Investigation of surface topology of printed nanoparticle layers using wide-angle low-Q scattering

A new small-angle scattering technique in reflection geometry is described which enables a topological study of rough surfaces. This is achieved by using long-wavelength soft X-rays which are scattered at wide angles but in the low-Q range normally associated with small-angle scattering. The use of nanometre-wavelength radiation restricts the penetration to a thin surface layer which follows the topology of the surface, while moving the scattered beam to wider angles preventing shadowing by the surface features. The technique is, however, only applicable to rough surfaces for which there is no specular reflection, so that only the scattered beam was detected by the detector. As an example, a study of the surfaces of rough layers of silicon produced by the deposition of nanoparticles by blade-coating is presented. The surfaces of the blade-coated layers have rough features of the order of several micrometers. Using 2 nm and 13 nm X-rays scattered at angular ranges of 5° ≤ θ ≤ 51° and 5° ≤ θ ≤ 45°, respectively, a combined range of scattering vector of 0.00842 Å⁻¹ ≤ Q ≤ 0.4883 Å⁻¹ was obtained. Comparison with previous transmission SAXS and USAXS studies of the same materials indicates that the new method does probe the surface topology rather than the internal microstructure.