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This study aims to present a numerical study of atomic structure for aluminium nitride (AlN) when the crystal was assumed grown on different orientation of sapphire substrate. The change of the AlN atomic structure with sapphire orientation was associated to the interface between the AlN and the sapphire. The results from this study would provide a guideline in selecting suitable orientation of sapphire for obtaining desirable AlN crystals, in particular, for reducing threading dislocation density in the AlN/sapphire templates for developing UV LEDs.

The approach of atomic structure by visualization for electronic and structural analysis numerical method to develop shape of atomic geometry to evaluate which plane are more suitable for the AlGaN technology UV-LED based.

The calculation based on ratio on first and second layers can be done by introduction of lattice constant.

With plane’s color of cutting plane on bulky materials, all the shape looks the same.

By implementing this method, the authors can save time to find the most suitable plane on the growth structure.

All authors of this research paper have directly participated in the planning, execution or analysis of the study; all authors of this paper have read and approved the final version submitted; the contents of this manuscript have not been copyrighted or published previously; the contents of this manuscript are not now under consideration for publication elsewhere; the contents of this manuscript will not be copyrighted, submitted or published elsewhere, whereas acceptance by the journal is under consideration.

Lapping is a vital flattening process to improve the quality of processed semiconductor wafers such as single-crystal sapphire wafers. This study aims to optimise the lapping process of the fixed-abrasive lapping plate of sapphire wafers with good overall performance [i.e. high material removal rate (MRR), small surface roughness (Ra) of the wafers after lapping and small lapping plate wear ratio (η)].

The influence of process parameters such as lapping time, abrasive size, abrasive concentration, lapping pressure and lapping speed on MRR, Ra and η of lapping-processed sapphire wafers was studied, and the results were combined with experimental data to establish a regression model. The multi-evaluation index optimisation problem was transformed into a single-index optimisation problem via an entropy method and the grey relational analysis (GRA) to comprehensively evaluate the performance of each parameter.

The results revealed that lapping time, abrasive size, abrasive concentration, lapping pressure and lapping speed had different influence degrees on MRR, Ra and η. Among these parameters, lapping time, lapping speed and abrasive size had the most significant effects on MRR, Ra and η, and the established regression equations predicted the response values of MRR, Ra and η to be 99.56%, 99.51% and 93.88% and the relative errors between the predicted and actual measured values were <12%, respectively. With increased lapping time, MRR, Ra and η gradually decreased. With increased abrasive size, MRR increased nearly linearly, whereas Ra and η initially decreased but subsequently increased. With an increase in abrasive concentration, MRR, Ra and η initially increased but subsequently decreased. With increased lapping pressure, MRR and η increased nearly linearly and continuously, whereas Ra decreased nearly linearly and continuously. With increased lapping speed, Ra initially decreased sharply but subsequently increased gradually, whereas η initially increased sharply but subsequently decreased gradually; however, the change in MRR was not significant. Comparing the optimised results obtained via the analysis of influence law, the parameters optimised via the entropy method and GRA were used to obtain sapphire wafers lapping with an MRR of 4.26 µm/min, Ra of 0.141 µm and η of 25.08, and the lapping effect was significantly improved.

Therefore, GRA can provide new ideas for ultra-precision processing and process optimisation of semiconductor materials such as sapphire wafers.

The wear of an abrasive single-crystal diamond (SCD) grit affects the machining quality of the sapphire wafer. This paper aims to investigate the influence of crystallographic orientation on the wear characteristics of SCD grit scratching on sapphire.

The wear characteristics of two SCD grits (SCD100 and SCD111) with different crystallographic orientations were systematically investigated. The wear mechanism involved in the scratching process was explored. The wear morphology, scratching forces and friction coefficient during the scratching process were measured and analyzed.

The experiment results show that the wear progress of the two SCD grits is obviously different. The wear resistance of SCD111 grit is greater than that of SCD100 grit in normal wear stage. However, the SCD100 grit could remove more sapphire material than SCD111 grit. The SCD grits mainly sustain extrusion stress and shear stress during scratching on sapphire. The crystallographic orientation of SCD grits plays a significant role in the wear progress during scratching on sapphire.

The results of the experimental studies could provide a theoretical foundation for improving the fabrication of abrasive diamond tools.

This paper explores four works of contemporary fiction to illuminate formal and informal regulation of sex. The paper’s co-authors frame analysis with the story of their creation of a transdisciplinary course, entitled “Regulating Sex: Historical and Cultural Encounters,” in which students mined literature for social critique, became immersed in the study of law and its limits, and developed increased sensitivity to power, its uses, and abuses. The paper demonstrates the value theoretically and pedagogically of third-wave feminisms, wild zones, and contact zones as analytic constructs and contends that including sex and sexualities in conversations transforms personal experience, education, society, and culture, including law.

The Fabry-Perot sapphire optical fiber sensor is an excellent choice for high-temperature sensing in civil and military fields, such as oil exploitation, engine and turbine. The purpose of this paper is to study the high-reflective film system withstanding high temperature in Fabry-Perot sapphire optical fiber high-temperature sensor. To improve the performance of the sensor and reduce the difficulty of signal acquisition, one of the key ways is to enhance the normalized light intensity of F-P sensor, which can be achieved by coating the high-reflective film system on the fiber end.

The high-reflective film system can be achieved by a multilayer film with alternating ZrO₂ and Al₂O₃ film layers whose refractive indexes are different. In addition, the optimum film alternating sequences and the influence of the number of film layers, incident angle and temperature should be obtained by numerical analysis.

With the increase of the number of film layers, the reflectivity rises gradually and the change trend is more and more gentle. A minimum of the spectral reflectivity will occur at a certain incident angle depending on the design of the periodic multilayer system. Temperature affects the reflectivity of high-reflective film system. The normalized light intensity of the F-P sensor coated with high-reflective film system enhances greatly which is helpful to the signal demodulation. The temperature response of the F-P sensor is mainly determined by the characteristics of the F-P cavity.

Higher reflectivity, lower cost and easy signal acquisition are the most important features of the introduced high-reflective film system for the Fabry-Perot sapphire optical fiber high-temperature sensor.

THE FRICTION developed in footstep type meter and instrument bearings have always presented a difficult problem to designers due to the mechanical severity, i.e., very high specific pressures, and the information given in this paper is the result of over thirty years of research on the problem carried out on behalf of the Electrical Research Association and also for the Northmet Laboratories.

This study aims to present the discrepancy in oil film distribution in reciprocating motion experimentally with zero entraining velocity (ZEV) on a conventional ball-disk test rig with oil lubrication.

Driven independently by two individual servomotors, a steel ball and a sapphire disc move at equal speed but in opposite directions in a triangle wave. The oil film images between the ball and the disc were recorded by a camera. After the experiments, the mid-section film thickness was evaluated by using a dichromatic interference intensity modulation approach.

The dimpled oil film in transient condition is shallower than that at steady state with the same load and velocities, and the transient dimple depth decreases with the decrease of time. The increase of the applied load offers a beneficial effect on lubrication. Boundary slippage happens in ZEV reciprocating motion. The slippage at the interface is related to the transient effect and applied load.

This study reveals the significant difference of the oil film variation in ZEV reciprocating motion, especially the complex boundary slippage at the interface of the oil and the sapphire disc.

The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-01-2020-0021

All measurements of EHD film thicknesses were carried out in simulated test machines. This study uses an actual bearing. A test rig which used a 65mm bore radial cylindrical roller bearing was constructed with a specially designed sapphire window in the outer track. Full loads, and speeds to 3000 rpm were applied. With specially polished rollers and chromic oxide coating on the window excellent interferometric film thickness measurements were found possible. A Xenon flash lamp was used and a Xenon Iaserof0–50pps,pulse half width of 150ns and peak power of 100 watts was developed for this research. A microscope and 35mm camera as well as video tape were used for recording results. Arrangements were made to study any chosen roller and the side of the bearing was also open to view. First the film measurements, when corrected for inlet zone viscous heating, agreed admirably with theoretical predictions for mid and exit film thickness. The effect of inlet boundary length on the film was then investigated in some depth. Studying the effect of the multiple roller system, a number of techniques were used to demonstrate that the inlet boundary length, which controls the lubricant film thickness, was itself controlled by the film thickness between the rollers and track in the unloaded zone. The ribs of oil, formed at either edge of the roller, are only secondary sources of oil for replenishment of the inlet film. It is in fact usual (as shown by the convex shape of the inletzone) for oil to feed out of the inlet zone into the ribs. Oil globules were sometimes observed riding on an air cushion at the entry to the roller‐track conjunction, though completely inoperative as providers of oil.

Rubicon Technology, a materials science company focused primarily on the manufacture and marketing of high quality single crystals possesses unique and advantageous technology. But having technological advantages is not enough. Concerted focus is required to translate that technical advantage into product performance that makes a significant difference in customer operations. With market intelligence, an honest self‐assessment and logical analysis, a sustainable market position was developed. The company avoided the temptation of chasing the market with the greatest upside potential and instead elected to target products and markets that were more accessible and aligned well with the experience and capabilities of the company’s technical and operations staffs. Recently, the company has invested enough (in manufacturing facilities and knowledge) to keep its future options open relative to additional vertical integration. Rubicon’s experience with strategic alliances confirms that they can play a crucial role in closing capability gaps and delivering a total package of value to key segments of the market. Rubicon has succeeded largely because, after selecting products and markets that offered excellent potential returns, it focused relentlessly on improving and aligning its technology and its operations to meet expressed customer and market needs. Rubicon has captured at least 10 percent of the LED/LD substrate market worldwide. More importantly, it has moved quickly from the high burn rate of a start‐up to breakeven, and it is on the road to profitability.

The purpose of this study is to investigate the influence of AlN nucleation thickness in reducing the threading dislocations density in AlN layer grown on sapphire substrate.

In this work, the effect of the nucleation thickness at 5 nm, 10 nm and 20 nm on reducing the dislocation density in the overgrown AlN layer by metal organic chemical vapor deposition was discussed. The AlN layer without the nucleation layer was also included in this study for comparison.

By inserting the 10 nm thick nucleation layer, the density of the dislocation in the AlN layer can be as low as 9.0 × 10⁸ cm⁻². The surface of the AlN layer with that nucleation layer was smoother than its counterparts.

This manuscript discussed the influence of nucleation thickness and its possible mechanism in reducing dislocations density in the AlN layer on sapphire. The authors believe that the finding will be of interest to the readers of this journal, in particular those who are working on the area of AlN.