时  间：   2016年12月1日（星期4）下午3:00
地  点：   中心教学楼610
报告一：硕士生报告    时间：15:10-15:40
题  目：Structure and optical properties of TM doped GaN nanowires
报告人：  杨欣欣            指导老师：邹炳锁
摘要：Diluted magnetic semiconductors (DMSs) which perform their semiconducting and magneticproperties, have promising applications in the field of spintronics, spin field-effect transistors and many other spin-based devices. However, Many material of ferromagnetic DMS researched nowadays have low Curie temperature and the behavior of magnetism impurity transition metal(TM) ions in DMSs is not yet well understood. The Mn doped GaN nanowires, containing Mn below 1% catalyzed by Au particles have been synthesized by means of a chemical vapor deposition method on Si substrate. The nanowires are characterized by scanning electron microscopy, Raman and photoluminescence. The growth mechanism of crystalline GaN nanowires is discussed briefly. The Mn doped GaN nanowires show two emission bands with a well-defined PL peak at 375 nm and 500-700 nm respectively. The large distinct redshift (375 nm) are comparable to pure GaN(370 nm) at room temperature. The red-shift photoluminescence is due to Mn doping. The magnetic properties discussion indicates that Mn doped GaN nanowires exhibit ferromagnetism above room temperature. In order to illustrate the optical properties of TM-doped GaN nanowires, power , temperature and polarization dependent Raman have been carried out. The result show the peak of Raman with increasing  power or temperature have large shift, due to the exchange interaction of exciton and magnetic ion spins.

 

报告二：硕士生报告    时间：15:40-16:10
题  目：二维双孔颗粒流的流量与孔间距的非线性依赖关系 
报告人：   王飞梁                      指导老师：郑宁
摘要：颗粒流指的是颗粒物质在外部作用和内部应力状态变化时发生的类似于流体的运动状态。在工业上，多孔漏斗流在颗粒材料输运，混合分离等方面具有广泛的应用。在实验研究上，二维多孔颗粒流更易于观察和分析，是三维多孔颗粒流的研究基础。我们设计了可以调节孔洞性质的二维双孔实验体系，在保证连续颗粒流的前提下，固定孔洞的直径，改变两个孔洞之间的距离，测量颗粒流出孔洞的流量。我们发现颗粒流出孔洞的平均流量随着孔洞间距的增大而下降，变化趋势呈现非线性的关系，这说明孔间的关联对颗粒流量有着明显的影响。随着孔间距的增大，流量下降的趋势逐渐变慢直至平稳。此外，我们还测量了颗粒流动过程中孔洞上方颗粒的密度分布和颗粒流速，定性上建立了其与流量变化之间的联系。