【作者】 夏川茴；

【导师】 胡陈果；

【作者基本信息】 重庆大学 ， 凝聚态物理， 2010， 博士

【摘要】 近年来,基于对电子自旋态的产生、输运、控制等的研究,导致了一门新的学科——自旋电子学的诞生。由于自旋电子器件能同时利用电子的电荷属性和自旋属性,它有可能成为电子科学与技术的新革命。稀磁半导体作为自旋电子学的重要基础,目前引起了科学界的广泛关注。稀磁半导体(DMS)是目前国际上研究的热门课题,研究最为广泛的是过渡族金属掺杂的ZnO所制成的DMS。尽管理论和实验上已经取得了可喜的结果,但是到目前为止,虽然人们对磁性半导体的微结构、磁性、电子输运、磁电阻、光学、磁光等性质都作了一些研究,然而来自不同研究小组的结果很不一致,甚至互相矛盾。其中氧化物磁性半导体的磁性起源是争论的焦点。研究者认为磁性可能来源于载流子诱导的交换作用、双交换作用等内禀的机制,也有可能是由于过渡元素在半导体中的溶解渡偏低而形成的铁磁性杂质相而引起的。因此还有许多问题有待于更进一步的研究。本文主要在ZnO基DMS方面开展了一些研究工作。①利用溶液腐蚀法制备了Mn2+离子掺杂的ZnO基稀磁半导体。XRD表明掺杂后的ZnO仍然保持单一的纤锌矿结构,没有任何杂质相产生。XPS表明Mn离子以+2价的形式存在于样品中。从紫外-可见光反射谱中,我们发现吸收边发生了红移。掺杂后样品的室温PL谱除了紫外发射峰外,在蓝光区域还出现了两个新的位于424nm和443nm的发射峰。室温磁滞回线显示样品有明显的铁磁性,剩余磁化强度为0.3902×10-3 emu/cm3,矫顽力为47Oe。我们分析室温铁磁性来源于缺陷调制的Mn2+-Mn2+长程铁磁交换相互作用。②利用溶液腐蚀法制备了不同浓度的Ni2+离子掺杂的ZnO基稀磁半导体。通过改变反应时间控制掺入的Ni2+离子的浓度。XRD发现,随着掺杂浓度的增大,样品中出现了NiO杂质相,证实了Ni在ZnO中的溶解度低于5%。XPS证明Ni离子以Ni2+的形式掺入ZnO的晶格。室温下的PL谱的紫外发射峰随着掺杂量的增加,峰强减弱,并出现了红移。当样品中掺入过多的Ni后,由于Ni离子会与ZnO中的部分氧离子形成NiO杂质,相应在ZnO中会出现氧空位,因此在该样品中还观察到了由于氧空位引起的绿光发射峰。不同浓度的样品都观察到了室温铁磁性,对应Ni的浓度分别为2.38,4.35和5.54 at%,剩余磁化强度分别为0.454,0.605和0.526emu/cm3。③用溶液腐蚀法制备了Fe掺杂的ZnO纳米棒阵列。通过调节反应时间控制掺入Fe元素的含量。XRD测试发现随着掺入的Fe增多,有ZnFe2O4杂质产生。XPS分析发现样品中Fe都以接近+3价存在。研究了掺杂对样品光学性质的影响,室温PL谱发现掺杂后紫外发射峰出现了红移,并且随着掺杂量的增多峰强在减弱。掺杂后由于有锌间隙缺陷的形成,三个样品都在蓝光区域产生了发射峰。同时对于有ZnFe2O4杂质产生的样品在绿光区域出现了一个发射峰。对样品进行了磁性的研究,掺杂前的ZnO在室温下表现出顺磁性,掺杂后,M-H曲线表现出明显的磁滞行为,证明Fe的掺杂使ZnO具有了室温铁磁性。三个样品的剩余磁化强度分别为0.372,0.613和0.557 emu/cm3,矫顽力分别为99.33,117.3和24.4 Oe。④由于Cu是非磁性离子,因此研究Cu离子掺杂是否引起铁磁性可以用来证明DMS中的铁磁性是否是材料本征的关键。因此,我们用溶液腐蚀法制备了Cu掺杂的ZnO。研究了掺杂对样品光学性质的影响,室温PL谱测试发现掺杂后紫外发射峰出现了红移。同时,Cu离子进入ZnO晶格引入了如锌间隙以及氧空位等缺陷造成PL谱在蓝光区域和绿光区域出现了发射峰。对样品进行了磁性的研究,掺杂前的ZnO在室温下表现出顺磁性,掺杂后,M-H曲线表现出明显的磁滞行为,证明Cu的掺杂使ZnO具有了室温铁磁性。由于Cu是非磁性离子,因此由于Cu离子的掺杂而引起的室温铁磁性证实了样品的磁性是材料本征的。更多还原

【Abstract】 In recent years, based on the research of produce, transportation and manipulation of electron spin, a new subject called“Spintronics”emerges. Due to the possibility of controlling both the spin and charge of electron, spintronics might bring a new revolution in the field of trasitional electronics. Meanwhile, as the footstone of designing spin-based devices, diluted magnetic semiconductors have now draun dramatic attentions.The research on diluted magnetic semiconductors is one o f the frontiers of modern physics. As one of the most promising DMS candidates, transition metals doped ZnO has been receiving great attention very recently. Although there have been many inspiring results in both theoretic and experimental fields, some questions are still to be further solved. The researchers have done some research on the micro-structure、magnetic、electronic transport、magnetic resestance、optical、magneto-optical and other properties of magnetic semiconductors, the results are inconsistent even contradictory. The origin of ferromagnetic is the focus of debate of oxide magnetic semiconductor. Researchers believed the magnetic come from the carrier induced exchange interaction, double exchange et al intrinsic mechanisms. Also, it may be due to the low dissolve of the transition elements in semiconductor which lead to the ferromagnetic impurity phase. Therefore, there are many issues to be solved further. In this paper, we mainly focus on the ZnO-based DMS to do some research.①We have investigated the properties of Mn-doped ZnO nanocrystalline film grown on zinc foil by corrosion-based strategy. The X-ray photoelectron spectroscopy show the manganese doped in ZnO exists as Mn2+. UV-vis spectra exhibit a decrease in the band gap after being doped with Mn. The photoluminescence spectrum of the Mn-doped ZnO film shows the two strong new peaks, blue emission peaks centered at 424 nm and 443 nm, except the UV emission peak owing to the band gap of ZnO semiconductor. The magnetic property of the Mn-doped ZnO exhibits a room temperature ferromagnetic characteristic with a saturation magnetization (Ms) of 0.3902×10-3 emu/cm2 and a coercive field of 47 Oe.②Ni-doped ZnO rod arrays have grown on zinc foils by corrosion-based strategy. The doping Ni content could be controlled by varying the reaction time. The X-ray diffraction and X-ray photoelectron spectroscopy indicated that the Ni ions are incorporated into the ZnO lattices as Ni2+ ions. However, NiO forms when the Ni content is more than 5 at %. Photoluminescence peak of the rod arrays shifts to a little longer wavelength and its intensity decreases with the increase of Ni content. The green light emission as a result of oxygen vacancies was observed when excessive Ni ions were doped in ZnO. The rod arrays have exhibited room-temperature ferromagnetic behavior with the remanence of 0.454, 0.605 and 0.526 emu/cm3 for the Ni concentration of 2.38, 4.35 and 5.54 at%, respectively.③Fe-doped ZnO rod arrays have grown on zinc foils by corrosion-based strategy. The doping Fe content could be controlled by varying the reaction time. The X-ray diffraction and X-ray photoelectron spectroscopy indicated that the Fe ions are incorporated into the ZnO lattices as Fe3+ ions. However, ZnFe2O4 forms when more Fe ions incorporated into the ZnO. Photoluminescence peak of the rod arrays shifts to a little longer wavelength and its intensity decreases with the increase of Fe content. Blue emission peak can be found in these three sampls. The green light emission as a result of oxygen vacancies was observed when excessive Fe ions were doped in ZnO. The rod arrays have exhibited room-temperature ferromagnetic behavior with the remanence of 0.372, 0.613, 0.557 emu/cm3 and the coercivity are 99.33, 117.3, 24.4 Oe respectively.④Because the Cu is non-magnetic ions, to study the Cu doping could give rise to ferromagnetism or not is very important. Cu-doped ZnO rod arrays have grown on zinc foils by corrosion-based strategy. PL spectra exhibit a red shift for the UV emission peak after being doped with Cu. There are two emission peaks in blue and green region for the interstitial zinc defects and oxygen vacancy defects caused by Cu ions incorporation. The magnetic property of the Cu-doped ZnO exhibits a room temperature ferromagnetic. The Cu is nonmagnetic ions. The room temperature ferromagnetic caused by Cu ions’incorporation is a strong evidence for the ferromagnetic is intrinsic of the samples.更多还原