Electron dynamics semiconductor surface states

Surface states can form due to abrupt distortion of the semiconductor crystal lattice. Charge transfer processes between surface states and the electrolyte have been analyzed in relation to water photoelectrolysis application [96]. Electron transfer mediated through surface states for an n-type semiconductor under dynamic equilibrium is shown in Fig. 3.13(d). 

Dynamics. Cluster dynamics constitutes a rich held, which focused on nuclear dynamics on the time scale of nuclear motion—for example, dissociahon dynamics [181], transihon state spectroscopy [177, 181, 182], and vibrahonal energy redistribuhon [182]. Recent developments pertained to cluster electron dynamics [183], which involved electron-hole coherence of Wannier excitons and exciton wavepacket dynamics in semiconductor clusters and quantum dots [183], ultrafast electron-surface scattering in metallic clusters [184], and the dissipahon of plasmons into compression nuclear modes in metal clusters [185]. Another interesting facet of electron dynamics focused on nanoplasma formation and response in extremely highly ionized molecular clusters coupled to an... 

Surface states were considered earlier (Sect. 1.3.4) from an electrostatic perspective. Here we examine their dynamic consequences. There are two principal charge transfer routes involving surface states. Gonsider again an n-type semiconductor the forward-bias current can either involve direct exchange of electrons between the semiconductor GB and Ox states in solution (Fig. 12b) or can be mediated by surface states (Fig. 15). The second... 

Two-photon time-resolved photoemission (TPTRP) spectroscopy has been developed to directly study the dynamics of optically excited electrons at metal and semiconductor surfaces. This technique has been applied to direct measurement of hot electron relaxation in noble and transition metals [27, 28], surface-state dynamics on clean and adsorbate-covered metal surfaces [29, 30], as well as charge carrier dynamics in semiconductors, where much work has been performed. 

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... 

In addition to the thermal bath of nuclear motions, important groups of solids— metals and semiconductors provide continua of electronic states that can dominate the dynamical behavior of adsorbed molecules. For example, the primary relaxation route of an electronically excited molecule positioned near a metal surface is electron and/or energy transfer involving the electronic degrees of freedom in the metal. In this section we briefly outline some concepts from the electronic structure of solids that are needed to understand the interactions of molecules with such environments. 

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