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Exploration of new spintronics materials by vapor phase epitaxy approach

气相外延方法探索新型自旋电子学材料

基本信息

批准号：
14076212
负责人：
MATSUMOTO Yuji
金额：
$ 12.48万
依托单位：
Materials and Structures Laboratory
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research on Priority Areas
财政年份：
2002
资助国家：
日本
起止时间：
2002 至 2005
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-14076212/
关键词：
Laser MBE Co : TiO_2 Magneto-optics EXAFS, XANES Combinatorial thin film preparatiorj XMCD magnetic superconductor.3元組成傾斜膜法光磁気光学

项目摘要

(1)Micro-structural analyses and Magnetic circular dichroism study of Co doped TiO_2 thin filmsThe local structure and electronic state of Co in anatase Co_xTi_<1-x>O_2 films were investigated by Co K-shell x-ray absorption near-edge structure (XANES) and extended x-ray absorption fine structure (EXAFS). There are often observed two kinds of Co in +2 formal oxidation state and metallic small clustering. A significant correlation between the observed ferromagnetism and the electronic band structure of TiO_2 host material was suggested by magnetic circular dichroism (MCD) study. Furthermore, synchrotron-radiation XMCD experiment for Co : TiO_2 anatase film concluded that the origin of the ferromagnetism was from Co^<2+> state but not from metallic Co.(2)Low temperature growth of Co-doped rutile thin film on the ultra-smooth TiO_2 single crystal substrateAn ultra-smooth TiO_2 single crystal substrate was developed to exhibit a step and terrace structure. On the ultra-smooth substrate, the … More homo-epitaxial growth of TiO_2 was found to proceed even at 300℃, relatively much lower than that for the TiO_2 growth on a conventionally used stepped □-sapphire substrate. The low temperature growth enabled to grow a high-quality Co-doped TiO_2 film with no impurity phase. X-ray photoelectron spectroscopy and x-ray absorption fine structure revealed that the doped Co in the films took 'a valence state of 2+ and substituted for Ti site. However, the ferromagnetism was not detected down to 4K, owing to the highly insulating nature of the films.(3)Carrier injection into highly insulating Co : TiO_2 filmsAt first, field-effect transistor (FET) was fabricated based on a Co : TiO_2 ruffle active channel. Top-gate transistor structure with amorphous. LaA103 insulator was fabricated on the Co : TiO_2 film grown on a.1102(110) ultra-smooth substrate. However, the high-leakage current property in the film prevented the appropriate performance of the TFT device. Next, during the alternate growth of insulating Co : TiO_2 and conductive TiO_2, an oxygen partial pressure PO_2 was modulated. The ferromagnetism in the artificial lattice was found to increase by decreasing the PO_2 for the growth of TiO_2. This enhancement of the ferromagnetism might be due to carrier injection from the conductive 1102 layer to the insulating Co : TiO_2 layer, as was evidenced by synchrotron-radiation XPS experiments of the Co : TiO_2/Nb : TiO_2 interface.(4)Flux-assisted reactive solid phase epitaxy of highly c-axis oriented Ru(Eu1.5Ce0.5)Sr2Cu2O10_d thin filmsHighly c-axis oriented epitaxial Ru(Eu1.5Ce0.5)Sr2Cu2O10_d (Ru-1222) thin lms were grown on SrTiO3 (001) substrates by a novel growth technique,ux-assisted reactive solid phase epitaxy. The lms grew epitaxially as (100)Ru-1222//(100)SrTiO3 with excellent crystallinity and atomically at terraces and steps. The magnetization dala are consistent with that reported for bulk Ru-1222 samples. The lms are suggested to be grantlar superconducting. Although zero resistance was not obtained at temperatures down to 5 K, the onset of superconducting transition was observed at about 25 K within the ferromagnetic order.(5)Design of Combinatorial Shadow Masks for Complete Ternary-Phase Diagramming of Solid State MaterialsA novel mask was designed for the combinatorial synthesis of a ternary composition spreads library, which allows such libraries to be deposited through a series of simple masks on a rotatable mount. This eliminates the use of complicated actuation of a heated substrate. In our configuration, this design leads to a standard linear phase diagram by varying the growth rate of each constituent nearly linearly from 0 to 100% at a triangular area on the substrate. Film growth occurs as a series of cycles in which one molecular layer of the material is deposited over the entire area of the spread by a synchronization of the mask movement, target exchange, and laser pulses: Less

（1）Co掺杂TiO_2薄膜的微结构分析和磁圆二色性研究<1-x>利用Co K壳层X射线吸收近边结构（XANES）和扩展X射线吸收精细结构（EXAFS）研究了Co掺杂TiO_2薄膜中Co的局域结构和电子态。通常观察到+2形式氧化态和金属小团簇两种Co。磁性圆二色性（MCD）研究表明，TiO_2基质材料的铁磁性与电子能带结构之间存在显著的相关性。此外，Co：TiO_2锐钛型薄膜的同步辐射XMCD实验得出结论，铁磁性的起源是Co^<2+>态，而不是金属Co。（2）在超光滑TiO_2单晶基片上低温生长Co掺杂金红石薄膜制备了一种具有台阶和平台结构的超光滑TiO_2单晶基片。在超光滑基底上， ...更多信息发现TiO_2的均匀外延生长在300℃下也能进行，比在传统的台阶式□-蓝宝石衬底上生长TiO_2的温度低得多。低温生长可以生长出无杂质相的高质量Co掺杂TiO_2薄膜。X射线光电子能谱（XPS）和X射线吸收精细结构分析表明，Co以2+价态取代Ti位。然而，由于薄膜的高度绝缘性，在4K以下没有检测到铁磁性。（3）高绝缘Co：TiO_2薄膜的载流子注入首先，我们制作了基于Co：TiO_2褶皱有源沟道的场效应晶体管（FET）。具有非晶的顶栅晶体管结构。在0.1102（110）超光滑衬底上生长的Co：TiO_2薄膜上制备了LaAl_（103）绝缘体。然而，膜中的高漏电流特性阻止了TFT器件的适当性能。接着，在绝缘性Co：TiO_2和导电性TiO_2的交替生长期间，调节氧分压PO_2。在人工晶格中的铁磁性被发现增加减少PO_2的TiO_2的生长。Co：TiO_2/Nb：TiO_2界面的同步辐射XPS实验表明，这种铁磁性的增强可能是由于载流子从导电的1102层注入到绝缘的Co：TiO_2层。（4）助熔剂辅助反应固相外延生长高c轴取向Ru（Eu_（1.5）Ce_（0.5））Sr_2Cu_2 O_（10）_d薄膜采用助熔剂辅助反应固相外延生长技术，在SrTiO_3（001）衬底上生长了高c轴取向Ru（Eu_（1.5）Ce_（0.5））Sr_2Cu_2 O_（10）_d（Ru-1222）薄膜。lms以（100）Ru-1222//（100）SrTiO_3的形式外延生长，具有良好的结晶性和原子级台阶结构。磁化强度数据与大块Ru-1222样品的磁化强度数据一致。lms被认为是grantlar超导。虽然零电阻没有得到在温度下降到5 K，超导转变的开始观察到在约25 K的铁磁顺序。（5）用于固态材料的完全三元相图的组合阴影掩模的设计设计一种新颖的掩模被设计用于三元组成铺展库的组合合成，其允许这样的库通过一系列简单的掩模沉积在可旋转的底座上。这消除了对加热的基板的复杂致动的使用。在我们的配置中，这种设计通过在衬底上的三角形区域处几乎线性地从0到100%改变每种成分的生长速率而导致标准线性相图。薄膜生长是一系列循环的过程，其中通过掩模移动、靶交换和激光脉冲的同步，在整个铺展区域上沉积一层分子材料：减