Ferroelectric nanoparticles, wires and tubes: synthesis, characterisation and applications

Nanostructured materials are central to the evolution of future electronics and information technologies. Ferroelectrics have already been established as a dominant branch in the electronics sector because of their diverse application range such as ferroelectric memories, ferroelectric tunnel junctions, etc. The on-going dimensional downscaling of materials to allow packing of increased numbers of components onto integrated circuits provides the momentum for the evolution of nanostructured ferroelectric materials and devices. Nanoscaling of ferroelectric materials can result in a modification of their functionality, such as phase transition temperature or Curie temperature (TC), domain dynamics, dielectric constant, coercive field, spontaneous polarisation and piezoelectric response. Furthermore, nanoscaling can be used to form high density arrays of monodomain ferroelectric nanostructures, which is desirable for the miniaturisation of memory devices. This review article highlights some research breakthroughs in the fabrication, characterisation and applications of nanoscale ferroelectric materials over the last decade, with priority given to novel synthetic strategies

Nanoscale ferroelectric and piezoelectric properties of Sb2S3 nanowire arrays

We report the first observation of piezoelectricity and ferroelectricity in individual Sb2S3 nanowires embedded in anodic alumina templates. Switching spectroscopy-piezoresponse force microscopy (SS-PFM) measurements demonstrate that individual, c-axis-oriented Sb2S3 nanowires exhibit ferroelectric as well as piezoelectric switching behavior. Sb2S3 nanowires with nominal diameters of 200 and 100 nm showed d33(eff) values around 2 pm V–1, while the piezo coefficient obtained for 50 nm diameter nanowires was relatively low at around 0.8 pm V–1. A spontaneous polarization (Ps) of approximately 1.8 μC cm–2 was observed in the 200 and 100 nm Sb2S3 nanowires, which is a 100% enhancement when compared to bulk Sb2S3 and is probably due to the defect-free, single-crystalline nature of the nanowires synthesized. The 180° ferroelectric monodomains observed in Sb2S3 nanowires were due to uniform polarization alignment along the polar c-axis

Characterization of resistivity of Sb2S3 semiconductor nanowires by conductive AFM and in-situ methods

Conductive AFM and in situ methods were used to determine contact resistance and resistivity of individual Sb2S3 nanowires. Nanowires were deposited on oxidized Si surface for in situ measurements and on Si surface with macroelectrodes for conductive AFM (C-AFM) measurements. Contact resistance was determined by measurement of I(V) characteristics at different distances from the nanowire contact with the macroelectrode and resistivity of nanowires was determined. Sb2S3 is a soft material with low adhesion force to the surface and therefore special precautions were taken during measurements

Surface roughness assisted growth of vertically oriented ferroelectric SbSI nanorods

We report the catalyst-free synthesis of arrays of c-axis oriented antimony sulfoiodide nanorods on anodic aluminum oxide (AAO) substrates by vapor phase deposition. The surface roughness of the AAO substrates played a decisive role in the orientation control of the SbSI nanorods produced. The as-grown SbSI nanorods were single-crystalline and ⟨001⟩ oriented, as revealed from the X-ray diffraction and transmission electron microscopy analysis. Switching spectroscopy-piezoresponse force microscopy experiments demonstrated, for the first time, the presence of switchable ferroelectricity and piezoelectricity in individual SbSI nanorods. Ferroelectric switching in the SbSI nanorods was found to occur via a 180° domain reversal, because of the preferred orientation of the nanorods along their polar c-axis

Application of electrochemical impedance for characterising arrays of Bi2S3 nanowires

Electrochemical Impedance Spectroscopy (EIS) was used to characterise the electrical properties of bismuth sulphide (Bi2S3) nanowires (NWs) templated within anodic aluminium oxide (AAO) membranes. A specially engineered cell, with a nominal electrolyte volume of 0.1–0.2 ml, was used to hold and measure the electrochemical impedance of the fragile NW/AAO samples. An equivalent circuit model was developed to determine the filling density of nanowires within the porous templates. The EIS method can be utilised to probe the nanowire filling density in porous membranes over large sample areas, which is often unobtainable using electron microscopy and conductive atomic force microscopy techniques

The Impact of Agriculture Extension Training Programs on the Extension Services in Kenya

Many studies have shown challenges and in some cases major failures toward the training programs sponsored by extension services. Extension services in Kenya are supposed to help local farming communities’ increase their productivity towards the survival of the agriculture industry in Kenya. Farming is the main source of income and survival for many Kenyans therefore; this research looked in to the perceptions of the farmers toward the extension services in Kisumu district, Kenya. Another part of this research was to discover the preference of the farmers toward different extension approaches to create motivation for the farmers, to participate in the extension training programs. The research showed a significant motivation factor presents in the farming community of Kenya, to learn new techniques to improve their farming practices and to become more profitable. However, due to lack of organization and planning by the extension services, farmers got discouraged to attend any training or workshop in their farming community. Another factor is the non-supportive government incentives toward extension services Many extension agents could not be found in the farming communities to provide farmers timely information and guidance toward their problems. Lastly, the extension workstations were without proper technology and resources due to lack of funding by the government, which created a dilemma for the Kenyans farming community

Application of electrochemical impedance for characterising arrays of Bi2S3 nanowires

Electrochemical Impedance Spectroscopy (EIS) was used to characterise the electrical properties of bismuth sulphide (Bi2S3) nanowires (NWs) templated within anodic aluminium oxide (AAO) membranes. A specially engineered cell, with a nominal electrolyte volume of 0.1–0.2 ml, was used to hold and measure the electrochemical impedance of the fragile NW/AAO samples. An equivalent circuit model was developed to determine the filling density of nanowires within the porous templates. The EIS method can be utilised to probe the nanowire filling density in porous membranes over large sample areas, which is often unobtainable using electron microscopy and conductive atomic force microscopy techniques

A Rare Case of Upper Gastrointestinal Bleeding and Esophageal Candidiasis in Severe Achalasia

Achalasia is an esophageal dysmotility disorder characterized by failure of relaxation of the lower esophageal sphincter (LES), accompanied by aperistalsis of the distal esophagus. Recent data show that the prevalence of achalasia in the United States is 10 per 100,000 individuals.1 Complications of achalasia include esophagitis, esophageal ulcer, esophagealtracheal fistula, esophageal rupture, aspiration pneumonia, and squamous cell carcinoma. We report a rare case of upper gastrointestinal bleeding associated with esophageal ulcer and candidiasis in a patient with severe achalasia requiring multiple endoscopic interventions

Relative Humidity Dependent Resistance Switching of Bi2S3 Nanowires

Funding Information: This work was done within Latvian National Research Program IMIS 2 and University of Latvia Base/Performance Funding Projects nos. AAP2016/B043 and ZD2010/AZ19. Publisher Copyright: © 2017 Raimonds Meija et al.Electrical properties of Bi2S3 nanowires grown using a single source precursor in anodic aluminum oxide templates are sensitive to the relative humidity in an inert gas environment. Dynamic sensing dependency is obtained and shows presence of spontaneous resistance switching effect between low and high relative humidity states. Employing the thermionic field emission theory, heights of Schottky barriers are estimated from the current-voltage characteristics and in relation to the humidity response. The change of Schottky barrier height is explained by local changes in physically adsorbed water molecules on the surface of the nanowire.publishersversionPeer reviewe

Fabrication of arrays of lead zirconate titanate (PZT) nanodots via block copolymer self-assembly

This Article presents a simple methodology for the fabrication of two-dimensional arrays of lead zirconate titanate (PZT) nanodots on n-doped Si substrates via the directed self-assembly of PS-b-PEO block copolymer templates. The approach produces highly ordered PZT nanodot patterns, with lateral widths and heights as small as 20 and 10 nm, respectively, and a coverage density as high as ∼68 × 109 nanodots cm–2. The existence of a perovskite phase in the nanodots was confirmed by X-ray diffraction and X-ray photoelectron spectroscopy. The piezo-amplitude and ferroelectric domain response obtained from the nanodots, through piezoresponse force microscopy, confirmed the presence of ferroelectricity in the PZT arrays. Notably, PZT nanodots with a thickness ∼10 nm, which is close to the critical size limit of PZT, showed ferroelectric behavior. The presence of a multi-a/c domain structure in the nanodots was attributed to their polycrystalline nature