【作者】 吴占玲；

【导师】 白亦真；

【作者基本信息】 大连理工大学 ， 凝聚态物理， 2011， 硕士

【摘要】 铝镁硼(AlMgB14)作为一种新型超硬纳米材料,以其优异的机械、热学和电学性能有着广泛的应用前景。铝镁硼(Al-Mg-B)薄膜的元素成分、表面形貌、内部结构等对其机械、热学和电学性能的影响十分明显。因此研究沉积参数和掺杂对Al-Mg-B薄膜的内部结构和表面特性的影响有重要的意义。本文采用磁控溅射的方法制备了Al-Mg-B薄膜。研究了基片温度、硼溅射功率、靶材组成、偏压及其掺杂对Al-Mg-B薄膜的元素含量、成键性质、表面形貌及其力学性能的影响。采用电子探针显微分析(EPMA)、原子力显微镜(AFM)、X射线衍射(XRD)、傅立叶红外光谱(FTIR)、纳米压痕等对薄膜进行了表征。工作主要内容如下：(1)在不同的沉积温度和硼溅射功率下,采用磁控溅射法成功制备了Al-Mg-B薄膜。结果表明,由于受到基片温度和硼溅射功率的影响,Al-Mg-B薄膜的硬度随着B含量的升高而增加。Al-Mg-B薄膜的最大硬度约为31 GPa,其硼含量为65 at.%。Al-Mg-B薄膜的表面很光滑。随着基片温度和硼溅射功率的增加,薄膜的表面粗糙度变小。最好的表面粗糙度达到约0.5 nm,摩擦系数可达到0.05,同时这个薄膜的硬度也最高。在沉积Al-Mg-B薄膜过程中,沉积温度和硼溅射功率扮演重要的角色,因为它们大大影响了薄膜中硼的含量。(2)采用磁控溅射方法,改变AlMg复合靶的比率,成功制备出Al-Mg-B薄膜。结果表明,非晶薄膜的成分接近于AlMgB14晶体的原子含量,表面非常平滑。通过改变AlMg复合靶的比率在一定程度上对Al-Mg-B薄膜的性能有所改善：当AlMg复合靶的Al:Mg比值接近于1时,制备的薄膜具有更高的硬度,表面更平滑,摩擦系数最低。因此AlMg复合靶对制备不同性能的Al-Mg-B薄膜有重要影响。(3)在不同的偏压下,利用高真空的磁控溅射设备在Si(100)上制备Al-Mg-B薄膜。结果表明,在600℃下沉积的薄膜成分是均匀的,并且改变偏压对薄膜化学组成基本没有影响；适当地偏压有助于Al-Mg-B薄膜中B12二十面体的形成,从而导致薄膜的硬度的升高,最高可达到30.7 GPa。(4)分别以铬、钛、氮为掺杂物,通过磁控溅射法采用两靶共溅射制备了掺杂Al-Mg-B薄膜。结果表明,Cr、Ti和N都分别充分地进入薄膜中；Al-Mg-B薄膜中掺入Cr元素对薄膜的B12的生长有一定的抑制作用,从而降低了薄膜的硬度；掺入N的薄膜中化学键态主要是sp2型B-N键,从而导致掺N的薄膜硬度仅仅为2 GPa；掺入Ti的薄膜的硬度只有9 GPa,可能主要是由B-O键导致的。总之,掺杂的Al-Mg-B薄膜的性能存在明显的差异,为其后续的研究打下良好基础。更多还原

【Abstract】 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.更多还原