Metal-Organic Chemical Vapor Deposition of Ferroelectric SrBi₂Ta₂O₉ Films from a Fluorine-Containing Precursor System

Abstract

MOCVD fabrication of ferroelectric SrBi2Ta2O9 (SBT) films using Sr(hfac)2·tetraglyme, Bi(C6H5)3, and Ta(OC2H5)5 precursors is reported. The SBT phase has been reproducibly obtained adopting a two-step procedure, namely, the deposition of a fluorine-containing Sr−Bi−Ta−O(F) matrix followed by the annealing step at 800 °C. The multicomponent deposition process was optimized by tuning the overall process to individual kinetics associated with each singled-out precursor, to film morphologies and microstructures, and finally to film properties. Particular attention has also been focused on the annealing process of the deposited Sr−Bi−Ta−O(F) matrix aimed at an efficient crystallization step of the SBT phase as well as on an efficient elimination of fluorine phases associated with decomposition of the fluorinated Sr precursors.

Evidence for Non‐Innocence of a β‐Diketonate Ligand

“…The deprotonated forms of pentane‐2,4‐dione (acac − ) and 1,1,1,5,5,5‐hexafluoropentane‐2,4‐dione, (hfac − ), are the most commonly used β‐diketonate ligands, with each garnering ∼3000 crystallographically characterized compounds . Notably, hfac − complexes demonstrate highly sought‐after properties, such as high vapor pressure and high solubility in non‐coordinating solvents, making them of interest for a wide range of applications, as in chemical vapor deposition, homogeneous catalysis, and molecule‐based magnets . Despite being so common, there are no reports of any non‐innocence of these ligands .…”

“…rhombic Pbca space group and features the Cr site located on an inversion center.T he Cr-N distance of 2.091(2) andt he Cr-O distances of 1.926(2) and 1.931(2) reveal no clearJ ahn-Te ller distortion, which,n onetheless, would be partially convoluted with the presence of different ligands. However,f or comparison, the isomorphous Cu II complex features aJ ahn-Teller axis along the CuÀO1 axis with CuÀO1 and CuÀO2 bond lengths of 2.225(4) and1 .995 (4) ,r espectively. [21] Althougha number of Cr II complexes have been reportedt ol ack the expected Jahn-Te ller distortion, [22] often attributed to the occurrence of dynamic effects, the absence of ad istortion renders the oxidation state assignment of + II ambiguous.…”

Synthesis and Structures of Bis(2‐dimethylaminoethyl)amine Adducts of Strontium Bis(2,2,6,6‐tetramethylheptane‐3,5‐dionate) and Their Use in the CVD of Cubic Strontium‐Doped Hafnium Dioxides

“…[10][11][12] b-diketonates and related complexes, especially those formed with the 2,2,6,6-tetramethylheptane-3,5-dionato (tmhd) ligand, are the most widely used precursors. [1] Due to the large size and low charge of the Group 2 metal ions, homoleptic tmhd complexes exist as oligomers (e.g., [Sr(tmhd) 2 ] 3 [13] and [Ba(tmhd) 2 ] 4 [14] ), which result in low precursor vapor pressures.…”

Fluorinated Heterometallic β-Diketonates as Volatile Single-Source Precursors for the Synthesis of Low-Valent Mixed-Metal Fluorides

“…All compounds explored for the synthesis of complex fluorides are nonvolatile. With ongoing miniaturization of electronic devices, there is a great interest in volatile precursors that can be used in metal−organic chemical vapor deposition (MOCVD) for the preparation of high-technological thin films with desired stoichiometry …”