Modeling of complex surface structures for ARXPS

Abstract

Angle-resolved X-ray photoelectron spectroscopy (ARXPS) has a great potential for nondestructive depth profiling in the nanometer thickness range. A method using computer simulation of ARXPS measurements is presented, which allows systematic studies on surfaces with artificial spatial inhomogeneity in the nanometer-range. Investigations of rough surfaces with varied structure sizes show that inhomogeneous structures can be increasingly better described by homogeneous smooth layers when lowering the typical length dimensions. In parallel, the obtained effective amount of overlayer material (or effective overlayer thickness), is systematically lower than the real one. Limitations of the 'magic-angle concept' are derived. Possible improvement of the method is discussed by consideration of elastic scattering.

XPS topofactors: determining overlayer thickness on particles and fibres

“…In this case, the so-called 'magic angle' for a particular sample is provided by the relationship sec θ =< sec γ >, bearing in mind that tilting the sample may also change the right hand side of this equation in a rather complicated fashion. The 'magic angle' is clearly sample dependent, orientation dependent, as well as thickness dependent, [6] providing a partial explanation of the various reports of 30-35…”

“…X-ray shadowing effects are not accounted for and θ = 0. The values for X-ray opaque cylinders with the fibre axis orthogonal to the azimuth defined by the source are included for completeness To approximate these values we first note that the limiting value at R → ∞ is provided by Eqn (1) with the effective thickness t calculated by dividing the overlayer thickness T by the relevant Topofactor, which can be found from Eqn (6). The limiting value at R, T → 0 is provided by Eqn (8), where V i is the volume of substance i and D is the dimensionality of the object: for cylinders, D = 1, and for spheres, D = 2.…”

Electron Spectroscopy of Corrugated Solid Surfaces

“…39,40 Recent work has shown, however, that the magic angle introduced as a practical tool for reducing experimental errors induced by surface roughness in an overlayer thickness estimation is not a universal tool. 20,23,24,42,43 It depends on the type of surface roughness, the overlayer thickness value, the overlayer thickness distribution, the surface contamination, and also on electron inelastic surface excitation effects.…”

“…Oswald and Oswald 43,44,46,51 calculated the angular dependencies of the photoelectron intensities from solid surfaces with simple-shaped 3D figures of various kinds, e.g., pyramids, spheroids, islands, hollows, all covered with an overlayer. They developed a computer program for simulating the ARXPS intensities for the above-mentioned surface structures.…”

Composition depth profiling of polystyrene/poly(vinyl ethyl ether) blend thin films by angle resolved XPS

“…Angle resolved XPS (ARXPS) can also be used to investigate the CDP of a sample between ~ 1 and ~ 8 nm of the uppermost surface [19][20][21][22][23][24][25][26][27][28][29][30][31] with less sample damage than caused by ion beam sputtering. The physics of the ARXPS method has been outlined in several publications [32-Page 3 of 29 A c c e p t e d M a n u s c r i p t 3 [35] has shown how uncertainties in the intensity measurements limit the information that can be extracted from the data.…”