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Atomic force microscopy investigation of growth process of organic TCNQ aggregates on SiO2 and mica substrates 下载免费PDF全文
<正>Deposition patterns of tetracyanoquinodimethane(TCNQ) molecules on different surfaces are investigated by atomic force microscopy.A homemade physical vapour deposition system allows the better control of molecule deposition. Taking advantage of this system,we investigate TCNQ thin film growth on both SiO_2 and mica surfaces.It is found that dense island patterns form at a high deposition rate,and a unique seahorse-like pattern forms at a low deposition rate.Growth patterns on different substrates suggest that the fractal pattern formation is dominated by molecule-molecule interaction.Finally,a phenomenal "two-branch" model is proposed to simulate the growth process of the seahorse pattern. 相似文献
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We report a facile phase conversion method that can locally convert n-type SnSe2 into p-type SnSe by direct laser irradiation. Raman spectra of SnSe2 flakes before and after laser irradiation confirm the phase conversion of SnSe2 to SnSe. By performing the laser irradiation on SnSe2 flakes at different temperatures, it is found that laser heating effect induces the removal of Se atoms from SnSe2 and results in the phase conversion of SnSe2 to SnSe. Lattice-revolved transmission electron microscope images of SnSe2 flakes before and after laser irradiation further confirm such conversion. By selective laser irradiation on SnSe2 flakes, a pattern with SnSe2/SnSe heteostructures is created. This indicates that the laser induced phase conversion technique has relatively high spatial resolution and enables the creation of micron-sized in-plane p-n junction at predefined region. 相似文献
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Dirac states from p_(x,y) orbitals in the buckled honeycomb structures:A tight-binding model and first-principles combined study 下载免费PDF全文
Dirac states composed of p_(x,y) orbitals have been reported in many two-dimensional(2 D) systems with honeycomb lattices recently. Their potential importance has aroused strong interest in a comprehensive understanding of such states.Here, we construct a four-band tight-binding model for the p_(x,y)-orbital Dirac states considering both the nearest neighbor hopping interactions and the lattice-buckling effect. We find that p_(x,y)-orbital Dirac states are accompanied with two additional narrow bands that are flat in the limit of vanishing π bonding, which is in agreement with previous studies. Most importantly, we analytically obtain the linear dispersion relationship between energy and momentum vector near the Dirac cone. We find that the Fermi velocity is determined not only by the hopping through π bonding but also by the hopping through σ bonding of p_(x,y) orbitals, which is in contrast to the case of p_z-orbital Dirac states. Consequently, p_(x,y)-orbital Dirac states offer more flexible engineering, with the Fermi velocity being more sensitive to the changes of lattice constants and buckling angles, if strain is exerted. We further validate our tight-binding scheme by direct first-principles calculations of model-materials including hydrogenated monolayer Bi and Sb honeycomb lattices. Our work provides a more in-depth understanding of p_(x,y)-orbital Dirac states in honeycomb lattices, which is useful for the applications of this family of materials in nanoelectronics. 相似文献
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Intrinsic charge transport behaviors in graphene-black phosphorus van der Waals heterojunction devices 下载免费PDF全文
Heterostructures from mechanically-assembled stacks of two-dimensional materials allow for versatile electronic device applications. Here, we demonstrate the intrinsic charge transport behaviors in graphene-black phosphorus heterojunction devices under different charge carrier densities and temperature regimes. At high carrier densities or in the ON state,tunneling through the Schottky barrier at the interface between graphene and black phosphorus dominates at low temperatures. With temperature increasing, the Schottky barrier at the interface is vanishing, and the channel current starts to decrease with increasing temperature, behaving like a metal. While at low carrier densities or in the OFF state, thermal emission over the Schottky barrier at the interface dominates the carriers transport process. A barrier height of ~67.3 meV can be extracted from the thermal emission-diffusion theory. 相似文献
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文章介绍了一种非模板选择性自组装纳米结构的方法.从实验和理论上研究了两种有机分子在Ag单晶不同表面上的吸附行为,发现在Ag(775)基底上PTCDA分子会完全吸附在(111)台阶面上,而DMe-DCNQI分子则完全吸附在(221)台阶面上.该研究还阐明了PTCDA分子与基底原子之间的相互作用机制,提出了PTCDA与基底之间的相互作用是通过分子末端官能团的氧原子实现的,中心的π共轭区域与基底相排斥,理论模拟得到的氧原子的NIXSW相干长度以及碳原子的近边X射线吸收谱与实验结果符合得较好. 相似文献