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Schematic diagrams illustrate a possible pore formation mechanism in ( BFO ) 0 . 5 : ( SmO ) 0 . 5 nanocomposite during high temperature annealing. (a)–(c) are cross-sectional view; (d)–(f) are plan-view. Areas in red correspond to BFO phase and areas in yellow correspond to SmO phase. (a) and (d) illustrates the initial VAN structure with a diameter of d . (b) and (e) represent the initial decomposition and vaporization process with pore size d 1 = d . (c) and (f) describe the nanopore growth and the coalescence of the SmO phase ( d 3 > d 2 > d 1 ). d
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Porous thin films with ordered nanopores have been processed by thermal treatment on vertically aligned nanocomposites (VAN), e.g., (BiFeO(3))(0.5):(Sm(2)O(3))(0.5) VAN thin films. Uniformly distributed nanopores with an average diameter of 60 nm and 150 nm were formed at the bottom and top of the nanoporous films, respectively. Controllable porosi...
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... to the different melting temperatures of BFO (T m = 817- 825 • C) and SmO (T m = 2300 • C), BFO will decompose and evaporate before SmO starts to decompose. The schematics in figure 4 show the possible scenario for the pore formation during annealing from both cross-sectional view ((a)-(c)) and plan-view ( figure 5(a) presents the surface pore density of the annealed film. These surface pores are the ones shown on the top layer in the annealed film (shown in figure 3(a)). ...
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Citations
... The possible fields of applications of VAN strained films are therefore numerous, including magnetoresistance [121][122][123], ionic/electronic conductors [122,[124][125][126], or resistive switching [127]. VAN films have been also used for fabricating singular nanostructures, such as nanoporous epitaxial films [128]. On the other hand, it is important to highlight that nowadays the fabrication of VAN thin films is still restricted to a limited number of materials' combinations. ...
The behavior of interface-dominated metal-oxide thin films is largely influenced by nanoionic effects. The control and engineering of interfaces becomes a powerful tool for the design of optimized electrochemical devices, in which ion movement plays a primary role. This chapter provides a comprehensive description of the most relevant ionic phenomena taking place in interfaces, as the basis of nanoionics. Grain boundaries and strain-dominated thin films are analyzed in detail, highlighting the fascinating relation between structure and chemical properties. The main strategies for an active implementation of these two interfaces in real devices are discussed. The chapter concludes overviewing foreseen future applications of nanoionics in superior energy and information technologies based on metal-oxide thin films.
... It is still an open field of research the communications between each of the nano-pores in nano-scale dimensions and their effect as a whole in the bulk material. In recent times, nano-porous thin films have attracted much research interests owing to their potential applications in fuel cells [1][2][3][4][5][6]; pressure and gas sensors [7][8]. The utilization of nanoporous membranes in such devices require geometrically controllable nanopores with controlled pore size and pore-density arrangements [6]. ...
... In recent times, nano-porous thin films have attracted much research interests owing to their potential applications in fuel cells [1][2][3][4][5][6]; pressure and gas sensors [7][8]. The utilization of nanoporous membranes in such devices require geometrically controllable nanopores with controlled pore size and pore-density arrangements [6]. ...
In this article, we report the process induced variation in the characteristics of PECVD deposited and thermally grown silicon dioxide (SiO2) thin film. We find key differences in the porosity, arrangement of the nano-pores, surface roughness, refractive index and electrical resistivity of the SiO2 thin films obtained by the two methods. While the occurrence of the nanoporous structure is an inherent property of the material and independent of the process of film growth or deposition, the arrangements of these nano-pores in the oxide film is process dependent. The distinct arrangements of the nano-pores are signatures of the deposition/growth processes. Morphological analysis has been carried out to demonstrate the difference between oxides either grown by thermal oxidation or through PECVD deposition. The tunable conductive behavior of the metal filled nano-porous oxides is also demonstrated, which has potential to be used as conductive oxides in various applications.
... Recently, the growth of heteroepitaxial thin films in the form of self-assembled vertically aligned nanocomposite (VANs) on various substrates has spurred a significant interest. 13,14 Self-assembled vertically aligned nanocom- posites 15,16 open new possibilities for applications in industry. This nanolevel construction provides a precise control on the physical properties of the materials through vertical strain control, as well as by enhancing coupling between various degrees of freedom due to large vertical interfacial area or interface to volume ratio. ...
The self-assembled growth of vertically aligned nanostructures of BaTiO3 in the matrix of Fe2O3 is
described. The arrays of well controlled and systematically ordered nanostructures of composite
phases were grown on MgO and SrTiO3 single crystalline substrate by using the pulse laser deposi-
tion technique under optimized conditions. The phase purities of the composite structures were
characterized by using x-ray diffraction and Raman spectroscopy. The surface topographical and
morphological measurements were carried out for confirming the growth on nanostructures in the
composite thin films. The ferroelectric properties of these composite films were probed by electrical
polarization versus electric field (P-E) measurements. The electronic and magnetic properties of the
composite were studied by employing x-ray absorption spectroscopy and magnetization measure-
ments. The presence of strain state in nanostructures is found to play an important role in modifying
the crystal field effects as well as the magnetic properties of the composite compound. It is shown
that the vertical self-assembly of nanorods of BaTiO3 can be grown in the matrix layer of Fe2O3 on
the MgO substrate by coablation.
... It is still an open field of research the communications between each of the nano-pores in nano-scale dimensions and their effect as a whole in the bulk material. In recent times, nano-porous thin films have attracted much research interests owing to their potential applications in fuel cells [1][2][3][4][5][6]; pressure and gas sensors [7][8]. The utilization of nanoporous membranes in such devices require geometrically controllable nanopores with controlled pore size and pore-density arrangements [6]. ...
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In this article, we report the process induced variation in the characteristics of PECVD deposited and thermally grown silicon dioxide (SiO2) thin film. We find key differences in the porosity, arrangement of the nano-pores, surface roughness, refractive index and electrical resistivity of the SiO2 thin films obtained by the two methods. While the occurrence of the nanoporous structure is an inherent property of the material and independent of the process of film growth or deposition, the arrangements of these nano-pores in the oxide film is process dependent. The distinct arrangements of the nano-pores are signatures of the deposition/growth processes. Morphological analysis has been carried out to demonstrate the difference between oxides either grown by thermal oxidation or through PECVD deposition. The tunable conductive behavior of the metal filled nano-porous oxides is also demonstrated, which has potential to be used as conductive oxides in various applications.
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... Very recently, self-assembled vertically aligned nanocomposite (VAN) thin films with two immiscible oxides heteroepitaxially grown on single crystal substrates have attracted considerable research interest not only for understanding the fundamental growth mechanisms of the self-assembled VAN [1] [2] [3] [4], but also for exploring their potential applications [5] [6] [7]. Unique properties that are not present in the single-phase materials could be enabled in the vertical heteroepitaxial nanocomposite films because of the strong interfacial couplings at the vertical phase boundaries. ...
Two-phase (La(0.7)Sr(0.3)MnO(3))(0.5):(CeO(2))(0.5) (LSMO:CeO(2)) heteroepitaxial nanocomposite films were grown on SrTiO(3) (STO) (001) by pulsed laser deposition (PLD). X-ray diffraction (XRD) and transmission electron microscopy (TEM) results show that LSMO:CeO(2) films epitaxially grow on STO as self-assembled vertically aligned nanocomposite (VAN). Magnetic and magnetotransport measurements demonstrate that the LSMO phase in the VAN structure behaves differently from its epitaxial single-phase counterpart, e.g. greatly enhanced coercivity (H(C)) and low-field magnetoresistance (LFMR). The enhanced properties in the VAN system are attributed to the interaction between the perovskite and the secondary phase or phase boundary. The results suggest that the growth of functional oxide in another oxide matrix with vertical heteroepitaxial form is a promising approach to achieve new functionality that may not be easily realized in the single epitaxial phase.
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(K,Na)NbO3-based lead-free ferroelectric materials are highly desired in modern electronic applications and have long been considered as a strong candidate for replacing (Pb,Zr)TiO3, but most of them are deficient in large remnant polarization and decent thermal stability. Here, a unique lead-free 0.95(K0.49Na0.49Li0.02)(Nb0.8Ta0.2)O3-0.05CaZrO3 with 2 wt.% MnO2 addition (KNNLT-CZ-M) ferroelectric film with special nanocomposite structures grown on La0.7Sr0.3MnO3-coated SrTiO3 (001) substrates is demonstrated. The KNNLT-CZ-M films display excellent ferroelectricity with a large twice remnant polarization of 64.91 μC/cm2, a superior thermal stability of ferroelectricity from -196 ˚C to 300 ˚C and a high Curie temperature of 400 ˚C. These robust performances could be attributed to the densely arranged self-assembled nanocolumns (~ 10 nm in diameter) in the films, which can vertically strain the matrix and enhance its b/a ratio. The formation of the nanocolumns critically depends on the CaZrO3 component. Our results may help the design of new type lead-free ferroelectric films and promote their potential applications in microelectronic-devices.
In this work, I start by introducing a relatively recently innovated thin film architecture which offers a new direction in strain control, the vertically aligned nanocomposite (VAN). I first present the literature in the field, explaining the advantages and unique novel properties stemming from VAN structures. Next, I introduce the work I did to examine the unique strain states of Ba0.6Sr0.4TiO3–Sm2O3 VAN structures. It was found that the strain states in the functional Ba0.6Sr0.4TiO3 phase are unconventional compared to those in planar thin films. 3-dimensional strain was found to be acting on the Ba0.6Sr0.4TiO3 phase in the VAN structure. The origin of the strain was explained using a simple model which takes into account thermal expansion mismatch as well as lattice mismatch and elastic coefficients. The ferroelectric properties of the films were presented in relation to the observed strain states. I next present the work I did on the influence of strain on the magnetic properties in VAN film of Sm0.34Sr0.66MnO3–Sm2O3. Ferromagnetism was achieved in an otherwise antiferromagnetic Sm0.34Sr0.66MnO3. The effect was explained by a strain induced transition from super-exchange to double exchange coupling in the material. Last but not least, the potential of scalability of VAN films was explored by using sputtering to grow VAN structures instead of the commonly-used PLD growth. BaTiO3–Sm2O3 was used as a primary study material due to its well reported VAN properties. Preliminary results showing indications of a VAN structure. Some basic physical property characterization is also presented and compared to the properties of PLD-grown films in the literature. Limitations and challenges that arise due to the fundamental differences between sputtering and PLD are also described.
