【作者】 阮海波；

【导师】 孔春阳；

【作者基本信息】 重庆师范大学 ， 理论物理， 2009， 硕士

【摘要】 ZnO的室温禁带宽度是3.37eV,激子束缚能高达60meV,作为一种重要的光电信息功能材料,其p型掺杂问题是目前国际上最为关注的前沿领域。与此同时,由于ZnO通过适当地掺杂过渡金属离子有望实现室温铁磁性,有关ZnO基稀磁半导体(DMS)的研究也逐渐成为热点。本文针对目前ZnO研究中的热点问题,采用射频磁控溅射法制备较高结晶质量的ZnO:Mn薄膜,并结合N离子注入完成ZnO薄膜的Mn-N两步法共掺杂。通过在N2气氛中适当条件的快速退火,使注入的N离子达到电激活成为有效受主,进而实现p型转变。借助X射线衍射仪(XRD)、场发射扫描电镜(F-SEM)、霍尔测试仪、X光电子能谱(XPS)、双光束紫外-可见分光光度计、样品振动磁强计对ZnO:Mn-N薄膜进行了结构、表面形貌、电学、元素组分及化学状态、光学、磁学等方面的测试。结果表明采用二步法共掺杂技术制备的ZnO:Mn-N薄膜具有良好的晶体质量,晶粒呈柱状结构,沿垂直于衬底的(002)方向生长。经退火后,没有观察到其它杂质相的生成。薄膜在650℃经10～30min退火时均可实现p型转变,空穴浓度可达1016-1018cm-3,表明650℃可能为ZnO:Mn-N体系中N离子达到电激活成为有效受主的温度。XPS能谱证明了Mn2+、N3-离子的掺入。在热退火作用下,部分间隙位N离子通过扩散进入O空位,形成N-Zn或N-Mn键,是样品转变为p型的依据。XPS深度剖析还发现在热退火作用下,N和Mn在薄膜体内分布比较稳定,且随刻蚀深度的增加变化不大,表明在薄膜中N离子由退火前的高斯分布趋向于均匀分布。XPS的量化分析结果表明Mn和N在薄膜体内的摩尔百分比浓度分别为～4 at.%和～1 at.%。未退火的n型与650℃退火10min的p型ZnO:Mn-N薄膜均具有室温铁磁性,矫顽力分别为40Oe与65Oe, p型样品比n型的饱和磁化强度明显增大,使用束缚磁极化子模型(BMP)对样品的磁性来源作了解释。此外,在成功实现ZnO:Mn-N薄膜p型转变的基础上,本文还在650℃20min对不同样品进行了重复性退火,样品的空穴浓度均达到～1017cm-3;在对样品进行长期的跟踪测试中,发现p型ZnO:Mn-N薄膜的电学性能在历经六个月后虽然存有不同程度的弱化,但整体表现良好,薄膜导电类型依然为p型。更多还原

【Abstract】 The semiconductor ZnO has gained substantial interest in the research of optoelectronic applications, which has band gap of 3.37eV at room temperature, and the binding energy of exciton as high as 60 meV. The renewed interest focusing on ZnO is fueled by reports of p-type conduction and ferromagnetic behavior when doped with transtions metals, both of which remain controversial.In this dissertation, our works are focused on p-type ZnO:Mn diluted magnetic semiconductor films. p-Type conductive Mn–N codoped ZnO thin films have been fabricated on quartz glass substrates by radio-frequency magnetron sputtering technique together with the direct implantation of N ions and post-annealing at appropriate condition in flowing N2 gas. The crystal structure, surface morphology, chemical bonding states and chemical compositions, electrical, optical and magnetic properties of the ZnO films are investigated by x-ray diffraction(XRD), field emission scanning electron microscopy(FESEM), Hall measurement system, X-ray photoelectron spectroscopy(XPS), transmission spectrum and Vibrating Sample Magnetometer (VSM) respectively.XRD and FESEM measurements reveal that the ZnO films which are grown by two steps codoping technic have single-phase wurtzite structure with c-axis preferred orientation, even when annealing later, no manganese oxide or nitride phase are detected. The codoped ZnO films annealed at 650℃from 10 to 30 minutes show good p-type conductivity with the hole concentration of 1016-1018cm-3, indicating that more N acceptors can be activated at the temperature of 650℃. X-ray photoelectron spectroscopy studies suggest that the incorporation of both divalent Mn2+ and trivalent N3- ions into the codoped ZnO films. Owing to electrical activation, a lot of N on substitutional sites can distribute into O site as NO, come into being N-Mn or N-Zn bonds in the films. It should be mentioned that nitrogen here mainly performs as Zn(MnZn)-NO or Zn(MnZn)+2NO complexes which would induce low resistivity p-type conduction. XPS depth profile reveals that the direct implantation of N ions change from Gaussian distribution tends to be uniform distribution under the effect of thermal annealing condition. The quantitative analysis indicate that the concentration of Mn and N in codoped ZnO film are～4.0% and～1.0 at.% respectively. Both samples of the deposit ZnO:Mn-N film and the film annealed at 650℃for 10 minutes exhibit significant ferromagnetism at room temperature(300K) with the coercive field (Hc) of 40Oe and 63Oe respectively. The saturation magnetic moment of the p-type sample is much larger than the n-type sample. The ferromagnetic mechanism in codoped ZnO films is discussed based on a bound magnetic polaron model.In addition, on the basis of p-type ZnO films are prepared successfully, we also do some research about repeatability of the experiments and the stability of the p-type codoped ZnO films. All samples were annealed at 650℃for 20 minutes show good p-type conductivity with the hole concentration of 1017cm-3 around. Although there are some different degrees of weakening, Hall effect measurements were also carried out half a year later and the p-type conductivity of the codoped ZnO films are still well observed.更多还原