Growth Of Ferroelectric Thin Films Research Articles

Removable polytetrafluoroethylene template based epitaxy of ferroelectric copolymer thin films

In recent years ferroelectric polymers have shown their great potentials in organic and flexible electronics. To meet the requirements of high-performance and low energy consumption of novel electronic devices and systems, structural and electrical properties of ferroelectric polymer thin films are expected to be further optimized. One possible way is to realize epitaxial growth of ferroelectric thin films via removable high-ordered polytetrafluoroethylene (PTFE) templates. Here two key parameters in epitaxy process, annealing temperature and applied pressure, are systematically studied and thus optimized through structural and electrical measurements of ferroelectric copolymer thin films. Experimental results indicate that controlled epitaxial growth is realized via suitable combination of both parameters. Annealing temperature above the melting point of ferroelectric copolymer films is required, and simultaneously moderate pressure (around 2.0 MPa here) should be applied. Over-low pressure (around 1.0 MPa here) usually results in the failure of epitaxy process, while over-high pressure (around 3.0 MPa here) often results in residual of PTFE templates on ferroelectric thin films.

Improved Thermal Stability of Ferroelectric Phase in Epitaxially Grown P(VDF-TrFE) Thin Films

In recent years ferroelectric polymers have attracted much attention due to their potentials in flexible electronics. To satisfy the requirements of low operation voltage and low power consumption, it is required to reduce the ferroelectric film thickness down to, for example, 100 nm. However, decreased film thickness results in low crystallinity and thus worse electrical performance. One possible solution is to realize the epitaxial growth of ferroelectric thin films via effective control of structure and orientation of ferroelectric crystals. Here we report our work on poly(tetrafluoroethylene)-template-induced ordered growth of ferroelectric thin films. We focus on the study of thermal stability of ferroelectric phase in these ferroelectric films. Our work indicates that epitaxial growth effectively increases the crystallinity and the melting and ferroelectric phase transition temperatures and implies the extended application of ferroelectric devices at higher temperature.

Epitaxial growth of LaNiO3 thin films on Si substrates using rf sputtering

Epitaxial LaNiO3 (001) thin films with an SrTiO3/TiN template layer have been deposited on Si(001) single crystal substrates by rf sputtering. The epitaxial growth of LaNiO3 was achieved in an Ar/O2 environment at low substrate temperatures from 140 to 310 °C. The orientation relationship was determined to be LaNiO3(001)[110]∥SrTiO3(001)[110]∥TiN(001)[110]∥Si(001)[110]. The deposited LaNiO3 films show a smooth and featureless surface with roughness below 1 nm. These smooth and crack-free LaNiO3 films provide promising electrodes for the subsequent epitaxial growth of ferroelectric thin films.

Pyroelectric Arrays Using Ceramics and Thin Films Integrated Radiation Collectors: Design Fabrication and Testing

Pyroelectric infra-red detectors have been of-interest for many years because of their wide wavelength response, good sensitivity and lack of need for cooling. Arrays of such detectors, comprising a pyroelectric material interfaced to an application specific integrated circuit for signal amplification and read out, provide an attractive solution to the problem of collecting spatial information on the IR distribution in a scene. Sol gel deposition provides an excellent technique for the growth of ferroelectric thin films and Mn-doped PZT30/70 films can be grown at 560°C with F D = 3.85 × 10−5 Pa−1/2 . A new concept is presented here: the use of arrays of thin film pyroelectric detector elements with integrated radiation collectors designed to enhance the intensity of the radiation falling on the element. Two collector designs are presented, one based on the use of wet-chemically-etched pyramidal cavities, the second based on the Compound Parabolic Concentrator (CPC). Approximations to truncated CPC structures were SF 6 -dry-etched into a silicon wafer, upon which had been defined pyroelectric IR sensors with low thermal conductance (spiral leg structure) fabricated in a high sensitivity PZT thin film. First experimental assessment of the performance of these structures is presented.

In situ electrical-field-induced growth and properties of Bi3TiNbO9 ferroelectric thin films

With Bi3TiNbO9 (BTN) ferroelectric samples, in situ electrical-field-induced growth of ferroelectric thin films was demonstrated to control the films’ microstructure and manipulate their ferroelectric properties. BTN films on Ti/SiO2/Si substrates were grown at a relatively low temperature (650 °C) with a biased electrical field during pulsed-laser deposition. The (001) orientation of the films, which makes no contribution to their polarization, was effectively reduced by the in situ electrical field of strength of 70 V/cm. This results in a large increase of remnant polarization from 1.1 to 6.2 μC/cm2, and reduction of the coercive field from 70 to 50 kV/cm, comparing the films grown freely under the same condition. Furthermore, the films showed an excellent fatigue-free property of up to 1010 switching cycles.

STUDIES OF MULTICOMPONENT OXIDE FILMS AND LAYERED HETEROSTRUCTURE GROWTH PROCESSES VIA IN SITU, TIME-OF-FLIGHT ION SCATTERING AND DIRECT RECOIL SPECTROSCOPY

▪ Abstract The understanding of film growth processes is critical for fabricating a variety of thin film-based devices. Many novel film-based devices require growth of films in background gas atmospheres such as oxygen and nitrogen for oxide or nitride films. The studies of film growth processes in background gas environments require special analytical techniques. We discuss a novel time-of-flight ion scattering and direct recoil spectroscopy (TOF-ISARS) technique developed in our laboratory that is capable of providing a wide range of information including film composition and surface structure during growth, at the atomic scale. We also discuss recent work focused on the growth of ferroelectric thin films and their integration with electrode layers relevant to the fabrication of ferroelectric capacitors.

Epitaxial Growth of Ferroelectric Thin Films on GaAs with MgO Buffer Layers by Pulsed Laser Deposition

AbstractEpitaxial growth of ferroelectric thin films on GaAs (100) by pulsed laser deposition was examined for integrated electro-optic device applications. To promote epitaxy of ferroelectrics and prevent interdiffusion, we have deposited several types of buffer layers. CeO2 reacted strongly with GaAs. Although Y203 9% stabilized-ZrO2 films showed epitaxial growth, YSZ reacted with GaAs at 780°C. MgO grew epitaxially and was stable even at 780°C. HRTEM observation showed a sharp interface between MgO and GaAs. BaTiO3 and SrTiO3 deposited on MgO/GaAs structures showed epitaxial growth. In-plane orientation was BaTiO3 [100 // MgO [100] // GaAs [100]. Epitaxial BaTiO3 films were c-axis oriented tetragonal phase and showed ferroelectric hysteresis.