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The (V,Al) co-doped ZnO nano-structured powders (Zn0.9-xV0.1AlxO, where x = 0.02, 0.03 and 0.04) were synthesized via the sol-gel technique and their structural and optical properties were investigated. The effect of Al concentration on the structural and optical properties of the Zn0.9-xV0.1AlxO nanopowders was studied using various techniques. The XRD patterns indicate that the samples have a polycrystalline wurtzite structure. The crystallite size increases with increasing the Al content and lies in the range of 23 to 30 nm. The lattice strain, estimated by the Stokes-Wilson equation, decreases when Al content increases. SEM and TEM micrographs show that Zn0.9-xV0.1AlxO powders are the agglomeration of nanoparticles having spherical and hexagonal shapes with dimensions ranging from 20 to 30 nm. FT-IR spectra show a distinct absorption peak at about 500 cm-1 for ZnO stretching modes and other peaks related to OH and H2O bands. Raman spectra confirm the wurtzite structure of the Zn0.9-xV0.1AlxO nanoparticles. The direct band gaps of the synthesized Zn0.9-xV0.1AlxO nanopowders, estimated from the Brus equation and the crystallite sizes deduced from XRD, are around 3.308 eV. The decomposition process of the dried gel system was investigated by thermal gravimetric analysis (TGA). [ABSTRACT FROM AUTHOR]

Thin films of GaxTe100-x (x = 3, 6, 9 and 12) have been synthesized by thermal evaporation. From SEM images, it is observed that all the films contain nanoparticles of sizes varying from 100 to 200 nm. The dc electrical conductivity of the as-deposited films of GaxTe100-x nanoparticles is measured as a function of temperature range from 298 to 383 K, and increases exponentially with temperature. The value of the activation energy, calculated from the slope of ln σdc versus 1000/T plots, is found to decrease with increase in the Ga content. On the basis of the value of the pre-exponential factor σo, it is suggested that the conduction is due to thermally assisted tunneling of carriers in localized states near the band edges. The optical measurements suggest an indirect optical band gap in this system. The value of the optical band gap decreases on increasing the Ga concentration. [ABSTRACT FROM AUTHOR]

A new series of Ni 1-x Al x O (0 ≤ x ≤ 0.023) films was prepared using the co-sputtering technique. The influence of the partial replacement of Ni-atoms by Al-atoms on the structure, growth orientation, and the lattice strain of NiO crystallites was emphasized. These films exhibit a cubic structure with preferential orientation along the (111) plane. The surface topography was investigated using atomic force microscopy and the lattice vibration was studied using Raman spectroscopy. The optical absorption spectroscopy indicated that the sputtered films depict a direct bandgap energy in the range of 3.31–3.03eV. Likewise, the influence of the inclusion of Al in NiO on the localized states is premeditated in terms of Urbach energy. The photoluminescence measurements divulged that the sputtered films contain oxygen vacancies, nickel vacancies, and interstitial oxygen defects. On the other hand, the incorporation of Al-atoms in the Ni-sites leads to the improvement of the electrical conductivity. The optoelectronic properties of the Ni 1-x Al x O (0 ≤ x ≤ 0.023) films were studied. The photo-detection mechanism of the constructed Ag/n-si/Ni 1-x Al x O/Ag photodiodes was investigated. It was found that the Ni 1-x Al x O (0 ≤ x ≤ 0.023) films exhibited a very fast photo-detection response of 2s and a high sensitivity of 3 × 10−4 A cm−2.sun−1 with high stability and reproducibility. [ABSTRACT FROM AUTHOR]

• In 1-x Hf x P films were prepared via 2,3DTPT-assisted sol–gel spin coating method. • The Raman spectra confirmed the substitution of Hf dopant in the In cites. • The Hf dopant reduced the bandgap and displaced the quantum shoulder to IR-region. • The Hf dopant improved the absorbance and photoconductivity of InP films. • A photodiode was constructed and showed high response detection for infrared light. For the first time, highly crystalline In 1-x Hf x P ceramic films (0 ≤ x ≤ 0.09) were synthesized via a sol–gel spin coating technique assisted with 2,3-di(tetradecanoyloxy)propyl tetradecanoate for the selective detection of infrared light. The impact of the Hf dopant on the structure and topographical characteristics of the InP films was studied using X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and FTIR spectroscopy. As-synthesized In 1-x Hf x P ceramic films possess a cubic structure, in which Hf atoms replace In atoms in the InP crystals. The Raman spectra of In 1-x Hf x P ceramic films showed two sharp bands at 302 cm−1 and 344 cm−1 as a result of the first-order TO and LO phonon scattering, whereas two weak bands centered at 649 cm−1 and 691 cm−1 were assigned to the second-order 2TO and 2LO phonon scattering. The XPS spectra revealed that Hf4f occupied the In3d cites in the InP crystals. These films exhibited high optical absorption, good transparency and low reflectance. The inclusion of the Hf dopant in the InP films instigated a decrease of the bandgap from 1.62 eV to 1.44 eV and caused an increase of the optical conductivity and dissipation factor. A photodiode made of the In 0.91 Hf 0.09 P film was constructed. This photodiode could detect the infrared light with a response time of 1.3 s and a recovery time of 0.9 s. It also exhibited sensitivity of 0.36 mA/W.cm2 and showed high stability and reproducibility. Therefore, the inclusion of 9 wt% of the Hf dopant in the In cites of the InP crystals may pave the way to the development of highly efficient photodetectors for infrared detection. [ABSTRACT FROM AUTHOR]

Here, we have developed a new series of quantum dots based on the incorporation of thulium, Tm, atoms as efficient dopant in the cubic CdTe crystal structure for laser diode application potential. Therefore, Cd 1 − x Tm x Te (0 ≤ x ≤ 0.07) quantum dots were synthesized using s,s′-phenylenebis-ethynediyl-phenylene-bisthioacetate assisted microwave approach. The measurements of X-ray diffractions implied the preservation of the cubic phase of the CdTe crystals at all Tm dopant contents. The transmission electron microscopy inspected the formation of monodisperse and self-assemble nanoparticles with mean diameter from 1.8 ± 0.2 nm to 5.7 ± 0.3 nm, depending on the amount of Tm incorporated in the CdTe nanocrystals. A modulation of the optical bandgap was observed because of the doping of CdTe with Tm atoms. Highly luminescent emission spectra with tunable colors were obtained. The emission spectra showed sharp intense emitted light with an enhancement of its intensity reached to seven folds compared with the un-doped CdTe crystals. An increasing of quantum yields from 31% to 94% was realized. A decrease of the Stokes shift was observed which implies the synthesis of Cd 1 − x Tm x Te QDs free of defects for the first time. This unique performance renders the prepared Cd 1 − x Tm x Te to be potential candidate for the manufacturing of laser diodes. [ABSTRACT FROM AUTHOR]

Nanophotonic or nano-optic is sort of nanotechnologies that scrutinize the comportment of light on the scale of nanometer along with the interaction of nanoscale substances with light. The photonic semiconducting nanocrystals with distinctive optical traits became a prevalent category of optical probes and optoelectronic nanodevices. The modulation of photonic semiconducting nanomaterials turned out to be a crucial challenge for efficacious optical applications. Here, highly luminescent photonic semiconductors quantum dots were prepared using hydrothermal approach. The ytterbium,Yb, has been selected as doping atoms in the positions of Ni atoms in the NiO crystals. Different amounts of ytterbium, from 1 to 9 at.%, have been doped in the NiO. The stimulus of ytterbium atoms on the NiO crystal structures and the dimension of NiO crystals were explored via transmission electron microscope and X-ray diffractometer. The optical absorbance features comprised modulations of the optical band gaps, where the ytterbium dopant drifted the band gaps from 3.36 eV to 2.24 eV. The luminescent emission spectral property inspected a distinctive displacement of the emission spectra from UV-light to the red light with brilliant improve of the luminescent emission spectra by 8 folds and increasing the quantum yield by 7 folds. These marvel features boarded the opportunity of using the developed Ni x Yb 1-x O photonic crystals in the fields of wave guides, optical switches and optical amplifiers. [ABSTRACT FROM AUTHOR]

Here, we report for the first time the creation of Cd 1-x Os x Te (0 ≤ x ≤ 0.1) quantum dot using poly(9,9-dioctylfluorene-alt-benzothiadiazole) assisted polyol approach. The stimulus of osmium, Os, on the structure and optical emission behavior of CdTe quantum dots were examined. The X-ray diffraction measurement revealed the preservation of the cubic structures of CdTe crystals at all Os atoms concentration, implies the successful partial replacement of the Os atoms in the Cd cites. The transmission electron microscopy inspected that the doping of CdTe with Os atoms caused an increase of its particle diameter from 1.9 ± 0.2 nm to 7.1 ± 0.3 nm. The inclusion of Os atoms in the Cd atom cites instigated a shift to the red spectrum for both of the optical absorption/emission spectra. Astonishing upgrading of the luminescent intensities and a reduction of the width of emission spectra was achieved. An enlargement of the luminescent quantum yield from 31 % to 92 % was perfectly accomplished. A decreasing of the Stokes shift owing to the inclusion of Os atoms in the Cd cites, thereby a successful constraining of the crystal defects was realized. These outstanding demeanors may concrete an avenue to utilizing the developed Cd 1-x Os x Te semiconductor quantum dots for the fabrication of competent laser diodes. [ABSTRACT FROM AUTHOR]

New lasing QD nanostructures with intense emission spectra based on In 1-x Sc x P QD crystals were prepared via tetradecanoic acid assisted wet chemical route. The doping of Sc in the In 1-x Sc x P QD crystals instigated increasing of lattice constants and crystallites size of their zinc blende cubic crystals. The images of TEM scrutinized that the formed nanocrystal were highly monodisperse particles and their mean diameter increased from 2.8 nm to 5.9 nm. The images of HRTEM reflected that that the d-spacing increased from 0.583 nm to 0.62 nm upon the increasing of Sc dopant amount in the InP crystals. The spectrum of optical absorption curves showed a displacement toward the long wavelength as the amount of Sc dopants increased in the InP crystals, comprising the decrease of the optical gaps from 2.04 eV to 1.73 eV. The insert of Sc-dopant in the InP QDs inspected a shift of the emission spectra to red light, confirming the decrease of the optical and gap. Moreover, the inclusion of Sc atoms in the In atom cites of the InP QDs gave rise to an enlargement of the luminescent intensity of the emitted lights from these nanocrystals by 9 times. It is found a remarkable decreasing of the Stokes shift reached to 97 % was achieved, implying the surface defects were passivized. The increase of the Sc-dopant in the InP QD crystal resulted in a decreasing of the emission band width by 5 times. The quantum yields changed from 12 % to 78 % due the increasing of the amount of Sc dopant in the InP QD crystals. These outstanding behaviors make these sorts of novel QDs to be served as efficient lasing nanomaterials for the development of laser diode. [ABSTRACT FROM AUTHOR]

Cd 1-x Dy x Se nanocrystalline quantum dots were synthesized via cation exchange approach for the first time. The as-synthesized Cd 1-x Dy x Se nanocrystals showed a cubic phase at all Dy ion contents. The formed nanoparticles of the as-synthesized Cd 1-x Dy x Se nanocrystals were spherical like shape and their diameters increased from 2.1–7.3 nm with increasing the amount of Dy ions. The doping of CdSe with Dy atoms comprises a read shift of the optical absorption spectral curves. Therefore, a decrease of the optical band gap from 2.58 eV to 2.15 eV owing to the increase of Dy atoms took place. The partial substitute of the Cd atoms by Dy atoms instigated remarkable enhancing of the of luminescent intensities by eight order of magnitudes, made the PL peaks more sharper by four orders and achieved enlargement of the quantum yield to reach to value of 93 %. A decrease of the Stokes shift due to the doping by the Dy atoms was reasoned to the passivation of the defects. The enlargement of luminescence intensity, the creation of narrow emission band and the high quantum yield value empowered the as-synthesized Cd 1-x Dy x Se nanocrystals to be employed as laser materials for the manufacturing of multicolor laser diodes. [ABSTRACT FROM AUTHOR]

Here, we report about Zn 1-x Gd x O (0 ≤ x ≤ 0.09) semiconductor quantum dots synthesized via tetraethyl orthosilicate assisted colloidal regime for first time. The X-ray diffraction disclosed that the introduction of Gd ions in Zn sites of ZnO did not affect its hexagonal phase. The transmission electron microscopy divulged that the Gd ions caused an increasing of the particle size of Zn 1-x Gd x O QDs from 3 nm to 18 nm. The EDAX spectra inspected the stoichiometry and high purity of the synthesized Zn 1-x Gd x O QDs. The doping of ZnO QDs by Gd ions gives rise to a red shifting of the absorption and emission optical spectra. The doping of ZnO QDs by Gd ions instigates a reduction of the ZnO band gap from 3.3 to 2.8 eV. The doping of ZnO QDs by Gd ions improves the luminescence intensity, reduces the spectral width and suppresses the crystal defects. The quantum yield improved from 31% to 94%. These outstanding behaviors give rise to develop prohibitive superiority laser diode from the nanocrystalline Zn 1-x Gd x O semiconductor quantum dot. [ABSTRACT FROM AUTHOR]

Here, we report the influence of protactinium (Pa) on the optical behavior of ZnTe quantum dots. A nanocrystalline Zn 1-x Pa x Te (0 ≤ x ≤ 0.09) quantum dots prepared via poly[(9,9-bis(3′-(N,N- dimethylamino)propyl)-2,7-fluorene)-alt-2,7-(9,9-dioctylfluorene)] assisted microwave approach. The X-ray diffraction showed that the ZnTe crystal preserves their zinc blende cubic structure at all Pa ions concentrations. The transmission electron microscopy revealed that the Pa dopants lead to an increase of the QDs size from 2.9 ± 0.5 nm to 8.3 ± 0.2 nm. The doping of Pa ions in the ZnTe QDs gives rise to a red shift of the optical absorption and luminescence spectral peaks. A remarkable improvement of the luminescence intensity and a decrease of the luminescence spectral width take place as a result of the doping of ZnTe with Pa ions. The quantum yield improved from 37 % to 95 %. The Stokes shift decreases with the increase of the Pa ions, implying the inhibition of the crystal defects due to the decrease of the number of Zn2+ vacancies. These exceptional comportments may pave the way for developing high quality laser diodes based on Zn 1-x Pa x Te semiconducting crystalline quantum dots. [ABSTRACT FROM AUTHOR]

Nanocrystalline Zn 1-x Th x Se quantum dots have been prepared using mercaptoethanol assisted colloidal approach. The prepared Zn 1-x Th x Se QDs exhibited a cubic crystalline structure. The Zn 1-x Th x Se quantum dots showed uniform spherical shapes with size in the range of 2 to 6 nm. The optical absorption spectra were shifted to large wavelengths with increasing the amount of Th ions in the ZnSe structures. The optical band gap decreased from 3.18 nm to 2.84 nm with increasing the Th ions from 0 to 0.07 mol. The replacement of the Zn ions by Th ions lead to an improvement of the intensity of luminescence by five times, a decrease of the peaks width by three times and 91% an increase of the quantum yield. The Stokes shift decreased with the increase of the Th ions was argued the suppression of the crystal defects and number of Zn2+ vacancies in the ZnSe crystals. The high luminescence intensity, narrow band of emission and the high quantum yield may enable the developed Zn 1-x Th x Se QDs to be used for manufacture of laser diodes. [ABSTRACT FROM AUTHOR]

Abstract Highly crystalline Ni 1-x Ru x O films have been prepared via a pulsed laser deposition technique using a Q-switching Nd:YAG laser. The impact of the substitution of Ni2+ ions with Ru4+ ions on the lattice constants and sizes of the NiO crystals was explored by the X-ray diffraction. The surface topography and the grain growth at various Ru ion substitutions have been examined by the atomic force microscopy and scanning electron microscopy. The elemental composition was determined by the energy dispersive spectroscopy, while the influence of Ru ions on the Ni-O and O-O vibration modes was studied by the Raman spectroscopy. The optical properties were investigated by the UV–vis spectroscopy. The I-V characteristics, electrical resistivity, hole mobility and carrier concentrations have been measured. The developed films revealed optical transparency exceeding 97% along the visible region. These films showed a decrease of the optical bandgap from 3.4 to 2.8 eV as the Ru ion content increased from 0 to 10 at%. The doping of NiO with 10 at% of Ru ions causes a decrease of the resistivity to 5 × 10−5 Ω cm, an increase of the mobility to 210 cm2 V−1 s−1 and an increase of the carrier concentration to 3.8 × 1020 cm−3. These unique features make Ru-doped NiO films promising for a replacement of n-type ITO and FTO in optoelectronic applications. [ABSTRACT FROM AUTHOR]

Abstract Highly transparent and conducting Zn 1-x Ru x O films have been developed via mercaptopurine modified sol-gel spin coating approach as an efficient alternative for indium tin oxide electrodes. The crystalline structure and surface topography of the Zn 1-x Ru x O films have been explored by X-ray diffraction and SEM. The optical spectroscopy was monitored by ellipsometry. The data was fitted by Forouhi- Bloomer model and harmonic oscillator model. The increase of Ru amount in ZnO causes a decrease of the optical bandgap achieving the lowest value at 1 wt% of Ru dopant. The free carriers' concentration for this film reached to 1021 cm−3. The Zn 0.99 Ru 0.01 O film showed high transparency exceeds 95% and outstanding resistivity of 10−5 Ω cm along the whole visible spectrum region. These unique characteristics may open the road for developing novel, cost-effective and highly transparent and conducting metal oxide electrodes for the future of optoelectronic applications. Highlights • Zn 1-x Ru x O thin films are prepared via mercaptopurine modified sol-gel approach. • An optical transparency reached to 96% was obtained. • An outstanding resistivity of 10−5 Ω cm was achieved. • These films may be used as efficient alternatives for ITO and FTO. [ABSTRACT FROM AUTHOR]

Abstract The opportunity of using electrons' spin rather than electrons charge has shown much eagerness for the future application in information technology. The success to create spin-polarized charge carriers into the semiconductor metal oxides can bring significant advantages in data storage devices. Here, a novel chemical recipe was developed to grow Zn 1-x Co x O thin films via Dimethyl pimelimidate dihydrochloride (DMP) modified spin-coating approach. The impact of Co ions (0.01 ≤ x ≤ 0.09) on the lattice constants, bond lengths, residual stress and the volume of unit cell of the ZnO crystal lattice was investigated. The X-ray photoelectron spectroscopy is served for investigating the oxidation states of the Zn and Co ions. It was found that the cobalt ions are incorporated in the ZnO crystals in the form of Co2+. The magnetic hysteresis of the developed thin films was detected by the vibrating magnetometer (VSM). The developed films revealed ferromagnetism with magnetic moment of 1.69μ B /Co and coercivity of 135 G at x = 0.03. However, high optical transparency reached to 85% and high photoconductivity exceeded 5 times the un-doped films, was achieved. The developed synthetic method enhanced the magneto-optical behaviors of the Zn 1-x Co x O films compared to the used conventional techniques which enable them to be employed as efficient materials for the optical data storage and optical spintronic devices. Highlights • Zn 1-x Co x O thin films are prepared via DMP modified spin-coating approach. • The Co ions caused a change of the bond length and residual stress of ZnO. • A ferromagnetism with moment of 1.69μ B /Co achieved at 3% Co ions. • Optical transparency and photoconductivity exceeded 5 times the ZnO film is achieved. • These films may be used for the optical data storage and optical spintronic devices. [ABSTRACT FROM AUTHOR]

Here, we report, for the first time, the solution growth of n-type MgFe 2 O 4 spinel ferrite nanoparticles on nano-textured p-type silicon (100) substrate. Water soluble MgFe 2 O 4 spinel ferrite nanoparticles are prepared by polyol technique. The MgFe 2 O 4 spinel ferrite nanoparticles were characterized by transmission electron microscopy both at low and high resolution, selected area electron diffraction, energy dispersive spectroscopy, and Raman spectroscopy. The texturing of the surface of the Si(100) substrate to create well-organized nanopillar-like shapes was carried out by a nanosecond laser lithography technique. The water soluble MgFe 2 O 4 spinel ferrite nanoparticles were deposited on the textured Si(100) substrate. The sample was characterized by scanning electron microscopy and X-ray diffraction. The charge carriers transport mechanism was discussed in terms of the variation of the barrier height under the exposure to various gases. A comparison between the MgFe 2 O 4 spinel ferrite nanoparticles grown on planar and textured p-type Si(100) surfaces showed that the latter demonstrated an improvement of gas sensitivity and accelerated response time. These two characteristics, combined with high performance stability, make these sensors promising for practical applications. [ABSTRACT FROM AUTHOR]

Here, we report the development of the solar cell with a hybrid p-n junction based on poly(3,4-ethylene dioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) deposited on the textured Si surface. Texturing was accomplished by a laser processing technique, allowing the formation of nanopyramids on the Si surface, leading to ultralow reflectance. The PEDOT:PSS solution was deposited on the textured Si-wafer via a spin-coating technique. The evaluation of the I–V characteristics under illumination demonstrated an improvement of the short-circuit current density of the PEDOT:PSS/textured nanopyramid Si-substrate by 61% compared to that of the device based on the planar Si-substrate. The effect of the nanopyramid aspect ratio (height/diameter) of the textured Si-substrate on the optical absorption and reflection was studied to determine the optimum aspect ratio to achieve the maximum rate of the light entrapment. It was demonstrated that the increase of the aspect ratio leads to an enhancement of the short-circuit current and the filling factor. The hybrid device developed shows a promise for future applications in photovoltaic solar cell devices. [ABSTRACT FROM AUTHOR]

The Cr-doped InP quantum dots (In 1-x Cr x P, 0 ≤ x ≤ 0.09) have been synthesized by a solvothermal method using In and Cr acetylacetonates and tris(1-pyrrolidinyl)phosphine as precursors. A combination of X-ray powder diffraction, transmission electron microscopy (TEM), high resolution TEM along with selected area electron diffraction and energy dispersive spectroscopy demonstrates that the increase of the Cr content in the InP nanocrystals (which is consistent with the increased Cr acetylacetonate loading) leads to a decrease of the quantum dot size, an increase of their monodispersity, and a decrease of lattice constants although the zinc blende InP crystal structure is preserved. The changes in the sizes and structure of the Cr-doped InP quantum dots result in the change of optical properties. The incorporation of Cr into the InP structure allows one to control the band gap of the InP nanocrystals in a wide range and leads to enhanced photoluminescence with high quantum yields. Thus, varying the Cr content one can design the InP quantum dot size and structure as well as their optical properties making it a considerable advance in the development of novel optical materials. [ABSTRACT FROM AUTHOR]

Nanocrystalline In 1−x Cu x P thin films (0 ≤ x ≤ 0.5) have been deposited on quartz substrates by a Metal-Organic Chemical Vapor Deposition (MOCVD) technique. The effect of the copper ion content on the structural crystal lattice, morphology and optical behavior of the InP thin films was assessed using X-ray diffraction, scanning electron microscopy, atomic force microscopy, Raman spectroscopy and spectrophotometry. All films exhibited a crystalline cubic zinc blende structure, inferring the solubility of the Cu atoms in the InP crystal structure. The XRD patterns demonstrated that the inclusion of Cu atoms into the InP films forced the nanoparticles in the films to grow along the (1 1 1) direction. The AFM topography showed that the Cu ions reduce the surface roughness of deposited films. The Raman spectra of the deposited films contain the first and second order anti-stoke Γ TO , Γ LO , Χ LO + Χ TO , 2Γ TO , and Γ LO + Γ TO bands which are characteristic of the InP crystalline structure. The intensities of these bands decreased with increasing the content of the Cu atoms in the InP crystals implying the creation of a stacking fault density in the InP crystal structure. The In 1−x Cu x P thin films have shown high optical transparency of 90%. An increase of the optical band gap from 1.38 eV to 1.6 eV was assigned to the increase of the amount of Cu ions in the InP films. The In 0.5 Cu 0.5 P thin film exhibited remarkable optical conductivity with very low dissipation factor which makes it a promising buffer window for solar energy applications. [ABSTRACT FROM AUTHOR]

Copper oxide nanoparticles loaded Poly(vinylidene fluoride) (PVDF) nanocomposites, at concentrations from 1 to 9 wt%, were developed by casting technique. The effect of the Cu 2 O nanoparticles on the structure, thermal, mechanical and dielectric properties of the PVDF were inspected. The scanning electron microscopy (FE-SEM) revealed the well dispersion of the Cu 2 O nanoparticles into the PVDF matrix up to 5 wt%. The X-ray diffraction (XRD) patterns and the infrared spectroscopy (FTIR) measurements implied that the inclusion of the Cu 2 O nanoparticles into the PVDF matrix leads to a transform of the non-polar semi-crystalline α-phase of the neat PVDF to highly crystallized polar β-phase. Moreover, an increase of the thermal stability and crystallinity of the PVDF after the incorporation of the Cu 2 O nanoparticles was achieved. The Cu 2 O/PVDF nanocomposites exhibited excellent cyclic mechanical property compared to the neat PVDF. The introduction of 5 wt% Cu 2 O nanoparticles into the PVDF composites resulted in remarkable increase of the dielectric constant by 13 times while the dielectric loss was very low. A device based on Al/5 wt% Cu 2 O doped PVDF/Pt structure is developed. This device shows ferroelectric hysteresis with butterfly like shape and exhibited remanent polarization of 11.2 μC/cm 2 with coercive field of 49 MV/m. These superior properties enable the developed Cu 2 O/PVDF nanocomposite films to be a potential candidate in the field of ferroelectric organic electronic memory devices. [ABSTRACT FROM AUTHOR]

Here, we report the synthesis of Cr 2 O 3 nanoparticles via ethylene glycol assisted microwave approach. Thin films of Cr 2 O 3 nanoparticles doped Poly(vinylidene fluoride) (PVDF), at a variety concentrations (0.01–0.09 wt%), were prepared by spin-coating technique on quartz substrate with thickness of 200 nm. The influence of the concentrations of Cr 2 O 3 nanoparticles on the structural, morphological, optical and dielectric properties of the PVDF is examined. The optical properties of the Cr 2 O 3 /PVDF thin films were examined by the ellipsometry and fitted by Forouhi–Bloomer model. The doping of PVDF by 0.05 wt% of Cr 2 O 3 nanoparticles showed an enhancement of the index of refraction compared to the neat PVDF. A remarkable enhancement of the dielectric constant was achieved when the PVDF film doped with 0.05 wt% of Cr 2 O 3 nanoparticles with 35 orders of magnitude compared to the neat PVDF film, owing to the Maxwell–Wagner–Sillars polarization effect. This results in an enhancement of the ferroelectric properties of the PVDF by increasing its remnant polarization from 8.7 μC/cm 2 to 12.1 μC/cm 2 . These superior properties may enable the developed Cr 2 O 3 /PVDF films to be a potential candidate in the field of organic ferroelectric random access memory junctions. [ABSTRACT FROM AUTHOR]

The chlorine intercalated Mg-Al layered double hydroxides (Mg-Al-Cl-LDH) with chemical formula of Mg 1−X Al X (OH) 2 Cl − X were successfully prepared by the one step mechanochemical activation and hydrothermal methods. For a comparative study of the mechanically activated samples versus hydrothermally treated specimens, the structural features such as crystallite size, lattice strain, crystallinity, the interlayer spacing, and the unit cell volume of samples were examined. Results revealed that the phase purity of products was strongly influenced by different ion substitution degrees ( X = 0.12, 0.18, 0.3, and 0.42). From X-ray diffraction (XRD) analysis, Brucite and Hydrotalcite were dominant phases at low ions substitution ( X ), while Gibbsite and Hydrotalcite were main peaks at high ions substitution ( X ) for both methods. Pure Hydrotalcite was obtained in the midrange. The unit cell volume and interlayer spacing of LDH obtained from both processes was also strongly influenced by degrees of substitutions so that it shows a downward trend as ion content increased. FESEM and TEM observations revealed that that the LDH powders possesses a typical platelet-like microstructure, so that the average crystallite size of hydrothermal samples was greater than milled samples. Detailed analysis of the phase behavior and structural trends revealed that Mg-Al-Cl-LDH can be synthesized much more easily and rapidly in high energy ball mill as compared with an analogous LDH prepared by hydrothermal method. However, the product obtained from hydrothermal method showed the greater crystallinity. [ABSTRACT FROM AUTHOR]

Two reliable approaches for estimating the number of atomic planes of graphene films grown on Si substrate were demonstrated by Raman and ellipsometry spectroscopies. The first approach depends on the measurement of the ratio of the integrated Raman scattering intensity of the graphene G band to the optical phonon band of Si substrate (I G /I Si ). The second approach belongs to ellipsometry measurement of the ratio of the amplitude of the reflected polarized light from the surface of the graphene films to the amplitude of reflected polarized light from the surface of the Si substrate (Ψ G /Ψ Si ). These two approaches could efficiently recognize the number of atomic planes in the graphene films (1 ≤ n ≤ 10). The results were compared with atomic force microscopy (AFM) measurement and showed a linear regression with slope of 0.36 ± 0.01 nm/graphene layer. The Two approaches will open a new avenue to efficiently count the number of graphene layers during the preparation process. [ABSTRACT FROM AUTHOR]

Direct growth of a monolayer graphene film on a quartz substrate by a hot filament chemical vapor deposition technique is reported. The monolayer graphene film prepared was characterized by Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), selected area electron diffraction (SAED), and atomic force microscopy (AFM). The optical properties were studied by spectroscopic elliposmetry. The experimental data were fitted by the Forouhi-Bloomer model to estimate the extinction coefficient and the refractive index of the monolayer graphene film. The refractive index spectrum in the visible region was studied based on the harmonic oscillator model. The lattice dielectric constant, real and imaginary dielectric constants and the ratio of the charge carrier number to the effective mass were determined. The surface and volume energy loss parameters were also found and showed that the value of the surface energy loss is greater than the volume energy loss. The determination of these optical constants will open new avenue for novel applications of graphene films in the field of wave plates, light modulators, ultrahigh-frequency signal processing and LCDs. [ABSTRACT FROM AUTHOR]

Highlights: [•] Zn1−xCu x O films based modified methoxy ethanol sol–gel dip-coating was synthesized. [•] Interstitial substitution of copper ions by zinc ions has been achieved. [•] Forouhi–Bloomer model fitted well the ellipsometric spectra. [•] The optical constants were estimated from spectroscopic ellipsometric data. [•] The VELF was larger than SELF at all incident photon energies. [Copyright &y& Elsevier]

Abstract: Nanocrystalline copper doped zinc oxide thin films were prepared via a modified 2-methoxyethanol sol–gel dip-coating technique at various concentrations of copper in the range 0–5wt%. The X-ray diffraction analysis confirmed the copper doped zinc oxide hexagonal wurtzite structure. The copper ions interstitially substitute zinc ions in the hexagonal structure which resulted in the decrease of the crystallite size from 25nm to 16nm. A decrease in the lattice parameters was observed up to 2wt% of copper ions followed by an increase. Scanning electron microscopy showed a homogenous distribution of the prepared films along the glass substrates. Energy dispersive spectroscopy confirmed the stoichiometry and high purity of the prepared films. The optimum optical band gap was achieved at 2wt% of the copper ion concentration. The prepared films showed a high transparency in the visible region with an average value of 89%. The I–V characteristics showed Ohmic behavior up to 3V. The electrical resistivity showed a lowest value (0.2Ωcm) for the film doped with 2wt% of copper. [Copyright &y& Elsevier]

Highlights: [•] Mercapto hexanoic acide functionalized InP QDs have been prepared. [•] These QDs doped into polyaniline via electropolymerization technique. [•] The hole transport was monitored by lifetime decay and time of flight methods. [•] High conversion efficiency about 3.1% was obtained at thickness of 157nm. [Copyright &y& Elsevier]

Abstract: Indium phosphide semiconductor quantum dots are of significant heed as their applications encompass a spacious concatenation in LEDs and solar cells technologies. For improving their serviceable prominence, there is a real demand for a fashion that furnishes prompt and large mass production of mightily monodispersed nanoparticles. This study conveys an efficacious and fast recipe of generating substantially monodispersed InP quantum dots via water based route technique using a novel surfactant. Herein, InP QDs have been prepared using 6-mercaptohexanoic acid for achieving an effective surface passivation of monodispersed InP QDs with highly luminescence at temperature 50°C. The as prepared quantum dots were investigated by transmission electron microscopy, luminescence spectroscopy, and X-ray diffraction. The XRD depicted that the InP quantum dots have a cubic zinc blend structure. TEM image revealed that the prepared quantum dots are monodispersed and their average particle size of about 4nm. Energy dispersive X-ray spectroscopy confirmed the existence of organic ligand as a shell around InP nanoparticles. Time resolved spectra depicted that the capping agent passivated the InP QDs surface and enhanced the luminescence emission. [Copyright &y& Elsevier]

Abstract: Phase change Ga15Se77Ag8 chalcogenide thin films were prepared by thermal evaporation technique. Thin films were then irradiated by Transverse Electrical Excitation at Atmospheric Pressure (TEA) nitrogen laser for different time intervals. The X-ray structural characterization revealed the amorphous nature of as-prepared films while the laser irradiated films show the polycrystalline nature. Field Emission Scanning Electron Microscope (FESEM) has been used to study the structural changes. The results are discussed in terms of the structural aspects and amorphous to crystalline phase change in Ga15Se77Ag8 chalcogenide thin films. The observed changes are associated with the interaction of the incident photon and the lone-pairs electrons which affects the band gap of the Ga15Se77Ag8 chalcogenide thin films. The optical constants of these thin films are measured by using the absorption spectra measurements as a function of photon energy in the wavelength region 400–1100nm. It is found that the optical band gap decreases while the absorption coefficient and extinction coefficient increases with increasing the laser-irradiation time. The decrease in the optical band gap has been explained on the basis of change in nature of films, from amorphous to polycrystalline state. The dc conductivities and activation energies of these thin films are also measured in temperature range 313–393K. It has been found that the activation energy in Ga15Se77Ag8 thin films decreases whereas the dc conductivity increases at each temperature by increasing the laser-irradiation time. [Copyright &y& Elsevier]

Nanocrystalline semiconducting quantum dots have drawn paramount attention as efficient materials for the next-generation optoelectronic devices owing to their multiple generations of excitons, tunable optical band gap and high absorption coefficient. For improving the optical, luminescence and electronic characteristics of quantum dots, Cd 1− x Nd x Se (0 ≤ x ≤ 0.09) nanocrystalline QDs were successfully synthesized via 6-mercaptopurine assisted wet chemical approach for the first time. The morphological shapes and crystal structures of the developed nanocrystals were characterized by transmission electron microscope and X-ray diffractions. However, the impact of Nd ions on the optical behavior, the optical band gap, and the valence band and the conduction band levels of the Cd 1− x Nd x Se (0 ≤ x ≤ 0.09) nanocrystalline QDs were evaluated. The luminescence, quantum efficiency as well as quantum yield were studied. A remarkable enhancement of the luminescent emission and narrow band emission was achieved. The quantum yield enhanced from 35% to 91%. Such unique demeanor embark the opportunity to use these novel series of Cd 1− x Nd x Se (0 ≤ x ≤ 0.09) nanocrystalline QDs as efficient materials for quantum dot sensitized solar cells as well as light emitting devices with high quality. [ABSTRACT FROM AUTHOR]

Semiconducting Zn 1-x Ta x O nanophotonic crystals were synthesized via Di-N-(2-hydroxyethyl)oleylamin assisted microwave approach using tantalum acetylacetonate, zinc acetylacetonate and 8-ethylquinoline N-oxide. The developed Zn 1-x Ta x O nanophotonic crystals exhibited a hexagonal crystalline structures and their lattice constant increased with increasing Ta atoms. The Zn 1-x Ta x O nanostructures demonstrated emission spectrum in the visible region from 354 to 430 nm. The inclusion of Ta atoms in the ZnO QDs enhanced the luminescent light and the quantum yields for ZnO nanocrystals by five orders at concentration of 5 wt%. The change of the power and time of microwave irradiation for the Zn 0.95 Ta 0.05 O nanocrystals instigated shift of the luminescence peak positions toward blue light and a modulation of the optical band gap. The increase of the microwave power to 850 W for 35 min for Ta-doped ZnO at concentration of 5 wt% comprised a remarkable increase of the luminescence intensity 7 times, decreased the emission band width by 5 times and enlarged the quantum yield to 92 %. These outstanding features may render the Zn 0.95 Ta 0.05 O nanocrystals to be used as laser material for the laser diode applications. [ABSTRACT FROM AUTHOR]

The large-scale production of graphene via a simple approach is the key factor to be introduced into the industrial applications such as energy conversion, storage materials and optical electronics. In this letter, a rapid and facile approach to synthesize high quality graphene layers with large mass production has been developed. The method depends on the intercalation of graphite flakes with tartaric acid. The treated graphite subjected to a thermal shock at 750 °C for 60 s and followed by solvothermal treatment in the presence of isopropanol at 400 °C for 2 h. The produced graphene layers have an average thickness of 0.53 nm which depicted the production of a monolayer graphene. The FT-IR and Raman spectroscopy confirmed that the produced graphene layers have very low surface defects compared to reported approaches. The XPS spectra revealed that the surface of the produced graphene layers contains only 6 at% oxygen, which is better than the reduced graphene by conventional methods. This novel approach will open a new avenue for a scalable production of high quality graphene monolayer. [ABSTRACT FROM AUTHOR]

Highlights: [•] γ-Fe2O3 nanocubes assemblies were prepared by using oxidosqualene. [•] The nanocubes showed a high monodispersion with FC cubic structure. [•] The nanocubes have a high saturation magnetization of 62emu/g. [•] The nanocubes exhibited high magnetic anisotropy density compared to bulk material. [ABSTRACT FROM AUTHOR]

Abstract: Phase transformation kinetics in Ga25Se75−x Sb x glasses have been determined by non-isothermal differential scanning calorimetric measurements at heating rates of 5, 10, 15, 20 and 25K/min. The values of glass transition (T g) and crystallization temperature (T c) are found to be composition and heating rate dependent. The activation energy of crystallization and glass transition have been determined from the dependence of T c and T g on the heating rate. Thin films of Ga25Se75−x Sb x glasses have been prepared by vacuum evaporation technique with thickness 400nm. These thin films were crystallized by thermal annealing and laser-irradiation. The phase change phenomena have been studied by measuring optical absorption of as-prepared and crystallized thin films in the wave length region 400–900nm. The optical absorption data indicate that the absorption mechanism is non-direct transition. Optical band gap values decrease with increase in Sb contents in Ga–Se as well as with increase in annealing temperature and laser-irradiation time. The optical band gap is shifted due to crystallization by annealing/laser-irradiation. As the phase of the films changes from amorphous to crystalline, a non sharp change of the optical band gap is observed. This gradual decrease in optical band gap was explained to be a result of an amorphous–crystalline phase transformation. [Copyright &y& Elsevier]

Abstract: This study demonstrates the feasibility of improving the performance of a quantum dot (QD) intermediate band solar cell (SC) by capping an InGaAs layer on the InAs QDs and inserting GaAs spacer layers. For comparison, a GaAs reference SC of the same p-i-n structure but without InAs QDs is grown. The two devices were grown by solid source molecular beam epitaxy (SS-MBE) on epiready (001) n+-GaAs substrates and the InAs QDs structure is highly stacked and well-aligned. The two SCs were investigated by sepectroscopic ellipsometry (SE), in the photon energy range of 1–6eV, photoluminescence (PL) and photo-absorption measurements. The two major spectral features observed in the dielectric function spectra of the InAs QDs SC at ∼3eV and ∼4.5eV are attributed to the E 1 and E 2 critical point structures of GaAs and InAs, respectively. The PL spectrum of the InAs QDs in the GaAs matrix is higher and presents an asymmetric shape, which indicated the growth of a high-quality multistacked InAs QDs structure and the contribution of larger and relatively smaller QDs to PL spectrum. The electrical conversion at the infrared range of λ=850–1300nm for the InAs QDs SC is demonstrated by photocurrent spectra. The enhanced absorption performance (up to 1280nm) of the QDs SC was attributed to the optical absorption from InAs QDs, wetting layer and InGaAs layer of the InAs/InGaAs/GaAs QD heterostructure. [Copyright &y& Elsevier]

Abstract: The effects of composition and thermal annealing in between glass transition and crystallization temperature on the optical and structural properties of Ga25Se75−x Te x were investigated. The glass transition and crystallization temperature of the synthesized samples was measured by non-isothermal DSC measurements. Amorphous thin films of Ga25Se75−x Te x glasses were grown onto ultra clean glass/Si wafer (100) substrates using the vacuum evaporation technique. The effect of thermal annealing on the optical gap (E g) for Ga25Se75−x Te x thin films in the temperature range 358–388K is studied. As-prepared and annealed thin films were characterized by X-ray diffraction, field emission scanning electron microscopy, energy dispersive X-ray spectroscopy and optical absorption. Thermal annealing was found to be accompanied by structural effects, which in turn, lead to changes in the optical constants. The optical absorption coefficient (α) for as-deposited and thermally annealed films was calculated from the absorbance data. From the knowledge of absorption coefficient at different wavelengths, the optical band gap (E g) was calculated for all compositions of Ga25Se75−x Te x thin films before and after thermal annealing. Results indicate that allowed indirect optical transition is predominated in as-deposited and thermally annealed thin films. The influence of Te incorporation and thermal annealing in Ga25Se75−x Te x thin films results in a gradual decrease in the indirect optical gap, this behavior can be explained as increased tailing. The decrease in optical band gap and an increase in absorption coefficient and extinction coefficient with thermal annealing can be attributed to transformation from amorphous to crystalline phase. [Copyright &y& Elsevier]