晶粒尺寸对气相沉积薄膜磁取向生长的影响研究

为了研究强磁场下薄膜取向生长规律,采用真空蒸发气相沉积法分别制备了不同磁场方向生长的Zn和Bi薄膜.XRD结果发现磁化率差异较小的Zn薄膜在4T时产生了明显的取向生长,而磁化率差异较大的Bi薄膜在5T磁场强度还没有发生取向生长.SEM结果显示Zn薄膜和Bi薄膜晶粒尺寸上有明显的差别,利用Zn薄膜在4T磁场下的取向建立晶粒尺寸和取向生长的对应关系,提出薄膜发生取向时晶粒的磁化能须大于热能kT的420倍.薄膜是否发生取向生长取决于三个因素:薄膜单个晶粒的大小V,材料不同晶向的磁化率差异Δ关键词： 强磁场 磁取向 薄膜生长 材料电磁加工     

中子探测晶体Li6Gd(BO3)3:Ce的光谱特性研究

文章用提拉法生长出Li₆Gd(BO₃)₃:Ce晶体,并对其光谱性能与发光过程进行了探索. 借助于真空紫外-紫外透过光谱测试,发现晶体的透过光谱中存在Ce³⁺离子和Gd³⁺的特征吸收峰,同时还存在与Ce⁴⁺离子相关的电荷迁移带. 对晶体的真空紫外-紫外激发发射光谱进行研究发现,在晶体存在着Ce³⁺离子的5d→4f辐射跃迁发光与Gd³⁺离子的4f→4f辐射跃迁发光,而且存在着Gd³⁺→Ce³⁺之间的能量传递. 对Li₆Gd(BO₃)₃:Ce晶体的X射线与γ射线激发发射光谱研究可知,晶体在高能射线激发下的闪烁光主要是Ce³⁺离子的发光. 关键词： 6Gd(BO₃)₃:Ce晶体')" href="#">Li₆Gd(BO₃)₃:Ce晶体 真空紫外-紫外透过光谱 真空紫外-紫外激发发射光谱 能量传递     

发光二极管用SrWO4:Eu3+红光荧光粉激发谱强度的调控

采用化学共沉淀法制备了Eu³⁺掺杂摩尔分数不同、煅烧温度不同的SrWO₄:Eu³⁺系列发光粉体, 所制备的粉体均具有Eu³⁺特征的强室温红光荧光发射. 通过调节煅烧温度和掺杂摩尔分数来调控近紫外和蓝光吸收强度, 进而调控用395 nm的近紫外光和465 nm的蓝光激发样品所得红光发光强度. 研究结果表明, 所制备的SrWO₄:Eu³⁺红光荧光粉可以被紫外和蓝光发光二极管有效激 关键词： 稀土掺杂 4:Eu³⁺')" href="#">SrWO₄:Eu³⁺ 光致发光 白光发光二极管     

Prediction of the magnetotoroidic effect from atomistic simulations

An effective Hamiltonian technique is used to investigate the effect of applying curled electric fields on physical properties of stress-free BiFeO(3) dots being under open-circuit electrical boundary conditions. It is discovered that such fields can lead to a control of not only the magnitude but also the direction of the magnetization. Such control originates from the field-induced transformation or switching of electrical vortices and their couplings with oxygen octahedral tilts and magnetic dipoles. This control involves striking intermediate states and constitutes a novel phenomenon that can be termed a "magnetotoroidic" effect.     

Effects of copper and oxygen vacancies on the ferromagnetism of Mn- and Co-doped Cu2O

The ferromagnetic properties of Mn- and Co-doped Cu₂O with copper and oxygen vacancies (V_Cu and V_O) are studied by first-principles calculations. The results indicate that Mn-doped Cu₂O has an antiferromagnetic state in the near configuration, while it has a ferromagnetic state for the far configuration. On the contrary, Co-doped Cu₂O possess a ferromagnetic state regardless of the distance between the two Co atoms. The observed ferromagnetism can be attributed to the 90° ferromagnetic super-exchange mechanism. The presence of V_O can enhance the ferromagnetism, whereas V_Cudepresses it.     

Real-time holography in ruthenium-doped bismuth sillenite crystals at 1064 nm

Real-time holographic recording and an improvement of the response time in ruthenium (Ru)-doped Bi(12)SiO(20) (BSO) crystal at 1064 nm is obtained. Using green light pre-exposure, a significant operation speed of 60 ms is achieved. In addition, the ability for image reconstruction is demonstrated in Ru-doped BSO, supporting further applications as reversible media for real-time image processing at the near-IR spectral range.     

Experimental demonstration of super quasi-phase matching in nonlinear photonic crystal

We have demonstrated super quasi-phase matching (QPM) in a super periodically poled lithium niobate (PPLN), which is composed of multiple ordinary PPLN cells. When super QPM is achieved, the slight phase mismatch in each PPLN cell can be further compensated for, and the relevant second harmonic generation is facilitated greatly. This mechanism provides an insightful means to relieve the limitation imposed by sample fabrication inaccuracy and will open up a promising avenue toward highly efficient nonlinear interactions.     

Density functional study of TaSin (n = 1-3, 12) clusters adsorbed to graphene surface

A plane-wave density functional theory (DFT) calculations have been performed to investigate structural and electronic properties of TaSi_n (n = 1-3, 12) clusters supported by graphene surface. The resulting adsorption structures are described and discussed in terms of stability, bonding, and electron transfer between the cluster and the graphene. The TaSi_n clusters on graphene surface favor their free-standing ground-state structures. Especially in the cases of the linear TaSi₂ and the planar TaSi₃, the graphene surface may catalyze the transition of the TaSi_n clusters from an isomer of lower dimensionality into the ground-state structure. The adsorption site and configuration of TaSi_n on graphene surface are dominated by the interaction between Ta atom and graphene. Ta atom prefers to adsorb on the hollow site of graphene, and Si atoms tend to locate on the bridge site. Further, the electron transfer is found to proceed from the cluster to the surface for n = 1 and 2, while its direction reverses as n > 2. For the case of TaSi, chemisorption is shown to prevail over physisorption as the dominant mode of surface-adsorbate interaction by charge density analysis.     

Surface adhesion properties of graphene and graphene oxide studied by colloid-probe atomic force microscopy

Surface adhesion properties are important to various applications of graphene-based materials. Atomic force microscopy is powerful to study the adhesion properties of samples by measuring the forces on the colloidal sphere tip as it approaches and retracts from the surface. In this paper we have measured the adhesion force between the colloid probe and the surface of graphene (graphene oxide) nanosheet. The results revealed that the adhesion force on graphene and graphene oxide surface were 66.3 and 170.6 nN, respectively. It was found the adhesion force was mainly determined by the water meniscus, which was related to the surface contact angle of samples.