Time-resolved in situ investigations of reactive sputtering processes by grazing incidence X-ray absorption spectroscopy

Abstract

Abstract:We have applied the time-resolved grazing incidence X-ray absorption fine structure technique to study in-situ the atomic short range order and the electronic structure of reactively sputter deposited thin films. Results obtained during the reactive deposition of amorphous Ta-pentoxide thin films deposited in oxygen containing atmospheres will be presented. A new calculation scheme for a detailed reflection mode EXAFS data analysis giving bond distances, coordination numbers and Debye-Waller factors is presented. The atomic short range structure of the amorphous Ta 2 O 5 thin films is compared to that of crystalline β-Ta 2 O 5 .

T-REX: new software for advanced QEXAFS data analysis

“…Various experiments have proven that using QEXAFS in grazing-incidence mode close to the total reflection is a promising approach to gain new insights in the in situ deposition of and reactions on thin films with second time resolution (Frahm et al, 1991;Lü tzenkirchen-Hecht & Frahm, 2005b, 2006 and recently also sub-second time resolution as demonstrated here. Owing to the close relationship between reflection and absorption data by means of the Kramers-Kronig relation, the full EXAFS information is also included in the reflectivity spectra.…”

“…Nowadays, QEXAFS instrumentation allows the collection of full EXAFS spectra in milliseconds continuously over several hours (Frahm et al, 2005(Frahm et al, , 2010Uruga et al, 2007;Khalid et al, 2010;. Invaluable scientific opportunities are the result, as structural and electronic changes during various processes in physics (Frahm et al, 1992;Schroer et al, 2003;Lü tzenkirchen-Hecht & Frahm, 2006), chemistry (Briois et al, 2005;Okumura et al, 2008;Fujimori et al, 2009;Bauer et al, 2010) and biology (Ascone et al, 2003;Haumann et al, 2005) can be studied. It is thus not surprising that QEXAFS becomes more and more a standard tool in materials science, especially in the context of catalysis research (Clausen et al, 1998;Grunwaldt et al, 2001;Dent, 2002;Bando et al, 2009;Silversmit et al, 2009;Reimann et al, 2011;Fö ttinger et al, 2011;Rochet et al, 2011).…”

Surface-sensitive reflection-mode EXAFS from layered sample systems: the influence of surface and interface roughness

“…Owing to the calculation procedure, these simulated reflectivity spectra R(E, Â) contain the near-range order structural information of the chosen model compounds, either by a direct input of structural parameters and an ab initio calculation of the refractive index (Lü tzenkirchen- Hecht & Frahm, 2006;Benzi et al, 2008) or by using spectra of suited reference compounds (Borthen & Strehblow, 1997;Lü tzenkirchen-Hecht et al, 2003). Here we have used high-quality transmission-mode XAS data which were obtained from polycrystalline reference materials (metal foils, oxide powders) at beamlines RÖ MO 2 and BW1 at HASYLAB (DESY, Hamburg, Germany) operating with 100-150 mA of 4.45 GeV positrons.…”

“…Grazing-incidence reflection-mode X-ray absorption spectroscopy is a valuable method for obtaining structural information about the near surface region surfaces and thin films, and has proven to be useful for many different research areas such as oxidation by gases and liquids (Bosio et al, 1988;Cortes et al, 1990;Borthen & Strehblow, 1993;Gibson & Crabb, 1995;, corrosion (Lü tzenkirchen- Hecht & Frahm, 2005), thin film growth (Charnock et al, 1995;d'Acapito et al, 2002d'Acapito et al, , 2004Lü tzenkirchen-Hecht & Frahm, 2006), materials synthesis (Cheong et al, 2001), battery charge and discharge investigations (Lü tzenkirchen- Hecht et al, 2003;Wagemaker et al, 2004) etc. Grazing-incidence X-ray absorption spectroscopy detection techniques currently also include total electron yield (Zheng et al, 1997), fluorescence (Heald et al, 1988), diffusely scattered light (Keil et al, 2005a) and the intensity of Bragg rods (Grenier et al, 2001;Luo et al, 2001).…”

“…However, such an extraction is in general not possible for thin film sample systems with layer thicknesses smaller than the X-ray penetration depth, or in the case of an inhomogeneous distribution of the X-ray absorbing atom within the sample. In those situations the experimental reflection-mode XAS data have to be compared with (ab initio) model calculations assuming the presence of certain structures and thicknesses of the involved surface layers (see, for example, Borthen & Strehblow, 1997;Lü tzenkirchen-Hecht & Frahm, 2006;Benzi et al, 2008). Nevertheless, a variation of the grazing angle allows a depth profiling of the materials under investigation similar to X-ray photoelectron spectroscopy (XPS).…”