P. Jussila

Instrumentation and analytical methods of an x-ray photoelectron spectroscopy–scanning tunneling microscopy surface analysis system for studying nanostructured materials

The design and performance of an x-ray photoelectron spectroscopy (XPS)–scanning tunneling microscopy (STM) surface analysis system for studying nanostructured materials are described. The analysis system features electron spectroscopy methods (XPS and Auger electron spectroscopy) in addition to a variable temperature STM. With the analytical methods of the system, surface chemical analysis as well as surface morphology down to atomic resolution can be obtained. The system also provides facilities for sample cleaning, annealing, gas dosing, depth profiling, and surface modifications by sputtering and evaporation. Controlled gas exposures from ultrahigh vacuum to atmospheric pressures in the adjustable temperature range of 120–1100K can be carried out in different chambers. A fast entry air lock allows the transfer of samples and STM tips into the system without air exposures. The surface analysis system uses a common sample holder in all five chambers which are independently pumped and separated from each...

Substrate-induced effects in the creation and decay of potassium 2p core excitations in ultrathin films of KCl on copper

Substrate-induced effects on the transport properties in thin KCl films on the Cu(100) surface have been studied using K + 2p photoelectron, photoabsorption and resonant Auger spectra. The measurements were performed at different KCl coverages ranging from a partial monolayer to a thick bulk-like film. The morphology and layer thickness were estimated from an analysis of the electron energy loss structure of the K + 2p and Cl − 2p photoelectron peaks, and from the variations in the photoelectron peak fine structure. The resonant Auger spectator decay spectra measured at the photoabsorption resonances show that the significant differences between the spectra of the solid and of thin layers are related to the charge delocalization from the K + 3d excited state into the metal substrate. The core-hole-clock approach yields an estimate of 1.5 fs for the corresponding charge transfer time at a single monolayer KCl coverage. (Some figures in this article are in colour only in the electronic version)

Ag/Cu(100) Surface Alloy and Polycrystalline Cu(Ag) Alloy Studied by XPS

In this work, polycrystalline Cu(Ag) bulk alloy (1 wt.% Ag) and Ag/Cu(100) surface alloy (0.9 ML Ag) have been characterized by x-ray photoelectron spectroscopy (XPS) employing Al Kα and Mg Kα radiation. XPS spectra of the principal core levels (Cu, Ag) are presented together with XAES (x-ray induced Auger electron spectroscopy) spectra of the Cu LMM transition. The samples were prepared in situ by argon ion sputtering at room temperature and subsequent annealing at 700 K. Ag overlayer was deposited on the Cu(100) surface by a resistively heated Ag evaporator. The absence of contaminants such as C or O was confirmed by XPS. Together, the industrial Cu(Ag) alloy and the well defined Ag/Cu(100) model system serve as a template for studies of nanoscale surface oxidation and segregation phenomena.