Ferroelectric epitaxial nanocrystals obtained by a self-patterning method

Abstract

Lead zirconate titanate nanoislands were obtained by a self-patterning method making use of the instability of ultrathin films during high-temperature treatments. After high-temperature annealing, the as-deposited film breaks into islands with a narrow size distribution. The single-crystal nanoislands were studied by scanning and high-resolution transmission electron microscopy, atomic force microscopy, and x-ray diffraction. They show an epitaxial relationship with the Nb-doped (001) SrTiO3 substrate. The ferroelectric switching of several individual islands was investigated by piezoresponse force microscopy.

Growth of Ca3Co4O9 films: Simple chemical solution deposition and stress induced spontaneous dewetting

“…methodology for the fabrication of new devices based on nanostructures such as nanodots or nanowires. [12][13][14][15][16] In this article, we report on CSD of CCO349 films on LaAlO 3 ͑LAO͒ single crystal substrates and the dewetting effects associated with strains are also studied. The results show that CCO349 films can be prepared using the simple CSD method on LAO substrates, although the mismatch is several tens of percentage points, which can broaden selection of substrates, as well as opening up a simple route for the preparation of CCO349 films, especially for large-scale production.…”

Geometric shadowing from rippledSrRuO3∕SrTiO3surface templates induces self-organiza

“…Within this framework, several selforganization routes have been investigated, some of the most common ones being: 8 ͑i͒ self-organization driven by interfacial stress originated during heteroepitaxial growths, 9,10 ͑ii͒ ordered segregations of immiscible chemical phases, 7,11 ͑iii͒ using surfaces with nanometric periodicities ͑e.g., vicinal surfaces͒, 12 ͑iv͒ via chemical routes based on hydrothermal deposition 13 and/or self-assembly lithography, 14,15 and ͑v͒ through three-dimensional ͑3D͒ thickness instabilities for ultrathin films ͑known also as self-patterning͒ due to the formation of thermally unstable unfavored interfaces. 16,17 In an earlier work, we demonstrated the successful fabrication of Cr-doped SrZrO 3 ͑SZO͒ nanowires on rippled SrRuO 3 ͑SRO͒ templates SrZrO 3 , which are prepared in situ on phototreated vicinal SrTiO 3 ͑STO͒ substrates. 18 The heterostructure of stacked oxides studied there was chosen attending to the following functional properties: Undoped SZO suits to high voltage capacitive applications due to its high dielectric constant ͑ Ϸ 60͒ and breakdown strength ͑400 kV cm −1 ͒, 19 while SZO doped with transition metals ͑e.g., Cr͒ is a promising candidate for resistance-switching nonvolatile memories.…”

Fabrication of Arrays of Lead Zirconate Titanate (PZT) Nanodots via Block Copolymer Self-Assembly

“…Nanosphere lithography (NSL) has also been used to obtain 2D ferroelectric nanostructures, but the minimum feature size that could be achieved by this method was limited to ~ 50 nm. [15][16][17] Block copolymer (BCP) based self-assembly has emerged as a viable 'bottom-up' patterning technique for nanostructures, due to the ability to form different types of 2D and 3D nanoscale patterns on various substrates. 23,24 These selfassembled patterns have been used as nanolithographic masks, as well as templates for the fabrication of arrays of dots and wires of inorganic organic nanostructures.…”

“…22 While self-assembly-based 'bottom-up' methods offer facile high-throughput synthesis of ferroelectric nanoislands, they suffer from poor ordering and limited control over feature size, which limits their practical application. [16][17][18]22 Templateassisted synthesis is a simplistic low-cost route for fabricating ferroelectric nanodots, due to the number of deposition methods that can be utilized and good control over the dimensions of the nanostructures formed. 7,11,[19][20][21] For example, Lee et al 3 fabricated individually addressable epitaxial arrays of PZT nanodot capacitors (~ 60 nm in diameter and ~ 20 to 40 nm in height) with a density of 32 Gb cm -2 using anodic aluminium oxide (AAO) templates.…”

“…3,5,6,8,11 Isolated singlecrystalline ferroelectric nanostructures have shown improved memory characteristics such as high polarization retention compared to their thin film counterparts, due to the presence of single ferroelectric domains, 11 and increased electromechanical displacement due the reduction of clamping effects on 90 degree domain reorientation. 12 Techniques such as electron beam lithography, 5,6 focused ion beam milling, 12 nanoimprint lithography, 13,14 dip-pen lithography, 15 sol-gel selfassembly [16][17][18] and templating 7,11,[19][20][21] have been used successfully to fabricate arrays of discrete nanoislands or dots. Although 'top-down' lithography-based techniques have been successful in making precisely positioned ferroelectric nanodots, their inherent feature-size limitations, low throughput and high processing cost makes these techniques less prevalent.…”