Microwave-Assisted Hydrothermal Synthesis of BiFe_xCr_1–xO₃ Ferroelectric Thin Films

Abstract

We synthesize ferroelectric BiFe x Cr1–x O3 thin films by microwave-assisted hydrothermal synthesis on (111) oriented Nb-doped SrTiO3 substrates. Bi­(NO3)3, Fe­(NO3)3, Cr­(NO3)3, and KOH are used in the precursor solution, along with deionized water. Combination of Raman and X-ray photoelectron spectroscopies confirmed the incorporation of chromium into the rhombohedral structure of BiFeO3. The effect of deposition time on the surface morphology and the ferroelectric properties of the films are analyzed. This reveals that if the deposition goes on beyond completion of the reaction (10 min at 120 W), the ferroelectric properties of the film deteriorate due to stoichiometry changes. Through piezoresponse force microscopy, we show that Cr significantly deteriorates the film retention, which cannot be recovered by thermal annealing.

BiFe1–xCrxO3 Ferroelectric Tunnel Junctions for Neuromorphic Systems

“…In this image, the dark regions are negatively poled (green square), while the brighter regions are positively poled (inner blue square). While the weak contrast thereby obtained could have different origins, it could indicate a poor ferroelectric retention due to the high concentration of Cr in the films . The remaining portion of the map is in its pristine state and reveals a preferential spontaneous downward polarization.…”

“…While the weak contrast thereby obtained could have different origins, 48 it could indicate a poor ferroelectric retention due to the high concentration of Cr in the films. 37 The remaining portion of the map is in its pristine state and reveals a preferential spontaneous downward polarization.…”

“…35 Here, we fabricate BiFe 0.45 Cr 0.55 O 3 ferroelectric tunnel junctions using niobium (Nb):doped (111) oriented strontium titanate (SrTiO 3 ) and platinum (Pt) as the bottom and top electrodes, respectively. While BiFe 1−x Cr x O 3 was mainly synthesized by pulsed laser deposition, 31 chemical solution deposition, 36 or through microwave-assisted hydrothermal synthesis, 35,37 we here exploit the more industry favored radio frequency (RF) magnetron sputtering. After reconstructing the electronic band profile of our structures, we demonstrate the resistive switching in our devices through electrical characterizations.…”

Accelerated microwave-assisted hydrothermal/solvothermal processing: Fundamentals, morphologies, and applications

“…The preparation of electroceramics, by the MAH process including BaTiO 3 [142], BiFeO 3 [143], and BiFe x Cr 1 − x O 3 [144]. Figure 12 gives some examples of morphologies achieved in the MAH/S synthesis of BaTiO 3 , CaTiO 3 , and BaZrO 3 .…”

Origin of Ferroelectric Modification: The Thermal Behavior of Dopant Ions

“…The ferroelectric phase transition (FPT) at Curie temperature is the intrinsic characteristic of all ferroelectrics. Though many kinds of ferroelectric materials have been found up to now, − all materials have their own strengths and weaknesses. Take the prototype ferroelectric PbTiO 3 as an example; it has much larger piezoelectric responses but gives rise to environmental concerns with lead content.…”