Mechanical Properties of Aluminum Nitride Layer Formed by Duplex Coating of Barrel Nitriding and Plasma Nitriding

Abstract

Aluminum nitride layers on aluminum are formed by the barrel nitriding in nitrogen gas, and duplex coatings are performed with the plasma nitriding in nitrogen and argon gas after the barrel nitriding. Aluminum nitride films with high thickness, high surface hardness, and good adhesion can be obtained on aluminum surfaces by using the above process. Hardness and Young's modulus of the AlN formed by the barrel nitriding is estimated by means of the rules of mixture. The microstructure of the AlN is proved to be composed of Al and AlN. It is suggested that the AlN formed by the barrel nitriding can play a role as the adhesion improvement of the AlN formed by the plasma nitriding. Furthermore, a microindentation test, which can obtain indentation load–penetration displacement curves, is performed in order to investigate the film fracture of the AlN.

Formation of Aluminum Nitride Films by Gas Nitriding

“…Since the difference in the thermal expansion coefficient of AlN is about 5-6 times that of Al, the film was thought to be subjected to high compressive stress during furnace cooling and this resulted in delamination. Moreover, AlN films formed by plasma nitriding often exhibit large compressive stress; moreover, cracks or delamination also occur in these films 10) . The films formed by our process were composed of AlN, Mg, and Al 2 O 3 as shown in Figs.…”

Morphological features in aluminum nitride epilayers prepared by magnetron sputtering

“…The studies of AlN thin film could be divided into the investigations which emphasize chemical and physical properties (mechanical, electrical, magnetic) [6,9,17,21,22], analysis of the films structure [4,7,12,15,16,19,[23][24][25]32] and combined, showing the dependences of the properties on the films morphology [2,11,13,14,26,[33][34][35]. The structure of the thin films can utterly differ from the structure of bulk material and have different structural perfection.…”

“…It is characterized by interesting tribological [5] properties, high value of hardness and high thermal conductivity, moderate piezoelectricity, low dielectric and acoustic losses [6], high resistance to temperature and stability in corrosive medium [7], good heat dissipation [8], high dielectric constant, moderately high electromechanical coupling coefficient [9], low coefficient of thermal expansion [4], high elastic stiffness [2], non-toxicity [10], electrical reliability [11], light weight [12], high fusion temperature [13], high refractive index, transparence in visible light [14]. All these characteristics in combination with large optical band gap make AlN suitable for applications in high power and high frequency devices, surface acoustic wave filters, insulating [7], passivating, cladding layers [15] and optical devices (blue light emitting diodes, short wavelength lasers, ultraviolet light detectors [16], compact disks, laser diodes, phase shift lithography masks, AlN/GaN multilayer devices [17], for growth of GaN layers on Al 2 O 3 and on 6H-SiC, which are also of interest as perspective materials), electroluminescent applications over a wide wavelength range [18], acoustic-optic devices.…”

Surface Nitriding of Al-Mg Alloys Using a Rotary Barrel Tank

“…The formation of an aluminum nitride film on an aluminum surface is quite difficult because of a thin aluminum oxide film on the aluminum surface, which functions as a barrier against nitrogen diffusion into the aluminum surface. These two common methods require an argon sputtering process that takes many hours to remove the oxide film from the surface prior to nitriding 8,9) . In the aluminum nitriding process, nitriding is performed in conjunction with argon sputtering a means of cleaning the surface in order to prevent a reoxidation reaction.…”

“…The thickness of the film formed by ion nitriding is about 15 m, and the growth rate of the film is very slow. Films formed by these processes often exhibit poor adhesion to the substrate 9) . Therefore, a new nitriding process needs to be developed that can form a thick aluminum nitride film with good adhesion to the substrate within a relatively short time.…”