Dynamic nanocrystal response and high temperature growth of carbon nanotube–ferroelectric hybrid nanostructure

Abstract

A long standing problem related to the capping of carbon nanotubes (CNT) by inorganic materials at high temperature has been solved. In situ dynamic response of Pb(Zr 0.52 Ti 0.48 )O 3 (PZT) nanocrystals attached to the wings of the outer surface of PZT/CNT hybrid-nanostructure has been demonstrated under a constantenergy high-resolution transmission electron microscopy (HRTEM) e-beam. PZT nanocrystals revealed that the crystal orientations, positions, faces, and hopping states change with time. HRTEM study has been performed to investigate the microstructure of hybrid nanostructures and nanosize polycrystal trapped across the wings. Raman spectroscopy was utilized to investigate the local structures, defects, crystal qualities and temperature dependent growth and degradation of hybrid nanostructures. Raman spectra indicate that MWCNT and PZT/MWCNT/n-Si possess good quality of CNT before and after PZT deposition until 650 C. The monoclinic Cc/Cm phase of PZT which is optimum in piezoelectric properties was prominent in the hybrid structure and should be useful for device applications. An unusual hexagonal faceting oscillation of the nano-crystal perimeter on a 10-30 s period is also observed.

Covering vertically aligned carbon nanotubes with a multiferroic compound

“…The shift in Raman peaks gives the information of the stress level of the MWCNTs [32]. In our case, because the observed shift there is quite small stresses developed at the interface are not so strong, as observed for example for MWCNTs covered with PZT by pulse laser deposition [10,11]. The change in the intensity ratio of D and G bands (I d /I g ) is 1.0 and 1.2 for the MWCNTs and BFO coated VA-MWCNTs of this study, respectively.…”

“…VA-MWCNTs used in this work depict two characteristic peaks at 1336 and 1575 cm -1 corresponding to D and G band respectively, where the D band is attributed to the breathing vibration of aromatic rings of carbon in the lattice, indicating the defect level of CNTs and G band corresponds to E2g mode where atoms of the carbon unit cell vibrate tangentially to each other [34]. After the BFO deposition the D and G band of MWCNTs shift to high frequency by ~2 cm -1 and the full width half maximum of the peaks also decreases due to less phonons interaction [11]. The shift in Raman peaks gives the information of the stress level of the MWCNTs [32].…”

“…The damage of CNTs lattice and contaminations from the silicon substrate was reported in this work. Later, these same researchers used pulse laser deposition technique to coat CNTs with ferroelectrics, as Ba 0.7 Sr 0.3 TiO 3 and PZT [10][11][12] and ferromagnetic as La 0.67 Sr 0.33 MnO 3 [13]. In the above studies the working principle was based on the coverage of individual tubes.…”

Enhanced electrical properties in ferroelectric thin films on conductive Au–LaNiO3 nanocomposite electrodes via modulation of Schottky potential barrier

“…7 Lead zirconate titanate (PZT) is one of the most extensively used ferroelectric materials, owing to its excellent ferroelectric, dielectric, and piezoelectric properties. 8 The ferroelectric properties of PZT thin lms strongly depend on the electrode materials, in particularly the bottom electrode. To act as electrodes for ferroelectric thin lms, several conditions must be satised, such as: (1) the resistivity of electrode must be as low as possible; (2) the electrode must be chemically stable under high temperatures, not react with ferroelectrics during the fabrication process; (3) the electrode has strong adhesion with silicon substrate; (4) the electrode can provide a reasonable ferroelectric/electrode interface with suitable electronic contact; (5) the electrode plays a role in controlling the microstructure and orientation of ferroelectric thin lms.…”

Unveiling the Role of CNTs in the Phase Formation of One-Dimensional Ferroelectrics

“…The authors found that annealing at 600 °C resulted in damage to the CNT lattice and reaction between the substrate and CNTs. Ashok et al , using pulsed-laser deposition (PLD) under controlled oxygen partial pressure (70–80 mTorr) successfully coated MWCNTs with PZT at ∼550 °C and with 150–200 nm Ba 0.7 Sr 0.3 TiO 3 (BST) at 650 °C. In addition, Yang et al used PLD to form coaxial multiferroic nanowires of MWCNTs with CoFe 2 O 3 and BaTiO 3 .…”