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Two-dimensional (2D) semiconductors, such as lead selenide (PbSe), locate at the key position of next-generation devices. However, the ultrathin PbSe is still rarely reported experimentally, particularly on metal substrates. Here, we report the ultrathin PbSe synthesized via sequential molecular beam epitaxy on Ag(111). The scanning tunneling microscopy is used to resolve the atomic structure and confirms the selective formation of ultrathin PbSe through the reaction between Ag5Se2 and Pb, as further evidenced by the theoretical calculation. It is also found that the increased accumulation of Pb leads to the improved quality of PbSe with larger and more uniform films. The detailed analysis demonstrates the bilayer structure of synthesized PbSe, which could be deemed to achieve the 2D limit. The differential conductance spectrum reveals a metallic feature of the PbSe film, indicating a certain interaction between PbSe and Ag(111). Moreover, the moiré pattern originated from the lattice mismatch between PbSe and Ag(111) is observed, and this moiré system provides the opportunity for studying physics under periodical modulation and for device applications. Our work illustrates a pathway to selectively synthesize ultrathin PbSe on metal surfaces and suggests a 2D experimental platform to explore PbSe-based opto-electronic and thermoelectric phenomena. 相似文献
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以本实验室合成的3种结构的蝌蚪型POSS杂化聚甲基丙烯酸三氟乙酯(POSS-PTFEMA)、POSS杂化聚甲基丙烯酸三氟乙酯嵌段共聚聚甲基丙烯酸甲酯(POSS-PMMA-PTFEMA)及POSS杂化聚甲基丙烯酸甲酯嵌段共聚聚甲基丙烯酸三氟乙酯为成膜材质,利用呼吸图案法制备规整结构的蜂窝状聚合物多孔薄膜.利用扫描电镜(SEM)对薄膜表观形貌进行观察,分析了孔形貌的影响因素,并研究了多孔膜的疏水疏油性和耐温性.研究表明,以氯仿为成膜溶剂,3种不同结构的杂化聚合物均可以在较大的浓度范围下(5~30 mg/mL)制备规整的杂化聚合物多孔膜,膜的孔径随聚合物浓度的增大而增大;聚合物POSS-PTFEMA由于化学结构中含有最多的TFEMA结构单元,其规整性最好;相对疏水的硅片也有利于这类疏水的聚合物多孔膜的制备.所形成的多孔膜具有良好的耐温性能和疏水拒油性,其对水接触角介于98°~116°之间,对正十二烷的接触角则介于43°~66°之间. 相似文献
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Signatures of strong interlayer coupling in γ-InSe revealed by local differential conductivity 下载免费PDF全文
Xiaoshuai Fu 《中国物理 B》2021,30(8):87306-087306
Interlayer coupling in layered semiconductors can significantly affect their optoelectronic properties. However, understanding the mechanisms behind the interlayer coupling at the atomic level is not straightforward. Here, we study modulations of the electronic structure induced by the interlayer coupling in the γ-phase of indium selenide (γ-InSe) using scanning probe techniques. We observe a strong dependence of the energy gap on the sample thickness and a small effective mass along the stacking direction, which are attributed to strong interlayer coupling. In addition, the moiré patterns observed in γ-InSe display a small band-gap variation and nearly constant local differential conductivity along the patterns. This suggests that modulation of the electronic structure induced by the moiré potential is smeared out, indicating the presence of a significant interlayer coupling. Our theoretical calculations confirm that the interlayer coupling in γ-InSe is not only of the van der Waals origin, but also exhibits some degree of hybridization between the layers. Strong interlayer coupling might play an important role in the performance of γ-InSe-based devices. 相似文献
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针对经典响应面法和加权响应面法存在的计算精度不高和稳定性不强的问题,提出一种新的样本点选择策略,即交叉降阶思想,并基于此发展出一种新的改进响应面方法。该方法以均值点加上0.5倍的标准差作为初始迭代点。在Bucher试验设计的基础之上,将n维坐标系降阶为n个一维坐标系。然后,依据样本点的重要性,筛选出n+1个靠近真实失效面的优秀样本点,并用这些样本点去拟合线性响应面函数。最后依据样本中心间的距离与上一次迭代得到的设计点的范数之商作为其收敛准则。通过5个数值算例与工程算例,验证了交叉降阶响应面法具有较高的精度、效率、稳定性和一定的工程适用性。 相似文献
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人工设计的光子学器件在现代光学的各个领域都有广阔的应用前景。传统光子学器件的设计通常是基于已知的物理模型,然后通过数值模拟方法对结构进行优化设计。由于器件结构很大程度上依赖于先验模型,所以传统优化设计的自由度是有限的。随着近年来对高性能光子学器件需求的日益增长,具有更高设计自由度的逆向设计方法得到了快速发展。逆向设计方法打破了传统方法的设计局限性,可以在全参数空间中实现高效的参数优化,因此更可能得到具有极限性能的器件结构。本文总结了光子学器件逆向设计的常用方法,并给出了逆向设计在各个光子学领域中的具体应用。随着计算机科学的不断发展,逆向设计方法展现出无与伦比的潜力,有望在各个光学领域中实现更高自由度的光场调控。 相似文献