【作者】 黎明锴；

【导师】 范湘军；

【作者基本信息】 武汉大学 ， 凝聚态物理， 2004， 博士

【摘要】 本工作研究了中频磁控溅射制备AIN薄膜和nc-AIN／a-Si₃N₄复合薄膜及其结构与特性，并且研究了Mn⁺离子注入AIN薄膜的电学和磁学性质。 最近的研究表明氮化物半导体是很有希望被用作光电器件（包括发光器件和感应器件），高功率和高温电子器件的材料。AIN具有6.28eV的直接带隙使得其在紫外光范围具有透光窗口，如果进行掺杂还可能得到在紫外光范围内发光的光电器件。AIN有许多十分有用的机械和电学性质，它具有的高硬度、高热导性、耐高温、耐腐蚀，与Si和GaAs有合理的温度适配性，使得AIN能够作为很好的电子封装材料。同时AIN不受电磁辐射、电子和离子轰击的影响。AIN还能与GaN形成合金AIGaN，从而能够制造出基于AlGaN／GaN的电子和光学器件，这种器件能够在绿光波长到紫外光波长都有效，这是十分诱人的。 早期合成AIN薄膜使用磁控溅射、等离子体放电、升华和化学气相沉积（CVD）等方法，其中CVD方法是最广泛使用的。该方法的特点在于使用含铝的化合物与氨水在高温下反应得到AIN。激光烧蚀法（PLD）沉积薄膜是较常见的一种方法。王洪海等人使用XeCl准分子激光烧蚀铝靶，使Al溅射出来与放电离化的N₂⁺反应生成AIN。 最常用于生长AIN薄膜的技术是反应磁控溅射技术。尽管使用溅射的方法得到的薄膜多为多晶甚至非晶，但是该方法简单易行而且便宜。许多研究小组分别用射频和直流磁控溅射研究了AIN薄膜的生长条件。Long Wu等用射频磁控溅射成功制备出c轴取向的AIN薄膜。 由于AIN是绝缘材料，尽管使用的是纯金属Al靶，但是如果直接用直流溅射，在工作一段时间之后靶表面和真空室内其它部件上就会覆盖上一层绝缘的AIN薄膜，导致靶中毒和阳极消失现象出现。为了解决这些问题，我们在这里使用了中频电源。中频电源输出40kHz对称矩形波，通过输出网络与负载匹配。另外选用15kHz的脉冲偏压防止正电荷积累太多就会引起弧光放电，影响镀膜工艺的稳定和薄膜的质量。 由于AIN薄膜的应用与其质量密切相关，为此我们研究在磁控溅射制备AIN薄膜的过程中，反应气体对薄膜的微结构及其性质的影响，以及衬底对微结构的影响，从而找到AIN薄膜的最佳制备工艺。 对不同N₂气流量下制备的AIN薄膜的结构和光学性质的测试表明，在中频磁控溅射沉积过程中，N₂气流量是影响AIN薄膜质量的重要因素之一。在较低的N₂气流量下 AIN薄膜的晶粒较小，取向性较差，导致薄膜的硬度较低，光学性能较差。在较高的 N:气流量下AIN薄膜的晶粒较大，取向性较好，薄膜的硬度达到20.4GPa，光学折射率 也较大。过高的N:气流量使得溅射速率下降，导致薄膜的性能有所降低。为了研究衬 底对AIN薄膜生长的影响，对比在Si（1 11）和玻璃两种衬底上AIN薄膜的微结构，结 果表明在上述两种衬底上AIN薄膜的生长方式有所不同，使得相同条件下生长的AIN 薄膜的微结构和形貌都有较大的差异。 在传统半导体材料中电子的两个自旋状态的能量几乎是简并的，所以半导体中电子 的自旋自由度长期以来被忽视了。然而随着半导体科技的发展，控制操纵半导体中的自 旋自由度逐渐成为可能。利用自旋自由度可以增强现有器件和电路的功能使得在存储信 息的同时进行信息处理，使用在固体中的自旋作为量子位来实现量子信息处理也是其重 大的潜在应用之一。在未来半导体中的电荷与自旋自由度都将扮演重要的不可缺少的作用，半导体电子学中的这个领域就被称之为半导体自旋电子学。 随着宽禁带半导体研究的逐渐成熟，稀磁半导体的研究也逐渐从H一Vl族化合物转向111一V族化合物，特别是氮化物宽禁带半导体。从理论计算我们知道大的禁带宽度能够得到更高的临界温度，从而预言了（Ga，Mn）N能够实现室温的铁磁性。目前GaN的制备工艺十分成熟，而且被广泛用于各种晶体管和激光器中，这使得有望将自旋电子器件与传统集成电路很好的结合起来。在GaN方面，2001年Shon等人在GaN的外延薄膜中注入Mn+离子得到了铁磁性的（Ga，Mn）N。Hashimoto等人成功合成了室温下的磁性半导体（Ga，Cr）N。理论研究表明，Cr和Mn掺杂的AIN有可能在室温下表现出铁磁性。2002年，Yang等人利用反应磁控溅射制备出（Al，Cr）N，在300K获得铁磁性。Cr溶解在AIN的晶格中，有效磁性受主能级到价带之间的跃迁导致的间接交换相互作用是（Al，Cr）N表现出铁磁性的主要原因。2003年Fraziar等人研究Co、Cr、Mn注入AIN的特性时发现，Co、cr、Mn掺杂都能表现出铁磁性，但是掺杂后的AIN的电阻依然大于10’“0 cm，所以不适合用传统的以载流子为媒介产生铁磁性的理论来解释。平均场理论认为Mn在AIN中不是均匀分布的而是形成团簇，这样使得自旋极化空穴局域在其周围从而显著提高临界温度。基于LSDA的第一性原理计算也发现现在第二近邻位置磁性离子形成二聚物或三聚物能够十分有效地形成铁磁性。有的研究小组提出了类似渗透网络的模型来解释低载流子浓度系统的铁磁性问题。最近的实验表明Mn作为替位原子占据了Al的晶格位置使得AIMnN的晶格常数减小，在室温下观察到的磁滞回线是AIM瓦N表现出来的，而不是其他的成分或团簇表现出来的。?更多还原

【Abstract】 This thesis presents investigations on the structure and properties of A1N films and nc-AlN/a-Si3N4 prepared by medium frequency magnetron sputtering. The cathodoluminescence and magnetic properties of Mn+ implanted A1N films are also studied.Recently researchs indicate that nitride based semiconductor has the potential applications as materials of photoeletric devices (include emittion device and inductor) and high power and high temperature devices. The direct 6.28eV band gap of A1N results in the transparent window at ultraviolet region. The A1N based emittion devices at ultraviolet region will be realized if A1N could be doped siutably. Useful mechanic and electronic properties of A1N such as high hardness and high themal conductance and high temperature resistance and corrosion resistant and siutably temperature adaptation with Si and GaAs make A1N as good electronic encapsulation materials. While A1N is not influenced by electromagnetism radiation and the ions and electrons bombardment. It is interesting that AlGaN/GaN based electronic and optical devices, which are made by alloy of A1N and GaN, are valid from green to ultraviolet region.Among early preparation methods of A1N films, such as magnetron sputtering and plasma discharge and sublimation and chemical vapour deposition (CVD) and etc, CVD is widely used. The CVD feature is that A1N films are prepeared by reaction between compound including Al and ammonia at high temperature. Pulsed laser deposition is one of familiar methods. Wang Honghai used XeCl quasimolecule laser to ablate Al target to deposite AIN by reaction between sputtered Al and ionic N2+.The magnetron sputter technology is the most familiar method for Al films preparation. Although polycrystal and amouphous films are prepeared by this method, it is simply and cheap. Many research groups invastigate th deposition condition of Al films by RF and DC magnetron sputter. Long Wu etc prepeared c-axis preferential AIN films by RF magnetron sputter.Since AIN is insulator, if DC is used for sputter Al target directly, the target surface and components in vacuum chamber will be covered with insulated AIN films although metal Altarget is used. It causes target poison and anode disppearance. To solve these problems, medium frequency (MF) power supply is used in our work. Rectangular wave exported by medium frequency power supply is matched load by a export network. By prevent arc discharge, which affect deposition stability and films quality, due to positive charge accumulation, 15kHz pulsed discharge supply is used.Since it is very interralated between application and quality of AIN films, we study influence of reaction gas for microstructure and properties of AIN films and influence of substrates for microstrucutre at preparation of AIN films by MF magnetron sputter to optimal AIN films deposition conditions.The investigations of the structure and optical properties of AIN films prepared with various N2 gas flux show that N2 gas flux is one most important factor when AIN is prepared by medium frequency magnetron sputtering. At low N2 gas flux, the small gains and poor orientation cause low hardness and poor optical properties. At high N2 gas flux, large gains and perfect orientation cause high hardness 20.4GPa and high refrective index. But excessive N2 gas flux casue the deposition rate dropping, and the propeties become bad. The influence of various substates is invastigated. The result of comparing the microstructure of AIN films on Si(111) substrate and glass substrate indicate that the modes and the microstructure and morphology of AIN films growing on two substrates have many difference.Degree of freedom of electronic spin has been ingored for long term because energy of electronic two spins status is almost degenerate. With semiconductor technology development, it becomes possible to control degree of freedom of semiconductor spin gradually. By using defree of freedom of spin the functions of existing devices and circuits can be enhanced to process information while information i更多还原