Semiconductor surface phonon

Esser, N. (1999) Analysis of semiconductor surface phonons by Raman spectroscopy. Appl. Phys. A, 69, 507. 

Cardona M, Giintherodt G (eds) (2000) Light scattering in solids VIII fullerenes, semiconductor surfaces, coherent phonons, vol 76, Topics in applied physics. Springer, Berlin... 

Electron work function of metals and semiconductors Electron binding energy of metals and semiconductors Surface free energy and surface stress Surface phonon dispersion Surface optical properties... 

Phonon surface bands of some insulators and semiconductors are given in Figs. 5.2-56-5.2-58. Surface phonon energies of alkali halide crytals are summarized in Table 5.2-23. Since insulators and semiconductors have in general more than one atom per unit cell, they display both acoustical and optical branches. Surface Debye temperatures of some semiconductors are given in Table 5.2-22. 

YN Hwang, SH Park, D Kim. Size-dependent surface phonon mode of CdSe quantum dots. Size dependence of electron-phonon coupling in semiconductor nanospheres—The case of CdSe. Phys Rev B 59 7285-7288, 1999. 

The specific character of properties, demonstrated by nanoccmiposites is determined by the small size (units of nanometers) of filler partides, comparable with the wavelength of electron, which leads to the so called quantum size effects and the essential ratio of surface to volume in such systems, which increases the role of particle surface and interfaces between particle and polymer media (e.g., in a SO A CdS partide, about 15% of the atoms are on the surface). The latter fact is the reason for the higher chemical activity of nanoparticles and the increase in the role of such surface excitations as surface plasmons in small metal particles and spedfic surface phonon modes both as the increadng role surface states, espedally surface traps in semiconductor nanopartides. 

Figure 3.4 shows the dispersion curve of a surface phonon poiariton. If the considered frequency range contains several optical phonon modes, Eq. (3.96) must be generalized to a sum over them. Another complication arises when the plasma frequency in a doped semiconductor crystal has the same order of magnitude as the optical phonon frequencies. Then one has to add into Eq. (3.96) the contribution of conduction electrons given by —cOp/co. ... 

In Section 3.3.3 we have considered surface phonon polaritons in dielectrics and semiconductors. To derive their dispersion relation we have used the dielectric function of a crystal in the form (3.96). However, for comparison with experimental data it is necessary to take into account the decay rate of phonons, F(a ), as well as their anharmonicity characterized by the frequency shift A(ur) (Mirlin 1982). The corresponding dielectric function is given by... 

Mirlin, D. (1982). Surface phonon polaritons in dielectrics and semiconductors. In Agranovich, V. and Mills, D., editors. 

The data for surface phonon dispersion determined either experimentally or theoretically for adsorbed covered systems is reported and compared with the surface phonon dispersion of the corresponding bare system. The data is organised according to the electrical properties of the material firstly metals, secondly elemental semiconductors and insulators, and finally compound semiconductors, oxides and salts. The reported systems are collected in Table I. 

Sulfur is used to passivate the Ge surface and was suggested as a prototype for the development of an intuitive picture of the chemical bond at the semiconductor surface. The structural and electronic properties were calculated within DFT-LDA for the (1x1) phase obtained at saturation (IML coverage). The adsorption site is identified with the bridge, while the substrate reverts to a nearly ideal bulk termination. The surface phonon spectrum was calculated by a total energy ansatz and is shown in... 

J. (1995) Surface phonons of hydrogen-terminated semiconductor surfaces. 1. The H-Si(lll)-(1 X1) surface. 

Many of the fiindamental physical and chemical processes at surfaces and interfaces occur on extremely fast time scales. For example, atomic and molecular motions take place on time scales as short as 100 fs, while surface electronic states may have lifetimes as short as 10 fs. With the dramatic recent advances in laser tecluiology, however, such time scales have become increasingly accessible. Surface nonlinear optics provides an attractive approach to capture such events directly in the time domain. Some examples of application of the method include probing the dynamics of melting on the time scale of phonon vibrations [82], photoisomerization of molecules [88], molecular dynamics of adsorbates [89, 90], interfacial solvent dynamics [91], transient band-flattening in semiconductors [92] and laser-induced desorption [93]. A review article discussing such time-resolved studies in metals can be found in... 

A number of solid compounds have been examined with this time-domain method since the first report of coherent phonons in GaAs [10]. Coherent phonons were created at the metal/semiconductor interface of a GaP photodiode [29] and stacked GaInP/GaAs/GalnP layers [30]. Cesium-deposited [31-33] and potassium-deposited [34] Pt surfaces were extensively studied. Manipulation of vibrational coherence was further demonstrated on Cs/Pt using pump pulse trains [35-37]. Magnetic properties were studied on Gd films [38, 39]. 

VEM excitation energy relaxati( i. Such ways (channels) be probably chemisorption with charge transfer, production of phonons, ejection of electrons from surface states and traps, and the like. The further studies in this field will, obviously, make it possible to give a more complete characteristic of the VEM interaction with the surface of solid bodies and the possibilities of VEM detecting with the aid of semiconductor sensors. 

A similar situation exists for carrier capture by surface states. Relatively large capture cross sections are observed but no adequate theoretical treatment exists. Theory to describe the capture process is greatly complicated by presence of the surface. The carrier motion as well as the vibrational behavior of the crystal is perturbed by the surface. What does seem clear, however, is that the surface state should be tightly enough bound to the crystal lattice so that phonon emission is possible. In addition, the state should be close enough to the semiconductor to overlap the wave function of the semiconductor carrier. 

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