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排序方式: 共有136条查询结果,搜索用时 397 毫秒
11.
12.
O. Lefeuvre W. Pang P. Zinin J. D. Comins A. G. Every G. A. D. Briggs B. D. Zeller G. E. Thompson 《Thin solid films》1999,350(1-2):53-58
The surface wave dispersion for a barrier oxide film on aluminium has been determined from surface Brillouin scattering measurements carried out on films of thicknesses of 0.2, 0.35 and 0.45 μm. The measured velocities of the generalised Rayleigh mode, the pseudo interfacial mode and of several Lamb modes conform to simulations performed for stiffening layers [1]. The longitudinal velocity and the shear velocity of the layer have been calculated from the experimental dispersion curve. 相似文献
13.
First-principles calculations are performed to investigate dynamical and dielectric properties of group-III-nitrides. We focus
on vibrational frequencies, dynamical charges, and the phonon density of states of cubic AlN, GaN, and InN. Chemical trends
are derived and discussed. The first ab initio calculations of phonon branches and density of states are presented for an
ordered InxGa1−xN structure. 相似文献
14.
M. Fadel M. Rieger J. C. Vaissiere J. P. Nougier P. Kocevar 《Solid-state electronics》1989,32(12):1229-1233
A novel numerical method is developed for solving the steady-state hot electron — hot LO phonon coupled Boltzmann equations. It combines a least-square matrix and an iterative technique for getting the distribution functions of the electrons and of the LO phonons and associated average values. Between 2 and 5 kV/cm in GaAs at T=300 K, the phonon distribution is significantly disturbed from thermal equilibrium, and in turn this disturbance induces a significant deviation of the hot electron distribution from its standard shape obtained assuming phonons at thermal equilibrium. The ohmic mobility and the peak velocity are shifted by 15%. This method proves to be much more accurate than previous ones. 相似文献
15.
16.
Kihong Lee Sebastian F. Maehrlein Xinjue Zhong Daniele Meggiolaro Jake C. Russell Douglas A. Reed Bonnie Choi Filippo De Angelis Xavier Roy Xiaoyang Zhu 《Advanced materials (Deerfield Beach, Fla.)》2019,31(36)
The coupling of phonons to electrons and other phonons plays a defining role in material properties, such as charge and energy transport, light emission, and superconductivity. In atomic solids, phonons are delocalized over the 3D lattice, in contrast to molecular solids where localized vibrations dominate. Here, a hierarchical semiconductor that expands the phonon space by combining localized 0D modes with delocalized 2D and 3D modes is described. This material consists of superatomic building blocks (Re6Se8) covalently linked into 2D sheets that are stacked into a layered van der Waals lattice. Using transient reflectance spectroscopy, three types of coherent phonons are identified: localized 0D breathing modes of isolated superatom, 2D synchronized twisting of superatoms in layers, and 3D acoustic interlayer deformation. These phonons are coupled to the electronic degrees of freedom to varying extents. The presence of local phonon modes in an extended crystal opens the door to controlling material properties from hierarchical phonon engineering. 相似文献
17.
Houk Jang Krishna P. Dhakal Kyung‐Il Joo Won Seok Yun Sachin M. Shinde Xiang Chen Soon Moon Jeong Suk Woo Lee Zonghoon Lee JaeDong Lee Jong‐Hyun Ahn Hyunmin Kim 《Advanced materials (Deerfield Beach, Fla.)》2018,30(14)
Understanding the collaborative behaviors of the excitons and phonons that result from light–matter interactions is important for interpreting and optimizing the underlying fundamental physics at work in devices made from atomically thin materials. In this study, the generation of exciton‐coupled phonon vibration from molybdenum disulfide (MoS2) nanosheets in a pre‐excitonic resonance condition is reported. A strong rise‐to‐decay profile for the transient second‐harmonic generation (TSHG) of the probe pulse is achieved by applying substantial (20%) beam polarization normal to the nanosheet plane, and tuning the wavelength of the pump beam to the absorption of the A‐exciton. The time‐dependent TSHG signals clearly exhibit acoustic phonon generation at vibration modes below 10 cm?1 (close to the Γ point) after the photoinduced energy is transferred from exciton to phonon in a nonradiative fashion. Interestingly, by observing the TSHG signal oscillation period from MoS2 samples of varying thicknesses, the speed of the supersonic waves generated in the out‐of‐plane direction (Mach 8.6) is generated. Additionally, TSHG microscopy reveals critical information about the phase and amplitude of the acoustic phonons from different edge chiralities (armchair and zigzag) of the MoS2 monolayers. This suggests that the technique could be used more broadly to study ultrafast physics and chemistry in low‐dimensional materials and their hybrids with ultrahigh fidelity. 相似文献
18.
Carrier Dynamics: Transient SHG Imaging on Ultrafast Carrier Dynamics of MoS2 Nanosheets (Adv. Mater. 14/2018)
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19.
Soumya Sarkar Sreetosh Goswami Maxim Trushin Surajit Saha Majid Panahandeh‐Fard Saurav Prakash Sherman Jun Rong Tan Mary Scott Kian Ping Loh Shaffique Adam Sinu Mathew Thirumalai Venkatesan 《Advanced materials (Deerfield Beach, Fla.)》2019,31(41)
The reduced electrical screening in 2D materials provides an ideal platform for realization of exotic quasiparticles, that are robust and whose functionalities can be exploited for future electronic, optoelectronic, and valleytronic applications. Recent examples include an interlayer exciton, where an electron from one layer binds with a hole from another, and a Holstein polaron, formed by an electron dressed by a sea of phonons. Here, a new quasiparticle is reported, “polaronic trion” in a heterostructure of MoS2/SrTiO3 (STO). This emerges as the Fröhlich bound state of the trion in the atomically thin monolayer of MoS2 and the very unique low energy soft phonon mode (≤7 meV, which is temperature and field tunable) in the quantum paraelectric substrate STO, arising below its structural antiferrodistortive (AFD) phase transition temperature. This dressing of the trion with soft phonons manifests in an anomalous temperature dependence of photoluminescence emission leading to a huge enhancement of the trion binding energy (≈70 meV). The soft phonons in STO are sensitive to electric field, which enables field control of the interfacial trion–phonon coupling and resultant polaronic trion binding energy. Polaronic trions could provide a platform to realize quasiparticle‐based tunable optoelectronic applications driven by many body effects. 相似文献
20.
We generalize the Landau Pekar theory of polarons by taking account of the screening of the Coulomb interactions, and of the coupling of the electrons with the acoustical phonons. We give a criterium of existence of polarons in the presence of screening. This criterium is probably not satisfied in metals, but it can be in anisotropic materials like the cuprates. Moreover, the composite polarons may attract each other at large distance. Finally, the screening lowers significantly the effective mass of the polarons. 相似文献