed feedback ridge waveguide laser source has been successfully fabricated. The full width at half maximum value of the laser was 180pm and the threshold for laser activity at 652.34nm was about 19μJ/cm2.