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GaMnN/GaN multilayers and conventional GaMnN single layers are grown by metal-organic chemical vapor deposition. Both kinds of samples show room-temperature ferromagnetism. After thermal annealing, the sample with GaMnN/GaN multilayer structure displays a larger coercivity and better thermal stability compared to the GaMnN single layer. The annealing effects on Vca related defects are observed from photoluminescenee measurements. Moreover, a different magnetic behavior is also found in the annealed GaMnN films grown on different (n-type GaN and p-type GaN) templates. These kinds of structure-dependent magnetic behaviors indicate that defects or carriers transformation introduced during annealing may have important effects on the electronic structure of Mn ions and on the ferromagnetism. Our work may be helpful for further understanding the origin of ferromagnetism in GaN-based diluted magnetic semiconductors. 相似文献
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用透射电子显微镜(TEM)和Raman散射(RS)研究了对向靶溅射法制备的Co/C软X射线多层膜在退火条件下碳的结构变化.结果表明,碳层的结构变化可大致分为三个阶段,即有序化,结晶以及晶粒生长阶段。在退火温度低于400℃时的有序化阶段,非晶碳层中键角无序的三配位键和四配位键转变为理想的三配位键。在结晶阶段,非晶碳层在500~600℃的退火温度下结晶成为石墨微晶。在晶粒生长阶段,样品在700℃以上温度退火,石墨微晶尺寸增大,与TEM分析结果相一致。 相似文献
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研究了对向靶反应溅射法制备的CoN/CN软X射线多层膜的结构稳定性。研究表明,通过掺杂N原子可以将Co/C软X射线多层膜的结构稳定性提高100~200℃.400℃温度下退火,CoN/CN多层膜的周期膨胀仅为4%,700℃时周期结构仍然存在.N掺杂可以有效抑制CN层中sp3键的形成,延迟层内结晶过程,进而减小了周期膨胀.Co-N和C-N间存在的强化学键可以减小结构弛豫.填隙N原子增大了Co原子运动的粘滞性,使hcp-Co和fcc-Co在相变温度以上共存,抑制了高温下晶粒长大. 相似文献
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研究了低温退火Co/C软X射线多层膜中掠入射反射率的增强现象.通过测量一级调制峰强度随退火温度和时间的变化,测得了低至-10-25m2s-1的有效扩散系数.由于所研究的Co/C多层膜的调制波长远大于Co-C系统的扩散临界波长,有效扩散系数近似等于真实宏观扩散系数.负的宏观扩散系数表明,在Co-C系统中有相分离的趋势.这一结果可解释为由Miedema宏观原子模型计算得到的正的Co-C系统的混合焓.高退火温度下反射率的降低是界面锐化与界面粗糙化
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