Si(111)-Pt interface at room temperature: A synchrotron radiation photoemission study

Abstract

We present extensive results on synchrotron-radiation angle-integrated photoemission from Si(111)surfaces onto which increasing amounts of Pt (coverages 8 from 0.07 to 40 monolayers) were deposited. Both core lines (Si 2p and Pt4f) and valence-band states have been measured. In the latter case we present results taken at a photon energy of h v=80 eV where the Pt Sd contribution is dominant and at h v=130 eV where the Cooper minimum effect reduces the Pt 5d photoemission considerably so that information on the Si contribution to the valence states can be revealed. We show that submonolayer coverages (8 & 0.07) of Pt disrupt the surface sufficiently to introduce considerable changes in the photoemission spectra with respect to that of clean Si(111). An interface with a photoemission spectrum resembling that of a silicide has developed at about 2 -10 monolayers. At increasing 8 the region explored with photoemission shows enrichment of the metal, but the situation at 8=40 is still very far from that of the pure Pt metal, thus indicating a very strong chemical interaction at room temperature on the depth scale of tens of monolayers. Opposite chemical shifts of the Si and Pt core lines are seen (Pt towards lower and Si. towards higher binding energies with increasing 8) and, moreover, the shape of the Si 2p core lines is modified towards that typical of a metallic phase. All these results are discussed in terms of the nature of the chemical bond between Si and Pt.

Investigation of the structure and stability of the Pt/SiC(001) interface

“…This agrees with previous results obtained for Pt/Si at higher resolution, e.g., 0.5 eV (Ref. 9), indicating that any chemical shifts are smaller than the relevant line widths and changes in band bending. In the valence region, changes were observed with Pt coverage and annealing, but the limited resolution available did not permit meaningful interpretation.…”

“…5 ' 9 The Pt layer is reported to grow uniformly up to about one monolayer 4 ' 5 (© = 1) beyond which intermixing occurs, leading to a structurally and chemically inhomogeneous layer the exact nature of which is uncertain. 4 ' 10 Most of the Pt appears to remain unreacted, 4 ' 8 although evidence for Si-Pt bonding is observed in the Si LVV line shape 8 and the Si 2p, Pt 4/ and valence band photoemission, 9 and features characteristic of PtSi appear in the Raman spectrum. 7 Clustering of the Pt into three-dimensional islands 8 may also influence the structure of the interface for coverages of a few monolayers.…”

Low-temperature formation of platinum silicides on polycrystalline silicon

“…It was obtained, that the layer formed after Pt deposition without annealing consists mainly of Pt 3 Si, and in lesser degree, of Pt 2 Si compounds. This is consistent with our previous data [16] as well as the results of the works on interaction of very thin platinum films with the surface of single-crystalline silicon [31,32]. Changes in the valence band of the platinum layer structure dependent on its thickness, studied by ultraviolet photoelectron spectroscopy at the liquid nitrogen temperature [31] and with synchrotron radiation at the room temperature [32], indicate the presence of the strong interaction between Si and Pt atoms, migrating beneath the surface of a Si single crystal.…”

ESCA and Photoelectrochemical Studies of p‐n Junction Silicon Electrodes Protected by Platinum Deposition for Use in Solar Energy Conversion

“…PtSi on Si is stable at temperatures below 700~ (18). The formation of a Pt-Si intermixed layer in nonannealed samples is also reported (19).…”