Nano Thin Films Research Articles

Synthesis, characterization, and conditions optima for thin film assembly of a light lanthanide nanocomplex

A light lanthanide thin film nanocomplex of Ce(III) with 2-mercaptopyridine-3-carboxylic acid (MPC) was synthesized via the layer-by-layer self-assembly (LbL-SA) chemical deposition method. The synthesized nanolanthanide complex was subjected to a number of analytical measurements to characterize and confirm its structure such as elemental analysis, electron impact mass spectra, FT-IR spectra, and UV–Vis spectra. The morphology and structure of the thin films of MPC ligand and its Ce(III) nanocomplex (CeMPC) were inspected with scanning electron microscopy. The nanothin films of CeMPC were subjected to X-ray powder diffraction analysis. The thermal decomposition of CeMPC nanothin films was studied and discussed. The thermal decomposition included seven steps. The optima of various controlling conditions for thin films of CeMPC nanocomplex assembly via LbL-SA were investigated and discussed.

Performance of a Nano PbS/Si Hetrojunction Deposited by Chemical Spray Pyrolysis

Deposition of polycrystalline Lead sulfide nanothin films onto Si and glass substrates at temperatures (200-300 °C) was carried out by chemical spraying route using optimized preparative conditions. The XRD pattern confirmed the formation of PbS semiconducting films with orthorhombic structure. The electrical and optical properties of the nanocrystalline thin films were studied aiming to better understanding for the electrical and opto-electrical properties of a hetrojunction with p-type Si. It was found that, the average grain size of PbS in the films was between 4 nm and 7 nm. The band gap was also calculated from the absorption co-efficient curves and showed a blue shift due to the grain size of the nanoPbS in the films. The current-voltage (I-V) and photoresponse characteristics were obtained with different illumination intensities. The detector exhibits an evident wide-range spectral responsivity

Performance of a Nano PbS/Si Hetrojunction Deposited by Chemical Spray Pyrolysis

Deposition of polycrystalline Lead sulfide nanothin films onto Si and glass substrates at temperatures (200-300 °C) was carried out by chemical spraying route using optimized preparative conditions. The XRD pattern confirmed the formation of PbS semiconducting films with orthorhombic structure. The electrical and optical properties of the nanocrystalline thin films were studied aiming to better understanding for the electrical and opto-electrical properties of a hetrojunction with p-type Si. It was found that, the average grain size of PbS in the films was between 4 nm and 7 nm. The band gap was also calculated from the absorption co-efficient curves and showed a blue shift due to the grain size of the nanoPbS in the films. The current-voltage (I-V) and photoresponse characteristics were obtained with different illumination intensities. The detector exhibits an evident wide-range spectral responsivity

Gap separation effect on thermoacoustic wave generation by heated suspended CNT nano-thinfilm

Completely suspended nano-thinfilms (NTFs) can be fabricated by drawing carbon nanotube (CNT) arrays in an open space. These NTFs have been identified as an excellent source for generating powerful thermoacoustic waves. However, NTFs are widely known to be structurally weak and that vulnerable structural stability poses a great threat and challenge to their applications in practical devices. By suspending NTFs on a substrate, the structural stability can be significantly reinforced. In this paper, an analytical model for the thermoacoustic pressure response of suspended NTFs, which are fabricated by suspending a nano-thinfilm on a substrate, is established and the model is validated by comparing with experiment. The influence of gap separation between thinfilm and substrate on the acoustic pressure response can be analyzed using the analytical model. By comparing with completely suspended NTFs in an open space, the performance of a suspended-on-substrate NTF is far more efficient if the gap separation is within a few micrometers. In addition, the new analytical model developed here also reports the acoustic pressure response in different surrounding gaseous media. The effect of substrate thermal properties on the performance of such suspended NTF devices is also analyzed theoretically. In general, the analytical model is expected to provide effective guidelines for further design optimization analysis using such thermoacoustic devices.

Vinculin focal adhesion of osteoblast‐like cells on PEEK coated with ultra‐thin polymer nano films

ABSTRACTPEEK is the polymer of choice to replace metal encapsulants and other parts in active medical implants fixated into bone. The current challenge is to improve its biocompatibility with bone tissue to ultimately achieve osseointegration. PEEK sheets surfaces coated with plasma deposited nano thin polymer films using CH4, (CH4 + O2) and (CH4 + N2) gases. PEEK samples plasma treated with nonpolymerizing gases (O2) were also used for comparison. The adhesion performance of osteoblast like cells on the plasma‐treated PEEK surfaces and the presence of Vinculin in these cells were evaluated after long culturing period (12 days). X‐ray photoelectron spectroscopy and Auger spectroscopy were used to provide surface molecular information, surface hardness and molecular density. All plasma‐treated surfaces retained functionality after the sterilization process. PEEK surfaces with high number of oxygen functional groups and particularly oxygen rich thin polymer coating (plasma deposition using CH4+O2 gas mixture) resulted in strong cellular adhesion strength and large Vinculin amount. Further, osteoblast‐like cells responded better to surfaces with lower molecular density acting like another signal for cell adhesion. The osteoblast‐like cells response was weaker for surfaces with both thin films with nitrogen functional groups and nonfunctional (nonpolar) films. Furthermore, thin films rich in nitrogen functional groups repelled the cells, showed abnormal cells shape, smaller Vinculin amount and induced thicker cellular clusters with poor spread. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42181.

Thickness dispersion of surface plasmon of Ag nano-thin films: determination by ellipsometry iterated with transmittance method.

Effective optical constants of Ag thin films are precisely determined with effective thickness simultaneously by using an ellipsometry iterated with transmittance method. Unlike the bulk optical constants in Palik's database the effective optical constants of ultrathin Ag films are found to strongly depend on the thickness. According to the optical data two branches of thickness dispersion of surface plasmon energy are derived and agreed with theoretical predication. The thickness dispersion of bulk plasmon is also observed. The influence of substrate on surface plasmon is verified for the first time by using ellipsometry. The thickness dependent effective energy loss function is thus obtained based on this optical method for Ag ultrathin films. This method is also applicable to other ultrathin films and can be used to establish an effective optical database for ultrathin films.

High-performance In filled CoSb3 nano thin films fabricated by multi-step co-sputtering method

In filled CoSb3 thin films with various In content were prepared on flexible substrates by multi-step co-sputtering method, which provided a promising way to prepare low-cost and high performance thin films. The influence of In content on the microstructure and thermoelectric properties of the CoSb3 based thin films are systematically investigated. The thin film transforms from P-type to N-type with the increasing of In content. Both of the electrical conductivity and the Seebeck coefficient of the thin films increase after In filled. The thermal conductivity of the In filled thin film significantly decreases and the ZT value of the In-filled thin films are much higher than that of the unfilled thin film. It can be observed that the In filled thin films are single CoSb3 phase and the grain size increases after In filled. The average grain size of all the thin films are less than 50nm, indicates the thin films are nano-particles structure.

Trace moisture detection in oil filled transformer by ceramic sensor

This paper reports on the suitability of thin film nano porous γ-alumina sensor for sensing parts per million (ppm) moisture present in transformer oil. Transformer oil degrades slowly by weathering, causing dielectric break down voltage of the oil to fall down. For improving this break down voltage, water must be removed from the transformer oil. Flash point of the transformer oil ranges from 150°C to 200°C.When the oil is slowly heated up to 75°C water vapour comes out from oil which is detected by ceramic sensor. The sensor is prepared from organo-metallic precursor by sol-gel process. Gold coated α-alumina substrate was dipped within the alumina hydra-sol and a thin film of γ-alumina formed on the substrate. The sensor capacitance was measured as a function of ppm moisture level. The circuit produces an output voltage which is precisely related to the absolute value of the capacitance of the dielectric material. In order to improve the sensitivity, parallel electrode structure was patterned on the nano porous dielectric. The response is sufficiently linear in extremely low ppm level moisture. A prototype hygrometer was built for detection of trace moisture in transformer oil. Porous alumina can be produced at a relatively low cost and in a variety of structural configurations. Sol- gel processing of alumina allows superior control on pore morphology, phase formation, purity and product microstructure compared to the more traditional techniques like Anodic oxidation of alumina sheets, tape cast by different sizes of alumina powder etc.

Photoluminescence of nanocrystalline ZnS thin film grown by sol-gel method.

Nano and polycrystalline ZnS thin films play a crucial role in photovoltaic technology and optoelectronic devices. In this work, we report the photoluminescence (PL) characterization of nanocrystalline ZnS thin films synthesized by dip coating method. The PL spectra exhibit broad nature with multiple emission peaks which are due to the different defect levels in the prepared film.

Synthesis and characterization of LiFePO4 cathode preparation by low temperature method

We review in detail the physics and technology of the novel material LiFePO4, a potential cathode material for Li-ion batteries. In the present work, nano crystalline LiFePO4 film has been synthesized in both powder and thin film forms from a non-aqueous sol–gel synthesis route based on oxalates of Li and Fe (II). Ferrous oxalate has been synthesized indigenously using a ferrous sulphate based chemical reaction and characterized. Nano powders and thin films of LiFePO4 have been fabricated and coated on stainless steel substrates with the aim of device development in future. The material has been characterized extensively by XRD for crystal structure, FESEM for microstructure, EDS for elemental analysis and FTIR for the internal modes of phosphate ion. Fe3+ impurity characterization has been done by using ESR.

1H Solid-State NMR Study of Nanothin Nafion Films

The unique behaviors of Nafion nanothin films with thicknesses of 10 nm (ultrathin) and 160 nm (thin) were evaluated using variable-temperature and variable-humidity solid-state 1H NMR spectroscopy. These unprecedented measurements of nanothin films stacked within an NMR rotor represent a remarkable experimental achievement and demonstrate that 1H NMR spectroscopy of such minute amounts of ionomer might be possible within active catalyst layers in polymer electrolyte fuel-cell electrodes. This study was motivated by the observation, in a separate work, of thickness-dependent and highly suppressed conductivity in nanothin films of Nafion (4–300 nm) compared to counterpart free-standing Nafion membranes. Trends in the line width and, more precisely, the T2 relaxation, as probed using a Hahn echo, showed that the local mobility within the hydrogen-bonded domain is equivalent for 10 and 160 nm films and is governed by the fast exchange limit in terms of NMR time scales. Subtle differences in the chemical shif...

Process model-based analysis of highly crystalline and chemically pure molecular beam epitaxy of MgO (111) nano-thin films on 6H-SiC (0001) substrates

A highly two-dimensional and chemically pure MgO (111) thin film grown epitaxially under ultra-high vacuum on a (√3 × √3) R30° reconstructed wideband gap 6H-SiC (0001) substrate surface can serve as a promising minimal mismatch interfacial layer between the substrate surface and a crystalline structure of functional oxide film. However, the reliability and repeatability of the growth process is challenging. In this paper the dynamic termination of the MgO (111) polar oxide during layer-by-layer growth is explained by OH group chemical bonding state of MgO structure. The analysis of causal relationships is conducted at three different thickness levels to account for the sensitivity of film chemistry to the mismatching strain related inherent twist of crystalline structure along the film thickness. The contribution of sources of the undesired bonding states is quantified by examining the process sensitivity trends to the most critical process variable (percentage starting oxygen) at different thickness levels.

Introducing a high gravity field to enhance infiltration of small molecules into polyelectrolyte multilayers.

Loading functional small molecules into nano-thin films is fundamental to various research fields such as membrane separation, molecular imprinting, interfacial reaction, drug delivery etc. Currently, a general demand for enhancing the loading rate without affecting the film structures exists in most infiltration phenomena. To handle this issue, we have introduced a process intensification method of a high gravity technique, which is a versatile energy form of mechanical field well-established in industry, into the investigations on diffusion/infiltration at the molecular level. By taking a polyelectrolyte multilayer as a model thin film and a photo-reactive molecule, 4,4'-diazostilbene-2,2'-disulfonic acid disodium salt (DAS), as a model small functional molecule, we have demonstrated remarkably accelerated adsorption/infiltration of DAS into a poly(allylamine hydrochloride) (PAH)/poly(acrylic acid) (PAA) multilayer by as high as 20-fold; meanwhile, both the film property of the multilayer and photoresponsive-crosslinking function of DAS were not disturbed. Furthermore, the infiltration of DAS and the surface morphology of the multilayer could be tuned based on their high dependence on the intensity of the high gravity field regarding different rotating speeds. The mechanism of the accelerated adsorption/infiltration under the high gravity field was interpreted by the increased turbulence of the diffusing layer with the thinned laminar boundary layer and the stepwise delivery of the local concentration gradient from the solution to the interior of the multilayer. The introduction of mechanical field provides a simple and versatile strategy to address the paradox of the contradictory loading amount and loading rate, and thus to promote applications of various membrane processes.

Effect of Post-Annealing on the Properties of Eu Doped ZnO Nano Thin Films

Europium (Eu) doped nanostructure ZnO thin films are prepared by using spray pyrolysis technique. The ZnO:Eu thin films are deposited at a substrate temperature of 623K on glass substrates, using europium nitrate as a Eu source. The as-prepared ZnO:Eu films are annealed in air at 673K and 723K for 1h. The effect of post-annealing on the structural, electrical and optical properties of the films has been studied. XRD measurements show that all the films are nanocrystallized in the hexagonal wurtzite structure and exhibit a preferential orientation along (002) plane, the intensity of preferentially oriented (002) peak is apparently improved. The resistivity of annealed film is larger than the as-deposited. ZnO:Eu film annealing at 723K for 60min exhibits lowest resistivity of 3.62×10-4Ω cm. In addition, the ZnO:Eu film shows good optical transmittance of 94%.

Structural, optical and magnetic properties of Ni-doped CdS thin films prepared by CBD

Room-temperature ferromagnetic behavior of undoped cadmium sulphide (CdS) and Ni-doped CdS thinfilms prepared by chemical bath deposition technique is reported. The crystallite sizes of the thinfilms have been characterized by X-ray diffraction pattern. The particle sizes increase from 11 to 40 nm with the increase of Ni content in the CdS thinfilms. scanning electron microscope results indicated that CdS thinfilms is made up of aggregate of spherical-like particles. The composition was estimated by Energy dispersive analysis of X-ray and reported. Spectroscopic studies revealed considerable improvement in transmission and the band gap of the films decreased from 2.62 to 2.28 eV with addition of Ni dopant that is associated with variation in crystallite sizes in the nano regime. Magnetization measurements indicate that the Ni doped CdS thinfilms exhibited ferromagnetism and the saturation magnetization decreases with the increase of crystal sizes in the Ni doped CdS nano thinfilms. This finding in CdS thinfilms should be focus of the future electronic and spintronics devices.

A new sol–gel processing routine without chelating agents for preparing highly transparent solutions and nanothin films: engineering the role of chemistry to design the process

The great sensitivity of titanium alkoxides to hydrolysis makes their sol–gel transformation very fast and thus difficult to control. A method was proposed to alleviate this drawback. Preparation of highly transparent solutions and nanothin films is another objective of the present research. Employing nanoemulsion method and optimizing the processing conditions, a clear solution of well-dispersed nanosized particles was obtained. With the proposed process BaTiO3 precursor sols and nanothin films with enhanced optical transparency towards the visible were prepared. The optimal formulation of the sol consists of acetic acid, barium acetate, 2-propanol, TTIP and deionized water with 6:1:1:1:150 M ratios, respectively. It was found that the reduction of the temperature in the initial stage of mixing of precursors controls the size of the forming species and accordingly improves the stability and transparency of the sol. The results also showed that the applied modifications and optimizations significantly downsize the particles within the sol to the nanometric scale and accordingly result in a significant improvement in the optical response of the products.

Preparation of ZnO nanoparticles by different pulsed laser energy

Zinc oxide nano thin films were deposited on conducting Fluorine Tin Oxide (FTO) coated glass by RF-magnetron sputtering under different deposition time and exposed different laser energy. The XRD analysis revealed the uniform preferential growth along the (002) of ZnO films and exhibited the hexagonal wurtzite type structure with good crystallinity. The energy gap of the deposited ZnO films was in the range of 3.36eV and 3.38eV for 15 and 45min deposition time, respectively. The triangle ZnO nanoparticles formed a homogenous film on the substrates without any discontinuities which was exhibited from the SEM micrographs. AFM images proved that grain size and Ra decreased but Rsk, Rku and Rdq increased for samples with different deposition times. After laser exposure with different energy the optimum grain sizes were 180 and 170nm at 50mj laser energy for 15 and 45min deposition time, respectively.

ChemInform Abstract: Metal—Metalloporphyrin Frameworks: A Resurging Class of Functional Materials

AbstractReview: 112 refs.

Behavior of charges locally injected into nanothin high-k SmScO3 dielectric

The behavior of charges locally injected from the probe of an atomic force microscope into nanothin films of high-k SmScO3 dielectric deposited on a silicon substrate is studied by the method of Kelvin probe force microscopy. Prior to examination, the films were annealed at different temperatures. At temperatures above 900°C, the amorphous as-prepared films exhibit polycrystalline inclusions. In the films annealed at 900°C, the injected charge persists for a long time that several tens of times exceeds the charge retention time observed when conventional dielectrics, such as SiO2 and Si3N4, are used. In addition, the diffusion of carriers in the plane of the dielectric layers sharply slows down.

Influence of gas flow on structural and optical properties of ZnO submicron particles grown on Au nano thin films by vapor phase transport

ZnO submicron particles were grown on Au-catalyzed Si substrates using a vapor phase transport (VPT) growth process under different mixture gas ratios at a growth temperature of 900°C. The structural and optical properties of the ZnO submicron particles were investigated using field-emission scanning electron microscopy (FE-SEM), x-ray diffraction (XRD), and photoluminescence (PL). The ZnO submicron particles were clustered for the O2/Ar mixture gas ratios (%) higher than 10%, which was largely determined by the ambient gas. In particular, for an O2/Ar mixture gas ratios of 30%, ZnO submicron particles with diameters between 125–500 nm were observed; in addition, the narrowest XRD full width at half maximum (FWHM) values and PL spectra with 0.121° and 92 meV were reported. The structural and optical properties of the ZnO submicron particles improved as the O2/Ar mixture gas ratio was increased, as observed from the XRD and PL spectra results.