Papers by Keyword: Sapphire

Abstract: Sapphire (Al₂O₃ crystal) is a hard and inert material with good mechanical, optical, physical and chemical properties that plays important roles in optics and electronics. The surface quality is the key element of sapphire components especially in optical field. This paper mainly introduces four methods of ultra-precision polishing, researches based on polishing theories and slurry. It can be a conclusion that traditional polishing methods can improve material removal rate assisted by ultrasonic.

Abstract: Single crystal sapphire is widely used as the material for precision equipments, due to its high hardness, chemical inertness and light transmission. However, it is difficult to obtain a scratch-free and damage-free sapphire surface with high-efficiency through traditional mechanical polishing or etching. We developed plasma assisted polishing (PAP) for the finishing of difficult-to-machine materials, such as silicon carbide, diamond, and sapphire. In this article, preliminary research results are showed about PAP applied to polishing of single crystal c-plane sapphire substrates. Combination of helium based atmospheric pressure water vapor plasma irradiation and silica abrasive polishing drastically increased removal rate of the sapphire c-plane. XPS measurements of the surfaces with and without irradiation of water vapor plasma revealed that alumina hydrate was formed by plasma irradiation at low temperature of less than 40°C. It is assumed that formation of alumina hydrate promoted the removal rate of sapphire.

Abstract: Sapphire/metal soldering joints are widely needed in various optical instruments. Traditional soldering methods are expensive and time consuming, because they usually involve a sapphire surface metallization procedure and a vacuum soldering procedure. In this study, we sealed infrared sapphire windows using a novel ultrasonic soldering method in the ambient atmosphere, with Sn-Zn-Al alloy as the solder. The wetting and bonding at the sapphire/solder and solder/metal-tube interfaces were realized by ultrasound. The microstructure of the joints was revealed by means of scanning electron microscope (SEM). The gas impermeability of the samples was investigated. This new method is very simple and cost-saving. The reliability of the samples made by this new method is equal to that made by traditional method. This is the first application of the ultrasonic interfacial deposition brazing and soldering (UIDBS) method to a practical device. We hope this method to be applied to other optical devices.

Abstract: Thin films of gallium nitride (GaN) and related nitride materials were prepared, and their properties as transparent conducting electrodes were investigated. GaN thin films were directly grown on sapphire single crystal substrates by the molecular beam epitaxy. Heavy doping of germanium was employed to reduce resistivity of the films, with sufficient reduction found to be possible while maintaining their epitaxial growth state. Optical transmission spectra of the films in the short wavelength region were slightly deteriorated by the heavy doping; however, this was successfully improved by growing GaN films under metal-rich conditions to increase the electron mobility and suppress unwanted increase of the carrier densities. In addition, the optical transmission spectra in the short wavelength region was improved also by alloying GaN with aluminum nitride, though the resistivities of these films were relatively higher than those of the unmodified GaN films. The prepared nitride thin films exhibited sufficiently suitable properties as transparent conducting electrodes for use in applications such as full-spectrum nitride-based solar cells.

Abstract: This study focuses on the process of the matte roughening technique of Sapphire. In order to effectively improve the shortcomings of conventional chemical etching, research adoptsthe micro abrasive jet machining technology with the experimental design method related experiments planned in order to effectively obtain the appropriate surface roughness and processing uniformity. Study found that # 800 Zirconium applied on the surface of sapphire with the initial surface roughness of about 0.9 μmRa for two minutes forms a surface roughness of about 1.1 μmRa. Not only does this conforms to the industrys sapphire surface specifications, it also effectively reduces the coarsening time and associated costs of sapphire.

Abstract: Sapphire, widely used in high-speed integrated-circuit chips, thin-film substrates, and various electronic components, is regarded as one of the most difficult to cut materials owing to its great hardness and low fracture toughness. Rotary ultrasonic machining (RUM) has been regarded as an effective processing method for hard and brittle materials. In this paper, RUM process is introduced into the drilling of sapphire for the first time. The feasibility to machine sapphire using RUM is studied. Moreover, results of a designed experimental study into RUM of sapphire are presented to discuss the main effects as well as interaction effects of process parameters (ultrasonic power, spindle speed, and feedrate) on outputs. The process outputs investigated include cutting force and edge chipping size.

Abstract: Grinding forces characteristics in elliptical ultrasonic assisted grinding (EUAG) of sapphire are investigated experimentally. The EUAG is a new grinding method proposed by the present authors in which an elliptical ultrasonic vibration is imposed on the workpiece by using an elliptical ultrasonic vibrator. In this paper, grinding experiments under the presence/absence of ultrasonic vibration assistance are performed. The effects of the vibration amplitude and grinding parameters such as the depth of cut, the grinding wheel speed on the grinding forces, grinding force ratio F_n/F_t are clarified. The obtained conclusions are as follows: the grinding forces during EUAG lowers to 50% and grinding forces ratio becomes reduced by 33% compared that during conventional grinding (CG); the grinding forces during EUAG have the less variation rate than those during CG as grinding parameters change; higher grinding wheel speed causes the larger grinding forces in CG, but has little effect on the variation of grinding forces in EUAG. By using EUAG method, the grinding forces and force ratio are greatly decreased, and surface quality is better, meaning that grindability of sapphire material is improved.

Abstract: The paper presents some aspects concerning use of pulse laser source for precise machining of Al₂O₃ crystals for medical applications. The scheme of laser beam manipulation and the test stand has been presented. Application of the mathematical model enabled determination of values of basic sapphire machining parameters. Presented results gave rough information about dynamics of the process and were used for the test stand designing, development as well as determination of machining precision.

Abstract: The dig rod process is the first step during the processing of sapphire. The Sapphire crystal lump cracks, the tool chipping and the low processing efficiency are the three common problems during the dig rod process. To solve these problems, developed the control system of the Sapphire dig rods machine based on the Z3050 rocker drill , applied fuzzy adaptive PID controller to detect the tool torque and adjust the tool feed rate real-timely, realized constant pressure closed-loop control, the experimental prototype successfully applied in the actual production. This paper introduces the composition, the principle of the system and its actual production.

Abstract: Solid phase growth of thin films of copper (Cu), aluminum (Al) and zinc oxide (ZnO) on single crystalline sapphire and quartz glass substrates were tried by heat-treatments and their crystallization conditions were investigated. ZnO thin films relatively easily recrystallized even when they were deposited on the amorphous quartz glass substrate. On the other hand, Cu and Al thin films hardly recrystallized when they were deposited on the quartz glass substrate. The metal thin films could be recrystallized at only extremely narrow windows of the heat-treatment conditions when they were deposited on the single crystalline sapphire substrate. The window of the solid phase heteroepitaxial growth condition of the Al film was wider than that of the Cu film.