Influence of Vacuum Chamber Pressure on Microstructure and Properties of Tungsten Target Fabricated by Low Pressure Plasma Spraying

Abstract

Planar and rotary tungsten targets were fabricated by low pressure plasma spraying (LPPS). The effects of chamber pressure on the relative density, oxygen content by mass, microstructure, micro-hardness and ultimate tensile strength(UTS) of tungsten targets were analyzed. In addition, the magnetron sputtering experiment of LPPS tungsten target was studied. As chamber pressure increased from 1.3×104Pa to 3.9×104Pa, tungsten powders were full melted and spread with decreased unmelted particles existing in the target, the oxygen content in the tungsten target slightly improved. At the same time, relative density, micro-hardness, and UTS of LPPS tungsten target increased up to maximum values as 97.2%, 377.8HV0.025 and 201.1MPa, respectively. However, oxygen content of tungsten targets increased significantly up to 0.71% with floc like W3O layer(about 200nm thickness) being formed at lamellar bonding interface as chamber pressure further increasing up to 6.5×104Pa. Instead, relative density, micro-hardness and UTS of tungsten target decrease for detrimental effect of oxygen content. Smooth, dense and continuous tungsten thin film with the thickness of about 300nm can be deposited by magnetron sputtering from LPPS tungsten target under chamber pressure of 3.9×104Pa. XRD spectra show that the tungsten thin film in body centered cubic structure grows preferentially along (110) direction. The uniform bombardment of sputter ion results in rapid sputtering and uniform reduction on the surface of tungsten targets during magnetron sputtering. The sputtering surface and cross section are even and smooth with the nano-scale sputtering spits being formed.

Keywords

• low pressure plasma spray
• tungsten target
• microstructure
• mechanical property
• magnetron sputtering