Nano Thin Films Research Articles

Modification of Novel Conductive PEDOT:Sulfonated Polyimide Nano-Thin Films by Anionic Surfactant and Poly(vinyl alcohol) for Electronic Applications

Conductive poly(3,4-ethylenedioxythiophene):sulfonated polyimide (PEDOT: SPI) nanoscale thin films were successfully developed by addition of anionic surfactant and poly(vinyl alcohol) (PVA) for potential application in electronic devices. In this work, sodium dodecyl sulfate (SDS) surfactant was introduced into PEDOT:SPI aqueous suspensions to improve the dispersion stability of the particles in water, leading to high transparency and low contact angle of PEDOT:SPI thin films. All of the conducting polymer thin films showed high transparency of more than 85% transmission. Conductivity enhancement and good film-formation properties of PEDOT:SPI were achieved by adding various amounts of PVA to each polymer aqueous suspension because of the resulting conformational changes. The highest conductivity of 0.134 S/cm was achieved at 0.08 wt.% PVA in PEDOT:SPI2/SDS/PVA film, increased by a factor of 3.5 compared with the original material. In addition, PVA also improved the thermal stability of the conductive films, as verified by thermogravimetric analysis (TGA). The interactions between conducting polymers, PVA, and SDS surfactant affecting nano-thin film properties were revealed and investigated. Moreover, the interactions between SDS and SPI were proven to be different from those between SDS and poly(styrenesulfonate) (PSS) in conventional PEDOT:PSS solutions.

Effect of complexing agent TEA: The structural, morphological, topographical and optical properties of FexSx nano thin films deposited by SILAR technique

Iron sulfide thin films (FexSx) (x=0.05M, 0.10M, 0.15M, 0.20M and 0.25M) were deposited by SILAR method from equimolar and equivolume aqueous solutions of ferrous nitrate and sodium sulfide with the addition of complexing agent TEA. The structural, morphological and optical characteristics of the films were derived from X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM) and UV–vis spectral techniques. The mixed characteristics (crystalline and amorphous) of the deposited films and the increasing crystalline qualities with the concentrations were understood from the XRD analysis. The grain sizes and roughness of the films were decreases with the increasing concentration and also at the higher concentration films are shown by the same images presence of hexagonal like crystallite structure. The influence of complexing agent TEA on the surface roughness and morphological properties are confirmed by the atomic force microscope (AFM) results. The effect of increasing substrate concentration on the absorption and transmission measurements and its impact on the optical band-gap energy were enumerated from the UV–vis analysis.

Sticky nano-thin films for the adhesion of polymers

Nanometre thick size films (about 2nm thick) that were plasma deposited using a mixture of polymerizing and non-polymerizing gases on a PEEK polymer surface resulted in a remarkable autohesive strength (up to 10 fold when compared with the untreated control). Experimental results on autohesion of semi-crystalline PEEK surfaces treated with plasma immersion ion implantation and deposition (PIIID) showed exceptionally strong autohesive bonds in lap-shear testing. Electron spin resonance (ESR) showed that the radical concentration increased linearly with plasma bias voltage. X-ray photoelectron spectroscopy (XPS) measurements showed no correlation between autohesive bonding strength and the concentration of oxygen and nitrogen elements and or the concentration of CO functional groups on the surface. Contact angle measurements showed that surface energy also showed no correlation. Bond strength values are linked with the percentage of the sp3 components of the C 1s region fitting in XPS spectra. There was strong relationship between the plasma treatment bias voltage and the plasma generated free radical density in the deposited thin film. Bond strength values are also correlated with the percentage of the sp3 components of the C 1s region fitting in XPS spectra. Free radicals induced covalent bonding might be suggested as the major contributor that leads to that the remarkable increase of the adhesion strength.

Effect of the Growth Parameters on Nonlinear Optical Properties of Al‐Doped ZnO Nano Films

The objective of this research work is to provide a systematic method to perform test and evaluation on the nonlinear optical properties of Al‐doped ZnO nano thin film structure for designing a high‐performance optical‐electronic structure. Some different kinds of samples can be manufactured for testing. The samples are designed by changing technical parameters such as sputtering power of Al and ZnO, pressure and sputtering time and each parameter has three levels. The test results show that the main factor is the sputtering power of Al, which means the doping density of Al. In the meantime, the Maxwell–Garnett theory is used to investigate the optical prosperities of Al‐doped ZnO nano thin films in the visible range. The optical band gap of Al‐doped ZnO nano thin films increases with the increasing of Al doping density, but it becomes slowly when the doping density is more than 16.0%. The results and the investigation method are useful for designing and manufacturing for nano thin films.

Ferroelectric domains and diffuse transitions in ultrathin films of PbTiO3: Effects of strain and electrodes

We determine strain-temperature phase diagrams that map the stability of ferroelectric ordering and domains in nanothin (1.6-20 nm) films of PbTiO${}_{3}$ using molecular dynamics based on a first-principles model Hamiltonian. The ferroelectric domain structure is shown to depend sensitively on the epitaxial strain and the nature of the electrodes that screen the surface charges of a ferroelectric. We show that a broad peak in the dielectric response as a function of temperature marks a diffuse transition to a flux closure stripe-domain structure in the ultrathin films with incomplete screening of charges at their interface with the electrode. We demonstrate that the strain-phonon coupling is fundamental to the stability and topology of such a domain structure, which can be engineered at the nanoscale with a suitable choice of electrodes and substrate, and used in ultrahigh-density memory chips.

Effects of the addition of anionic surfactant during template polymerization of conducting polymers containing pedot with sulfonated poly(imide) and poly(styrene sulfonate) as templates for nano-thin film applications

Herein, the addition of an anionic surfactant, sodium dodecyl sulfonate (SDS), during the template polymerization of conducting polymers to improve the nano-thin films properties was investigated. In order to compare the effects, three methods of addition SDS were demonstrated: addition of SDS during template polymerization, addition after template polymerization, and addition of both during and after template polymerization. Sodium dodecyl sulfonate (SDS) was utilized as a stabilizer and a dopant for the polymerization of 3,4-ethylenedioxythiophene (EDOT) with two different templates, sulfonated poly(imide) (SPI) and polystyrene sulfonate (PSS). The addition of SDS during polymerization of both PEDOT-SPI and PEDOT-PSS was more effective in stabilizing particles against coagulation, significantly reducing the sizes of conducting particles, forming stable spherical particles, and enhancing thermal stability and conductivity. Evidence from FTIR measurements indicated that molecular interactions between SDS and PEDOT chains resulted in the decrease in distortion of the structures and in the effectiveness of doping of the PEDOT chains. TEM and TGA analyses further showed that SDS molecules were intercalated in conducting particles when they were added during polymerization. The addition of SDS during template polymerization of PEDOT demonstrated a greater effect on colloid stability and intercalation doping than that of the addition of SDS after polymerization, resulting in significant conductivity improvements of PEDOT-SPI and PEDOT-PSS films.

An In-situ Real-Time Optical Fiber Sensor Based on Surface Plasmon Resonance for Monitoring the Growth of TiO2 Thin Films

An optical fiber sensor based on surface plasmon resonance (SPR) is proposed for monitoring the thickness of deposited nano-thin films. A side-polished multimode SPR optical fiber sensor with an 850 nm-LD is used as the transducing element for real-time monitoring of the deposited TiO2 thin films. The SPR optical fiber sensor was installed in the TiO2 sputtering system in order to measure the thickness of the deposited sample during TiO2 deposition. The SPR response declined in real-time in relation to the growth of the thickness of the TiO2 thin film. Our results show the same trend of the SPR response in real-time and in spectra taken before and after deposition. The SPR transmitted intensity changes by approximately 18.76% corresponding to 50 nm of deposited TiO2 thin film. We have shown that optical fiber sensors utilizing SPR have the potential for real-time monitoring of the SPR technology of nanometer film thickness. The compact size of the SPR fiber sensor enables it to be positioned inside the deposition chamber, and it could thus measure the film thickness directly in real-time. This technology also has potential application for monitoring the deposition of other materials. Moreover, in-situ real-time SPR optical fiber sensor technology is in inexpensive, disposable technique that has anti-interference properties, and the potential to enable on-line monitoring and monitoring of organic coatings.

Patterned Permalloy and Barium Strontium Titanate Thin Film Enabled Tunable Slow Wave Elements for Compact Multi-Band RF Applications

We have designed and proposed tunable slow wave RF elements enabled with patterned Permalloy (Py) and barium strontium titanate (BST) nano thin films. A slow wave element structure with discontinuous signal width is designed and implemented in an IBM 45 nm CMOS technology. Effects of pitch length and signal width ratio on slow wave effects are discussed. Inductance variations of Py embedded transmission lines for different dc levels are studied, and capacitance variations of BST thin film are investigated and measured. Results show that the designed slow wave element can have both 2:1 inductance and capacitance tuning ratio with 50 mA dc current and 5 V voltage applied respectively. Multi-band, multi-functionality RF components with miniaturized size can be achieved using this design.

The effect of different gas atmospheres on the structure, morphology and photoluminescence properties of pulsed laser deposited Y3(Al,Ga)5O12:Ce3+ nano thin films

Luminescent properties of Y3(Al,Ga)5O12:Ce3+ phosphor powder and thin films were obtained. The phosphor powder was used as target material for Pulsed Laser Deposition (PLD) of the thin films in the presence of different background gases. Excitation peaks for the powder were obtained at 439, 349, 225 and 189 nm and emission peaks at 512 and 565 nm. X-ray diffraction indicated that better crystallization took place for films deposited in a 20 mTorr O2 atmosphere. Atomic force microscope revealed an RMS value of 0.7 nm, 2.5 nm and 4.8 nm for the films deposited in vacuum, O2 and Ar atmospheres, respectively. The highest PL intensity was observed for films deposited in the O2 atmosphere. A slight shift in the wavelength of the PL spectra was obtained for the thin films due to a change in the crystal field. The thickness of the films varied from 120 nm to 270 nm with films deposited in vacuum having the thin layer and those in Ar having the thick layer. The stoichiometry of the powder was maintained in the film during the deposition as confirmed by Rutherford backscattering spectroscopy.

An investigation on high-temperature electrical transport properties of graphene-oxide nano-thinfilms

High-temperature electrical transport properties are investigated for graphene-oxide nano thinfilms. The graphene-oxide nanoparticles are synthesized by modified Hummers method and characterized by UV–vis, Raman and X-ray diffraction techniques. The surface morphology of graphene-oxide film is analyzed using scanning electron and atomic force microscopy. The experimental results on high-temperature electrical studies of thinfilms exhibit metallic behavior followed by three-dimensional variable range hopping mechanism. The current–voltage characteristics at various temperatures (from 293K to 573K) were investigated. The effect of high-temperature on the functional groups of graphene-oxide film is evidently examined using X-ray photoelectron, thermal gravimetric analysis and Fourier transform infra-red spectroscopy. Transistor characteristics were performed after heat treatment resulting ambipolar behavior with holes and electron mobility of 127 and 66.9cm2V−1s−1 respectively. Our results are comparable to reduced graphene-oxide, indicating the advantage of our approach requires no further reduction to develop graphene-based transparent and conductive electrodes for dye-sensitized solar cells and ultra-capacitor applications.

Oxidation kinetics of plasmonic Ag particles in SiO2 nanofilms: Interlinking particle size to atmosphere–film–substrate system properties

A quantitative real-time assessment of the oxidation kinetics of Ag nanoparticles (NPs) embedded in nano-thin SiO2 films deposited on soda-lime glass has been carried out by a process-selective refinement of in situ optical microspectroscopy under ambient conditions. The temperature dependence of Ag NPs oxidation in the nanocomposite films was studied during thermal processing in air in the 673–773K temperature range. An Arrhenius-type analysis of the exponential decay of the peak intensity of the surface plasmon resonance of the NPs allowed for estimating the activation energy of the process at 4.54 (±0.53)×104Jmol−1. Transmission electron microscopy and secondary ion mass spectrometry are further employed in an effort to discuss the real-time optical spectroscopy information in a broader context regarding the possible physico-chemical multistep interactions in the air–nanofilm–substrate system as a whole.

Noninvasive Photodetachment of Stem Cells on Tunable Conductive Polymer Nano Thin Films: Selective Harvesting and Preserved Differentiation Capacity

Viable mesenchymal stem cells (MSCs) were efficiently and selectively harvested by near-infrared (NIR) light using the photothermal effect of a conductive polymer nano thin film. The poly(3,4-ethylenedioxy thiophene) (PEDOT)-coated cell culture surfaces were prepared via a simple and fast solution-casting polymerization (SCP) technique. The absorption of PEDOT thin films in the NIR region was effectively triggered cell harvesting upon exposure to an NIR source. By controlling the NIR absorption of the PEDOT film through electrochemical doping or growing PEDOT with different thin film thickness from 70 to 300 nm, the proliferation and harvesting of MSCs on the PEDOT surface were controlled quantitatively. This light-induced cell detachment method based on PEDOT films provides the temporal and spatial control of cell harvesting, as well as cell patterning. The harvested stem cells were found to be alive and well proliferated despite the use of temperature increase by NIR. More importantly, the harvested MSCs by this method preserved their intrinsic characteristics as well as multilineage differentiation capacities. This PEDOT surfaces could be used for repetitive culture and detachment of MSCs or for efficient selection or depletion of a specific subset from heterogeneous population during culture of various tissue-derived cells because there were no photodegradation and photobreakage in the PEDOT films by NIR exposure.

Nanoceramics: Issues and Opportunities

The goal of this study is to review developments in nanoceramics as discussed during presentations on the subject during the International Ceramic Congress (ICC4) held in Chicago on July 2012. As nanotechnology is such a broad subject affecting many industrial sectors, some presentations in other sessions were included as well. The study has been organized according to the dimensions of the nanoscale material starting with nanoscale entities or particulates followed by nanothin films and finally bulk nanoceramics where the nanoscale character lies in the structure. Developments on hybrid nanocomposites containing at least one ceramic compound were often included in the presentations and are discussed in a separate section. The promise of nanotechnology is also to discover materials with totally new properties or combinations of properties. One such example presented in depth at the conference is presented. The study concludes with a section on issues and opportunities. In general, it can be said that the very large investments that were made more than a decade ago into nanotechnology start to pay off dividends. Products are appearing on the market and can have a substantial impact there. Other commercial applications are on the horizon. Because of the wide scope of the technology, there are still plenty of opportunities for research and development. A particular issue that was mentioned by a number of speakers is that of upscaling, which can be understood literally as interfacing the nanostructure with the micro‐, meso‐, and macroworld. However, often one means the implementation on the factory floor of processes that have been developed within the laboratory.

Enhancement of poly(3,4-ethylenedioxy thiophene)/poly(styrene sulfonate) properties by poly(vinyl alcohol) and doping agent as conductive nano-thin film for electronic application

In this work, the integration of the useful concepts of polymer blending and doping agent to simultaneously improve various properties of poly(3,4-ethylene dioxy thiophene) poly(styrene sulfonate) (PEDOT:PSS) nano-thin films was shown. According to the polymer-blending concept, insulating poly(vinyl alcohol) (PVA) has a good deal of potential to be utilized as a filler to improve the critical properties of the PEDOT:PSS matrix, especially conductivity, wettability, and thermal and mechanical properties. At the appropriate amount of PVA, 0.08 wt%, it acts as a binder to improve the connection network between PEDOT:PSS chains, leading to a maximum conductivity of 1.18 S/cm, and also providing a good contact angle of 8.8°. The transmission of the films decreased with increasing PVA content; however, all specimens still showed excellent transmittance values of more than 80 %. The thermal stability and the resistance to abrasion of the nano-thin conductive films were improved by strong covalent bonds between PVA and PSS, which were verified by TGA and a scratching test, respectively. In addition, the relationship of PEDOT:PSS properties versus various amounts of insulating PVA for practical usage for specific electronic fields were shown. Use of the doping agent quinoxaline was aimed to particularly enhance the conductivity of PEDOT:PSS. The highest conductivity (2.75 S/cm) was achieved when 0.5 wt% quinoxaline was added into 0.08 wt% PVA/PEDOT:PSS while the other properties were not significantly altered.

Modeling and estimation of the parameters of the morphology of the surfaces of thin films of nano- and micro-electromechanical systems

Thin-film nano- and micro-electromechanical systems of pressure transducers, experimental and theoretical research methods, and the results of estimation of the parameters of the morphology of the surfaces of films are considered. A model and algorithm for the description of the growth of thin films that takes diffusion into account are developed.

Anomalous thermal conductivity by surface phonon-polaritons of polar nano thin films due to their asymmetric surrounding media

The surface phonon-polaritons contribution to the thermal conductivity of a nano thin film of silicon dioxide is investigated based on the Maxwell equations and the Boltzmann transport equation. It is shown that: (1) a small difference between the permittivities of the substrate and superstrate of the film can generate giant propagation lengths and therefore remarkably enhances its thermal conductivity with respect to values obtained for a freestanding one. (2) The propagation of surface phonon-polaritons is present in a broad band of frequencies and exhibits its largest propagation lengths at the frequency where the absorption of energy is minimal. (3) The increase of the thermal conductivity of the film as its thickness decreases is higher when it is deposited on potassium bromide instead of being suspended in air. The difference in the thermal conductivity for these two systems increases with increasing temperature and reducing the film thickness. A thermal conductivity as high as 2.5 W/m K is obtained for a 30 nm-thick thin film at room temperature, which is about 1.8 times larger than its bulk phonon value. The obtained results show that the propagation of surface phonon-polaritons has the potential not only to offset the reduction of the phonon thermal conductivity of a nano thin film, when its sizes are scaled down, but also to enhance it, by choosing properly the permittivity of its substrate.

Investigation of the hydrogen response characteristics for sol–gel-derived Pd-doped, Fe-doped and PEG-added SnO2 nano-thin films

This report describes the preparation of undoped, polyethylene glycol (PEG-400)-added, Fe-doped, Pd-doped and Fe-, Pd-doped, PEG-400-added SnO2 thin films using sol–gel technology. The gas-sensing properties of the five abovementioned structures were investigated over a range of 50–2000ppm H2. The linear response magnitude (S) response profile of Fe-, Pd-doped, PEG-400-added SnO2 thin film toward H2 concentration (C) was observed, and a concise formula without any transformation was expressed as S=1.724+0.046C (correlation coefficient (R)=0.99803, probability (P)<0.0001). The selectivity of Fe-, Pd-doped, PEG-400-added SnO2 thin film toward H2 in CO and CH4 defined as S(H2)/S(CO) and S(H2)/S(CH4) was 17.3 and 40.4, respectively, which was better than those of undoped SnO2 (2.6 and 5.3, respectively) at 225°C. A volcano-shaped correlation was observed in Fe-, Pd-doped, PEG-400-added SnO2 thin film approaching 2000ppm within a range of 75–275°C, and the film's response magnitude measured up to 55.75, even at a low temperature of 75°C. The consistency and reproducibility of undoped SnO2 thin films were investigated and found to be acceptable when considering the mass sensor production. Two important phenomena related to gas response time profile and a “fluctuation” that appeared at the bottom of every gas response profile were observed and qualitatively analyzed for the first time in this study.

N-doped TiO2nanothin films: photocatalytic and hydrophilicity properties

Nitrogen-doped TiO 2 nanothin films were synthesized by spray pyrolysis method using TiCl 4 as a precursor. Five samples including 0.0, 0.1, 0.2, 0.3 and 0.4 molar urea (as a nitrogen source) were fabricated. XRD spectra of the samples confirm that increasing the nitrogen doping initiates anatase to rutile-phase transformation and narrows band gap from 3.60 to 3.46 eV. This means that doping nitrogen increases the rate of the anatase to rutile-phase transformation. UV-vis spectrophotometer of the thin films showed 85–90% transmission in the visible region. AFM images indicate the increase of roughness and the grain size of the samples by increasing nitrogen doping. Optical band gaps were calculated by Tauc plot with values larger than those reported for bulk samples. The larger band gap might be due to the strain from lattice distortion. High hydrophilicity and photocatalytic properties were observed in thin films during UV illumination that persists for 210 min. It was found that the sample with the largest amount of N doping shows the best hydrophilicity activity and photocatalytic property.

GISAXS study on the annealing behavior of sputtered HfO2 thin films

AbstractGrazing Incidence Small-Angle X-ray Scattering (GISAXS) is a versatile technique for the analysis of nano and micro thin films surfaces. The scattering data depend strongly on the form and distribution of the scattering objects. In the present work GISAXS is used to study hafnium dioxide (HfO2) thin films deposited by magnetron sputtering using different deposition processes and post-deposition annealing conditions. Two distinct types of 15 nm thick samples were produced using different sputtering targets and different gas mixtures. The GISAXS results show that the ellipsoids that compose the thin films present a reduction in their size for both samples sets. For the sputtered Hf metal target samples, the ellipsoid diameter value shifted from 9 nm (as-deposited) to 6 nm following a 800 °C thermal treatment. For the sputtered HfO2 target samples the diameter value shifts from 19 nm (as-deposited) to 3 nm after a 800 °C anneal in oxygen. The size distribution, for both sets of samples, follows a Gaussian distribution function.

Preparation and Characterization of Cu-Zn Nano-Structural Ferrite Thin Films Produced by Pulsed Laser Deposition (PLD)

Cu-Zn ferrite nano thin films were deposited from a target of Cu-Zn ferrite onto a sapphire substrate using XeCl excimer laser operating 308 nm with an energy of 225 mJ and a frequency of 30 Hz. Films were deposited from the target onto sapphire (001) substrates heated to 650℃ in an oxygen atmosphere of 100 mTorr. The laser beam was incident On the target face at an angle of 45°. Studies on crystal structure were done by X-ray diffactometry (XRD). The surface texture, cross-section morphology and grain size was observed by JEOL-JSM-6400 scanning electron microscopy, atomic force microscopy (AFM) and magnetic force microscopy (MFM) [Model DI 3000, Digital instruments].