Study On Properties Of Al-Mg-B Thin Films Prepared By Magnetron Sputtering

Aluminum magnesium boride (AlMgB14) is one of the promising hard materials, which is of great interest due to its extreme hardness, low density, high thermal stability, and desitable thermoelectric properties. These properties were significantly affected by elemental composition, surface morphology, bonding states in Al-Mg-B thin films. Therefore, it is important to study surface morphology and structural properties in the aluminum magnesium boron (Al-Mg-B) films deposited via different experimental parameters and doped.Al-Mg-B thin films were deposited by magnetron sputtering. We carefully investigated the effects of substrate temperature, boron sputtering power, target composition, bias and doped on element content, bonding states, surface morphology and mechanical properties.Films were investigated by EPMA, AFM, XRD, nanoindentation. The main contents are given below:(1) Al-Mg-B thin films were successfully prepared by magnetron sputtering with different boron sputtering power and substrate temperature. The analyses results indicate that the hardness of Al-Mg-B thin films become higher with the increase of the B content, which can be influenced with the substrate temperature and the sputtering power of the B-cathode. The maximum hardness of the Al-Mg-B thin films of～31 GPa is obtained for the film with-65 at.% B. The Al-Mg-B thin films showed a smooth surface. The surface of the films becomes smoother with increasing the boron sputtering power and the substrate temperature. The best RMS roughness attained is about 0.5 nm for the film which shows also the highest hardness. The deposition temperature and the boron sputtering power play important roles, as they sharply influence the B content, in the process of depositing Al-Mg-B thin films.(2) Al-Mg-B thin films were deposited by radio frequency magnetron sputtering from different rates of AlMg sputtering target in the atmosphere of argon (Ar). It is found that elemental content of Al-Mg-B thin films were very close to that of AlMgB14. The structure of these films was amorphous and had a very smooth surface. When the rate of Al/Mg in AlMg sputtering target is about 1:1, Al-Mg-B thin films had much smoother surface, higher hardness and lower friction coefficient. Therefore, the influences of the rates of AlMg sputtering target on properties of Al-Mg-B thin films are very important. (3) We investigated the influence of bias voltage on the bond contents, compositions and mechanical properties of Al-Mg-B films prepared using radio frequency magnetron sputtering technique at 600℃. The results showed that the chemical compositions of thin films were uniform in the surface region and show similar values under different bias voltage. Optimizing bias may be helpful for the growth of B12 icosahedra in films. That may be result in the increase of the hardness of films. The maximum hardness of the Al-Mg-B thin films of 30.7 GPa is obtained for the film with 50 V bias.(4) Al-Mg-B thin films with different doped were prepared on Si (100) substrates with a two target magnetron sputtering system. The dopant were chromium, titanium and nitrogen, respectively. The results indicate that Cr, Ti and N elements by electron microprobe analysis are all present in the films, respectively. Doping Cr may inhibit the growth of B12 icosahedra in films, which due to the hardness decrese; the hardness of N-doped Al-Mg-B thin films was only 2 GPa, which was attributed to sp2 B-N bond in films; Ti-doped Al-Mg-B thin films had low hardnss with 9 GPa. It may be probably due to B-O bond in thin films. To summarize, it is obvious that Al-Mg-B thin films with different dopants show different properties, which would lay a good foundation for further research of Al-Mg-B thin films.