The Influence of the Precursor on the Formation of Bi 2 O 3 Polymorphs in CSD ‐Derived Thin Films

This work examines the synthesis and characterization of crack‐free, β‐ Bi 2 O 3 thin films prepared on Pt / TiO 2 / SiO 2 / Si or corundum substrates using the sol‐gel method. We observed that the Bi ‐based precursor has a pronounced influence on the β‐ Bi 2 O 3 phase formation. Well‐crystallized, single β‐ Bi 2 O 3 thin films were obtained from Bi ‐2ethylhexanoate at a temperature of 400°C. In contrast, thin films deposited from Bi ‐nitrate and Bi ‐acetate resulted in non‐single Bi 2 O 3 phase formation. TEOS was used for the stabilization of the β‐ Bi 2 O 3 phase. The phase composition of the thin films was characterized by means of X‐ray diffraction ( XRD ), whereas the morphology and thickness of the thin films were studied using scanning electron microscopy ( SEM ). The β‐ Bi 2 O 3 films' dielectric properties were characterized utilizing microwave‐frequency measurement techniques: (1) the split‐post dielectric resonator method (15 GHz) and (2) the planar capacitor configuration (1–5 GHz). The dielectric constant and dielectric loss measured at 15 GHz were 257 and 7.5 × 10 −3 , respectively.