Off‐Stoichiometry of Magnetron Sputtered Ba_1−xSr_xTiO₃ Thin Films

Abstract

Barium strontium titanate thin films with different Ba/Sr ratios deposited by radio-frequency magnetron sputtering are studied with respect to their composition using in situ X-ray photoelectron spectroscopy. The deposited samples can be described as either titanium-rich or stoichiometric, with cation B/A ratios (i.e., ratios between the Ti and (Ba þ Sr) concentrations) of 1.2-1.6 or 0.7-1.0, respectively. Volume sensitive compositional analysis using transmission electron microscopy shows a non-stoichiometry, which is less pronounced than at the surface. X-ray diffraction only shows cubic perovskite reflections. Together with photoelectron binding energy differences and full widths at half maxima of the Ti 2p and O 1s emissions, this indicates that all films consist of a single phase. The relation between oxygen concentration and B/A ratio further indicates that the deviation of stoichiometry is accommodated by removal or insertion of (Ba,Sr)O. The higher variation of (Ba,Sr)O content near the surface as compared to the bulk may be associated to an increased strain, which is proposed to contribute to surface roughening.

Origin of Surface Reduction upon Water Adsorption on Oriented NiO Thin Films and Its Relation to Electrochemical Activity

“…1(a). Details of the preparation and properties of oriented Pt substrates are reported in [25] and AFM images of Pt substrates are shown in Fig. S3 in the Supporting Information.…”

Nonvolatile bipolar resistive switching characteristics of aluminum oxide grown by thermal oxidation processes

“…Obviously, an increase in the O 2 ratio during the annealing process can facilitate reactions (1) and (2) to proceed to the right, leading to an increase in oxygen interstitials and Al vacancies. These defects play a role similar to oxygen vacancy, which can generate additional carriers or assist in external carrier injection to increase conduction current [25][26][27]. Therefore, they are considered as key factors for determining electrical properties of AlO x devices.…”

“…The AlO x film, annealed in a pure O 2 environment, has an O/Al ratio of 1.87, which is significantly higher than 1.5 of a stoichiometric Al 2 O 3 film. This implies that excessive O i and V Al are existing in the AlO x film (figure 7(a-1)), and carriers can transport via these abundant and connected defect states [27,28], resulting in a high conductive and nonswitching behavior of the device (figure 7(a-2)). When the O 2 ratio in oxidation ambient reduces to 50%, the O/Al ratio [19,20,29], which explains the polarity-independent set feature of the AlO x RRAM (figure 2(a)).…”

Oxygen Surface Exchange and Tracer Diffusion in Differently Oriented Thin Films of Gd-Doped CeO2

“…34 As the sputter target, a ceramic Ce 0.99 Gd 0.01 O 1.995 sample (EVOCHEM Advanced Materials, Offenbach am Main, Germany), with a diameter of 2″ was used. The sputter deposition was carried out with a power of 25 W, with a distance between the target and the sample of 7 cm, in an atmosphere of Ar(99.999% purity) at a pressure of p = 0.5 Pa and at a substrate temperature of T = 823 K. These conditions resulted in a deposition rate of roughly 1 nm min 41 The use of Pt also has the benefit of avoiding an oxide|oxide interface, across which cation interdiffusion may occur. Al 2 O 3 and MgO single crystals were obtained from CrysTec (Berlin, Germany).…”