Caracterización de la estructura de láminas cristalinas a través de los métodos de difracción de rayos X por transmisión y por reflexión

Abstract

This degree project, conducted as an internship, addresses the conditions for the structural characterization of crystalline sheets and thin films using the X-ray diffraction (XRD) technique. The purpose consists of comparing, both theoretically and experimentally, the transmission diffraction (Laue method) and reflection diffraction methods, evaluating the feasibility and necessity of the grazing-incidence X-ray diffraction (GIXRD) technique. The methodology involved the use of a Leybold 554 800 X-ray apparatus equipped with various anodes (W, Mo, Cu) operating at 35 kV. Reference single crystals (LiF) and three configurations of titanium dioxide (TiO₂) were analyzed: thin films deposited on organic substrates (guadua), monolayer powder samples, and agglomerates (paste). The patterns obtained were interpreted using the Beer-Lambert law of attenuation and the Drude-Lorentz electrodynamic oscillator approximation. The experimental results demonstrated that the Laue method has physical limitations for the study of supported TiO₂ films. It was theoretically demonstrated that the film’s diffraction signal is masked by scattering from the organic substrate. Furthermore, it was shown that irradiating crystalline powders with the spectrum emitted by the tungsten anode induces destructive interference under Bragg conditions, making phase indexing impossible. The study concludes that, to effectively characterize thin films in the laboratory, a methodological shift toward grazing-incidence X-ray diffraction (GIXRD) is necessary to suppress substrate interference.