Properties Of Nanostructured Thin Films Research Articles

Investigation of Physical Properties of Nanostructured Selenium-Based Compound Semiconductors

The study of physical properties of compound semiconductors plays a vital role in the device fabrication point of view. Different investigations suggest that one can tune these properties by impurity dopants, irradiation techniques, adopting different synthesis techniques, etc. In this study, the physical properties of nanostructured thin films of Se–S compound were tuned by different Hg dopant concentrations. X-ray diffraction spectra clarify the preferred crystallite growth occurs in the cubic phase of the corresponding Bravi’s crystal system. The particle size calculated from Bragg’s reflection spectra by using Scherrer’s analytical formula illustrates an enhancement of crystallite size in highly concentrated Hg-doped sample. Similar consequences are found in surface morphological micrographs. The optical band gap reduced from 1.65[Formula: see text]eV to 1.54[Formula: see text]eV on increasing the doping concentration of Hg, according to the computed optical parameters using optical transmission spectra in the wavelength range 200–1100[Formula: see text]nm. The thin-film refractive index dispersion data fits well in accordance with the single oscillator model. Investigation of electrical properties tells that there is significant improvement in electrical conductivity in highly concentrated Hg-doped samples. Therefore, the apparent tuning as observed in the physical properties of the investigated material may have practical uses in industry for a variety of optoelectronic devices.

Anisotropic optical properties of indium tin oxide thin films prepared by ion beam sputtering under oblique angle deposition

Unraveling the anisotropic optical properties of nanometer-scale structured thin films is of great interest for both fundamental and applicative perspectives, but can be challenging and is therefore generally overlooked, especially for transparent and conducting materials. In this paper, porous slanted columnar thin films of indium tin oxide are prepared under Oblique Angle Deposition (OAD) by Ion Beam Sputtering (IBS) using argon and xenon as process ions. Their anisotropic optical properties are investigated both in the Visible–NIR range (400nm to 1.7μm) and the Infrared range (1.7 to 30μm) by means of Mueller Matrix Spectroscopic Ellipsometry. The optical models and their results are confronted to and confirmed by High Resolution Transmission Electron Microscopy (HRTEM) studies. In the Visible–NIR range, the resulting picture is that of a ripple-like structure with greater optical index in the direction perpendicular to the slanting plane. This configuration is quite original for OAD films, for which the optical index is usually greater in the direction parallel to the columns, and appears to be a specific footprint of IBS due to the enhanced diffusion of the species during deposition. In the Infrared range, the strong optical anisotropy observed for the Xe-deposited films is explained by the anisotropic free-carrier scattering inside the nanoscopic sub-columnar structure evidenced by HRTEM, yielding to a biaxial Drude model. This mechanism is highly original for OAD films, and may be of a great help to elucidate the anisotropic optical properties of other OAD metallic systems, for which such a sub-columnar structure appears to be a general trend. More generally, this work proposes an original and thorough method combining advanced optical modeling and transmission electron microscopy studies to unravel the anisotropic optical properties of nanostructured thin films.

Electrochemical, Optical and Morphological Characterizations of Cu Doped ZnO Nanostructure Thin Films Prepared by Spin Coating Method

From nanotechnology point of view where conductivity is crucial, although it is essential to determine the electrochemical properties Cu doped ZnO nanostructure thin films produced by spin coating, there are rare studies in the literature. Therefore, in this study, the aim was to examine thouroughly the electrochemical properties of nanostructure thin films which were grown on glass substrates by using a facile and cost-effective spin coating method. The effects of the dopant on the morphological, optical and electrochemical properties of ZnO nanostructure thin films doped with Cu at different concentrations (0-50%) were investigated by SEM, XRF, FTIR, UV-vis, mechanical profilometer, and cyclic voltametry. The absorption spectra of the samples revealed that the energy band gap value decreased by the incereasing of Cu doping concentration. SEM images depicted that more spherical and homogeneous nanostructures formed with the doping of Cu. Electrochemical results showed that increasing the Cu doping ratio in ZnO nanoparticles results in higher electron transfer indicating that the conductivity of ZnO nanostructured thin films increases with Cu doping. It can be concluded that it is possible to produce more homogeneous, wider spectrum absorption capable and more conductive nanostructure thin films by a simple and inexpensive method. It is envisaged that the thin films obtained are promising for a wide range of nanotechnology applications.

Preparation and optical properties of nanostructure thin films

Preparation and optical properties of nanostructure thin films

Photo‐Induced Self‐Cleaning and Wettability in TiO2 Nanocolumn Arrays Obtained by Glancing‐Angle Deposition with Sputtering

AbstractIn this work, the preparation of regular nanosized columnar structures of titanium dioxide by means of glancing angle deposition with magnetron sputtering (MS‐GLAD) followed by thermal annealing is reported. MS‐GLAD gives rise to metallic titanium columnar structures with regular width and length that after thermal treatment are fully oxidized to form TiO2 nanocolumns that maintain the morphological features of the original metallic ones. Further functionalization with gold by means of multiple ion cluster source results in well‐dispersed Au nanoparticles across the nanocolumns’ surface with a narrow size distribution centered at ca. 8.5 nm. The obtained nanostructures show photocatalytic self‐cleaning activity as shown by the elimination of an organic layer deposited on their surface and the detection of hydroxyl radicals. Photoelectrochemical measurements show a better charge separation at the Au/TiO2 interface. In addition, wettability studies show that the degree of hydrophobicity of the surface is increased by the presence of nanocolumns, both in the dark and under UV illumination. This behavior is not modified by the presence of Au nanoparticles on the surface. The obtained results open up interesting implications in the tunability of the properties of nanostructured thin films for this kind of photo‐activated application.

Engineering of colloidal nanocrystal thin films and their optoelectronic properties: A simple and effective route

This work investigates the effect of heat treatments on CdSe/CdS core–shell nanocrystals assemblies with different sizes and capping ligands. Nanostructured thin films, consisting of an array of CdSe quantum dots embedded in a continuous matrix of CdS, have been obtained by mild thermal treatments of CdSe/CdS core–shell nanocrystals deposited on glass substrates from colloidal solution. These materials are regarded as promising photon upconverters, or absorbers for high-efficiency photovoltaic devices. The treatments were conducted in the range 300–550 °C for up to 150 min. The nanoscale evolution during the heat treatment was investigated by monitoring optical properties of the films. Initially, the well-defined photoluminescence band, corresponding to the first quantum dots exciton state, rapidly shifts towards lower energy, indicating delocalization of the exciton and suggesting that nanocrystal CdS shells are merging by sintering mechanisms, thus forming a continuous matrix. Control over this phase of the heat treatment leads to the desired nanoscale morphology and properties. The kinetics of sintering has been characterized, and the procedure has been systemically applied to CdSe/CdS nanocrystals of different sizes and ligand types. This research provides novel values for the activation energy of the sintering process and strongly support the general applicability of such process to control and optimize optoelectronic properties of nanostructured thin films for applications like light-emitting diodes, tunable emitters and photoconductors among others.

New challenges of femto-nanophotonics: basic principles and possible applications

The possibility of controlling the functional properties of nanostructured thin films of different topology and elemental composition deposited on solid substrates by laser radiation is under our study. Quantum-correlated states that emerge in the deposited granular nanocluster semiconductor/metal structures lead to both hopping/tunneling electroconductivity and specific optical properties. An increase in electrical conductivity (by several orders of magnitude) is observed in experiments depending on the surface and boundary conditions in various topologically organized cluster systems. The high-temperature superconductivity tendency in such nanocluster structures that are both stable and can give rise to different (non-phonon) electron pairing mechanisms is discussed. New optical effects were observed in such topological structures as well.

Piezoelectric Thin Films of ZnO-Nanorods/Nanowalls Grown by Chemical Bath Deposition

This study presents a comparison of the piezoelectric properties of nanostructured thin films made of arrays of vertically oriented ZnO-nanorods (ZnO-NRs) over ITO-glass substrate and of ZnO-nanowalls (ZnO-NWs) over aluminium substrate. Both nanostructures were synthesized on a large area through chemical bath deposition. The morphological, structural, and chemical characteristics of the produced nanostructures were investigated in order to assess the crystal quality and purity. To this purpose, we used different techniques, such as field-emission scanning electron microscopy, atomic force microscopy, energy dispersive x-ray analysis, powder x-ray diffraction, x-ray photoelectron spectroscopy, and photoluminescence spectroscopy. Moreover, the piezoelectric response of the nanostructured films was assessed through piezoresponse force microscopy. This technique was employed to obtain a quantitative evaluation of the piezoelectric coefficient ( ${d_{33}}$ ) of the film. We obtained ${d_{33}}$ values as high as (7.01 ± 0.33) pm/V for ZnO-NRs and (2.63 ± 0.49) pm/V for ZnO-NWs films.

Electrophysics of nanocluster thin-film systems: Achieving superconducting topological states

The possibility of controlling the functional properties of nanostructured thin films deposited on solid substrates using lasers stems from the different topology and elemental composition of the deposited materials. Quantum-correlated states that emerge in the deposited granular nanocluster semiconductor/ metal structures lead to hopping/tunneling conductivity. The possibility of high-temperature superconductivity in such nanocluster structures that are both stable and can give rise to different (nonphonon) electron pairing mechanisms is discussed. An increase in electrical conductivity (by several orders of magnitude) is observed in experiments, depending on the surface and boundary conditions in various topologically organized cluster systems. The problem is to find the optimum numerical relations between the topological parameters in order to obtain the patterns of directivity (such as the Bragg resonance) needed for a sharp increase in electrical conductivity in selective directions.

Effect of gamma irradiation on structural, electrical and optical properties of nanostructure thin films of nickel phthalocyanine

A thermal evaporation technique at room temperature and in a vacuum of 10−4Pa has been used to prepare deposit thin films of nickel phthalocyanine. The prepared samples were irradiated at room temperature with absorbed doses 100, 200 and 300kGy. Thin films have been identified before and after irradiate by X-ray diffraction and Fourier transformation infrared. It was found that the films have nano-size structure; also the films have a radiation resistance up to 300kGy gamma dose.The optical properties of as deposited and irradiated thin films were investigated by spectrophotmetric at wavelength range 200–2500nm. The optical constants were calculated for as deposited and irradiated thin films. The optical energy gaps and oscillator energy of samples decrease with increase gamma ray doses, while the dispersion energy, lattice dielectric constant, high frequency dielectric constant and N/m* increase with increasing gamma.

Comparative study of the mechanical properties of nanostructured thin films on stretchable substrates

Comparative studies of the mechanical behavior between copper, tungsten, and W/Cu nanocomposite based on copper dispersoïd thin films were performed under in-situ controlled tensile equi-biaxial loadings using both synchrotron X-ray diffraction and digital image correlation techniques. The films first deform elastically with the lattice strain equal to the true strain given by digital image correlation measurements. The Cu single thin film intrinsic elastic limit of 0.27% is determined below the apparent elastic limit of W and W/Cu nanocomposite thin films, 0.30% and 0.49%, respectively. This difference is found to be driven by the existence of as-deposited residual stresses. Above the elastic limit on the lattice strain-true strain curves, we discriminate two different behaviors presumably footprints of plasticity and fracture. The Cu thin film shows a large transition domain (0.60% true strain range) to a plateau with a smooth evolution of the curve which is associated to peak broadening. In contrast, W and W/Cu nanocomposite thin films show a less smooth and reduced transition domain (0.30% true strain range) to a plateau with no peak broadening. These observations indicate that copper thin film shows some ductility while tungsten/copper nanocomposites thin films are brittle. Fracture resistance of W/Cu nanocomposite thin film is improved thanks to the high compressive residual stress and the elimination of the metastable β-W phase.

Morphology, optical and AC electrical properties of nanostructure thin film of bromo indium phthalocyanine

Sandwich devices of bromo indium phthalocyanine (BrlnPc) thin films with aluminium electrodes were deposited on polyborosilicate substrate, using electron beam gun evaporation technique at room temperature. The AC electrical properties of nanostructure thin films (Al/BrInPc/Al) were examined in the temperature range of 303–393K and frequency (f) between 102 and 105Hz. Structural and optical behaviour of samples were investigated by scanning electron microscope (SEM) images, X-ray diffraction (XRD) micrograph and optical absorption. Capacitance increase with increasing temperature for frequencies <103Hz and is almost independent of temperature for the range of frequencies >103Hz. Dissipation factor decrease with increasing frequency to a minimum value and increased noticeably thereafter. The AC electrical properties of nanostructured thin films of our materials are in agreement with the model of Goswami and Goswami. The band theory and hopping mechanism are applicable in explaining the conduction process for the frequency range of f<103Hz and f>103Hz, respectively.

Negative Magnetoresistance of Indium Tin Oxide Nanoparticle Thin Films Grown by Chemical Thermolysis

To clarify the electrical transport properties of nanostructured thin films, tin-doped indium oxide (ITO) nanoparticle (NP) solution-processed films were fabricated. An air-atmosphere, simple chemical thermolysis method was used to grow the ITO NPs, and the structural and electrical properties of spin-coated granular ITO NP films were investigated. X-ray diffraction measurements showed clear observation of the cubic indium oxide (222) diffraction peak, and films with a smaller Sn concentration were shown to have a better crystalline quality. We further explored the physical origin of the sign of the magnetoresistance (MR) in the variable-range hopping (VRH) region. A negative MR under a magnetic field perpendicular to the film surface increases with decreasing Sn concentration, and these results can be explained by the forward interference model in the VRH region. A larger negative MR is attributed to longer localization and hopping lengths, and better crystallinity. Thus, ITO NP thin films produced by th...

Optical and electrical properties of nanostructured heterojunction (Au|PdPc|ClAlPc|Al) and using as O2sensor

Nanostructure thin films and sandwich devices of palladium phthalocyanine (PdPc) and chloro-aluminum-phthalocyanine (ClAlPc) were prepared by thermal evaporation technique. Optical and struc- tural properties of nanostructure thin films were investigated by XRD, SEM and optical absorption. The SEM images demonstrated PdPc (40–60 nm) and ClAlPc (30–50 nm) nanostructures. XRD pat- terns showed that thin films are in α-phase at room temperature. Also, optical bandgap energy of thin films was calculated by optical absorption spectra. Heterojunction (Au|PdPc|ClAlPc|Al) and single layer (Au|PdPc|Al and Au|ClAlPc|Al) devices were fabricated. Electrical measurements demonstrated the semi-conducting and photo-conducting behavior of thin films. After that, devices were exposed to different concentrations of O2 at 300 K and 350 K and conductivity of thin films was increased on exposure to O2 . Heterojunction devices were more sensitive than other thin films and had better response and reversibility in comparison with single layer devices at 350 K. Finally, 10% O2 was mixed with different percentages of relative humidity and all results showed that the conductivity of thin films is reduced on exposure to O2 mixed to humidity.

Gas Sensing Properties of Interconnected ZnO Nanowires

In this report, the structural, morphological, and gas-sensing properties of nanostructured thin films made of interconnected zinc oxide (ZnO) nanowires were studied. This paper is the first demonstration of functional devices based on such nanowires. Interconnected nanowires were grown via a two-stage process using, spray pyrolysis for the deposition of a ZnO seed layer on glass substrates, followed by a hydrothermal method for the growth of interconnected ZnO nanowires. Samples were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) techniques. Characterization of the films revealed that they were populated with interconnected ZnO nanowires, approximately ~20-30 nm in width with a hexagonal wurtzite structure after heat treatment. Samples were evaluated for NO2 gas sensing applications, and exhibited a considerable change in surface conductivity when exposed to N O2 at 200 °C. The influence of temperature between 65-260 °C on N O2 response of the developed sensors will be presented and discussed.

Effects of paste storage on the properties of nanostructured thin films for the development of dye-sensitized solar cells

The effects of paste storage on the properties of nanostructured thin films were investigated in the present study. To this aim, dye-sensitized solar cells were fabricated using nanostructured TiO 2 thin films and an organic dye as a sensitizer. Aggregation of TiO 2 nanoparticles was observed when paste was stored until deposition affecting film's porosity and surface roughness factor and as a consequence, reducing the efficiency of the solar cells. On the other hand, fewer cracks were developed during the drying process of the film when stored paste was used for film deposition instead of freshly prepared paste. This is due to the presence of large pores on films with significant particle agglomeration, which enhance evaporation of acetyl acetone and water, thereby reducing cracks. The development of cracks on the film's surface results to a decrease in the efficiency of the cell, albeit a slight one. One of the main aims of the present study was also the investigation of different methods for developing counter electrodes, as the properties of the counter electrodes can affect the efficiency of the solar cells considerably. Counter electrodes were prepared by two different methods, namely by electrodeposition using an aqueous solution of H 2PtCl 6 (0.002 M) and by thermal decomposition of H 2PtCl 6 from isopropanol (5 mM). Electrodeposited counter electrodes were found to present several advantages over electrodes prepared by thermal decomposition, such as increased photocurrent, reduced sheet resistance, as well improved fill factor for the resulting solar cell.

Characterization of elastic properties of nanostructured thin films by X-rays

Characterization of elastic properties of nanostructured thin films by X-rays

Effect of precursor sol's aging on properties of nanostructured thin films with coexistent CeO 2 and CeTi 2O 6 phases

Thin films constituting CeO 2 and CeTi 2O 6 phases have been deposited using a solution of cerium chloride heptahydrate and titanium propoxide in ethanol. The effect of sol's aging on different properties of the films has been discussed. X-ray diffraction and transmission electron microscopic investigations have shown the coexistence of CeO 2 and CeTi 2O 6 phases in these films. Fourier transform infrared studies have affirmed increased bond strength of Ti–O network in the films as a function of sol's aging. Optical transmittance is observed to be higher in the aged sol films. Scanning electron microscopy study has illustrated that the aged sol leads to compact films with lesser porosity. Photoluminescence (PL) intensity in the films has shown dependence on sol's aging with the films deposited from the aged sol exhibiting low PL activity. The decomposition of eosin (yellow) under UV–visible light irradiation in the presence of CeO 2–CeTi 2O 6 films shows the presence of photoactivity in these films. Compared to TiO 2 films, the CeO 2–CeTi 2O 6 films have exhibited better photocatalytic response. Electrochemical investigations have revealed superior response in the aged sol films. Ion storage capacity and diffusion coefficient for Li ions in the aged sol films is measured to be greater. The higher transmission modulation of WO 3 film configured with the aged sol CeO 2–CeTi 2O 6 film demonstrates the potential of the latter films as a promising counter electrode in electrochromic windows.

D-78 Elastic Properties of Nano-Structured Thin Films: Characterization and Modeling

An abstract is not available for this content so a preview has been provided. Please use the Get access link above for information on how to access this content.

Influence of Grain Size and Humidity on the Nanotribological Properties of Wear-Resistant Nanostructured ZrO2 Coatings: An Atomic Force Microscopy Study

The nanotribological properties of nanostructured thin films of tetragonal ZrO2 on oxidized Si (100) were studied as a function of grain size and relative humidity (RH) by atomic force microscopy. The nanostructured ZrO2 showed a 50% decrease in friction coefficient μ compared with oxidized Si (100) in dry nitrogen atmosphere and 40% RH. A maximum of μ was observed at ca. 40% RH for both samples, while there were insignificant differences in μ for ZrO2 samples with grain sizes between 12 and 30 nm. The good tribological properties open the possibility for nanostructured zirconia to be applied as wear-resistant, low friction coatings on various materials.