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Preparation of ellipsoidal rod-shaped silica nanocomposite abrasives by Chromium ion/PEG200 induced method for sapphire substrates chemical mechanical polishing
摘要： Abrasive is vital to sapphire substrates chemical mechanical polishing and provides the most critical support for ?attening of sapphire. This work proposed a method to prepare ellipsoidal rod-shaped silica nanocomposite abrasives in order to increase the material removal rate and improve the surface roughness, which were applied to chemical mechanical polishing on sapphire substrates. Ellipsoidal rod-shaped silica nanocomposite abrasives were prepared by Chromium ion/PEG200 induced method. In this work, the synthesis process of ellipsoidal rod-shaped silica nanocomposite abrasives was discussed. As an inducing agent, Chromium compounds were bonded with two SiO2 particles via chemical bonds. And ellipsoidal rod-shaped silica nanocomposite abrasives were coated by PEG200 via hydrogen bonds. Results from X-ray photoelectron spectroscopy and time-of-?ight secondary ion mass spectroscopy revealed the occurrence of solid-state chemical reactions. The contact angle tests indicated the polishing liquid containing ellipsoidal rod-shaped silica nanocomposite abrasives had a good wettability. Ellipsoidal rod-shaped silica nanocomposite abrasives showed an excellent chemical mechanical polishing performance with a higher material removal and a lower surface roughness due to an excellent combination of chemical effect and mechanical effect occurred between ellipsoidal rod-shaped silica nanocomposite abrasives and sapphire substrates. A material removal model was built to describe the polishing behavior of ellipsoidal rod-shaped silica nanocomposite abrasives.
关键词： Polishing mechanism,Sapphire substrates,Ellipsoidal rod-shaped silica nanocomposite abrasives,Chemical mechanical polishing
更新于2025-11-14 15:27:09
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Orientation-Dependent THz Response of <i>m</i> -Plane Sapphire Substrate by Polarization-Sensitive THz Time Domain Spectroscopy
摘要： The dielectric response of m-plane sapphire (m-sapphire) substrates in the terahertz (THz) frequency is investigated using polarized-sensitive femto-second THz time-domain spectroscopy. We examined the transmitted THz time-domain waveforms with respect to the parallel-polarized THz field by rotating phi angle of m-sapphire substrates. The THz amplitude significantly decreased at the azimuth angle of 0°, 90°, and 180° with roughly equal amplitudes and no propagation time delay. The time delay of 480 fs in the THz pulse oscillations was observed between the azimuth angle of 45° and 90°, possibly due to the birefringence of nonpolar m-sapphire substrate. Strong THz field absorptions around ～1 THz frequency at azimuth angles of every 90° could be attributed to low-frequency phonon modes.
关键词： Sapphire,Birefringence,Time-Domain Spectroscopy,THz
更新于2025-09-23 15:23:52
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Study on mechanism of crack propagation of sapphire single crystals of four different orientations under impact load and static load
摘要： Sapphire has a wide range of applications due to its excellent physical properties. Sapphire is a typical anisotropic material, whose parts are usually employed in the complex conditions, including static and dynamic load. The mechanism of crack propagation under different loading conditions has important significance for successful application of sapphire. In this study, impact and static load tests have been performed on the A-plane, C-plane, M-plane and R-plane of sapphire by the high frequency cyclic impact test device, respectively. The force signals applied to sapphire have been obtained under different test conditions. The crack propagation has been analyzed based on the fracture morphology of specimen. It is found that sapphire will quickly crack and break under impact load, and then enter the fatigue stage. In the static load indentation tests, the force applied to sapphire seems to increase linearly with the linear increase of load, but this relationship is not yet linear in the unloading procedure. The crack propagation is affected by the crystal orientation, which leads to different characteristics of the surface morphology of the different crystal orientations sapphire after fracture. So four different models of crack system are proposed for A-plane, C-plane, M-plane and R-plane respectively. In addition, the three-dimensional morphology of sapphire is observed by a white-light interferometer. It seems that the Hertzian cone crack occurs only on the R-plane sapphire after impact load, but it cannot be sure whether the cone crack occurs when impacting A-, C-, and M-planes sapphire.
关键词： Impact load,Static load,Sapphire,Crystal orientations,Crack propagation,Crack system
更新于2025-09-23 15:23:52
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Purification and comprehensive utilization of sapphire kerf waste
摘要： Sapphire kerf waste (a fine powder) is a great potential source of high-purity α-Al2O3 and is currently discarded without reutilization, which is a waste of this resource and causes environmental problems, such as occupying space and generating dust. Herein, we report a feasible combined method to recycle valuable high-purity α-Al2O3 from sapphire kerf waste through the ultrasound-assisted leaching of nickel, diamond removal by bulk heating and a grinding process. The impurities in the waste were collected, and their existence states were characterized as independent metal nickel and diamond. The nickel impurity was removed from the waste by ultrasound-assisted leaching using a mixture of sulfuric acid and nitric acid, and the optimal leaching efficiency reached 99.67% under the conditions of sulfuric acid: nitric acid = 2:1 (v/v), 4 mol/L H+ concentration, 4 mL/g liquid-solid ratio, 45 °C, 30 min, 200 rpm, 240 W ultrasonic power and 45 kHz ultrasonic frequency. Subsequently, nickel ions in the lixivium were recycled in the form of nickel sulfate through extraction and stripping treatments. The diamond impurity was removed by bulk heating in flowing oxygen, and the optimal removal ratio was 99.65% under the conditions of 800 °C, 30 min and oxygen flow of 400 mL/min. High-purity α-Al2O3 was successfully recovered from the sapphire kerf waste after the grinding process, which had a purity higher than 99.99 wt% and an average diameter of 0.6 mm. In addition, the kinetics of leaching nickel and diamond removal were systematically analysed based on the shrinking model, and the chemical reaction was found to be the control step. The reaction mechanisms of the two processes were also studied. The economic evaluation revealed that the profit from dealing with 1 kg sapphire kerf waste with this method was $13.68. Therefore, the proposed method is promising for providing technical and economical guidance for industrial production.
关键词： Purification,Sapphire kerf waste,Carbon removal,Nickel leaching,Recycle
更新于2025-09-23 15:23:52
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Novel polyelectrolyte–Al2O3/SiO2 composite nanoabrasives for improved chemical mechanical polishing (CMP) of sapphire
摘要： A new type of polyelectrolyte–Al2O3/SiO2 composite nanoparticle with excellent dispersibility and superior polishing performance was successfully fabricated using a facile method. Silica acted as a bifunctional molecule by attaching to alumina via covalent bond and adsorbing polyelectrolytes by electrostatic interaction. The material removal rate of the polyelectrolyte–Al2O3/SiO2 abrasive was 30% higher than that of the pure Al2O3 abrasive. In addition, the sapphire surface was much smoother. The material removal mechanism was investigated during CMP using the microcontact and wear model. The enhanced removal rate was mainly attributed to the well-dispersed particles, which can accelerate mechanical removal process. The remarkably smooth surface was due to the decrease in penetration depth of the abrasive into the wafer. The results of this study provided a feasible strategy to satisfy the high efficiency and damage-free polishing requirements for sapphire planarization.
关键词： chemical mechanical polishing,composite abrasives,polyelectrolyte,surface roughness,sapphire,material removal rate
更新于2025-09-23 15:22:29
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The morphology evolution of selective area wet etched commercial patterned sapphire substrates
摘要： Patterned sapphire substrates (PSS) have been widely used to enhance the light output power of light emitting diodes (LEDs). The morphology and shape of the PSS have a great influence on the performance of the LEDs. In this work, commercial PSS is reprocessed utilizing selective-area wet etching approach, in which selective-area SiO2 mask is fabricated through partial exposure lithography instead of conventional overlay lithography. By precisely controlling the exposure time, the etching process can be controlled to take place only on the top of the PSS. Various surface morphology including pyramid, volcano, clover and closed-packaged inverted pyramid can be attained from the evolution of the selective-area etched PSS. The mechanism of the selective-area etched sapphire is correlated to the slant angle of the pattern surface and the SiO2 mask pattern.
关键词： Wet etching,Selective-area,Patterned sapphire substracte
更新于2025-09-23 15:22:29
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<i>β</i> -Ga <sub/>2</sub> O <sub/>3</sub> thin film grown on sapphire substrate by plasma-assisted molecular beam epitaxy
摘要： Monoclinic gallium oxide (Ga2O3) has been grown on (0001) sapphire (Al2O3) substrate by plasma-assisted molecular beam epitaxy (PA-MBE). The epitaxial relationship has been confirmed to be [010](ˉ201)β-Ga2O3||[1ˉ100](0001)Al2O3 via in-situ reflection high energy electron diffraction (RHEED) monitoring and ex-situ X-ray diffraction (XRD) measurement. Crystalline quality is improved and surface becomes flatter with increasing growth temperature, with a best full width at half maximum (FWHM) of XRD ω-rocking curve of (ˉ201) plane and root mean square (RMS) roughness of 0.68° and 2.04 nm for the sample grown at 730 °C, respectively. Room temperature cathodoluminescence measurement shows an emission at ~417 nm, which is most likely originated from recombination of donor–acceptor pair (DAP).
关键词： CL measurement,β-Ga2O3,sapphire substrate,PA-MBE,crystalline quality
更新于2025-09-23 15:22:29
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Numerical Analysis of Thermal Stress in Semi-Transparent Oxide Crystals Grown by Czochralski and EFG Methods
摘要： Crystal growth of oxides is generally difficult since large curvatures of the growth interface in these systems generate high thermal stress, dislocations and crystal cracking. Three-dimensional numerical modeling is applied to investigate thermal stress distribution in sapphire and langatate La3Ta0.5Ga5.5O14 (LGT) semi-transparent crystals grown by Czochralski (Cz) and Edge-defined Film-fed Growth (EFG) techniques. The analysis of thermal stress distribution in a sapphire ingot grown in a Czochralski furnace shows high von Mises stresses distributed almost symmetrically on large areas in the crystal. Thermal stress computations for piezoelectric langatate crystals grown in a Czochralski configuration show non-symmetrical von Mises distribution with higher stress on one side of the ingot. These numerical results are in agreement with experimental results showing non-symmetrical cracking at the outer surface of the crystal. 3D modeling of multi-die EFG growth of white sapphire ribbons shows that the von Mises stress is almost constant when the number of ribbons is increased from two to ten. Two models are applied to simulate the internal radiative heat transfer in the sapphire crystals: P1 approximation and the Rosseland radiation model. Numerical results show that applying Rosseland formula introduces significant errors in temperature field calculations especially in the case of the EFG configuration.
关键词： computer simulation,Czochralski,sapphire,single crystal growth,stresses
更新于2025-09-23 15:22:29
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Effect of crucible and crystal rotations on the solute distribution in large size sapphire crystals during Czochralski growth
摘要： In this study, the ?ow, temperature and solute concentration ?elds in the melt during the CZ growth process are numerically investigated. The results show that the magnitude and distribution of the solute concentration in the melt is strongly affected by the convective ?ow and thermal distribution. The maximum solute concentration always occurs at the crucible sidewall where the maximum temperature in the melt is found and the solute concentration at the crystal-melt interface increases from the triple point to the centerline. Heat transport from the side crucible wall towards the crystal-melt interface is enhanced by the crucible rotation. The level of the solute concentration inside the melt is reduced due to the lowering of the maximum temperature at the crucible wall. As a consequence, the distribution of the solute concentration along the crystal-melt interface becomes smaller and more uniform as the crucible rotation rate increases. However, after the crucible rotation rate becomes large enough, the maximum solute concentration and the solute concentration along the crystal-melt interface start to increase. Heat transport inside the melt is also affected by the crystal rotation. The centrifugal force induced by the crystal rotation generates a vortex below the crystal-melt interface. This vortex gets larger and stronger as the crystal rotation rate increases. In the smaller crystal rotation rate regime, this vortex is very small, suppressing the solute concentration at the crystal-melt interface. Therefore, the solute concentration along the crystal-melt interface becomes less when the crystal rotation rate is higher, although there is an increase in the maximum solute concentration in the melt due to the higher maximum temperature. In the higher crystal rotation rate regime, there is a reduction in the convexity of the crystal-melt interface due to enhancement of heat transport from the bottom wall of the crucible by vortex motion under the crystal-melt interface. Therefore, there is a switch to an increase in the transport of solute impurities into the crystal-melt interface. Hence, the solute concentration along the crystal-melt interface increases as the crystal rotation rate increases. However, with a further increase in the crystal rotation rate, as the shape of the crystal-melt interface changes becoming concave towards the melt, the solute concentration along the crystal-melt interface decreases because the maximum temperature is signi?cantly reduced. In this study, both counter- and iso-rotations are considered. The results of a comparison of the cases of iso- and counter-crystal rotation show that the lowest and most uniform solute distribution along the crystal-melt interface is achieved when there is no crystal rotation and the crucible rotation rate is ?xed at 1 rpm. In other words, the lowest and most uniform solute concentration can be achieved with the only crucible rotation.
关键词： Solute concentration,Czochralski method,Sapphire,Numerical simulation,Crucible and crystal rotations
更新于2025-09-23 15:21:21
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[IEEE 2018 31st International Vacuum Nanoelectronics Conference (IVNC) - Kyoto, Japan (2018.7.9-2018.7.13)] 2018 31st International Vacuum Nanoelectronics Conference (IVNC) - Depth profile of ZnAl<inf>2</inf> O<inf>4</inf> layer on sapphire substrate by cathodoluminescence
摘要： ZnAl2O4 for ultraviolet emitting phosphor prepared by deposition of ZnO on c-sapphire substrate and thermal diffusion process. The deflections of Zn and Al atoms in the films were confirmed by cathodo-luminescence properties. The CL intensity of ZnAl2O4 was not saturated from the film annealed for 100 hours, however, the saturation of UV emission was observed under anode voltage of 8 kV in the film annealed for 200 hours. It is thought that the thickness of ZnAl2O4 film became thinner by longer annealing at high temperature because of Zn re-evaporation. From cross-sectional FE-SEM observation, it was confirmed that the correct thickness and atomic distributions in the film. Since the ZnAl2O4 film thickness of the sample annealed for 100 hours was about 1 μm by FE-SEM, it was suitable the penetration depth of the electron into ZnAl2O4 layer
关键词： Sapphire substrate,Thermal distribution,ZnAl2O4,Ultra-Violet emission
更新于2025-09-23 15:21:21