Nanodomain reversal

In this paper we present a comprehensive experimental and theoretical description of nanodomain reversal in fe bulk crystals an experimental method for domain switching using hvafm, results on nanodomain switching using hvafm and under indirect electron beam exposure, theory of fe domain breakdown and our last development of the fabrication of nanodomain gratings by the use of multiple tip arrays. We show that fdb is a new physical phenomenon observed in bulk fe crystals, and is the basis for the development of nanodomain technology in bulk fe crystals. This technology is required for future photonic, acoustic and microelectronic devices. 

Three physical and technology-related fundamental key issues of fe nanodomain reversal and fabrication of nanodomain structures in fe thin films and fe bulk crystals are under theoretical and experimental consideration (i) technological requirements and the minimal size of fe domains (n) experimental technique for nanodomain reversal and (hi) physics of nanodomain switching in fe films and bulk crystals. 

Low and high voltage AFM for nanodomain reversal in FE bulk crystals... 

Nanometer scale domain configurations in fe bulk crystals pave the way for a new class of photonic devices. As an example, preliminary calculations show that a uv laser (A = 300 nm) based on second harmonic generation in LiTaC>3 crystal requires a periodic nanodomain superlattice with domain widths of around 700 nm. In addition, the current domain gratings in ferroelectric crystals are suitable only for quasi-phase-matched nonlinear interactions in the forward direction, where the pump and generated beams propagate in the same direction. Sub-micron ferroelectric domain gratings are the basis for a new family of devices based on backward nonlinear quasi-phase-matched optical interactions in which the generated beam travels in a reverse or another non-collinear direction to the incident beam. Non-collinear... 

The classical experimental setup developed for fe polarization reversal implies a singledomain fe sample sandwiched between two electrodes [28], While conventional domain inversion techniques use equal sized electrodes covering the polar faces of fe templates, nanodomain inversion occurs under totally different conditions when the bottom electrode is a uniform plate and the upper one is a point contact. Two different kinds of the upper switching mobile nanoelectrodes may be considered afm tip (and/or array of tips) and electron drop formed using electron beam exposure. When a voltage stress is applied to the nanoelectrode, both the electric field intensity and its spatial distribution strongly differ in fe thin films (thin fe crystals) and bulk fe crystals. 

The physical limits and technological requirements of domain dimensions for a new generation of nanodomain-based devices were considered. It was shown that for both ferroelectric thin films and crystals the achievable domain size is in the range of 100 nm. It is shown that for 100 nm thick ferroelectric films, an application of nanosize electrodes does not make a big difference compared with conventional polarization reversal setups and physical mechanism. However, in the case of bulk ferroelectrics, the use of a switching afm tip electrode for generation of long domains with a nanometer size radius requires a new approach both for polarization reversal instrumentation and physics of domain inversion. 

The surfactant layer limits growth and aggregation of nanoparticles prepared in (w/o) microemulsions and maintains their sizes within the nanodomain. Furthermore, increasing the surfactant concentration at constant water to surfactant mole ratio, R, is accompanied by an increase in the population of reverse micelles [43], In addition, reactive surfactants participate in product formation and shift equilibrium reactions towards more product concenhation. All these facts suggest that an increase of the surfactant concentration favors higher-nanoparticle uptake. Higher uptake, on the other hand, may lead to particle aggregation due to the increase in probability of collision between nanoparticle-populated reverse micelles. 

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