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Gap opening and tuning in single-layer graphene with combined electric and magnetic field modulation 下载免费PDF全文
The energy band structure of single-layer graphene under one-dimensional electric and magnetic field modulation is theoretically investigated. The criterion for bandgap opening at the Dirac point is analytically derived with a two-fold degeneracy second-order perturbation method. It is shown that a direct or an indirect bandgap semiconductor could be realized in a single-layer graphene under some specific configurations of the electric and magnetic field arrangement. Due to the bandgap generated in the single-layer graphene,the Klein tunneling observed in pristine graphene is completely suppressed. 相似文献
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The variation of Mn-dopant distribution state with x and its effect on the magnetic coupling mechanism in Znl-xMnxO nanocrystals 下载免费PDF全文
Zn1-xMnxO (x = 0.0005, 0.001, 0.005, 0.01, 0.02) nanocrystals are synthesized by using a wet chemical process. The coordination environment of Mn is characterized by X-ray photoelectron spectroscopy, Raman spectroscopy, and its X-ray absorption fine structure. It is found that the solubility of substitutional Mn in a ZnO lattice is very low, which is less than 0.4%. Mn ions first dissolve into the substitutional sites in the ZnO lattice, thereby forming Mn2+O4 tetrahedral coordination when x ≤ 0.001, then entering into the interstitial sites and forming Mn3+O6 octahedral coordination when x ≥ 0.005. All the samples exhibit paramagnetic behaviors at room temperature, and antiferromagnetic coupling can be observed below 100 K. 相似文献
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We have theoretically analyzed the quasibound states in a Mraphene quantum dot (GO, D) with a magnetic flux -φ in the centre. It is shown that the two-fold time reversal degeneracy is broken and the quasibound states of GQD with positive~negative angular momentum shifted upwards/downwards with increasing the magnetic flux. The variation of the quasibound energy depends linearly on the magnetic flux, which is quite different from the parabolic relationship for SchrSdinger electrons. The GQD's quasibound states spectrum shows an obvious Aharonov-Bohm (AB) oscillations with the magnetic flux. It is also shown that the quasibound state with energy equal to the barrier height becomes a bound state completely confined in GQD. 相似文献
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宽带光放大是指在整个硅基光纤最低损耗带1.4μm~1.7μm能够获得有效信号净增益的光放大。研究高效的宽带光放大材料可以大大满足人们提高通信容量和实现光集成的要求。材料体系的研究主要集中在稀土掺杂氧化物薄膜、玻璃材料和有机聚合物材料上。着重从宽带的获得、发光性能的改善和发光机理的探索3个方面介绍了稀土掺杂玻璃和薄膜材料的研究进展。结合已经取得的结果和积累的经验,探讨了提高发光效率的方法,指出纳米结构设计的共掺材料体系可以获得有效的宽带发光。最后展望了本领域的发展前景。 相似文献
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采用高氢稀硅烷热丝化学气相沉积方法制备氢化微晶硅薄膜.其结构特征用Raman谱,红外透射谱,小角X射线散射等来表征.结果表明微晶硅的大小及在薄膜中的晶态比χc随氢稀释度的提高而增加.而从红外谱计算得到氢含量则随氢稀释度的增加而减少.小角X射线散射结果表明薄膜致密度随氢稀释度的增加而增加.结合红外谱和小角X射线散射的结果讨论与比较了不同相结构下硅网络中H的键合状态.认为随着晶化的发生和晶化程度的提高H逐渐移向晶粒表面,在硅薄膜中H的存在形式从以SiH为主向SiH2
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报道了GaAs(311)A衬底上的自组装InAs量子点的结构和光学特性.原子力量显微镜结果表明(311)A GaAs衬底上的InAs量子点呈箭头状,箭头方向沿[233]方向.实验发现,量子点的光致发光(PL)强度、峰位、半高宽都与测量温度密切相关.随着温度的升高,量子点的发光强度减小,峰位快速红移,半高宽单调下降.可以认为这是由于载流子先被热激活到浸润层势垒后再被俘获到能量较低的量子点中进行复合造成的,这一模型圆满解释了我们的实验结果.
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The variation of Mn-dopant distribution state with x and its effect on the magnetic coupling mechanism in Zn_(1-x) Mn_x O nanocrystals 下载免费PDF全文
Zn1-x Mn x O(x = 0.0005,0.001,0.005,0.01,0.02) nanocrystals are synthesized by using a wet chemical process.The coordination environment of Mn is characterized by X-ray photoelectron spectroscopy,Raman spectroscopy,and its X-ray absorption fine structure.It is found that the solubility of substitutional Mn in a ZnO lattice is very low,which is less than 0.4%.Mn ions first dissolve into the substitutional sites in the ZnO lattice,thereby forming Mn2+O4tetrahedral coordination when x ≤ 0.001,then entering into the interstitial sites and forming Mn3+O6octahedral coordination when x ≥ 0.005.All the samples exhibit paramagnetic behaviors at room temperature,and antiferromagnetic coupling can be observed below 100 K. 相似文献
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采用对非晶氧化硅薄膜退火处理方法,获得纳米晶硅与氧化硅的镶嵌结构.室温下观察到峰位为2.40eV光致发光.系统地研究了不同退火温度对薄膜的Raman谱、光荧光谱及光电子谱的影响.结果表明,荧光谱可分成两个不随温度变化的峰位为1.86和2.30eV的发光带.Si2p能级光电子谱表明与发光强度一样Si4+强度随退火温度增加而增加.Si平均晶粒大小为4.1—8.0nm,不能用量子限制模型解释蓝绿光的发射.纳米晶硅与SiO2界面或SiO2中与氧有关的缺陷可能是蓝绿光发射的主要原因
关键词: 相似文献