Bias Effects On AlMgB Thin Films Prepared By Magnetron Sputtering

Considerable attention has been paid to a new kind of superhard materials, ternary AlMgB₁₄ composite, in recent years. With unique mechanical, thermal, and electrical properties, AlMgB₁₄ has been seen as a promising candidate material in protective coating of cutting tools and microelectromechanical components, In this paper, AlMgB thin films were deposited on Si ?100? substrates by a three target magnetron co-sputtering system. We explored effects of pulse negative bias voltage, duty cycle and DC superimposed pulse bias voltage on thickness, morphology, microstructure, mechanical property of AlMgB thin film in details.Amorphous AlMgB thin films were successfully prepared at different pulse negative bias voltages. The AlMgB thin films prepared at high negative bias voltage were found to be generally dense and containing more well-formed B12 icosahedra. These characteristics contribute to the hardness of the deposited films, which can reach 22.6 GPa and the corresponding elastic modulus is 240 GPa at the negative bias voltage of 400 V. These hard films have a roughness value of 0.89 nm, which is atomically smooth surface. However, the AlMgB thin films prepared at low negative bias voltages exhibit a loose microstructure, coarse surface, and contain few B12 icosahedra.Amorphous AlMgB thin films were prepared at different duty cycle. The surface morphology of AlMgB thin films was destructed leading to a large area of the thin films failing off from the substrates and the property becoming worse at duty cycle. The adhesion strength of the thin films decreases as well. In addition, AlMgB thin films contain less B12 with increasing the duty cycle, leading to the decrease of hardness and elastic modulus of AlMgB thin film.Amorphous AlMgB thin films were prepared at different superimposed pulse negative bias voltage. It is shown that the variation of the property of AlMgB thin films is not monotonous with the increase of superimposed pulse negative bias voltage. The deposition rate, hardness and elastic modulus of AlMgB thin films have a similar variation trend, i.e., increasing firstly until reaching a maximum, and then decreasing with the increase of superimposed pulse negative bias voltage. The variation of surface roughness has an opposite trend. With the values of DC voltage and superimposed pulse negative bias voltage set to be 50 and 300 V, the hardness and elastic modulus of deposited thin film reached 31 and 301 GPa, respectively. Simultaneously, the surface roughness reaches the lowest value of 0.8 nm. However, much higher superimposed pulse bias voltage can produce etching effect, which will make the quality of the AlMgB become worse.