Interplay Of Process Parameters Research Articles

The interplay of process parameters and influence on the AlN films on sapphire fabricated by DC magnetron sputtering and annealing

This paper reports a high-quality aluminium nitride (AlN) film deposited on c-plane sapphire using a direct current reactive sputtering system. A comprehensive investigation on the effects of substrate temperature, sputtering power, Ar/N2 flow ratio, and process pressure on the morphology and crystalline quality of the AlN thin films was performed. Optimal process parameters including substrate temperature of 500 °C, process pressure of 0.5 Pa, gas flow ratio of Ar/N2 = 1/6, and sputtering power of 400 W was demonstrated. In addition, the crystallization quality was further improved after face-to-face annealing and homoepitaxial regrowth by metal–organic chemical vapor deposition. The full widths at half maximum values of the x-ray rocking curves of the (0002) and () diffraction of AlN after the re-growth process reach as low as 49 and 360 arcsec, respectively, and the corresponding surface morphologies of the films were covered with atomic bi-layer steps. Finally, a ultraviolet-C light emitting diode with decent performance was demonstrated on top of the sputtered AlN thin film.

Absorber-free laser transmission welding of transparent polymers using fixed focus optics and 3D laser scanner

Laser transmission welding is a well-known joining technology for thermoplastics, providing reliable and hermetical sealing without adhesives or particle formation. The main advantages of laser-based energy input - high precision, no additional adhesive and no particle emission - are essential for medical and optical applications. To obtain sufficient absorption in visually transparent polymers, thulium fibre lasers emitting in the polymers’ intrinsic absorption spectrum are used. Optics with high numerical aperture provide large intensity gradients inside the specimen, enabling selective fusing in the joining zone. Although the basic feasibility has already been demonstrated, the welding process lacks stability and productivity.Aim of this work is the determination of optimized settings for a fast and reliable welding process. Thus, the interplay of process parameters as well as their impact on the seam are analysed by thermal simulations. Calculated settings are verified by welding tests with COC, PA6 and PETG, using a fixed-focus optics and a 3D laser scanner with up to 200 mm/s feed rate.