Interaction of oxygen with silicon d-metal interfaces: A photoemission investigation

Abstract

We have carried out synchrotron radiation measurements both from valence states and core levels from Si(111)–Cu, Si(111)–Ag, Si(111)–Au, Si(111)–Pd interfaces before and after exposure at room temperature to 30×106 L of oxygen and we compare the results with those for the oxidation of Si(111). In all cases the oxygen interacts with Si and not with the metal, and the Si reaction rate is strongly increased with respect to that of Si(111). The strongest oxidation enhancement is obtained with Cu and Pd. In the noble metal case the interaction with oxygen produces the overgrowth of a SiO2-like phase having a Si 2 p chemical shift of ∠3.8 eV as opposite to Si(111) which cannot be oxidized to SiO2 in these conditions. Moreover, in the Si–Pd case the oxidation number is lower and the chemical shift is ∠2.3 eV. We discuss the relevance of the results both in terms of the structure of the interface and of the nature of the chemical interaction between Si and d metals.

Low temperature catalytic formation of Si-based metal–oxide–semiconductor structure

“…It is clearly seen that the silicon oxide layer is present between the Si substrate and the Pt overlayer, but not on the Pt layer, in contrast to the case of noble metal or transition metal-promoted oxidation of Si. [8][9][10] The oxide thickness is 4-4.5 nm, which is in good agreement with that estimated from the XPS spectrum ͓spectrum ͑c͒ in Fig. 1͔.…”

“…In the case of noble metal or transition metal-promoted oxidation of Si, silicon oxide layers are formed on the metal surfaces, [8][9][10] and hence the moving species through the metal layer is Si atoms ͑or Si ions͒. In that case, the Si outdiffusion is promoted by the interaction of Si with metals.…”

“…1 One of the candidates for the method of the low temperature formation of gate oxide is metal-promoted oxidation. [2][3][4][5][6][7][8][9][10] A small amount of alkali metals such as Cs and Na deposited on Si enables the Si oxidation at room temperature, but the removal of the alkali metals, which greatly degrade the electrical characteristics of the devices, requires the moderate temperature heating at around 600°C. [2][3][4][5] Moreover, secondary ion mass spectroscopy and Hall effect measurements 11 show that alkali metal atoms with the amount in the range of 10 18 cm Ϫ3 are present after the heat treatment, which is much more than that acceptable for MOS devices.…”

“…The oxidation of Si is also promoted by depositing noble metals or transition metals. [8][9][10] In this case, outdiffusion of Si atoms is enhanced by the presence of the metals. Consequently, a silicon oxide layer is formed on the metal overlayer, [8][9][10] and thus this method is not applicable to MOS technology.…”

Density functional theory studies of submonolayer oxidized silicon structures on Pd(111) and Pt(111)

“…A study of the adsorption of oxygen on Pd(1 0 0) determined that Si impurities in the Pd crystal led to irreversible oxygen adsorption and the formation of a Si-stabilized surface oxide [7]. Other investigations have shown that Si oxidation is enhanced in the presence of Ni, Pt and Pd silicide films on Si, which is mainly attributed to the lower barrier for dissociation of O 2 on the metal atoms [11][12][13][14][15][16]. The oxidation of Si on these surfaces is not complete, and an intermediate oxidation state of Si is found on the surface, described in the literature as an SiO X layer.…”