Characterization of multiferroic thin films directly deposited on silicon for novel device applications

We have investigated the multiferroic and dielectric properties in Dy modified BiFeO<SUB>3</SUB> thin films deposited directly on silicon using pulsed laser deposition (PLD) technique. The results support the usability of these films in multiferroic based MEMS devices as well as gate dielectrics for future CMOS applications

Nanochanical characterization of multiferroic thin films for micro-electromechanical systems

In this paper, the elastic properties of Dy modified BiFeO<SUB>3</SUB> (BDFO) multiferroic films deposited on Si substrate are reported for the first time. The mechanical properties are extracted using nanoindentation technique. The Young's modulus and hardness of the BDFO films are found to be 140 ± 3 GPa and 7.5 ± 0.3 GPa respectively. In this study the properties in the region of penetration depth up to 20% of BDFO film thickness, are found out. For these indentation depths, Young's modulus and hardness are almost constant indicating that substrate effects are not significant. It is also confirmed that neither cracks, nor pile-ups can be observed for indentation loads up to 10 mN. However, at higher indentation loads (&gt;10 mN), bulging and spallation are observed suggesting delamination and buckling of the film. The mechanical properties of BDFO films are similar to that reported for lead zirconate titanate (PZT), while offering many novel properties. This report is accordingly expected to facilitate the design of BDFO-based micro-electromechanical systems devices

Structural, optical and vibrational properties of self-assembled Pbn+1(Ti1−xFex)nO3n+1−δ Ruddlesden-Popper superstructures

Bulk crystals and thin films of PbTi1−xFexO3−δ (PTFO) are multiferroic, exhibiting ferroelectricity and ferromagnetism at room temperature. Here we report that the Ruddlesden-Popper phase Pbn+1(Ti1−xFex)nO3n+1−δ forms spontaneously during pulsed laser deposition of PTFO on LaAlO3 substrates. High-resolution transmission electron microscopy, x-ray diffraction and x-ray photoemission spectroscopy were utilised to perform a structural and compositional analysis, demonstrating that and . The complex dielectric function of the films was determined from far-infrared to ultraviolet energies using a combination of terahertz time-domain spectroscopy, Fourier transform spectroscopy, and spectroscopic ellipsometry. The simultaneous Raman and infrared activity of phonon modes and the observation of second harmonic generation establishes a non-centrosymmetric point group for Pbn+1(Ti0.5Fe0.5)nO3n+1−δ, a prerequisite for (but not proof of) ferroelectricity. No evidence of macroscopic ferromagnetism was found in SQUID magnetometry. The ultrafast optical response exhibited coherent magnon oscillations compatible with local magnetic order, and additionally was used to study photocarrier cooling on picosecond timescales. An optical gap smaller than that of BiFeO3 and long photocarrier lifetimes may make this system interesting as a ferroelectric photovoltaic

Coherent magnon and acoustic phonon dynamics in tetragonal and rare-earth-doped BiFeO_{3} multiferroic thin films

Coherent magnons and acoustic phonons were impulsively excited and probed in thin films of the room temperature multiferroic Bi1−x−yDyxLayFeO3 using femtosecond laser pulses. The elastic moduli of rhombohedral, tetragonal, and rare-earth doped BiFeO3 were determined from acoustic-mode frequencies in conjunction with spectroscopic ellipsometry. A weak ferromagnetic order, induced alternately by magnetization in the growth direction or by tetragonality, created a magnon oscillation at 75 GHz, indicative of a Dzyaloshinskii-Moriya interaction energy of 0.31 meV