Surface states metal-induced

For the more accurate description of the Mott-Schottky dependences of semiconductor electrodes modified with small metal particles, it is reasonable to take into account the contribution of the capacity of electronic surface states (C ) induced by the... 

Interface states played a key role in the development of transistors. The initial experiments at Bell Laboratories were on metal/insulator/semiconductor (MIS) stmctures in which the intent was to modulate the conductance of a germanium layer by applying a voltage to the metal plate. However, only - 10% of the induced charges were effective in charging the conductance (3). It was proposed (2) that the ineffective induced charges were trapped in surface states. Subsequent experiments on surface states led to the discovery of the point-contact transistor in 1948 (4). 

Kolb and Franke have demonstrated how surface reconstruction phenomena can be studied in situ with the help of potential-induced surface states using electroreflectance (ER) spectroscopy.449,488,543,544 The optical properties of reconstructed and unreconstructed Au(100) have been found to be remarkably different. In recent model calculations it was shown that the accumulation of negative charges at a metal surface favors surface reconstruction because the increased sp-electron density at the surface gives rise to an increased compressive stress between surface atoms, forcing them into a densely packed structure.532... 

From the above reasoning one could expect that the pre-deposition of small amounts of noble metals on the Ti02 surface in a form of the intermediate sub-layer, which can induce the electroactive electronic surface states in the Ti02 band gap, may enhance the electrocatalytic effect of subsequently deposited Cu particles. Actually, the photocatalytic deposition of silver particles in amount of 5xl014 atoms/cm-2, which on its own only slightly increases the electrocatalytic activity of Ti02 electrode, leads to 2-3-fold enhancement of the electrocatalytic activity of Cu particles subsequently deposited in a relatively high concentration (1016-1017 atoms/cm 2) [52],... 

This mcclianism is not so efrcctivc in polar semiconductors. The conversion of empty hybrids to doubly occupied hybrids on a GaAs surface would require the double occupation of a gallium hybrid, which is unfavorable because of the polar energy. Indeed, recent experiments (Chye, Babalola, Sukegawa, and Spicer, 1975) indicate that the I crmi level is not pinned on surfaces of GaP at the vacuum. Nonetheless, Schottky barriers can arise at GaP- metal interfaces. Metal-induced surface states" have been proposed as a mechanism (discussed in Section 18-1 ) but the barriers could well arise simply from incorporation of metal atoms in the semiconductor or vice versa. 

J.-N. Chazalviel and M. Stefenel, Surface states induced by metal atoms at the Si/electrolyte interface, Surf. Sci. 134, 865, 1983. 

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