氧化钙薄膜中缺陷诱导的高居里温度铁磁性研究（英文）

通过脉冲激光沉积在(111)取向钇稳定的氧化锆(YSZ)衬底上制备了氧化钙(CaO)薄膜.室温下磁滞回线的实验观测数据表明CaO薄膜具有明显的铁磁性.X射线衍射和X射线光电子能谱分析表明,CaO薄膜为(111)取向,没有杂质相.在高真空条件下生长和退火的CaO薄膜都表现出铁磁性磁化行为,而在相应的CaO靶材上没有检测到这种铁磁性.结果表明,氧空位浓度与氧化钙薄膜的磁化强度之间存在一定的相关性,后退火对CaO薄膜磁性的影响说明,氧空位浓度与氧化钙薄膜的铁磁性是相关的.     

择优取向MgO缓冲层上制备的硅基Ba0.7Sr0.3TiO3薄膜的结构和性能研究

分别采用sol-gel法和磁控溅射法在Si(001)单晶衬底上制备出(111)和(001)取向的MgO缓冲层薄膜,随后在其上生长Ba0.7Sr0.3TiO3(BST30)铁电薄膜.通过X射线衍射,扫描电子显微镜,原子力显微镜等方法研究了薄膜的微结构.实验结果发现,在较厚的MgO(001)缓冲层上可长出(101)取向的BST30薄膜,而在较薄的MgO(111) 缓冲层上则表现出(101)和(111)取向相互竞争的现象,随着MgO(111)缓冲层厚度的增加,BST30薄膜的(101)取向被抑制,而(001)取向逐渐增强.利用反射率测定仪、阻抗分析仪研究了BST30薄膜的光学和电学性能. 通过改进的单纯形法拟合反射率曲线,得到了BST30及其MgO缓冲层薄膜的光学常数, 由BST30薄膜的电压-电流特性(I-V曲线),发现MgO缓冲层对BST30薄膜的漏电流有明显的阻隔作用,可以有效消除BST30膜层的p-n结效应.     

强磁场对酞菁铁薄膜分子取向及形貌的影响

有机半导体器件的性能在很大程度上受有机分子取向和堆积方式的影响,研究调控有机分子取向的方法对优化器件性能有重要意义.在强磁场(8.5 T)下使用有机分子束沉积方法在Si(111)衬底上制备了酞菁铁薄膜,应用X射线衍射,角分辨近边X射线吸收精细结构、偏振激光拉曼光谱,原子力显微镜等技术研究了磁场对酞菁铁薄膜的分子取向和形貌的影响.结果表明,酞菁铁分子相对于衬底呈侧立构型并形成α相的薄膜.在强磁场作用下,分子平面与衬底的夹角由63.6°增大为67.1°,形成薄膜的结晶度明显提高,晶粒更加均匀,在衬底上的分布更加有序.     

Mn-Na共掺ZnO非极性薄膜的结构及其光电磁性能研究

非极性方向生长的ZnO基多量子阱消除了量子限域Stark效应, 可以提高光电器件的发光效率. 据此我们采用脉冲激光沉积方法(PLD)在r面蓝宝石衬底上生长了高质量的a面(1120)单一取向非极性Zn(Mn,Na)O薄膜. X射线衍射(XRD)、场发射扫描电子显微镜(FE-SEM)、Hall测试、X射线光电子能谱(XPS)等测试结果表明: 衬底温度和生长气压对Zn(Mn,Na)O薄膜的非极性生长影响很大, 在600℃和0.02 Pa条件下实现了Mn-Na共掺, 得到了高结晶质量并具有良好光电性能的非极性Zn(Mn,Na)O薄膜. 此外, 我们还利用超导量子干涉仪(SQUID)研究了Zn(Mn,Na)O薄膜的生长取向对其室温铁磁性能的影响规律, 并对引起磁性变化的机理进行了讨论.     

Pb1－xMnxSe薄膜的光学特性

采用分子束外延的方法在BaF₂(111)衬底上制备出了高质量的Pb_1-xMn_xSe(0≤x≤0.0681)薄膜.X射线衍射结果表明，Pb₁-xMn_xSe薄膜为立方相NaCl型结构，没有观察到MnSe相分离现象，薄膜的取向为平行于衬底(111)晶面.晶格常数随着Mn含量的增加逐渐减小，Mn含量由Vegard公式得到.通 关键词： 1-xMn_xSe外延薄膜')" href="#">Pb_1-xMn_xSe外延薄膜 透射光谱 带隙 折射率     

退火氛围对掺杂ZnO薄膜磁性的影响

采用直流磁控反应共溅法制备了非磁性元素Al和磁性元素Co掺杂的ZnO薄膜, 样品原位真空退火后再空气退火处理. 利用X射线衍射仪(XRD) 和物理性能测量仪(PPMS) 对薄膜的结构和磁性进行了表征. XRD和PPMS结果表明, 不同的退火氛围对掺杂薄膜的结构和磁性有着很大的影响. 真空退火的Al掺杂ZnO薄膜没有观察到铁磁性, 而空气退火的样品却显示出明显的室温铁磁性, 铁磁性的来源与空气退火后导致Al和ZnO基体间电荷转移增强有关. 而对于Co掺杂ZnO薄膜, 真空退火后再空气退火, 室温铁磁性明显减弱. 其磁性变化与Co离子和ZnO基体间电荷转移导致磁性增强和间隙Co原子被氧化导致磁性减弱有关.     

择优取向MgO缓冲层上制备的硅基Ba0.7Sr0.3TiO3薄膜的结构和性能研究

分别采用sol-gel法和磁控溅射法在Si（001）单晶衬底上制备出（111）和（001）取向的MgO缓冲层薄膜,随后在其上生长Ba_0.7Sr_0.3TiO₃（BST30）铁电薄膜.通过X射线衍射,扫描电子显微镜,原子力显微镜等方法研究了薄膜的微结构.实验结果发现,在较厚的MgO（001）缓冲层上可长出（101）取向的BST30薄膜,而在较薄的MgO（111） 缓冲层上则表现出（101）和（111）取向相互竞争的现象,随着MgO（111）缓冲 关键词： 0.7Sr_0.3TiO₃')" href="#">Ba_0.7Sr_0.3TiO₃ 铁电薄膜 择优取向 sol-gel     

沉积温度对YBCO薄膜取向的影响

采用脉冲激光沉积技术(PLD)在SrTiO3(100)单晶衬底上制备YBCO薄膜,用X射线对薄膜的取向和织构进行表征,用扫描电子显微镜(SEM)对薄膜的表面形貌进行观察.实验主要研究了衬底温度对薄膜外延取向的影响,结果表明在770℃温度下制备的YBCO有较多的a轴晶粒生成,在800℃温度下制备的YBCO是纯的c轴取向,且平均面内φ扫描半高宽(FWHM)为1.2°,超导转变宽度(△Tc)为0.9K.     

苝四甲酸二酐在Au(111)表面的取向生长及电子结构研究

利用X射线光电子能谱(XPS),同步辐射紫外光电子能谱(SRUPS),近边X射线吸收精细结构(NEXAFS)以及原子力显微镜(AFM)等技术研究了苝四甲酸二酐(PTCDA)与Au(111)的界面电子结构、PTCDA分子取向及有机薄膜的表面形貌.SRUPS价带谱显示,伴随PTCDA分子的微量沉积(0·5ML),位于费米能级附近Au的表面电子态迅速消失,但却观察不到明显的界面杂化态,这说明PTCDA分子和Au(111)界面间存在弱电子传输过程,但并没有发生明显的化学反应.角分辨NEXAFS以及SRUPS结果证明PTCDA分子是平铺在衬底表面.根据Au4f7/2和C1s峰积分强度随薄膜厚度的变化以及AFM图像可知,PTCDA分子在Au(111)表面是一种典型的Stranski-Krastanov生长模式,即先层状生长,再岛状生长,并且在层状生长到岛状生长的转变过程中,存在有机分子的去润湿过程.     

Al掺杂ZnO薄膜的厚度对其结构及磁学性能的影响

采用直流磁控共溅的方法在玻璃基底上制备了不同厚度的Al掺杂ZnO薄膜,并在真空和空气中分别退火.利用X射线衍射仪(XRD)和物理性能测量仪(PPMS)对系列薄膜的结构和磁性进行了表征.XRD结果显示:随着膜厚的增加,晶粒尺寸逐渐增大,薄膜的内应力逐渐减小.在空气退火的薄膜样品中观察到了室温的铁磁性,薄膜的饱和磁化强度M_s 随着膜厚的增加而增大,而矫顽力H_c却随着膜厚的增加而减小. 关键词： Al掺杂ZnO薄膜 薄膜厚度 应力 铁磁性     

Room temperature ferromagnetism in Ni-doped ZnO films

Zn_1−xNi_xO (x = 0.02, 0.03, 0.04, 0.05, 0.07) films were prepared using magnetron sputtering. X-ray diffraction indicates that all samples have a wurtzite structure with c-axis orientation. X-ray photoelectron spectroscopy results reveal that the Ni ion is in a +2 charge state in these films. Magnetization measurements indicate that all samples have room temperature ferromagnetism. In order to elucidate the origin of the ferromagnetism, Zn_0.97Ni_0.03O films were grown under different atmospheric ratios of argon to oxygen. The results show that as the fraction of oxygen in the atmosphere decreases, both the saturation magnetization and the number of oxygen vacancies increase, confirming that the ferromagnetism is correlated with the oxygen vacancy level.     

Defects enhanced ferromagnetism in Cu-doped ZnO thin films

We present here new evidences of point defects enhanced ferromagnetism in Cu-doped ZnO thin films by different characterization methods. Cu-doped ZnO thin films with Cu concentrations ranging from 0.05 to 5 at.% were prepared by an inductively coupled plasma enhanced physical vapor deposition system. Room-temperature ferromagnetism is observed in all the films. The saturation magnetization shows an increasing trend with the increase of Cu concentration except a slight decrease for the 1 at.% Cu-doping. Further study performed by Raman spectra, X-ray absorption spectra and extended X-ray absorption fine structure indicate the existence of Cu²⁺ ions and point defects in all the films. The local structural characterization and magnetic properties reveal that the sample with larger saturation magnetization has a higher concentration of point defects.     

Preparation, structure and ferromagnetic properties of the nanocrystalline Ti1-xMnxO2 thin films grown by radio frequency magnetron co-sputtering

This paper reported that the Mn-doped TiO2 films were prepared by radio frequency （RF） magnetron cosputtering. X-ray diffraction measurements indicate that the samples are easy to form the futile structure, and the sizes of the crystal grains grow big and big as the Mn concentration increases. X-ray photoemlssion spectroscopy measurements and high resolution transmission electron microscope photographs confirm that the manganese ions have been effectively doped into the TiO2 crystal when the Mn concentration is lower than 21%. The magnetic property measurements show that the Ti1-xMnxO2 （x = 0.21） films are ferromagnetic at room temperature, and the saturation magnetization, coercivity, and saturation field are 16.0 emu/cm^3, 167.5 × 80 A/m and 3740 × 80 A/m at room temperature, respectively. The room-temperature ferromagnetism of the films can be attributed to the new futile Ti1-xMnxO2 structure formed by the substitution of Mn^4＋ for Ti^4＋ into the TiO2 crystal .lattice, and could be explained by O vacancy （Vo）-enhanced ferromagnetism model.     

基于XPS与XAS的稀磁半导体GaMnN电子结构研究

采用基于同步辐射技术的X射线光电子能谱(XPS)与X射线吸收谱(XAS)测试由金属有机化学气相沉积(MOCVD)技术制备的不同Mn掺杂浓度的稀磁半导体GaMnN薄膜的电子结构,探究Mn掺杂浓度对磁性原子Mn周围的局域环境和电子态等方面的影响,并阐述材料铁磁性变化的机理. XPS和XAS图谱分析表明：Mn²⁺和Mn³⁺共存于薄膜样品内,样品D中Mn²⁺占比高达70%-80%,N空位随Mn掺杂浓度增加而增多且N空位能够使空穴浓度降低,导致Mn 3d和N 2p轨道间的相互交换作用减小,从而减弱体系铁磁性.此外,Mn不同的掺杂浓度会影响GaMnN薄膜p-d耦合杂化能力的强弱,当掺Mn 1.8%时具有较强的p-d耦合杂化能力.     

Effect of vanadium on the room temperature ferromagnetism of V-doped 6H-SiC powder

This study focuses on the effect of V-doping on the ferromagnetism(FM) of 6H-SiC powder.The X-ray diffraction results indicate that V is inserted into the 6H-SiC lattice.The Raman spectra reveal that with a V concentration of 25 ppm,the crystalline quality and carrier concentration of 6H-SiC are hardly varied.It is found that after the V-doping process,the saturation magnetization(Ms) and the vacancy concentration of 6H-SiC are both increased.From these results,it is deduced that the effect of V might contribute mainly to the increase of vacancy concentration,thus resulting in the increase of Ms of V-doped 6H-SiC.     

用热丝CVD技术制备场发射冷阴极金刚石薄膜

以甲烷和氢气的混合气体为原料,用热丝化学汽相淀积法,在(100)硅衬底上800℃温度时异质生长出适合场发射的金刚石薄膜.然后用扫描电子显微镜、X射线衍射仪、透射电子显微镜和喇曼光谱仪等对其进行了分析,结果表明,所制备的薄膜是多晶金刚石,而且在(111)晶相择优生长.在扫描电子显微镜下(111)晶粒的外形几乎都是四面体结构,具有很多尖端,可以加强一定电压下的电场,所以所制备的薄膜能够满足低压场发射的要求.     

Effects of temperature and atmosphere on the magnetic properties of Co-doped ZnO rods

Co-doped ZnO (Zn_0.95Co_0.05O) rods are fabricated by co-precipitation method at different temperatures and atmospheres. X-ray diffraction, Energy dispersive X-ray spectroscopy and Raman results indicate that the samples were crystalline with wurtzite structure and no metallic Co or other secondary phases were found. Raman results indicate that the Co-doped ZnO powders annealed at different temperatures have different oxygen vacancy concentrations. The oxygen vacancies play an important role in the magnetic origin for diluted magnetic semiconductors. At low oxygen vacancy concentration, room temperature ferromagnetism is presented in Co-doped ZnO rods, and the ferromagnetism increases with the increment of oxygen vacancy concentration. But at very high oxygen vacancy concentration, large paramagnetic or antiferromagnetic effects are observed in Co-doped ZnO rods due to the ferromagnetic-antiferromagnetic competition. In addition, the sample annealed in Ar gas has better magnetic properties than that annealed in air, which indicates that O₂ plays an important role. Therefore, the ferromagnetism is affected by the amounts of structural defects, which depend sensitively on atmosphere and annealing temperature.     

The effect of annealing on the room temperature ferromagnetism in co-sputtered In2O3: C thin films

In this paper, we report investigation of room temperature (RT) ferromagnetism in In₂O₃ (InO) thin films doped with carbon prepared by the co-sputtering method. InO thin films both undoped and C doped with varied thicknesses in the range of 45 to 80 nm were synthesized on Si substrates with varied C concentrations. The carbon concentration was varied from 1.6 to 9.3 at%. The undoped InO films showed no trace of ferromagnetism. Carbon doped films (InO:C) exhibited ferromagnetism at RT, which was of the orders of 10⁻⁵ emu and varied strongly with C concentrations. It is observed that the magnetization reached a maximum value of 5.7 emu/cm³ at 4 at% C. Annealing of the InO:C films in an oxygen environment resulted in a decrease in the magnetization, indicating the crucial role of oxygen vacancies in the films. It is concluded that the oxygen vacancies were important and compete with C substitution for the RT ferromagnetism.     

氧空位对钴掺杂氧化锌半导体磁性能的影响

从实验和理论上阐述了氧空位对Co掺杂ZnO半导体磁性能的影响.采用磁控溅射法在不同的氧分压下制备了Zn_095Co_005O薄膜,研究了氧分压对薄膜磁性能的影响.实验结果表明,高真空条件下制备的Zn_095Co_005O薄膜具有室温铁磁性,提高氧分压后制备的薄膜铁磁性逐渐消失.第一性原理计算表明,在Co掺杂ZnO体系中引入氧空位有利于降低铁磁态的能量,铁磁态的稳定性与氧空位和Co之间的距离密切相关. 关键词： Co掺杂ZnO 稀磁半导体 第一性原理计算 氧空位缺陷     

Ferromagnetism of MnxLiyZn1−x−yO films

We had prepared Mn-doped ZnO and Li, Mn codoped-ZnO films with different concentrations using spin coating method. Crystal structure and magnetic measurements demonstrate that the impurity phases (ZnMnO₃) are not contributed to room temperature ferromagnetism and the ferromagnetism in Mn-doped ZnO film is intrinsic. Interesting, saturated magnetization decreases with Mn or Li concentration increase, showing that some antiferromagnetism exists in the samples with high Mn or Li concentration. In addition, Mn_0.05Zn_0.95O film annealed in vaccum shows larger ferromagnetism than the as-prepared sample and more oxygen vacancies induced by annealing in reducing atmosphere enhance ferromagnetism, which supports the bound magnetic polaron model on the origin of room temperature ferromagnetism.