Influence of oxygen content on the crystallinity of MgO layers in magnetic tunnel junctions

With RF sputtering process, Si/Si02/Ta/Ru/Ta/CoFeB/MgO/CoFeB/Ta/Ru structure has been grown on Si （100） substrate. Attempting different targets and adjusting the oxygen dose, the crystallization quality of the MgO layer is studied. The X-ray diffraction measurements demonstrate that crystal structure and crystallization quality of MgO layers are related to the type of target and concentration of oxygen in sputtering process. With the method sputtering Mg in an ambient flow of oxygen, not only the crystallization quality of a normal MgO layer with lattice constant of 0.421 nm is improved, but also a new MgO crystal with lattice constant of 0.812 nm is formed and the perpendicular magnetic anisotropy of CoFeB is enhanced. Also it is found that crystallization quality for both the normal MgO and new MgO is more improved with MgO target and same oxygen dose, which means that this new method is helpful to form a new structure of MgO annealed at 400 ℃ in vacuum. with lattice constant of 0.812 nm. All of the samples were     

Mn离子注入Mg掺杂GaN的微结构和光学特性研究

通过Mn离子注入Mg掺杂GaN外延层制备了铁磁性GaN∶Mn薄膜,利用拉曼散射和光致发光谱研究了退火温度对薄膜微结构和光学特性的影响。拉曼谱测试显示由离子注入相关缺陷引起了新的声子模,分析认为Mn离子相关的局域振动(LVM)紧邻Ehigh2峰。光致发光谱观察到位于1.69,2.54和2.96eV的3个新的发光峰,分析认为2.96eV的发光峰来自MgGa-VN复合体深施主能级和Mg的浅受主能级之间的辐射复合跃迁,2.54eV的发光峰来自浅施主能级和深受主能级之间的辐射复合跃迁,对于位于1.69eV的新发光峰不排除来自MgGa-VN复合体深施主能级和Mn相关深受主能级之间辐射复合跃迁的贡献。