Monolithic integration of room-temperature multifunctional BaTiO3-CoFe2O4 epitaxial heterostructures on Si(001)

Abstract

The multifunctional (ferromagnetic and ferroelectric) response at room temperature that is elusive in single phase multiferroic materials can be achieved in a proper combination of ferroelectric perovskites and ferrimagnetic spinel oxides in horizontal heterostructures. In this work, lead-free CoFe2O4/BaTiO3 bilayers are integrated with Si(001) using LaNiO3/CeO2/YSZ as a tri-layer buffer. They present structural and functional properties close to those achieved on perovskite substrates: the bilayers are fully epitaxial with extremely flat surface, and exhibit robust ferromagnetism and ferroelectricity at room temperature.

Tailoring Lattice Strain and Ferroelectric Polarization of Epitaxial BaTiO3 Thin Films on Si(001)

“…The buffer layers were grown using the same parameters, including substrate temperature of 800 °C for YSZ and CeO2, and 700 °C for LNO, and oxygen pressure of 4x10-4 mbar for YSZ and CeO 2 , and 0.15 mbar for LNO; additional experimental conditions are reported elsewhere. 15,17,25 The deposition temperature was measured using a thermocouple inserted in the middle of the heater block. The thicknesses of the BTO, LNO, CeO 2 and YSZ layers are 110, 30, 20, and 60 nm, respectively.…”

“…The strategy is based on controlling the defects that generate strain by tuning the balance between thermodynamics and kinetics in the growth of BTO via modification of substrate deposition temperature. We focus on thin films integrated with Si(001), [15][16][17] and we show that epitaxial growth can be achieved in a broad deposition temperature window with a huge impact on the BTO tetragonality and ferroelectric polarization. In particular, high-quality c-oriented epitaxial BTO films are grown in a temperature window about 300 °C wide, permitting fine tuning of the c-axis (the polar axis) strain from 0% (high deposition temperature, favoring thermodynamics) to more than 2% (low deposition temperature, imposing kinetic limitations), and with the remnant polarization scaling with the c-axis.…”

Resistive switching in MoSe2/BaTiO3 hybrid structures

“…5-0626, the reflections of BTO in both structures are shifted to lower 2θ values due to the tensile stress caused by the thermal expansion mismatch with the Si substrate. 24 The gate voltage was swept from -5 V to +5 V and then backs again to -5 V. Figure 2(a) shows the C-V characteristics for the Al/Si/SiO x /MoSe 2 /Au structure. A transition from accumulation to depletion is clearly observed and no hysteresis can be found suggesting that the SiO x /MoSe 2 interface is of good quality.…”

Barium Titanate Nanostructures and Thin Films for Photonics

“…[31] Apart from the choice of material substrate, parameters like oxygen pressure or substrate temperature have large impact over the conductivity or the c-axis orientation, respectively. [35,36] Samples that deviate from stoichiometric composition are not anymore perfect dielectrics, while the deposition temperature may produce films with large stress and ferroelectric polarization.…”