Spin-coated epoxy resin embedding technique enables facile SEM/FIB thickness determination of porous metal oxide ultra-thin films.

PubMed

Peña, B; Owen, G Rh; Dettelbach, K E; Berlinguette, C P

2018-01-25

A facile nonsubjective method was designed to measure porous nonconductive iron oxide film thickness using a combination of a focused ion beam (FIB) and scanning electron microscopy. Iron oxide films are inherently nonconductive and porous, therefore the objective of this investigation was to optimize a methodology that would increase the conductivity of the film to facilitate high resolution imaging with a scanning electron microscopy and to preserve the porous nature of the film that could potentially be damaged by the energy of the FIB. Sputter coating the sample with a thin layer of iridium before creating the cross section with the FIB decreased sample charging and drifting, but differentiating the iron layer from the iridium coating with backscattered electron imaging was not definitive, making accurate assumptions of the delineation between the two metals difficult. Moreover, the porous nature of the film was lost due to beam damage following the FIB process. A thin layer plastication technique was therefore used to embed the porous film in epoxy resin that would provide support for the film during the FIB process. However, the thickness of the resin created using conventional thin layer plastication processing varied across the sample, making the measuring process only possible in areas where the resin layer was at its thinnest. Such variation required navigating the area for ideal milling areas, which increased the subjectivity of the process. We present a method to create uniform thin resin layers, of controlled thickness, that are ideal for quantifying the thickness of porous nonconductive films with FIB/scanning electron microscopy. © 2018 The Authors Journal of Microscopy © 2018 Royal Microscopical Society.

Investigation of phase transition properties of ZrO2 thin films

NASA Astrophysics Data System (ADS)

Kumar, Davinder; Singh, Avtar; Kaur, Manpreet; Rana, Vikrant Singh; Kaur, Raminder

2018-05-01

This paper presents the synthesis of transparent thin films of zirconium oxide (ZrO2) deposited on glass substrates by sol-gel dip coating technique. Synthesized films were characterized for different annealing time and withdrawal speed. Change in crystallographic properties of thin films was investigated by using X-ray diffraction. Surface morphology of transparent thin films was estimated by using scanning electron microscope.

Studying Dynamic Processes of Nano-sized Objects in Liquid using Scanning Transmission Electron Microscopy.

PubMed

Hermannsdörfer, Justus; de Jonge, Niels

2017-02-05

Samples fully embedded in liquid can be studied at a nanoscale spatial resolution with Scanning Transmission Electron Microscopy (STEM) using a microfluidic chamber assembled in the specimen holder for Transmission Electron Microscopy (TEM) and STEM. The microfluidic system consists of two silicon microchips supporting thin Silicon Nitride (SiN) membrane windows. This article describes the basic steps of sample loading and data acquisition. Most important of all is to ensure that the liquid compartment is correctly assembled, thus providing a thin liquid layer and a vacuum seal. This protocol also includes a number of tests necessary to perform during sample loading in order to ensure correct assembly. Once the sample is loaded in the electron microscope, the liquid thickness needs to be measured. Incorrect assembly may result in a too-thick liquid, while a too-thin liquid may indicate the absence of liquid, such as when a bubble is formed. Finally, the protocol explains how images are taken and how dynamic processes can be studied. A sample containing AuNPs is imaged both in pure water and in saline.

Studying Dynamic Processes of Nano-sized Objects in Liquid using Scanning Transmission Electron Microscopy

PubMed Central

Hermannsdörfer, Justus; de Jonge, Niels

2017-01-01

Samples fully embedded in liquid can be studied at a nanoscale spatial resolution with Scanning Transmission Electron Microscopy (STEM) using a microfluidic chamber assembled in the specimen holder for Transmission Electron Microscopy (TEM) and STEM. The microfluidic system consists of two silicon microchips supporting thin Silicon Nitride (SiN) membrane windows. This article describes the basic steps of sample loading and data acquisition. Most important of all is to ensure that the liquid compartment is correctly assembled, thus providing a thin liquid layer and a vacuum seal. This protocol also includes a number of tests necessary to perform during sample loading in order to ensure correct assembly. Once the sample is loaded in the electron microscope, the liquid thickness needs to be measured. Incorrect assembly may result in a too-thick liquid, while a too-thin liquid may indicate the absence of liquid, such as when a bubble is formed. Finally, the protocol explains how images are taken and how dynamic processes can be studied. A sample containing AuNPs is imaged both in pure water and in saline. PMID:28190028

Plasmon-enhanced electron scattering in nanostructured thin metal films revealed by low-voltage scanning electron microscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mikhailovskii, V., E-mail: v.mikhailovskii@spbu.ru; IRC for Nanotechnology, Research Park, St.-Petersburg State University; Petrov, Yu.

2016-06-17

The drastic enhancement of backscattered electrons (BSE) yield from nanostructured thin metal film which exceeded well the one from massive metal was observed at accelerating voltages below 400 V. The dependences of BSE signal from nanostructured gold film on accelerating voltage and on retarding grid potential applied to BSE detector were investigated. It was shown that enhanced BSE signal was formed by inelastic scattered electrons coming from the gaps between nanoparticles. A tentative explanation of the mechanism of BSE signal enhancement was suggested.

New developments in electron microscopy for serial image acquisition of neuronal profiles.

PubMed

Kubota, Yoshiyuki

2015-02-01

Recent developments in electron microscopy largely automate the continuous acquisition of serial electron micrographs (EMGs), previously achieved by laborious manual serial ultrathin sectioning using an ultramicrotome and ultrastructural image capture process with transmission electron microscopy. The new systems cut thin sections and capture serial EMGs automatically, allowing for acquisition of large data sets in a reasonably short time. The new methods are focused ion beam/scanning electron microscopy, ultramicrotome/serial block-face scanning electron microscopy, automated tape-collection ultramicrotome/scanning electron microscopy and transmission electron microscope camera array. In this review, their positive and negative aspects are discussed. © The Author 2015. Published by Oxford University Press on behalf of The Japanese Society of Microscopy. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Atom Chips on Direct Bonded Copper Substrates (Postprint)

DTIC Science & Technology

2012-01-19

joining of a thin sheet of pure copper to a ceramic substrate14 and is commonly used in power electronics due to its high current handling and heat...Squires et al. Rev. Sci. Instrum. 82, 023101 (2011) FIG. 1. A scanning electron micrograph of the top view of test chip A. the photolithographically...the etching pro- cesses and masking methods were quantified using a scanning electron microscope. Two test chips (A and B) are presented below and are

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gill, Tobias G.; Fleurence, Antoine; Warner, Ben

We observe a new two-dimensional (2D) silicon crystal, using low energy electron diffraction (LEED) and scanning tunnelling microscopy (STM) and it's formed by depositing additional Si atoms onto spontaneously-formed epitaxial silicene on a ZrB 2 thin film. From scanning tunnelling spectroscopy (STS) studies, we find that this atomically-thin layered silicon has distinctly different electronic properties. Angle resolved photoelectron spectroscopy (ARPES) reveals that, in sharp contrast to epitaxial silicene, the layered silicon exhibits significantly enhanced density of states at the Fermi level resulting from newly formed metallic bands. Furthermore, the 2D growth of this material could allow for direct contacting tomore » the silicene surface and demonstrates the dramatic changes in electronic structure that can occur by the addition of even a single monolayer amount of material in 2D systems.« less

Structural, Morphological, and Electron Transport Studies of Annealing Dependent In2O3 Dye-Sensitized Solar Cell

PubMed Central

Mahalingam, S.; Abdullah, H.; Shaari, S.; Muchtar, A.; Asshari, I.

2015-01-01

Indium oxide (In2O3) thin films annealed at various annealing temperatures were prepared by using spin-coating method for dye-sensitized solar cells (DSSCs). The objective of this research is to enhance the photovoltaic conversion efficiency in In2O3 thin films by finding the optimum annealing temperature and also to study the reason for high and low performance in the annealed In2O3 thin films. The structural and morphological characteristics of In2O3 thin films were studied via XRD patterns, atomic force microscopy (AFM), field-emission scanning electron microscopy (FESEM), EDX sampling, and transmission electron microscopy (TEM). The annealing treatment modified the nanostructures of the In2O3 thin films viewed through FESEM images. The In2O3-450°C-based DSSC exhibited better photovoltaic performance than the other annealed thin films of 1.54%. The electron properties were studied by electrochemical impedance spectroscopy (EIS) unit. The In2O3-450°C thin films provide larger diffusion rate, low recombination effect, and longer electron lifetime, thus enhancing the performance of DSSC. PMID:26146652

The uniformity study of non-oxide thin film at device level using electron energy loss spectroscopy

NASA Astrophysics Data System (ADS)

Li, Zhi-Peng; Zheng, Yuankai; Li, Shaoping; Wang, Haifeng

2018-05-01

Electron energy loss spectroscopy (EELS) has been widely used as a chemical analysis technique to characterize materials chemical properties, such as element valence states, atoms/ions bonding environment. This study provides a new method to characterize physical properties (i.e., film uniformity, grain orientations) of non-oxide thin films in the magnetic device by using EELS microanalysis on scanning transmission electron microscope. This method is based on analyzing white line ratio of spectra and related extended energy loss fine structures so as to correlate it with thin film uniformity. This new approach can provide an effective and sensitive method to monitor/characterize thin film quality (i.e., uniformity) at atomic level for thin film development, which is especially useful for examining ultra-thin films (i.e., several nanometers) or embedded films in devices for industry applications. More importantly, this technique enables development of quantitative characterization of thin film uniformity and it would be a remarkably useful technique for examining various types of devices for industrial applications.

Fabrication and characterization of silver- and copper-coated Nylon 6 forcespun nanofibers by thermal evaporation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mihut, Dorina M., E-mail: dorinamm@yahoo.com; Lozano, Karen; Foltz, Heinrich

2014-11-01

Silver and copper nanoparticles were deposited as thin films onto substrates consisting of Nylon 6 nanofibers manufactured using forcespinning{sup ®} equipment. Different rotational speeds were used to obtain continuous nanofibers of various diameters arranged as nonwoven mats. The Nylon 6 nanofibers were collected as successive layers on frames, and a high-vacuum thermal evaporation method was used to deposit the silver and copper thin films on the nanofibers. The structures were investigated using scanning electron microscopy–scanning transmission electron microscopy, atomic force microscopy, x-ray diffraction, and electrical resistance measurements. The results indicate that evaporated silver and copper nanoparticles were successfully deposited onmore » Nylon 6 nanofibers as thin films that adhered well to the polymer substrate while the native morphology of the nanofibers were preserved, and electrically conductive nanostructures were achieved.« less

Preparation of nickel oxide thin films at different annealing temperature by sol-gel spin coating method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Abdullah, M. A. R., E-mail: ameerridhwan89@gmail.com; Mamat, M. H., E-mail: hafiz-030@yahoo.com; Ismail, A. S., E-mail: kyrin-samaxi@yahoo.com

2016-07-06

Preparation of NiO thin films at different annealing temperature by sol-gel method was conducted to synthesize the quality of the surface thin films. The effects of annealing temperature on the surface topology were systematically investigated. Our studies confirmed that the surface roughness of the thin films was increased whenever annealing temperature was increase. NiO thin films morphology structure analysis was confirmed by field emission scanning electron microscope. Surface roughness of the thin films was investigated by atomic force microscopy.

STEMsalabim: A high-performance computing cluster friendly code for scanning transmission electron microscopy image simulations of thin specimens.

PubMed

Oelerich, Jan Oliver; Duschek, Lennart; Belz, Jürgen; Beyer, Andreas; Baranovskii, Sergei D; Volz, Kerstin

2017-06-01

We present a new multislice code for the computer simulation of scanning transmission electron microscope (STEM) images based on the frozen lattice approximation. Unlike existing software packages, the code is optimized to perform well on highly parallelized computing clusters, combining distributed and shared memory architectures. This enables efficient calculation of large lateral scanning areas of the specimen within the frozen lattice approximation and fine-grained sweeps of parameter space. Copyright © 2017 Elsevier B.V. All rights reserved.

On the structural origins of ferroelectricity in HfO{sub 2} thin films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sang, Xiahan; Grimley, Everett D.; LeBeau, James M.

2015-04-20

Here, we present a structural study on the origin of ferroelectricity in Gd doped HfO{sub 2} thin films. We apply aberration corrected high-angle annular dark-field scanning transmission electron microscopy to directly determine the underlying lattice type using projected atom positions and measured lattice parameters. Furthermore, we apply nanoscale electron diffraction methods to visualize the crystal symmetry elements. Combined, the experimental results provide unambiguous evidence for the existence of a non-centrosymmetric orthorhombic phase that can support spontaneous polarization, resolving the origin of ferroelectricity in HfO{sub 2} thin films.

The effect of TiO2 thin film thickness on self-cleaning glass properties

NASA Astrophysics Data System (ADS)

Mufti, Nandang; Laila, Ifa K. R.; Hartatiek; Fuad, Abdulloh

2017-05-01

TiO2 is one of semiconductor materials which are widely used as photocatalyst in the form of a thin film. The TiO2 thin film is prepared by using the spin coating sol-gel method. The researcher prepared TiO2 thin film with 3 coating variations and X-Ray Diffraction characterization, UV-Vis Spectrophotometer, Electron Microscopy Scanning, and examined its hydrophilic and anti-fogging properties. The result of X-Ray Diffraction showed that the phase formed is the anatase on 101crystal field. The Electron Microscopy Scanning images showed that TiO2 thin films had a homogeneous surface with the particle sizes as big as 235 nm, 179 nm, and 137 nm. The thickness of each thin film was 2.06μm, 3.33μm, and 5.20μm. The characterization of UV-Vis Spectrophotometer showed that the greatest absorption to the wavelength of visible light was in the thin film’s thickness of 3 coatings with the band-gap determined by using 3.30 eV, 3.33 eV, and 3.33 eV Plot Tuoc. These results indicated that the rate of absorption would be increased by increasing the thickness of film. The increasing thickness of the thin film makes the film hydrophilic able to be used as an anti-fogging substance.

Structural and morphological study of chemically synthesized CdSe thin films

NASA Astrophysics Data System (ADS)

Agrawal, P.; Singh, Randhir; Sharma, Jeewan; Sachdeva, M.; Singh, Anupinder; Bhargava, A.

2018-05-01

Nanocrystalline CdSe thin films were prepared by Chemical Bath Deposition (CBD) method using potassium nitrilo-triacetic acid cadmium complex and sodium selenosulphite. The as deposited films were red in color, uniform and well adherent to the glass substrate. These films were strongly dependent on the deposition parameters such as bath composition, deposition temperature and time. Films were annealed at 350 °C for four hours. The morphological, structural and optical properties were studied using X-ray diffraction (XRD), UV-VIS spectrophotometer measurements, scanning electron microscopy and atomic force microscopy. The XRD analysis confirmed that films are predominantly in hexagonal phase. Scanning electron micrograph shows that the grains are uniformly spread all over the film and each grain contains many nanocrystals with spherical shapes.

Tunneling rates in electron transport through double-barrier molecular junctions in a scanning tunneling microscope

PubMed Central

Nazin, G. V.; Wu, S. W.; Ho, W.

2005-01-01

The scanning tunneling microscope enables atomic-scale measurements of electron transport through individual molecules. Copper phthalocyanine and magnesium porphine molecules adsorbed on a thin oxide film grown on the NiAl(110) surface were probed. The single-molecule junctions contained two tunneling barriers, vacuum gap, and oxide film. Differential conductance spectroscopy shows that electron transport occurs via vibronic states of the molecules. The intensity of spectral peaks corresponding to the individual vibronic states depends on the relative electron tunneling rates through the two barriers of the junction, as found by varying the vacuum gap tunneling rate by changing the height of the scanning tunneling microscope tip above the molecule. A simple, sequential tunneling model explains the observed trends. PMID:15956189

Tunneling rates in electron transport through double-barrier molecular junctions in a scanning tunneling microscope.

PubMed

Nazin, G V; Wu, S W; Ho, W

2005-06-21

The scanning tunneling microscope enables atomic-scale measurements of electron transport through individual molecules. Copper phthalocyanine and magnesium porphine molecules adsorbed on a thin oxide film grown on the NiAl(110) surface were probed. The single-molecule junctions contained two tunneling barriers, vacuum gap, and oxide film. Differential conductance spectroscopy shows that electron transport occurs via vibronic states of the molecules. The intensity of spectral peaks corresponding to the individual vibronic states depends on the relative electron tunneling rates through the two barriers of the junction, as found by varying the vacuum gap tunneling rate by changing the height of the scanning tunneling microscope tip above the molecule. A simple, sequential tunneling model explains the observed trends.

Electronic and optical properties of La-doped S r3I r2O7 epitaxial thin films

NASA Astrophysics Data System (ADS)

Souri, M.; Terzic, J.; Johnson, J. M.; Connell, J. G.; Gruenewald, J. H.; Thompson, J.; Brill, J. W.; Hwang, J.; Cao, G.; Seo, A.

2018-02-01

We have investigated structural, transport, and optical properties of tensile strained (Sr1-xL ax ) 3I r2O7 (x =0 , 0.025, 0.05) epitaxial thin films. While high-Tc superconductivity is predicted theoretically in the system, we have observed that all of the samples remain insulating with finite optical gap energies and Mott variable-range hopping characteristics in transport. Cross-sectional scanning transmission electron microscopy indicates that structural defects such as stacking faults appear in this system. The insulating behavior of the La-doped S r3I r2O7 thin films is presumably due to disorder-induced localization and ineffective electron doping of La, which brings to light the intriguing difference between epitaxial thin films and bulk single crystals of the iridates.

Preparation and characterization of nanostructured Pt/TiO2 thin films treated using electron beam.

PubMed

Shin, Joong-Hyeok; Woo, Hee-Gweon; Kim, Bo-Hye; Lee, Byung Cheol; Jun, Jin

2010-05-01

Pt nanoparticle-doped titanium dioxide (Pt/TiO2) thin films were prepared on a silicon wafer substrate by sol-gel spin coating process. The prepared thin films were treated with electron beam (EB at 1.1 MeV, 100, 200, 300 kGy) at air atmosphere. The effect of EB-irradiation on the composition of the treated thin films, optical properties and morphology of thin films were investigated by various analytical techniques such as X-ray photoelectron spectroscopy (XPS), spectroscopic ellipsometry (SE), X-ray diffraction (XRD), field emission-scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM). The crystal structure of the TiO2 layer was found to be an anatase phase and the size of TiO2 particles was determined to be about 13 nm. Pt nanoparticles with diameter of 5 nm were observed on surface of the films. A new layer (presumed to be Pt-Ti complex and/or PtO2 compound) was created in the Pt/TiO2 thin film treated with EB (300 kGy). The transmittance of thin film decreased with EB treatment whereas the refractive index increased.

Atomic-scale visualization of oxide thin-film surfaces.

PubMed

Iwaya, Katsuya; Ohsawa, Takeo; Shimizu, Ryota; Okada, Yoshinori; Hitosugi, Taro

2018-01-01

The interfaces of complex oxide heterostructures exhibit intriguing phenomena not observed in their constituent materials. The oxide thin-film growth of such heterostructures has been successfully controlled with unit-cell precision; however, atomic-scale understandings of oxide thin-film surfaces and interfaces have remained insufficient. We examined, with atomic precision, the surface and electronic structures of oxide thin films and their growth processes using low-temperature scanning tunneling microscopy. Our results reveal that oxide thin-film surface structures are complicated in contrast to the general perception and that atomically ordered surfaces can be achieved with careful attention to the surface preparation. Such atomically ordered oxide thin-film surfaces offer great opportunities not only for investigating the microscopic origins of interfacial phenomena but also for exploring new surface phenomena and for studying the electronic states of complex oxides that are inaccessible using bulk samples.

Far-field optical imaging with subdiffraction resolution enabled by nonlinear saturation absorption

NASA Astrophysics Data System (ADS)

Ding, Chenliang; Wei, Jingsong

2016-01-01

The resolution of far-field optical imaging is required to improve beyond the Abbe limit to the subdiffraction or even the nanoscale. In this work, inspired by scanning electronic microscopy (SEM) imaging, in which carbon (or Au) thin films are usually required to be coated on the sample surface before imaging to remove the charging effect while imaging by electrons. We propose a saturation-absorption-induced far-field super-resolution optical imaging method (SAI-SRIM). In the SAI-SRIM, the carbon (or Au) layers in SEM imaging are replaced by nonlinear-saturation-absorption (NSA) thin films, which are directly coated onto the sample surfaces using advanced thin film deposition techniques. The surface fluctuant morphologies are replicated to the NSA thin films, accordingly. The coated sample surfaces are then imaged using conventional laser scanning microscopy. Consequently, the imaging resolution is greatly improved, and subdiffraction-resolved optical images are obtained theoretically and experimentally. The SAI-SRIM provides an effective and easy way to achieve far-field super-resolution optical imaging for sample surfaces with geometric fluctuant morphology characteristics.

Two-dimensional X-ray diffraction and transmission electron microscopy study on the effect of magnetron sputtering atmosphere on GaN/SiC interface and gallium nitride thin film crystal structure

NASA Astrophysics Data System (ADS)

Shen, Huaxiang; Zhu, Guo-Zhen; Botton, Gianluigi A.; Kitai, Adrian

2015-03-01

The growth mechanisms of high quality GaN thin films on 6H-SiC by sputtering were investigated by X-ray diffraction (XRD) and scanning transmission electron microscopy (STEM). The XRD θ-2θ scans show that high quality ( 0002 ) oriented GaN was deposited on 6H-SiC by reactive magnetron sputtering. Pole figures obtained by 2D-XRD clarify that GaN thin films are dominated by ( 0002 ) oriented wurtzite GaN and { 111 } oriented zinc-blende GaN. A thin amorphous silicon oxide layer on SiC surfaces observed by STEM plays a critical role in terms of the orientation information transfer from the substrate to the GaN epilayer. The addition of H2 into Ar and/or N2 during sputtering can reduce the thickness of the amorphous layer. Moreover, adding 5% H2 into Ar can facilitate a phase transformation from amorphous to crystalline in the silicon oxide layer and eliminate the unwanted { 3 3 ¯ 02 } orientation in the GaN thin film. Fiber texture GaN thin films can be grown by adding 10% H2 into N2 due to the complex reaction between H2 and N2.

Energy dispersive X-ray analysis on an absolute scale in scanning transmission electron microscopy.

PubMed

Chen, Z; D'Alfonso, A J; Weyland, M; Taplin, D J; Allen, L J; Findlay, S D

2015-10-01

We demonstrate absolute scale agreement between the number of X-ray counts in energy dispersive X-ray spectroscopy using an atomic-scale coherent electron probe and first-principles simulations. Scan-averaged spectra were collected across a range of thicknesses with precisely determined and controlled microscope parameters. Ionization cross-sections were calculated using the quantum excitation of phonons model, incorporating dynamical (multiple) electron scattering, which is seen to be important even for very thin specimens. Copyright © 2015 Elsevier B.V. All rights reserved.

Effect of Doping Materials on the Low-Level NO Gas Sensing Properties of ZnO Thin Films

NASA Astrophysics Data System (ADS)

Çorlu, Tugba; Karaduman, Irmak; Yildirim, Memet Ali; Ateş, Aytunç; Acar, Selim

2017-07-01

In this study, undoped, Cu-doped, and Ni-doped ZnO thin films have been successfully prepared by successive ionic layer adsorption and reaction method. The structural, compositional, and morphological properties of the thin films are characterized by x-ray diffractometer, energy dispersive x-ray analysis (EDX), and scanning electron microscopy, respectively. Doping effects on the NO gas sensing properties of these thin films were investigated depending on gas concentration and operating temperature. Cu-doped ZnO thin film exhibited a higher gas response than undoped and Ni-doped ZnO thin film at the operating temperature range. The sensor with Cu-doped ZnO thin film gave faster responses and recovery speeds than other sensors, so that is significant for the convenient application of gas sensor. The response and recovery speeds could be associated with the effective electron transfer between the Cu-doped ZnO and the NO molecules.

Scanning electron microscope cathodoluminescence imaging of subgrain boundaries, twins and planar deformation features in quartz

NASA Astrophysics Data System (ADS)

Hamers, M. F.; Pennock, G. M.; Drury, M. R.

2017-04-01

The study of deformation features has been of great importance to determine deformation mechanisms in quartz. Relevant microstructures in both growth and deformation processes include dislocations, subgrains, subgrain boundaries, Brazil and Dauphiné twins and planar deformation features (PDFs). Dislocations and twin boundaries are most commonly imaged using a transmission electron microscope (TEM), because these cannot directly be observed using light microscopy, in contrast to PDFs. Here, we show that red-filtered cathodoluminescence imaging in a scanning electron microscope (SEM) is a useful method to visualise subgrain boundaries, Brazil and Dauphiné twin boundaries. Because standard petrographic thin sections can be studied in the SEM, the observed structures can be directly and easily correlated to light microscopy studies. In contrast to TEM preparation methods, SEM techniques are non-destructive to the area of interest on a petrographic thin section.

Electron beam induced radiation damage in the catalyst layer of a proton exchange membrane fuel cell.

PubMed

He, Qianping; Chen, Jihua; Keffer, David J; Joy, David C

2014-01-01

Electron microscopy is an essential tool for the evaluation of microstructure and properties of the catalyst layer (CL) of proton exchange membrane fuel cells (PEMFCs). However, electron microscopy has one unavoidable drawback, which is radiation damage. Samples suffer temporary or permanent change of the surface or bulk structure under radiation damage, which can cause ambiguity in the characterization of the sample. To better understand the mechanism of radiation damage of CL samples and to be able to separate the morphological features intrinsic to the material from the consequences of electron radiation damage, a series of experiments based on high-angle annular dark-field-scanning transmission scanning microscope (HAADF-STEM), energy filtering transmission scanning microscope (EFTEM), and electron energy loss spectrum (EELS) are conducted. It is observed that for thin samples (0.3-1 times λ), increasing the incident beam energy can mitigate the radiation damage. Platinum nanoparticles in the CL sample facilitate the radiation damage. The radiation damage of the catalyst sample starts from the interface of Pt/C or defective thin edge and primarily occurs in the form of mass loss accompanied by atomic displacement and edge curl. These results provide important insights on the mechanism of CL radiation damage. Possible strategies of mitigating the radiation damage are provided. © 2013 Wiley Periodicals, Inc.

Structural and morphological study of ZrO2 thin films

NASA Astrophysics Data System (ADS)

Kumar, Davinder; Singh, Avtar; Kaur, Manpreet; Rana, Vikrant Singh; Kaur, Raminder

2018-05-01

In this paper we discuss the fabrication of transparent thin films of Zirconium Oxide (ZrO2) deposited on glass substrates by sol-gel dip coating technique. Further these fabricated films were characterized for different annealing temperatures and withdrawal speed. X-ray diffraction is used to study the structural properties of deposited thin films and it reveals the change in crystallographic properties with the change in annealing temperature. Thickness of thin films is estimated by using scanning electron microscope.

Atmospheric scanning electron microscope observes cells and tissues in open medium through silicon nitride film.

PubMed

Nishiyama, Hidetoshi; Suga, Mitsuo; Ogura, Toshihiko; Maruyama, Yuusuke; Koizumi, Mitsuru; Mio, Kazuhiro; Kitamura, Shinichi; Sato, Chikara

2010-03-01

Direct observation of subcellular structures and their characterization is essential for understanding their physiological functions. To observe them in open environment, we have developed an inverted scanning electron microscope with a detachable, open-culture dish, capable of 8 nm resolution, and combined with a fluorescence microscope quasi-simultaneously observing the same area from the top. For scanning electron microscopy from the bottom, a silicon nitride film window in the base of the dish maintains a vacuum between electron gun and open sample dish while allowing electrons to pass through. Electrons are backscattered from the sample and captured by a detector under the dish. Cells cultured on the open dish can be externally manipulated under optical microscopy, fixed, and observed using scanning electron microscopy. Once fine structures have been revealed by scanning electron microscopy, their component proteins may be identified by comparison with separately prepared fluorescence-labeled optical microscopic images of the candidate proteins, with their heavy-metal-labeled or stained ASEM images. Furthermore, cell nuclei in a tissue block stained with platinum-blue were successfully observed without thin-sectioning, which suggests the applicability of this inverted scanning electron microscope to cancer diagnosis. This microscope visualizes mesoscopic-scale structures, and is also applicable to non-bioscience fields including polymer chemistry. (c) 2010 Elsevier Inc. All rights reserved.

Fabrication and etching processes of silicon-based PZT thin films

NASA Astrophysics Data System (ADS)

Zhao, Hongjin; Liu, Yanxiang; Liu, Jianshe; Ren, Tian-Ling; Liu, Li-Tian; Li, Zhijian

2001-09-01

Lead-zirconate-titanate (PZT) thin films on silicon were prepared by a sol-gel method. Phase characterization and crystal orientation of the films were investigated by x-ray diffraction analysis (XRD). It was shown that the PZT thin films had a perfect perovskite structure after annealed at a low temperature of 600 degrees C. PZT thin films were chemically etched using HCl/HF solution through typical semiconductor lithographic process, and the etching condition was optimized. The scanning electron microscopy results indicated that the PZT thin film etching problem was well solved for the applications of PZT thin film devices.

Imaging of Norway spruce early somatic embryos with the ESEM, Cryo-SEM and laser scanning microscope.

PubMed

Neděla, Vilém; Hřib, Jiří; Havel, Ladislav; Hudec, Jiří; Runštuk, Jiří

2016-05-01

This article describes the surface structure of Norway spruce early somatic embryos (ESEs) as a typical culture with asynchronous development. The microstructure of extracellular matrix covering ESEs were observed using the environmental scanning electron microscope as a primary tool and using the scanning electron microscope with cryo attachment and laser electron microscope as a complementary tool allowing our results to be proven independently. The fresh samples were observed in conditions of the air environment of the environmental scanning electron microscope (ESEM) with the pressure from 550Pa to 690Pa and the low temperature of the sample from -18°C to -22°C. The samples were studied using two different types of detector to allow studying either the thin surface structure or material composition. The scanning electron microscope with cryo attachment was used for imaging frozen extracellular matrix microstructure with higher resolution. The combination of both electron microscopy methods was suitable for observation of "native" plant samples, allowing correct evaluation of our results, free of error and artifacts. Copyright © 2016 Elsevier Ltd. All rights reserved.

Carbon contamination in scanning transmission electron microscopy and its impact on phase-plate applications.

PubMed

Hettler, Simon; Dries, Manuel; Hermann, Peter; Obermair, Martin; Gerthsen, Dagmar; Malac, Marek

2017-05-01

We analyze electron-beam induced carbon contamination in a transmission electron microscope. The study is performed on thin films potentially suitable as phase plates for phase-contrast transmission electron microscopy. Electron energy-loss spectroscopy and phase-plate imaging is utilized to analyze the contamination. The deposited contamination layer is identified as a graphitic carbon layer which is not prone to electrostatic charging whereas a non-conductive underlying substrate charges. Several methods that inhibit contamination are evaluated and the impact of carbon contamination on phase-plate imaging is discussed. The findings are in general interesting for scanning transmission electron microscopy applications. Crown Copyright © 2017. Published by Elsevier Ltd. All rights reserved.

Electrodeposition of thin yttria-stabilized zirconia layers using glow-discharge plasma

NASA Astrophysics Data System (ADS)

Ogumi, Zempachi; Uchimoto, Yoshiharu; Tsuji, Yoichiro; Takehara, Zen-ichiro

1992-08-01

A novel process for preparation of thin yttria-stabilized zirconia (YSZ) layers was developed. This process differs from other vapor-phase deposition methods in that a dc bias circuit, separate from the plasma-generation circuit, is used for the electrodeposition process. The YSZ layer was electrodeposited from ZrCl4 and YCl3 on a nonporous calcia-stabilized zirconia substrate. Scanning electron microscopy, electron probe microanalysis, electron spectroscopy for chemical analysis, and x-ray-diffraction measurements confirmed the electrodeposition of a smooth, pinhole-free yttria-stabilized zirconia film of about 3 μm thickness.

Structural, electronic transport and optical properties of Cr doped PbS thin film by chemical bath deposition

NASA Astrophysics Data System (ADS)

Preetha, K. C.

2017-06-01

Incorporation of Chromium ions into Lead Sulphide thin films have been achieved by CBD technique. Effects of doping were investigated as a function of Pb/Cr ratio from o to 2 at %. X-ray diffraction patterns showed that films were polycrystalline in nature with increase in crystallite size up to an optimum doping concentration. Scanning electron microscopic study revealed excellent morphology with doping concentration. The low transmittance in the UV-VIS region offered the suitability of the samples as solar control coatings. The thin films were found to be P type and electrical conductivity enhanced on doping.

Development of Thin Films as Potential Structural Cathodes to Enable Multifunctional Energy-Storage Structural Composite Batteries for the U.S. Army’s Future Force

DTIC Science & Technology

2011-09-01

glancing angle X - ray diffraction (GAXRD), atomic force microscopy (AFM), scanning electron microscopy (SEM), and electrochemical...Emission SEM FWHM full width at half maximum GAXRD glancing angle X - ray diffraction H3COCH2CH2OH 2-methoxyethanol LiMn2O4 lithium manganese oxide...were characterized by scanning electron microscopy (SEM), X - ray diffraction (XRD), and atomic force microscopy (AFM). In addition,

One dimensional metallic edges in atomically thin WSe2 induced by air exposure

NASA Astrophysics Data System (ADS)

Addou, Rafik; Smyth, Christopher M.; Noh, Ji-Young; Lin, Yu-Chuan; Pan, Yi; Eichfeld, Sarah M.; Fölsch, Stefan; Robinson, Joshua A.; Cho, Kyeongjae; Feenstra, Randall M.; Wallace, Robert M.

2018-04-01

Transition metal dichalcogenides are a unique class of layered two-dimensional (2D) crystals with extensive promising applications. Tuning the electronic properties of low-dimensional materials is vital for engineering new functionalities. Surface oxidation is of particular interest because it is a relatively simple method of functionalization. By means of scanning probe microscopy and x-ray photoelectron spectroscopy, we report the observation of metallic edges in atomically thin WSe2 monolayers grown by chemical vapor deposition on epitaxial graphene. Scanning tunneling microscopy shows structural details of WSe2 edges and scanning tunneling spectroscopy reveals the metallic nature of the oxidized edges. Photoemission demonstrates that the formation of metallic sub-stoichiometric tungsten oxide (WO2.7) is responsible for the high conductivity measured along the edges. Ab initio calculations validate the susceptibility of WSe2 nanoribbon edges to oxidation. The zigzag terminated edge exhibits metallic behavior prior the air-exposure and remains metallic after oxidation. Comprehending and exploiting this property opens a new opportunity for application in advanced electronic devices.

Glancing angle deposition of sculptured thin metal films at room temperature

NASA Astrophysics Data System (ADS)

Liedtke, S.; Grüner, Ch; Lotnyk, A.; Rauschenbach, B.

2017-09-01

Metallic thin films consisting of separated nanostructures are fabricated by evaporative glancing angle deposition at room temperature. The columnar microstructure of the Ti and Cr columns is investigated by high resolution transmission electron microscopy and selective area electron diffraction. The morphology of the sculptured metallic films is studied by scanning electron microscopy. It is found that tilted Ti and Cr columns grow with a single crystalline morphology, while upright Cr columns are polycrystalline. Further, the influence of continuous substrate rotation on the shaping of Al, Ti, Cr and Mo nanostructures is studied with view to surface diffusion and the shadowing effect. It is observed that sculptured metallic thin films deposited without substrate rotation grow faster compared to those grown with continuous substrate rotation. A theoretical model is provided to describe this effect.

Lα and Mαβ X-ray production cross-sections of Bi by 6-30 keV electron impact

NASA Astrophysics Data System (ADS)

Liang, Y.; Xu, M. X.; Yuan, Y.; Wu, Y.; Qian, Z. C.; Chang, C. H.; Mei, C. S.; Zhu, J. J.; Moharram, K.

2017-12-01

In this paper, the Lα and Mαβ X-ray production cross-sections for Bi impacted by 6-30 keV electron have been measured. The experiments were performed at a Scanning Electron Microscope equipped with a silicon drift detector. The thin film with thick C substrate and the thin film deposited on self-supporting thin C film were both used as the targets to make a comparison. For the thick carbon substrate target, the Monte Carlo method has been used to eliminate the contribution of backscattering particles. The measured data are compared with the DWBA theoretical model and the experimental results in the literature. The experimental data for the thin film with thick C substrate target and the thin film deposited on self-supporting thin C film target are within reasonable gaps. The DWBA theoretical model gives good fit to the experimental data both for L- and M- shells. Besides, we also analyze the reasons why the discrepancies exist between our measurements and the experimental results in the literature.

Scalable high-mobility MoS2 thin films fabricated by an atmospheric pressure chemical vapor deposition process at ambient temperature

NASA Astrophysics Data System (ADS)

Huang, Chung-Che; Al-Saab, Feras; Wang, Yudong; Ou, Jun-Yu; Walker, John C.; Wang, Shuncai; Gholipour, Behrad; Simpson, Robert E.; Hewak, Daniel W.

2014-10-01

Nano-scale MoS2 thin films are successfully deposited on a variety of substrates by atmospheric pressure chemical vapor deposition (APCVD) at ambient temperature, followed by a two-step annealing process. These annealed MoS2 thin films are characterized with scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), micro-Raman, X-ray diffraction (XRD), transmission electron microscopy (TEM), UV-VIS-NIR spectrometry, photoluminescence (PL) and Hall Effect measurement. Key optical and electronic properties of APCVD grown MoS2 thin films are determined. This APCVD process is scalable and can be easily incorporated with conventional lithography as the deposition is taking place at room temperature. We also find that the substrate material plays a significant role in the crystalline structure formation during the annealing process and single crystalline MoS2 thin films can be achieved by using both c-plane ZnO and c-plane sapphire substrates. These APCVD grown nano-scale MoS2 thin films show great promise for nanoelectronic and optoelectronic applications.

Electronic structure of Fe1.08Te bulk crystals and epitaxial FeTe thin films on Bi2Te3

NASA Astrophysics Data System (ADS)

Arnold, Fabian; Warmuth, Jonas; Michiardi, Matteo; Fikáček, Jan; Bianchi, Marco; Hu, Jin; Mao, Zhiqiang; Miwa, Jill; Singh, Udai Raj; Bremholm, Martin; Wiesendanger, Roland; Honolka, Jan; Wehling, Tim; Wiebe, Jens; Hofmann, Philip

2018-02-01

The electronic structure of thin films of FeTe grown on Bi2Te3 is investigated using angle-resolved photoemission spectroscopy, scanning tunneling microscopy and first principles calculations. As a comparison, data from cleaved bulk Fe1.08Te taken under the same experimental conditions is also presented. Due to the substrate and thin film symmetry, FeTe thin films grow on Bi2Te3 in three domains, rotated by 0°, 120°, and 240°. This results in a superposition of photoemission intensity from the domains, complicating the analysis. However, by combining bulk and thin film data, it is possible to partly disentangle the contributions from three domains. We find a close similarity between thin film and bulk electronic structure and an overall good agreement with first principles calculations, assuming a p-doping shift of 65 meV for the bulk and a renormalization factor of around two. By tracking the change of substrate electronic structure upon film growth, we find indications of an electron transfer from the FeTe film to the substrate. No significant change of the film’s electronic structure or doping is observed when alkali atoms are dosed onto the surface. This is ascribed to the film’s high density of states at the Fermi energy. This behavior is also supported by the ab initio calculations.

Cross-sectional TEM specimen preparation for W/B{sub 4}C multilayer sample using FIB

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mondal, Puspen, E-mail: puspen@rrcat.gov.in; Pradhan, P. C.; Tiwari, Pragya

2016-05-23

A recent emergence of a cross-beam scanning electron microscopy (SEM)/focused-ion-beam (FIB) system have given choice to fabricate cross-sectional transmission electron microscopy (TEM) specimen of thin film multilayer sample. A 300 layer pair thin film multilayer sample of W/B{sub 4}C was used to demonstrate the specimen lift-out technique in very short time as compared to conventional cross-sectional sample preparation technique. To get large area electron transparent sample, sample prepared by FIB is followed by Ar{sup +} ion polishing at 2 kV with grazing incident. The prepared cross-sectional sample was characterized by transmission electron microscope.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yin, Congfei; Liang, Xiaojuan, E-mail: lxj6126@126

The titanate, is a material of interest for various energy applications, including photovoltaics, catalysts, and high-rate energy storage devices. Herein, its related materials, CuO/CaTi{sub 4}O{sub 9} [CCTO] thin films, were successfully fabricated on SrTiO{sub 3} (100) substrates by RF magnetron sputtering assisted with subsequent oxygen annealing. This obtained CCTO thin films were then systemically studied by X-ray powder diffraction (XRD), atomic force microscopy (AFM), scan electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and high-resolution transmission electron microscopy (HRTEM). It was found that CuO and CaTi{sub 4}O{sub 9} (001) particles were closely accumulated together on the surface of the substrate inmore » the annealing process after comparing with that of the as-prepared thin film, which was verified by SEM and AFM results. Furthermore, we investigated the third-order nonlinear optical (NLO) properties of the as-prepared and annealed CCTO thin film by means of the Z-scan technique using 650 nm femtosecond laser pulse. Post-deposition oxygen annealing was found to modify the morphological characteristics of the films, resulting in enhancing their NLO properties. The observation of NLO performance of annealed CCTO thin film indicates that RF magnetron sputtering is a feasible method for the fabrication of optical thin films, which can be expanded to fabricate other NLO materials from the corresponding dispersions. Naturally, we concluded that the CCTO thin film occupy a better NLO property, and thus enlarge its application in nonlinear optics. - Highlights: • The CCTO thin film was prepared using the RF magnetron sputtering and oxygen annealing. • The film was prepared on the SrTiO{sub 3}(100) substrates with a Ca{sub 2}CuO{sub 3} target. • The oxygen annealing was found can effectively enhance the film quality and NLO property. • The film was characterized using XPS, SEM, AFM, TEM, XRD and Z-scan techniques.« less

Wireless digital pressure gauge based on nanomaterials

NASA Astrophysics Data System (ADS)

Abay, Dilyara; Otarbay, Zhuldyz; Token, Madengul; Guseinov, Nazim; Muratov, Mukhit; Gabdullin, Maratbek; Ismailov, Daniyar

2018-03-01

In the article studies the efficiency of using nanostructured nickel copper films as thin films for bending sensors. Thin films of nickel-copper alloy were deposited using magnetron sputtering technology followed by the appropriate masks. Scanning electron microscopy (SEM) and energy- dispersive X-ray spectroscopy (EDS) techniques were used to examine structure and surface of the Ni Cu coatings. The results of the bending sensors result indicated that the Ni Cu thin film strain gauge showed an excellent sensitive.

Reprint of: Atmospheric scanning electron microscope observes cells and tissues in open medium through silicon nitride film.

PubMed

Nishiyama, Hidetoshi; Suga, Mitsuo; Ogura, Toshihiko; Maruyama, Yuusuke; Koizumi, Mitsuru; Mio, Kazuhiro; Kitamura, Shinichi; Sato, Chikara

2010-11-01

Direct observation of subcellular structures and their characterization is essential for understanding their physiological functions. To observe them in open environment, we have developed an inverted scanning electron microscope with a detachable, open-culture dish, capable of 8 nm resolution, and combined with a fluorescence microscope quasi-simultaneously observing the same area from the top. For scanning electron microscopy from the bottom, a silicon nitride film window in the base of the dish maintains a vacuum between electron gun and open sample dish while allowing electrons to pass through. Electrons are backscattered from the sample and captured by a detector under the dish. Cells cultured on the open dish can be externally manipulated under optical microscopy, fixed, and observed using scanning electron microscopy. Once fine structures have been revealed by scanning electron microscopy, their component proteins may be identified by comparison with separately prepared fluorescence-labeled optical microscopic images of the candidate proteins, with their heavy-metal-labeled or stained ASEM images. Furthermore, cell nuclei in a tissue block stained with platinum-blue were successfully observed without thin-sectioning, which suggests the applicability of this inverted scanning electron microscope to cancer diagnosis. This microscope visualizes mesoscopic-scale structures, and is also applicable to non-bioscience fields including polymer chemistry. Copyright © 2010 Elsevier Inc. All rights reserved.

Surface Diagnostics in Tribology Technology and Advanced Coatings Development

NASA Technical Reports Server (NTRS)

Miyoshi, Kazuhisa

1999-01-01

This paper discusses the methodologies used for surface property measurement of thin films and coatings, lubricants, and materials in the field of tribology. Surface diagnostic techniques include scanning electron microscopy, transmission electron microscopy, atomic force microscopy, stylus profilometry, x-ray diffraction, electron diffraction, Raman spectroscopy, Rutherford backscattering, elastic recoil spectroscopy, and tribology examination. Each diagnostic technique provides specific measurement results in its own unique way. In due course it should be possible to coordinate the different pieces of information provided by these diagnostic techniques into a coherent self-consistent description of the surface properties. Examples are given on the nature and character of thin diamond films.

Characterization of Thin Film Materials using SCAN meta-GGA, an Accurate Nonempirical Density Functional

DOE Office of Scientific and Technical Information (OSTI.GOV)

Buda, I. G.; Lane, C.; Barbiellini, B.

We discuss self-consistently obtained ground-state electronic properties of monolayers of graphene and a number of ’beyond graphene’ compounds, including films of transition-metal dichalcogenides (TMDs), using the recently proposed strongly constrained and appropriately normed (SCAN) meta-generalized gradient approximation (meta-GGA) to the density functional theory. The SCAN meta-GGA results are compared with those based on the local density approximation (LDA) as well as the generalized gradient approximation (GGA). As expected, the GGA yields expanded lattices and softened bonds in relation to the LDA, but the SCAN meta-GGA systematically improves the agreement with experiment. Our study suggests the efficacy of the SCAN functionalmore » for accurate modeling of electronic structures of layered materials in high-throughput calculations more generally.« less

Characterization of Thin Film Materials using SCAN meta-GGA, an Accurate Nonempirical Density Functional

DOE PAGES

Buda, I. G.; Lane, C.; Barbiellini, B.; ...

2017-03-23

We discuss self-consistently obtained ground-state electronic properties of monolayers of graphene and a number of ’beyond graphene’ compounds, including films of transition-metal dichalcogenides (TMDs), using the recently proposed strongly constrained and appropriately normed (SCAN) meta-generalized gradient approximation (meta-GGA) to the density functional theory. The SCAN meta-GGA results are compared with those based on the local density approximation (LDA) as well as the generalized gradient approximation (GGA). As expected, the GGA yields expanded lattices and softened bonds in relation to the LDA, but the SCAN meta-GGA systematically improves the agreement with experiment. Our study suggests the efficacy of the SCAN functionalmore » for accurate modeling of electronic structures of layered materials in high-throughput calculations more generally.« less

Ultrafast amorphization in Ge(10)Sb(2)Te(13) thin film induced by single femtosecond laser pulse.

PubMed

Konishi, Mitsutaka; Santo, Hisashi; Hongo, Yuki; Tajima, Kazuyuki; Hosoi, Masaharu; Saiki, Toshiharu

2010-06-20

We demonstrate amorphization in a Ge(10)Sb(2)Te(13) (GST) thin film through a nonthermal process by femtosecond electronic excitation. Amorphous recording marks were formed by irradiation with a single femtosecond pulse, and were confirmed to be recrystallized by laser thermal annealing. Scanning electron microscope observations revealed that amorphization occurred below the melting temperature. We performed femtosecond pump-probe measurements to investigate the amorphization dynamics of a GST thin film. We found that the reflectivity dropped abruptly within 500fs after excitation by a single pulse and that a small change in the reflectivity occurred within 5ps of this drop.

An electro-conductive organic coating for scanning electron microscopy (déjà vu)

NASA Astrophysics Data System (ADS)

Burnett, Bryan R.

2014-09-01

An organic compound, originally marketed as an antistatic, can form an extremely thin electro-conductive coating upon drying. A scanning electron microscope (SEM) application for this compound was first explored in the late 1960s. A coating of this compound eliminates the need for carbon or gold coating in some applications. It is well suited for the viewing of fabric samples and associated gunshot residue (GSR) in the SEM and makes it possible to quickly analyze fabric bullet wipe and bore wipe GSR. Fabric samples can also be examined for GSR from intermediate-range shots to estimate muzzle-target distances. Scanning

A conceptual design study for a two-dimensional, electronically scanned thinned array radiometer

NASA Technical Reports Server (NTRS)

Mutton, Philip; Chromik, Christopher C.; Dixon, Iain; Statham, Richard B.; Stillwagen, Frederic H.; Vontheumer, Alfred E.; Sasamoto, Washito A.; Garn, Paul A.; Cosgrove, Patrick A.; Ganoe, George G.

1993-01-01

A conceptual design for the Two-Dimensional, Electronically Steered Thinned Array Radiometer (ESTAR) is described. This instrument is a synthetic aperture microwave radiometer that operates in the L-band frequency range for the measurement of soil moisture and ocean salinity. Two auxiliary instruments, an 8-12 micron, scanning infrared radiometer and a 0.4-1.0 micron, charge coupled device (CCD) video camera, are included to provided data for sea surface temperature measurements and spatial registration of targets respectively. The science requirements were defined by Goddard Space Flight Center. Instrument and the spacecraft configurations are described for missions using the Pegasus and Taurus launch vehicles. The analyses and design trades described include: estimations of size, mass and power, instrument viewing coverage, mechanical design trades, structural and thermal analyses, data and communications performance assessments, and cost estimation.

Microstructural homogeneity of support silk spun by Eriophora fuliginea (C.L. Koch) determined by scanning X-ray microdiffraction

NASA Astrophysics Data System (ADS)

Riekel, C.; Craig, C. L.; Burghammer, M.; Müller, M.

2001-01-01

Scanning X-ray microdiffraction (SXD) permits the 'imaging' in-situ of crystalline phases, crystallinity and texture in whole biopolymer samples on the micrometre scale. SXD complements transmission electron microscopy (TEM) techniques, which reach sub-nanometre lateral resolution but require thin sections and a vacuum environment. This is demonstrated using a support thread from a web spun by the orb-weaving spider Eriophora fuliginea (C.L. Koch). Scanning electron microscopy (SEM) shows a central thread composed of two fibres to which thinner fibres are loosely attached. SXD of a piece of support thread approximately 60 µm long shows in addition the presence of nanometre-sized crystallites with the β-poly(L-alanine) structure in all fibres. The crystallinity of the thin fibres appears to be higher than that of the central thread, which probably reflects a higher polyalanine content of the fibroins. The molecular axis of the polymer chains in the central thread is orientated parallel to the macroscopic fibre axis, but in the thin fibres the molecular axis is tilted by about 71° to the macroscopic fibre axis. A helical model is tentatively proposed to describe this morphology. The central thread has a homogeneous distribution of crystallinity along the macroscopic fibre axis.

Synthesis and characterization of Copper/Cobalt/Copper/Iron nanostructurated films with magnetoresistive properties

NASA Astrophysics Data System (ADS)

Ciupinǎ, Victor; Prioteasa, Iulian; Ilie, Daniela; Manu, Radu; Petrǎşescu, Lucian; Tutun, Ştefan Gabriel; Dincǎ, Paul; MustaÅ£ǎ, Ion; Lungu, Cristian Petricǎ; Jepu, IonuÅ£; Vasile, Eugeniu; Nicolescu, Virginia; Vladoiu, Rodica

2017-02-01

Copper/Cobalt/Copper/Iron thin films were synthesized in order to obtain nanostructured materials with special magnetoresistive properties. The multilayer films were deposited on silicon substrates. In this respect we used Thermionic Vacuum Arc Discharge Method (TVA). The benefit of this deposition technique is the ability to have a controlled range of thicknesses starting from few nanometers to hundreds of nanometers. The purity of the thin films was insured by a high vacuum pressure and a lack of any kind of buffer gas inside the coating chamber. The morphology and structure of the thin films were analyzed using Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) Techniques and Energy Dispersive X-ray Spectroscopy (EDXS). Magnetoresistive measurement results depict that thin films possess Giant Magneto-Resistance Effect (GMR). Magneto-Optic-Kerr Effect (MOKE) studies were performed to characterize the magnetic properties of these thin films.

Facile synthesis and photo electrochemical performance of SnSe thin films

NASA Astrophysics Data System (ADS)

Pusawale, S. N.; Jadhav, P. S.; Lokhande, C. D.

2018-05-01

Orthorhombic structured SnSe thin films are synthesized via SILAR (successive ionic layer adsorption and reaction) method on glass substrates. The structural properties of thin films are characterized by x-ray diffraction, scanning electron microscopy studies from which nanoparticles with an elongated shape and hydrophilic behavior are observed. UV -VIS absorption spectroscopy study showed the maximum absorption in the visible region with a direct band gap of 1.55 eV. The photo electrochemical study showed p-type electrical conductivity.

Atomic Layer-Deposited Titanium-Doped Vanadium Oxide Thin Films and Their Thermistor Applications

DOE PAGES

Wang, Shuyu; Yu, Shifeng; Lu, Ming; ...

2016-11-30

In this paper, we report the enhancement in the temperature coefficient of resistance (TCR) of atomic layer-deposited vanadium oxide thin films through the doping of titanium oxide. The Hall effect measurement provides a potential explanation for the phenomenon. The composition and morphology of the thin films are investigated by x-ray diffraction and scanning electron microscopy techniques. The high TCR, good uniformity, and low processing temperature of the material make it a good candidate for thermistor application.

DEVELOPMENT OF LiCo0.90Mg0.05Al0.05O2 THIN FILMS BY PULSED LASER DEPOSITION TECHNIQUE

NASA Astrophysics Data System (ADS)

Vasanthi, R.; Ruthmangani, I.; Manoravi, P.; Joseph, M.; Kesavamoorthy, R.; Sundar, C.; Selladurai, S.

LiCo0.90Mg0.05Al0.05O2 bulk powders are synthesized using combustion process and made into a thin film by depositing on silicon wafer using a pulsed laser ablation technique. A comparative study by SEM (Scanning Electron Microscope) XRD (X-ray diffraction), Infrared spectroscopy and Raman Spectroscopy is performed on both bulk and PLD thin films.

Preliminary results on complex ceramic layers deposition by atmospheric plasma spraying

NASA Astrophysics Data System (ADS)

Florea, Costel; Bejinariu, Costicǎ; Munteanu, Corneliu; Cimpoeşu, Nicanor

2017-04-01

In this article we obtain thin layers from complex ceramic powders using industrial equipment based on atmospheric plasma spraying. We analyze the influence of the substrate material roughness on the quality of the thin layers using scanning electron microscopy (SEM) and X-ray dispersive energy analyze (EDAX). Preliminary results present an important dependence between the surface state and the structural and chemical homogeneity.

Ballistic-Electron-Emission Microscope

NASA Technical Reports Server (NTRS)

Kaiser, William J.; Bell, L. Douglas

1990-01-01

Ballistic-electron-emission microscope (BEEM) employs scanning tunneling-microscopy (STM) methods for nondestructive, direct electrical investigation of buried interfaces, such as interface between semiconductor and thin metal film. In BEEM, there are at least three electrodes: emitting tip, biasing electrode, and collecting electrode, receiving current crossing interface under investigation. Signal-processing device amplifies electrode signals and converts them into form usable by computer. Produces spatial images of surface by scanning tip; in addition, provides high-resolution images of buried interface under investigation. Spectroscopic information extracted by measuring collecting-electrode current as function of one of interelectrode voltages.

Going for green

NASA Astrophysics Data System (ADS)

Extance, Andy

2010-05-01

Thousands of times per second a point of light turns on and off, moving side to side, top to bottom. It is a rhythm that ticks around the world, illuminating living rooms and office desks in the process. However, the cathode-ray TVs and monitors that metronomically fire electron guns at viewers - who are shielded only by thin sheets of glass - are rapidly being replaced by flat-screen technologies. Yet as the creation of images using scanning electron beams fades into history, a new form of technology is emerging that builds up pictures by scanning with light.

Method for observation of deembedded sections of fish gonad by scanning electron microscopy

NASA Astrophysics Data System (ADS)

Mao, Lian-Ju

2000-09-01

This article reports a method for examining the intracellular structure of fish gonads using a scanning electron microscope(SEM). The specimen preparation procedure is similar to that for transmission electron microscopy wherein samples cut into semi-thin sections are fixed and embedded in plastic. The embedment matrix was removed by solvents. Risen-free specimens could be observed by SEM. The morphology of matured sperms in the gonad was very clear, and the oocyte internal structures appeared in three-dimensional images. Spheroidal nucleoli and yolk vesicles and several bundles of filaments adhered on the nucleoli could be viewed by SEM for the first time.

Thin films of a ferroelectric phenazine/chloranilic acid organic cocrystal

NASA Astrophysics Data System (ADS)

Thompson, Nicholas J.; Jandl, Adam C.; Spalenka, Josef W.; Evans, Paul G.

2011-07-01

Phenazine-chloranilic acid cocrystal thin films can be formed by vacuum evaporation of the component molecules onto cooled substrates. Fluxes of phenazine and chloranilic acid were provided from separate sublimation sources, from which the cocrystalline phase can be formed under a wide range of impingement rates of the component molecules. Substrates consisted of Au or Ni thin films on Si wafers, cooled to 100-140 K during deposition. X-ray diffraction and scanning electron microscopy show that this process yields polycrystalline thin films of the cocrystal with voids between crystalline grains. The relative intensities of X-ray reflections differ from reported intensities of polycrystalline powders, suggesting that the films have an anisotropic distribution of crystallographic orientations. The cocrystalline thin films have an effective dielectric constant of 13 at room temperature, increasing at lower temperatures and exhibiting a broad maximum near 200 K. The means to grow thin films of organic ferroelectric materials will allow the integration of new functionalities into organic electronic device structures, including capacitors and field-effect transistors.

Nanostructure CdS/ZnO heterojunction configuration for photocatalytic degradation of Methylene blue

NASA Astrophysics Data System (ADS)

Velanganni, S.; Pravinraj, S.; Immanuel, P.; Thiruneelakandan, R.

2018-04-01

In the present manuscript, thin films of Zinc Oxide (ZnO) have been deposited on a FTO substrate using a simple successive ionic layer adsorption and reaction (SILAR) and chemical bath deposition (CBD) method. Cadmium Sulphide (CdS) nanoparticles are sensitized over ZnO thin films using SILAR method. The synthesized nanostructured CdS/ZnO heterojunction thin films was characterized by X-ray diffraction (XRD), Scanning electron microscopy (SEM), High resolution transmission electron microscopy (HR-TEM), X-ray photoelectron spectroscopy (XPS), UV-Vis spectroscopy and Raman spectroscopy techniques. The band gap of CdS nanoparticles over ZnO nanostructure was found to be about 3.20 eV. The photocatalytic activities of the deposited CdS/ZnO thin films were evaluated by the degradation of methylene blue (MB) in an aqueous solution under sun light irradiation.

Correlation of live-cell imaging with volume scanning electron microscopy.

PubMed

Lucas, Miriam S; Günthert, Maja; Bittermann, Anne Greet; de Marco, Alex; Wepf, Roger

2017-01-01

Live-cell imaging is one of the most widely applied methods in live science. Here we describe two setups for live-cell imaging, which can easily be combined with volume SEM for correlative studies. The first procedure applies cell culture dishes with a gridded glass support, which can be used for any light microscopy modality. The second approach is a flow-chamber setup based on Ibidi μ-slides. Both live-cell imaging strategies can be followed up with serial blockface- or focused ion beam-scanning electron microscopy. Two types of resin embedding after heavy metal staining and dehydration are presented making best use of the particular advantages of each imaging modality: classical en-bloc embedding and thin-layer plastification. The latter can be used only for focused ion beam-scanning electron microscopy, but is advantageous for studying cell-interactions with specific substrates, or when the substrate cannot be removed. En-bloc embedding has diverse applications and can be applied for both described volume scanning electron microscopy techniques. Finally, strategies for relocating the cell of interest are discussed for both embedding approaches and in respect to the applied light and scanning electron microscopy methods. Copyright © 2017 Elsevier Inc. All rights reserved.

Synthesis, characterization, and photocatalytic properties of nanocrystalline NZO thin films

NASA Astrophysics Data System (ADS)

Aryanto, D.; Hastuti, E.; Husniya, N.; Sudiro, T.; Nuryadin, B. W.

2018-03-01

Nanocrystalline Ni-doped ZnO (NZO) thin films were synthesized on glass substrate using sol-gel spin coating methods. The effect of annealing on the structural and optical properties of nanocrystalline thin film was studied using X-ray diffractometer (XRD), field emission scanning electron microscopy (FESEM), UV-VIS spectrophotometry, and photoluminescence (PL). The results showed that the annealing temperature strongly influenced the physical properties of nanocrystalline NZO thin films. The photocatalytic properties of nanocrystalline NZO thin films were evaluated using an aqueous solution of Rhodamine-B. The photocatalytic activity of nanocrystalline NZO thin films increased with the increase of annealing temperature. The results indicated that the structure, morphology, and band gap energy of nanocrystalline NZO thin films played an important role in photocatalytic activity.

Role of target-substrate distance on the growth of CuInSe{sub 2} thin films by pulsed laser ablation technique

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rawat, Kusum; Dhruvashi; Department of Electronic Science, University of Delhi South Campus, Delhi 110021

2016-05-06

CuInSe{sub 2} thin films have been deposited on corning glass substrates by pulsed laser ablation technique. The chamber pressure and substrate temperature was maintained at 1 × 10{sup −6} torr and 550°C respectively during deposition of the films. The influence of target to substrate (T-S) distance on the structural and optical properties of thin films have been investigated by grazing incidence x-ray diffraction, Raman spectroscopy, scanning electron microscope and UV-Vis-NIR spectroscopy. The study reveals that thin films crystallized in a chalcopyrite structure with highly preferential orientation along (112) plane. Optimum T-S distance has been attained for the growth of thinmore » films with large grain size. An intense Raman peak at 174 cm{sup −1} corresponding to dominant A{sub 1} vibration mode is gradually shifted to smaller wavenumber with the increase in T-S distance. The optical bandgap energy of the films was evaluated and found to vary with the T-S distance. The bandgap tailing was observed to obey the Urbach rule and the Urbach energy was also calculated for the films. Scanning electron micrographs depicts uniform densely packed grains and EDAX studies revealed the elemental composition of CuInSe{sub 2} thin films.« less

Investigation of the Optical and Electronic Properties of Crystalline Organic Materials

DTIC Science & Technology

1990-06-14

38 (A) EFFECTS OF DEPOSTION RATE ---------------- 38 0 (B) EFFECTS OF SUBSTRATE TEMPERATURE ------ 40 11.5 ANISOTROPIES IN CRYSTALLINE ORGANIC THIN...depostion rate .- ------------------------------------------------------------------ 41 Fig. 2.10: Scanning electron micrographs showing the surface...materials grown be lattice-matched. Hence, relatively strain -free heterostructures using materials with large lattice-mismatch can be realized by the

In situ observation of the impact of surface oxidation on the crystallization mechanism of GeTe phase-change thin films by scanning transmission electron microscopy

NASA Astrophysics Data System (ADS)

Berthier, R.; Bernier, N.; Cooper, D.; Sabbione, C.; Hippert, F.; Noé, P.

2017-09-01

The crystallization mechanisms of prototypical GeTe phase-change material thin films have been investigated by in situ scanning transmission electron microscopy annealing experiments. A novel sample preparation method has been developed to improve sample quality and stability during in situ annealing, enabling quantitative analysis and live recording of phase change events. Results show that for an uncapped 100 nm thick GeTe layer, exposure to air after fabrication leads to composition changes which promote heterogeneous nucleation at the oxidized surface. We also demonstrate that protecting the GeTe layer with a 10 nm SiN capping layer prevents nucleation at the surface and allows volume nucleation at a temperature 50 °C higher than the onset of crystallization in the oxidized sample. Our results have important implications regarding the integration of these materials in confined memory cells.

Investigation of AlGaN/GaN high electron mobility transistor structures on 200-mm silicon (111) substrates employing different buffer layer configurations.

PubMed

Lee, H-P; Perozek, J; Rosario, L D; Bayram, C

2016-11-21

AlGaN/GaN high electron mobility transistor (HEMT) structures are grown on 200-mm diameter Si(111) substrates by using three different buffer layer configurations: (a) Thick-GaN/3 × {Al x Ga 1-x N}/AlN, (b) Thin-GaN/3 × {Al x Ga 1-x N}/AlN, and (c) Thin-GaN/AlN, so as to have crack-free and low-bow (<50 μm) wafer. Scanning electron microscopy, energy-dispersive X-ray spectroscopy, high resolution-cross section transmission electron microscopy, optical microscopy, atomic-force microscopy, cathodoluminescence, Raman spectroscopy, X-ray diffraction (ω/2θ scan and symmetric/asymmetric ω scan (rocking curve scan), reciprocal space mapping) and Hall effect measurements are employed to study the structural, optical, and electrical properties of these AlGaN/GaN HEMT structures. The effects of buffer layer stacks (i.e. thickness and content) on defectivity, stress, and two-dimensional electron gas (2DEG) mobility and 2DEG concentration are reported. It is shown that 2DEG characteristics are heavily affected by the employed buffer layers between AlGaN/GaN HEMT structures and Si(111) substrates. Particularly, we report that in-plane stress in the GaN layer affects the 2DEG mobility and 2DEG carrier concentration significantly. Buffer layer engineering is shown to be essential for achieving high 2DEG mobility (>1800 cm 2 /V∙s) and 2DEG carrier concentration (>1.0 × 10 13  cm -2 ) on Si(111) substrates.

Investigation of AlGaN/GaN high electron mobility transistor structures on 200-mm silicon (111) substrates employing different buffer layer configurations

PubMed Central

Lee, H.-P.; Perozek, J.; Rosario, L. D.; Bayram, C.

2016-01-01

AlGaN/GaN high electron mobility transistor (HEMT) structures are grown on 200-mm diameter Si(111) substrates by using three different buffer layer configurations: (a) Thick-GaN/3 × {AlxGa1−xN}/AlN, (b) Thin-GaN/3 × {AlxGa1−xN}/AlN, and (c) Thin-GaN/AlN, so as to have crack-free and low-bow (<50 μm) wafer. Scanning electron microscopy, energy-dispersive X-ray spectroscopy, high resolution-cross section transmission electron microscopy, optical microscopy, atomic-force microscopy, cathodoluminescence, Raman spectroscopy, X-ray diffraction (ω/2θ scan and symmetric/asymmetric ω scan (rocking curve scan), reciprocal space mapping) and Hall effect measurements are employed to study the structural, optical, and electrical properties of these AlGaN/GaN HEMT structures. The effects of buffer layer stacks (i.e. thickness and content) on defectivity, stress, and two-dimensional electron gas (2DEG) mobility and 2DEG concentration are reported. It is shown that 2DEG characteristics are heavily affected by the employed buffer layers between AlGaN/GaN HEMT structures and Si(111) substrates. Particularly, we report that in-plane stress in the GaN layer affects the 2DEG mobility and 2DEG carrier concentration significantly. Buffer layer engineering is shown to be essential for achieving high 2DEG mobility (>1800 cm2/V∙s) and 2DEG carrier concentration (>1.0 × 1013 cm−2) on Si(111) substrates. PMID:27869222

Isolation, electron microscopic imaging, and 3-D visualization of native cardiac thin myofilaments.

PubMed

Spiess, M; Steinmetz, M O; Mandinova, A; Wolpensinger, B; Aebi, U; Atar, D

1999-06-15

An increasing number of cardiac diseases are currently pinpointed to reside at the level of the thin myofilaments (e.g., cardiomyopathies, reperfusion injury). Hence the aim of our study was to develop a new method for the isolation of mammalian thin myofilaments suitable for subsequent high-resolution electron microscopic imaging. Native cardiac thin myofilaments were extracted from glycerinated porcine myocardial tissue in the presence of protease inhibitors. Separation of thick and thin myofilaments was achieved by addition of ATP and several centrifugation steps. Negative staining and subsequent conventional and scanning transmission electron microscopy (STEM) of thin myofilaments permitted visualization of molecular details; unlike conventional preparations of thin myofilaments, our method reveals the F-actin moiety and allows direct recognition of thin myofilament-associated porcine cardiac troponin complexes. They appear as "bulges" at regular intervals of approximately 36 nm along the actin filaments. Protein analysis using SDS-polyacrylamide gel electrophoresis revealed that only approximately 20% troponin I was lost during the isolation procedure. In a further step, 3-D helical reconstructions were calculated using STEM dark-field images. These 3-D reconstructions will allow further characterization of molecular details, and they will be useful for directly visualizing molecular alterations related to diseased cardiac thin myofilaments (e.g., reperfusion injury, alterations of Ca2+-mediated tropomyosin switch). Copyright 1999 Academic Press.

Tunneling-Electron-Induced Light Emission from Single Gold Nanoclusters.

PubMed

Yu, Arthur; Li, Shaowei; Czap, Gregory; Ho, W

2016-09-14

The coupling of tunneling electrons with the tip-nanocluster-substrate junction plasmon was investigated by monitoring light emission in a scanning tunneling microscope (STM). Gold atoms were evaporated onto the ∼5 Å thick Al2O3 thin film grown on the NiAl (110) surface where they formed nanoclusters 3-7 nm wide. Scanning tunneling spectroscopy (STS) of these nanoclusters revealed quantum-confined electronic states. Spatially resolved photon imaging showed localized emission hot spots. Size dependent study and light emission from nanocluster dimers further support the viewpoint that coupling of tunneling electrons to the junction plasmon is the main radiative mechanism. These results showed the potential of the STM to reveal the electronic and optical properties of nanoscale metallic systems in the confined geometry of the tunnel junction.

Optical Analysis of Iron-Doped Lead Sulfide Thin Films for Opto-Electronic Applications

NASA Astrophysics Data System (ADS)

Chidambara Kumar, K. N.; Khadeer Pasha, S. K.; Deshmukh, Kalim; Chidambaram, K.; Shakil Muhammad, G.

Iron-doped lead sulfide thin films were deposited on glass substrates using successive ionic layer adsorption and reaction method (SILAR) at room temperature. The X-ray diffraction pattern of the film shows a well formed crystalline thin film with face-centered cubic structure along the preferential orientation (1 1 1). The lattice constant is determined using Nelson Riley plots. Using X-ray broadening, the crystallite size is determined by Scherrer formula. Morphology of the thin film was studied using a scanning electron microscope. The optical properties of the film were investigated using a UV-vis spectrophotometer. We observed an increase in the optical band gap from 2.45 to 3.03eV after doping iron in the lead sulfide thin film. The cutoff wavelength lies in the visible region, and hence the grown thin films can be used for optoelectronic and sensor applications. The results from the photoluminescence study show the emission at 500-720nm. The vibrating sample magnetometer measurements confirmed that the lead sulfide thin film becomes weakly ferromagnetic material after doping with iron.

Synthesis, Fabrication and Characterization of ZnO-Based Thin Films Prepared by Sol-Gel Process and H2 Gas Sensing Performance

NASA Astrophysics Data System (ADS)

Dey, Anup; Roy, Subhashis; Sarkar, Subir Kumar

2018-03-01

In this paper, an attempt is made to deposit ZnO thin films using sol-gel process followed by dip-coating method on p-silicon (100) substrates for intended application as a hydrogen gas sensor owing to the low toxic nature and thermal stability of ZnO. The thin films are annealed under annealing temperatures of 350, 450 and 550 °C for 25 min. The crystalline quality of the fabricated thin films is then analyzed by field-emission scanning electron microscopy and transmission electron microscope. The gas sensing performance analysis of ZnO thin films is demonstrated at different annealing temperatures and hydrogen gas concentrations ranging from 100 to 3000 ppm. Results obtained show that the sensitivity is significantly improved as annealing temperature increases with maximum sensitivity being achieved at 550 °C annealing temperature and operating temperature of 150 °C. Hence, the modified ZnO thin films can be applicable as H2 gas sensing device showing to the improved performance in comparison with unmodified thin-film sensor.

Graphene Synthesis and Characterization

DTIC Science & Technology

2015-04-08

for synthesis electrochemical. - A Scanning Electron Microscope (SEM) (EVO MA from Carl Zeiss). 6 6. RESULTS AND...5, 2332-2339, 2011, High-Quality Thin graphene films from fast electrochemical exfoliation. [13] Da Hee Jung , Cheong Kang, Ji Eun Nam, Jin-Seok Kim

TEM characterization of nanodiamond thin films.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Qin, L.-C.; Zhou, D.; Krauss, A. R.

The microstructure of thin films grown by microwave plasma-enhanced chemical vapor deposition (MPCVD) from fullerene C{sub 60} precursors has been characterized by scanning electron microscopy (SEM), selected-area electron diffraction (SAED), bright-field electron microscopy, high-resolution electron microscopy (HREM), and parallel electron energy loss spectroscopy (PEELS). The films are composed of nanosize crystallites of diamond, and no graphitic or amorphous phases were observed. The diamond crystallite size measured from lattice images shows that most grains range between 3-5 nm, reflecting a gamma distribution. SAED gave no evidence of either sp2-bonded glassy carbon or sp3-bonded diamondlike amorphous carbon. The sp2-bonded configuration found inmore » PEELS was attributed to grain boundary carbon atoms, which constitute 5-10% of the total. Occasionally observed larger diamond grains tend to be highly faulted.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stöber, Laura, E-mail: laura.stoeber@tuwien.ac.at; Patocka, Florian, E-mail: florian.patocka@tuwien.ac.at; Schneider, Michael, E-mail: michael.schneider@tuwien.ac.at

In this paper, the authors report on the high temperature performance of sputter deposited molybdenum (Mo) and molybdenum nitride (Mo{sub 2}N) thin films. Various argon and nitrogen gas compositions are applied for thin film synthetization, and the amount of nitrogen incorporation is determined by Auger measurements. Furthermore, effusion measurements identifying the binding conditions of the nitrogen in the thin film are performed up to 1000 °C. These results are in excellent agreement with film stress and scanning electron microscope analyses, both indicating stable film properties up to annealing temperatures of 500 °C.

Morphology selection for cupric oxide thin films by electrodeposition.

PubMed

Dhanasekaran, V; Mahalingam, T; Chandramohan, R

2011-10-01

Polycrystalline cupric oxide thin films were deposited using alkaline solution bath employing cathodic electrodeposition method. The thin films were electrodeposited at various solution pH. The surface morphology and elemental analyzes of the films were studied using scanning electron microscopy (SEM) and energy dispersive X-ray analysis, respectively. SEM studies revealed that the surface morphology could be tailored suitably by adjusting the pH value during deposition. Mesh average on multiple lattice mode atomic force microscopy image was obtained and reported. Copyright © 2011 Wiley-Liss, Inc.

Exploring a new phenomenon in the bactericidal response of TiO2 thin films by Fe doping: Exerting the antimicrobial activity even after stoppage of illumination

NASA Astrophysics Data System (ADS)

Naghibi, Sanaz; Vahed, Shohreh; Torabi, Omid; Jamshidi, Amin; Golabgir, Mohammad Hossein

2015-02-01

Antibacterial properties of Fe-doped TiO2 thin films prepared on glass by the sol-gel hot-dipping technique were studied. The films were characterized by X-ray diffraction, field emission scanning electron microscopy, scanning probe microscopy and X-ray photoelectron spectroscopy. The photocatalytic activities were evaluated by measuring the decomposition rate of methylene blue under ultra violet and visible light. The antibacterial properties of the coatings were investigated against Escherichia coli, Staphylococcus aureus, Saccharomyces cerevisia and Aspergillus niger. The principle of incubation methods was also discussed. The results indicated that Fe doping of thin films eventuated in high antibacterial properties under visible light and this performance remained even after stoppage of illumination. This article tries to provide some explanation for this fact.

SnS thin films deposited by chemical bath deposition, dip coating and SILAR techniques

NASA Astrophysics Data System (ADS)

Chaki, Sunil H.; Chaudhary, Mahesh D.; Deshpande, M. P.

2016-05-01

The SnS thin films were synthesized by chemical bath deposition (CBD), dip coating and successive ionic layer adsorption and reaction (SILAR) techniques. In them, the CBD thin films were deposited at two temperatures: ambient and 70 °C. The energy dispersive analysis of X-rays (EDAX), X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM) and optical spectroscopy techniques were used to characterize the thin films. The electrical transport properties studies on the as-deposited thin films were done by measuring the I-V characteristics, DC electrical resistivity variation with temperature and the room temperature Hall effect. The obtained results are deliberated in this paper.

Synthesis of galium nitride thin films using sol-gel dip coating method

NASA Astrophysics Data System (ADS)

Hamid, Maizatul Akmam Ab; Ng, Sha Shiong

2017-12-01

In this research, gallium nitride (GaN) thin film were grown on silicon (Si) substrate by a low-cost sol-gel dip coating deposition method. The GaN precursor solution was prepared using gallium (III) nitrate hydrate powder, ethanol and diethanolamine as a starting material, solvent and surfactant respectively. The structural, morphological and optical characteristics of the deposited GaN thin film were investigated. Field-emission scanning electron microscopy observations showed that crack free and dense grains GaN thin films were formed. Energy dispersive X-ray analysis confirmed that the oxygen content in the deposited films was low. X-ray diffraction results revealed that deposited GaN thin films have hexagonal wurtzite structure.

New possibility on InZnO nano thin film for green emissive optoelectronic devices

NASA Astrophysics Data System (ADS)

Sugumaran, Sathish; Noor Bin Ahmad, Mohd; Faizal Jamlos, Mohd; Bellan, Chandar Shekar; Chandran, Sharmila; Sivaraj, Manoj

2016-04-01

Indium zinc oxide (InZnO) nano thin film was prepared from InZnO nanoparticles (NPs) by thermal evaporation technique. Fourier transform infrared spectroscopy showed the presence of metal-oxide bond. X-ray diffraction pattern revealed the mixed phase structure. The presence of elements In, Zn and O were identified from energy dispersive X-ray analysis. Size of the NPs was found to be 171 and 263 nm by transmission electron microscopy. Scanning electron microscopy image showed the spherical shape uniform morphology with uniform distribution grains. Photoluminescence spectrum exhibited a broad green emission for InZnO nano thin film. The acquired results of structure, smooth morphology and photoluminescence property suggested that the InZnO nano thin film to be a promising material for room temperature green emissive optoelectronic, laser diodes, solar cells and other optical devices.

Effect of deposition pressure on the microstructure and thermoelectric properties of epitaxial ScN(001) thin films sputtered onto MgO(001) substrates

DOE PAGES

Burmistrova, Polina V.; Zakharov, Dmitri N.; Favaloro, Tela; ...

2015-03-14

Four epitaxial ScN(001) thin films were successfully deposited on MgO(001) substrates by dc reactive magnetron sputtering at 2, 5, 10, and 20 mTorr in an Ar/N2 ambient atmosphere at 650 °C. The microstructure of the resultant films was analyzed by x-ray diffraction, scanning electron microscopy, and transmission electron microscopy. Electrical resistivity, electron mobility and concentration were measured using the room temperature Hall technique, and temperature dependent in-plain measurements of the thermoelectric properties of the ScN thin films were performed. The surface morphology and film crystallinity significantly degrade with increasing deposition pressure. The ScN thin film deposited at 20 mTorr exhibitsmore » the presence of <221> oriented secondary grains resulting in decreased electric properties and a low thermoelectric power factor of 0.5 W/m-K² at 800 K. ScN thin films grown at 5 and 10 mTorr are single crystalline, yielding the power factor of approximately 2.5 W/m-K² at 800 K. The deposition performed at 2 mTorr produces the highest quality ScN thin film with the electron mobility of 98 cm² V⁻¹ s⁻¹ and the power factor of 3.3 W/m-K² at 800 K.« less

Theory of the spatial resolution of (scanning) transmission electron microscopy in liquid water or ice layers.

PubMed

de Jonge, Niels

2018-04-01

The sample dependent spatial resolution was calculated for transmission electron microscopy (TEM) and scanning TEM (STEM) of objects (e.g., nanoparticles, proteins) embedded in a layer of liquid water or amorphous ice. The theoretical model includes elastic- and inelastic scattering, beam broadening, and chromatic aberration. Different contrast mechanisms were evaluated as function of the electron dose, the detection angle, and the sample configuration. It was found that the spatial resolution scales with the electron dose to the -1/4th power. Gold- and carbon nanoparticles were examined in the middle of water layers ranging from 0.01--10 µm thickness representing relevant classes of experiments in both materials science and biology. The optimal microscope settings differ between experimental configurations. STEM performs the best for gold nanoparticles for all layer thicknesses, while carbon is best imaged with phase-contrast TEM for thin layers but bright field STEM is preferred for thicker layers. The resolution was also calculated for a water layer enclosed between thin membranes. The influence of chromatic aberration correction for TEM was examined as well. The theory is broadly applicable to other types of materials and sample configurations. Copyright © 2018 Elsevier B.V. All rights reserved.

Scanning Electron Microscope Studies of Interactions between Agaricus bisporus (Lang) Sing Hyphae and Bacteria in Casing Soil

PubMed Central

Masaphy, Segula; Levanon, D.; Tchelet, R.; Henis, Y.

1987-01-01

Relationships between the hyphae of Agaricus bisporus (Lang) Sing and bacteria from the mushroom bed casing layer were examined with a scanning electron microscope. Hyphae growing in the casing layer differed morphologically from compost-grown hyphae. Whereas the compost contained thin single hyphae surrounded by calcium oxalate crystals, the casing layer contained mainly wide hyphae or mycelial strands without crystals. The bacterial population in the hyphal environment consisted of several types, some attached to the hyphae with filamentlike structures. This attachment may be important in stimulation of pinhead initiation. Images PMID:16347340

Collective Modes and Structural Modulation in Ni-Mn-Ga(Co) Martensite Thin Films Probed by Femtosecond Spectroscopy and Scanning Tunneling Microscopy.

PubMed

Schubert, M; Schaefer, H; Mayer, J; Laptev, A; Hettich, M; Merklein, M; He, C; Rummel, C; Ristow, O; Großmann, M; Luo, Y; Gusev, V; Samwer, K; Fonin, M; Dekorsy, T; Demsar, J

2015-08-14

The origin of the martensitic transition in the magnetic shape memory alloy Ni-Mn-Ga has been widely discussed. While several studies suggest it is electronically driven, the adaptive martensite model reproduced the peculiar nonharmonic lattice modulation. We used femtosecond spectroscopy to probe the temperature and doping dependence of collective modes, and scanning tunneling microscopy revealed the corresponding static modulations. We show that the martensitic phase can be described by a complex charge-density wave tuned by magnetic ordering and strong electron-lattice coupling.

Collective Modes and Structural Modulation in Ni-Mn-Ga(Co) Martensite Thin Films Probed by Femtosecond Spectroscopy and Scanning Tunneling Microscopy

NASA Astrophysics Data System (ADS)

Schubert, M.; Schaefer, H.; Mayer, J.; Laptev, A.; Hettich, M.; Merklein, M.; He, C.; Rummel, C.; Ristow, O.; Großmann, M.; Luo, Y.; Gusev, V.; Samwer, K.; Fonin, M.; Dekorsy, T.; Demsar, J.

2015-08-01

The origin of the martensitic transition in the magnetic shape memory alloy Ni-Mn-Ga has been widely discussed. While several studies suggest it is electronically driven, the adaptive martensite model reproduced the peculiar nonharmonic lattice modulation. We used femtosecond spectroscopy to probe the temperature and doping dependence of collective modes, and scanning tunneling microscopy revealed the corresponding static modulations. We show that the martensitic phase can be described by a complex charge-density wave tuned by magnetic ordering and strong electron-lattice coupling.

Scanning electron microscopy of a blister roof in dystrophic epidermolysis bullosa*

PubMed Central

de Almeida Jr., Hiram Larangeira; Monteiro, Luciane; Silva, Ricardo Marques e; Rocha, Nara Moreira; Scheffer, Hans

2013-01-01

In dystrophic epidermolysis bullosa the genetic defect of anchoring fibrils leads to cleavage beneath the basement membrane, with its consequent loss. We performed scanning electron microscopy of an inverted blister roof of a case of dystrophic epidermolysis bullosa, confirmed by immunomapping and gene sequencing. With a magnification of 2000 times a net attached to the blister roof could be easily identified. This net was composed of intertwined flat fibers. With higher magnifications, different fiber sizes could be observed, some thin fibers measuring around 80 nm and thicker ones measuring between 200 and 300 nm. PMID:24474107

Chapter 14: Electron Microscopy on Thin Films for Solar Cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Romero, Manuel; Abou-Ras, Daniel; Nichterwitz, Melanie

2016-07-22

This chapter overviews the various techniques applied in scanning electron microscopy (SEM) and transmission electron microscopy (TEM), and highlights their possibilities and also limitations. It gives the various imaging and analysis techniques applied on a scanning electron microscope. The chapter shows that imaging is divided into that making use of secondary electrons (SEs) and of backscattered electrons (BSEs), resulting in different contrasts in the images and thus providing information on compositions, microstructures, and surface potentials. Whenever aiming for imaging and analyses at scales of down to the angstroms range, TEM and its related techniques are appropriate tools. In many cases,more » also SEM techniques provide the access to various material properties of the individual layers, not requiring specimen preparation as time consuming as TEM techniques. Finally, the chapter dedicates to cross-sectional specimen preparation for electron microscopy. The preparation decides indeed on the quality of imaging and analyses.« less

Optical and structural properties of cobalt-permalloy slanted columnar heterostructure thin films

NASA Astrophysics Data System (ADS)

Sekora, Derek; Briley, Chad; Schubert, Mathias; Schubert, Eva

2017-11-01

Optical and structural properties of sequential Co-column-NiFe-column slanted columnar heterostructure thin films with an Al2O3 passivation coating are reported. Electron-beam evaporated glancing angle deposition is utilized to deposit the sequential multiple-material slanted columnar heterostructure thin films. Mueller matrix generalized spectroscopic ellipsometry data is analyzed with a best-match model approach employing the anisotropic Bruggeman effective medium approximation formalism to determine bulk-like and anisotropic optical and structural properties of the individual Co and NiFe slanted columnar material sub-layers. Scanning electron microscopy is applied to image the Co-NiFe sequential growth properties and to verify the results of the ellipsometric analysis. Comparisons to single-material slanted columnar thin films and optically bulk solid thin films are presented and discussed. We find that the optical and structural properties of each material sub-layer of the sequential slanted columnar heterostructure film are distinct from each other and resemble those of their respective single-material counterparts.

Structural, electrical and optical properties of nanostructured ZrO2 thin film deposited by SILAR method

NASA Astrophysics Data System (ADS)

Salodkar, R. V.; Belkhedkar, M. R.; Nemade, S. D.

2018-05-01

Successive Ionic Layer Adsorption and Reaction (SILAR) method has been employed to deposit nanocrystalline ZrO2 thin film of thickness 91 nm onto glass substrates using ZrOCl2.8H2O and NaOH as cationic and anionic precursors respectively. The structural and surface morphological characterizations have been carried out by means of X-ray diffraction and field emission scanning electron microscopy confirms the nanocrystalline nature of ZrO2 thin film. The direct optical band gap and activation energy of the ZrO2 thin film are found to be 4.74 and 0.80eV respectively.

AZO nanorods thin films by sputtering method

NASA Astrophysics Data System (ADS)

Rosli, A. B.; Shariffudin, S. S.; Awang, Z.; Herman, S. H.

2018-05-01

Al-doped zinc oxide (AZO) nanorods thin film were deposited on Au catalyst using RF sputtering at 300 °C. The 15 nm thickness Au catalyst were deposited on glass substrates by sputtering method followed by annealing for 15 min at 500 °C to form Au nanostructures on the glass substrate. The AZO thin films were then deposited on Au catalyst at different RF power ranging from 50 - 200 W. The morphology of AZO was characterized using Field Emission Scanning Electron Microscopy while X-ray Diffraction was used to examine crystallinity of AZO thin films. From this work, the AZO nanorods was found grow at 200 W RF power.

Nanowelding and patterning of silver nanowires via mask-free atmospheric cold plasma-jet scanning

NASA Astrophysics Data System (ADS)

Liu, Lang; Li, Han-Yu; Ye, Dong; Yu, Yao; Liu, Lin; Wu, Yue

2017-06-01

Silver nanowire (AgNW) thin film is a promising candidate to replace traditional indium tin oxide in optoelectronics applications. To date however, the widespread application of AgNW thin film is limited by the weak point contacts between individual AgNWs and the lack of facile patterning techniques. Here, we demonstrate a novel and facile method to not only nanoweld AgNW junctions but also pattern AgNW thin films via mask-free cold plasma-jet scanning in ambient conditions. After the plasma-jet nanowelding treatment, the morphology of AgNWs change substantially and the junctions are welded together. The nanowelded AgNWs-based thin film shows enhanced electrical and mechanical properties. On the other hand, after the plasma-jet patterning treatment, the AgNWs are etched and transformed into separated large particles. Different kinds of patterns are produced via this patterning technique. At last, a simple light emitting diode circuit is fabricated to demonstrate the suitability of the nanowelded and patterned AgNW electrodes for flexible electronic devices.

A simple way to obtain backscattered electron images in a scanning transmission electron microscope.

PubMed

Tsuruta, Hiroki; Tanaka, Shigeyasu; Tanji, Takayoshi; Morita, Chiaki

2014-08-01

We have fabricated a simple detector for backscattered electrons (BSEs) and incorporated the detector into a scanning transmission electron microscope (STEM) sample holder. Our detector was made from a 4-mm(2) Si chip. The fabrication procedure was easy, and similar to a standard transmission electron microscopy (TEM) sample thinning process based on ion milling. A TEM grid containing particle objects was fixed to the detector with a silver paste. Observations were carried out using samples of Au and latex particles at 75 and 200 kV. Such a detector provides an easy way to obtain BSE images in an STEM. © The Author 2014. Published by Oxford University Press on behalf of The Japanese Society of Microscopy. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Optimisation of growth of epitaxial Tl 2Ba 2Ca 1Cu 2O 8 superconducting thin films for electronic device applications

NASA Astrophysics Data System (ADS)

Michael, Peter C.; Johansson, L.-G.; Bengtsson, L.; Claeson, T.; Ivanov, Z. G.; Olsson, E.; Berastegui, P.; Stepantsov, E.

1994-12-01

Epitaxial thin films of Tl 2Ba 2Ca 1Cu 2O 8 (Tl-2212) superconductor have been grown on single crystal (100) lanthanum aluminate (LaAlO 3) substrates by a two stage process: laser ablation of a BaCaCuO (0212) sintered target and post-deposition anneal ex-situ in a thallium environment. The films are c-axis oriented with in-plane epitaxy as determined by x-ray diffraction (XRD θ-2θ and φ-scans). Superconducting transition temperatures as high as 105.5K have been obtained both from four-probe resistance and a.c. magnetic susceptibility measurements. Film morphology and chemical composition have been assessed by scanning electron microscopy (SEM) and energy dispersive x-ray analysis (EDX). Sensitivity of the precursor film to environmental exposure has proven to be a determining factor in the reproducibility of film growth characteristics. The effect of oxygen partial pressure and substrate temperature used in the precursor film synthesis, as well as the thallium annealing temperature and duration, on the growth of Tl-2212 thin films is reported.

Biocompatible cephalosporin-hydroxyapatite-poly(lactic-co-glycolic acid)-coatings fabricated by MAPLE technique for the prevention of bone implant associated infections

NASA Astrophysics Data System (ADS)

Rădulescu, Dragoş; Grumezescu, Valentina; Andronescu, Ecaterina; Holban, Alina Maria; Grumezescu, Alexandru Mihai; Socol, Gabriel; Oprea, Alexandra Elena; Rădulescu, Marius; Surdu, Adrian; Trusca, Roxana; Rădulescu, Radu; Chifiriuc, Mariana Carmen; Stan, Miruna S.; Constanda, Sabrina; Dinischiotu, Anca

2016-06-01

In this study we aimed to obtain functionalized thin films based on hydroxyapatite/poly(lactic-co-glycolic acid) (HAp/PLGA) containing ceftriaxone/cefuroxime antibiotics (ATBs) deposited by Matrix Assisted Pulsed Laser Evaporation (MAPLE) technique. The prepared thin films were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-Ray diffraction (XRD), selected area electron diffraction (SAED), and infra red (IR) analysis. HAp/PLGA/ATBs thin films sustained the growth of human osteoblasts, proving their good biocompatibility. The microscopic evaluation and the culture-based quantitative assay of the E. coli biofilm development showed that the thin films inhibited the initial step of microbial attachment as well as the subsequent colonization and biofilm development on the respective surfaces. This study demonstrates that MAPLE technique could represent an appealing technique for the fabrication of antibiotics-containing polymeric implant coatings. The bioevaluation results recommend this type of surfaces for the prevention of bone implant microbial contamination and for the enhanced stimulation of the implant osseointegration process.

Electronically decoupled stacking fault tetrahedra embedded in Au(111) films

PubMed Central

Schouteden, Koen; Amin-Ahmadi, Behnam; Li, Zhe; Muzychenko, Dmitry; Schryvers, Dominique; Van Haesendonck, Chris

2016-01-01

Stacking faults are known as defective structures in crystalline materials that typically lower the structural quality of the material. Here, we show that a particular type of defect, that is, stacking fault tetrahedra (SFTs), exhibits pronounced quantized electronic behaviour, revealing a potential synthetic route to decoupled nanoparticles in metal films. We report on the electronic properties of SFTs that exist in Au(111) films, as evidenced by scanning tunnelling microscopy and confirmed by transmission electron microscopy. We find that the SFTs reveal a remarkable decoupling from their metal surroundings, leading to pronounced energy level quantization effects within the SFTs. The electronic behaviour of the SFTs can be described well by the particle-in-a-box model. Our findings demonstrate that controlled preparation of SFTs may offer an alternative way to achieve well-decoupled nanoparticles of high crystalline quality in metal thin films without the need of thin insulating layers. PMID:28008910

Electronically decoupled stacking fault tetrahedra embedded in Au(111) films.

PubMed

Schouteden, Koen; Amin-Ahmadi, Behnam; Li, Zhe; Muzychenko, Dmitry; Schryvers, Dominique; Van Haesendonck, Chris

2016-12-23

Stacking faults are known as defective structures in crystalline materials that typically lower the structural quality of the material. Here, we show that a particular type of defect, that is, stacking fault tetrahedra (SFTs), exhibits pronounced quantized electronic behaviour, revealing a potential synthetic route to decoupled nanoparticles in metal films. We report on the electronic properties of SFTs that exist in Au(111) films, as evidenced by scanning tunnelling microscopy and confirmed by transmission electron microscopy. We find that the SFTs reveal a remarkable decoupling from their metal surroundings, leading to pronounced energy level quantization effects within the SFTs. The electronic behaviour of the SFTs can be described well by the particle-in-a-box model. Our findings demonstrate that controlled preparation of SFTs may offer an alternative way to achieve well-decoupled nanoparticles of high crystalline quality in metal thin films without the need of thin insulating layers.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cullen, David A; Koestner, Roland; Kukreja, Ratan

Improved conditions for imaging and spectroscopic mapping of thin perfluorosulfonic acid (PFSA) ionomer layers in fuel cell electrodes by scanning transmission electron microscopy (STEM) have been investigated. These conditions are first identified on model systems of Nafion ionomer-coated nanostructured thin films and nanoporous Si. The optimized conditions are then applied in a quantitative study of the ionomer through-layer loading for two typical electrode catalyst coatings using electron energy loss and energy dispersive X-ray spectroscopy in the transmission electron microscope. The e-beam induced damage to the perfluorosulfonic acid (PFSA) ionomer is quantified by following the fluorine mass loss with electron exposuremore » and is then mitigated by a few orders of magnitude using cryogenic specimen cooling and a higher incident electron voltage. Multivariate statistical analysis is also applied to the analysis of spectrum images for data denoising and unbiased separation of independent components related to the catalyst, ionomer, and support.« less

Correlative fluorescence and scanning transmission electron microscopy of quantum dot-labeled proteins on whole cells in liquid.

PubMed

Peckys, Diana B; Bandmann, Vera; de Jonge, Niels

2014-01-01

Correlative fluorescence microscopy combined with scanning transmission electron microscopy (STEM) of cells fully immersed in liquid is a new methodology with many application areas. Proteins, in live cells immobilized on microchips, are labeled with fluorescent quantum dot nanoparticles. In this protocol, the epidermal growth factor receptor (EGFR) is labeled. The cells are fixed after a selected labeling time, for example, 5 min as needed to form EGFR dimers. The microchip with cells is then imaged with fluorescence microscopy. Thereafter, STEM can be accomplished in two ways. The microchip with the labeled cells and one microchip with a spacer are assembled into a special microfluidic device and imaged with dedicated high-voltage STEM. Alternatively, thin edges of cells can be studied with environmental scanning electron microscopy with a STEM detector, by placing a microchip with cells in a cooled wet environment. © 2014 Elsevier Inc. All rights reserved.

Probing battery chemistry with liquid cell electron energy loss spectroscopy

DOE PAGES

Unocic, Raymond R.; Baggetto, Loic; Veith, Gabriel M.; ...

2015-09-15

Electron energy loss spectroscopy (EELS) was used to determine the chemistry and oxidation state of LiMn 2O 4 and Li 4Ti 5O 12 thin film battery electrodes in liquid cells for in situ scanning/transmission electron microscopy (S/TEM). Using the L2,3 white line intensity ratio method we determine the oxidation state of Mn and Ti in a liquid electrolyte solvent and discuss experimental parameters that influence measurement sensitivity.

Damage evaluation of proton irradiated titanium deuteride thin films to be used as neutron production targets

NASA Astrophysics Data System (ADS)

Suarez Anzorena, Manuel; Bertolo, Alma A.; Gagetti, Leonardo; Gaviola, Pedro A.; del Grosso, Mariela F.; Kreiner, Andrés J.

2018-06-01

Titanium deuteride thin films have been manufactured under different conditions specified by deuterium gas pressure, substrate temperature and time. The films were characterized by different techniques to evaluate the deuterium content and the homogeneity of such films. Samples with different concentrations of deuterium, including non deuterated samples, were irradiated with a 150 keV proton beam. Both deposits, pristine and irradiated, were characterized by optical profilometry and scanning electron microscopy.

Surface structures of L10-MnGa (001) by scanning tunneling microscopy and first-principles theory

NASA Astrophysics Data System (ADS)

Corbett, J. P.; Guerrero-Sanchez, J.; Richard, A. L.; Ingram, D. C.; Takeuchi, N.; Smith, A. R.

2017-11-01

We report on the surface reconstructions of L10-ordered MnGa (001) thin films grown by molecular beam epitaxy on a 50 nm Mn3N2 (001) layer freshly grown on a magnesium oxide (001) substrate. Scanning tunneling microscopy, Auger electron spectroscopy, and reflection high energy electron diffraction are combined with first-principles density functional theory calculations to determine the reconstructions of the L10-ordered MnGa (001) surface. We find two lowest energy reconstructions of the MnGa (001) face: a 1 × 1 Ga-terminated structure and a 1 × 2 structure with a Mn replacing a Ga in the 1 × 1 Ga-terminated surface. The 1 × 2 reconstruction forms a row structure along [100]. The manganese:gallium stoichiometry within the surface based on theoretical modeling is in good agreement with experiment. Magnetic moment calculations for the two lowest energy structures reveal important surface and bulk effects leading to oscillatory total magnetization for ultra-thin MnGa (001) films.

Ultraviolet emission enhancement in ZnO thin films modified by nanocrystalline TiO2

NASA Astrophysics Data System (ADS)

Zheng, Gaige; Lu, Xi; Qian, Liming; Xian, Fenglin

2017-05-01

In this study, nanocrystalline TiO2 modified ZnO thin films were prepared by electron beam evaporation. The structural, morphological and optical properties of the samples were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), UV-visible spectroscopy, fluorescence spectroscopy, respectively. The composition of the films was examined by energy dispersive X-ray spectroscopy (EDX). The photoluminescent spectrum shows that the pure ZnO thin film exhibits an ultraviolet (UV) emission peak and a strong green emission band. Surface analysis indicates that the ZnO thin film contains many oxygen vacancy defects on the surface. After the ZnO thin film is modified by the nanocrystalline TiO2 layer, the UV emission of ZnO is largely enhanced and the green emission is greatly suppressed, which suggests that the surface defects such as oxygen vacancies are passivated by the TiO2 capping layer. As for the UV emission enhancement of the ZnO thin film, the optimized thickness of the TiO2 capping layer is ∼16 nm. When the thickness is larger than 16 nm, the UV emission of the ZnO thin film will decrease because the TiO2 capping layer absorbs most of the excitation energy. The UV emission enhancement in the nanocrystalline TiO2 modified ZnO thin film can be attributed to surface passivation and flat band effect.

The Effects of ph on Structural and Optical Characterization of Iron Oxide Thin Films

NASA Astrophysics Data System (ADS)

Tezel, Fatma Meydaneri; Özdemir, Osman; Kariper, I. Afşin

In this study, the iron oxide thin films have been produced by chemical bath deposition (CBD) method as a function of pH onto amorphous glass substrates. The surface images of the films were investigated with scanning electron microscope (SEM). The crystal structures, orientation of crystallization, crystallite sizes, and dislocation density i.e. structural properties of the thin films were analyzed with X-ray diffraction (XRD). The optical band gap (Eg), optical transmission (T%), reflectivity (R%), absorption coefficient (α), refraction index (n), extinction coefficient (k) and dielectric constant (ɛ) of the thin films were investigated depending on pH, deposition time, solution temperature, substrate temperature, thickness of the films by UV-VIS spectrometer.

Characterization of barium strontium titanate thin films on sapphire substrate prepared via RF magnetron sputtering system

NASA Astrophysics Data System (ADS)

Jamaluddin, F. W.; Khalid, M. F. Abdul; Mamat, M. H.; Zoolfakar, A. S.; Zulkefle, M. A.; Rusop, M.; Awang, Z.

2018-05-01

Barium Strontium Titanate (Ba0.5Sr0.5TiO3) is known to have a high dielectric constant and low loss at microwave frequencies. These unique features are useful for many electronic applications. This paper focuses on material characterization of BST thin films deposited on sapphire substrate by RF magnetron sputtering system. The sample was then annealed at 900 °C for two hours. Several methods were used to characterize the structural properties of the material such as X-ray diffraction (XRD) and atomic force microscopy (AFM). Field emission scanning electron microscopy (FESEM) was used to analyze the surface morphology of the thin film. From the results obtained, it can be shown that the annealed sample had a rougher surface and better crystallinity as compared to as-deposited sample.

Atomic-resolution characterization of the effects of CdCl2 treatment on poly-crystalline CdTe thin films

NASA Astrophysics Data System (ADS)

Paulauskas, T.; Buurma, C.; Colegrove, E.; Guo, Z.; Sivananthan, S.; Chan, M. K. Y.; Klie, R. F.

2014-08-01

Poly-crystalline CdTe thin films on glass are used in commercial solar-cell superstrate devices. It is well known that post-deposition annealing of the CdTe thin films in a CdCl2 environment significantly increases the device performance, but a fundamental understanding of the effects of such annealing has not been achieved. In this Letter, we report a change in the stoichiometry across twin boundaries in CdTe and propose that native point defects alone cannot account for this variation. Upon annealing in CdCl2, we find that the stoichiometry is restored. Our experimental measurements using atomic-resolution high-angle annular dark field imaging, electron energy-loss spectroscopy, and energy dispersive X-ray spectroscopy in a scanning transmission electron microscope are supported by first-principles density functional theory calculations.

Optical characteristics of bismuth sulfide (Bi2S3) thin films.

NASA Astrophysics Data System (ADS)

Mahmoud, S.; Eid, A. H.; Omar, H.

Thin films of bismuth sulfide (Bi2S3) were grown by two deposition techniques, by thermal evaporation and by chemical deposition. The thermally deposited reactions consisted in depositing the individual elements, namely bismuth and sulfur, sequentially from a tungsten boat source and allowing the layers to interdiffuse to form the compound during the heat-treatment. The chemical deposition was based on the reaction between the triethanolamine compex of Bi3+ ions and thiourea in basic media. Scanning electron microscope and X-ray diffraction analysis were made on as-deposited and on annealed films to determine their structure. The different electronic transitions and the optical constants are determined from the transmision and reflection data of these thin films for normal incidence. The optical gaps of Bi2S3 films show a remarkable dependence on the preparation method.

A simple and low temperature process for super-hydrophilic rutile TiO 2 thin films growth

NASA Astrophysics Data System (ADS)

Mane, R. S.; Joo, Oh-Shim; Min, Sun-Ki; Lokhande, C. D.; Han, Sung-Hwan

2006-11-01

We investigate an environmentally friendly aqueous solution system for rutile TiO2 violet color nanocrystalline thin films growth on ITO substrate at room temperature. Film shows considerable absorption in visible region with excitonic maxima at 434 nm. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), selected area electron diffraction (SAED), UV-vis, water surface contact angle and energy dispersive X-ray analysis (EDX) techniques in addition to actual photo-image that shows purely rutile phase of TiO2 with violet color, super-hydrophilic and densely packed nanometer-sized spherical grains of approximate diameter 3.15 ± 0.4 nm, characterize the films. Band gap energy of 4.61 eV for direct transition was obtained for the rutile TiO2 films. Film surface shows super-hydrophilic behavior, as exhibited water contact angle was 7°. Strong visible absorption (not due to chlorine) leaves future challenge to use these films in extremely thin absorber (ETA) solar cells.

Correlation study of nanocrystalline carbon doped thin films prepared by a thermionic vacuum arc deposition technique

NASA Astrophysics Data System (ADS)

Dinca-Balan, Virginia; Vladoiu, Rodica; Mandes, Aurelia; Prodan, Gabriel

2017-11-01

The synthesis of Ag, Mg and Si nanocrystalline, embedded in a hydrogen-free amorphous carbon (a-C) matrix, deposited by a high vacuum and free buffer gas technique, were investigated. The films with compact structures and extremely smooth surfaces were prepared using the thermionic vacuum arc method in one electron gun configuration, on glass and silicon substrates. The surface morphology and wettability of the obtained multifunctional thin films were investigated using transmission electron microscopy (TEM), scanning electron microscopy (SEM) and free surface energy (FSE) by See System. The results from the TEM measurements show how the Ag, Mg and Si interacted with carbon and the influence these materials have on the thin film structure formation and the grain size distribution. SEM correlated with EDX results reveal a very precise comparative study, regarding the quantity of the elements that morphed into carbides nanostructures. Also, the FSE results prove how different materials in combination with carbon can make changes to the surface properties.

Effect of Substrate Roughness on Adhesion and Structural Properties of Ti-Ni Shape Memory Alloy Thin Film.

PubMed

Kim, Donghwan; Lee, Hyunsuk; Bae, Joohyeon; Jeong, Hyomin; Choi, Byeongkeun; Nam, Taehyun; Noh, Jungpil

2018-09-01

Ti-Ni shape memory alloy (SMA) thin films are very attractive material for industrial and medical applications such as micro-actuator, micro-sensors, and stents for blood vessels. An important property besides shape memory effect in the application of SMA thin films is the adhesion between the film and the substrate. When using thin films as micro-actuators or micro-sensors in MEMS, the film must be strongly adhered to the substrate. On the other hand, when using SMA thin films in medical devices such as stents, the deposited alloy thin film must be easily separable from the substrate for efficient processing. In this study, we investigated the effect of substrate roughness on the adhesion of Ti-Ni SMA thin films, as well as the structural properties and phase-transformation behavior of the fabricated films. Ti-Ni SMA thin films were deposited onto etched glass substrates with magnetron sputtering. Radio frequency plasma was used for etching the substrate. The adhesion properties were investigated through progressive scratch test. Structural properties of the films were determined via Feld emission scanning electron microscopy, X-ray diffraction measurements (XRD) and Energy-dispersive X-ray spectroscopy analysis. Phase transformation behaviors were observed with differential scanning calorimetry and low temperature-XRD. Ti-Ni SMA thin film deposited onto rough substrate provides higher adhesive strength than smooth substrate. However the roughness of the substrate has no influence on the growth and crystallization of the Ti-Ni SMA thin films.

Synthesis of zirconia (ZrO2) nanowires via chemical vapor deposition

NASA Astrophysics Data System (ADS)

Baek, M. K.; Park, S. J.; Choi, D. J.

2017-02-01

Monoclinic zirconia nanowires were synthesized by chemical vapor deposition using ZrCl4 powder as a starting material at 1200 °C and 760 Torr. Graphite was employed as a substrate, and an Au thin film was pre-deposited on the graphite as a catalyst. The zirconia nanostructure morphology was observed through scanning electron microscopy and transmission electron microscopy. Based on X-ray diffraction, selected area electron diffraction, and Raman spectroscopy data, the resulting crystal structure was found to be single crystalline monoclinic zirconia. The homogeneous distributions of Zr, O and Au were studied by scanning transmission electron microscopy with energy dispersive X-ray spectroscopy mapping, and there was no metal droplet at the nanowire tips despite the use of an Au metal catalyst. This result is apart from that of conventional metal catalyzed nanowires.

Nanoscale contact resistance of V2O5 xerogel films developed by nanostructured powder

NASA Astrophysics Data System (ADS)

Bera, Biswajit; Sekhar Das, Pradip; Bhattacharya, Manjima; Ghosh, Swapankumar; Mukhopadhyay, Anoop Kumar; Dey, Arjun

2016-03-01

Here we report the synthesis of V2O5 nanostructures by a fast, simple, cost-effective, low-temperature chemical process; followed by the deposition of V2O5 xerogel thin films on a glass substrate by a sol-gel route. Phase analysis, phase transition, microstructural and electronic characterization studies are carried out by x-ray diffraction, texture coefficient analysis, field emission scanning electron microscopy, transmission electron microscopy (TEM), related selected area electron diffraction pattern (SAED) analysis, Fourier transform infrared spectroscopy, thermogravimetry and differential thermal analysis, differential scanning calorimetry, and x-ray photoelectron spectroscopy techniques. Confirmatory TEM and SAED data analysis prove further that in this polycrystalline powder there is a unique localized existence of purely single crystalline V2O5 powder with a preferred orientation in the (0 1 0) direction. The most interesting result obtained in the present work is that the xerogel thin films exhibit an inherent capability to enhance the intrinsic resistance against contact induced deformations as more external load is applied during the nanoindentation experiments. In addition, both the nanohardness and Young’s modulus of the films are found to be insensitive to load variations (e.g. 1 to 7 mN). These results are explained in terms of microstructural parameters, e.g. porosity and structural configuration.

Laser sintered thin layer graphene and cubic boron nitride reinforced nickel matrix nanocomposites

NASA Astrophysics Data System (ADS)

Hu, Zengrong; Tong, Guoquan

2015-10-01

Laser sintered thin layer graphene (Gr)-cubic boron nitride (CBN)-Ni nanocomposites were fabricated on AISI 4140 plate substrate. The composites fabricating process, composites microstructure and mechanical properties were studied. Scanning electron microscopy (SEM), X-ray diffraction (XRD) and Raman spectroscopy were employed to study the micro structures and composition of the composites. XRD and Raman tests proved that graphene and CBN were dispersed in the nanocomposites. Nanoindentation test results indicate the significant improvements were achieved in the composites mechanical properties.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, D.F.; Zhang, X.M.; Gautier, E.

The morphology and crystallography of deformation-induced martensites formed during isothermal tensile tests in Fe-30Ni-0.34C and Fe-25Ni-0.66C alloys were investigated by means of optical, transmission electron and scanning electron microscopy. Transitions in morphology from thin plate to coupled plate, to lenticular coupled-plate martensite and from thin plate to lenticular to compact martensite have been observed with increasing deformation. Stress favors the growth of martensite when concurrent plastic strain allows accommodation of macroscopic transformation strains and the change of the Bain strain accommodation mechanism. Mobile dislocations and emission dislocations are directly related to the change of the Bain strain accommodation mechanism frommore » twinning to slip.« less

Connected Au network in annealed Ni/Au thin films on p-GaN

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, S. P.; Jang, H. W.; Noh, D. Y.

2007-11-12

We report the formation of a connected Au network in annealed Ni/Au thin films on p-GaN, which was studied by scanning electron microscopy, transmission electron microscopy, and synchrotron x-ray diffraction. As the Ni was oxidized into NiO upon annealing at 530 deg. C in air, the Au layer was transformed to an interconnected network with an increased thickness. During annealing, Ni atoms diffuse out onto the Au through defects to form NiO, while Au atoms replace the Ni positions. The Au network grows downward until it reaches the p-GaN substrate, and NiO columns fill the space between the Au network.

Clean graphene electrodes on organic thin-film devices via orthogonal fluorinated chemistry.

PubMed

Beck, Jonathan H; Barton, Robert A; Cox, Marshall P; Alexandrou, Konstantinos; Petrone, Nicholas; Olivieri, Giorgia; Yang, Shyuan; Hone, James; Kymissis, Ioannis

2015-04-08

Graphene is a promising flexible, highly transparent, and elementally abundant electrode for organic electronics. Typical methods utilized to transfer large-area films of graphene synthesized by chemical vapor deposition on metal catalysts are not compatible with organic thin-films, limiting the integration of graphene into organic optoelectronic devices. This article describes a graphene transfer process onto chemically sensitive organic semiconductor thin-films. The process incorporates an elastomeric stamp with a fluorinated polymer release layer that can be removed, post-transfer, via a fluorinated solvent; neither fluorinated material adversely affects the organic semiconductor materials. We used Raman spectroscopy, atomic force microscopy, and scanning electron microscopy to show that chemical vapor deposition graphene can be successfully transferred without inducing defects in the graphene film. To demonstrate our transfer method's compatibility with organic semiconductors, we fabricate three classes of organic thin-film devices: graphene field effect transistors without additional cleaning processes, transparent organic light-emitting diodes, and transparent small-molecule organic photovoltaic devices. These experiments demonstrate the potential of hybrid graphene/organic devices in which graphene is deposited directly onto underlying organic thin-film structures.

Auger electron diffraction in thin CoO films on Au(1 1 1)

NASA Astrophysics Data System (ADS)

Chassé, A.; Niebergall, L.; Heiler, M.; Neddermeyer, H.; Schindler, K.-M.

The local structure of thin CoO films grown on a single crystal Au(1 1 1) surface has been studied by Auger electron diffraction (AED). Therefore, the angular dependence of the Auger electron intensity of Co-LMM and O-KLL Auger electrons was recorded in the total half-space above the film. Such 2 π-scans immediately reflect the symmetry of the surface and the local structure of the film. The experimental data are compared to multiple-scattering cluster calculations, where both the influence of multiple-scattering effects and effects of Auger transition matrix elements have been investigated. We have found that the AED patterns of a CoO film in forward-scattering conditions do not always provide straightforward information on the local structure of the film, whereas the multiple-scattering approximation applied gives very good agreement between experimental and theoretical results.

Quantifying charge carrier concentration in ZnO thin films by Scanning Kelvin Probe Microscopy

PubMed Central

Maragliano, C.; Lilliu, S.; Dahlem, M. S.; Chiesa, M.; Souier, T.; Stefancich, M.

2014-01-01

In the last years there has been a renewed interest for zinc oxide semiconductor, mainly triggered by its prospects in optoelectronic applications. In particular, zinc oxide thin films are being widely used for photovoltaic applications, in which the determination of the electrical conductivity is of great importance. Being an intrinsically doped material, the quantification of its doping concentration has always been challenging. Here we show how to probe the charge carrier density of zinc oxide thin films by Scanning Kelvin Probe Microscopy, a technique that allows measuring the contact potential difference between the tip and the sample surface with high spatial resolution. A simple electronic energy model is used for correlating the contact potential difference with the doping concentration in the material. Limitations of this technique are discussed in details and some experimental solutions are proposed. Two-dimensional doping concentration images acquired on radio frequency-sputtered intrinsic zinc oxide thin films with different thickness and deposited under different conditions are reported. We show that results inferred with this technique are in accordance with carrier concentration expected for zinc oxide thin films deposited under different conditions and obtained from resistivity and mobility measurements. PMID:24569599

Improvement of corrosion resistance of NiTi sputtered thin films by anodization

NASA Astrophysics Data System (ADS)

Bayat, N.; Sanjabi, S.; Barber, Z. H.

2011-08-01

Anodization of sputtered NiTi thin films has been studied in 1 M acetic acid at 23 °C for different voltages from 2 to 10 V. The morphology and cross-sectional structures of the untreated and anodized surfaces were investigated by field emission scanning electron microscopy (FE-SEM). The results show that increasing anodization voltage leads to film surface roughening and unevenness. It can be seen that the thickness of the anodized layer formed on the NiTi surface is in the nanometer range. The corrosion resistance of anodized thin films was studied by potentiodynamic scan (PDS) and impedance spectroscopy (EIS) techniques in Hank's solution at 310 K (37 °C). It was shown that the corrosion resistance of the anodized film surface improved with increasing voltage to 6 V. Anodization of austenitic sputtered NiTi thin films has also been studied, in the same anodizing conditions, at 4 V. Comparison of anodized sputtered NiTi thin films with anodized austenitic shape memory films illustrate that the former are more corrosion resistant than the latter after 1 h immersion in Hank's solution, which is attributed to the higher grain boundary density to quickly form a stable and protective passive film.

Preparation of isolated nuclei from K 562 haemopoietic cell line for high resolution scanning electron microscopy.

PubMed

Reipert, S; Reipert, B M; Allen, T D

1994-09-01

The aim of the work is to visualise nuclear pore complexes (NPCs) in mammalian cells by high resolution scanning electron microscopy. A detergent-free isolation protocol was employed to obtain clean nuclei from the haemopoietic cell line K 562. Nuclear isolation was performed by mechanical homogenisation under hypotonic conditions followed by purification of the nuclear fraction. The isolated nuclei were attached to silicon chips, fixed, critical point dried, and sputter coated with a thin film (3-4 nm) of tantalum. Analysis of the nuclear surface by scanning electron microscopy (SEM) revealed a strong sensitivity of the outer nuclear membrane (ONM) to disruption during the isolation procedure. A significant reduction of the characteristic pattern of damage to the ONM was achieved by means of an isopicnic centrifugation on an isoosmolar balanced Percoll gradient. Analysis of the population of isolated nuclei by flow cytometry showed no signs of cell cycle specific losses of nuclei during isolation. The SEM investigations of the morphology of the nuclear envelope (NE) and of substructural details of NPCs and polyribosomes were performed using an in-lens field emission scanning electron microscope.

Antimicrobial activity of biopolymer-antibiotic thin films fabricated by advanced pulsed laser methods

NASA Astrophysics Data System (ADS)

Cristescu, R.; Popescu, C.; Dorcioman, G.; Miroiu, F. M.; Socol, G.; Mihailescu, I. N.; Gittard, S. D.; Miller, P. R.; Narayan, R. J.; Enculescu, M.; Chrisey, D. B.

2013-08-01

We report on thin film deposition by matrix assisted pulsed laser evaporation (MAPLE) of two polymer-drug composite thin film systems. A pulsed KrF* excimer laser source (λ = 248 nm, τ = 25 ns, ν = 10 Hz) was used to deposit composite thin films of poly(D,L-lactide) (PDLLA) containing several gentamicin concentrations. FTIR spectroscopy was used to demonstrate that MAPLE-transferred materials exhibited chemical structures similar to those of drop cast materials. Scanning electron microscopy data indicated that MAPLE may be used to fabricate thin films of good morphological quality. The activity of PDLLA-gentamicin composite thin films against Staphylococcus aureus bacteria was demonstrated using drop testing. The influence of drug concentration on microbial viability was also assessed. Our studies indicate that polymer-drug composite thin films prepared by MAPLE may be used to impart antimicrobial activity to implants, medical devices, and other contact surfaces.

Deposition and characterization of ZnSe nanocrystalline thin films

NASA Astrophysics Data System (ADS)

Temel, Sinan; Gökmen, F. Özge; Yaman, Elif; Nebi, Murat

2018-02-01

ZnSe nanocrystalline thin films were deposited at different deposition times by using the Chemical Bath Deposition (CBD) technique. Effects of deposition time on structural, morphological and optical properties of the obtained thin films were characterized. X-ray diffraction (XRD) analysis was used to study the structural properties of ZnSe nanocrystalline thin films. It was found that ZnSe thin films have a cubic structure with a preferentially orientation of (111). The calculated average grain size value was about 28-30 nm. The surface morphology of these films was studied by the Field Emission Scanning Electron Microscope (FESEM). The surfaces of the thin films were occurred from small stacks and nano-sized particles. The band gap values of the ZnSe nanocrystalline thin films were determined by UV-Visible absorption spectrum and the band gap values were found to be between 2.65-2.86 eV.

Characterization of Pb-Doped GaN Thin Films Grown by Thermionic Vacuum Arc

NASA Astrophysics Data System (ADS)

Özen, Soner; Pat, Suat; Korkmaz, Şadan

2018-03-01

Undoped and lead (Pb)-doped gallium nitride (GaN) thin films have been deposited by a thermionic vacuum arc (TVA) method. Glass and polyethylene terephthalate were selected as optically transparent substrates. The structural, optical, morphological, and electrical properties of the deposited thin films were investigated. These physical properties were interpreted by comparison with related analysis methods. The crystalline structure of the deposited GaN thin films was hexagonal wurtzite. The optical bandgap energy of the GaN and Pb-doped GaN thin films was found to be 3.45 eV and 3.47 eV, respectively. The surface properties of the deposited thin films were imaged using atomic force microscopy and field-emission scanning electron microscopy, revealing a nanostructured, homogeneous, and granular surface structure. These results confirm that the TVA method is an alternative layer deposition system for Pb-doped GaN thin films.

Deposition of tetracene thin films on SiO2/Si substrates by rapid expansion of supercritical solutions using carbon dioxide

NASA Astrophysics Data System (ADS)

Fujii, Tatsuya; Takahashi, Yuta; Uchida, Hirohisa

2015-03-01

We report on a novel deposition technique of tetracene (naphthacene) thin films on SiO2/Si substrates by rapid expansion of supercritical solutions (RESS) using CO2. Optical microscopy and scanning electron microscopy show that the thin films consist of a high density of submicron-sized grains. The growth mode of the grains followed the Volmer-Weber mode. X-ray diffraction shows that the thin films have regularly arranged structures in both the horizontal and vertical directions of the substrate. A fabricated top-contacted organic thin-film transistor with the tetracene active layer showed p-type transistor characteristics with a field-effect mobility of 5.1 × 10-4 cm2 V-1 s-1.

Microstructure engineering of Pt-Al alloy thin films through Monte Carlo simulations

NASA Astrophysics Data System (ADS)

Harris, R. A.; Terblans, J. J.; Swart, H. C.

2014-06-01

A kinetic algorithm, based on the regular solution model, was used in conjunction with the Monte Carlo method to simulate the evolution of a micro-scaled thin film system during exposure to a high temperature environment. Pt-Al thin films were prepared via electron beam physical vapor deposition (EB-PVD) with an atomic concentration ratio of Pt63:Al37. These films were heat treated at an annealing temperature of 400 °C for 16 and 49 minutes. Scanning Auger Microscopy (SAM) (PHI 700) was used to obtain elemental maps while sputtering through the thin films. Simulations were run for the same annealing temperatures and thin-film composition. From these simulations theoretical depth profiles and simulated microstructures were obtained. These were compared to the experimentally measured depth profiles and elemental maps.

Electrochemical properties of magnetron sputtered WO{sub 3} thin films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Madhavi, V.; Kondaiah, P.; Hussain, O. M.

2013-02-05

Thin films of tungsten oxide (WO{sub 3}) were deposited on ITO substrates by using RF magnetron sputtering at oxygen and argon atmospheres of 6 Multiplication-Sign 10{sup -2}Pa and 4 Pa respectively. The chemical composition and surface morphology of the WO{sub 3} thin films have been studied by X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) respectively. The results indicate that the deposited WO{sub 3} thin films are nearly stoichiometric. The electrochemical performances of the WO{sub 3} thin films have been evaluated by galvonostatic charging/discharging method. The discharge capacity was 15{mu}Ah/cm{sup 2}{mu}m at the initial cycle and faded rapidly inmore » the first few cycles and stabilized at a lesser stage.« less

Chemically prepared La2Se3 nanocubes thin film for supercapacitor application.

PubMed

Patil, S J; Lokhande, V C; Chodankar, N R; Lokhande, C D

2016-05-01

Lanthanum selenide (La2Se3) nanocubes thin film is prepared via successive ionic layer adsorption and reaction (SILAR) method and utilized for energy storage application. The prepared La2Se3 thin film is characterized by X-ray diffraction, field emission scanning electron microscopy and contact angle measurement techniques for structural, surface morphological and wettability studies, respectively. Energy dispersive X-ray microanalysis (EDAX) is performed in order to obtain the elemental composition of the thin film. The La2Se3 film electrode shows a maximum specific capacitance of 363 F g(-1) in a 0.8 M LiClO4/PC electrolyte at a scan rate of 5 mV s(-1) within 1.3 V/SCE potential range. The specific capacitive retention of 83 % of La2Se3 film electrode is obtained over 1000 cyclic voltammetry cycles. The predominant performance, such as high energy (80 Wh kg(-1)) and power density (2.5 kW kg(-1)), indicates that La2Se3 film electrode facilitates fast ion diffusion during redox processes. Copyright © 2016 Elsevier Inc. All rights reserved.

Initial formation of calcite crystals in the thin prismatic layer with the periostracum of Pinctada fucata.

PubMed

Suzuki, Michio; Nakayama, Seiji; Nagasawa, Hiromichi; Kogure, Toshihiro

2013-02-01

Although the formation mechanism of calcite crystals in the prismatic layer has been studied well in many previous works, the initial state of calcite formation has not been observed in detail using electron microscopes. In this study, we report that the soft prismatic layer with transparent color (the thin prismatic layer) in the tip of the fresh shell of Pinctada fucata was picked up to observe the early calcification phase. A scanning electron microscope (SEM) image showed that the growth tip of the thin prismatic layer was covered by the periostracum, which was also where the initial formation of calcite crystals began. A cross-section containing the thin calcite crystals in the thin prismatic layer with the periostracum was made using a focused ion beam (FIB) system. In a transmission electron microscope (TEM) observation, the thin calcite crystal (thickness is about 1μm) on the periostracum was found to be a single crystal with the c-axis oriented perpendicular to the shell surface. On the other hand, many aggregated small particles consisting of bassanite crystals were observed in the periostracum suggesting the possibility that not only organic sulfate but also inorganic sulfates exist in the prismatic layer. These discoveries in the early calcification phase of the thin prismatic layer may help to clarify the mechanism of regulating the nucleation and orientation of the calcite crystal in the shell. Copyright © 2012 Elsevier Ltd. All rights reserved.

Passive optical limiting studies of nanostructured Cu doped ZnO-PVA composite thin films

NASA Astrophysics Data System (ADS)

Tamgadge, Y. S.; Sunatkari, A. L.; Talwatkar, S. S.; Pahurkar, V. G.; Muley, G. G.

2016-01-01

We prepared undoped and Cu doped ZnO semiconducting nanoparticles (NPs) by chemical co-precipitation method and obtained Cu doped ZnO-polyvinyl alcohol (PVA) nanocomposite thin films by spin coating to investigate third order nonlinear optical and optical limiting properties under cw laser excitation. Powder samples of NPs were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), energy dispersive spectroscopy, transmission electron microscopy, ultraviolet-visible (UV-vis) and Fourier transform infrared spectroscopy. XRD pattern and FE-SEM micrograph revealed the presence of hexagonal wurtzite phase ZnO NPs having uniform morphology with average particle size of 20 nm. The presence of excitons and absorption peaks in the range 343-360 nm, revealed by UV-vis study, were attributed to excitons in n = 1 quantum state. Third order NLO properties of all composite thin films were investigated by He-Ne continuous wave (cw) laser of wavelength 632.8 nm using Z-scan technique. Thermally stimulated enhanced values of nonlinear refraction and absorption coefficients were obtained which may be attributed to self-defocusing effect, reverse saturable absorption, weak free carrier absorption and surface states properties originated from thermo optic effect. Optical limiting properties have been studied using cw diode laser of wavelength 808 nm and results are presented.

Gold coated metal nanostructures grown by glancing angle deposition and pulsed electroplating

NASA Astrophysics Data System (ADS)

Grüner, Christoph; Reeck, Pascal; Jacobs, Paul-Philipp; Liedtke, Susann; Lotnyk, Andriy; Rauschenbach, Bernd

2018-05-01

Nickel based nanostructures are grown by glancing angle deposition (GLAD) on flat and pre-patterned substrates. These fabricated porous thin films were subsequently coated by pulsed electroplating with gold. The morphology and conformity of the gold coating were investigated by scanning electron microscopy and X-ray diffraction. Controlled growth of closed gold layers on the nanostructures could be achieved, while the open-pore structure of the nanosculptured thin films was preserved. Such gold coated nanostructures are a candidate for optical sensing and catalysis applications. The demonstrated method can be applied for numerous material combinations, allowing to provide GLAD thin films with new surface properties.

Acquisition parameters optimization of a transmission electron forward scatter diffraction system in a cold-field emission scanning electron microscope for nanomaterials characterization.

PubMed

Brodusch, Nicolas; Demers, Hendrix; Trudeau, Michel; Gauvin, Raynald

2013-01-01

Transmission electron forward scatter diffraction (t-EFSD) is a new technique providing crystallographic information with high resolution on thin specimens by using a conventional electron backscatter diffraction (EBSD) system in a scanning electron microscope. In this study, the impact of tilt angle, working distance, and detector distance on the Kikuchi pattern quality were investigated in a cold-field emission scanning electron microscope (CFE-SEM). We demonstrated that t-EFSD is applicable for tilt angles ranging from -20° to -40°. Working distance (WD) should be optimized for each material by choosing the WD for which the EBSD camera screen illumination is the highest, as the number of detected electrons on the screen is directly dependent on the scattering angle. To take advantage of the best performances of the CFE-SEM, the EBSD camera should be close to the sample and oriented towards the bottom to increase forward scattered electron collection efficiency. However, specimen chamber cluttering and beam/mechanical drift are important limitations in the CFE-SEM used in this work. Finally, the importance of t-EFSD in materials science characterization was illustrated through three examples of phase identification and orientation mapping. © Wiley Periodicals, Inc.

Iron doped LiCoPO4 thin films for lithium-ion microbatteries obtained by ns pulsed laser deposition

NASA Astrophysics Data System (ADS)

Smaldone, A.; Brutti, S.; De Bonis, A.; Ciarfaglia, N.; Santagata, A.; Teghil, R.

2018-07-01

Well crystallized and homogeneous iron doped LiCoPO4 (LCfP) thin films have been grown by ns Pulsed Laser Ablation, at ambient temperature without any substrate heating or post-annealing treatments. The films have been deposited in vacuum and in the presence of buffer gases (O2, Ar) and it has been found that their crystallinity, structure and morphology depend on pressure conditions. The films have been studied by Scanning Electron Microscopy and X Ray Diffraction, while their first steps of growth have been characterized by Transmission Electron Microscopy. A study of the plasma produced by the laser ablation in the different pressure conditions has been carried out with the aim of elucidate the mechanisms involved in the films deposition. LCfP thin films have been also tested as microelectrodes in lithium cells in galvanostatic condition for analyzing the reversibility of the lithium-ion battery.

New modes of electron microscopy for materials science enabled by fast direct electron detectors

NASA Astrophysics Data System (ADS)

Minor, Andrew

There is an ongoing revolution in the development of electron detector technology that has enabled modes of electron microscopy imaging that had only before been theorized. The age of electron microscopy as a tool for imaging is quickly giving way to a new frontier of multidimensional datasets to be mined. These improvements in electron detection have enabled cryo-electron microscopy to resolve the three-dimensional structures of non-crystalized proteins, revolutionizing structural biology. In the physical sciences direct electron detectors has enabled four-dimensional reciprocal space maps of materials at atomic resolution, providing all the structural information about nanoscale materials in one experiment. This talk will highlight the impact of direct electron detectors for materials science, including a new method of scanning nanobeam diffraction. With faster detectors we can take a series of 2D diffraction patterns at each position in a 2D STEM raster scan resulting in a four-dimensional data set. For thin film analysis, direct electron detectors hold the potential to enable strain, polarization, composition and electrical field mapping over relatively large fields of view, all from a single experiment.

Nanometres-resolution Kikuchi patterns from materials science specimens with transmission electron forward scatter diffraction in the scanning electron microscope.

PubMed

Brodusch, N; Demers, H; Gauvin, R

2013-04-01

A charge-coupled device camera of an electron backscattered diffraction system in a scanning electron microscope was positioned below a thin specimen and transmission Kikuchi patterns were collected. Contrary to electron backscattered diffraction, transmission electron forward scatter diffraction provides phase identification and orientation mapping at the nanoscale. The minimum Pd particle size for which a Kikuchi diffraction pattern was detected and indexed reliably was 5.6 nm. An orientation mapping resolution of 5 nm was measured at 30 kV. The resolution obtained with transmission electron forward scatter diffraction was of the same order of magnitude than that reported in electron nanodiffraction in the transmission electron microscope. An energy dispersive spectrometer X-ray map and a transmission electron forward scatter diffraction orientation map were acquired simultaneously. The high-resolution chemical, phase and orientation maps provided at once information on the chemical form, orientation and coherency of precipitates in an aluminium-lithium 2099 alloy. © 2013 The Authors Journal of Microscopy © 2013 Royal Microscopical Society.

Dip coated TiO2 nanostructured thin film: synthesis and application

NASA Astrophysics Data System (ADS)

Vanaraja, Manoj; Muthukrishnan, Karthika; Boomadevi, Shanmugam; Karn, Rakesh Kumar; Singh, Vijay; Singh, Pramod K.; Pandiyan, Krishnamoorthy

2016-02-01

TiO2 thin film was fabricated by dip coating method using titanium IV chloride as precursor and sodium carboxymethyl cellulose as thickening as well as capping agent. Structural and morphological features of TiO2 thin film were characterized by X-ray diffractometer and field emission scanning electron microscope, respectively. Crystallinity of the film was confirmed with high-intensity peak at (101) plane, and its average crystallite size was found to be 28 nm. The ethanol-sensing properties of TiO2 thin film was studied by the chemiresistive method. Furthermore, various gases were tested in order to verify the selectivity of the sensor. Among the several gases, the fabricated TiO2 sensor showed very high selectivity towards ethanol at room temperature.

Physical properties of nanostructured strontium oxide thin film grown by chemical bath deposition technique

NASA Astrophysics Data System (ADS)

Ahmad, Farhan; Belkhedkar, M. R.; Salodkar, R. V.

2018-05-01

Nanostructured SrO thin film of thickness 139 nm was deposited by chemical bath deposition technique onto glass substrates using SrCl2.6H2O and NaOH as cationic and anionic precursors without complexing agents. The X-ray diffraction studies revealed that, SrO thin film is nanocrystalline in nature with cubic structure. The surface morphology of the SrO film was investigated by means of field emission scanning electron microscopy. The optical studies showed that SrO film exhibits direct as well as indirect optical band gap energy. The electrical resistivity and activation energy of SrO thin film is found to be of the order of 106 Ω cm and 0.58eV respectively.

From Single Atoms to Nanoparticles — Spectroscopy on the Atomic Level

NASA Astrophysics Data System (ADS)

Nilius, Niklas

2003-12-01

The scanning tunneling microscope is not only a well-established tool for a topographic characterization of the sample surface on the atomic scale. It also provides a variety of spectroscopic techniques to examine electronic, magnetic, vibrational and optical properties of a localized system. The following presentation gives an overview, how scanning tunneling spectroscopy, inelastic electron tunneling spectroscopy and photon emission spectroscopy with the STM can be employed to investigate spatially confined metal systems and their interaction with molecular gases. The experiments were performed on single Pd and Au atoms, mono-atomic chains and individual Ag clusters on a NiAl support and a Al2O3 thin film.

Phase contrast scanning transmission electron microscopy imaging of light and heavy atoms at the limit of contrast and resolution.

PubMed

Yücelen, Emrah; Lazić, Ivan; Bosch, Eric G T

2018-02-08

Using state of the art scanning transmission electron microscopy (STEM) it is nowadays possible to directly image single atomic columns at sub-Å resolution. In standard (high angle) annular dark field STEM ((HA)ADF-STEM), however, light elements are usually invisible when imaged together with heavier elements in one image. Here we demonstrate the capability of the recently introduced Integrated Differential Phase Contrast STEM (iDPC-STEM) technique to image both light and heavy atoms in a thin sample at sub-Å resolution. We use the technique to resolve both the Gallium and Nitrogen dumbbells in a GaN crystal in [[Formula: see text

Matched Backprojection Operator for Combined Scanning Transmission Electron Microscopy Tilt- and Focal Series.

PubMed

Dahmen, Tim; Kohr, Holger; de Jonge, Niels; Slusallek, Philipp

2015-06-01

Combined tilt- and focal series scanning transmission electron microscopy is a recently developed method to obtain nanoscale three-dimensional (3D) information of thin specimens. In this study, we formulate the forward projection in this acquisition scheme as a linear operator and prove that it is a generalization of the Ray transform for parallel illumination. We analytically derive the corresponding backprojection operator as the adjoint of the forward projection. We further demonstrate that the matched backprojection operator drastically improves the convergence rate of iterative 3D reconstruction compared to the case where a backprojection based on heuristic weighting is used. In addition, we show that the 3D reconstruction is of better quality.

Comparison of the agglomeration behavior of thin metallic films on SiO2

NASA Astrophysics Data System (ADS)

Gadkari, P. R.; Warren, A. P.; Todi, R. M.; Petrova, R. V.; Coffey, K. R.

2005-07-01

The stability of continuous metallic thin films on insulating oxide surfaces is of interest to applications such as semiconductor interconnections and gate engineering. In this work, we report the study of the formation of voids and agglomeration of initially continuous Cu, Au, Ru and Pt thin films deposited on amorphous thermally grown SiO2 surfaces. Polycrystalline thin films having thicknesses in the range of 10-100 nm were ultrahigh vacuum sputter deposited on thermally grown SiO2 surfaces. The films were annealed at temperatures in the range of 150-800 °C in argon and argon+3% hydrogen gases. Scanning electron microscopy was used to investigate the agglomeration behavior, and transmission electron microscopy was used to characterize the microstructure of the as-deposited and annealed films. The agglomeration sequence in all of the films is found to follow a two step process of void nucleation and void growth. However, void growth in Au and Pt thin films is different from Cu and Ru thin films. Residual stress and adhesion were observed to play an important part in deciding the mode of void growth in Au and Pt thin films. Last, it is also observed that the tendency for agglomeration can be reduced by encapsulating the metal film with an oxide overlayer.

Application of low-energy scanning transmission electron microscopy for the study of Pt-nanoparticle uptake in human colon carcinoma cells.

PubMed

Blank, Holger; Schneider, Reinhard; Gerthsen, Dagmar; Gehrke, Helge; Jarolim, Katharina; Marko, Doris

2014-06-01

High-angle annular dark-field scanning transmission electron microscopy (HAADF STEM) in a scanning electron microscope facilitates the acquisition of images with high chemical sensitivity and high resolution. HAADF STEM at low electron energies is particularly suited to image nanoparticles (NPs) in thin cell sections which are not subjected to poststaining procedures as demonstrated by comparison with bright-field TEM. High membrane contrast is achieved and distinction of NPs with different chemical composition is possible at first sight. Low-energy HAADF STEM was applied to systematically study the uptake of Pt-NPs with a broad size distribution in HT29 colon carcinoma cells as a function of incubation time and incubation temperature. The cellular dose was quantified, that is, the amount and number density of NPs taken up by the cells, as well as the particle-size distribution. The results show a strong dependence of the amount of incubated NPs on the exposure time which can be understood by considering size-dependent diffusion and gravitational settling of the NPs in the cell culture medium.

Z-scan studies of the nonlinear optical properties of gold nanoparticles prepared by electron beam deposition.

PubMed

Mezher, M H; Nady, A; Penny, R; Chong, W Y; Zakaria, R

2015-11-20

This paper details the fabrication process for placing single-layer gold (Au) nanoparticles on a planar substrate, and investigation of the resulting optical properties that can be exploited for nonlinear optics applications. Preparation of Au nanoparticles on the substrate involved electron beam deposition and subsequent thermal dewetting. The obtained thin films of Au had a variation in thicknesses related to the controllable deposition time during the electron beam deposition process. These samples were then subjected to thermal annealing at 600°C to produce a randomly distributed layer of Au nanoparticles. Observation from field-effect scanning electron microscope (FESEM) images indicated the size of Au nanoparticles ranges from ∼13 to ∼48  nm. Details of the optical properties related to peak absorption of localized surface plasmon resonance (LSPR) of the nanoparticle were revealed by use of UV-Vis spectroscopy. The Z-scan technique was used to measure the nonlinear effects on the fabricated Au nanoparticle layers where it strongly relates LSPR and nonlinear optical properties.

Scanning electron microscopy as an analytical tool for the study of calcified intrauterine contraceptive devices

DOE Office of Scientific and Technical Information (OSTI.GOV)

Khan, S.R.; Wilkinson, E.J.

Within the endometrial cavity intrauterine contraceptive devices (IUDs) become encrusted with cellular, acellular, and fibrillar substances. Scanning electron microscopy was used to study the crust. Cellular material consisted mainly of blood cells and various types of bacteria. The fibrillar material appeared to be fibrin which was omnipresent in the crust and formed a thin layer immediately over the IUD surface. X-ray microanalysis of the acellular component of the crust revealed the presence of calcium. No other major peaks were identified. Near the IUD surface characteristic calcium phosphate crystals were present. Their microanalysis showed peaks for calcium and phosphorus. X-ray diffractionmore » of the crust however, showed it to contain only calcite. It is through the use of scanning electron microscopy that calcium phosphate has been detected in the IUD crust and a fibrillar layer has been visualized on the IUD surface. This study further demonstrates the effectiveness of SEM analytical techniques in the area of biomedical research.« less

Novel scanning electron microscope bulge test technique integrated with loading function

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Chuanwei; Xie, Huimin, E-mail: liuzw@bit.edu.cn, E-mail: xiehm@mail.tsinghua.edu.cn; Liu, Zhanwei, E-mail: liuzw@bit.edu.cn, E-mail: xiehm@mail.tsinghua.edu.cn

2014-10-15

Membranes and film-on-substrate structures are critical elements for some devices in electronics industry and for Micro Electro Mechanical Systems devices. These structures are normally at the scale of micrometer or even nanometer. Thus, the measurement for the mechanical property of these membranes poses a challenge over the conventional measurements at macro-scales. In this study, a novel bulge test method is presented for the evaluation of mechanical property of micro thin membranes. Three aspects are discussed in the study: (a) A novel bulge test with a Scanning Electron Microscope system realizing the function of loading and measuring simultaneously; (b) a simplifiedmore » Digital Image Correlation method for a height measurement; and (c) an imaging distortion correction by the introduction of a scanning Moiré method. Combined with the above techniques, biaxial modulus as well as Young's modulus of the polyimide film can be determined. Besides, a standard tensile test is conducted as an auxiliary experiment to validate the feasibility of the proposed method.« less

Atomic-scale observation of structural and electronic orders in the layered compound α-RuCl3

NASA Astrophysics Data System (ADS)

Ziatdinov, M.; Banerjee, A.; Maksov, A.; Berlijn, T.; Zhou, W.; Cao, H. B.; Yan, J.-Q.; Bridges, C. A.; Mandrus, D. G.; Nagler, S. E.; Baddorf, A. P.; Kalinin, S. V.

2016-12-01

A pseudospin-1/2 Mott phase on a honeycomb lattice is proposed to host the celebrated two-dimensional Kitaev model which has an elusive quantum spin liquid ground state, and fascinating physics relevant to the development of future templates towards topological quantum bits. Here we report a comprehensive, atomically resolved real-space study by scanning transmission electron and scanning tunnelling microscopies on a novel layered material displaying Kitaev physics, α-RuCl3. Our local crystallography analysis reveals considerable variations in the geometry of the ligand sublattice in thin films of α-RuCl3 that opens a way to realization of a spatially inhomogeneous magnetic ground state at the nanometre length scale. Using scanning tunnelling techniques, we observe the electronic energy gap of ~0.25 eV and intra-unit cell symmetry breaking of charge distribution in individual α-RuCl3 surface layer. The corresponding charge-ordered pattern has a fine structure associated with two different types of charge disproportionation at Cl-terminated surface.

Charging/discharge events in coated spacecraft polymers during electron beam irradiation in a scanning electron microscope

NASA Astrophysics Data System (ADS)

Czeremuszkin, G.; Latrèche, M.; Wertheimer, M. R.

2001-12-01

Spacecraft, such as those operating in geosynchronous orbit (GEO), can be subjected to intense irradiation by charged particles, for example high-energy (e.g. 20 keV) electrons. The surfaces of dielectric materials (for example, polymers used as "thermal blankets") can therefore become potential sites for damaging electrostatic discharge (ESD) pulse events. We simulate these conditions by examining small specimens of three relevant polymers (polyimide, polyester and fluoropolymer), both bare and coated, in a scanning electron microscope (SEM). The coatings examined include commercial indium-tin oxide (ITO), and thin films of SiO 2 and a-Si:H deposited by plasma-enhanced chemical vapor deposition (PECVD). All coatings are found to greatly modify the observed ESD behavior, compared with that of the bare polymer counterparts. These observations are explained in terms of the model for ESD pulses proposed by Frederickson.

Excimer laser annealing of NiTi shape memory alloy thin film

NASA Astrophysics Data System (ADS)

Xie, Qiong; Huang, Weimin; Hong, Ming Hui; Song, Wendong; Chong, Tow Chong

2003-02-01

NiTi Shape Memory Alloy (SMA) is with great potential for actuation in microsystems. It is particularly suitable for medical applications due to its excellent biocompatibility. In MEMS, local annealing of SMA is required in the process of fabrication. In this paper, local annealing of Ni52Ti48 SMA with excimer laser is proposed for the first time. The Ni52Ti48 thin film in a thickness of 5 μm was deposited on Si (100) wafer by sputtering at room temperature. After that, the thin film was annealed by excimer laser (248nm KrF laser) for the first time. Field-Emission Scanning Electron Microscopy (FESEM) and Atomic Force Microscopy (AFM) were used to characterize the surface profile of the deposited film after laser annealing. The phase transformation was measured by Differential Scanning Calorimeter (DSC) test. It is concluded that NiTi film sputtering on Si(100) substrate at room temperature possesses phase transformation after local laser annealing but with cracks.

Controllable self-induced passivation of hybrid lead iodide perovskites toward high performance solar cells.

PubMed

Chen, Qi; Zhou, Huanping; Song, Tze-Bin; Luo, Song; Hong, Ziruo; Duan, Hsin-Sheng; Dou, Letian; Liu, Yongsheng; Yang, Yang

2014-07-09

To improve the performance of the polycrystalline thin film devices, it requires a delicate control of its grain structures. As one of the most promising candidates among current thin film photovoltaic techniques, the organic/inorganic hybrid perovskites generally inherit polycrystalline nature and exhibit compositional/structural dependence in regard to their optoelectronic properties. Here, we demonstrate a controllable passivation technique for perovskite films, which enables their compositional change, and allows substantial enhancement in corresponding device performance. By releasing the organic species during annealing, PbI2 phase is presented in perovskite grain boundaries and at the relevant interfaces. The consequent passivation effects and underlying mechanisms are investigated with complementary characterizations, including scanning electron microscopy (SEM), X-ray diffraction (XRD), time-resolved photoluminescence decay (TRPL), scanning Kelvin probe microscopy (SKPM), and ultraviolet photoemission spectroscopy (UPS). This controllable self-induced passivation technique represents an important step to understand the polycrystalline nature of hybrid perovskite thin films and contributes to the development of perovskite solar cells judiciously.

Temperature dependence of gas sensing behaviour of TiO2 doped PANI composite thin films

NASA Astrophysics Data System (ADS)

Srivastava, Subodh; Sharma, S. S.; Sharma, Preetam; Sharma, Vinay; Rajura, Rajveer Singh; Singh, M.; Vijay, Y. K.

2014-04-01

In the present work we have reported the effect of temperature on the gas sensing properties of TiO2 doped PANI composite thin film based chemiresistor type gas sensors for hydrogen gas sensing application. PANI and TiO2 doped PANI composite were synthesized by in situ chemical oxidative polymerization of aniline at low temperature. The electrical properties of these composite thin films were characterized by I-V measurements as function of temperature. The I-V measurement revealed that conductivity of composite thin films increased as the temperature increased. The changes in resistance of the composite thin film sensor were utilized for detection of hydrogen gas. It was observed that at room temperature TiO2 doped PANI composite sensor shows higher response value and showed unstable behavior as the temperature increased. The surface morphology of these composite thin films has also been characterized by scanning electron microscopy (SEM) measurement.

Structural and magnetic properties of nanocrystalline NiFe2O4 thin film prepared by spray pyrolysis technique

NASA Astrophysics Data System (ADS)

Chavan, Apparao R.; Chilwar, R. R.; Shisode, M. V.; Hivrekar, Mahesh M.; Mande, V. K.; Jadhav, K. M.

2018-05-01

The nanocrystalline NiFe2O4 thin film has been prepared using a spray pyrolysis technique on glass substrate. The prepared thin film was characterized by using X-ray diffraction (XRD), Fourier transform Infrared spectroscopy (FTIR), and Field Emission-Scanning Electron Microscopy (FE-SEM) characterization techniques for the structural and microstructural analysis. The magnetic property was measured using vibrating sample magnetometer (VSM) at room temperature. X-ray diffraction studies show the formation of single phase spinel structure of the thin film. The octahedral and tetrahedral vibration in the sample was studied by Fourier transform infrared (FT-IR) spectra. Magnetic hysteresis loop was recorded for thin film at room temperature. At 15 kOe, saturation magnetization (Ms) was found to increase while coercivity (Hc) decreases with thickness of the NiFe2O4 thin film.

Functionalized antibiofilm thin coatings based on PLA-PVA microspheres loaded with usnic acid natural compounds fabricated by MAPLE

NASA Astrophysics Data System (ADS)

Grumezescu, Valentina; Socol, Gabriel; Grumezescu, Alexandru Mihai; Holban, Alina Maria; Ficai, Anton; Truşcǎ, Roxana; Bleotu, Coralia; Balaure, Paul Cǎtǎlin; Cristescu, Rodica; Chifiriuc, Mariana Carmen

2014-05-01

We report the fabrication of thin coatings of PLA-PVA microspheres loaded with usnic acid by matrix assisted pulsed laser evaporation (MAPLE) onto Ti substrate. The obtained coatings have been physico-chemically characterized by scanning electron microscopy (SEM) and infrared microscopy (IRM). In vitro biological assays have been performed in order to evaluate the influence of fabricated microsphere thin coatings on the Staphylococcus aureus biofilm development as well as their biocompatibility. SEM micrographs have revealed a uniform morphology of thin coatings, while IRM investigations have proved both the homogeneity and functional groups integrity of prepared thin coatings. The obtained microsphere-based thin coatings have proved to be efficient vehicles for usnic acid natural compound with antibiofilm activity, as demonstrated by the inhibitory activity on S. aureus mature biofilm development, opening new perspectives for the prevention and therapy associated to biofilm related infections.

[Study on anti-coagulant property of radio frequency sputtering nano-sized TiO2 thin films].

PubMed

Tang, Xiaoshan; Li, Da

2010-12-01

Nano-TiO2 thin films were prepared by Radio frequency (RF) sputtering on pyrolytic carbon substrates. The influences of sputtering power on the structure and the surface morphology of TiO2 thin films were investigated by X-ray diffraction (XRD), and by scanning electron microscopy (SEM). The results show that the TiO2 films change to anatase through the optimum of sputtering power. The mean diameter of nano-particle is about 30 nm. The anti-coagulant property of TiO2 thin films was observed through platelet adhesion in vitro. The result of experiment reveals the amount of thrombus on the TiO2 thin films being much less than that on the pyrolytic carbon. It also indicates that the RF sputtering Nano-sized TiO2 thin films will be a new kind of promising materials applied to artificial heart valve and endovascular stent.

Fracture resistance of dental nickel-titanium rotary instruments with novel surface treatment: Thin film metallic glass coating.

PubMed

Chi, Chih-Wen; Deng, Yu-Lun; Lee, Jyh-Wei; Lin, Chun-Pin

2017-05-01

Dental nickel-titanium (NiTi) rotary instruments are widely used in endodontic therapy because they are efficient with a higher success rate. However, an unpredictable fracture of instruments may happen due to the surface characteristics of imperfection (or irregularity). This study assessed whether a novel surface treatment could increase fatigue fracture resistance of dental NiTi rotary instruments. A 200- or 500-nm thick Ti-zirconium-boron (Ti-Zr-B) thin film metallic glass was deposited on ProTaper Universal F2 files using a physical vapor deposition process. The characteristics of coating were analyzed by scanning electron microscopy, transmission electron microscopy, and X-ray diffractometry. In cyclic fatigue tests, the files were performed in a simulated root canal (radius=5 mm, angulation=60°) under a rotating speed of 300rpm. The fatigue fractured cross sections of the files were analyzed with their fractographic performances through scanning electron microscopy images. The amorphous structure of the Ti-Zr-B coating was confirmed by transmission electron microscopy and X-ray diffractometry. The surface of treated files presented smooth morphologies without grinding irregularity. For the 200- and 500-nm surface treatment groups, the coated files exhibited higher resistance of cyclic fatigue than untreated files. In fractographic analysis, treated files showed significantly larger crack-initiation zone; however, no significant differences in the areas of fatigue propagation and catastrophic fracture were found compared to untreated files. The novel surface treatment of Ti-Zr-B thin film metallic glass on dental NiTi rotary files can effectively improve the fatigue fracture resistance by offering a smooth coated surface with amorphous microstructure. Copyright © 2016. Published by Elsevier B.V.

Characterization of nanostructured VO2 thin films grown by magnetron controlled sputtering deposition and post annealing method.

PubMed

Chen, Sihai; Lai, Jianjun; Dai, Jun; Ma, Hong; Wang, Hongchen; Yi, Xinjian

2009-12-21

By magnetron controlled sputtering system, a new nanostructured metastable monoclinic phase VO2 (B) thin film has been fabricated. The testing result shows that this nanostructured VO2 (B) thin film has high temperature coefficient of resistance (TCR) of -7%/K. Scanning electron microscopy measurement shows that the average grain diameter of the VO2 (B) crystallite is between 100 and 250 nm. After post annealed, VO2 (B) crystallite is changed into monoclinic (M) phase VO2 (M) crystallite with the average grain diameter between 20 and 50 nm. A set up of testing the thin film switching time is established. The test result shows the switching time is about 50 ms. With the nanostructured VO2 (B) and VO2 (M) thin films, optical switches and high sensitivity detectors will be presented.

Investigations of Si Thin Films as Anode of Lithium-Ion Batteries

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wu, Qingliu; Shi, Bing; Bareño, Javier

Amorphous silicon thin films having various thicknesses were investigated as a negative electrode material for lithium-ion batteries. Electrochemical characterization of the 20 nm thick thin silicon film revealed a very low first cycle Coulombic efficiency, which can be attributed to the silicon oxide layer formed on both the surface of the as-deposited Si thin film and the interface between the Si and the substrate. Among the investigated films, the 100 nm Si thin film demonstrated the best performance in terms of first cycle efficiency and cycle life. Observations from scanning electron microscopy demonstrated that the generation of cracks was inevitablemore » in the cycled Si thin films, even as the thickness of the film was as little as 20 nm, which was not predicted by previous modeling work. However, the cycling performance of the 20 and 100 nm silicon thin films was not detrimentally affected by these cracks. The poor capacity retention of the 1 mu m silicon thin film was attributed to the delamination.« less

Antimicrobial Activity of Thin Solid Films of Silver Doped Hydroxyapatite Prepared by Sol-Gel Method

PubMed Central

Iconaru, Simona Liliana; Chapon, Patrick; Le Coustumer, Philippe; Predoi, Daniela

2014-01-01

In this work, the preparation and characterization of silver doped hydroxyapatite thin films were reported and their antimicrobial activity was characterized. Silver doped hydroxyapatite (Ag:HAp) thin films coatings substrate was prepared on commercially pure Si disks by sol-gel method. The silver doped hydroxyapatite thin films were characterized by various techniques such as Scanning electron microscopy (SEM) with energy Dispersive X-ray attachment (X-EDS), Fourier transform infrared spectroscopy (FT-IR), and glow discharge optical emission spectroscopy (GDOES). These techniques have permitted the structural and chemical characterisation of the silver doped hydroxyapatite thin films. The antimicrobial effect of the Ag:HAp thin films on Escherichia coli and Staphylococcus aureus bacteria was then investigated. This is the first study on the antimicrobial effect of Ag:HAp thin films obtained by sol-gel method. The results of this study have shown that the Ag:HAp thin films with x Ag = 0.5 are effective against E. coli and S. aureus after 24 h. PMID:24523630

Antimicrobial activity of thin solid films of silver doped hydroxyapatite prepared by sol-gel method.

PubMed

Iconaru, Simona Liliana; Chapon, Patrick; Le Coustumer, Philippe; Predoi, Daniela

2014-01-01

In this work, the preparation and characterization of silver doped hydroxyapatite thin films were reported and their antimicrobial activity was characterized. Silver doped hydroxyapatite (Ag:HAp) thin films coatings substrate was prepared on commercially pure Si disks by sol-gel method. The silver doped hydroxyapatite thin films were characterized by various techniques such as Scanning electron microscopy (SEM) with energy Dispersive X-ray attachment (X-EDS), Fourier transform infrared spectroscopy (FT-IR), and glow discharge optical emission spectroscopy (GDOES). These techniques have permitted the structural and chemical characterisation of the silver doped hydroxyapatite thin films. The antimicrobial effect of the Ag:HAp thin films on Escherichia coli and Staphylococcus aureus bacteria was then investigated. This is the first study on the antimicrobial effect of Ag:HAp thin films obtained by sol-gel method. The results of this study have shown that the Ag:HAp thin films with x(Ag) = 0.5 are effective against E. coli and S. aureus after 24 h.

Electron transport in Bi2Se3 ultra thin films

NASA Astrophysics Data System (ADS)

Bauer, Sebastian; Bernhart, Alexander M.; Bobisch, Christian A.

2018-02-01

We studied the electronic transport properties of a 4 QL thin Bi2Se3 film in the hybridized phase on Si(111) by scanning tunneling potentiometry. When a transverse voltage is applied, the film exhibits a homogeneous electric field on the nm scale. In addition, thermovoltage signals with lateral nm variations are found which result from sample heating by the transverse current. The thermovoltage signals are directly correlated to morphological structures on the surface, i.e. step edges, and indicate a lateral variation of the local density of states at the Bi2Se3 surface. No discernible voltage drops appear at the surface so that the whole film serves as a current carrying medium and scattering at surface defects is less important.

Flexible pressure sensor based on graphene aerogel microstructures functionalized with CdS nanocrystalline thin film

NASA Astrophysics Data System (ADS)

Plesco, Irina; Dragoman, Mircea; Strobel, Julian; Ghimpu, Lidia; Schütt, Fabian; Dinescu, Adrian; Ursaki, Veaceslav; Kienle, Lorenz; Adelung, Rainer; Tiginyanu, Ion

2018-05-01

In this paper, we report on functionalization of graphene aerogel with a CdS thin film deposited by magnetron sputtering and on the development of flexible pressure sensors based on ultra-lightweight CdS-aerogel nanocomposite. Analysis by scanning electron microscopy, transmission electron microscopy and energy dispersive X-ray analysis disclose the uniform deposition of nanocrystalline CdS films with quasi-stoichiometric composition. The piezoresistive response of the aforementioned nanocomposite in the pressure range from 1 to 5 atm is found to be more than one order of magnitude higher than that inherent to suspended graphene membranes, leading to an average sensitivity as high as 3.2 × 10-4 kPa-1.

Super-resolution imaging based on the temperature-dependent electron-phonon collision frequency effect of metal thin films

NASA Astrophysics Data System (ADS)

Ding, Chenliang; Wei, Jingsong; Xiao, Mufei

2018-05-01

We herein propose a far-field super-resolution imaging with metal thin films based on the temperature-dependent electron-phonon collision frequency effect. In the proposed method, neither fluorescence labeling nor any special properties are required for the samples. The 100 nm lands and 200 nm grooves on the Blu-ray disk substrates were clearly resolved and imaged through a laser scanning microscope of wavelength 405 nm. The spot size was approximately 0.80 μm , and the imaging resolution of 1/8 of the laser spot size was experimentally obtained. This work can be applied to the far-field super-resolution imaging of samples with neither fluorescence labeling nor any special properties.

Analysis of compositional uniformity in Al{sub x}Ga{sub 1−x}N thin films using atom probe tomography and electron microscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Fang; Huang, Li; Porter, Lisa M.

2016-07-15

Calculated frequency distributions of atom probe tomography reconstructions (∼80 nm field of view) of very thin Al{sub x}Ga{sub 1−x}N (0.18 ≤ x ≤ 0.51) films grown via metalorganic vapor phase epitaxy on both (0001) GaN/AlN/SiC and (0001) GaN/sapphire heterostructures revealed homogeneous concentrations of Al and chemically abrupt Al{sub x}Ga{sub 1−x}N/GaN interfaces. The results of scanning transmission electron microscopy and selected area diffraction corroborated these results and revealed that neither superlattice ordering nor phase separation was present at nanometer length scales.

Precise and economic FIB/SEM for CLEM: with 2 nm voxels through mitosis.

PubMed

Luckner, Manja; Wanner, Gerhard

2018-05-23

A portfolio is presented documenting economic, high-resolution correlative focused ion beam scanning electron microscopy (FIB/SEM) in routine, comprising: (i) the use of custom-labeled slides and coverslips, (ii) embedding of cells in thin, or ultra-thin resin layers for correlative light and electron microscopy (CLEM) and (iii) the claim to reach the highest resolution possible with FIB/SEM in xyz. Regions of interest (ROIs) defined in light microscope (LM), can be relocated quickly and precisely in SEM. As proof of principle, HeLa cells were investigated in 3D context at all stages of the cell cycle, documenting ultrastructural changes during mitosis: nuclear envelope breakdown and reassembly, Golgi degradation and reconstitution and the formation of the midzone and midbody.

Facile preparation of optically transparent and hydrophobic cellulose nanofibril composite films

Treesearch

Yan Qing; Zhiyong Cai; Yiqiang Wu; Chunhua Yao; Qinglin Wu; Xianjun Li

2015-01-01

Cellulose nanofibril (CNF) and epoxy nanocomposites with high visible light transmittance and low watersensitivity were manufactured by laminating thin layers of epoxy resin onto CNF films prepared through,pressurized filtration in combination with oven drying. Scanning Electron Microscopy (SEM) studiessuggest that the resin component bonded to the CNF substrate well....

Raman scattering from rapid thermally annealed tungsten silicide

NASA Technical Reports Server (NTRS)

Kumar, Sandeep; Dasgupta, Samhita; Jackson, Howard E.; Boyd, Joseph T.

1987-01-01

Raman scattering as a technique for studying the formation of tungsten silicide is presented. The tungsten silicide films have been formed by rapid thermal annealing of thin tungsten films sputter deposited on silicon substrates. The Raman data are interpreted by using data from resistivity measurements, Auger and Rutherford backscattering measurements, and scanning electron microscopy.

Defects in oxide surfaces studied by atomic force and scanning tunneling microscopy

PubMed Central

König, Thomas; Simon, Georg H; Heinke, Lars; Lichtenstein, Leonid

2011-01-01

Summary Surfaces of thin oxide films were investigated by means of a dual mode NC-AFM/STM. Apart from imaging the surface termination by NC-AFM with atomic resolution, point defects in magnesium oxide on Ag(001) and line defects in aluminum oxide on NiAl(110), respectively, were thoroughly studied. The contact potential was determined by Kelvin probe force microscopy (KPFM) and the electronic structure by scanning tunneling spectroscopy (STS). On magnesium oxide, different color centers, i.e., F0, F+, F2+ and divacancies, have different effects on the contact potential. These differences enabled classification and unambiguous differentiation by KPFM. True atomic resolution shows the topography at line defects in aluminum oxide. At these domain boundaries, STS and KPFM verify F2+-like centers, which have been predicted by density functional theory calculations. Thus, by determining the contact potential and the electronic structure with a spatial resolution in the nanometer range, NC-AFM and STM can be successfully applied on thin oxide films beyond imaging the topography of the surface atoms. PMID:21977410

Metal-Insulator crossover in SrVO3 thin film

NASA Astrophysics Data System (ADS)

Wang, Gaomin; Wang, Zhen; Saghayezhian, Mohammad; Chen, Chen; Chen, Lina; Guo, Hangwen; Zhu, Yimei; Zhang, Jiandi

Paramagnetic metallic oxide SrVO3 (SVO) represents a prototype system for the study of the mechanism behind thickness-induced metal-to-insulator transition (MIT) or crossover due to its simple structure and itinerancy. Here SrVO3 thin films with different thicknesses were obtained through the layer-by-layer growth by laser Molecular Beam Epitaxy on SrTiO3 (001) surface. Ultraviolet Photoemission Spectroscopy and Scanning Tunneling Spectroscopy measurements confirm a MIT at the thickness of 3 unit cell, while atomically resolved Scanning Transmission Electron Microscopy and Electron Energy Loss Spectroscopy analysis reveal the depletion of Sr, change of V-valence and expansion of the out-of-plane lattice constant in the first three unit cell above the interface, thus different from the rest of the films. The existence of significant amount of oxygen vacancies is proposed, which is also supported by X-ray Photoelectron Spectroscopy, therefore providing a possible explanation of MIT. This work is primarily supported by U.S. DOE under Grant No. DOE DE-SC0002136. G.W. was supported by U.S. NSF under Grant No. DMR 16088865.

Investigation of the Structural, Electrical, and Optical Properties of the Nano-Scale GZO Thin Films on Glass and Flexible Polyimide Substrates

PubMed Central

Wang, Fang-Hsing; Chen, Kun-Neng; Hsu, Chao-Ming; Liu, Min-Chu; Yang, Cheng-Fu

2016-01-01

In this study, Ga2O3-doped ZnO (GZO) thin films were deposited on glass and flexible polyimide (PI) substrates at room temperature (300 K), 373 K, and 473 K by the radio frequency (RF) magnetron sputtering method. After finding the deposition rate, all the GZO thin films with a nano-scale thickness of about 150 ± 10 nm were controlled by the deposition time. X-ray diffraction patterns indicated that the GZO thin films were not amorphous and all exhibited the (002) peak, and field emission scanning electron microscopy showed that only nano-scale particles were observed. The dependences of the structural, electrical, and optical properties of the GZO thin films on different deposition temperatures and substrates were investigated. X-ray photoemission spectroscopy (XPS) was used to measure the elemental composition at the chemical and electronic states of the GZO thin films deposited on different substrates, which could be used to clarify the mechanism of difference in electrical properties of the GZO thin films. In this study, the XPS binding energy spectra of Ga2p3/2 and Ga2p1/2 peaks, Zn2p3/2 and Zn2p1/2 peaks, the Ga3d peak, and O1s peaks for GZO thin films on glass and PI substrates were well compared. PMID:28335216

Spatially Resolved Nano-Scale Characterization of Electronic States in SrTiO3(001) Surfaces by STM/STS

NASA Astrophysics Data System (ADS)

Iwaya, Katsuya; Ohsawa, Takeo; Shimizu, Ryota; Hashizume, Tomihiro; Hitosugi, Taro

2012-02-01

We have performed low temperature scanning tunneling microscopy/spectroscopy (STM/STS) measurements on TiO2-terminated SrTiO3(001) thin film surfaces. The conductance map exhibited electronic modulations that were completely different from the surface structure. We also found that the electronic modulations were strongly dependent on temperature and the density of atomic defects associated with oxygen vacancies. These results suggest the existence of strongly correlated two-dimensional electronic states near the SrTiO3 surface, implying the importance of electron correlation at the interfaces of SrTiO3-related heterostructures.

Sizes of X-ray radiation coherent domains in thin SmS films and their visualization

NASA Astrophysics Data System (ADS)

Sharenkova, N. V.; Kaminskii, V. V.; Petrov, S. N.

2011-09-01

The size of X-ray radiation coherent domains (250 ± 20 Å) is determined in a thin polycrystalline SmS film using X-ray diffraction patterns (θ-2θ scanning, DRON-2 diffractometer, Cu K α radiation) and the Selyakov-Scherrer formula with allowance for the effect of microstrains. An image of this film is taken with a transmission electron microscope, and regions with a characteristic size of 240 Å are clearly visible in it. It is concluded that X-ray radiation coherent domains are visualized.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Marimuthu, T.; Anandhan, N., E-mail: anandhan-kn@rediffmail.com; Mummoorthi, M.

Zinc oxide (ZnO) and zinc oxide/eosin yellow (ZnO/EY) thin films were potentiostatically deposited onto fluorine doped tin oxide (FTO) glass substrate. Effect of eosin yellow dye on structural, morphological and optical properties was studied. X-ray diffraction patterns, micro Raman spectra and photoluminescence (PL) spectra reveal hexagonal wurtzite structure with less atomic defects in 101 plane orientation of the ZnO/EY film. Scanning electron microscopy (SEM) images show flower for ZnO and porous like structure for ZnO/EY thin film, respectively. DSSC was constructed and evaluated by measuring the current density verses voltage curve.

Metastable and equilibrium phase formation in sputter-deposited Ti/Al multilayer thin films

NASA Astrophysics Data System (ADS)

Lucadamo, G.; Barmak, K.; Lavoie, C.; Cabral, C., Jr.; Michaelsen, C.

2002-06-01

The sequence and kinetics of metastable and equilibrium phase formation in sputter deposited multilayer thin films was investigated by combining in situ synchrotron x-ray diffraction (XRD) with ex situ electron diffraction and differential scanning calorimetry (DSC). The sequence included both cubic and tetragonal modifications of the equilibrium TiAl3 crystal structure. Values for the formation activation energies of the various phases in the sequence were determined using the XRD and DSC data obtained here, as well as activation energy data reported in the literature.

Apatitic connecting rings in moulds of Baculites sp. from the middle part of the Smoky Hill Member, Niobrara Chalk (Santonian), of western Kansas

USGS Publications Warehouse

Hasenmueller, W.A.; Hattin, D.E.

1985-01-01

Moulds of Baculites sp. are common in the Smoky Hill Member but only five known specimens contain connecting rings that have been preserved because of mineralisation by carbonate apatite. Analysis of four of these specimens suggests that the connecting rings were originally composed of organic material and were mineralised during early diagenesis. Thin sections and scanning electron microscopy demonstrate that the connecting rings had a two-layered structure consisting of a thick siphuncular wall and a thin pellicle. ?? 1985.

Structural, optical, and transport properties of nanocrystalline bismuth telluride thin films treated with homogeneous electron beam irradiation and thermal annealing.

PubMed

Takashiri, Masayuki; Asai, Yuki; Yamauchi, Kazuki

2016-08-19

We investigated the effects of homogeneous electron beam (EB) irradiation and thermal annealing treatments on the structural, optical, and transport properties of bismuth telluride thin films. Bismuth telluride thin films were prepared by an RF magnetron sputtering method at room temperature. After deposition, the films were treated with homogeneous EB irradiation, thermal annealing, or a combination of both the treatments (two-step treatment). We employed Williamson-Hall analysis for separating the strain contribution from the crystallite domain contribution in the x-ray diffraction data of the films. We found that strain was induced in the thin films by EB irradiation and was relieved by thermal annealing. The crystal orientation along c-axis was significantly enhanced by the two-step treatment. Scanning electron microscopy indicated the melting and aggregation of nano-sized grains on the film surface by the two-step treatment. Optical analysis indicated that the interband transition of all the thin films was possibly of the indirect type, and that thermal annealing and two-step treatment methods increased the band gap of the films due to relaxation of the strain. Thermoelectric performance was significantly improved by the two-step treatment. The power factor reached a value of 17.2 μW (cm(-1) K(-2)), approximately 10 times higher than that of the as-deposited thin films. We conclude that improving the crystal orientation and relaxing the strain resulted in enhanced thermoelectric performance.

Thin film assembly of nanosized cobalt(II) bis(5-phenyl-azo-8-hydroxyquinolate) using static step-by-step soft surface reaction technique: Structural characterization and optical properties.

PubMed

Seleim, S M; Hamdalla, Taymour A; Mahmoud, Mohamed E

2017-09-05

Nanosized (NS) cobalt (II) bis(5-phenyl-azo-8-hydroxyquinolate) (NS Co(II)-(5PA-8HQ) 2 ) thin films have been synthesized using static step-by-step soft surface reaction (SS-b-SSR) technique. Structural and optical characterizations of these thin films have been carried out using thermal gravimetric analysis (TGA), Fourier transform infrared (FT-IR), scanning electron microscopy (SEM), high resolution transmission electron microscopy (HR-TEM) and X-ray diffraction (XRD). The HR-TEM results revealed that the assembled Co(II)-complex exhibited a uniformly NS structure particles in the form of nanorods with width and length up to 16.90nm and 506.38nm, respectively. The linear and nonlinear optical properties have been investigated. The identified energy gap of the designed thin film materials was found 4.01eV. The refractive index of deposited Co(II)-complex thin film was identified by thickness-dependence and found as 1.9 at wavelength 1100nm. In addition, the refractive index was varied by about 0.15 due to an increase in the thickness by 19nm. Copyright © 2017 Elsevier B.V. All rights reserved.

Ternary Precursors for Depositing I-III-VI2 Thin Films for Solar Cells via Spray CVD

NASA Technical Reports Server (NTRS)

Banger, K. K.; Hollingsworth, J. A.; Jin, M. H.-C.; Harris, J. D.; Duraj, S. A.; Smith, M.; Scheiman, D.; Bohannan, E. W.; Switzer, J. A.; Buhro, W. E.

2002-01-01

The development of thin-film solar cells on flexible, lightweight, space-qualified substrates provides an attractive cost solution to fabricating solar arrays with high specific power (W/kg). Thin-film fabrication studies demonstrate that ternary single source precursors (SSP's) can be used in either a hot or cold-wall spray chemical vapour deposition (CVD) reactor, for depositing CuInS2, CuGaS2, and CuGaInS2 at reduced temperatures (400 to 450 C), which display good electrical and optical properties suitable for photovoltaic (PV) devices. X-ray diffraction studies, energy dispersive spectroscopy (EDS), and scanning electron microscopy (SEM) confirmed the formation of the single phase CIS, CGS, CIGS thin-films on various substrates at reduced temperatures.

Growing barium hexaferrite (BaFe{sub 12}O{sub 19}) thin films using chemical solution deposition

DOE Office of Scientific and Technical Information (OSTI.GOV)

Budiawanti, Sri, E-mail: awanty77@yahoo.com; Faculty of Teacher Training and Education, Sebelas Maret University; Soegijono, Bambang

Barium hexaferrite (BaFe{sub 12}O{sub 19}, or simply known as BaM) thin films has been recognized as a potential candidate for microwave-based devices, magnetic recording media and data storage. To grow BaM thin films, chemical solution deposition is conducted using the aqueous solution of metal nitrates, which involves spin coatings on Si substrates. Furthermore, Thermal Gravimeter Analysis (TGA), X-Ray Diffractometer (XRD), Scanning Electron Microscopy (SEM) and Vibrating Sample Magnetometer (VSM) are applied to evaluate the decomposition behavior, structure, morphology, and magnetic properties of BaM thin films. Additionally, the effects of number of layers variation are also investigated. Finally, magnetic properties analysismore » indicates the isotropic nature of the films.« less

Temperature dependent fabrication of cost-effective and nontoxic Cu{sub 2}ZnSnS{sub 4} (CZTS) thin films for solar cell

DOE Office of Scientific and Technical Information (OSTI.GOV)

Digraskar, Renuka, E-mail: renukad120@gmail.com; Sathe, Bhaskar, E-mail: bhaskarsathe@gmail.com; Gattu, Ketan

2016-05-06

In the present work, Cu{sub 2}ZnSnS{sub 4} (CZTS) thin films have been fabricated onto the glass substrate by simple and economic chemical bath deposition technique{sup 1}, and the effect of deposition temperature is reported. The deposition temperatures used were 50°C and 60°C for a deposition time of 60 min, which are significantly lower than earlier reports. These CZTS thin films were characterized for optical, electrical, morphological and elemental properties using, UV-Vis spectrophotometer, I-V system for photosensitivity, two probe resistivity system for resistivity, scanning electron microscopy, energy dispersive spectroscopy and Raman spectroscopy.

Electrochemical Liquid Phase Epitaxy (ec-LPE): A New Methodology for the Synthesis of Crystalline Group IV Semiconductor Epifilms.

PubMed

Demuth, Joshua; Fahrenkrug, Eli; Ma, Luyao; Shodiya, Titilayo; Deitz, Julia I; Grassman, Tyler J; Maldonado, Stephen

2017-05-24

Deposition of epitaxial germanium (Ge) thin films on silicon (Si) wafers has been achieved over large areas with aqueous feedstock solutions using electrochemical liquid phase epitaxy (ec-LPE) at low temperatures (T ≤ 90 °C). The ec-LPE method uniquely blends the simplicity and control of traditional electrodeposition with the material quality of melt growth. A new electrochemical cell design based on the compression of a liquid metal electrode into a thin cavity that enables ec-LPE is described. The epitaxial nature, low strain character, and crystallographic defect content of the resultant solid Ge films were analyzed by electron backscatter diffraction, scanning transmission electron microscopy, high resolution X-ray diffraction, and electron channeling contrast imaging. The results here show the first step toward a manufacturing infrastructure for traditional crystalline inorganic semiconductor epifilms that does not require high temperature, gaseous precursors, or complex apparatus.

Thin single-crystalline Bi2(Te1-xSex)3 ternary nanosheets synthesized by a solvothermal technique

NASA Astrophysics Data System (ADS)

Guo, Jing; Jian, Jikang; Zhang, Zhihua; Wu, Rong; Li, Jin; Sun, Yanfei

2016-01-01

Bi2(Te1-xSex)3 ternary nanosheets have been successfully synthesized through a facile solvothermal technique using diethylenetriamine as solvent, where x can vary from 0 to 1. X-ray diffraction (XRD) and Scanning electron microscopy (SEM) indicate that the as-synthesized Bi2(Te1-xSex)3 samples are nanosheets with rhombohedral structure, and the thickness of the nanosheets can be as thin as several nanometers. High resolution transmission electron microscopy (HRTEM) and selected area electron diffraction (SAED) reveal that the nanosheets are single crystalline with a rhombohedral structure. Energy disperse spectroscopy (EDS) and XRD analysis by Vegard's law confirm that the ternary Bi2(Te1-xSex)3 nanosheets have been obtained here. The growth of the nanosheets is discussed based on an amine-based molecular template mechanism that has been employed to synthesize some other metal chalcogenides.

Nanoscale electron transport at the surface of a topological insulator.

PubMed

Bauer, Sebastian; Bobisch, Christian A

2016-04-21

The use of three-dimensional topological insulators for disruptive technologies critically depends on the dissipationless transport of electrons at the surface, because of the suppression of backscattering at defects. However, in real devices, defects are unavoidable and scattering at angles other than 180° is allowed for such materials. Until now, this has been studied indirectly by bulk measurements and by the analysis of the local density of states in close vicinity to defect sites. Here, we directly measure the nanoscale voltage drop caused by the scattering at step edges, which occurs if a lateral current flows along a three-dimensional topological insulator. The experiments were performed using scanning tunnelling potentiometry for thin Bi2Se3 films. So far, the observed voltage drops are small because of large contributions of the bulk to the electronic transport. However, for the use of ideal topological insulating thin films in devices, these contributions would play a significant role.

Nanoscale electron transport at the surface of a topological insulator

NASA Astrophysics Data System (ADS)

Bauer, Sebastian; Bobisch, Christian A.

2016-04-01

The use of three-dimensional topological insulators for disruptive technologies critically depends on the dissipationless transport of electrons at the surface, because of the suppression of backscattering at defects. However, in real devices, defects are unavoidable and scattering at angles other than 180° is allowed for such materials. Until now, this has been studied indirectly by bulk measurements and by the analysis of the local density of states in close vicinity to defect sites. Here, we directly measure the nanoscale voltage drop caused by the scattering at step edges, which occurs if a lateral current flows along a three-dimensional topological insulator. The experiments were performed using scanning tunnelling potentiometry for thin Bi2Se3 films. So far, the observed voltage drops are small because of large contributions of the bulk to the electronic transport. However, for the use of ideal topological insulating thin films in devices, these contributions would play a significant role.

Room Temperature Gas Sensing Properties of Sn-Substituted Nickel Ferrite (NiFe2O4) Thin Film Sensors Prepared by Chemical Co-Precipitation Method

NASA Astrophysics Data System (ADS)

Manikandan, V.; Li, Xiaogan; Mane, R. S.; Chandrasekaran, J.

2018-04-01

Tin (Sn) substituted nickel ferrite (NiFe2O4) thin film sensors were prepared by a simple chemical co-precipitation method, which initially characterized their structure and surface morphology with the help of x-ray diffraction and scanning electron microscopy. Surface morphology of the sensing films reveals particles stick together with nearer particles and this formation leads to a large specific area as a large specific area is very useful for easy adsorption of gas molecules. Transmission electron microscopy and selected area electron diffraction pattern images confirm particle size and nanocrystallnity as due to formation of circular rings. Fourier transform infrared analysis has supported the presence of functional groups. The 3.69 eV optical band gap of the film was found which enabled better gas sensing. Gas sensors demonstrate better response and recovery characteristics, and the maximum response was 68.43%.

Enhanced conductivity at orthorhombic–rhombohedral phase boundaries in BiFeO 3 thin films

DOE PAGES

Heo, Yooun; Lee, Jin Hong; Xie, Lin; ...

2016-08-26

Enhanced properties in modern functional materials can often be found at structural transition regions, such as morphotropic phase boundaries (MPB), owing to the coexistence of multiple phases with nearly equivalent energies. Strain-engineered MPBs have emerged in epitaxially grown BiFeO 3 (BFO) thin films by precisely tailoring a compressive misfit strain, leading to numerous intriguing phenomena, such as a massive piezoelectric response, magnetoelectric coupling, interfacial magnetism and electronic conduction. Recently, an orthorhombic–rhombohedral (O–R) phase boundary has also been found in tensile-strained BFO. In this study, we characterise the crystal structure and electronic properties of the two competing O and R phasesmore » using X-ray diffraction, scanning probe microscope and scanning transmission electron microscopy (STEM). We observe the temperature evolution of R and O domains and find that the domain boundaries are highly conductive. Temperature-dependent measurements reveal that the conductivity is thermally activated for R–O boundaries. STEM observations point to structurally wide boundaries, significantly wider than in other systems. Furthermore, we reveal a strong correlation between the highly conductive domain boundaries and structural material properties. These findings provide a pathway to use phase boundaries in this system for novel nanoelectronic applications.« less

Morphology and crystallinity of ZnS nanocolumns prepared by glancing angle deposition.

PubMed

Lu, Lifang; Zhang, Fujun; Xu, Zheng; Zhao, Suling; Wang, Yongsheng

2010-03-01

ZnS films with different morphologies and nanometer structures were fabricated via high vacuum electron beam deposition by changing the oblique angle alpha between the incoming particle flux and the substrate normal. The morphology and crystallinity of ZnS nanocrystalline films prepared on the substrates at alpha = 0 degrees and 80 degrees were characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), and X-ray diffraction. These experimental results show that the ZnS nanocolumn structure was formed at the situation of alpha = 80 degrees. The incidence angle also strongly influenced the crystallinity of thin films. The most intensive diffraction peaks changed from (220) to (111) when the incidence angle was set to 0 degrees and 80 degrees. The dynamic growth process of ZnS films at alpha = 0 degrees and 80 degrees has been analyzed by shadow effect and atomic surface diffusion. The transmittance spectra of the ZnS thin films prepared at different oblique angles were measured, and the transmissivity of ZnS nanocolumn thin films was enhanced compared with ZnS thin films prepared by normal deposition in the visible light range.

Influence of sulfurization temperature on Cu2ZnSnS4 absorber layer on flexible titanium substrates for thin film solar cells

NASA Astrophysics Data System (ADS)

Gokcen Buldu, Dilara; Cantas, Ayten; Turkoglu, Fulya; Gulsah Akca, Fatime; Meric, Ece; Ozdemir, Mehtap; Tarhan, Enver; Ozyuzer, Lutfi; Aygun, Gulnur

2018-02-01

In this study, the effect of sulfurization temperature on the morphology, composition and structure of Cu2ZnSnS4 (CZTS) thin films grown on titanium (Ti) substrates has been investigated. Since Ti foils are flexible, they were preferred as a substrate. As a result of their flexibility, they allow large area manufacturing and roll-to-roll processes. To understand the effects of sulfurization temperature on the CZTS formation on Ti foils, CZTS films fabricated with various sulfurization temperatures were investigated with several analyses including x-ray diffraction (XRD), scanning electron microscopy (SEM), x-ray photoelectron spectroscopy and Raman scattering. XRD measurements showed a sharp and intense peak coming from the (112) planes of the kesterite type lattice structure (KS), which is strong evidence for good crystallinity. The surface morphologies of our thin films were investigated using SEM. Electron dispersive spectroscopy was also used for the compositional analysis of the thin films. According to these analysis, it is observed that Ti foils were suitable as substrates for the growth of CZTS thin films with desired properties and the sulfurization temperature plays a crucial role for producing good quality CZTS thin films on Ti foil substrates.

Domain matched epitaxial growth of (111) Ba{sub 0.5}Sr{sub 0.5}TiO{sub 3} thin films on (0001) Al{sub 2}O{sub 3} with ZnO buffer layer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Krishnaprasad, P. S., E-mail: pskrishnaprasu@gmail.com, E-mail: mkj@cusat.ac.in; Jayaraj, M. K., E-mail: pskrishnaprasu@gmail.com, E-mail: mkj@cusat.ac.in; Antony, Aldrin

2015-03-28

Epitaxial (111) Ba{sub 0.5}Sr{sub 0.5}TiO{sub 3} (BST) thin films have been grown by pulsed laser deposition on (0001) Al{sub 2}O{sub 3} substrate with ZnO as buffer layer. The x-ray ω-2θ, Φ-scan and reciprocal space mapping indicate epitaxial nature of BST thin films. The domain matched epitaxial growth of BST thin films over ZnO buffer layer was confirmed using Fourier filtered high resolution transmission electron microscope images of the film-buffer interface. The incorporation of ZnO buffer layer effectively suppressed the lattice mismatch and promoted domain matched epitaxial growth of BST thin films. Coplanar inter digital capacitors fabricated on epitaxial (111) BSTmore » thin films show significantly improved tunable performance over polycrystalline thin films.« less

Synthesis, characterization and oxidation of metallic cobalt (Co) thin film into semiconducting cobalt oxide (Co3O4)thin film using microwave plasma CVD

NASA Astrophysics Data System (ADS)

Rahman Ansari, Akhalakur; Hussain, Shahir; Imran, Mohd; Abdel-wahab, M. Sh; Alshahrie, Ahmed

2018-06-01

The pure cobalt thin film was deposited on the glass substrate by using DC magnetron sputtering and then exposed to microwave assist oxygen plasma generated in microwave plasma CVD. The oxidation process of Co thin film into Co3O4 thin films with different microwave power and temperature were studied. The influences of microwave power, temperature and irradiation time were investigated on the morphology and particle size of oxide thin films. The crystal structure, chemical conformation, morphologies and optical properties of oxidized Co thin films (Co3O4) were studied by using x-ray diffraction (XRD), Field emission scanning electron microscopy (FESEM), Raman Spectroscopy and UV–vis Spectroscopy. The data of these films showed complete oxidation pure metallic cobalt (Co) into cobalt oxide (Co3O4). The optical properties were studied for calculating the direct band gaps which ranges from 1.35 to 1.8 eV.

Investigation of Selective Laser Melting Surface Alloyed Aluminium Metal Matrix Dispersive Reinforced Layers

NASA Astrophysics Data System (ADS)

Kamburov, V. V.; Dimitrova, R. B.; Kandeva, M. K.; Sofronov, Y. P.

2018-01-01

The aim of the paper is to investigate the improvement of mechanical properties and in particular wear resistance of laser surface alloyed dispersive reinforced thin layers produced by selective laser melting (SLM) technology. The wear resistance investigation of aluminium matrix composite layers in the conditions of dry friction surface with abrasive particles and nanoindentation tests were carried out. The process parameters (as scan speed) and their impact on the wear resistant layers have been evaluated. The alloyed layers containing metalized SiC particles were studied by Optical and Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray microanalysis (EDX). The obtained experimental results of the laser alloyed thin layers show significant development of their wear resistance and nanohardness due to the incorporated reinforced phase of electroless nickel coated SiC particles.

Analyzing indirect secondary electron contrast of unstained bacteriophage T4 based on SEM images and Monte Carlo simulations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ogura, Toshihiko, E-mail: t-ogura@aist.go.jp

2009-03-06

The indirect secondary electron contrast (ISEC) condition of the scanning electron microscopy (SEM) produces high contrast detection with minimal damage of unstained biological samples mounted under a thin carbon film. The high contrast image is created by a secondary electron signal produced under the carbon film by a low acceleration voltage. Here, we show that ISEC condition is clearly able to detect unstained bacteriophage T4 under a thin carbon film (10-15 nm) by using high-resolution field emission (FE) SEM. The results show that FE-SEM provides higher resolution than thermionic emission SEM. Furthermore, we investigated the scattered electron area within themore » carbon film under ISEC conditions using Monte Carlo simulation. The simulations indicated that the image resolution difference is related to the scattering width in the carbon film and the electron beam spot size. Using ISEC conditions on unstained virus samples would produce low electronic damage, because the electron beam does not directly irradiate the sample. In addition to the routine analysis, this method can be utilized for structural analysis of various biological samples like viruses, bacteria, and protein complexes.« less

Effect of copper and nickel doping on the optical and structural properties of ZnO

NASA Astrophysics Data System (ADS)

Muǧlu, G. Merhan; Sarıtaş, S.; ćakıcı, T.; Şakar, B.; Yıldırım, M.

2017-02-01

The present study is focused on the Cu doped ZnO and Ni doped ZnO dilute magnetic semiconductor thin films. ZnO:Cu and ZnO:Ni thin films were grown by Chemically Spray Pyrolysis (CSP) method on glass substrates. Optical analysis of the films was done spectral absorption and transmittance measurements by UV-Vis double beam spectrophotometer technique. The structure, morphology, topology and elemental analysis of ZnO:Cu and ZnO:Ni dilute magnetic thin films were investigated by X-ray diffraction (XRD), Raman Analysis, field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDX), atomic force microscopy (AFM) techniques, respectively. Also The magnetic properties of the ZnO:Ni thin film was investigated by vibrating sample magnetometer (VSM) method. VSM measurements of ZnO:Ni thin film showed that the ferromagnetic behavior.

Seebeck coefficient of synthesized Titanium Dioxide thin film on FTO glass substrate

NASA Astrophysics Data System (ADS)

Usop, R.; Hamed, N. K. A.; Megat Hasnan, M. M. I.; Ikeda, H.; Sabri, M. F. M.; Ahmad, M. K.; Said, S. M.; Salleh, F.

2018-04-01

In order to fabricate a thermoelectric device on glass substrate for harvesting waste heat energy through house appliances, the Seebeck coefficient of translucent TiO2 thin film was investigated. The TiO2 thin film was synthesized by using hydrothermal method with F-SnO2 coated glass as substrate. From scanning electron microscopy analysis, the synthesized TiO2 thin film was found to be in nanometer-scale rod structure with a thickness of 4 µm. The Seebeck coefficient was measured in the temperature range of 300 – 400 K. The Seebeck coefficient is found to be in negative value which shows that synthesized film is an n-type semiconductor material, and is lower than the value of bulk-size material. This reduction in Seebeck coefficient of TiO2 thin film is likely due to the low dimensional effect and the difference of carrier concentration.

Cross section TEM characterization of high-energy-Xe-irradiated U-Mo

DOE PAGES

Ye, B.; Jamison, L.; Miao, Y.; ...

2017-03-09

U-Mo alloys irradiated with 84 MeV Xe ions to various doses were characterized with transmission electron microscopy (TEM) and scanning transmission electron microscopy (STEM) techniques. The TEM thin foils were prepared perpendicular to the irradiated surface to allow a direct observation of the entire region modified by ions. Furthermore, depth-selective microstructural information was revealed. Varied irradiation-induced phenomena such as gas bubble formation, phase reversal, and recrystallization were observed at different ion penetration depths in U-Mo.

Metal-Coated Optical Fibers for High Temperature Applications

NASA Technical Reports Server (NTRS)

Zeakes, Jason; Murphy, Kent; Claus, Richard; Greene, Jonathan; Tran, Tuan

1996-01-01

A DC magnetron sputtering system has been used to actively coat optical fibers with hermetic metal coatings during the fiber draw process. Thin films of Inconel 625 have been deposited on optical fibers and annealed in air at 2000 F. Scanning electron microscopy and Auger electron microscopy have been used to investigate the morphology and composition of the films prior to and following thermal cycling. Issues to be addressed include film adhesion, other coating materials, and a discussion of additional applications for this novel technology.

Emission properties of body-centered cubic elemental metal photocathodes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Tuo; Rickman, Benjamin L., E-mail: brickm2@uic.edu; Schroeder, W. Andreas

2015-04-07

A first principles analysis of photoemission is developed to explain the lower than expected rms transverse electron momentum measured using the solenoid scan technique for the body-centered cubic Group Vb (V, Nb, and Ta) and Group VIb (Cr, Mo, and W) metallic photocathodes. The density functional theory based analysis elucidates the fundamental role that the electronic band structure (and its dispersion) plays in determining the emission properties of solid-state photocathodes and includes evaluation of work function anisotropy using a thin-slab method.

Effects of air annealing on CdS quantum dots thin film grown at room temperature by CBD technique intended for photosensor applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shaikh, Shaheed U.; Desale, Dipalee J.; Siddiqui, Farha Y.

2012-11-15

Graphical abstract: The effect of different intensities (40, 60 100 and 200 W) of light on CdS quantum dots thin film annealed at 350 °C indicating enhancement in (a) photo-current and (b) photosensitivity. Highlights: ► The preparation of CdS nanodot thin film at room temperature by M-CBD technique. ► Study of air annealing on prepared CdS nanodots thin film. ► The optimized annealing temperature for CdS nanodot thin film is 350 °C. ► Modified CdS thin films can be used in photosensor application. -- Abstract: CdS quantum dots thin-films have been deposited onto the glass substrate at room temperature usingmore » modified chemical bath deposition technique. The prepared thin films were further annealed in air atmosphere at 150, 250 and 350 °C for 1 h and subsequently characterized by scanning electron microscopy, ultraviolet–visible spectroscopy, electrical resistivity and I–V system. The modifications observed in morphology and opto-electrical properties of the thin films are presented.« less

Multi-Resolution Imaging of Electron Dynamics in Nanostructure Interfaces

DTIC Science & Technology

2010-07-27

metallic carbon nanotubes from semiconducting ones. In pentacene transistors, we used scanning photocurrent microscopy to study spatially resolved...photoelectric response of pentacene thin films, which showed that point contacts formed near the hole injection points limit the overall performance of the...photothermal current microscopy, carbon nanotube transistor, pentacene transistor, contact resistance, hole injection 16. SECURITY CLASSIFICATION OF

Electrical characterization of grain boundaries of CZTS thin films using conductive atomic force microscopy techniques

DOE Office of Scientific and Technical Information (OSTI.GOV)

Muhunthan, N.; Singh, Om Pal; Toutam, Vijaykumar, E-mail: toutamvk@nplindia.org

2015-10-15

Graphical abstract: Experimental setup for conducting AFM (C-AFM). - Highlights: • Cu{sub 2}ZnSnS{sub 4} (CZTS) thin film was grown by reactive co-sputtering. • The electronic properties were probed using conducting atomic force microscope, scanning Kelvin probe microscopy and scanning capacitance microscopy. • C-AFM current flow mainly through grain boundaries rather than grain interiors. • SKPM indicated higher potential along the GBs compared to grain interiors. • The SCM explains that charge separation takes place at the interface of grain and grain boundary. - Abstract: Electrical characterization of grain boundaries (GB) of Cu-deficient CZTS (Copper Zinc Tin Sulfide) thin films wasmore » done using atomic force microscopic (AFM) techniques like Conductive atomic force microscopy (CAFM), Kelvin probe force microscopy (KPFM) and scanning capacitance microscopy (SCM). Absorbance spectroscopy was done for optical band gap calculations and Raman, XRD and EDS for structural and compositional characterization. Hall measurements were done for estimation of carrier mobility. CAFM and KPFM measurements showed that the currents flow mainly through grain boundaries (GB) rather than grain interiors. SCM results showed that charge separation mainly occurs at the interface of grain and grain boundaries and not all along the grain boundaries.« less

Phase change studies in Se85In15-xZnx chalcogenide thin films

NASA Astrophysics Data System (ADS)

Srivastava, Archana; Tiwari, S. N.; Alvi, M. A.; Khan, Shamshad A.

2018-03-01

This research work describes the phase change studies in Se85In15-xZnx thin films at various annealing temperatures. Glassy samples of Se85In15-xZnx were synthesized by the melt quenching method and thin films of thickness 400 nm were prepared by the vacuum evaporation technique on a glass/Si wafer substrate. The glass transition temperature (Tg) and the on-set crystallization temperature (Tc) of the prepared alloys were evaluated by non-isothermal differential scanning calorimetry studies. Thin films were annealed at three temperatures 330 K, 340 K, and 350 K (which are in between Tg and Tc of the synthesized samples) in a vacuum furnace for 2 h. High resolution X-ray diffraction studies demonstrate that the as-prepared films are amorphous in nature whereas the annealed films are of crystalline/polycrystalline in nature. Field emission scanning electron microscopy studies of thin films (as-deposited and crystallized) confirm the phase transformation in Se85In15-xZnx thin films. Optical band gaps were calculated from the Tauc's extrapolation procedure and were found to be enhanced with the Zn concentration and decrease with the increasing annealing temperature. Various optical parameters were evaluated for as-prepared and annealed Se85In15-xZnx thin films. The changes in optical parameters with annealing temperature were described on the basis of structural relaxation as well as changes in defect states and density of localized states during amorphous to crystalline phase transformation in Se85In15-xZnx thin films.

Structural, optical and nonlinear optical studies of AZO thin film prepared by SILAR method for electro-optic applications

NASA Astrophysics Data System (ADS)

Edison, D. Joseph; Nirmala, W.; Kumar, K. Deva Arun; Valanarasu, S.; Ganesh, V.; Shkir, Mohd.; AlFaify, S.

2017-10-01

Aluminium doped (i.e. 3 at%) zinc oxide (AZO) thin films were prepared by simple successive ionic layer adsorption and reaction (SILAR) method with different dipping cycles. The structural and surface morphology of AZO thin films were studied by using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The optical parameters such as, transmittance, band gap, refractive index, extinction coefficient, dielectric constant and nonlinear optical properties of AZO films were investigated. XRD pattern revealed the formation of hexagonal phase ZnO and the intensity of the film was found to increase with increasing dipping cycle. The crystallite size was found to be in the range of 29-37 nm. Scanning Electron Microscope (SEM) images show the presence of small sized grains, revealing that the smoothest surface was obtained at all the films. The EDAX spectrum of AZO conforms the presence of Zn, O and Al. The optical transmittance in the visible region is high 87% and the band gap value is 3.23 eV. The optical transmittance is decreased with respect to dipping cycles. The room temperature PL studies revealed that the AZO films prepared at (30 cycles) has good film quality with lesser defect density. The third order nonlinear optical parameters were also studied using Z-scan technique to know the applications of deposited films in nonlinear devices. The third order nonlinear susceptibility value is found to be 1.69 × 10-7, 3.34 × 10-8, 1.33 × 10-7and 2.52 × 10-7 for AZO films deposited after 15, 20, 25 and 30 dipping cycles.

Atomic-scale identification of novel planar defect phases in heteroepitaxial YBa2Cu3O7-δ thin films

NASA Astrophysics Data System (ADS)

Gauquelin, Nicolas; Zhang, Hao; Zhu, Guozhen; Wei, John Y. T.; Botton, Gianluigi A.

2018-05-01

We have discovered two novel types of planar defects that appear in heteroepitaxial YBa2Cu3O7-δ (YBCO123) thin films, grown by pulsed-laser deposition (PLD) either with or without a La2/3Ca1/3MnO3 (LCMO) overlayer, using the combination of high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) imaging and electron energy loss spectroscopy (EELS) mapping for unambiguous identification. These planar lattice defects are based on the intergrowth of either a BaO plane between two CuO chains or multiple Y-O layers between two CuO2 planes, resulting in non-stoichiometric layer sequences that could directly impact the high-Tc superconductivity.

Transmission Kikuchi diffraction and transmission electron forescatter imaging of electropolished and FIB manufactured TEM specimens

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zieliński, W., E-mail: wiziel@inmat.pw.edu.pl; Płociński, T.; Kurzydłowski, K.J.

2015-06-15

We present a study of the efficiency of the utility of scanning electron microscope (SEM)-based transmission methods for characterizing grain structure in thinned bulk metals. Foils of type 316 stainless steel were prepared by two methods commonly used for transmission electron microscopy — double-jet electropolishing and focused ion beam milling. A customized holder allowed positioning of the foils in a configuration appropriate for both transmission electron forward scatter diffraction, and for transmission imaging by the use of a forescatter detector with two diodes. We found that both crystallographic orientation maps and dark-field transmitted images could be obtained for specimens preparedmore » by either method. However, for both methods, preparation-induced artifacts may affect the quality or accuracy of transmission SEM data, especially those acquired by the use of transmission Kikuchi diffraction. Generally, the quality of orientation data was better for specimens prepared by electropolishing, due to the absence of ion-induced damage. - Highlights: • The transmission imaging and diffraction techniques are emerging in scanning electron microscopy (SEM) as promising new field of materials characterization. • The manuscript titled: “Transmission Kikuchi Diffraction and Transmission Electron Forescatter Imaging of Electropolished and FIB Manufactured TEM Specimens” documents how different specimen thinning procedures can effect efficiency of transmission Kikuchi diffraction and transmission electron forescatter imaging. • The abilities to make precision crystallographic orientation maps and dark-field images in transmission was studied on electropolished versus focus ion beam manufactured TEM specimens. • Depending on the need, electropolished and focused ion beam technique may produce suitable specimens for transmission imaging and diffraction in SEM.« less

A feasible method to eliminate nanoleakage in dentin hybrid layers.

PubMed

Chen, Ji-Hua; Liu, Yan; Niu, Li-Na; Lu, Shuai; Tay, Franklin R; Gao, Yu

2014-10-01

To determine whether high-pressure air blowing during adhesive application affects the infiltration of resin comonomers and nanoleakage manifestation in the resin/dentin interface under simulated pulpal pressure. Thirty mid-coronal dentin surfaces were bonded with an etch-and-rinse adhesive (Adper Single Bond 2) under simulated pulpal pressure. In the control group, the adhesive was thinned by ordinary air blowing with a pressure of 0.2 MPa, while in the experimental group, a high-pressure air blowing technique (pressure: 0.4 MPa) was used. All other procedures followed the manufacturer's instructions. Resin tag formation and nanoleakage in the bonding interface were evaluated with scanning electron microscopy (SEM) and transmission electron microscopy (TEM). When adhesive was thinned with high pressure air blowing, longer and more homogeneous resin tags were formed. The bonding interface demonstrated good overall morphology and integrity. Almost perfect infiltration of resin and no obvious nanoleakage were observed. Thinning of adhesive with high-pressure air blowing provides a clinically feasible adjunctive procedure for better resin infiltration.

Electrical four-point probing of spherical metallic thin films coated onto micron sized polymer particles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pettersen, Sigurd R., E-mail: sigurd.r.pettersen@ntnu.no, E-mail: jianying.he@ntnu.no; Stokkeland, August Emil; Zhang, Zhiliang

Micron-sized metal-coated polymer spheres are frequently used as filler particles in conductive composites for electronic interconnects. However, the intrinsic electrical resistivity of the spherical thin films has not been attainable due to deficiency in methods that eliminate the effect of contact resistance. In this work, a four-point probing method using vacuum compatible piezo-actuated micro robots was developed to directly investigate the electric properties of individual silver-coated spheres under real-time observation in a scanning electron microscope. Poly(methyl methacrylate) spheres with a diameter of 30 μm and four different film thicknesses (270 nm, 150 nm, 100 nm, and 60 nm) were investigated. By multiplying the experimental resultsmore » with geometrical correction factors obtained using finite element models, the resistivities of the thin films were estimated for the four thicknesses. These were higher than the resistivity of bulk silver.« less

Characterization of the thin-film NbN superconductor for single-photon detection by transport measurements

NASA Astrophysics Data System (ADS)

Lin, Shi-Zeng; Ayala-Valenzuela, Oscar; McDonald, Ross D.; Bulaevskii, Lev N.; Holesinger, Terry G.; Ronning, Filip; Weisse-Bernstein, Nina R.; Williamson, Todd L.; Mueller, Alexander H.; Hoffbauer, Mark A.; Rabin, Michael W.; Graf, Matthias J.

2013-05-01

The fabrication of high-quality thin superconducting films is essential for single-photon detectors. Their device performance is crucially affected by their material parameters, thus requiring reliable and nondestructive characterization methods after the fabrication and patterning processes. Important material parameters to know are the resistivity, superconducting transition temperature, relaxation time of quasiparticles, and uniformity of patterned wires. In this work, we characterize micropatterned thin NbN films by using transport measurements in magnetic fields. We show that from the instability of vortex motion at high currents in the flux-flow state of the IV characteristic, the inelastic lifetime of quasiparticles can be determined to be about 2 ns. Additionally, from the depinning transition of vortices at low currents, as a function of magnetic field, the size distribution of grains can be extracted. This size distribution is found to be in agreement with the film morphology obtained from scanning electron microscopy and high-resolution transmission electron microscopy images.

Enhanced photoelectrochemical performance of Ti-doped hematite thin films prepared by the sol-gel method

NASA Astrophysics Data System (ADS)

Lian, Xiaojuan; Yang, Xin; Liu, Shangjun; Xu, Ying; Jiang, Chunping; Chen, Jinwei; Wang, Ruilin

2012-01-01

Ti-doped α-Fe2O3 thin films were successfully prepared on FTO substrates by the sol-gel route. Hematite film was characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and energy dispersive spectrometer (EDS). The XRD data showed α-Fe2O3 had a preferred (1 1 0) orientation which belonged to the rhombohedral system. Interestingly, the grains turned into worm-like shape after annealed at high temperature. The IPCE could reach 32.6% at 400 nm without any additional potential vs. SCE. Titanium in the lattice can affect the photo electro chemical performance positively by increasing the conductivity of the thin film. So the excited electrons and holes could live longer, rather than recombining with each other rapidly as undoped hematite. And the efficient carrier density on the Ti-doped anode surface was higher than the undoped anode, which contribute to the well PEC performance.

Study of the optical properties of CuAlS2 thin films prepared by two methods

NASA Astrophysics Data System (ADS)

Ahmad, S. M.

2017-04-01

CuAlS2 thin films were successfully deposited on glass substrates using two methods: chemical spray pyrolysis (CSP) and chemical bath deposition (CBD). It was confirmed from the X-ray diffraction (XRD) analysis that CSP films exhibited a polycrystalline nature while amorphous nature was diagnosed for CBD films. Also XRD analysis was utilized to compute grain size, strain and dislocation density. Surface morphology was characterized using scanning electron microscope and photomicroscope images. The optical absorption measurement revealed that the direct allowed electronic transition with band gaps 2.8 eV and 3.0 eV for CBD and CSP methods, respectively. The optical constants, such as extinction coefficient ( k), refractive index ( n), real and imaginary dielectric constants ( ɛ 1, ɛ 2) were discussed. The photoluminescence (PL) spectra of CuAlS2 thin films appeared as a single peak for each of them, and this is attributed to band-to-band transition.

Contribution of a new generation field-emission scanning electron microscope in the understanding of a 2099 Al-Li alloy.

PubMed

Brodusch, Nicolas; Trudeau, Michel; Michaud, Pierre; Rodrigue, Lisa; Boselli, Julien; Gauvin, Raynald

2012-12-01

Aluminum-lithium alloys are widespread in the aerospace industry. The new 2099 and 2199 alloys provide improved properties, but their microstructure and texture are not well known. This article describes how state-of-the-art field-emission scanning electron microscopy (FE-SEM) can contribute to the characterization of the 2099 aluminum-lithium alloy and metallic alloys in general. Investigations were carried out on bulk and thinned samples. Backscattered electron imaging at 3 kV and scanning transmission electron microscope imaging at 30 kV along with highly efficient microanalysis permitted correlation of experimental and expected structures. Although our results confirm previous studies, this work points out possible substitutions of Mg and Zn with Li, Al, and Cu in the T1 precipitates. Zinc and magnesium are also present in "rice grain"-shaped precipitates at the grain boundaries. The versatility of the FE-SEM is highlighted as it provides information in the macro- and microscales with relevant details. Its ability to probe the distribution of precipitates from nano- to microsizes throughout the matrix makes FE-SEM an essential technique for the characterization of metallic alloys.

Charge dynamics in aluminum oxide thin film studied by ultrafast scanning electron microscopy.

PubMed

Zani, Maurizio; Sala, Vittorio; Irde, Gabriele; Pietralunga, Silvia Maria; Manzoni, Cristian; Cerullo, Giulio; Lanzani, Guglielmo; Tagliaferri, Alberto

2018-04-01

The excitation dynamics of defects in insulators plays a central role in a variety of fields from Electronics and Photonics to Quantum computing. We report here a time-resolved measurement of electron dynamics in 100 nm film of aluminum oxide on silicon by Ultrafast Scanning Electron Microscopy (USEM). In our pump-probe setup, an UV femtosecond laser excitation pulse and a delayed picosecond electron probe pulse are spatially overlapped on the sample, triggering Secondary Electrons (SE) emission to the detector. The zero of the pump-probe delay and the time resolution were determined by measuring the dynamics of laser-induced SE contrast on silicon. We observed fast dynamics with components ranging from tens of picoseconds to few nanoseconds, that fits within the timescales typical of the UV color center evolution. The surface sensitivity of SE detection gives to the USEM the potential of applying pump-probe investigations to charge dynamics at surfaces and interfaces of current nano-devices. The present work demonstrates this approach on large gap insulator surfaces. Copyright © 2018 Elsevier B.V. All rights reserved.

Milligram-per-second femtosecond laser production of Se nanoparticle inks and ink-jet printing of nanophotonic 2D-patterns

NASA Astrophysics Data System (ADS)

Ionin, Andrey; Ivanova, Anastasia; Khmel'nitskii, Roman; Klevkov, Yury; Kudryashov, Sergey; Mel'nik, Nikolay; Nastulyavichus, Alena; Rudenko, Andrey; Saraeva, Irina; Smirnov, Nikita; Zayarny, Dmitry; Baranov, Anatoly; Kirilenko, Demid; Brunkov, Pavel; Shakhmin, Alexander

2018-04-01

Milligram-per-second production of selenium nanoparticles in water sols was realized through 7-W, 2 MHz-rate femtosecond laser ablation of a crystalline trigonal selenium pellet. High-yield particle formation mechanism and ultimate mass-removal yield were elucidated by optical profilometry and scanning electron microscopy characterization of the corresponding crater depths and topographies. Deposited selenium particles were inspected by scanning and transmission electron microscopy, while their hydrosols (nanoinks) were characterized by optical transmission, Raman and dynamic light scattering spectroscopy. 2D patterns and coatings were ink-jet printed on thin supported silver films and their bare silica glass substrates, as well as on IR-transparent CaF2 substrates, and characterized by electron microscopy, energy-dispersive x-ray spectroscopy, and broadband (vis-mid IR) transmission spectroscopy, exhibiting crystalline selenium nanoparticles with high refractive index as promising all-dielectric sensing building nanoblocks in nanophotonics.

Imaging and elemental mapping of biological specimens with a dual-EDS dedicated scanning transmission electron microscope

PubMed Central

Wu, J.S.; Kim, A. M.; Bleher, R.; Myers, B.D.; Marvin, R. G.; Inada, H.; Nakamura, K.; Zhang, X.F.; Roth, E.; Li, S.Y.; Woodruff, T. K.; O'Halloran, T. V.; Dravid, Vinayak P.

2013-01-01

A dedicated analytical scanning transmission electron microscope (STEM) with dual energy dispersive spectroscopy (EDS) detectors has been designed for complementary high performance imaging as well as high sensitivity elemental analysis and mapping of biological structures. The performance of this new design, based on a Hitachi HD-2300A model, was evaluated using a variety of biological specimens. With three imaging detectors, both the surface and internal structure of cells can be examined simultaneously. The whole-cell elemental mapping, especially of heavier metal species that have low cross-section for electron energy loss spectroscopy (EELS), can be faithfully obtained. Optimization of STEM imaging conditions is applied to thick sections as well as thin sections of biological cells under low-dose conditions at room- and cryogenic temperatures. Such multimodal capabilities applied to soft/biological structures usher a new era for analytical studies in biological systems. PMID:23500508

Multi-walled carbon nanotubes decorated by platinum catalyst nanoparticles--examination and microanalysis using scanning and transmission electron microscopies.

PubMed

Guinel, M J-F; Brodusch, N; Verde-Gómez, Y; Escobar-Morales, B; Gauvin, R

2013-10-01

Carbon nanotubes (CNTs) decorated with platinum (Pt) nanoparticles (NPs) have been characterized using a cold field-emission scanning electron microscope (SEM) and a high resolution field-emission transmission electron microscope (TEM). With this particular composite material, the complementary nature of the two instruments was demonstrated. Although the long CNTs were found to be mostly bent and defective in some parts, the nucleation of Pt occurred randomly and uniformly covered the CNTs. The NPs displayed a large variation in size, were sometimes defective with twins and stacking faults, and were found to be faceted with the presence of surface steps. The shape and size of the NPs and the presence of defects may have significant consequences on the activity of the Pt catalyst material. Also, thin layers of platinum oxide were identified on the surface of some NPs. © 2013 The Authors Journal of Microscopy © 2013 Royal Microscopical Society.

Pd-Ni-MWCNT nanocomposite thin films: preparation and structure

NASA Astrophysics Data System (ADS)

Kozłowski, Mirosław; Czerwosz, ElŻbieta; Sobczak, Kamil

2017-08-01

The properties of nanocomposite palladium-nickel-multi-walled (Pd-Ni-MWCNT) films deposited on aluminum oxide (Al2O3) substrate have been prepared and investigated. These films were obtained by 3 step process consisted of PVD/CVD/PVD methods. The morphology and structure of the obtained films were characterized by Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) techniques at various stages of the film formation. EDX spectrometer was used to measurements of elements segregation in the obtained film. TEM and STEM (Scanning Transmission Electron Microscopy) observations showed MWCNTs decorated with palladium nanoparticles in the film obtained in the last step of film formation (final PVD process). The average size of the palladium nanoparticles observed both on MWCNTs and carbonaceous matrix does not exceed 5 nm. The research was conducted on the use of the obtained films as potential sensors of gases (e.g. H2, NH3, CO2) and bio-sensors or optical sensors.

Coaxial carbon plasma gun deposition of amorphous carbon films

NASA Technical Reports Server (NTRS)

Sater, D. M.; Gulino, D. A.; Rutledge, S. K.

1984-01-01

A unique plasma gun employing coaxial carbon electrodes was used in an attempt to deposit thin films of amorphous diamond-like carbon. A number of different structural, compositional, and electrical characterization techniques were used to characterize these films. These included scanning electron microscopy, scanning transmission electron microscopy, X ray diffraction and absorption, spectrographic analysis, energy dispersive spectroscopy, and selected area electron diffraction. Optical absorption and electrical resistivity measurements were also performed. The films were determined to be primarily amorphous, with poor adhesion to fused silica substrates. Many inclusions of particulates were found to be present as well. Analysis of these particulates revealed the presence of trace impurities, such as Fe and Cu, which were also found in the graphite electrode material. The electrodes were the source of these impurities. No evidence of diamond-like crystallite structure was found in any of the film samples. Details of the apparatus, experimental procedure, and film characteristics are presented.

Revealing the synergetic effects in Ni nanoparticle-carbon nanotube hybrids by scanning transmission X-ray microscopy and their application in the hydrolysis of ammonia borane

NASA Astrophysics Data System (ADS)

Zhao, Guanqi; Zhong, Jun; Wang, Jian; Sham, Tsun-Kong; Sun, Xuhui; Lee, Shuit-Tong

2015-05-01

The hybrids of carbon nanotubes (CNTs) and the supported Ni nanoparticles (NPs) have been studied by scanning transmission X-ray microscopy (STXM) and tested by the hydrolysis reaction of ammonia borane (AB, NH3BH3). Data clearly showed the existence of a strong interaction between Ni NPs and thin CNTs (C-O-Ni bonds), which favored the tunable (buffer) electronic structure of Ni NPs facilitating the catalytic process. The hydrolysis process of AB confirmed the hypothesis that the hybrids with a strong interfacial interaction would show superior catalytic performance, while the hybrids with a weak interfacial interaction show poor performance. Our results provide a wealth of detailed information regarding the electronic structure of the NP-CNT hybrids and provide guidance towards the rational design of high-performance catalysts for energy applications.The hybrids of carbon nanotubes (CNTs) and the supported Ni nanoparticles (NPs) have been studied by scanning transmission X-ray microscopy (STXM) and tested by the hydrolysis reaction of ammonia borane (AB, NH3BH3). Data clearly showed the existence of a strong interaction between Ni NPs and thin CNTs (C-O-Ni bonds), which favored the tunable (buffer) electronic structure of Ni NPs facilitating the catalytic process. The hydrolysis process of AB confirmed the hypothesis that the hybrids with a strong interfacial interaction would show superior catalytic performance, while the hybrids with a weak interfacial interaction show poor performance. Our results provide a wealth of detailed information regarding the electronic structure of the NP-CNT hybrids and provide guidance towards the rational design of high-performance catalysts for energy applications. Electronic supplementary information (ESI) available: Magnified TEM images, high resolution TEM images and the particle size distributions of the samples, the STXM results of a thick tube at different positions, XPS results, stability test. See DOI: 10.1039/c5nr01168j

Atomic-scale observation of structural and electronic orders in the layered compound α-RuCl3

PubMed Central

Ziatdinov, M.; Banerjee, A.; Maksov, A.; Berlijn, T.; Zhou, W.; Cao, H. B.; Yan, J.-Q.; Bridges, C. A.; Mandrus, D. G.; Nagler, S. E.; Baddorf, A. P.; Kalinin, S. V.

2016-01-01

A pseudospin-1/2 Mott phase on a honeycomb lattice is proposed to host the celebrated two-dimensional Kitaev model which has an elusive quantum spin liquid ground state, and fascinating physics relevant to the development of future templates towards topological quantum bits. Here we report a comprehensive, atomically resolved real-space study by scanning transmission electron and scanning tunnelling microscopies on a novel layered material displaying Kitaev physics, α-RuCl3. Our local crystallography analysis reveals considerable variations in the geometry of the ligand sublattice in thin films of α-RuCl3 that opens a way to realization of a spatially inhomogeneous magnetic ground state at the nanometre length scale. Using scanning tunnelling techniques, we observe the electronic energy gap of ≈0.25 eV and intra-unit cell symmetry breaking of charge distribution in individual α-RuCl3 surface layer. The corresponding charge-ordered pattern has a fine structure associated with two different types of charge disproportionation at Cl-terminated surface. PMID:27941761

Atomic-scale observation of structural and electronic orders in the layered compound α-RuCl3.

PubMed

Ziatdinov, M; Banerjee, A; Maksov, A; Berlijn, T; Zhou, W; Cao, H B; Yan, J-Q; Bridges, C A; Mandrus, D G; Nagler, S E; Baddorf, A P; Kalinin, S V

2016-12-12

A pseudospin-1/2 Mott phase on a honeycomb lattice is proposed to host the celebrated two-dimensional Kitaev model which has an elusive quantum spin liquid ground state, and fascinating physics relevant to the development of future templates towards topological quantum bits. Here we report a comprehensive, atomically resolved real-space study by scanning transmission electron and scanning tunnelling microscopies on a novel layered material displaying Kitaev physics, α-RuCl 3 . Our local crystallography analysis reveals considerable variations in the geometry of the ligand sublattice in thin films of α-RuCl 3 that opens a way to realization of a spatially inhomogeneous magnetic ground state at the nanometre length scale. Using scanning tunnelling techniques, we observe the electronic energy gap of ≈0.25 eV and intra-unit cell symmetry breaking of charge distribution in individual α-RuCl 3 surface layer. The corresponding charge-ordered pattern has a fine structure associated with two different types of charge disproportionation at Cl-terminated surface.

Atomic-scale observation of structural and electronic orders in the layered compound α-RuCl 3

DOE PAGES

Ziatdinov, Maxim A.; Banerjee, Arnab; Maksov, Artem B.; ...

2016-12-12

A pseudospin-1/2 Mott phase on a honeycomb lattice is proposed to host the celebrated two-dimensional Kitaev model which has an elusive quantum spin liquid ground state, and fascinating physics relevant to the development of future templates towards topological quantum bits. Here we report a comprehensive, atomically resolved real-space study by scanning transmission electron and scanning tunnelling microscopies on a novel layered material displaying Kitaev physics, -RuCl3. Our local crystallography analysis reveals considerable variations in the geometry of the ligand sublattice in thin films of -RuCl3 that opens a way to realization of a spatially inhomogeneous magnetic ground state at themore » nanometre length scale. Using scanning tunnelling techniques, we observe the electronic energy gap of 0.25 eV and intra-unit cell symmetry breaking of charge distribution in individual -RuCl3 surface layer. The corresponding charge-ordered pattern has a fine structure associated with two different types of charge disproportionation at Cl-terminated surface.« less

Influence of film thickness and Fe doping on LPG sensing properties of Mn3O4 thin film grown by SILAR method

NASA Astrophysics Data System (ADS)

Belkhedkar, M. R.; Ubale, A. U.

2018-05-01

Nanocrystalline Fe doped and undoped Mn3O4 thin films have been deposited by Successive Ionic Layer Adsorption and Reaction (SILAR) method onto glass substrates using MnCl2 and NaOH as cationic and anionic precursors. The grazing incidence X-ray diffraction (GIXRD) and field emission scanning electron microscopy (FESEM)) have been carried out to analyze structural and surface morphological properties of the films. The LPG sensing performance of Mn3O4thin films have been studied by varying temperature, concentration of LPG, thickness of the film and doping percentage of Fe. The LPG response of the Mn3O4thin films were found to be enhances with film thickness and decreases with increased Fe doping (0 to 8 wt. %) at 573 K temperature.

Structural and spectroscopic analysis of ex-situ annealed RF sputtered aluminium doped zinc oxide thin films

NASA Astrophysics Data System (ADS)

Otieno, Francis; Airo, Mildred; Erasmus, Rudolph M.; Billing, David G.; Quandt, Alexander; Wamwangi, Daniel

2017-08-01

Aluminium doped zinc oxide thin films are prepared by Radio Frequency magnetron sputtering in pure argon atmosphere at 100 W. The structural results reveal good film adhesion on a silicon substrate (001). The thin films were then subjected to heat treatment in a furnace under ambient air. The structural, morphological, and optical properties of the thin films as a function of deposition time and annealing temperatures have been investigated using Grazing incidence X-Ray Diffraction (GIXRD), Atomic Force Microscopy, and Scanning Electronic Microscopy. The photoluminescence properties of the annealed films showed significant changes in the optical properties attributed to mid gap defects. Annealing increases the crystallite size and the roughness of the film. The crystallinity of the films also improved as evident from the Raman and XRD studies.

Effect of pressure-assisted thermal annealing on the optical properties of ZnO thin films.

PubMed

Berger, Danielle; Kubaski, Evaldo Toniolo; Sequinel, Thiago; da Silva, Renata Martins; Tebcherani, Sergio Mazurek; Varela, José Arana

2013-01-01

ZnO thin films were prepared by the polymeric precursor method. The films were deposited on silicon substrates using the spin-coating technique, and were annealed at 330 °C for 32 h under pressure-assisted thermal annealing and under ambient pressure. Their structural and optical properties were characterized, and the phases formed were identified by X-ray diffraction. No secondary phase was detected. The ZnO thin films were also characterized by field-emission scanning electron microscopy, Fourier transform infrared spectroscopy, photoluminescence and ultraviolet emission intensity measurements. The effect of pressure on these thin films modifies the active defects that cause the recombination of deep level states located inside the band gap that emit yellow-green (575 nm) and orange (645 nm) photoluminescence. Copyright © 2012 John Wiley & Sons, Ltd.

Simulated Thin-Film Growth and Imaging

NASA Astrophysics Data System (ADS)

Schillaci, Michael

2001-06-01

Thin-films have become the cornerstone of the electronics, telecommunications, and broadband markets. A list of potential products includes: computer boards and chips, satellites, cell phones, fuel cells, superconductors, flat panel displays, optical waveguides, building and automotive windows, food and beverage plastic containers, metal foils, pipe plating, vision ware, manufacturing equipment and turbine engines. For all of these reasons a basic understanding of the physical processes involved in both growing and imaging thin-films can provide a wonderful research project for advanced undergraduate and first-year graduate students. After producing rudimentary two- and three-dimensional thin-film models incorporating ballsitic deposition and nearest neighbor Coulomb-type interactions, the QM tunneling equations are used to produce simulated scanning tunneling microscope (SSTM) images of the films. A discussion of computational platforms, languages, and software packages that may be used to accomplish similar results is also given.

Investigation on Structural and Optical Properties of Copper Telluride Thin Films with Different Annealing Temperature

NASA Astrophysics Data System (ADS)

Nishanthini, R.; Muthu Menaka, M.; Pandi, P.; Bahavan Palani, P.; Neyvasagam, K.

The copper telluride (Cu2Te) thin film of thickness 240nm was coated on a microscopic glass substrate by thermal evaporation technique. The prepared films were annealed at 150∘C and 250∘C for 1h. The annealing effect on Cu2Te thin films was examined with different characterization methods like X-ray Diffraction Spectroscopy (XRD), Scanning Electron Microscopy (SEM), Ultra Violet-Visible Spectroscopy (UV-VIS) and Photoluminescence (PL) Spectroscopy. The peak intensities of XRD spectra were increased while increasing annealing temperature from 150∘C to 250∘C. The improved crystallinity of the thin films was revealed. However, the prepared films are exposed complex structure with better compatibility. Moreover, the shift in band gap energy towards higher energies (blue shift) with increasing annealing temperature is observed from the optical studies.

Study of organic-inorganic hetero-interfaces and electrical transport in semiconducting nanostructures

NASA Astrophysics Data System (ADS)

Wagner, Sean Robert

As the electronics industry continues to evolve and move towards functional electronic devices with increasing complexity and functionality, it becomes important to explore materials outside the regime of conventional semiconductors. Organic semiconducting small molecules have received a large amount of attention due to their high degree of flexibility, the option to perform molecular synthesis to modify their electronic and magnetic properties, and their ability to organize into highly-ordered functionalized nanostructures and thin films. Being able to form complex nanostructures and thin films with molecular precision, while maintaining the ability to tune properties through modifications in the molecular chemistry could result in vast improvements in conventional device architectures. However, before this is realized, there still remains a significant lack of understanding regarding how these molecules interact with various substrate surfaces as well as their intermolecular interactions. The interplay between these interactions can produce drastic changes in the molecular orientation and ordering at the hetero-interface, which can affect the transport properties of the molecular thin film and ultimately modify the performance of the organic electronic device. This study first focuses on the growth dynamics, molecular ordering, and molecular orientation of metal phthalocyanine (MPc) molecules, particularly on Si, a substrate which is notoriously difficult to form an organized organic thin film on due to the surface dangling bonds. By deactivating these bonds, the formation of a highly ordered organic molecular thin film becomes possible. Combining scanning tunneling microscopy, scanning tunneling spectroscopy, low-energy electron diffraction, and density functional theory calculations, the growth evolution of MPc molecules ( M = Zn, Cu, Co) from the single molecule level to multilayered films on the deactivated Si(111)-B surface is investigated. Initial tests are centered around thermally evaporated ZnPc. These molecules display a highly-ordered, close-packed, tilted configuration which differs from any known bulk packing motif. The ZnPc molecules are able to diffuse rapidly on the Si surface and preferentially nucleate at Si step-edges. This is followed by the formation of highly-ordered anisotropic stripe structures which grow across the Si terraces, i.e. anisotropic step-flow growth. The step-flow growth mode further impacts the growth by reducing the allowed symmetry of the molecular domains such that thin films with an exclusive in-plane molecular ordering are formed. Additionally, the ZnPc tilted packing motif stabilizes the molecular film, allowing it to maintain this packing for multilayered films, despite the decreasing substrate influence. The strength of the MPc-substrate interaction can be modified by changing the central transition-metal ion within the molecule. Through selective p-d orbital coupling between MPc molecules and the substrate, the degree of orbital coupling can induce modifications in the molecular ordering and orientation of MPc molecules at the interface. The secondary focus of this study is to initiate preliminary experimentation towards understanding how ordered organic molecular thin films can be applied to silicon-based devices that could have a significant impact on the electronics market. Si nanomembrane is a flexible, low-dimensional nanomaterial with electronic properties that are highly sensitive to the interface condition. By merging the knowledge of MPc thin film growth on Si with Si nanomembrane technology, possibilities towards modifying the transport properties of nanomaterials through engineering the organic-inorganic hetero-interface can be explored.

Studies of Nano-structured Se77Sb23- x Ge x Thin Films Prepared by Physical Vapor Condensation Technique

NASA Astrophysics Data System (ADS)

Alvi, M. A.

2017-02-01

Bulk Se77Sb23- x Ge x material with x = 4 and 12 was prepared by employing a melt quench technique. Its amorphous as well as glassy nature was confirmed by x-ray diffraction analysis and nonisothermal differential scanning calorimetry measurements. The physical vapor condensation technique was applied to prepare nanostructured thin films of Se77Sb23- x Ge x material. The surface morphology of the films was examined using field-emission scanning electron microscopy, revealing average particle size between 20 nm and 50 nm. Systematic investigation of optical absorption data indicated that the optical transition was indirect in nature. The dark conductivity (dc conductivity) of nano-structured Se77Sb23- x Ge x thin films was also investigated at temperatures from 313 K to 463 K, revealing that it tended to increase with increasing temperature. Analyses of our experimental data also indicate that the conduction is due to thermally supported tunneling of charge carriers in confined states close to the band edges. The calculated values of activation energy agree well with the optical bandgap.

The early growth and interface of YBa 2Cu 3O y thin films deposited on YSZ substrates

NASA Astrophysics Data System (ADS)

Gao, J.; Tang, W. H.; Yau, C. Y.

2001-11-01

Epitaxial thin films of YBa 2Cu 3O y (YBCO) have been prepared on yttrium-stabilized zirconia substrates with and without a buffer layer. The early growth, crystallinity and surface morphology of these thin films have been characterized by X-ray diffraction, rocking curves, scanning electron microscope, in situ conductance measurements, and surface step profiler. The full width at half maximum of the ( 0 0 5 ) peak of rocking curve was found to be less than 0.1°. Over a wide scanning range of 2000 μm the average surface roughness is just 5 nm, indicating very smooth films. Grazing incident X-ray reflection and positron annihilation spectroscopy shows well-defined interfaces between layers and substrate. By applying a new Eu 2CuO 4 (ECO) buffer layer the initial formation of YBCO appears to grow layer-by-layer rather than the typical island growth mode. The obtained results reveal significant improvements at the early formation and crystallinity of YBCO by using the 214-T ‧ ECO as a buffer layer.

Three-Dimensional, Fibrous Lithium Iron Phosphate Structures Deposited by Magnetron Sputtering.

PubMed

Bünting, Aiko; Uhlenbruck, Sven; Sebold, Doris; Buchkremer, H P; Vaßen, R

2015-10-14

Crystalline, three-dimensional (3D) structured lithium iron phosphate (LiFePO4) thin films with additional carbon are fabricated by a radio frequency (RF) magnetron-sputtering process in a single step. The 3D structured thin films are obtained at deposition temperatures of 600 °C and deposition times longer than 60 min by using a conventional sputtering setup. In contrast to glancing angle deposition (GLAD) techniques, no tilting of the substrate is required. Thin films are characterized by X-ray diffraction (XRD), Raman spectrospcopy, scanning electron microscopy (SEM), cyclic voltammetry (CV), and galvanostatic charging and discharging. The structured LiFePO4+C thin films consist of fibers that grow perpendicular to the substrate surface. The fibers have diameters up to 500 nm and crystallize in the desired olivine structure. The 3D structured thin films have superior electrochemical properties compared with dense two-dimensional (2D) LiFePO4 thin films and are, hence, very promising for application in 3D microbatteries.

Estimating pore and cement volumes in thin section

USGS Publications Warehouse

Halley, R.B.

1978-01-01

Point count estimates of pore, grain and cement volumes from thin sections are inaccurate, often by more than 100 percent, even though they may be surprisingly precise (reproducibility + or - 3 percent). Errors are produced by: 1) inclusion of submicroscopic pore space within solid volume and 2) edge effects caused by grain curvature within a 30-micron thick thin section. Submicroscopic porosity may be measured by various physical tests or may be visually estimated from scanning electron micrographs. Edge error takes the form of an envelope around grains and increases with decreasing grain size and sorting, increasing grain irregularity and tighter grain packing. Cements are greatly involved in edge error because of their position at grain peripheries and their generally small grain size. Edge error is minimized by methods which reduce the thickness of the sample viewed during point counting. Methods which effectively reduce thickness include use of ultra-thin thin sections or acetate peels, point counting in reflected light, or carefully focusing and counting on the upper surface of the thin section.

Morphological, elemental, and optical characterization of plasma polymerized n-butyl methacrylate thin films

NASA Astrophysics Data System (ADS)

Nasrin, Rahima; Hossain, Khandker S.; Bhuiyan, A. H.

2018-05-01

Plasma polymerized n-butyl methacrylate (PPnBMA) thin films of varying thicknesses were prepared at room temperature by AC plasma polymerization system using a capacitively coupled parallel plate reactor. Field-emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), energy-dispersive X-ray (EDX) analysis, and ultraviolet-visible (UV-Vis) spectroscopic investigation have been performed to study the morphological, elemental, and optical properties of the PPnBMA thin films, respectively. The flat and defect-free nature of thin films were confirmed by FESEM and AFM images. With declining plasma power, average roughness and root mean square roughness increase. Allowed direct transition ( E gd) and indirect transition ( E gi) energy gaps were found to be 3.64-3.80 and 3.38-3.45 eV, respectively, for PPnBMA thin films of different thicknesses. Values of E gd as well as E gi increase with the increase of thickness. The extinction coefficient, Urbach energy, and steepness parameter were also determined for these thin films.

Electrical characterization of MIM capacitor comprises an adamantane film at room temperature

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tiwari, Rajanish N., E-mail: rajanisht@gmail.com; Toyota Technological Institute, 2-12-1Hisakata, Tempaku-Ku, Nagoya 468-8511; Yoshimura, Masamichi

2016-06-15

We fabricated a new metal-insulator-metal capacitor at room temperature, comprising a ∼90 nm thin low–k adamantane film on a Si substrate. The surface morphology of deposited organic film was investigated by using scanning electron microscopy and Raman spectroscopy, which is confirmed that the adamantane thin film was uniformly distributed on the Si surface. The adamantane film exhibits a low leakage current density of 7.4 x 10{sup −7} A/cm{sup 2} at 13.5 V, better capacitance density of 2.14 fF/μm{sup 2} at 100 KHz.

ZrO{sub 2}-ZnO composite thin films for humidity sensing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Velumani, M., E-mail: velumanimohan@gmail.com; Sivacoumar, R.; Alex, Z. C.

2016-05-23

ZrO{sub 2}-ZnO composite thin films were grown by reactive DC magnetron sputtering. X-ray diffraction studies reveal the composite nature of the films with separate ZnO and ZrO{sub 2} phase. Scanning electron microscopy studies confirm the nanocrystalline structure of the films. The films were studied for their impedometric relative humidity (RH) sensing characteristics. The complex impedance plot was fitted with a standard equivalent circuit consisting of an inter-granular resistance and a capacitance in parallel. The DC resistance was found to be decreasing with increase in RH.

Stacking the Deck: Leveraging Surface Interactions to Tune Interfacial Electronic Structure

NASA Astrophysics Data System (ADS)

Maughan, Bret; Eads, Calley; Zahl, Percy; Sutter, Peter; Monti, Oliver

We present results from a series of experiments aimed at understanding and controlling molecular interactions in phthalocyanine (Pc) thin-films on Cu(110) to tailor the interfacial electronic structure. Using low-temperature scanning tunneling microscopy (LT-STM), we identify interactions that drive surface-molecule coupling, molecular self-assembly and thin-film order. We provide evidence that interactions with native Cu adatoms play a pivotal role in self-assembly of Pc systems, along with anisotropic nanoribbon growth dynamics, supported by an agent-based kinetic Monte Carlo (AB-KMC) simulation. We show further that self-assembled nanoribbon length can be controlled using surface diffusion barriers and that ordered 2D thin-film growth is promoted by diminishing surface-molecule interactions that otherwise dominate native Cu(110) interfaces. Altogether, this detailed structural understanding allows us to interpret interfacial electronic structure and dynamics, uncovered through ultraviolet (UPS) and two-photon photoemission (2PPE) spectroscopy experiments, in molecular configuration-specific detail. In all, our understanding of interfacial processes guides strategic modifications to both surface and molecule to harness interfacial interactions and thereby modify the collective electronic structure of the interface. NSF No. CHE-1213243 and No. CHE-1565497, Arizona TRIF, DOE/BNL Cntrct No. DE-SC0012704, and DOE No. DE-SC0016343.

Stabilization of Hydrogen Production via Methanol Steam Reforming in Microreactor by Al2O3 Nano-Film Enhanced Catalyst Adhesion.

PubMed

Jeong, Heondo; Na, Jeong-Geol; Jang, Min Su; Ko, Chang Hyun

2016-05-01

In hydrogen production by methanol steam reforming reaction with microchannel reactor, Al2O3 thin film formed by atomic layer deposition (ALD) was introduced on the surface of microchannel reactor prior to the coating of catalyst particles. Methanol conversion rate and hydrogen production rate, increased in the presence of Al2O3 thin film. Over-view and cross-sectional scanning electron microscopy study showed that the adhesion between catalyst particles and the surface of microchannel reactor enhanced due to the presence of Al2O3 thin film. The improvement of hydrogen production rate inside the channels of microreactor mainly came from the stable fixation of catalyst particles on the surface of microchannels.

Biopolymer Green Lubricant for Sustainable Manufacturing

PubMed Central

Shi, Shih-Chen; Lu, Fu-I

2016-01-01

We report on the preparation of a biopolymer thin film by hydroxypropyl methylcellulose (HPMC), which can be used as a dry green lubricant in sustainable manufacturing. The thin films were characterized through scanning electron microscopy, energy-dispersive spectroscopy, and Raman spectroscopy; the films showed desirable levels of thickness, controllability, and uniformity. Tribology tests also showed desirable tribological and antiwear behaviors, caused by the formation of transfer layers. Zebrafish embryo toxicity studies showed that HPMC has excellent solubility and biocompatibility, which may show outstanding potential for applications as a green lubricant. The results of the present study show that these techniques for biopolymer HPMC provide an ecologically responsible and convenient method for preparing functional thin films, which is particularly applicable to sustainable manufacturing. PMID:28773462

Silicon thin film homoepitaxy by rapid thermal atmospheric-pressure chemical vapor deposition (RT-APCVD)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Monna, R.; Angermeier, D.; Slaoui, A.

1996-12-01

The homoepitaxy of thin film silicon layers in a horizontal, atmospheric pressure RTCVD reactor is reported. The experiments were conducted in a temperature range from 900 C to 1,300 C employing the precursor trichlorosilane (TCS) and the dopant trichloroborine (TCB) diluted in hydrogen. The epilayers were evaluated by Nomarski microscopy, Rutherford backscattering spectroscopy, and scanning electron microscopy (SEM). The electrical properties of the thin film were analyzed by sheet resistance and four point probe characterization methods. The authors propose that the responsible mechanisms for the observed growth decline at higher precursor concentration in hydrogen are due to the reaction ofmore » the gaseous HCl with the silicon surface and the supersaturation of silicon.« less

Self-Organized Formation of Short TiO2 Nanotube Arrays By Complete Anodization of Ti Thin Films

NASA Astrophysics Data System (ADS)

Okada, Masahisa; Tajima, Kazuki; Yamada, Yasusei; Yoshimura, Kazuki

We investigate the self-organized growth of short TiO2 nanotubes by complete anodization of Ti thin films deposited on Si substrates in ethylene glycol electrolytes with small addition of NH4F. During the anodization process, real-time inspection of the current transient is performed to anodize the Ti films completely. X-ray photoelectron spectroscopy and scanning electron microscopy are employed to characterize the resulting samples. We find that the length of the formed TiO2 nanotubes is governed by the thickness of Ti thin films independently of the tube diameter. Short TiO2 nanotubes are also found to be stable up to 550 °C in air atmosphere even after crystallization to rutile.

Synthesis of TiN/a-Si3N4 thin film by using a Mather type dense plasma focus system

NASA Astrophysics Data System (ADS)

Hussain, T.; R., Ahmad; Khalid, N.; A. Umar, Z.; Hussnain, A.

2013-05-01

A 2.3 kJ Mather type pulsed plasma focus device was used for the synthesis of a TiN/a-Si3N4 thin film at room temperature. The film was characterized using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and atomic force microscopy (AFM). The XRD pattern confirms the growth of polycrystalline TiN thin film. The XPS results indicate that the synthesized film is non-stoichiometric and contains titanium nitride, silicon nitride, and a phase of silicon oxy-nitride. The SEM and AFM results reveal that the surface of the synthesized film is quite smooth with 0.59 nm roughness (root-mean-square).

In-depth evolution of chemical states and sub-10-nm-resolution crystal orientation mapping of nanograins in Ti(5 nm)/Au(20 nm)/Cr(3 nm) tri-layer thin films

NASA Astrophysics Data System (ADS)

Zhu, Xiaoli; Todeschini, Matteo; Bastos da Silva Fanta, Alice; Liu, Lintao; Jensen, Flemming; Hübner, Jörg; Jansen, Henri; Han, Anpan; Shi, Peixiong; Ming, Anjie; Xie, Changqing

2018-09-01

The applications of Au thin films and their adhesion layers often suffer from a lack of sufficient information about the chemical states of adhesion layers and about the high-lateral-resolution crystallographic morphology of Au nanograins. Here, we demonstrate the in-depth evolution of the chemical states of adhesive layers at the interfaces and the crystal orientation mapping of gold nanograins with a lateral resolution of less than 10 nm in a Ti/Au/Cr tri-layer thin film system. Using transmission electron microscopy, the variation in the interdiffusion at Cr/Au and Ti/Au interfaces was confirmed. From X-ray photoelectron spectroscopy (XPS) depth profiling, the chemical states of Cr, Au and Ti were characterized layer by layer, suggesting the insufficient oxidation of the adhesive layers. At the interfaces the Au 4f peaks shift to higher binding energies and this behavior can be described by a proposed model based on electron reorganization and substrate-induced final-state neutralization in small Au clusters supported by the partially oxidized Ti layer. Utilizing transmission Kikuchi diffraction (TKD) in a scanning electron microscope, the crystal orientation of Au nanograins between two adhesion layers was non-destructively characterized with sub-10 nm spatial resolution. The results provide nanoscale insights into the Ti/Au/Cr thin film system and contribute to our understanding of its behavior in nano-optic and nano-electronic devices.

Structure Study of Magnetic Thin Films for Voltage Controlled Spintronics by Scanning Transmission Electron Microscopy Experiment and Density Functional Theory Calculations

NASA Astrophysics Data System (ADS)

Sun, Congli

We have studied magnetic thin films for voltage controlled magnetic tunnel junctions (MTJs) by advanced scanning transmission electron microscopy (STEM) and density functional theory (DFT) simulations. MTJs are the prototypical spintronic device and manipulation of magnetism by electrical means is among the most promising approaches to novel voltage-controlled spin electronics. The voltage controlled magnetic effect can be achieved across many different materials systems, all of which depend on high-quality thin films with minimum crystallographic defects. Cr2O3 is antiferromagnetic in bulk but ferromagnetic on the (0001) surface. Bulk Cr2O3 has two degenerate antiferromagnetic states with opposite (0001) surface spin polarization. As Cr2O3 is also magnetoelectric, the degenerate antiferromagnetic states can be lifted by manipulating the free-energy gain DeltaF = aEH. Therefore, the surface ferromagnetism can be controlled by applied electric field. We have observed vertical grain boundaries in Cr2O 3/Al2O3 systems that are related with a 60° in-plane rotation by diffraction contrast TEM image. STEM as a function of scattering angle points out a simultaneous ⅓[101¯0] basal plane shift. Local boundary electron energy loss spectroscopy (EELS) shows a pre-peak on the O K-edge, indicating a reduced bandgap along the boundary that provides potential breakdown paths in Cr2O3 thin films. B doping of Cr2O3 is known to increase the Neel temperature. B was found to form either BCr4 tetrahedra or BO 3 triangles in the Cr2O3 lattice, with sigma * and pi* bonds exhibiting different energy loss features. Modeling the experimental spectra as a linear combination of simulated B K edges reproduces the experimental pi* / sigma * ratios for 12 to 43 % of the B in the sample occupying BCr 4 sites. Simulated BCr4 fraction / total B as a function of oxygen partial pressures supports the EELS results and indicates further increase of Neel temperature can be achieved by optimizing oxygen partial pressures.

Effect of thickness on physical properties of electron beam vacuum evaporated CdZnTe thin films for tandem solar cells

NASA Astrophysics Data System (ADS)

Chander, Subhash; Dhaka, M. S.

2016-10-01

The thickness and physical properties of electron beam vacuum evaporated CdZnTe thin films have been optimized in the present work. The films of thickness 300 nm and 400 nm were deposited on ITO coated glass substrates and subjected to different characterization tools like X-ray diffraction (XRD), UV-Vis spectrophotometer, source meter and scanning electron microscopy (SEM) to investigate the structural, optical, electrical and surface morphological properties respectively. The XRD results show that the as-deposited CdZnTe thin films have zinc blende cubic structure and polycrystalline in nature with preferred orientation (111). Different structural parameters are also evaluated and discussed. The optical study reveals that the optical transition is found to be direct and energy band gap is decreased for higher thickness. The transmittance is found to increase with thickness and red shift observed which is suitable for CdZnTe films as an absorber layer in tandem solar cells. The current-voltage characteristics of deposited films show linear behavior in both forward and reverse directions as well as the conductivity is increased for higher film thickness. The SEM studies show that the as-deposited CdZnTe thin films are found to be homogeneous, uniform, small circle-shaped grains and free from crystal defects. The experimental results confirm that the film thickness plays an important role to optimize the physical properties of CdZnTe thin films for tandem solar cell applications as an absorber layer.

The effects of viscoelastic polymer substrates on adult stem cell differentiation

NASA Astrophysics Data System (ADS)

Chang, Chungchueh; Fields, Adam; Ramek, Alex; Jurukovski, Vladimir; Simon, Marcia; Rafailovich, Miriam

2009-03-01

Dental Pulp Stem Cells (DPSCs) are known to differentiate in either bone, dentine, or nerve tissue by different environment signals. In this study, we have determined whether differentiation could only through modification of the substrate mechanics. Atomic Force Microscopy (AFM) on Shear Modulation Force Microscopy (SMFM) mode indicated that the spun-cast polybutadiene (PB) thin films could be used to provide different stiffness substrates by changing the thicknesses of thin films. DPSCs were then plated on these substrates and cultured in standard media. After 28 days incubation, Lasar Scanning Confocal Microscopy (LSCM) with mercury lamp indicated that the crystals were observed only on hard surfaces. The Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray analysis (EDX analysis) indicated that the crystals are calcium phosphates. The Glancing Incidence Diffraction (GID) was also used to determine the structure of crystals. These results indicate that DPSCs could be differentiated into osteoblasts by mechanical stimuli from substrate mechanics.

Stoichiometric control for heteroepitaxial growth of smooth ɛ-Ga2O3 thin films on c-plane AlN templates by mist chemical vapor deposition

NASA Astrophysics Data System (ADS)

Tahara, Daisuke; Nishinaka, Hiroyuki; Morimoto, Shota; Yoshimoto, Masahiro

2017-07-01

Epitaxial ɛ-Ga2O3 thin films with smooth surfaces were successfully grown on c-plane AlN templates by mist chemical vapor deposition. Using X-ray diffraction 2θ-ω and φ scans, the out-of-plane and in-plane epitaxial relationship was determined to be (0001) ɛ-Ga2O3 [10\\bar{1}0] ∥ (0001)AlN[10\\bar{1}0]. The gallium/oxygen ratio was controlled by varying the gallium precursor concentration in the solution. While scanning electron microscopy showed the presence of large grains on the surfaces of the films formed for low concentrations of oxygen species, no large grains were observed under stoichiometric conditions. Cathodoluminescence measurements showed a deep-level emission ranging from 1.55-3.7 eV; however, no band-edge emission was observed.

Growth, Structural, Electronic, and Magnetic Characterization of GaN, CrN, Fe Islands on CrN, and Fe/CrN Bilayer Thin Films

NASA Astrophysics Data System (ADS)

Alam, Khan

As a part of my Ph.D research, initially I was involved in construction and calibration of an ultra-high vacuum thin film facility, and later on I studied structural, electronic, and magnetic properties of GaN, CrN, Fe/CrN bilayers, and Fe islands on CrN thin films. All of these films were grown by molecular beam epitaxy and characterized with a variety of state-of-the-art techniques including variable temperature reflection high energy electron diffraction, low temperature scanning tunneling microscopy and spectroscopy, variable temperature vibrating sample magnetometry, variable temperature neutron diffraction and reflectometry, variable temperature x-ray diffraction, x-ray reflectometry, Rutherford backscattering, Auger electron spectroscopy, and cross-sectional tunneling electron microscopy. The experimental results are furthermore understood by comparing with numerical calculations using generalized gradient approximation, local density approximation with Hubbard correction, Refl1D, and data analysis and visual environment program. In my first research project, I studied Ga gas adatoms on GaN surfaces. We discovered frozen-out gallium gas adatoms on atomically smooth c(6x12) GaN(0001¯) surface using low temperature scanning tunneling microscopy. We identified adsorption sites of the Ga adatoms on c(6x12) reconstructed surface. Their bonding is determined by measuring low unoccupied molecular orbital level. Absorption sites of the Ga gas adatoms on centered 6x12 are identified, and their asymmetric absorption on the chiral domains is investigated. In second project, I investigated magneto-structural phase transition in chromium nitride (CrN) thin films. The CrN thin films are grown by molecular beam epitaxy. Structural and magnetic transition are studied using variable temperature reflection high energy electron diffraction and variable temperature neutron diffraction. We observed a structural phase transition at the surface at 277+/-2 K, and a sharp, first-order magnetic phase transition from paramagnetic (room temperature) to antiferromagnetic (low temperature) at 280+/-3 K. Our experiments suggest that the structural transition in CrN thin films occur in out-of-plane direction, and epitaxial constraints suppress the in-plane transition; therefore, the low temperature crystal structure of CrN is tetragonal. This new model explains our structural and magnetic data at low temperatures, but it is different than the previously published orthorhombic model. In third project, I studied exchange bias and exchange spring effect in MBE grown Fe/CrN bilayer thin films. We grew Fe/CrN bilayer thin films on MgO(001) substrate by molecular beam epitaxy, and studied them using variable temperature vibrating sample magnetometry, polarized neutron reflectometry, x-ray reflectivity, and cross-sectional transmission electron microscopy. We observed exchange bias and exchange spring effect in all bilayer thin films. We studied the relationship of exchange bias, blocking temperature, and coercivity with Fe and CrN layers thicknesses. We used polarized neutron beam reflectometry to see if spins at Fe/CrN interface are pinned. We found a thin ferromagnetically ordered CrN layer at the interface. In my final project, I studied growth of submonolayer Fe islands on CrN thin films. These films are prepared in two stages: first, a CrN layer is grown by MBE and then a submonolayer Fe is deposited at room temperature from a carefully degassed e-beam evaporator. The films are studied at liquid helium temperature using low temperature scanning tunneling microscopy and spectroscopy. Islands are seen in STM images, after the Fe deposition, at the edges as well as at the center of atomically flat CrN terraces. However, numerical calculations performed by our collaborator Ponce-P'erez from Benem'erita Universidad Aut'onoma de Puebla show that the Fe islands are energetically unstable on the surface. The Fe atoms substitute Cr atoms in the surface layer and the Cr atoms comes out and form islands. In order to find out elemental composition of the islands, we attempted to map local density of state by measuring differential conductance spectra as a function of bias voltage using LT-STS. We observed three characteristically different spectra; one in the CrN substrate and two in the islands. The CrN substrate curve has a "U" shape near Fermi level and a peak at ≈ 105 mV. The islands spectra show Kondo-like resonances at Fermi level; some islands produce a peak whereas others produce a dip the dI/dV curves near Fermi level. Further investigations are needed to determine the origin of the peak and dip in the island curves, as well as to find the composition of the islands.

Thickness dependent structural, optical and electrical properties of Se85In12Bi3 nanochalcogenide thin films

NASA Astrophysics Data System (ADS)

Tripathi, Ravi P.; Zulfequar, M.; Khan, Shamshad A.

2018-04-01

Our aim is to study the thickness dependent effects on structure, electrical and optical properties of Se85In12Bi3 nanochalcogenide thin films. Bulk alloy of Se85In12Bi3 was synthesized by melt-quenching technique. The amorphous as well as glassy nature of Se85In12Bi3 chalcogenide was confirmed by non-isothermal Differential Scanning Calorimetry (DSC) measurements. The nanochalcogenide thin films of thickness 30, 60 and 90 nm were prepared on glass/Si wafer substrate using Physical Vapour Condensation Technique (PVCT). From XRD studies it was found that thin films have amorphous texture. The surface morphology and particle size of films were studied by Field Emission Scanning Electron Microscope (FESEM). From optical studies, different optical parameters were estimated for Se85In12Bi3 thin films at different thickness. It was found that the absorption coefficient (α) and extinction coefficient (k) increases with photon energy and decreases with film thickness. The optical absorption process followed the rule of indirect transitions and optical band gap were found to be increase with film thickness. The value of Urbach energy (Et) and steepness parameter (σ) were also calculated for different film thickness. For electrical studies, dc-conductivity measurement was done at different temperature and activation energy (ΔEc) were determined and found to be increase with film thickness.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cooper, R. C.; Bruno, Giovanni; Onel, Yener

Microstructural changes in porous cordierite caused by machining were characterized using microtensile testing, X-ray computed tomography and scanning electron microscopy. Young s moduli and Poisson s ratios were determined on ~215-380 um thick machined samples by combining digital image correlation and microtensile loading. The results provide evidence for an increase in microcrack density due to machining of the thin samples extracted from diesel particulate filter honeycombs.

Subatomic electronic feature from dynamic motion of Si dimer defects in Bi nanolines on Si(001)

NASA Astrophysics Data System (ADS)

Kirkham, C. J.; Longobardi, M.; Köster, S. A.; Renner, Ch.; Bowler, D. R.

2017-08-01

Scanning tunneling microscopy (STM) reveals unusual sharp features in otherwise defect-free Bi nanolines self-assembled on Si(001). They appear as subatomic thin lines perpendicular to the Bi nanoline at positive biases and as atomic size beads at negative biases. Density functional theory (DFT) simulations show that these features can be attributed to buckled Si dimers substituting for Bi dimers in the nanoline, where the sharp feature is the counterintuitive signature of these dimers flipping during scanning. The perfect correspondence between the STM data and the DFT simulation demonstrated in this paper highlights the detailed understanding we have of the complex Bi-Si(001) Haiku system. This discovery has applications in the patterning of Si dangling bonds for nanoscale electronics.

The Evolution of Fabricated Gold Thin Films to Nano-Micro Particles Under Thermal Annealing Process

NASA Astrophysics Data System (ADS)

Hajivaliei, Mahdi; Nazari, Saeed

2016-06-01

Gold (Au) thin films with thickness of 35nm were prepared by electron beam deposition onto flat glass substrates under high vacuum (5.3×10-3Pa) condition and they were annealed in the range of 573-873 K for 1 and 2h in atmospheric pressure. The influence of the annealing temperature on the evolution of Au thin film to nano-micro particles was studied. Moreover, the basic properties of the films, namely morphological, structural and optical were investigated. The X-ray diffraction (XRD) analysis revealed that the Au thin films were cubic structure phase with lattice parameter around a=4.0786Å. The most preferential orientation is along (111) planes for all Au films. The lattice parameter and grain size in the films were calculated by X-ray patterns and correlated with annealing temperatures. The obtained results of ultraviolet-visible spectrometry (UV-Vis) indicate that with increasing annealing temperature, the surface plasmon resonance peak of gold nanocrystallite will disappear which implies the size of particles are grown. Field-emission scanning electron microscopy (FE-SEM) results show that the prepared gold thin films have been converted to nano-micro gold particles in different annealing temperatures. These results lead to controlling the size of produced nanocrystallite.

Atomic structures of B20 FeGe thin films grown on the Si(111) surface

NASA Astrophysics Data System (ADS)

Kim, Wondong; Noh, Seungkyun; Yoon, Jisoo; Kim, Young Heon; Lee, Inho; Kim, Jae-Sung; Hwang, Chanyong

We investigated the growth and atomic structures of FeGe thin films on the Si (111) surface by using scanning tunneling microscopy (STM) and transmission electron microscopy (TEM). The 2 5nm- thick FeGe thin films were prepared on the clean Si(111) 7x7 surface by co-deposition of Fe and Ge from separated electron-beam evaporators. With direct deposition on the substrate at the temperature above 550 K, the surface of FeGe films was not smooth and consisted of coarse grains. By the combination of room-temperature annealing and post-annealing process around 800 K, the structure of FeGe thin films evolved into the well crystalized structures. Atom-resolved STM images revealed that there are at least four different surface terminations. We constructed atomic models for each surface terminations based on the bulk atomic arrangement of a B20 chiral structure and confirmed that the observed STM images are successfully reproduced by using computational simulations employing Vienna Ab Initio Simulation package (VASP) with a B20 chiral structure model. TEM cross-sectional images also support our atomic models by revealing clearly the characteristic zigzag features of B20 structures of FeGe(111) thin films.

FIB-SEM tomography in biology.

PubMed

Kizilyaprak, Caroline; Bittermann, Anne Greet; Daraspe, Jean; Humbel, Bruno M

2014-01-01

Three-dimensional information is much easier to understand than a set of two-dimensional images. Therefore a layman is thrilled by the pseudo-3D image taken in a scanning electron microscope (SEM) while, when seeing a transmission electron micrograph, his imagination is challenged. First approaches to gain insight in the third dimension were to make serial microtome sections of a region of interest (ROI) and then building a model of the object. Serial microtome sectioning is a tedious and skill-demanding work and therefore seldom done. In the last two decades with the increase of computer power, sophisticated display options, and the development of new instruments, an SEM with a built-in microtome as well as a focused ion beam scanning electron microscope (FIB-SEM), serial sectioning, and 3D analysis has become far easier and faster.Due to the relief like topology of the microtome trimmed block face of resin-embedded tissue, the ROI can be searched in the secondary electron mode, and at the selected spot, the ROI is prepared with the ion beam for 3D analysis. For FIB-SEM tomography, a thin slice is removed with the ion beam and the newly exposed face is imaged with the electron beam, usually by recording the backscattered electrons. The process, also called "slice and view," is repeated until the desired volume is imaged.As FIB-SEM allows 3D imaging of biological fine structure at high resolution of only small volumes, it is crucial to perform slice and view at carefully selected spots. Finding the region of interest is therefore a prerequisite for meaningful imaging. Thin layer plastification of biofilms offers direct access to the original sample surface and allows the selection of an ROI for site-specific FIB-SEM tomography just by its pronounced topographic features.

Three-dimensional reconstruction of root cells and interdental cells in the rat inner ear by serial section scanning electron microscopy.

PubMed

Shodo, Ryusuke; Hayatsu, Manabu; Koga, Daisuke; Horii, Arata; Ushiki, Tatsuo

2017-01-01

In the cochlea, a high K + environment in the endolymph is essential for the maintenance of normal hearing function, and the transport of K + ions through gap junctions of the cochlear epithelium is thought to play an important role in endolymphatic homeostasis. The aim of the present study was to demonstrate the three-dimensional (3D) ultrastructure of spiral ligament root cells and interdental cells, which are located at both ends of the gap junction system of the cochlea epithelium. Serial semi-thin sections of plastic-embedded rat cochlea were mounted on glass slides, stained with uranyl acetate and lead citrate, and observed by scanning electron microscopy (SEM) using the backscattered electron (BSE) mode. 3D reconstruction of BSE images of serial sections revealed that the root cells were linked together to form a branched structure like an elaborate "tree root" in the spiral ligament. The interdental cells were also connected to each other, forming a comb-shaped cellular network with a number of cellular strands in the spiral limbus. Furthermore, TEM studies of ultra-thin sections revealed the rich presence of gap junctions in both root cells and interdental cells. These findings suggest the possibility that both root cells and interdental cells contribute to K + circulation as the end portion of the epithelial cell gap junction system of the cochlea.

Characterization and manipulation of individual defects in insulating hexagonal boron nitride using scanning tunnelling microscopy.

PubMed

Wong, Dillon; Velasco, Jairo; Ju, Long; Lee, Juwon; Kahn, Salman; Tsai, Hsin-Zon; Germany, Chad; Taniguchi, Takashi; Watanabe, Kenji; Zettl, Alex; Wang, Feng; Crommie, Michael F

2015-11-01

Defects play a key role in determining the properties and technological applications of nanoscale materials and, because they tend to be highly localized, characterizing them at the single-defect level is of particular importance. Scanning tunnelling microscopy has long been used to image the electronic structure of individual point defects in conductors, semiconductors and ultrathin films, but such single-defect electronic characterization remains an elusive goal for intrinsic bulk insulators. Here, we show that individual native defects in an intrinsic bulk hexagonal boron nitride insulator can be characterized and manipulated using a scanning tunnelling microscope. This would typically be impossible due to the lack of a conducting drain path for electrical current. We overcome this problem by using a graphene/boron nitride heterostructure, which exploits the atomically thin nature of graphene to allow the visualization of defect phenomena in the underlying bulk boron nitride. We observe three different defect structures that we attribute to defects within the bulk insulating boron nitride. Using scanning tunnelling spectroscopy we obtain charge and energy-level information for these boron nitride defect structures. We also show that it is possible to manipulate the defects through voltage pulses applied to the scanning tunnelling microscope tip.

Correlative fluorescence microscopy and scanning transmission electron microscopy of quantum-dot-labeled proteins in whole cells in liquid.

PubMed

Dukes, Madeline J; Peckys, Diana B; de Jonge, Niels

2010-07-27

Correlative fluorescence microscopy and transmission electron microscopy (TEM) is a state-of-the-art microscopy methodology to study cellular function, combining the functionality of light microscopy with the high resolution of electron microscopy. However, this technique involves complex sample preparation procedures due to its need for either thin sections or frozen samples for TEM imaging. Here, we introduce a novel correlative approach capable of imaging whole eukaryotic cells in liquid with fluorescence microscopy and with scanning transmission electron microscopy (STEM); there is no additional sample preparation necessary for the electron microscopy. Quantum dots (QDs) were bound to epidermal growth factor (EGF) receptors of COS7 fibroblast cells. Fixed whole cells in saline water were imaged with fluorescence microscopy and subsequently with STEM. The STEM images were correlated with fluorescence images of the same cellular regions. QDs of dimensions 7x12 nm were visible in a 5 microm thick layer of saline water, consistent with calculations. A spatial resolution of 3 nm was achieved on the QDs.

Scanning transmission electron microscopy and its application to the study of nanoparticles and nanoparticle systems.

PubMed

Liu, Jingyue

2005-06-01

Scanning transmission electron microscopy (STEM) techniques can provide imaging, diffraction and spectroscopic information, either simultaneously or in a serial manner, of the specimen with an atomic or a sub-nanometer spatial resolution. High-resolution STEM imaging, when combined with nanodiffraction, atomic resolution electron energy-loss spectroscopy and nanometer resolution X-ray energy dispersive spectroscopy techniques, is critical to the fundamental studies of importance to nanoscience and nanotechnology. The availability of sub-nanometer or sub-angstrom electron probes in a STEM instrument, due to the use of a field emission gun and aberration correctors, ensures the greatest capabilities for studies of sizes, shapes, defects, crystal and surface structures, and compositions and electronic states of nanometer-size regions of thin films, nanoparticles and nanoparticle systems. The various imaging, diffraction and spectroscopy modes available in a dedicated STEM or a field emission TEM/STEM instrument are reviewed and the application of these techniques to the study of nanoparticles and nanostructured catalysts is used as an example to illustrate the critical role of the various STEM techniques in nanotechnology and nanoscience research.

Electronic properties of epitaxial silicene: a LT-STM/STS study

NASA Astrophysics Data System (ADS)

Fleurence, Antoine; Lee, Chi-Cheng; Ozaki, Taisuke; Yamada-Takamura, Yukiko; Yoshida, Yasuo; Hasegawa, Yukio

2013-03-01

The astonishing properties of silicene, the Si-counterpart of graphene, together with pioneering experimental observations, triggered in the very recent years, an exponentially increasing interest for this atom-thick material, both at fundamental level and for applications in high-speed electronic devices. We demonstrated, that the spontaneous segregation of silicon on (0001) surface of zirconium diboride (ZrB2) thin films epitaxied on Si(111) wafers gives rise to a wide-scale uniform two-dimensional silicene sheet. The silicene nature of the honeycomb structure imaged by scanning tunneling microscopy is evidenced by the observation of gap-opened π-electronic bands. The band gap opening is primarily due the specifically imprinted buckling. Here, we present the results of a low-temperature scanning tunneling spectroscopy investigation, which evidences the n-doped nature of silicene. The mapping of the local density of states, together with density functional theory give precious insights into the microscopic origin of the electronic bands of silicene. In particular, it shows the correlation between the degree of sp2 hybridization of different Si atoms in the internal structure and the character of the electronic bands.

Correlative Fluorescence Microscopy and Scanning Transmission Electron Microscopy of Quantum Dot Labeled Proteins in Whole Cells in Liquid

PubMed Central

Dukes, Madeline J.; Peckys, Diana B.; de Jonge, Niels

2010-01-01

Correlative fluorescence microscopy and transmission electron microscopy (TEM) is a state-of-the-art microscopy methodology to study cellular function, combining the functionality of light microscopy with the high resolution of electron microscopy. However, this technique involves complex sample preparation procedures due to its need for either thin sections or frozen samples for TEM imaging. Here, we introduce a novel correlative approach capable of imaging whole eukaryotic cells in liquid with fluorescence microscopy and with scanning transmission electron microscopy (STEM); there is no additional sample preparation necessary for the electron microscopy. Quantum dots (QDs) were bound to epidermal growth factor (EGF) receptors of COS7 fibroblast cells. Fixed whole cells in saline water were imaged with fluorescence microscopy and subsequently with STEM. The STEM images were correlated with fluorescence images of the same cellular regions. QDs of dimensions 7 × 12 nm were visible in a 5 μm thick layer of saline water, consistent with calculations. A spatial resolution of 3 nm was achieved on the QDs. PMID:20550177

Transport properties of ultra-thin VO2 films on (001) TiO2 grown by reactive molecular-beam epitaxy

NASA Astrophysics Data System (ADS)

Paik, Hanjong; Moyer, Jarrett A.; Spila, Timothy; Tashman, Joshua W.; Mundy, Julia A.; Freeman, Eugene; Shukla, Nikhil; Lapano, Jason M.; Engel-Herbert, Roman; Zander, Willi; Schubert, Jürgen; Muller, David A.; Datta, Suman; Schiffer, Peter; Schlom, Darrell G.

2015-10-01

We report the growth of (001)-oriented VO2 films as thin as 1.5 nm with abrupt and reproducible metal-insulator transitions (MIT) without a capping layer. Limitations to the growth of thinner films with sharp MITs are discussed, including the Volmer-Weber type growth mode due to the high energy of the (001) VO2 surface. Another key limitation is interdiffusion with the (001) TiO2 substrate, which we quantify using low angle annular dark field scanning transmission electron microscopy in conjunction with electron energy loss spectroscopy. We find that controlling island coalescence on the (001) surface and minimization of cation interdiffusion by using a low growth temperature followed by a brief anneal at higher temperature are crucial for realizing ultrathin VO2 films with abrupt MIT behavior.

High-Speed Coating Method for Photovoltaic Textiles with Closed-Type Die Coater

NASA Astrophysics Data System (ADS)

Imai, Takahiko; Shibayama, Norihisa; Takamatsu, Seiichi; Shiraishi, Kenji; Marumoto, Kazuhiro; Itoh, Toshihiro

2013-06-01

We developed a closed-type die-coating method to fabricate thin films for electronic devices. We succeeded in the die-coating of poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) water dispersions and regioregular poly(3-hexylthiophene):[6,6]-phenyl C61-butyric acid methyl ester (P3HT:PCBM) solution to fabricate thin films of these organic materials with extremely high speeds of 5 and 20 m/min, respectively. The film thicknesses were evaluated by cross-sectional scanning electron microscopy (SEM). The deviations of the film thicknesses from our target values were less than 5%. We fabricated Al/P3HT:PCBM/PEDOT:PSS/indium tin oxide (ITO)/poly(ethylene terephthalate) (PET) textiles as an example of an application of the method, and the photovoltaic characteristic of the devices was confirmed.

Molecular and electronic structure of thin films of protoporphyrin(IX)Fe(III)Cl

NASA Astrophysics Data System (ADS)

Snyder, Shelly R.; White, Henry S.

1991-11-01

Electrochemical, scanning tunneling microscopy (STM), and tunneling spectroscopy studies of the molecular and electronic properties of thin films of protoporphyrin(IX)Fe(III)Cl (abbreviated as PP(IX)Fe(III)Cl) on highly oriented pyrolytic graphite (HOPG) electrodes are reported. PP(IX)Fe(III)Cl films are prepared by two different methods: (1) adsorption, yielding an electrochemically-active film, and (2) irreversible electrooxidative polymerization, yielding an electrochemically-inactive film. STM images, in conjunction with electro-chemical results, indicate that adsorption of PP(IX)Fe(III)Cl from aqueous solutions onto freshly cleaved HOPG results in a film comprised of molecular aggregates. In contrast, films prepared by irreversible electrooxidative polymerization of PP(IX)Fe(III)Cl have a denser, highly structured morphology, including what appear to be small pinholes (approx. 50A diameter) in an otherwise continuous film.

Low-temperature MOCVD deposition of Bi2Te3 thin films using Et2BiTeEt as single source precursor

NASA Astrophysics Data System (ADS)

Bendt, Georg; Gassa, Sanae; Rieger, Felix; Jooss, Christian; Schulz, Stephan

2018-05-01

Et2BiTeEt was used as single source precursor for the deposition of Bi2Te3 thin films on Si(1 0 0) substrates by metal organic chemical vapor deposition (MOCVD) at very low substrate temperatures. Stoichiometric and crystalline Bi2Te3 films were grown at 230 °C, which is approximately 100 °C lower compared to conventional MOCVD processes using one metal organic precursors for each element. The Bi2Te3 films were characterized using scanning electron microscopy, high-resolution transmission electron microscopy and X-ray diffraction. The elemental composition of the films, which was determined by energy-dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy, was found to be strongly dependent of the substrate temperature.

Thin and flexible all-solid supercapacitor prepared from novel single wall carbon nanotubes/polyaniline thin films obtained in liquid-liquid interfaces

NASA Astrophysics Data System (ADS)

de Souza, Victor Hugo Rodrigues; Oliveira, Marcela Mohallem; Zarbin, Aldo José Gorgatti

2014-08-01

The present work describes for the first time the synthesis and characterization of single wall carbon nanotubes/polyaniline (SWNTs/PAni) nanocomposite thin films in a liquid-liquid interface, as well as the subsequent construction of a flexible all-solid supercapacitor. Different SWNTs/PAni nanocomposites were prepared by varying the ratio of SWNT to aniline, and the samples were characterized by scanning and transmission electron microscopy, Raman and UV-Vis spectroscopy, cyclic voltammetry and electrochemical impedance spectroscopy. The pseudo-capacitive behavior of the nanocomposites was evaluated by charge/discharge galvanostatic measurements. The presence of the SWNTs affected the electronic and vibrational properties of the polyaniline and also improved the pseudo-capacitive behavior of the conducting polymer. A very thin and flexible all-solid device was manufactured using two electrodes (polyethylene terephthalate-PET covered with the SWNT/PAni nanocomposite separated by a H2SO4-PVA gel electrolyte). The pseudo-capacitive behavior was characterized by a volumetric specific capacitance of approximately 76.7 F cm-3, even under mechanical deformation, indicating that this nanocomposite has considerable potential for application in new-generation energy storage devices.

Facile One-Pot Synthesis of Flower Like Cobalt Oxide Nanostructures on Nickel Plate and Its Supercapacitance Properties.

PubMed

Kandasamy, N; Venugopal, T; Kannan, K

2018-06-01

A flower like cobalt oxide nanostructured thin film (Co2O3) on Nickel (Ni) plate as have been successfully developed via alcoholic Seed Layer assisted chemical bath Deposition (SLD) process. Through the controlled alkaline electrolytes, the flower and paddles like Co2O3 nanoarchitectures were formed. The prepared thin film was characterized by X-ray diffraction (XRD), scanning electron microscope with energy dispersive X-ray (SEM and EDX), Atomic Force Microscope (AFM), Raman spectroscopy techniques. Electron micrograph reveals the flower and paddles like nanostructured Co2O3 thin film deposited on Ni plates. The electrochemical characteristics were investigated using cyclic voltammetry (CV), charge-discharge and AC impedance spectroscopy in different aqueous electrolytes such as NaOH, KOH, and LiOH. The maximum specific capacitance of 856 Fg-1 was attained with 2 M KOH electrolyte with 2 mVs-1 of the Co2O3 thin film coated Ni plate at 80 °C using SLD method. The capacitance values obtained with various electrolytes are in the order of KOH > NaOH > LiOH. The results indicate that the present method is economical and the material is ecofriendly with enhanced capacitance property.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mohri, Maryam, E-mail: mmohri@ut.ac.ir; Karlsruhe Institute of Technology, Institute of Nanotechnology, 76021 Karlsruhe; Nili-Ahmadabadi, Mahmoud

The crystallization of Ni-rich/NiTiCu bi-layer thin film deposited by magnetron sputtering from two separate alloy targets was investigated. To achieve the shape memory effect, the NiTi thin films deposited at room temperature with amorphous structure were annealed at 773 K for 15, 30, and 60 min for crystallization. Characterization of the films was carried out by differential scanning calorimetry to indicate the crystallization temperature, grazing incidence X-ray diffraction to identify the phase structures, atomic force microscopy to evaluate surface morphology, scanning transmission electron microscopy to study the cross section of the thin films. The results show that the structure ofmore » the annealed thin films strongly depends on the temperature and time of the annealing. Crystalline grains nucleated first at the surface and then grew inward to form columnar grains. Furthermore, the crystallization behavior was markedly affected by composition variations. - Highlights: • A developed bi-layer Ni45TiCu5/Ni50.8Ti was deposited on Si substrate and crystallized. • During crystallization, The Ni{sub 45}TiCu{sub 5} layer is thermally less stable than the Ni-rich layer. • The activation energy is 302 and 464 kJ/mol for Cu-rich and Ni-rich layer in bi-layer, respectively.« less

Uniform thin films of CdSe and CdSe(ZnS) core(shell) quantum dots by sol-gel assembly: enabling photoelectrochemical characterization and electronic applications.

PubMed

Korala, Lasantha; Wang, Zhijie; Liu, Yi; Maldonado, Stephen; Brock, Stephanie L

2013-02-26

Optoelectronic properties of quantum dot (QD) films are limited by (1) poor interfacial chemistry and (2) nonradiative recombination due to surface traps. To address these performance issues, sol-gel methods are applied to fabricate thin films of CdSe and core(shell) CdSe(ZnS) QDs. High-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) imaging with chemical analysis confirms that the surface of the QDs in the sol-gel thin films are chalcogen-rich, consistent with an oxidative-induced gelation mechanism in which connectivity is achieved by formation of dichalcogenide covalent linkages between particles. The ligand removal and assembly process is probed by thermogravimetric, spectroscopic, and microscopic studies. Further enhancement of interparticle coupling via mild thermal annealing, which removes residual ligands and reinforces QD connectivity, results in QD sol-gel thin films with superior charge transport properties, as shown by a dramatic enhancement of electrochemical photocurrent under white light illumination relative to thin films composed of ligand-capped QDs. A more than 2-fold enhancement in photocurrent, and a further increase in photovoltage can be achieved by passivation of surface defects via overcoating with a thin ZnS shell. The ability to tune interfacial and surface characteristics for the optimization of photophysical properties suggests that the sol-gel approach may enable formation of QD thin films suitable for a range of optoelectronic applications.

Ion Beam Assisted Deposition of Thin Epitaxial GaN Films.

PubMed

Rauschenbach, Bernd; Lotnyk, Andriy; Neumann, Lena; Poppitz, David; Gerlach, Jürgen W

2017-06-23

The assistance of thin film deposition with low-energy ion bombardment influences their final properties significantly. Especially, the application of so-called hyperthermal ions (energy <100 eV) is capable to modify the characteristics of the growing film without generating a large number of irradiation induced defects. The nitrogen ion beam assisted molecular beam epitaxy (ion energy <25 eV) is used to deposit GaN thin films on (0001)-oriented 6H-SiC substrates at 700 °C. The films are studied in situ by reflection high energy electron diffraction, ex situ by X-ray diffraction, scanning tunnelling microscopy, and high-resolution transmission electron microscopy. It is demonstrated that the film growth mode can be controlled by varying the ion to atom ratio, where 2D films are characterized by a smooth topography, a high crystalline quality, low biaxial stress, and low defect density. Typical structural defects in the GaN thin films were identified as basal plane stacking faults, low-angle grain boundaries forming between w-GaN and z-GaN and twin boundaries. The misfit strain between the GaN thin films and substrates is relieved by the generation of edge dislocations in the first and second monolayers of GaN thin films and of misfit interfacial dislocations. It can be demonstrated that the low-energy nitrogen ion assisted molecular beam epitaxy is a technique to produce thin GaN films of high crystalline quality.

Uniform Thin Films of CdSe and CdSe(ZnS) Core(shell) Quantum Dots by Sol-Gel Assembly: Enabling Photoelectrochemical Characterization and Electronic Applications

PubMed Central

Korala, Lasantha; Wang, Zhijie; Liu, Yi; Maldonado, Stephen; Brock, Stephanie L.

2013-01-01

Optoelectronic properties of quantum dot (QD) films are limited by (1) poor interfacial chemistry and (2) non-radiative recombination due to surface traps. To address these performance issues, sol-gel methods are applied to fabricate thin films of CdSe and core(shell) CdSe(ZnS) QDs. High-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) imaging with chemical analysis confirms that the surface of the QDs in the sol-gel thin films are chalcogen-rich, consistent with an oxidative-induced gelation mechanism in which connectivity is achieved by formation of dichalcogenide covalent linkages between particles. The ligand removal and assembly process is probed by thermogravimetric, spectroscopic and microscopic studies. Further enhancement of inter-particle coupling via mild thermal annealing, which removes residual ligands and reinforces QD connectivity, results in QD sol-gel thin films with superior charge transport properties, as shown by a dramatic enhancement of electrochemical photocurrent under white light illumination relative to thin films composed of ligand-capped QDs. A more than 2-fold enhancement in photocurrent, and a further increase in photovoltage can be achieved by passivation of surface defects via overcoating with a thin ZnS shell. The ability to tune interfacial and surface characteristics for the optimization of photophysical properties suggests that the sol-gel approach may enable formation of QD thin films suitable for a range of optoelectronic applications. PMID:23350924

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lorut, F.; Imbert, G.; Roggero, A.

In this paper, we investigate the tendency of porous low-K dielectrics (also named Ultra Low-K, ULK) behavior to shrink when exposed to the electron beam of a scanning electron microscope. Various experimental electron beam conditions have been used for irradiating ULK thin films, and the resulting shrinkage has been measured through use of an atomic force microscope tool. We report the shrinkage to be a fast, cumulative, and dose dependent effect. Correlation of the shrinkage with incident electron beam energy loss has also been evidenced. The chemical modification of the ULK films within the interaction volume has been demonstrated, withmore » a densification of the layer and a loss of carbon and hydrogen elements being observed.« less

Nonlinear refraction properties of nickel oxide thin films at 800 nm

DOE Office of Scientific and Technical Information (OSTI.GOV)

Melo, Ronaldo P. Jr. de; Silva, Blenio J. P. da; Santos, Francisco Eroni P. dos

2009-11-01

Measurements of the nonlinear refractive index, n{sub 2}, of nickel oxide films prepared by controlled oxidation of nickel films deposited on substrates of soda-lime glass are reported. The structure and morphology of the samples were characterized by scanning electron microscopy, atomic force microscopy, and x-ray diffractometry. Samples of excellent optical quality were prepared. The nonlinear measurements were performed using the thermally managed eclipse Z-scan technique at 800 nm. A large value of n{sub 2}approx =10{sup -12} cm{sup 2}/W and negligible nonlinear absorption were obtained.

Synthesis and Characterization of the First Liquid Single Source Precursors for the Deposition of Ternary Chalcopyrite (CuInS2) Thin Film Materials

NASA Technical Reports Server (NTRS)

Banger, Kulbinder K.; Cowen, Jonathan; Hepp, Aloysius

2002-01-01

Molecular engineering of ternary single source precursors based on the [{PBu3}2Cu(SR')2In(SR')2] architecture have afforded the first liquid CIS ternary single source precursors (when R = Et, n-Pr), which are suitable for low temperature deposition (< 350 C). Thermogravimetric analyses (TGA) and modulated-differential scanning calorimetry (DSC) confirm their liquid phase and reduced stability. X-ray diffraction studies, energy dispersive analyzer (EDS), and scanning electron microscopy (SEM) support the formation of the single-phase chalcopyrite CuInS2 at low temperatures.

Graphene-Decorated Nanocomposites for Printable Electrodes in Thin Wafer Devices

NASA Astrophysics Data System (ADS)

Bakhshizadeh, N.; Sivoththaman, S.

2017-12-01

Printable electrodes that induce less stress and require lower curing temperatures compared to traditional screen-printed metal pastes are needed in thin wafer devices such as future solar cells, and in flexible electronics. The synthesis of nanocomposites by incorporating graphene nanopowders as well as silver nanowires into epoxy-based electrically conductive adhesives (ECA) is examined to improve electrical conductivity and to develop alternate printable electrode materials that induce less stress on the wafer. For the synthesized graphene and Ag nanowire-decorated ECA nanocomposites, the curing kinetics were studied by dynamic and isothermal differential scanning calorimetry measurements. Thermogravimetric analysis on ECA, ECA-AG and ECA/graphene nanopowder nanocomposites showed that the temperatures for onset of decomposition are higher than their corresponding glass transition temperature ( T g) indicating an excellent thermal resistance. Printed ECA/Ag nanowire nanocomposites showed 90% higher electrical conductivity than ECA films, whereas the ECA/graphene nanocomposites increased the conductivity by over two orders of magnitude. Scanning electron microscopy results also revealed the effect of fillers morphology on the conductivity improvement and current transfer mechanisms in nanocomposites. Residual stress analysis performed on Si wafers showed that the ECA and nanocomposite printed wafers are subjected to much lower stress compared to those printed with metallic pastes. The observed parameters of low curing temperature, good thermal resistance, reasonably high conductivity, and low residual stress in the ECA/graphene nanocomposite makes this material a promising alternative in screen-printed electrode formation in thin substrates.

Proton irradiation of beryllium deposits on different candidate materials to be used as a neutron production target for accelerator-based BNCT

NASA Astrophysics Data System (ADS)

Gagetti, Leonardo; Anzorena, Manuel Suarez; Bertolo, Alma; del Grosso, Mariela; Kreiner, Andrés J.

2017-12-01

Thin Be targets for neutron production through Be(d,n) are produced and characterized. We improved and characterized the substrate surface, specifically the roughness, in order to achieve homogeneous and stable deposits. Once well bonded deposits were obtained, some of them were irradiated with a 150 keV proton beam and with a 1.45 MeV deuteron beam. Both deposits, pristine and irradiated, were characterized by profilometry, X-ray diffraction, scanning electron microscopy and electron probe microanalyzer.

Terrace-like morphology of the boundary created through basal-prismatic transformation in magnesium

DOE PAGES

Liu, Bo -Yu; Wan, Liang; Wang, Jian; ...

2015-01-24

Here, the boundaries created through basal-prismatic transformation in submicron-sized single crystal magnesium have been investigated systematically using in situ transmission electron microscopy. We found that these boundaries not only deviated significantly from the twin plane associated with {101¯2} twin, but also possessed a non-planar morphology. After the sample was thinned to be less than 90 nm, aberration-corrected scanning transmission electron microscopy observation found that the basic components of these boundaries are actually terrace-like basal-prismatic interfaces.

Electrochemically Controlled Ion-exchange Property of Carbon Nanotubes/Polypyrrole Nanocomposite in Various Electrolyte Solutions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Choi, Daiwon; Zhu, Chengzhou; Fu, Shaofang

2016-09-15

The electrochemically controlled ion-exchange properties of multi-wall carbon nanotube (MWNT)/electronically conductive polypyrrole (PPy) polymer composite in the various electrolyte solutions have been investigated. The ion-exchange behavior, rate and capacity of the electrochemically deposited polypyrrole with and without carbon nanotube (CNT) were compared and characterized using cyclic voltammetry (CV), chronoamperometry (CA), electrochemical quartz crystal microbalance (EQCM), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). It has been found that the presence of carbon nanotube backbone resulted in improvement in ion-exchange rate, stability of polypyrrole, and higher anion loading capacity per PPy due to higher surface area, electronic conductivity, porous structuremore » of thin film, and thinner film thickness providing shorter diffusion path. Chronoamperometric studies show that electrically switched anion exchange could be completed more than 10 times faster than pure PPy thin film. The anion selectivity of CNT/PPy film is demonstrated using X-ray photoelectron spectroscopy (XPS).« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pawar, C. S., E-mail: charudutta-p@yahoo.com; Gujar, M. P.; Mathe, V. L.

Nano crystalline Nickel Zinc ferrite (Ni{sub 0.25}Zn{sub 0.75}Fe{sub 2}O{sub 4}) thin films were synthesized by Sol Gel method for gas response. The phase and microstructure of the obtained Ni{sub 0.25}Zn{sub 0.75}Fe{sub 2}O{sub 4} thin films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM). The nanostructured Ni{sub 0.25}Zn{sub 0.75}Fe{sub 2}O{sub 4} thin film shows single spinel phase. Magnetic study was obtained with the help of VSM. The effects of working temperature on the gas response were studied. The results reveal that the Ni{sub 0.25}Zn{sub 0.75}Fe{sub 2}O{sub 4} thin film gas sensor shows good selectivity to chlorine gas at roommore » temperature. The sensor shows highest sensitivity (∼50%) at room temperature, indicating its application in detecting chlorine gas at room temperature in the future.« less

Improving Fire Resistance of Cotton Fabric through Layer-by-Layer Assembled Graphene Multilayer Nanocoating

NASA Astrophysics Data System (ADS)

Jang, Wonjun; Chung, Il Jun; Kim, Junwoo; Seo, Seongmin; Park, Yong Tae; Choi, Kyungwho

2018-05-01

In this study, thin films containing poly(vinyl alcohol) (PVA) and graphene nanoplatelets (GNPs), stabilized with poly(4-styrene-sulfonic acid) (PSS), were assembled by a simple and cost-effective layer-by-layer (LbL) technique in order to introduce the anti-flammability to cotton. These antiflammable layers were characterized by using UV-vis spectrometry and quartz crystal microbalance as a function of the number of bilayers deposited. Scanning electron microscopy was used to visualize the morphology of the thin film coatings on the cotton fabric. The graphene-polymer thin films introduced anti-flammable properties through thermally stable carbonaceous layers at a high temperature. The thermal stability and flame retardant property of graphene-coated cotton was demonstrated by thermogravimetric analysis, cone calorimetry, and vertical flame test. The results indicate that LbL-assembled graphene-polymer thin films can be applied largely in the field of flame retardant.

Effect of Ag doping on the properties of ZnO thin films for UV stimulated emission

NASA Astrophysics Data System (ADS)

Razeen, Ahmed S.; Gadallah, A.-S.; El-Nahass, M. M.

2018-06-01

Ag doped ZnO thin films have been prepared using sol-gel spin coating method, with different doping concentrations. Structural and morphological properties of the films have been investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. Thin films have been optically pumped and stimulated emission has been observed with strong peaks in the UV region. The UV stimulated emission is found to be due to exciton-exciton scattering, and Ag doping promoted this process by increasing the excitons concentrations in the ZnO lattice. Output-input intensity relation and peak emission, FWHM, and quantum efficiency relations with pump intensity have been reported. The threshold for which stimulated emission started has been evaluated to be about 18 MW/cm2 with quantum efficiency of about 58.7%. Mechanisms explaining the role of Ag in enhancement of stimulated emission from ZnO thin films have been proposed.

Evaluation of the optical characteristics of c-axis oriented zinc oxide thin films grown by sol gel spin coating technique

NASA Astrophysics Data System (ADS)

Baisakh, K.; Behera, S.; Pati, S.

2018-03-01

In this work we have systematically studied the optical characteristics of synthesized wurzite zinc oxide thin films exhibiting (002) orientation. Using sol gel spin coating technique zinc oxide thin films are grown on pre cleaned fused quartz substrates. Structural properties of the films are studied using X-ray diffraction analysis. Micro structural analysis and thickness of the grown samples are analyzed using field emission scanning electron microscopy. With an aim to investigate the optical characteristics of the grown zinc oxide thin films the transmission and reflection spectra are evaluated in the ultraviolet-visible (UV-VIS) range. Using envelope method, the refractive index, extinction coefficient, absorption coefficient, band gap energy and the thickness of the synthesized films are estimated from the recorded UV-VIS spectra. An attempt has also been made to study the influence of crystallographic orientation on the optical characteristics of the grown films.

Growth and structure of Bi 0.5(Na 0.7K 0.2Li 0.1) 0.5TiO 3 thin films prepared by pulsed laser deposition technique

NASA Astrophysics Data System (ADS)

Lu, Lei; Xiao, Dingquan; Lin, Dunmin; Zhang, Yongbin; Zhu, Jianguo

2009-02-01

Bi 0.5(Na 0.7K 0.2Li 0.1) 0.5TiO 3 (BNKLT) thin films were prepared on Pt/Ti/SiO 2/Si substrates by pulsed laser deposition (PLD) technique. The films prepared were examined by using X-ray diffraction (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM). The effects of the processing parameters, such as oxygen pressure, substrate temperature and laser power, on the crystal structure, surface morphology, roughness and deposition rates of the thin films were investigated. It was found that the substrate temperature of 600 °C and oxygen pressure of 30 Pa are the optimized technical parameters for the growth of textured film, and all the thin films prepared have granular structure, homogeneous grain size and smooth surfaces.

Ridge Minimization of Ablated Morphologies on ITO Thin Films Using Squared Quasi-Flat Top Beam

PubMed Central

Jeon, Jin-Woo; Choi, Wonsuk; Shin, Young-Gwan; Ji, Suk-Young

2018-01-01

In this study, we explore the improvements in pattern quality that was obtained with a femtosecond laser with quasi-flat top beam profiles at the ablated edge of indium tin oxide (ITO) thin films for the patterning of optoelectronic devices. To ablate the ITO thin films, a femtosecond laser is used that has a wavelength and pulse duration of 1030 nm and 190 fs, respectively. The squared quasi-flat top beam is obtained from a circular Gaussian beam using slits with varying x-y axes. Then, the patterned ITO thin films are measured using both scanning electron and atomic force microscopes. In the case of the Gaussian beam, the ridge height and width are approximately 39 nm and 1.1 μm, respectively, whereas, when the quasi-flat top beam is used, the ridge height and width are approximately 7 nm and 0.25 μm, respectively. PMID:29601515

Mechanical comparison of a polymer nanocomposite to a ceramic thin-film anti-reflective filter.

PubMed

Druffel, Thad; Geng, Kebin; Grulke, Eric

2006-07-28

Thin-film filters on optical components have been in use for decades and, for those industries utilizing a polymer substrate, the mismatch in mechanical behaviour has caused problems. Surface damage including scratches and cracks induces haze on the optical filter, reducing the transmission of the optical article. An in-mold anti-reflective (AR) filter incorporating 1/4-wavelength thin films based on a polymer nanocomposite is outlined here and compared with a traditional vacuum deposition AR coating. Nanoindentation and nanoscratch techniques are used to evaluate the mechanical properties of the thin films. Scanning electron microscopy (SEM) images of the resulting indentations and scratches are then compared to the force deflection curves to further explain the phenomena. The traditional coatings fractured by brittle mechanisms during testing, increasing the area of failure, whereas the polymer nanocomposite gave ductile failure with less surface damage.

Growth of diamond by RF plasma-assisted chemical vapor deposition

NASA Technical Reports Server (NTRS)

Meyer, Duane E.; Ianno, Natale J.; Woollam, John A.; Swartzlander, A. B.; Nelson, A. J.

1988-01-01

A system has been designed and constructed to produce diamond particles by inductively coupled radio-frequency, plasma-assisted chemical vapor deposition. This is a low-pressure, low-temperature process used in an attempt to deposit diamond on substrates of glass, quartz, silicon, nickel, and boron nitride. Several deposition parameters have been varied including substrate temperature, gas concentration, gas pressure, total gas flow rate, RF input power, and deposition time. Analytical methods employed to determine composition and structure of the deposits include scanning electron microscopy, absorption spectroscopy, scanning Auger microprobe spectroscopy, and Raman spectroscopy. Analysis indicates that particles having a thin graphite surface, as well as diamond particles with no surface coatings, have been deposited. Deposits on quartz have exhibited optical bandgaps as high as 4.5 eV. Scanning electron microscopy analysis shows that particles are deposited on a pedestal which Auger spectroscopy indicates to be graphite. This is a phenomenon that has not been previously reported in the literature.

Chemical synthesis and supercapacitive properties of lanthanum telluride thin film.

PubMed

Patil, S J; Lokhande, A C; Lee, D-W; Kim, J H; Lokhande, C D

2017-03-15

Lanthanum telluride (La 2 Te 3 ) thin films are synthesized via a successive ionic layer adsorption and reaction (SILAR) method. The crystal structure, surface morphology and surface wettability properties are investigated using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Field emission scanning electron microscopy (FE-SEM) and contact angle goniometer techniques, respectively. The La 2 Te 3 material exhibits a specific surface area of 51m 2 g -1 determined by Brunauer-Emmett-Teller (BET) method. La 2 Te 3 thin film electrode has a hydrophilic surface which consists of interconnected pine leaf-like flaky arrays that affect the performance of the supercapacitor. The supercapacitive performance of La 2 Te 3 film electrode is evaluated in 1M LiClO 4 /PC electrolyte using cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy techniques. La 2 Te 3 film electrode exhibits a specific capacitance of 194Fg -1 at a scan rate of 5mVs -1 and stored energy density of 60Whkg -1 with delivering power density of 7.22kWkg -1 . La 2 Te 3 film electrode showed capacitive retention of 82% over 1000cycles at a scan rate of 100mVs -1 . Further, flexible La 2 Te 3 |LiClO 4 -PVA|La 2 Te 3 supercapacitor cell is fabricated. Copyright © 2016 Elsevier Inc. All rights reserved.

Imaging surface acoustic wave dynamics in semiconducting polymers by scanning ultrafast electron microscopy.

PubMed

Najafi, Ebrahim; Liao, Bolin; Scarborough, Timothy; Zewail, Ahmed

2018-01-01

Understanding the mechanical properties of organic semiconductors is essential to their electronic and photovoltaic applications. Despite a large volume of research directed toward elucidating the chemical, physical and electronic properties of these materials, little attention has been directed toward understanding their thermo-mechanical behavior. Here, we report the ultrafast imaging of surface acoustic waves (SAWs) on the surface of the Poly(3-hexylthiophene-2,5-diyl) (P3HT) thin film at the picosecond and nanosecond timescales. We then use these images to measure the propagation velocity of SAWs, which we then employ to determine the Young's modulus of P3HT. We further validate our experimental observation by performing a semi-empirical transient thermoelastic finite element analysis. Our findings demonstrate the potential of ultrafast electron microscopy to not only probe charge carrier dynamics in materials as previously reported, but also to measure their mechanical properties with great accuracy. This is particularly important when in situ characterization of stiffness for thin devices and nanomaterials is required. Copyright © 2017 Elsevier B.V. All rights reserved.

LPG ammonia and nitrogen dioxide gas sensing properties of nanostructured polypyrrole thin film

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bagul, Sagar B., E-mail: nano.sbbagul@gmail.com; Upadhye, Deepak S.; Sharma, Ramphal, E-mail: rps.phy@gmail.com

Nanostructured Polypyrrole thin film was synthesized by easy and economic chemical oxidative polymerization technique on glass at room temperature. The prepared thin film of Polypyrrole was characterized by optical absorbance study by UV-visible spectroscopy and electrical study by I-V measurement system. The optical absorbance spectrum of Polypyrrole shows two fundamental peaks in region of 420 and 890 nm, which confirms the formation of Polypyrrole on glass substrate. The I-V graph of nanostructured Polypyrrole represents the Ohmic nature. Furthermore, the thin film of Polypyrrole was investigated by Scanning electron microscopy for surface morphology study. The SEM micrograph represents spherical nanostructured morphology ofmore » Polypyrrole on glass substrate. In order to investigate gas sensing properties, 100 ppm of LPG, Ammonia and Nitrogen Dioxide were injected in the gas chamber and magnitude of resistance has been recorded as a function of time in second. It was observed that nanostructured Polypyrrole thin film shows good sensing behavior at room temperature.« less

A Study on the Formation of 2-Dimensional Tungsten Disulfide Thin Films on Sapphire Substrate by Sputtering and High Temperature Rapid Thermal Processing.

PubMed

Nam, Hanyeob; Kim, Hong-Seok; Han, Jae-Hee; Kwon, Sang Jik; Cho, Eou Sik

2018-09-01

As direct formation of p-type two-dimensional transition metal dichalcogenides (TMDC) films on substrates, tungsten disulfide (WS2) thin films were deposited onto sapphire glass substrate through shadow mask patterns by radio-frequency (RF) sputtering at different sputtering powers ranging from 60 W to 150 W and annealed by rapid thermal processing (RTP) at various high temperatures ranging from 500 °C to 800 °C. Based on scanning electron microscope (SEM) images and Raman spectra, better surface roughness and mode dominant E12g and A1g peaks were found for WS2 thin films prepared at higher RF sputtering powers. It was also possible to obtain high mobilities and carrier densities for all WS2 thin films based on results of Hall measurements. Process conditions for these WS2 thin films on sapphire substrate were optimized to low RF sputtering power and high temperature annealing.

Semiconducting Properties of Nanostructured Amorphous Carbon Thin Films Incorporated with Iodine by Thermal Chemical Vapor Deposition

NASA Astrophysics Data System (ADS)

Kamaruzaman, Dayana; Ahmad, Nurfadzilah; Annuar, Ishak; Rusop, Mohamad

2013-11-01

Nanostructured iodine-post doped amorphous carbon (a-C:I) thin films were prepared from camphor oil using a thermal chemical vapor deposition (TCVD) technique at different doping temperatures. The structural properties of the films were studied by field-emission scanning electron microscopy (FESEM), energy-dispersive spectroscopy (EDS), Raman, and Fourier transform infrared (FTIR) studies. FESEM and EDS studies showed successful iodine doping. FTIR and Raman studies showed that the a-C:I thin films consisted of a mixture of sp2- and sp3-bonded carbon atoms. The optical and electrical properties of a-C:I thin films were determined by UV-vis-NIR spectroscopy and current-voltage (I-V) measurement respectively. The optical band gap of a-C thin films decreased upon iodine doping. The highest electrical conductivity was found at 400 °C doping. Heterojunctions are confirmed by rectifying the I-V characteristics of an a-C:I/n-Si junction.

Nanocrystalline Pd:NiFe2O4 thin films: A selective ethanol gas sensor

NASA Astrophysics Data System (ADS)

Rao, Pratibha; Godbole, R. V.; Bhagwat, Sunita

2016-10-01

In this work, Pd:NiFe2O4 thin films were investigated for the detection of reducing gases. These films were fabricated using spray pyrolysis technique and characterized using X-ray diffraction (XRD) to confirm the crystal structure. The surface morphology was studied using scanning electron microscopy (SEM). Magnetization measurements were carried out using SQUID VSM, which shows ferrimagnetic behavior of the samples. These thin film sensors were tested against methanol, ethanol, hydrogen sulfide and liquid petroleum gas, where they were found to be more selective to ethanol. The fabricated thin film sensors exhibited linear response signal for all the gases with concentrations up to 5 w/o Pd. Reduction in optimum operating temperature and enhancement in response was also observed. Pd:NiFe2O4 thin films exhibited faster response and recovery characteristic. These sensors have potential for industrial applications because of their long-term stability, low power requirement and low production cost.

Highly antibacterial activity of N-doped TiO2 thin films coated on stainless steel brackets under visible light irradiation

NASA Astrophysics Data System (ADS)

Cao, Shuai; Liu, Bo; Fan, Lingying; Yue, Ziqi; Liu, Bin; Cao, Baocheng

2014-08-01

In this study, the radio frequency (RF) magnetron sputtering method was used to prepare a TiO2 thin film on the surface of stainless steel brackets. Eighteen groups of samples were made according to the experimental parameters. The crystal structure and surface morphology were characterized by X-ray diffraction, and scanning electron microscopy, respectively. The photocatalytic properties under visible light irradiation were evaluated by measuring the degradation ratio of methylene blue. The sputtering temperature was set at 300 °C, and the time was set as 180 min, the ratio of Ar to N was 30:1, and annealing temperature was set at 450 °C. The thin films made under these parameters had the highest visible light photocatalytic activity of all the combinations of parameters tested. Antibacterial activities of the selected thin films were also tested against Lactobacillus acidophilus and Candida albicans. The results demonstrated the thin film prepared under the parameters above showed the highest antibacterial activity.

A Rapid Method for Deposition of Sn-Doped GaN Thin Films on Glass and Polyethylene Terephthalate Substrates

NASA Astrophysics Data System (ADS)

Pat, Suat; Özen, Soner; Korkmaz, Şadan

2018-01-01

We report the influence of Sn doping on microstructure, surface, and optical properties of GaN thin films deposited on glass and polyethylene terephthalate (PET) substrate. Sn-doped GaN thin films have been deposited by thermionic vacuum arc (TVA) at low temperature. TVA is a rapid deposition technology for thin film growth. Surface and optical properties of the thin films were presented. Grain size, height distribution, roughness values were determined. Grain sizes were calculated as 20 nm and 13 nm for glass and PET substrates, respectively. Nano crystalline forms were shown by field emission scanning electron microscopy. Optical band gap values were determined by optical methods and photoluminescence measurement. The optical band gap values of Sn doped GaN on glass and PET were determined to be approximately ˜3.40 eV and ˜3.47 eV, respectively. As a result, TVA is a rapid and low temperature deposition technology for the Sn doped GaN deposited on glass and PET substrate.

LPG ammonia and nitrogen dioxide gas sensing properties of nanostructured polypyrrole thin film

NASA Astrophysics Data System (ADS)

Bagul, Sagar B.; Upadhye, Deepak S.; Sharma, Ramphal

2016-05-01

Nanostructured Polypyrrole thin film was synthesized by easy and economic chemical oxidative polymerization technique on glass at room temperature. The prepared thin film of Polypyrrole was characterized by optical absorbance study by UV-visible spectroscopy and electrical study by I-V measurement system. The optical absorbance spectrum of Polypyrrole shows two fundamental peaks in region of 420 and 890 nm, which confirms the formation of Polypyrrole on glass substrate. The I-V graph of nanostructured Polypyrrole represents the Ohmic nature. Furthermore, the thin film of Polypyrrole was investigated by Scanning electron microscopy for surface morphology study. The SEM micrograph represents spherical nanostructured morphology of Polypyrrole on glass substrate. In order to investigate gas sensing properties, 100 ppm of LPG, Ammonia and Nitrogen Dioxide were injected in the gas chamber and magnitude of resistance has been recorded as a function of time in second. It was observed that nanostructured Polypyrrole thin film shows good sensing behavior at room temperature.

Cu2SixSn1-xS3 Thin Films Prepared by Reactive Magnetron Sputtering For Low-Cost Thin Film Solar Cells

NASA Astrophysics Data System (ADS)

Yan, Chang; Liu, Fang-Yang; Lai, Yan-Qing; Li, Jie; Liu, Ye-Xiang

2011-10-01

We report the preparation of Cu2SixSn1-xS3 thin films for thin film solar cell absorbers using the reactive magnetron co-sputtering technique. Energy dispersive spectrometer and x-ray diffraction analyses indicate that Cu2Si1-xSnxS3 thin films can be synthesized successfully by partly substituting Si atoms for Sn atoms in the Cu2SnS3 lattice, leading to a shrinkage of the lattice, and, accordingly, by 2θ shifting to larger values. The blue shift of the Raman peak further confirms the formation of Cu2SixSn1-xS3. Environmental scanning electron microscope analyses reveal a polycrystalline and homogeneous morphology with a grain size of about 200-300 nm. Optical measurements indicate an optical absorption coefficient of higher than 104 cm-1 and an optical bandgap of 1.17±0.01 eV.

Plasma assisted facile synthesis of vanadium oxide (V3O7) nanostructured thin films

NASA Astrophysics Data System (ADS)

Singh, Megha; Saini, Sujit K.; Kumar, Prabhat; Sharma, Rabindar K.; Reddy, G. B.

2018-05-01

Vanadium oxides nanostructured thin films are synthesized using plasma assisted sublimation process. The effect of temperatures on growth of V2O5 and V3O7 thin films is studied. Scanning electron micrographs shows different morphologies are obtained at different temperatures i.e. at 450 °C nano cubes-like structures are obtained, whereas at 550 °C and 650 °C nanorods are obtained. Sample deposited at 450 °C is entirely composed of V2O5 and sample at higher temperatures are composed of mixed phase of vanadium oxides i.e. V2O5 and V3O7. As temperature increased, so the content of V3O7 in the sample is increased as confirmed by XRD and Raman analyses.

Structural and mechanical properties of CVD deposited titanium aluminium nitride (TiAlN) thin films

NASA Astrophysics Data System (ADS)

Das, Soham; Guha, Spandan; Ghadai, Ranjan; Kumar, Dhruva; Swain, Bibhu P.

2017-06-01

Titanium aluminium nitride (TiAlN) thin films were deposited by chemical vapour deposition using TiO2 powder, Al powder and N2 gas. The morphology and mechanical properties of the films were characterized by scanning electron microscopy and nanoindentation technique, respectively. The structural properties were characterized by Raman spectroscopy and X-ray diffraction. The XRD result shows TiAlN films are of NaCl-type metal nitride structure. Micro-Raman peaks of the TiAlN thin film were observed within 450 and 642 cm-1 for acoustic and optic range, respectively. A maximum hardness and Young modulus up to 22 and 272.15 GPa, respectively, were observed in the TiAlN film deposited at 1200 °C.

Annealing temperature effect on electrical properties of MEH-PPV thin film via spin coating method

NASA Astrophysics Data System (ADS)

Azhar, N. E. A.; Shariffudin, S. S.; Alrokayan, Salman A. H.; Khan, Haseeb A.; Rusop, M.

2018-05-01

Organic semiconductor has been discovered in different application devices such as organic light emitting diodes (OLEDs). Poly [2-methoxy-5(2' -ethylhexyloxy)-1, 4-phenylenevinylene), MEH-PPV widely used in this device because its ability to produce a good optical quality films. The MEH-PPV was prepared on glass substrate by spin coating method. The thin film was investigated at different annealing temperatures. The scanning electron micrographs (SEM) revealed that sample annealed at 50°C showed uniformity and less aggregation on morphology polymer thin film. Optical properties showed the intensities of visible emission increased as temperatures increased. The current-voltage (I-V) measurement revealed that the temperature of 50°C showed high conductive and it is suitable for optoelectronic device.

Preparation and characterization of copper telluride thin films by modified chemical bath deposition (M-CBD) method

NASA Astrophysics Data System (ADS)

Pathan, H. M.; Lokhande, C. D.; Amalnerkar, D. P.; Seth, T.

2003-09-01

Copper telluride thin films were deposited using modified chemical method using copper(II) sulphate; pentahydrate [CuSO 4·5H 2O] and sodium tellurite [Na 2TeO 3] as cationic and anionic sources, respectively. Modified chemical method is based on the immersion of the substrate into separately placed cationic and anionic precursors. The preparative conditions such as concentration, pH, immersion time, immersion cycles, etc. were optimized to get good quality copper telluride thin films at room temperature. The films have been characterized for structural, compositional, optical and electrical transport properties by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDAX), Rutherford back scattering (RBS), optical absorption/transmission, electrical resistivity and thermoemf measurement techniques.

A green synthesis method for large area silver thin film containing nanoparticles.

PubMed

Shinde, N M; Lokhande, A C; Lokhande, C D

2014-07-05

The green synthesis method is inexpensive and convenient for large area deposition of thin films. For the first time, a green synthesis method for large area silver thin film containing nanoparticles is reported. Silver nanostructured films are deposited using silver nitrate solution and guava leaves extract. The study confirmed that the reaction time plays a key role in the growth and shape/size control of silver nanoparticles. The properties of silver films are studied using UV-visible spectrophotometer, scanning electron microscopy (SEM), X-ray diffraction (XRD), atomic force microscopy (AFM), contact angle, Fourier-transform Raman (FT-Raman) spectroscopy and Photoluminescence (PL) techniques. Finally, as an application, these films are used effectively in antibacterial activity study. Copyright © 2014 Elsevier B.V. All rights reserved.

Observations on Si-based micro-clusters embedded in TaN thin film deposited by co-sputtering with oxygen contamination

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, Young Mi; Jung, Min-Sang; Choi, Duck-Kyun, E-mail: duck@hanyang.ac.kr, E-mail: mcjung@oist.jp

2015-08-15

Using scanning electron microscopy (SEM) and high-resolution x-ray photoelectron spectroscopy with the synchrotron radiation we investigated Si-based micro-clusters embedded in TaSiN thin films having oxygen contamination. TaSiN thin films were deposited by co-sputtering on fixed or rotated substrates and with various power conditions of TaN and Si targets. Three types of embedded micro-clusters with the chemical states of pure Si, SiO{sub x}-capped Si, and SiO{sub 2}-capped Si were observed and analyzed using SEM and Si 2p and Ta 4f core-level spectra were derived. Their different resistivities are presumably due to the different chemical states and densities of Si-based micro-clusters.

Exchange bias and bistable magneto-resistance states in amorphous TbFeCo thin films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Xiaopu, E-mail: xl6ba@virginia.edu; Ma, Chung T.; Poon, S. Joseph, E-mail: sjp9x@virginia.edu

2016-01-04

Amorphous TbFeCo thin films sputter deposited at room temperature on thermally oxidized Si substrate are found to exhibit strong perpendicular magnetic anisotropy. Atom probe tomography, scanning transmission electron microscopy, and energy dispersive X-ray spectroscopy mapping have revealed two nanoscale amorphous phases with different Tb atomic percentages distributed within the amorphous film. Exchange bias accompanied by bistable magneto-resistance states has been uncovered near room temperature by magnetization and magneto-transport measurements. The exchange anisotropy originates from the exchange interaction between the ferrimagnetic and ferromagnetic components corresponding to the two amorphous phases. This study provides a platform for exchange bias and magneto-resistance switchingmore » using single-layer amorphous ferrimagnetic thin films that require no epitaxial growth.« less

Enhanced gas sensing correlated with structural and optical properties of Cs-loaded SnO2 nanofilms

NASA Astrophysics Data System (ADS)

Elia Raine, P. J.; Arun George, P.; Balasundaram, O. N.; Varghese, T.

2016-09-01

The Cs-loaded SnO2 thin films were prepared by the spray pyrolysis technique and were characterized by X-ray diffraction, scanning electron microscopy, ultraviolet-visible spectroscopy, impedance spectroscopy and conductometric method. Investigations based on the structural, optical and electrical properties confirm an enhanced gas sensing potential of cesium-loaded tin oxide films. It is found that the tin oxide thin film doped with 4% Cs with a mean grain size of 20 nm at a deposition temperature of 350 ° C show a maximum sensor response of 97.5% for LPG consistently. It is also observed that the sensor response of Cs-doped SnO2 thin films depends on the dopant concentration and the deposition temperature of the film.

Origins of enhanced thermoelectric power factor in topologically insulating Bi{sub 0.64}Sb{sub 1.36}Te{sub 3} thin films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Wei; State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan 430070; Chi, Hang

2016-01-25

In this research, we report the enhanced thermoelectric power factor in topologically insulating thin films of Bi{sub 0.64}Sb{sub 1.36}Te{sub 3} with a thickness of 6–200 nm. Measurements of scanning tunneling spectroscopy and electronic transport show that the Fermi level lies close to the valence band edge, and that the topological surface state (TSS) is electron dominated. We find that the Seebeck coefficient of the 6 nm and 15 nm thick films is dominated by the valence band, while the TSS chiefly contributes to the electrical conductivity. In contrast, the electronic transport of the reference 200 nm thick film behaves similar to bulk thermoelectric materialsmore » with low carrier concentration, implying the effect of the TSS on the electronic transport is merely prominent in the thin region. The conductivity of the 6 nm and 15 nm thick film is obviously higher than that in the 200 nm thick film owing to the highly mobile TSS conduction channel. As a consequence of the enhanced electrical conductivity and the suppressed bipolar effect in transport properties for the 6 nm thick film, an impressive power factor of about 2.0 mW m{sup −1} K{sup −2} is achieved at room temperature for this film. Further investigations of the electronic transport properties of TSS and interactions between TSS and the bulk band might result in a further improved thermoelectric power factor in topologically insulating Bi{sub 0.64}Sb{sub 1.36}Te{sub 3} thin films.« less

Gold nanoparticle uptake in whole cells in liquid examined by environmental scanning electron microscopy.

PubMed

Peckys, Diana B; de Jonge, Niels

2014-02-01

The size of gold nanoparticles (AuNPs) can influence various aspects of their cellular uptake. Light microscopy is not capable of resolving most AuNPs, while electron microscopy (EM) is not practically capable of acquiring the necessary statistical data from many cells and the results may suffer from various artifacts. Here, we demonstrate the use of a fast EM method for obtaining high-resolution data from a much larger population of cells than is usually feasible with conventional EM. A549 (human lung carcinoma) cells were subjected to uptake protocols with 10, 15, or 30 nm diameter AuNPs with adsorbed serum proteins. After 20 min, 24 h, or 45 h, the cells were fixed and imaged in whole in a thin layer of liquid water with environmental scanning electron microscopy equipped with a scanning transmission electron microscopy detector. The fast preparation and imaging of 145 whole cells in liquid allowed collection of nanoscale data within an exceptionally small amount of time of ~80 h. Analysis of 1,041 AuNP-filled vesicles showed that the long-term AuNP storing lysosomes increased their average size by 80 nm when AuNPs with 30 nm diameter were uptaken, compared to lysosomes of cells incubated with AuNPs of 10 and 15 nm diameter.

Development of nanostructured ZnO thin film via electrohydrodynamic atomization technique and its photoconductivity characteristics.

PubMed

Duraisamy, Navaneethan; Kwon, Ki Rin; Jo, Jeongdai; Choi, Kyung-Hyun

2014-08-01

This article presents the non-vacuum technique for the preparation of nanostructured zinc oxide (ZnO) thin film on glass substrate through electrohydrodynamic atomization (EHDA) technique. The detailed process parameters for achieving homogeneous ZnO thin films are clearly discussed. The crystallinity and surface morphology of ZnO thin film are investigated by X-ray diffraction and field emission scanning electron microscopy. The result shows that the deposited ZnO thin film is oriented in the wurtzite phase with void free surface morphology. The surface roughness of deposited ZnO thin film is found to be ~17.8 nm. The optical properties of nanostructured ZnO thin films show the average transmittance is about 90% in the visible region and the energy band gap is found to be 3.17 eV. The surface chemistry and purity of deposited ZnO thin films are analyzed by fourier transform infrared and X-ray photoelectron spectroscopy, conforming the presence of Zn-O in the deposited thin films without any organic moiety. The photocurrent measurement of nanostructured ZnO thin film is examined in the presence of UV light illumination with wavelength of 365 nm. These results suggest that the deposited nanostructured ZnO thin film through EHDA technique possess promising applications in the near future.

Nanostructuring on zinc phthalocyanine thin films for single-junction organic solar cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chaudhary, Dhirendra K.; Kumar, Lokendra, E-mail: lokendrakr@allduniv.ac.in

2016-05-23

Vertically aligned and random oriented crystalline molecular nanorods of organic semiconducting Zinc Phthalocyanine (ZnPc) have been grown on ITO coated glass substrate using solvent volatilization method. Interesting changes in surface morphology were observed under different solvent treatment. Vertically aligned nanorods of ZnPc thin film were observed in the films treated with acetone, where as the random oriented nanorods were observed in the films treated with chloroform. The X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM) have been used for characterization of nanostructures. The optical properties of the nanorods have been investigated by UV-Vis. absorption spectroscopy.

Electrochromic TiO2 Thin Film Prepared by Dip-Coating Technique

NASA Astrophysics Data System (ADS)

Suriani, S.; Kamisah, M. M.

2002-12-01

Titanium dioxide (TiO2) thin films were prepared by using sol-gel dip coating technique. The coating solutions were prepared by reacting titanium isopropoxide as precursors and ethanol as solvent. The films were formed on transparent ITO-coated glass by a dip coating technique and final dried at various temperatures up to 600 °C for 30 minutes. The films were characterized with the UV-Vis-NIR Spectrometer, Scanning Electron Microscopy (SEM) and X-ray diffractometer (XRD). XRD results show that the films dried at 600 °C form anatase structure. From the spectroscopic studies, the sample shows electrochromic property.

Thin films deposited by femtosecond pulsed laser ablation of tungsten carbide

NASA Astrophysics Data System (ADS)

De Bonis, A.; Teghil, R.; Santagata, A.; Galasso, A.; Rau, J. V.

2012-09-01

Ultra-short Pulsed Laser Deposition has been applied to the production of thin films from a tungsten carbide target. The gaseous phase obtained by the laser ablation shows a very weak primary plume, in contrast with a very strong secondary one. The deposited films, investigated by Scanning Electron Microscopy, Atomic Force Microscopy, X-Ray Photoelectron Spectroscopy and X-Ray Diffraction, present a mixture of WC and other phases with lower carbon content. All films are amorphous, independently from the substrate temperature. The characteristics of the deposits have been explained in terms of thermal evaporation and cooling rate of molten particles ejected from the target.

Electrodeposition of polymer electrolyte in nanostructured electrodes for enhanced electrochemical performance of thin-film Li-ion microbatteries

NASA Astrophysics Data System (ADS)

Salian, Girish D.; Lebouin, Chrystelle; Demoulin, A.; Lepihin, M. S.; Maria, S.; Galeyeva, A. K.; Kurbatov, A. P.; Djenizian, Thierry

2017-02-01

We report that electrodeposition of polymer electrolyte in nanostructured electrodes has a strong influence on the electrochemical properties of thin-film Li-ion microbatteries. Electropolymerization of PMMA-PEG (polymethyl methacrylate-polyethylene glycol) was carried out on both the anode (self-supported titania nanotubes) and the cathode (porous LiNi0.5Mn1.5O4) by cyclic voltammetry and the resulting electrode-electrolyte interface was examined by scanning electron microscopy. The electrochemical characterizations performed by galvanostatic experiments reveal that the capacity values obtained at different C-rates are doubled when the electrodes are completely filled by the polymer electrolyte.

Quantitative Cryo-Scanning Transmission Electron Microscopy of Biological Materials.

PubMed

Elbaum, Michael

2018-05-11

Electron tomography provides a detailed view into the 3D structure of biological cells and tissues. Physical fixation by vitrification of the aqueous medium provides the most faithful preservation of biological specimens in the native, fully hydrated state. Cryo-microscopy is challenging, however, because of the sensitivity to electron irradiation and due to the weak electron scattering of organic material. Tomography is even more challenging because of the dependence on multiple exposures of the same area. Tomographic imaging is typically performed in wide-field transmission electron microscopy (TEM) mode with phase contrast generated by defocus. Scanning transmission electron microscopy (STEM) is an alternative mode based on detection of scattering from a focused probe beam, without imaging optics following the specimen. While careful configuration of the illumination and detectors is required to generate useful contrast, STEM circumvents the major restrictions of phase contrast TEM to very thin specimens and provides a signal that is more simply interpreted in terms of local composition and density. STEM has gained popularity in recent years for materials science. The extension of STEM to cryomicroscopy and tomography of cells and macromolecules is summarized herein. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

HAADF-STEM atom counting in atom probe tomography specimens: Towards quantitative correlative microscopy.

PubMed

Lefebvre, W; Hernandez-Maldonado, D; Moyon, F; Cuvilly, F; Vaudolon, C; Shinde, D; Vurpillot, F

2015-12-01

The geometry of atom probe tomography tips strongly differs from standard scanning transmission electron microscopy foils. Whereas the later are rather flat and thin (<20 nm), tips display a curved surface and a significantly larger thickness. As far as a correlative approach aims at analysing the same specimen by both techniques, it is mandatory to explore the limits and advantages imposed by the particular geometry of atom probe tomography specimens. Based on simulations (electron probe propagation and image simulations), the possibility to apply quantitative high angle annular dark field scanning transmission electron microscopy to of atom probe tomography specimens has been tested. The influence of electron probe convergence and the benefice of deconvolution of electron probe point spread function electron have been established. Atom counting in atom probe tomography specimens is for the first time reported in this present work. It is demonstrated that, based on single projections of high angle annular dark field imaging, significant quantitative information can be used as additional input for refining the data obtained by correlative analysis of the specimen in APT, therefore opening new perspectives in the field of atomic scale tomography. Copyright © 2015 Elsevier B.V. All rights reserved.

Scintillator for low accelerating voltage scanning electron microscopy imaging

NASA Astrophysics Data System (ADS)

Bowser, Christopher; Tzolov, Marian; Barbi, Nicholas

Scintillators are essential in detecting electrons in SEM. The conventional scintillators such as YAP and YAG have poor response at low accelerating voltages due to a top conductive layer of ITO or Al. We have developed a thin film ZnWO4 scintillator with high photoluminescence quantum efficiency of 60% with enough electrical conductivity to prevent charging. We are showing that the ZnWO4 films are effective in detecting electrons at low accelerating voltages. This makes it a good option for a top layer on crystalline scintillators and we have integrated ZnWO4 with YAP to explore the high response of YAP at high electron energies and the effective response of ZnWO4 at low electron energies. We will compare the spectral intensities over a range of accelerating voltages between 1 and 30kV between the conventional and coupled thin film scintillator. The results are interpreted using a simulation of the depth profile of the electron penetration in the scintillator using CASINO. We have verified the absence of charging by measuring the sum of the secondary and backscattered electron coefficients. We have built detectors with the combined scintillators and we will compare SEM images recorded simultaneously by conventional and ZnWO4-based scintillators.

The influence of C s/C c correction in analytical imaging and spectroscopy in scanning and transmission electron microscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zaluzec, Nestor J.

Aberration correction in scanning/transmission electron microscopy (S/TEM) owes much to the efforts of a small dedicated group of innovators. Leading that frontier has been Prof. Harald Rose. To date his leadership and dynamic personality has spearheaded our ability to leave behind many of the limitations imposed by spherical aberration (C s) in high resolution phase contrast imaging. Following shortly behind, has been the development of chromatic aberration correction (C c) which augments those accomplishments. In this study we will review and summarize how the combination of C s/C c technology enhances our ability to conduct hyperspectral imaging and spectroscopy inmore » today's and future computationally mediated experiments in both thin as well as realistic specimens in vacuo and during in-situ/environmental experiments.« less

The influence of C s/C c correction in analytical imaging and spectroscopy in scanning and transmission electron microscopy

DOE PAGES

Zaluzec, Nestor J.

2014-11-11

Aberration correction in scanning/transmission electron microscopy (S/TEM) owes much to the efforts of a small dedicated group of innovators. Leading that frontier has been Prof. Harald Rose. To date his leadership and dynamic personality has spearheaded our ability to leave behind many of the limitations imposed by spherical aberration (C s) in high resolution phase contrast imaging. Following shortly behind, has been the development of chromatic aberration correction (C c) which augments those accomplishments. In this study we will review and summarize how the combination of C s/C c technology enhances our ability to conduct hyperspectral imaging and spectroscopy inmore » today's and future computationally mediated experiments in both thin as well as realistic specimens in vacuo and during in-situ/environmental experiments.« less

Three-dimensional nanostructure determination from a large diffraction data set recorded using scanning electron nanodiffraction.

PubMed

Meng, Yifei; Zuo, Jian-Min

2016-09-01

A diffraction-based technique is developed for the determination of three-dimensional nanostructures. The technique employs high-resolution and low-dose scanning electron nanodiffraction (SEND) to acquire three-dimensional diffraction patterns, with the help of a special sample holder for large-angle rotation. Grains are identified in three-dimensional space based on crystal orientation and on reconstructed dark-field images from the recorded diffraction patterns. Application to a nanocrystalline TiN thin film shows that the three-dimensional morphology of columnar TiN grains of tens of nanometres in diameter can be reconstructed using an algebraic iterative algorithm under specified prior conditions, together with their crystallographic orientations. The principles can be extended to multiphase nanocrystalline materials as well. Thus, the tomographic SEND technique provides an effective and adaptive way of determining three-dimensional nanostructures.

Spectral, thermal and optical-electrical properties of the layer-by-layer deposited thin film of nano Zn(II)-8-hydroxy-5-nitrosoquinolate complex.

PubMed

Haggag, Sawsan M S; Farag, A A M; Abdelrafea, Mohamed

2013-06-01

Zinc(II)-8-hydroxy-5-nitrosoquinolate, [Zn(II)-(HNOQ)2], was synthesized and assembled as a deposited thin film of nano-metal complex by a rapid, direct, simple and efficient procedure based on layer-by-layer chemical deposition technique. Stoichiometric identification and structural characterization of [Zn(II)-(HNOQ)2] were confirmed by electron impact mass spectrometry (EI-MS) and Fourier Transform infrared spectroscopy (FT-IR). Surface morphology was studied by using a scanning electron microscope imaging (SEM) and the particle size was found to be in the range of 23-49 nm. Thermal stability of [Zn(II)-(HNOQ)2] was studied and the thermal parameters were evaluated using thermal gravimetric analysis (TGA). The current density-voltage measurements showed that the current flow is dominated by a space charge limited and influenced by traps under high bias. The optical properties of [Zn(II)-(HNOQ)2] thin films were found to exhibit two direct allowed transitions at 2.4 and 1.0 eV, respectively. Copyright © 2013 Elsevier B.V. All rights reserved.

Photo-induced self-cleaning and sterilizing activity of Sm3+ doped ZnO nanomaterials.

PubMed

Saif, M; Hafez, H; Nabeel, A I

2013-01-01

Highly active samarium doped zinc oxide self-cleaning and biocidal surfaces (x mol% Sm(3+)/ZnO where x=0, 1, 2 and 4 mol%) with crystalline porous structures were synthesized by hydrothermal method. Sm(3+)/ZnO thin films were characterized by X-ray diffraction (XRD), transmission electron microscope (TEM), scanning electron microscope (SEM), energy dispersive spectroscopic (EDS), UV-visible diffuse reflectance and fluorescence (FL) spectroscopy. The combination between doping and hydrothermal treatments significantly altered the morphology of ZnO into rod and plate-like nanoshapes structure and enhanced its absorption and emission of ultraviolet radiation. The photo-activity in term of quantitative determination of the active oxidative species (()OH) produced on the thin film surfaces was evaluated using fluorescent probe method. The results showed that, the hydrothermally treated 2.0 mol% Sm(3+)/ZnO film (S2) is the highly active one. The optical, structural, morphology and photo-activity properties of the highly active thin film (S2) make it promising surface for self-cleaning and sterilizing applications. Copyright © 2012 Elsevier Ltd. All rights reserved.

Influence of microstructure and surface topography on the electrical conductivity of Cu and Ag thin films obtained by magnetron sputtering

NASA Astrophysics Data System (ADS)

Polonyankin, D. A.; Blesman, A. I.; Postnikov, D. V.

2017-05-01

Conductive thin films formation by copper and silver magnetron sputtering is one of high technological areas for industrial production of solar energy converters, energy-saving coatings, flat panel displays and touch control panels because of their high electrical and optical properties. Surface roughness and porosity, average grain size, internal stresses, orientation and crystal lattice type, the crystallinity degree are the main physical properties of metal films affecting their electrical resistivity and conductivity. Depending on the film thickness, the dominant conduction mechanism can affect bulk conductivity due to the flow of electron gas, and grain boundary conductivity. The present investigation assesses the effect of microstructure and surface topography on the electrical conductivity of magnetron sputtered Cu and Ag thin films using X-ray diffraction analysis, scanning electron and laser interference microscopy. The highest specific conductivity (78.3 MS m-1 and 84.2 MS m-1, respectively, for copper and silver films at the thickness of 350 nm) were obtained with the minimum values of roughness and grain size as well as a high degree of lattice structuredness.

Properties of NiZnO Thin Films with Different Amounts of Al Doping

NASA Astrophysics Data System (ADS)

Kayani, Zohra N.; Fatima, Gulnaz; Zulfiqar, Bareera; Riaz, Saira; Naseem, Shahzad

2017-10-01

Transparent Al-doped NiZnO thin films have been fabricated by sol-gel dip coating and investigated using scanning electron microscopy, x-ray diffraction analysis, ultraviolet-visible-near infrared (UV-Vis-NIR) spectrophotometry, vibrating-sample magnetometry, and Fourier-transform infrared spectroscopy. The Al-doped NiZnO films consisted of ZnO hexagonal and α-Al2O3 rhombohedral phases as the Al incorporation was gradually increased from 1 at.% up to 3 at.%. A decrease in the optical bandgap from 3.90 eV to 3.09 eV was observed for films grown with Al content of 1 at.% to 2.5 at.%, but at 3 at.% Al, the bandgap increased to 3.87 eV. Optical transmittance of 96% was achieved for these transparent oxide films. Study of their magnetic properties revealed that increasing Al percentage resulted in enhanced ferromagnetism. The saturated magnetization increased with increasing Al percentage. The ferromagnetic properties of Al-doped NiZnO are mediated by electrons. The surface of the deposited thin films consisted of nanowires, nanorods, porous surface, and grains.

Time-lapse cinemicrography and scanning electron microscopy of platelet formation by megakaryocytes.

PubMed

Haller, C J; Radley, J M

1983-01-01

The surface architecture of megakaryocytes undergoing platelet formation in vitro has been examined by time-lapse cinemicrography and scanning electron microscopy. Fragments of mouse bone marrow were placed in culture medium and incubated at 37 degrees C. After several hours mature megakaryocytes migrated out of the marrow and some underwent shape changes so that they eventually appeared as a relatively small central body, housing the nucleus, from which emerged a number of thin processes which resembled platelet chains. Scanning electron microscopy showed that initially the megakaryocyte surface was ruffled but with development of processes it became smoother. Circumferential folds of small amplitude were found on the surface of developing constrictions which separated putative platelets. It is thought they may be associated with the mechanism of extension, but could have a role in establishing the topography of membrane components. Rupture of the chains and release of platelets was not observed; this permits the number of putative platelets formed by individual megakaryocytes to be determined. The putative platelets exhibited features common to circulating platelets when exposed to a glass surface including the development of pseudopodia and, eventually, flattening on to the surface.

Defect-mediated transport and electronic irradiation effect in individual domains of CVD-grown monolayer MoS 2

DOE PAGES

Durand, Corentin; Zhang, Xiaoguang; Fowlkes, Jason; ...

2015-01-16

We study the electrical transport properties of atomically thin individual crystalline grains of MoS 2 with four-probe scanning tunneling microscopy. The monolayer MoS 2 domains are synthesized by chemical vapor deposition on SiO 2/Si substrate. Temperature dependent measurements on conductance and mobility show that transport is dominated by an electron charge trapping and thermal release process with very low carrier density and mobility. The effects of electronic irradiation are examined by exposing the film to electron beam in the scanning electron microscope in an ultrahigh vacuum environment. The irradiation process is found to significantly affect the mobility and the carriermore » density of the material, with the conductance showing a peculiar time-dependent relaxation behavior. It is suggested that the presence of defects in active MoS 2 layer and dielectric layer create charge trapping sites, and a multiple trapping and thermal release process dictates the transport and mobility characteristics. The electron beam irradiation promotes the formation of defects and impact the electrical properties of MoS 2. Finally, our study reveals the important roles of defects and the electron beam irradiation effects in the electronic properties of atomic layers of MoS 2.« less

Evolution of structural and optical properties of rutile TiO2 thin films synthesized at room temperature by chemical bath deposition method

NASA Astrophysics Data System (ADS)

Mayabadi, A. H.; Waman, V. S.; Kamble, M. M.; Ghosh, S. S.; Gabhale, B. B.; Rondiya, S. R.; Rokade, A. V.; Khadtare, S. S.; Sathe, V. G.; Pathan, H. M.; Gosavi, S. W.; Jadkar, S. R.

2014-02-01

Nanocrystalline thin films of TiO2 were prepared on glass substrates from an aqueous solution of TiCl3 and NH4OH at room temperature using the simple and cost-effective chemical bath deposition (CBD) method. The influence of deposition time on structural, morphological and optical properties was systematically investigated. TiO2 transition from a mixed anatase-rutile phase to a pure rutile phase was revealed by low-angle XRD and Raman spectroscopy. Rutile phase formation was confirmed by FTIR spectroscopy. Scanning electron micrographs revealed that the multigrain structure of as-deposited TiO2 thin films was completely converted into semi-spherical nanoparticles. Optical studies showed that rutile thin films had a high absorption coefficient and a direct bandgap. The optical bandgap decreased slightly (3.29-3.07 eV) with increasing deposition time. The ease of deposition of rutile thin films at low temperature is useful for the fabrication of extremely thin absorber (ETA) solar cells, dye-sensitized solar cells, and gas sensors.

First observation of magnetoelectric effect in M-type hexaferrite thin films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mohebbi, Marjan; Ebnabbasi, Khabat; Vittoria, Carmine

2013-05-07

The magnetoelectric (ME) effect in M-type hexaferrite thin films is reported. Prior to this work, the ME effect in hexaferrite materials was observed only in bulk polycrystalline materials. Thin films of SrCo{sub 2}Ti{sub 2}Fe{sub 8}O{sub 19} were grown on sapphire (0001) using pulsed laser deposition. The thin films were characterized by X-ray diffractometer, scanning electron microscope, energy-dispersive spectroscopy, vibrating sample magnetometer, and ferromagnetic resonance. We measured saturation magnetization of 1250 G, g-factor of 2.66, and coercive field of 20 Oe for these magnetoelectric M-type hexaferrite thin films. The magnetoelectric effect was confirmed by monitoring the change rate in remanence magnetizationmore » with the application of DC voltage at room temperature and it gave rise to changes in remanence in the order of 12.8% with the application of only 1 V (DC voltage). We deduced a magnetoelectric coupling, {alpha}, of 6.07 Multiplication-Sign 10{sup -9} s m{sup -1} in SrCo{sub 2}Ti{sub 2}Fe{sub 8}O{sub 19} thin films.« less

LPCVD homoepitaxy of Si doped β-Ga2O3 thin films on (010) and (001) substrates

NASA Astrophysics Data System (ADS)

Rafique, Subrina; Karim, Md Rezaul; Johnson, Jared M.; Hwang, Jinwoo; Zhao, Hongping

2018-01-01

This paper presents the homoepitaxy of Si-doped β-Ga2O3 thin films on semi-insulating (010) and (001) Ga2O3 substrates via low pressure chemical vapor deposition with a growth rate of ≥1 μm/h. Both high resolution scanning transmission electron microscopy and X-ray diffraction measurements demonstrated high crystalline quality homoepitaxial growth of these thin films. Atomic resolution STEM images of the as-grown β-Ga2O3 thin films on (010) and (001) substrates show high quality material without extended defects or dislocations. The charge carrier transport properties of the as-grown Si-doped β-Ga2O3 thin films were characterized by the temperature dependent Hall measurement using van der Pauw patterns. The room temperature carrier concentrations achieved for the (010) and (001) homoepitaxial thin films were ˜1.2 × 1018 cm-3 and ˜9.5 × 1017 cm-3 with mobilities of ˜72 cm2/V s and ˜42 cm2/V s, respectively.

Dewetting of thin films on flexible substrates via direct-write laser exposure

NASA Astrophysics Data System (ADS)

Ferrer, Anthony Jesus

Microelectromechanical systems (MEMS) have enabled a wide variety of technologies both in the consumer space and in industrial/research areas. At the market level, such devices advance by the invention and innovation of production techniques. Additionally, there has been increased demand for flexible versions of such MEMS devices. Thin film patterning, represents a key technology for the realization of such flexible electronics. Patterns and methods that can be directly written into the thin film allow for design modification on the fly with the need for harsh chemicals and long etching steps. Laser-induced dewetting has the potential to create patterns in thin films at both the microscopic and nanoscopic level without wasting deposited material. This thesis presents the first demonstration of high-speed direct-write patterning of metallic thin films that uses a laser-induced dewetting phenomenon to prevent material loss. The ability to build film material with this technique is explored using various scanning geometries. Finally, demonstrations of direct-write dewetting of a variety of thin films will be presented with special consideration for high melting point metals deposited upon polymer substrates.

Characterization of stable, electroactive protein cage/synthetic polymer multilayer thin films prepared by layer-by-layer assembly

NASA Astrophysics Data System (ADS)

Uto, Koichiro; Yamamoto, Kazuya; Kishimoto, Naoko; Muraoka, Masahiro; Aoyagi, Takao; Yamashita, Ichiro

2013-04-01

We have fabricated electroactive multilayer thin films containing ferritin protein cages. The multilayer thin films were prepared on a solid substrate by the alternate electrostatic adsorption of (apo)ferritin and poly( N-isopropylacrylamide- co-2-carboxyisopropylacrylamide) (NIPAAm- co-CIPAAm) in pH 3.5 acetate buffer solution. The assembly process was monitored using a quartz crystal microbalance. The (apo)ferritin/poly(NIPAAm- co-CIPAAm) multilayer thin films were then cross-linked using a water-soluble carbodiimide, 1-[3-(dimethylamino)propyl]-3-ethylcarbodiimide. The cross-linked films were stable under a variety of conditions. The surface morphology and thickness of the multilayer thin films were characterized by atomic force microscopy, and the ferritin iron cores were observed by scanning electron microscopy to confirm the assembly mechanism. Cyclic voltammetry measurements showed different electrochemical properties for the cross-linked ferritin and apoferritin multilayer thin films, and the effect of stability of the multilayer film on its electrochemical properties was also examined. Our method for constructing multilayer films containing protein cages is expected to be useful in building more complex functional inorganic nanostructures.

Integration of Ion Implantation with Scanning ProbeAlignment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Persaud, A.; Rangelow, I.W.; Schenkel, T.

We describe a scanning probe instrument which integrates ion beams with imaging and alignment functions of a piezo resistive scanning probe in high vacuum. Energetic ions (1 to a few hundred keV) are transported through holes in scanning probe tips [1]. Holes and imaging tips are formed by Focused Ion Beam (FIB) drilling and ion beam assisted thin film deposition. Transport of single ions can be monitored through detection of secondary electrons from highly charged dopant ions (e. g., Bi{sup 45+}) enabling single atom device formation. Fig. 1 shows SEM images of a scanning probe tip formed by ion beammore » assisted Pt deposition in a dual beam FIB. Ion beam collimating apertures are drilled through the silicon cantilever with a thickness of 5 {micro}m. Aspect ratio limitations preclude the direct drilling of holes with diameters well below 1 {micro}m, and smaller hole diameters are achieved through local thin film deposition [2]. The hole in Fig. 1 was reduced from 2 {micro}m to a residual opening of about 300 nm. Fig. 2 shows an in situ scanning probe image of an alignment dot pattern taken with the tip from Fig. 1. Transport of energetic ions through the aperture in the scanning probe tip allows formation of arbitrary implant patterns. In the example shown in Fig. 2 (right), a 30 nm thick PMMA resist layer on silicon was exposed to 7 keV Ar{sup 2+} ions with an equivalent dose of 10{sup 14} ions/cm{sup 2} to form the LBL logo. An exciting goal of this approach is the placement of single dopant ions into precise locations for integration of single atom devices, such as donor spin based quantum computers [3, 4]. In Fig. 3, we show a section of a micron size dot area exposed to a low dose (10{sup 11}/cm{sup 2}) of high charge state dopant ions. The Bi{sup 45+} ions (200 keV) were extracted from a low emittance highly charged ions source [5]. The potential energy of B{sup 45+}, i. e., the sum of the binding energies required to remove the electrons, amounts to 36 keV. This energy is deposited within {approx}10 fs when an ion impinges on a target. The highly localized energy deposition results in efficient resist exposure, and is associated with strongly enhanced secondary electron emission, which allows monitoring of single ion impacts [4]. The ex situ scanning probe image with line scan in Fig. 3 shows a single ion impact site in PMMA (after standard development). In our presentation, we will discuss resolution requirements for ion placement in prototype quantum computer structures [3] with respect to resolution limiting factors in ion implantation with scanning probe alignment.« less

Structural, Optical, and Vibrational Properties of ZnO Microrods Deposited on Silicon Substrate

NASA Astrophysics Data System (ADS)

Lahlouh, Bashar I.; Ikhmayies, Shadia J.; Juwhari, Hassan K.

2018-03-01

Zinc oxide (ZnO) microrod films deposited by spray pyrolysis on silicon substrate at 350 ± 5°C have been studied and evaluated, and compared with thin films deposited by electron beam to confirm the identity of the studied samples. The films were characterized using different techniques. The microrod structure was studied and confirmed by scanning electron microscopy. Fourier-transform infrared (FTIR) spectroscopy and x-ray diffraction analysis confirmed successful deposition of ZnO thin films with the expected wurtzite structure. Reflectance data showed a substantial drop across the whole studied wavelength range. The photoluminescence (PL) spectra of the studied samples showed a peak at ˜ 360 nm, representing a signature of ZnO. The shift in the PL peak position is due to defects and other species present in the films, as confirmed by FTIR and energy-dispersive x-ray spectroscopy results.

Dimensional crossover of the charge density wave transition in thin exfoliated VSe2

NASA Astrophysics Data System (ADS)

Pásztor, Árpád; Scarfato, Alessandro; Barreteau, Céline; Giannini, Enrico; Renner, Christoph

2017-12-01

Isolating single unit-cell thin layers from the bulk matrix of layered compounds offers tremendous opportunities to design novel functional electronic materials. However, a comprehensive thickness dependence study is paramount to harness the electronic properties of such atomic foils and their stacking into synthetic heterostructures. Here we show that a dimensional crossover and quantum confinement with reducing thickness result in a striking non-monotonic evolution of the charge density wave transition temperature in VSe2. Our conclusion is drawn from a direct derivation of the local order parameter and transition temperature from the real space charge modulation amplitude imaged by scanning tunnelling microscopy. This study lifts the disagreement of previous independent transport measurements. We find that thickness can be a non-trivial tuning parameter and demonstrate the importance of considering a finite thickness range to accurately characterize its influence.

Transport properties of ultra-thin VO{sub 2} films on (001) TiO{sub 2} grown by reactive molecular-beam epitaxy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Paik, Hanjong; Tashman, Joshua W.; Moyer, Jarrett A.

2015-10-19

We report the growth of (001)-oriented VO{sub 2} films as thin as 1.5 nm with abrupt and reproducible metal-insulator transitions (MIT) without a capping layer. Limitations to the growth of thinner films with sharp MITs are discussed, including the Volmer-Weber type growth mode due to the high energy of the (001) VO{sub 2} surface. Another key limitation is interdiffusion with the (001) TiO{sub 2} substrate, which we quantify using low angle annular dark field scanning transmission electron microscopy in conjunction with electron energy loss spectroscopy. We find that controlling island coalescence on the (001) surface and minimization of cation interdiffusion bymore » using a low growth temperature followed by a brief anneal at higher temperature are crucial for realizing ultrathin VO{sub 2} films with abrupt MIT behavior.« less

Structural “ δ Doping” to Control Local Magnetization in Isovalent Oxide Heterostructures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Moon, E. J.; He, Q.; Ghosh, S.

Modulation and δ-doping strategies, in which atomically thin layers of charged dopants are precisely deposited within a heterostructure, have played enabling roles in the discovery of new physical behavior in electronic materials. Here in this paper, we demonstrate a purely structural “δ-doping” strategy in complex oxide heterostructures, in which atomically thin manganite layers are inserted into an isovalent manganite host, thereby modifying the local rotations of corner-connected MnO 6 octahedra. Combining scanning transmission electron microscopy, polarized neutron reflectometry, and density functional theory, we reveal how local magnetic exchange interactions are enhanced within the spatially confined regions of suppressed octahedral rotations.more » Finally, the combined experimental and theoretical results illustrate the potential to utilize noncharge-based approaches to “doping” in order to enhance or suppress functional properties within spatially confined regions of oxide heterostructures.« less

Structural “ δ Doping” to Control Local Magnetization in Isovalent Oxide Heterostructures

DOE PAGES

Moon, E. J.; He, Q.; Ghosh, S.; ...

2017-11-08

Modulation and δ-doping strategies, in which atomically thin layers of charged dopants are precisely deposited within a heterostructure, have played enabling roles in the discovery of new physical behavior in electronic materials. Here in this paper, we demonstrate a purely structural “δ-doping” strategy in complex oxide heterostructures, in which atomically thin manganite layers are inserted into an isovalent manganite host, thereby modifying the local rotations of corner-connected MnO 6 octahedra. Combining scanning transmission electron microscopy, polarized neutron reflectometry, and density functional theory, we reveal how local magnetic exchange interactions are enhanced within the spatially confined regions of suppressed octahedral rotations.more » Finally, the combined experimental and theoretical results illustrate the potential to utilize noncharge-based approaches to “doping” in order to enhance or suppress functional properties within spatially confined regions of oxide heterostructures.« less

Imaging and elemental mapping of biological specimens with a dual-EDS dedicated scanning transmission electron microscope.

PubMed

Wu, J S; Kim, A M; Bleher, R; Myers, B D; Marvin, R G; Inada, H; Nakamura, K; Zhang, X F; Roth, E; Li, S Y; Woodruff, T K; O'Halloran, T V; Dravid, Vinayak P

2013-05-01

A dedicated analytical scanning transmission electron microscope (STEM) with dual energy dispersive spectroscopy (EDS) detectors has been designed for complementary high performance imaging as well as high sensitivity elemental analysis and mapping of biological structures. The performance of this new design, based on a Hitachi HD-2300A model, was evaluated using a variety of biological specimens. With three imaging detectors, both the surface and internal structure of cells can be examined simultaneously. The whole-cell elemental mapping, especially of heavier metal species that have low cross-section for electron energy loss spectroscopy (EELS), can be faithfully obtained. Optimization of STEM imaging conditions is applied to thick sections as well as thin sections of biological cells under low-dose conditions at room and cryogenic temperatures. Such multimodal capabilities applied to soft/biological structures usher a new era for analytical studies in biological systems. Copyright © 2013 Elsevier B.V. All rights reserved.

Investigation of the structural, surface, optical and electrical properties of the Indium doped CuxO thin films deposited by a thermionic vacuum arc

NASA Astrophysics Data System (ADS)

Musaoğlu, Caner; Pat, Suat; Özen, Soner; Korkmaz, Şadan; Mohammadigharehbagh, Reza

2018-03-01

In this study, investigation of some physical properties of In-doped CuxO thin films onto amorphous glass substrates were done. The thin films were depsoied by thermionic vacuum arc technique (TVA). TVA technique gives a thin film with lower precursor impurity according to the other chemical and physical depsoition methods. The microstructural properties of the produced thin films was determined by x-ray diffraction device (XRD). The thickness values were measured as to be 30 nm and 60 nm, respectively. The miller indices of the thin films’ crystalline planes were determined as to be Cu (111), CuO (\\bar{1} 12), CuInO2 (107) and Cu2O (200), Cu (111), CuO (\\bar{1} 12), CuO (\\bar{2} 02), CuInO2 (015) for sample C1 and C2, respectively. The produced In-doped CuO thin films are in polycrystalline structure. The surface properties of produced In doped CuO thin films were determined by using an atomic force microscope (AFM) and field emission scanning electron microscope (FESEM) tools. The optical properties of the In doped CuO thin films were determined by UV–vis spectrophotometer, interferometer, and photoluminescence devices. p-type semiconductor thin film was obtained by TVA depsoition.

Nonlinear optical characterization of ZnS thin film synthesized by chemical spray pyrolysis method

NASA Astrophysics Data System (ADS)

G, Sreeja V.; V, Sabitha P.; Anila, E. I.; R, Reshmi; John, Manu Punnan; Radhakrishnan, P.

2014-10-01

ZnS thin film was prepared by Chemical Spray Pyrolysis (CSP) method. The sample was characterized by X-ray diffraction method and Z scan technique. XRD pattern showed that ZnS thin film has hexagonal structure with an average size of about 5.6nm. The nonlinear optical properties of ZnS thin film was studied by open aperture Z-Scan technique using Q-switched Nd-Yag Laser at 532nm. The Z-scan plot showed that the investigated ZnS thin film has saturable absorption behavior. The nonlinear absorption coefficient and saturation intensity were also estimated.

Atomic-scale distortions and temperature-dependent large pseudogap in thin films of the parent iron-chalcogenide superconductor Fe1+y Te

NASA Astrophysics Data System (ADS)

Gerbi, Andrea; Buzio, Renato; Kawale, Shrikant; Bellingeri, Emilio; Martinelli, Alberto; Bernini, Cristina; Tresca, Cesare; Capone, Massimo; Profeta, Gianni; Ferdeghini, Carlo

2017-12-01

We investigate with scanning tunneling microscopy/spectroscopy (STM/STS) and density functional theory (DFT) calculations the surface structures and the electronic properties of Fe1+y Te thin films grown by pulsed laser deposition. Contrary to the regular arrangement of antiferromagnetic nanostripes previously reported on cleaved single-crystal samples, the surface of Fe1+y Te thin films displays a peculiar distribution of spatially inhomogeneous nanostripes. Both STM and DFT calculations show the bias-dependent nature of such features and support the interpretation of spin-polarized tunneling between the FeTe surface and an unintentionally magnetized tip. In addition, the spatial inhomogeneity is interpreted as a purely electronic effect related to changes in hybridization and Fe-Fe bond length driven by local variations in the concentration of excess interstitial Fe cations. Unexpectedly, the surface density of states measured by STS strongly evolves with temperature in close proximity to the antiferromagnetic-paramagnetic first-order transition, and reveals a large pseudogap of 180-250 meV at about 50-65 K. We believe that in this temperature range a phase transition takes place, and the system orders and locks into particular combinations of orbitals and spins because of the interplay between excess interstitial magnetic Fe and strongly correlated d-electrons.

Direct observation of anti-phase boundaries in heteroepitaxy of GaSb thin films grown on Si(001) by transmission electron microscopy

NASA Astrophysics Data System (ADS)

Woo, S. Y.; Hosseini Vajargah, S.; Ghanad-Tavakoli, S.; Kleiman, R. N.; Botton, G. A.

2012-10-01

Unambiguous identification of anti-phase boundaries (APBs) in heteroepitaxial films of GaSb grown on Si has been so far elusive. In this work, we present conventional transmission electron microscopy (TEM) diffraction contrast imaging using superlattice reflections, in conjunction with convergent beam electron diffraction analysis, to determine a change in polarity across APBs in order to confirm the presence of anti-phase disorder. In-depth analysis of anti-phase disorder is further supported with atomic resolution high-angle annular dark-field scanning transmission electron microscopy. The nature of APBs in GaSb is further elucidated by a comparison to previous results for GaAs epilayers grown on Si.

Correlative multi-scale characterization of a fine grained Nd-Fe-B sintered magnet.

PubMed

Sasaki, T T; Ohkubo, T; Hono, K; Une, Y; Sagawa, M

2013-09-01

The Nd-rich phases in pressless processed fine grained Nd-Fe-B sintered magnets have been characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and three dimensional atom probe tomography (3DAP). The combination of the backscattered electron (BSE) and in-lens secondary electron (IL-SE) images in SEM led to an unambiguous identification of four types of Nd-rich phases, NdOx, Ia3 type phase, which is isostructural to Nd₂O₃, dhcp-Nd and Nd₁Fe₄B₄. In addition, the 3DAP analysis of thin Nd-rich grain boundary layer indicate that the coercivity has a close correlation with the chemistry of the grain boundary phase. Copyright © 2013 Elsevier B.V. All rights reserved.

Determination of dispersive optical constants of nanocrystalline CdSe (nc-CdSe) thin films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sharma, Kriti; Al-Kabbi, Alaa S.; Saini, G.S.S.

2012-06-15

Highlights: ► nc-CdSe thin films are prepared by thermal vacuum evaporation technique. ► TEM analysis shows NCs are spherical in shape. ► XRD reveals the hexagonal (wurtzite) crystal structure of nc-CdSe thin films. ► The direct optical bandgap of nc-CdSe is 2.25 eV in contrast to bulk (1.7 eV). ► Dispersion of refractive index is discussed in terms of Wemple–DiDomenico single oscillator model. -- Abstract: The nanocrystalline thin films of CdSe are prepared by thermal evaporation technique at room temperature. These thin films are characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), X-raymore » diffraction (XRD) and photoluminescence spectroscopy (PL). The transmission spectra are recorded in the transmission range 400–3300 nm for nc-CdSe thin films. Transmittance measurements are used to calculate the refractive index (n) and absorption coefficient (α) using Swanepoel's method. The optical band gap (E{sub g}{sup opt}) has been determined from the absorption coefficient values using Tauc's procedure. The optical constants such as extinction coefficient (k), real (ε{sub 1}) and imaginary (ε{sub 2}) dielectric constants, dielectric loss (tan δ), optical conductivity (σ{sub opt}), Urbach energy (E{sub u}) and steepness parameter (σ) are also calculated for nc-CdSe thin films. The normal dispersion of refractive index is described using Wemple–DiDomenico single-oscillator model. Refractive index dispersion is further analysed to calculate lattice dielectric constant (ε{sub L}).« less

Micropaleontological studies of lunar and terrestrial precambrian materials

NASA Technical Reports Server (NTRS)

Schope, J. W.

1974-01-01

Optical microscopic and scanning electron microscopic studies of rock chips and dust returned by Apollo 14, 15, 16, and 17 are analyzed along with optical microscopic studies of petrographic thin sections of breccias and basalts returned by Apollo 14, 15, and 16. Results show no evidence of modern or fossil lunar organisms. The lunar surface is now, and apparently has been throughout the geologic past, inimical to known biologic systems.

Substrate decomposition in galvanic displacement reaction: Contrast between gold and silver nanoparticle formation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ghosh, Tapas; Satpati, Biswarup, E-mail: biswarup.satpati@saha.ac.in; Kabiraj, D.

We have investigated substrate decomposition during formation of silver and gold nanoparticles in galvanic displacement reaction on germanium surfaces. Silver and gold nanoparticles were synthesized by electroless deposition on sputter coated germanium thin film (∼ 200 nm) grown initially on silicon substrate. The nanoparticles formation and the substrate corrosion were studied using scanning transmission electron microscopy (STEM) and the energy dispersive X-ray (EDX) spectroscopy.

Enhancement of the Optoelectronic Properties of PEDOT: PSS-PbS Nanoparticles Composite Thin Films Through Nanoparticles' Capping Ligand Exchange

NASA Astrophysics Data System (ADS)

García-Gutiérrez, Diana F.; Hernández-Casillas, Laura P.; Sepúlveda-Guzmán, Selene; Vazquez-Rodriguez, Sofia; García-Gutiérrez, Domingo I.

2018-02-01

The influence of the capping ligand on nanoparticles' optical and electronic properties is a topic of great interest currently being investigated by several research groups in different countries. In the present study, PbS nanoparticles originally synthesized with oleic acid, myristic acid and hexanoic acid underwent a ligand exchange process to replace the original carboxylic acid for uc(l)-cysteine as the capping layer, and were thoroughly characterized by means of transmission electron microscopy and its related techniques, such as energy dispersive x-ray spectroscopy and scanning-transmission electron microscopy, and Fourier transform infrared, Raman and x-ray photoelectron spectroscopy. Afterwards, these PbS nanoparticles were dispersed into a poly(3,4-ethylenedioxythiophene):poly(styrenesulfonic acid) (PEDOT:PSS) matrix to fabricate a composite thin film which displayed the optical absorption properties of the PbS nanoparticles and the electrical transport properties of the PEDOT:PSS matrix, in order to evaluate the impact of the nanoparticles' capping ligand on the optoelectronic properties of the fabricated composite thin films. Composite thin films with PbS nanoparticles showing uc(l)-cysteine as the capping layer displayed clear photoresponse and a threefold increment in their conductivities compared to pristine PEDOT:PSS. The properties of PEDOT:PSS, known as a hole transport layer in most organic photovoltaic devices, were enhanced by adding PbS nanoparticles with different capping ligands, producing a promising composite material for optoelectronic applications by proper selection of the nanoparticles' capping layer.

Scanning probes for lithography: Manipulation and devices

NASA Astrophysics Data System (ADS)

Rolandi, Marco

2005-11-01

Scanning probes are relatively low cost equipment that can push the limit of lithography in the nanometer range, with the advantages of high resolution, accuracy in the positioning of the overlayers and no proximity aberrations. We have developed three novel scanning probe lithography (SPL) resists based on thin films of Titanium, Molybdenum and Tungsten and we have manipulated single walled carbon nanotubes using the sharp tip of an atomic force microscope (AFM) for the fabrication of nanostructures. A dendrimer-passivated Ti film was imaged in the positive and the negative tone using SPL. This is the first example of SPL imaging in both tones using a unique resist. Positive tone patterning was obtained by locally scribing the dendrimer molecules and subsequent acid etch of the deprotected Ti film. Local anodic oxidation transforms Ti into TiO2 and deposits a thin layer of amorphous carbon on the patterned areas. This is very resistive to base etch and affords negative tone imaging of the Ti surface. Molybdenum and Tungsten were patterned using local anodic oxidation. This scheme is particularly flexible thanks to the solubility in water of the fully oxidized states of the two metals. We will present the facile fabrication of several nanostructures such as of trenches, dots wires and nanoelectrodes and show the potential of this scheme for competing with conventional lithographic techniques based on radiation. Quasi one dimensional electrodes for molecular electronics applications were also fabricated by creating nanogaps in single walled carbon nanotubes. The tubes, connected to microscopic contacts, were controllably cut via local anodic oxidation using the tip of the AFM. This technique leads to nanoscopic carboxyl terminated wires to which organic molecules can be linked using covalent chemistry. This geometry is particularly useful for the high gate efficiency without the need of a thin gate dielectric and the stability of the junction. Room temperature and low temperature measurements were performed and show single electron transistor behavior for the molecular junction.

Unexpected surface implanted layer in static random access memory devices observed by microwave impedance microscope

NASA Astrophysics Data System (ADS)

Kundhikanjana, W.; Yang, Y.; Tanga, Q.; Zhang, K.; Lai, K.; Ma, Y.; Kelly, M. A.; Li, X. X.; Shen, Z.-X.

2013-02-01

Real-space mapping of doping concentration in semiconductor devices is of great importance for the microelectronics industry. In this work, a scanning microwave impedance microscope (MIM) is employed to resolve the local conductivity distribution of a static random access memory sample. The MIM electronics can also be adjusted to the scanning capacitance microscopy (SCM) mode, allowing both measurements on the same region. Interestingly, while the conventional SCM images match the nominal device structure, the MIM results display certain unexpected features, which originate from a thin layer of the dopant ions penetrating through the protective layers during the heavy implantation steps.

The saturable absorption and reverse saturable absorption properties of Cu doped zinc oxide thin films

NASA Astrophysics Data System (ADS)

Yao, Cheng-Bao; Wen, Xin; Li, Qiang-Hua; Yan, Xiao-Yan; Li, Jin; Zhang, Ke-Xin; Sun, Wen-Jun; Bai, Li-Na; Yang, Shou-Bin

2017-03-01

We present the structure and nonlinear absorption (NLA) properties of Cu-doped ZnO (CZO) films prepared by magnetron sputtering. The films were characterized using X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. The results show that the CZO films can maintain a wurtzite structure. Furthermore, the open-aperture (OA) Z-scan measurements of the film were carried out by nanosecond laser pulse. A transition from saturable absorption (SA) to reverse saturable absorption (RSA) was observed as the excitation intensity increasing. With good excellent nonlinear optical coefficient, the samples were expected to be the potential applications in optical devices.

Histology and ultrastructure of picosecond laser intrastromal photorefractive keratectomy (ISPRK)

NASA Astrophysics Data System (ADS)

Krueger, Ronald R.; Quantock, Andrew J.; Ito, Mitsutoshi; Assil, Kerry K.; Schanzlin, David J.

1995-05-01

Picosecond intrastromal ablation is currently under investigation as a new minimally invasive way of correcting refractive error. When the laser pulses are placed in an expanding spiral pattern along a lamellar plane, the technique is called intrastromal photorefractive keratectomy (ISPRK). We performed ISPRK on six human eye bank eyes. Thirty picosecond pulses at 1000 Hz and 20 - 25 (mu) J per pulse were separated by 15 microns. A total of 3 layers were placed in the anterior stroma separated by 15 microns. The eyes were then preserved and sectioned for light, scanning and transmission electron microscopy. Light and scanning electron microscopy reveals that picosecond intrastromal ablation using an ISPRK pattern demonstrates multiple, coalescing intrastromal cavities oriented parallel to the corneal surface. These cavities possess a smooth appearing inner wall. Using transmission electron microscopy, we noticed tissue loss surrounding some cavities with collagen fibril termination and thinning of collagen lamella. Other cavities we formed by separation of lamella with little evidence of tissue loss. A pseudomembrane lines the edge of some cavities. Although underlying tissue disruption was occasionally seen along the border of a cavity in no case was there any evidence of thermal damage or tissue necrosis. Ablation and loss of tissue in ISPRK results in nonthermal microscopic corneal thinning around some cavities whereas others demonstrate only lamellar separation. Alternative patterns and energy parameters should be investigated to bring this technology to its full potential in refractive surgery.

Simple technique for high-throughput marking of distinguishable micro-areas for microscopy.

PubMed

Henrichs, Leonard F; Chen, L I; Bell, Andrew J

2016-04-01

Today's (nano)-functional materials, usually exhibiting complex physical properties require local investigation with different microscopy techniques covering different physical aspects such as dipolar and magnetic structure. However, often these must be employed on the very same sample position to be able to truly correlate those different information and corresponding properties. This can be very challenging if not impossible especially when samples lack prominent features for orientation. Here, we present a simple but effective method to mark hundreds of approximately 15×15 μm sample areas at one time by using a commercial transmission electron microscopy grid as shadow mask in combination with thin-film deposition. Areas can be easily distinguished when using a reference or finder grid structure as shadow mask. We show that the method is suitable to combine many techniques such as light microscopy, scanning probe microscopy and scanning electron microscopy. Furthermore, we find that best results are achieved when depositing aluminium on a flat sample surface using electron-beam evaporation which ensures good line-of-sight deposition. This inexpensive high-throughput method has several advantageous over other marking techniques such as focused ion-beam processing especially when batch processing or marking of many areas is required. Nevertheless, the technique could be particularly valuable, when used in junction with, for example focused ion-beam sectioning to obtain a thin lamellar of a particular pre-selected area. © 2015 The Authors Journal of Microscopy © 2015 Royal Microscopical Society.

"Un-annealed and Annealed Pd Ultra-Thin Film on SiC Characterized by Scanning Probe Microscopy and X-ray Photoelectron Spectroscopy"

NASA Technical Reports Server (NTRS)

Lu, W. J.; Shi, D. T.; Elshot, K.; Bryant, E.; Lafate, K.; Chen, H.; Burger, A.; Collins, W. E.

1998-01-01

Pd/SiC has been used as a hydrogen and a hydrocarbon gas sensor operated at high temperature. UHV (Ultra High Vacuum)-Scanning Tunneling Microscopy (STM), Atomic Force Microscopy (AFM) and X-ray Photoelectron Spectroscopy (XPS) techniques were applied to study the relationship between the morphology and chemical compositions for Pd ultra-thin films on SiC (less than 30 angstroms) at different annealing temperatures. Pd ultra-thin film on 6H-SiC was prepared by the RF sputtering method. The morphology from UHV-STM and AFM shows that the Pd thin film was well deposited on SiC substrate, and the Pd was partially aggregated to round shaped participates at an annealing temperature of 300 C. At 400 C, the amount of surface participates decreases, and some strap shape participates appear. From XPS, Pd2Si was formed on the surface after annealing at 300 C, and all Pd reacted with SiC to form Pd2Si after annealing at 400 C. The intensity of the XPS Pd peak decreases enormously at 400 C. The Pd film diffused into SiC, and the Schottky barrier height has almost no changes. The work shows the Pd sicilides/SiC have the same electronic properties with Pd/SiC, and explains why the Pd/SiC sensor still responds to hydrogen at high operating temperatures.

Sensitive power compensated scanning calorimeter for analysis of phase transformations in small samples

NASA Astrophysics Data System (ADS)

Lopeandía, A. F.; Cerdó, L. l.; Clavaguera-Mora, M. T.; Arana, Leonel R.; Jensen, K. F.; Muñoz, F. J.; Rodríguez-Viejo, J.

2005-06-01

We have designed and developed a sensitive scanning calorimeter for use with microgram or submicrogram, thin film, or powder samples. Semiconductor processing techniques are used to fabricate membrane based microreactors with a small heat capacity of the addenda, 120nJ/K at room temperature. At heating rates below 10K/s the heat released or absorbed by the sample during a given transformation is compensated through a resistive Pt heater by a digital controller so that the calorimeter works as a power compensated device. Its use and dynamic sensitivity is demonstrated by analyzing the melting behavior of thin films of indium and high density polyethylene. Melting enthalpies in the range of 40-250μJ for sample masses on the order of 1.5μg have been measured with accuracy better than 5% at heating rates ˜0.2K/s. The signal-to-noise ratio, limited by the electronic setup, is 200nW.

A comparative review of optical surface contamination assessment techniques

NASA Technical Reports Server (NTRS)

Heaney, James B.

1987-01-01

This paper will review the relative sensitivities and practicalities of the common surface analytical methods that are used to detect and identify unwelcome adsorbants on optical surfaces. The compared methods include visual inspection, simple reflectometry and transmissiometry, ellipsometry, infrared absorption and attenuated total reflectance spectroscopy (ATR), Auger electron spectroscopy (AES), scanning electron microscopy (SEM), secondary ion mass spectrometry (SIMS), and mass accretion determined by quartz crystal microbalance (QCM). The discussion is biased toward those methods that apply optical thin film analytical techniques to spacecraft optical contamination problems. Examples are cited from both ground based and in-orbit experiments.

Thermal and Optical Modulation of the Carrier Mobility in OTFTs Based on an Azo-anthracene Liquid Crystal Organic Semiconductor.

PubMed

Chen, Yantong; Li, Chao; Xu, Xiuru; Liu, Ming; He, Yaowu; Murtaza, Imran; Zhang, Dongwei; Yao, Chao; Wang, Yongfeng; Meng, Hong

2017-03-01

One of the most striking features of organic semiconductors compared with their corresponding inorganic counterparts is their molecular diversity. The major challenge in organic semiconductor material technology is creating molecular structural motifs to develop multifunctional materials in order to achieve the desired functionalities yet to optimize the specific device performance. Azo-compounds, because of their special photoresponsive property, have attracted extensive interest in photonic and optoelectronic applications; if incorporated wisely in the organic semiconductor groups, they can be innovatively utilized in advanced smart electronic applications, where thermal and photo modulation is applied to tune the electronic properties. On the basis of this aspiration, a novel azo-functionalized liquid crystal semiconductor material, (E)-1-(4-(anthracen-2-yl)phenyl)-2-(4-(decyloxy)phenyl)diazene (APDPD), is designed and synthesized for application in organic thin-film transistors (OTFTs). The UV-vis spectra of APDPD exhibit reversible photoisomerizaton upon photoexcitation, and the thin films of APDPD show a long-range orientational order based on its liquid crystal phase. The performance of OTFTs based on this material as well as the effects of thermal treatment and UV-irradiation on mobility are investigated. The molecular structure, stability of the material, and morphology of the thin films are characterized by thermal gravimetric analysis (TGA), polarizing optical microscopy (POM), (differential scanning calorimetry (DSC), UV-vis spectroscopy, atomic force microscopy (AFM), and scanning tunneling microscopy (STM). This study reveals that our new material has the potential to be applied in optical sensors, memories, logic circuits, and functional switches.

[Preparation and transmissivity of ZnS nanocolumn thin films with glancing angle deposition technology].

PubMed

Lu, Li-Fang; Xu, Zheng; Zhang, Fu-Jun; Zhao, Su-Ling; Song, Dan-Dan; Li, Jun-Ming; Wang, Yong-Sheng; Xu, Xu-Rong

2010-02-01

Nanocrystalline ZnS thin films were fabricated by glancing angle deposition (GLAD) technology in an electron beam evaporation system. Deposition was carried out in the custom vacuum chamber at a base pressure 3 x 10(-4) Pa, and the deposition rate was fixed at 0.2 nm x s(-1). ZnS films were deposited on pieces of indium tin oxide (ITO) substrates when the oblique angle of the substrate relative to the incoming molecular flux was set to 0 degrees, 80 degrees and 85 degrees off the substrate normal respectively. X-ray diffraction (XRD) spectra and scanning electron microscope (SEM) images showed that ZnS nanocrystalline films were formed on the substrates at different oblique angle, but the nanocolumn structure was only formed under the situation of alpha = 80 degrees and 85 degrees. The dynamics during the deposition process of the ZnS films at alpha = 0 degrees, 80 degrees and 85 degrees was analyzed. The transmitted spectra of ZnS thin films deposited on ITO substrates showed that the ZnS nanocolumn thin films could enhance the transmissivity in visible range. The ZnS nanocolumn could be used into electroluminescence device, and it would enhance the luminous efficiency of the device.

Photosensitive space charge limited current in screen printed CdTe thin films

NASA Astrophysics Data System (ADS)

Vyas, C. U.; Pataniya, Pratik; Zankat, Chetan K.; Patel, Alkesh B.; Pathak, V. M.; Patel, K. D.; Solanki, G. K.

2018-05-01

Group II-VI Compounds have emerged out as most suitable in the class of photo sensitive material. They represent a strong position in terms of their applications in the field of detectors as well as photo voltaic devices. Cadmium telluride is the prime member of this Group, because of high acceptance of this material as active component in opto-electronic devices. In this paper we report preparation and characterization of CdTe thin films by using a most economical screen printing technique in association with sintering at 510°C temperature. Surface morphology and smoothness are prime parameters of any deposited to be used as an active region of devices. Thus, we studied of the screen printed thin film by means of atomic force microscopy (AFM) and scanning electron microscopy (SEM) for this purpose. However, growth processes induced intrinsic defects in fabricated films work as charge traps and affect the conduction process significantly. So the conduction mechanism of deposited CdTe thin film is studied under dark as well as illuminated conditions. It is found that the deposited films showed the space charge limited conduction (SCLC) mechanism and hence various parameters of space charge limited conduction (SCLC) of CdTe film were evaluated and discussed and the photo responsive resistance is also presented in this paper.

Structural, Optical and Electrical Properties of ITO Thin Films

NASA Astrophysics Data System (ADS)

Sofi, A. H.; Shah, M. A.; Asokan, K.

2018-02-01

Transparent and conductive thin films of indium tin oxide were fabricated on glass substrates by the thermal evaporation technique. Tin doped indium ingots with low tin content were evaporated in vacuum (1.33 × 10-7 kpa) followed by an oxidation for 15 min in the atmosphere in the temperature range of 600-700°C. The structure and phase purity, surface morphology, optical and electrical properties of thin films were studied by x-ray diffractometry and Raman spectroscopy, scanning electron microcopy and atomic force microscopy, UV-visible spectrometry and Hall measurements in the van der Pauw configuration. The x-ray diffraction study showed the formation of the cubical phase of polycrystalline thin films. The morphological analysis showed the formation of ginger like structures and the energy dispersive x-ray spectrum confirmed the presence of indium (In), tin (Sn) and oxygen (O) elements. Hall measurements confirmed n-type conductivity of films with low electrical resistivity ( ρ) ˜ 10-3 Ω cm and high carrier concentration ( n) ˜ 1020 cm-3. For prevalent scattering mechanisms in the films, experimental data was analyzed by calculating a mean free path ( L) using a highly degenerate electron gas model. Furthermore, to investigate the performance of the deposited films as a transparent conductive material, the optical figure of merit was obtained for all the samples.

Synergistic effect of indium and gallium co-doping on the properties of RF sputtered ZnO thin films

NASA Astrophysics Data System (ADS)

Shaheera, M.; Girija, K. G.; Kaur, Manmeet; Geetha, V.; Debnath, A. K.; Karri, Malvika; Thota, Manoj Kumar; Vatsa, R. K.; Muthe, K. P.; Gadkari, S. C.

2018-04-01

ZnO thin films were synthesized using RF magnetron sputtering, with simultaneous incorporation of Indium (In) and Gallium (Ga). The structural, optical, chemical composition and surface morphology of the pure and co-doped (IGZO) thin films were characterized by X-Ray diffraction (XRD), UV-visible spectroscopy, Field Emission Scanning Electron Microscopy (FESEM), and Raman spectroscopy. XRD revealed that these films were oriented along c-axis with hexagonal wurtzite structure. The (002) diffraction peak in the co-doped sample was observed at 33.76° with a slight shift towards lower 2θ values as compared to pure ZnO. The surface morphology of the two thin films was observed to differ. For pure ZnO films, round grains were observed and for IGZO thin films round as well as rod type grains were observed. All thin films synthesized show excellent optical properties with more than 90% transmission in the visible region and band gap of the films is observed to decrease with co-doping. The co doping of In and Ga is therefore expected to provide a broad range optical and physical properties of ZnO thin films for a variety of optoelectronic applications.

An investigation of GaN thin films on AlN on sapphire substrate by sol-gel spin coating method

NASA Astrophysics Data System (ADS)

Amin, Nur Fahana Mohd; Ng, Sha Shiong

2017-12-01

In this research, the gallium nitride (GaN) thin films were deposited on aluminium nitride on sapphire (AlN/Al2O3) substrate by sol-gel spin coating method. Simple ethanol-based precursor with the addition of diethanolamine solution was used. The structural and morphology properties of synthesized GaN thin films were characterized by using X-ray Diffraction, Field-Emission Scanning Electron Microscopy and Atomic Force Microscopy. While the elemental compositions and the lattice vibrational properties of the films were investigated by means of the Energy Dispersive X-ray spectroscopy and Raman spectroscopy. All the results revealed that the wurtzite structure GaN thin films with GaN(002) preferred orientation and smooth surface morphology were successfully grown on AlN/Al2O3 substrate by using inexpensive and simplified sol-gel spin coating technique. The sol-gel spin coated GaN thin film with lowest oxygen content was also achieved.FESEM images show that GaN thin films with uniform and packed grains were formed. Based on the obtained results, it can be concluded that wurtzite structure GaN thin films were successfully deposited on AlN/Al2O3 substrate.

Effect of annealing temperature on physical properties of solution processed nickel oxide thin films

NASA Astrophysics Data System (ADS)

Sahoo, Pooja; Thangavel, R.

2018-05-01

In this report, NiO thin films were prepared at different annealing temperatures from nickel acetate precursor by sol-gel spin coating method. These films were characterized by different analytical techniques to obtain their structural, optical morphological and electrical properties using X-ray diffractometer (XRD), Field emission scanning electron microscopy (FESEM), UV-Vis NIR double beam spectrophotometer and Keithley 2450 source meter respectively. FESEM images clearly indicates the formation of a homogenous and porous films. Due to their porosity, they can be used in sensing applications. The optical absorption spectra elucidated that the films are highly transparent and have a suitable band gap which are in similar agreement with earlier reports. The current enhancement under illumination shows the suitability of nanostructured NiO thin films in its application in photovoltaics.

Synthesis and Characterization of Molybdenum Doped ZnO Thin Films by SILAR Deposition Method

NASA Astrophysics Data System (ADS)

Radha, R.; Sakthivelu, A.; Pradhabhan, D.

2016-08-01

Molybdenum (Mo) doped zinc oxide (ZnO) thin films were deposited on the glass substrate by Successive Ionic Layer Adsorption and Reaction (SILAR) deposition method. The effect of Mo dopant concentration of 5, 6.6 and 10 mol% on the structural, morphological, optical and electrical properties of n-type Mo doped ZnO films was studied. The X-ray diffraction (XRD) results confirmed that the Mo doped ZnO thin films were polycrystalline with wurtzite structure. The field emission scanning electron microscopy (FESEM) studies shows that the surface morphology of the films changes with Mo doping. A blue shift of the optical band gap was observed in the optical studies. Effect of Mo dopant concentration on electrical conductivity was studied and it shows comparatively high electrical conductivity at 10 mol% of Mo doping concentration.

Dewetting of polymer thin films on modified curved surfaces: preparation of polymer nanoparticles with asymmetric shapes by anodic aluminum oxide templates.

PubMed

Liu, Chih-Ting; Tsai, Chia-Chan; Chu, Chien-Wei; Chi, Mu-Huan; Chung, Pei-Yun; Chen, Jiun-Tai

2018-04-18

We study the dewetting behaviors of poly(methyl methacrylate) (PMMA) thin films coated in the cylindrical nanopores of anodic aluminum oxide (AAO) templates by thermal annealing. Self-assembled monolayers (SAMs) of n-octadecyltrichlorosilane (ODTS) are introduced to modify the pore surfaces of the AAO templates to induce the dewetting process. By using scanning electron microscopy (SEM), the dewetting-induced morphology transformation from the PMMA thin films to PMMA nanoparticles with asymmetric shapes can be observed. The sizes of the PMMA nanoparticles can be controlled by the original PMMA solution concentrations. The dewetting phenomena on the modified nanopores are explained by taking into account the excess intermolecular interaction free energy (ΔG). This work opens a new possibility for creating polymer nanoparticles with asymmetric shapes in confined geometries.

Fabrication and characterization of high mobility spin-coated zinc oxide thin film transistors

NASA Astrophysics Data System (ADS)

Singh, Shaivalini; Chakrabarti, P.

2012-10-01

A ZnO based thin film transistor (TFT) with bottom-gate configuration and SiO2 as insulating layer has been fabricated and characterized. The ZnO thin film was prepared by spin coating the sol-gel solution on the p-type Si wafers. The optical and structural properties of ZnO films were investigated using UV measurements and scanning electron microscope (SEM). The result of UV-visible study confirms that the films have a good absorbance in UV region and relatively low absorbance in the visible region. The TFT exhibited an off-current of 2.5×10-7 A. The values of field effect channel mobility and on/off current ratio extracted for the device, measured 11 cm2/V.s and ~102 respectively. The value of threshold voltage was found to be 1.3 V.

Structural and morphological properties of ITO thin films grown by magnetron sputtering

NASA Astrophysics Data System (ADS)

Ghorannevis, Z.; Akbarnejad, E.; Ghoranneviss, M.

2015-10-01

Physical properties of transparent and conducting indium tin oxide (ITO) thin films grown by radiofrequency (RF) magnetron sputtering are studied systematically by changing deposition time. The X-ray diffraction (XRD) data indicate polycrystalline thin films with grain orientations predominantly along the (2 2 2) and (4 0 0) directions. From atomic force microscopy (AFM) it is found that by increasing the deposition time, the roughness of the film increases. Scanning electron microscopy (SEM) images show a network of a high-porosity interconnected nanoparticles, which approximately have a pore size ranging between 20 and 30 nm. Optical measurements suggest an average transmission of 80 % for the ITO films. Sheet resistances are investigated using four-point probes, which imply that by increasing the film thickness the resistivities of the films decrease to 2.43 × 10-5 Ω cm.

Multilayer bioactive glass/zirconium titanate thin films in bone tissue engineering and regenerative dentistry

PubMed Central

Mozafari, Masoud; Salahinejad, Erfan; Shabafrooz, Vahid; Yazdimamaghani, Mostafa; Vashaee, Daryoosh; Tayebi, Lobat

2013-01-01

Surface modification, particularly coatings deposition, is beneficial to tissue-engineering applications. In this work, bioactive glass/zirconium titanate composite thin films were prepared by a sol-gel spin-coating method. The surface features of the coatings were studied by scanning electron microscopy, atomic force microscopy, and spectroscopic reflection analyses. The results show that uniform and sound multilayer thin films were successfully prepared through the optimization of the process variables and the application of carboxymethyl cellulose as a dispersing agent. Also, it was found that the thickness and roughness of the multilayer coatings increase nonlinearly with increasing the number of the layers. This new class of nanocomposite coatings, comprising the bioactive and inert components, is expected not only to enhance bioactivity and biocompatibility, but also to protect the surface of metallic implants against wear and corrosion. PMID:23641155

Electron ptychographic phase imaging of light elements in crystalline materials using Wigner distribution deconvolution

DOE PAGES

Yang, Hao; MacLaren, Ian; Jones, Lewys; ...

2017-04-01

Recent development in fast pixelated detector technology has allowed a two dimensional diffraction pattern to be recorded at every probe position of a two dimensional raster scan in a scanning transmission electron microscope (STEM), forming an information-rich four dimensional (4D) dataset. Electron ptychography has been shown to enable efficient coherent phase imaging of weakly scattering objects from a 4D dataset recorded using a focused electron probe, which is optimised for simultaneous incoherent Z-contrast imaging and spectroscopy in STEM. Thus coherent phase contrast and incoherent Z-contrast imaging modes can be efficiently combined to provide a good sensitivity of both light andmore » heavy elements at atomic resolution. Here, we explore the application of electron ptychography for atomic resolution imaging of strongly scattering crystalline specimens, and present experiments on imaging crystalline specimens including samples containing defects, under dynamical channelling conditions using an aberration corrected microscope. A ptychographic reconstruction method called Wigner distribution deconvolution (WDD) was implemented. Our experimental results and simulation results suggest that ptychography provides a readily interpretable phase image and great sensitivity for imaging light elements at atomic resolution in relatively thin crystalline materials.« less

Understanding individual defects in CdTe thin-film solar cells via STEM: From atomic structure to electrical activity

DOE PAGES

Li, Chen; Poplawsky, Jonathan; Yan, Yanfa; ...

2017-07-01

Here in this paper we review a systematic study of the structure-property correlations of a series of defects in CdTe solar cells. A variety of experimental methods, including aberration-corrected scanning transmission electron microscopy, electron energy loss spectroscopy, energy dispersive X-ray spectroscopy, and electron-beam-induced current have been combined with density-functional theory. The research traces the connections between the structures and electrical activities of individual defects including intra-grain partial dislocations, grain boundaries and the CdTe/CdS interface. The interpretations of the physical origin underlying the structure-property correlation provide insights that should further the development of future CdTe solar cells.

Understanding individual defects in CdTe thin-film solar cells via STEM: From atomic structure to electrical activity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Chen; Poplawsky, Jonathan; Yan, Yanfa

Here in this paper we review a systematic study of the structure-property correlations of a series of defects in CdTe solar cells. A variety of experimental methods, including aberration-corrected scanning transmission electron microscopy, electron energy loss spectroscopy, energy dispersive X-ray spectroscopy, and electron-beam-induced current have been combined with density-functional theory. The research traces the connections between the structures and electrical activities of individual defects including intra-grain partial dislocations, grain boundaries and the CdTe/CdS interface. The interpretations of the physical origin underlying the structure-property correlation provide insights that should further the development of future CdTe solar cells.

Investigation of the relations between resin and advanced composite mechanical properties. Volume 2: Appendices

NASA Technical Reports Server (NTRS)

Zimmerman, R. S.; Adams, D. F.; Walrath, D. E.

1984-01-01

One untoughened epoxy baseline resin and three toughened epoxy resin systems were evaluated. The Hercules 3502, 2220-1, and 2220-3, and Ciba-Geigy Fibredux 914 resin systems were supplied in the uncured state by NASA-Langley and cast into thin flat specimens and round dogbone specimens. Tensile and torsional shear measurements were performed at three temperatures and two moisture conditions. Coefficients of thermal expansion and moisture expansion were also measured. Extensive scanning electron microscopic examination of fracture surfaces was performed to permit the correlation of observed failure modes with the environmental conditions under which the various specimens were tested. A micromechanics analysis was used to predict the unidirectional composite response under the various test conditions, incorporating the neat resin experimental results as the required input data. The mechanical and physical test results, the scanning electron microscope observations, and the analytical predictions were then correlated.

Investigation of the relations between neat resin and advanced composite mechanical properties. Volume 1: Results

NASA Technical Reports Server (NTRS)

Zimmerman, R. S.; Adams, D. F.; Walrath, D. E.

1984-01-01

A detailed evaluation of one untoughened epoxy baseline resin and three toughened epoxy resin systems was performed. The Hercules 3502, 2220-1, and 2220-3, and Ciba-Geigy Fibredux 914 resin systems were supplied in the uncured state by NASA-Langley and cast into thin flat specimens and round dogbone specimens. Tensile and torsional shear measurements were performed at three temperatures and two moisture conditions. Coefficients of thermal expansion and moisture expansion were also measured. Extensive scanning electron microscopic examination of fracture surfaces was performed, to permit the correlation of observed failure modes with the environmental conditions under which the various specimens were tested. A micromechanics analysis was used to predict the unidirectional composite response under the various test conditions, using the neat resin experimental results as the required input data. Mechanical and physical test results, the scanning electron microscope observations, and the analytical predictions were then correlated.

Three-dimensional nanostructure determination from a large diffraction data set recorded using scanning electron nanodiffraction

DOE PAGES

Meng, Yifei; Zuo, Jian -Min

2016-07-04

A diffraction-based technique is developed for the determination of three-dimensional nanostructures. The technique employs high-resolution and low-dose scanning electron nanodiffraction (SEND) to acquire three-dimensional diffraction patterns, with the help of a special sample holder for large-angle rotation. Grains are identified in three-dimensional space based on crystal orientation and on reconstructed dark-field images from the recorded diffraction patterns. Application to a nanocrystalline TiN thin film shows that the three-dimensional morphology of columnar TiN grains of tens of nanometres in diameter can be reconstructed using an algebraic iterative algorithm under specified prior conditions, together with their crystallographic orientations. The principles can bemore » extended to multiphase nanocrystalline materials as well. Furthermore, the tomographic SEND technique provides an effective and adaptive way of determining three-dimensional nanostructures.« less

Rose bengal-grafted biodegradable microcapsules: singlet-oxygen generation and cancer-cell incapacitation.

PubMed

Wang, Xiao-Lei; Zeng, Yu; Zheng, Yan-Zhen; Chen, Jian-Feng; Tao, Xia; Wang, Ling-Xuan; Teng, Yan

2011-09-26

Rose bengal-grafted chitosan (RB-CHI), synthesized through dehydration between amino and carboxyl functional groups under mild conditions, was coated onto the outer layer of preformed biodegradable microcapsules consisting of sodium alginate and chitosan. The fabricated photosensitive microcapsules were characterized by optical microscopy, scanning electron microscopy, and confocal laser scanning microscopy. The assembled materials maintained intact spherical morphology and thus showed good ability to form thin films. Electron spin resonance spectroscopy allowed direct observation of the generation of singlet oxygen ((1)O(2)) from photosensitive microcapsules under light excitation at about 545 nm. Furthermore, with increasing light radiation, the content of (1)O(2) increased, as detected by a chemical probe. In vitro cellular toxicity assays showed that RB-CHI-coated photosensitive microcapsules exhibit good biocompatibility in darkness and high cytotoxicity after irradiation, and could provide new photoresponsive drug-delivery vehicles. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Quantitative Transmission Electron Microscopy of Nanoparticles and Thin-Film Formation in Electroless Metallization of Polymeric Surfaces

NASA Astrophysics Data System (ADS)

Dutta, Aniruddha; Heinrich, Helge; Kuebler, Stephen; Grabill, Chris; Bhattacharya, Aniket

2011-03-01

Gold nanoparticles(Au-NPs) act as nucleation sites for electroless deposition of silver on functionalized SU8 polymeric surfaces. Here we report the nanoscale morphology of Au and Ag nanoparticles as studied by Transmission Electron Microscopy (TEM). Scanning TEM with a high-angle annular dark-field detector is used to obtain atomic number contrast. From the intensity-calibrated plan-view scanning TEM images we determine the mean thickness and the volume distribution of the Au-NPs on the surface of the functionalized polymer. We also report the height and the radius distribution of the gold nanoparticles obtained from STEM images taking into consideration the experimental errors. The cross sectional TEM images yield the density and the average distance of the Au and Ag nanoparticles on the surface of the polymer. Supported by grant NSF, Chemistry Division.

Revealing the synergetic effects in Ni nanoparticle-carbon nanotube hybrids by scanning transmission X-ray microscopy and their application in the hydrolysis of ammonia borane.

PubMed

Zhao, Guanqi; Zhong, Jun; Wang, Jian; Sham, Tsun-Kong; Sun, Xuhui; Lee, Shuit-Tong

2015-06-07

The hybrids of carbon nanotubes (CNTs) and the supported Ni nanoparticles (NPs) have been studied by scanning transmission X-ray microscopy (STXM) and tested by the hydrolysis reaction of ammonia borane (AB, NH3BH3). Data clearly showed the existence of a strong interaction between Ni NPs and thin CNTs (C-O-Ni bonds), which favored the tunable (buffer) electronic structure of Ni NPs facilitating the catalytic process. The hydrolysis process of AB confirmed the hypothesis that the hybrids with a strong interfacial interaction would show superior catalytic performance, while the hybrids with a weak interfacial interaction show poor performance. Our results provide a wealth of detailed information regarding the electronic structure of the NP-CNT hybrids and provide guidance towards the rational design of high-performance catalysts for energy applications.

L-Phenylalanine functionalized silver nanoparticles: Photocatalytic and nonlinear optical applications

NASA Astrophysics Data System (ADS)

Nidya, M.; Umadevi, M.; Sankar, Pranitha; Philip, Reji; Rajkumar, Beulah J. M.

2015-04-01

An extensive study on the behavior of L-Phenylalanine capped silver nanoparticles (Phe-Ag NPs) in the aqueous phase and in a sol-gel thin film showed different UV/Vis, Transmission Electron Microscope (TEM), Dynamic Light Scattering and Zeta potential profiles. Scanning Electron Microscope (SEM) images of the samples in the sol gel film showed Ag embedded in the SiO2 matrix. Surface Enhanced Raman Spectra (SERS) confirmed that both in the aqueous media and in the sol gel film, the attachment of Phe to the Ag NP surface was through the benzene ring, with the sol-gel film showing a better enhancement. Photocatalytic degradation of crystal violet was measured spectrophotometrically using Phe-Ag NPs as a nanocatalyst under visible light illumination. Intensity-dependent nonlinear optical absorption of Phe-Ag measured using the open aperture Z-scan technique revealed that the material is an efficient optical limiter with potential applications.

Effect of growth time on the structure, morphology and optical properties of hydrothermally synthesized TiO2 nanorod thin films

NASA Astrophysics Data System (ADS)

Mohapatra, A. K.; Nayak, J.

2018-05-01

Titanium dioxide (TiO2) nanorod thin films were deposited on fluorine doped tin oxide coated glass substrates by a single step rapid hydrothermal process. The concentration of the precursor, the temperature of the reaction mixture were optimized in order to enhance the rate of deposition. Unlike the previously reported hydrothermal treatment for 24 - 48 h, the deposition of well aligned titanium dioxide nanorods was achieved in a short time such as 3 - 8 h. The crystal structure of the films were investigated by X-rays diffraction. The morphology of the nanorod films were studied with scanning electron microscopy. The optical properties were studied by photoluminescence spectroscopy.

Dielectric response of branched copper phthalocyanine

NASA Astrophysics Data System (ADS)

Hamam, Khalil J.; Al-Amar, Mohammad M.; Mezei, Gellert; Guda, Ramakrishna; Burns, Clement A.

2017-09-01

The dielectric constant of pressed pellets and thin films of branched copper phthalocyanine (CuPc) was investigated as a function of frequency from 0.1 kHz to 1 MHz and temperature from 20 °C to 100 °C. Surface morphology was studied using a scanning electron microscope. The high-frequency values of the dielectric constant of pellets and thin films are ~3.5 and ~5.8, respectively. The response was only weakly dependent on frequency and temperature. The branched structure of the CuPc molecules helped to cancel out the effects of low-frequency polarization mechanisms. A planar delocalized charge system with two-dimensional localization was found using time-resolved photoluminescence measurements.

Structure and optical properties of TiO2 thin films deposited by ALD method

NASA Astrophysics Data System (ADS)

Szindler, Marek; Szindler, Magdalena M.; Boryło, Paulina; Jung, Tymoteusz

2017-12-01

This paper presents the results of study on titanium dioxide thin films prepared by atomic layer deposition method on a silicon substrate. The changes of surface morphology have been observed in topographic images performed with the atomic force microscope (AFM) and scanning electron microscope (SEM). Obtained roughness parameters have been calculated with XEI Park Systems software. Qualitative studies of chemical composition were also performed using the energy dispersive spectrometer (EDS). The structure of titanium dioxide was investigated by X-ray crystallography. A variety of crystalline TiO2 was also confirmed by using the Raman spectrometer. The optical reflection spectra have been measured with UV-Vis spectrophotometry.

Quantitative measurement of piezoelectric coefficient of thin film using a scanning evanescent microwave microscope.

PubMed

Zhao, Zhenli; Luo, Zhenlin; Liu, Chihui; Wu, Wenbin; Gao, Chen; Lu, Yalin

2008-06-01

This article describes a new approach to quantitatively measure the piezoelectric coefficients of thin films at the microscopic level using a scanning evanescent microwave microscope. This technique can resolve 10 pm deformation caused by the piezoelectric effect and has the advantages of high scanning speed, large scanning area, submicron spatial resolution, and a simultaneous accessibility to many other related properties. Results from the test measurements on the longitudinal piezoelectric coefficient of PZT thin film agree well with those from other techniques listed in literatures.

Simulating Lattice Image of Suspended Graphene Taken by Helium Ion Microscopy

NASA Astrophysics Data System (ADS)

Miyamoto, Yoshiyuki; Zhang, Hong; Rubio, Angel

2013-03-01

Atomic scale image in nano-scale helps us to characterize property of graphene, and performance of high-resolution transmission electron microscopy (HRTEM) is significant, so far. While a tool without pre-treatment of samples is demanded in practice. Helium ion microscopy (HIM), firstly reported by Word et. al. in 2006, was applied for monitoring graphene in device structure (Lumme, et. al., 2009). Motivated by recent HIM explorations, we examined the possibility of taking lattice image of suspended graphene by HIM. The intensity of secondary emitted electron is recorded as a profile of scanned He+-beam in HIM measurement. We mimicked this situation by performing electron-ion dynamics based on the first-principles simulation within the time-dependent density functional theory. He+ ion collision on single graphene sheet at several impact points were simulated and we found that the amount of secondary emitted electron from graphene reflected the valence charge distribution of the graphene sheet. Therefore HIM using atomically thin He-beam should be able to provide the lattice image, and we propose that an experiment generating ultra-thin He+ ion beam (Rezeq et. al., 2006) should be combined with HIM technique. All calculations were performed by using the Earth Simulator.

Enhanced Photocatalytic Activity of Diamond Thin Films Using Embedded Ag Nanoparticles.

PubMed

Li, Shuo; Bandy, Jason A; Hamers, Robert J

2018-02-14

Silver nanoparticles embedded into the diamond thin films enhance the optical absorption and the photocatalytic activity toward the solvated electron-initiated reduction of N 2 to NH 3 in water. Here, we demonstrate the formation of diamond films with embedded Ag nanoparticles <100 nm in diameter. Cross-sectional scanning electron microscopy (SEM), energy-dependent SEM, and energy-dispersive X-ray analysis demonstrate the formation of encapsulated nanoparticles. Optical absorption measurements in the visible and ultraviolet region show that the resulting films exhibit plasmonic resonances in the visible and near-ultraviolet region. Measurements of photocatalytic activity using supraband gap (λ < 225 nm) and sub-band gap (λ > 225 nm) excitation show significantly enhanced ability to convert N 2 to NH 3 . Incorporation of Ag nanoparticles induces a nearly 5-fold increase in activity using a sub-band gap excitation with λ > 225 nm. Our results suggest that internal photoemission, in which electrons are excited from Ag into diamond's conduction band, is an important process that extends the wavelength region beyond diamond's band gap. Other factors, including Ag-induced optical scattering and formation of graphitic impurities are also discussed.

Europium-doped mesoporous titania thin films: rare-earth locations and emission fluctuations under illumination.

PubMed

Leroy, Celine Marie; Cardinal, Thierry; Jubera, Veronique; Treguer-Delapierre, Mona; Majimel, Jerome; Manaud, Jean Pierre; Backov, Renal; Boissière, Cedric; Grosso, David; Sanchez, Clement; Viana, Bruno; Pellé, Fabienne

2008-10-06

Herein, Eu(III)-doped 3D mesoscopically ordered arrays of mesoporous and nanocrystalline titania are prepared and studied. The rare-earth-doped titania thin films-synthesized via evaporation-induced self-assembly (EISA)-are characterized by using environmental ellipsoporosimetry, electronic microscopy (i.e. high-resolution scanning electron microscopy, HR-SEM, and transmission electron microscopy, HR-TEM), X-ray diffraction, and luminescence spectroscopy. Structural characterizations show that high europium-ion loadings can be incorporated into the titanium-dioxide walls without destroying the mesoporous arrangement. The luminescence properties of Eu(III) are investigated by using steady-state and time-resolved spectroscopy via excitation of the Eu(III) ions through the titania host. Using Eu(III) luminescence as a probe, the europium-ion sites can be addressed with at least two different environments within the mesoporous framework, namely, a nanocrystalline environment and a glasslike one. Emission fluctuations ((5)D(0)-->(7)F(2)) are observed upon continuous UV excitation in the host matrix. These fluctuations are attributed to charge trapping and appear to be strongly dependent on the amount of europium and the level of crystallinity.

Hydrogen Gas Sensing Characteristics of Nanostructured NiO Thin Films Synthesized by SILAR Method

NASA Astrophysics Data System (ADS)

Karaduman, Irmak; Çorlu, Tugba; Yıldırım, M. Ali; Ateş, Aytunç; Acar, Selim

2017-07-01

Nanostructured NiO thin films have been synthesized by a facile, low-cost successive ionic layer adsorption and reaction (SILAR) method, and the effects of the film thickness on their hydrogen gas sensing properties investigated. The samples were characterized by scanning electron microscopy (SEM), x-ray diffraction (XRD) analysis, and energy-dispersive x-ray analysis. The XRD results revealed that the crystallinity improved with increasing thickness, exhibiting polycrystalline structure. SEM studies showed that all the films covered the glass substrate well. According to optical absorption measurements, the optical bandgap decreased with increasing film thickness. The gas sensing properties of the nanostructured NiO thin films were studied as a function of operating temperature and gas concentration. The samples showed good sensing performance of H2 gas with high response. The maximum response was 75% at operating temperature of 200°C for hydrogen gas concentration of 40 ppm. These results demonstrate that nanostructured NiO thin films synthesized by the SILAR method have potential for application in hydrogen detection.

The synthesis of multifunctional porous honey comb-like La2O3 thin film for supercapacitor and gas sensor applications.

PubMed

Yadav, A A; Lokhande, A C; Pujari, R B; Kim, J H; Lokhande, C D

2016-12-15

The porous honey comb-like La 2 O 3 thin films have been synthesized using one step spray pyrolysis method. The influence of sprayed solution quantity on properties of La 2 O 3 thin films is studied using X-ray diffraction, Fourier transform spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, optical absorption and Brunauer-Emmett-Teller techniques. Morphology of La 2 O 3 electrode is controlled with sprayed solution quantity. The supercapacitive properties of La 2 O 3 thin film electrode are investigated using cyclic voltammetry, galvanostatic charge-discharge and electrochemical impedance techniques. The La 2 O 3 film electrode exhibited the specific capacitance of the 166Fg -1 with 85% stability for the 3000 cycles. The La 2 O 3 film electrode exhibited sensitivity of 68 at 523K for 500ppm CO 2 gas concentration. The possible CO 2 sensing mechanism is discussed. Copyright © 2016 Elsevier Inc. All rights reserved.

Design and fabrication of highly hydrophobic Mn nano-sculptured thin films and evaluation of surface properties on hydrophobicity

NASA Astrophysics Data System (ADS)

Hosseini, Somaye; Savaloni, Hadi; Gholipour-Shahraki, Mehran

2017-03-01

The wettability of solid surfaces is important from the aspects of both science and technology. The Mn nano-sculptured thin films were designed and fabricated by oblique angle deposition of Mn on glass substrates at room temperature. The obtained structure was characterized by field emission scanning electron microscopy and atomic force microscopy. The wettability of thin films samples was investigated by water contact angle (WCA). The 4-pointed helical star-shaped structure exhibits hydrophobicity with static WCAs of more than 133° for a 10-mg distilled water droplet. This sample also shows the rose petal effect with the additional property of high adhesion. The Mn nano-sculptured thin films also act as a sticky surface which is confirmed by hysteresis of the contact angle obtained from advancing and receding contact angles measurements. Physicochemical property of liquid phase could effectively change the contact angle, and polar solvents in contact with hydrophobic solid surfaces do not necessarily show high contact angle value.

Seedless-grown of ZnO thin films for photoelectrochemical water splitting application

NASA Astrophysics Data System (ADS)

Abdullah, Aidahani; Hamid, Muhammad Azmi Abdul; Chiu, W. S.

2018-04-01

We developed a seedless hydrothermal method to grow a flower like ZnO nanorods. Prior to the growth, a layer of Au thin film is sputtered onto the surface of indium tin oxide (ITO) coated glass substrate. The morphological, structural and optical properties of the ZnO nanostructures were characterized by means of scanning electron microscopy (SEM), X-ray diffraction (XRD), and diffuse reflection measurement to understand the growth process of the working thin film. The photoelectrochemical (PEC) results suggest that the deposition of ZnO nanorods on Au nanoparticles plays an important role in enhancing the photoelectrode activity. H2 evolution from photo-splitting of water over Au-incorporated ZnO in the 0.1M NaOH liquid system was enhanced, compared to that over bare ZnO; particularly, the production of 15.5 µL of H2 gas after twenty five minutes exposure of ZnO grown on Au-coated thin film.

Electrochemical Properties of RuO2 Electrodes as a Function of Thin Film Thickness

NASA Astrophysics Data System (ADS)

Li, Xiang; Xiong, Jian; Luo, Yuan; Luo, Yongmei

2018-01-01

A thin film RuO2 electrode was prepared by spin coating thermal decomposition methods. Precursor containing RuCl3·nH2O and isopropyl alcohol was coated on tantalum substrate and annealed at 250-260°C for 3 h to form a thin film RuO2 electrode of about 2.5 μm, 5.6 μm, 11.4 μm, and 14.5 μm in thickness. X-ray diffraction revealed that peak intensities of those electrodes were similar and close to each other. Scanning electron microscopy showed that thin film of 5.6 μm in thickness was dense and free of cracks. Electrochemical performances of electrodes were examined by cyclic voltammetry, galvanostatic charge/discharge as well as equivalent series resistance. The highest specific capacitance value of 725 F g-1 was registered for the electrode of 5.6 μm in thickness with good constant current charge/discharge and equivalent series resistance of 0.36 Ω as well as cyclic stability.

Carbon nanotube thin film strain sensors: comparison between experimental tests and numerical simulations

NASA Astrophysics Data System (ADS)

Lee, Bo Mi; Loh, Kenneth J.

2017-04-01

Carbon nanotubes can be randomly deposited in polymer thin film matrices to form nanocomposite strain sensors. However, a computational framework that enables the direct design of these nanocomposite thin films is still lacking. The objective of this study is to derive an experimentally validated and two-dimensional numerical model of carbon nanotube-based thin film strain sensors. This study consisted of two parts. First, multi-walled carbon nanotube (MWCNT)-Pluronic strain sensors were fabricated using vacuum filtration, and their physical, electrical, and electromechanical properties were evaluated. Second, scanning electron microscope images of the films were used for identifying topological features of the percolated MWCNT network, where the information obtained was then utilized for developing the numerical model. Validation of the numerical model was achieved by ensuring that the area ratios (of MWCNTs relative to the polymer matrix) were equivalent for both the experimental and modeled cases. Strain sensing behavior of the percolation-based model was simulated and then compared to experimental test results.

Structural and optical properties of annealed and illuminated (Ag3AsS3)0.6(As2S3)0.4 thin films

NASA Astrophysics Data System (ADS)

Studenyak, I. P.; Neimet, Yu. Yu.; Rati, Y. Y.; Stanko, D.; Kranjčec, M.; Kökényesi, S.; Daróci, L.; Bohdan, R.

2014-11-01

(Ag3AsS3)0.6(As2S3)0.4 thin films were deposited upon a quartz substrate by rapid thermal evaporation. Structural studies of the as-deposited, annealed and illuminated films were performed using XRD, scanning electron and atomic force microscopies. Surfaces of all the films were found to be covered with Ag-rich crystalline micrometer sized cones. Thermal annealing leads to mechanical deformation of part of the cones and their detachment from the base film surface while the laser illumination leads to the new formations appearance on the surface of thin films. The spectroscopic studies of optical transmission spectra for as-deposited, annealed and illuminated thin films were carried out. The optical absorption spectra in the region of its exponential behaviour were analysed, the dispersion dependences of refractive index as well as their variation after annealing and illumination were investigated.

Defect engineering in atomically-thin bismuth oxychloride towards photocatalytic oxygen evolution

DOE Office of Scientific and Technical Information (OSTI.GOV)

Di, Jun; Chen, Chao; Yang, Shi -Ze

Photocatalytic solar energy conversion is a clean technology for producing renewable energy sources, but its efficiency is greatly hindered by the kinetically sluggish oxygen evolution reaction. Herein, confined defects in atomically-thin BiOCl nanosheets were created to serve as a remarkable platform to explore the relationship between defects and photocatalytic activity. Surface defects can be clearly observed on atomically-thin BiOCl nanosheets from scanning transmission electron microscopy images. Theoretical/experimental results suggest that defect engineering increased states of density and narrowed the band gap. With combined effects from defect induced shortened hole migratory paths and creation of coordination-unsaturated active atoms with dangling bonds,more » defect-rich BiOCl nanosheets displayed 3 and 8 times higher photocatalytic activity towards oxygen evolution compared with atomically-thin BiOCl nanosheets and bulk BiOCl, respectively. As a result, this successful application of defect engineering will pave a new pathway for improving photocatalytic oxygen evolution activity of other materials.« less

Defect engineering in atomically-thin bismuth oxychloride towards photocatalytic oxygen evolution

DOE PAGES

Di, Jun; Chen, Chao; Yang, Shi -Ze; ...

2017-06-26

Photocatalytic solar energy conversion is a clean technology for producing renewable energy sources, but its efficiency is greatly hindered by the kinetically sluggish oxygen evolution reaction. Herein, confined defects in atomically-thin BiOCl nanosheets were created to serve as a remarkable platform to explore the relationship between defects and photocatalytic activity. Surface defects can be clearly observed on atomically-thin BiOCl nanosheets from scanning transmission electron microscopy images. Theoretical/experimental results suggest that defect engineering increased states of density and narrowed the band gap. With combined effects from defect induced shortened hole migratory paths and creation of coordination-unsaturated active atoms with dangling bonds,more » defect-rich BiOCl nanosheets displayed 3 and 8 times higher photocatalytic activity towards oxygen evolution compared with atomically-thin BiOCl nanosheets and bulk BiOCl, respectively. As a result, this successful application of defect engineering will pave a new pathway for improving photocatalytic oxygen evolution activity of other materials.« less

Influence of Thermal Annealing Treatment on Bipolar Switching Properties of Vanadium Oxide Thin-Film Resistance Random-Access Memory Devices

NASA Astrophysics Data System (ADS)

Chen, Kai-Huang; Cheng, Chien-Min; Kao, Ming-Cheng; Chang, Kuan-Chang; Chang, Ting-Chang; Tsai, Tsung-Ming; Wu, Sean; Su, Feng-Yi

2017-04-01

The bipolar switching properties and electrical conduction mechanism of vanadium oxide thin-film resistive random-access memory (RRAM) devices obtained using a rapid thermal annealing (RTA) process have been investigated in high-resistive status/low-resistive status (HRS/LRS) and are discussed herein. In addition, the resistance switching properties and quality improvement of the vanadium oxide thin-film RRAM devices were measured by x-ray diffraction (XRD) analysis, x-ray photoelectron spectrometry (XPS), scanning electron microscopy (SEM), atomic force microscopy (AFM), and current-voltage ( I- V) measurements. The activation energy of the hopping conduction mechanism in the devices was investigated based on Arrhenius plots in HRS and LRS. The hopping conduction distance and activation energy barrier were obtained as 12 nm and 45 meV, respectively. The thermal annealing process is recognized as a candidate method for fabrication of thin-film RRAM devices, being compatible with integrated circuit technology for nonvolatile memory devices.

Tuning the properties of tin oxide thin films for device fabrications

NASA Astrophysics Data System (ADS)

Sudha, A.; Sharma, S. L.; Gupta, A. N.; Sharma, S. D.

2017-11-01

Tin oxide thin films were deposited on well cleaned glass substrates by thermal evaporation in vacuum and were annealed at 500 ∘C in the open atmosphere inside a furnace for 90 min for promoting the sensitivity of the films. The X-ray diffraction studies revealed that the as-deposited films were amorphous in nature and the annealed films showed appreciable crystalline behavior. The annealed thin films were then irradiated using 60Co gamma source. The radiation induced changes were then studied by X-ray diffraction, scanning electron microscopy, UV-vis spectroscopy and I- V characterization. The remarkable increase in the average grain size, the decrement in the energy band gap and resistivity due to the gamma irradiations up to a certain dose and the reversal of these properties at higher doses are the important observations. The large changes in the conductivity and energy band gap of the annealed thin films due to gamma irradiation make these films quite important device material for the fabrication of gamma sensors and dosimeters.

Nano CaCO₃ imprinted starch hybrid polyethylhexylacrylate\\polyvinylalcohol nanocomposite thin films.

PubMed

Prusty, Kalyani; Swain, Sarat K

2016-03-30

Starch hybrid polyethylhexylacrylate (PEHA)/polyvinylalcohol (PVA) nanocomposite thin films are prepared by different composition of nano CaCO3 in aqueous medium. The chemical interaction of nano CaCO3 with PEHA in presence of starch and PVA is investigated by Fourier transforms infrared spectroscopy (FTIR). X-ray diffraction (XRD) is used in order to study the change in crystallite size and d-spacing during the formation of nanocomposite thin film. The surface morphology of nanofilms is studied by scanning electron microscope (SEM). The topology and surface roughness of the films is noticed by atomic force microscope (AFM). The tensile strength, thermal stability and thermal conductivity of films are increased with increase in concentrations of CaCO3 nanopowder. The chemical resistance and biodegradable properties of the nanocomposite thin films are also investigated. The growth of bacteria and fungi in starch hybrid PEHA film is reduced substantially with imprint of nano CaCO3. Copyright © 2015 Elsevier Ltd. All rights reserved.

Structural and optical properties of Na-doped ZnO films

NASA Astrophysics Data System (ADS)

Akcan, D.; Gungor, A.; Arda, L.

2018-06-01

Zn1-xNaxO (x = 0.0-0.05) solutions have been synthesized by the sol-gel technique using Zinc acetate dihydrate and Sodium acetate which were dissolved into solvent and chelating agent. Na-doped ZnO nanoparticles were obtained from solutions to find phase and crystal structure. Na-doped ZnO films have been deposited onto glass substrate by using sol-gel dip coating system. The effects of dopant concentration on the structure, morphology, and optical properties of Na-doped ZnO thin films deposited on glass substrate are investigated. Characterization of Zn1-xNaxO nanoparticles and thin films are examined using differential thermal analysis (DTA)/thermogravimetric analysis (TGA), Scanning electron microscope (SEM) and X-Ray diffractometer (XRD). Optical properties of Zn1-xNaxO thin films were obtained by using PG Instruments UV-Vis-NIR spectrophotometer in 190-1100 nm range. The structure, morphology, and optical properties of thin films are presented.

Transparent Conducting Mo-Doped CdO Thin Films by Spray Pyrolysis Method for Solar Cell Applications

NASA Astrophysics Data System (ADS)

Helen, S. J.; Devadason, Suganthi; Haris, M.; Mahalingam, T.

2018-04-01

Pure and 3%, 5%, and 7% molybdenum-doped cadmium oxide (CdO) thin films have been prepared on glass substrates preheated to 400°C using a spray pyrolysis technique, then analyzed using x-ray diffraction analysis, field-emission scanning electron microscopy, ultraviolet-visible spectroscopy, and photoluminescence and Hall measurements. The films were found to have polycrystalline nature with cubic structure. The crystallite size was calculated to be ˜ 12 nm for various doping concentrations. Doping improved the optical transparency of the CdO thin film, with the 5% Mo-doped film recording the highest transmittance in the optical region. The energy bandgap deduced from optical studies ranged from 2.38 eV and 2.44 eV for different Mo doping levels. The electrical conductivity was enhanced on Mo doping, with the highest conductivity of 1.74 × 103 (Ω cm)-1 being achieved for the 5% Mo-doped CdO thin film.

Young’s modulus and Poisson’s ratio changes due to machining in porous microcracked cordierite

DOE PAGES

Cooper, R. C.; Bruno, Giovanni; Onel, Yener; ...

2016-07-25

Microstructural changes in porous cordierite caused by machining were characterized using microtensile testing, X-ray computed tomography and scanning electron microscopy. Young s moduli and Poisson s ratios were determined on ~215-380 um thick machined samples by combining digital image correlation and microtensile loading. The results provide evidence for an increase in microcrack density due to machining of the thin samples extracted from diesel particulate filter honeycombs.

Study of the photovoltaic effect in thin film barium titanate

NASA Technical Reports Server (NTRS)

Grannemann, W. W.; Dharmadhikari, V. S.

1982-01-01

The basic mechanism associated with the photovoltaic phenomena observed in the R.F. sputtered BaTiO3/silicon system is presented. Series of measurements of short circuit photocurrents and open circuit photovoltage were made. The composition depth profiles and the interface characteristics of the BaTiO3/silicon system were investigated for a better understanding of the electronic properties. A Scanning Auger Microprobe combined with ion in depth profiling were used.

Effect of Mg doping in ZnO buffer layer on ZnO thin film devices for electronic applications

NASA Astrophysics Data System (ADS)

Giri, Pushpa; Chakrabarti, P.

2016-05-01

Zinc Oxide (ZnO) thin films have been grown on p-silicon (Si) substrate using magnesium doped ZnO (Mg: ZnO) buffer layer by radio-frequency (RF) sputtering method. In this paper, we have optimized the concentration of Mg (0-5 atomic percent (at. %)) ZnO buffer layer to examine its effect on ZnO thin film based devices for electronic and optoelectronic applications. The crystalline nature, morphology and topography of the surface of the thin film have been characterized. The optical as well as electrical properties of the active ZnO film can be tailored by varying the concentration of Mg in the buffer layer. The crystallite size in the active ZnO thin film was found to increase with the Mg concentration in the buffer layer in the range of 0-3 at. % and subsequently decrease with increasing Mg atom concentration in the ZnO. The same was verified by the surface morphology and topography studies carried out with scanning electron microscope (SEM) and atomic electron microscopy (AFM) respectively. The reflectance in the visible region was measured to be less than 80% and found to decrease with increase in Mg concentration from 0 to 3 at. % in the buffer region. The optical bandgap was initially found to increase from 3.02 eV to 3.74 eV by increasing the Mg content from 0 to 3 at. % but subsequently decreases and drops down to 3.43 eV for a concentration of 5 at. %. The study of an Au:Pd/ZnO Schottky diode reveals that for optimum doping of the buffer layer the device exhibits superior rectifying behavior. The barrier height, ideality factor, rectification ratio, reverse saturation current and series resistance of the Schottky diode were extracted from the measured current voltage (I-V) characteristics.

Li-ion diffusion kinetics in LiCoPO 4 thin films deposited on NASICON-type glass ceramic electrolytes by magnetron sputtering

NASA Astrophysics Data System (ADS)

Xie, J.; Imanishi, N.; Zhang, T.; Hirano, A.; Takeda, Y.; Yamamoto, O.

LiCoPO 4 thin films were deposited on Li 1+ x+ yAl xTi 2- xSi yP 3- yO 12 (LATSP) solid electrolyte by radio frequency magnetron sputtering and were characterized by X-ray diffraction and scanning electron microscope. The films show a (1 1 1) preferred orientation upon annealing and are chemically stable with LATSP up to 600 °C in air. An all-solid-state Li/PEO 18-Li(CF 3SO 2) 2N/LATSP/LiCoPO 4/Au cell was fabricated to investigate the electrochemical performance and Li-ion chemical diffusion coefficients, D˜Li , of the LiCoPO 4 thin films. The potential dependence of D˜Li values of the LiCoPO 4 thin film was investigated by potentiostatic intermittent titration technique and was compared with those of the LiFePO 4 thin film. These results showed that the intercalation mechanism of Li-ion in LiCoPO 4 is different from that in LiFePO 4.

Impact of nanostructured thin ZnO film in ultraviolet protection

PubMed Central

Sasani Ghamsari, Morteza; Alamdari, Sanaz; Han, Wooje; Park, Hyung-Ho

2017-01-01

Nanoscale ZnO is one of the best choices for ultraviolet (UV) protection, not only because of its antimicrobial properties but also due to its potential application for UV preservation. However, the behavior of nanostructured thin ZnO films and long-term effects of UV-radiation exposure have not been studied yet. In this study, we investigated the UV-protection ability of sol gel-derived thin ZnO films after different exposure times. Scanning electron microscopy, atomic force microscopy, and UV-visible optical spectroscopy were carried out to study the structure and optical properties of the ZnO films as a function of the UV-irradiation time. The results obtained showed that the prepared thin ZnO films were somewhat transparent under the visible wavelength region and protective against UV radiation. The UV-protection factor was 50+ for the prepared samples, indicating that they were excellent UV protectors. The deposited thin ZnO films demonstrated promising antibacterial potential and significant light absorbance in the UV range. The experimental results suggest that the synthesized samples have potential for applications in the health care field. PMID:28096668

Optimization of rotational speed for growing BaFe12O19 thin films using spin coating

NASA Astrophysics Data System (ADS)

Budiawanti, S.; Soegijono, B.; Mudzakir, I.; Suharno, Fadillah, L.

2017-07-01

Barium ferrite (BaFe12O19, BaM) thin films were fabricated by the spin coating of precursors obtained by using a sol-gel method. The effects of the rotational speed on the spin-coating process for growing a BaM thin film were investigated in this study. Coated films were heat-deposited at different rotational speeds ranging from 2000 to 4000 rpm, while the number of layers was set to nine. Further, the effect of the number of layers on the growth of BaM thin films was discussed. For this purpose, we take the layers number 1 to 12 and take the constant rotational speed of 3000 rpm. All the film were characterized using X-Ray diffraction, Scanning Electron microscope, and Energy-dispersive X-Ray spectroscopy and Vibrating Sample Magnetometer. It was found that by increasing the rotational speed the amount of material deposited on the Si substrate decreased. The measured grain size of the BaM thin film was nearly similar for three three different rotational speeds. However, the grain size was found to increase the number of layers.

Fabrication of band gap engineered nanostructured tri-metallic (Mn-Co-Ti) oxide thin films

NASA Astrophysics Data System (ADS)

Mansoor, Muhammad Adil; Yusof, Farazila Binti; Nay-Ming, Huang

2018-04-01

In continuation of our previous studies on photoelectrochemical (PEC) properties of titanium based composite oxide thin films, an effort is made to develop thin films of 1:1:2 manganese-cobalt-titanium oxide composite, Mn2O3-Co2O3-4TiO2 (MCT), using Co(OAc)2 and a bimetallic manganese-titanium complex, [Mn2Ti4(TFA)8(THF)6(OH)4(O)2].0.4THF (1), where OAc = acetato, TFA = trifluoroacetato and THF = tetrahydrofuran, via aerosol-assisted chemical vapour deposition (AACVD) technique. The X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and energy dispersive X-ray (EDX) spectroscopic analyses confirmed formation of thin film of Mn2O3-Co2O3-4TiO2 composite material with uniformly distributed agglomerated particles. The average size of 39.5 nm, of the particles embedded inside agglomerates, was estimated by Scherer's equation. Further, UV-Vis spectroscopy was used to estimate the band gap of 2.62 eV for MCT composite thin film.

Characteristics research of pressure sensor based on nanopolysilicon thin films resistors

NASA Astrophysics Data System (ADS)

Zhao, Xiaofeng; Li, Dandan; Wen, Dianzhong

2017-10-01

To further improve the sensitivity temperature characteristics of pressure sensor, a kind of pressure sensor taking nanopolysilicon thin films as piezoresistors is proposed in this paper. On the basis of the microstructure analysis by X-ray diffraction (XRD) and scanning electron microscope (SEM) tests, the preparing process of nanopolysilicon thin films is optimized. The effects of film thickness and annealing temperature on the micro-structure of nanopolysilicon thin films were studied, respectively. In order to realize the measurement of external pressure, four nanopolysilicon thin films resistors were arranged at the edges of square silicon diaphragm connected to a Wheatstone bridge, and the chip of the sensor was designed and fabricated on a 〈100〉 orientation silicon wafer by microelectromechanical system (MEMS) technology. Experimental result shows that when I = 6.80 mA, the sensitivity of the sensor PS-1 is 0.308 mV/kPa, and the temperature coefficient of sensitivity (TCS) is about -1742 ppm/∘C in the range of -40-140∘C. It is possible to obviously improve the sensitivity temperature characteristics of pressure sensor by the proposed sensors.

Antimicrobial activity of biopolymeric thin films containing flavonoid natural compounds and silver nanoparticles fabricated by MAPLE: A comparative study

NASA Astrophysics Data System (ADS)

Cristescu, R.; Visan, A.; Socol, G.; Surdu, A. V.; Oprea, A. E.; Grumezescu, A. M.; Chifiriuc, M. C.; Boehm, R. D.; Yamaleyeva, D.; Taylor, M.; Narayan, R. J.; Chrisey, D. B.

2016-06-01

The purpose of this study was to investigate the interactions between microorganisms, including the planktonic and adherent organisms, and biopolymer (polyvinylpyrrolidone), flavonoid (quercetin dihydrate and resveratrol)-biopolymer, and silver nanoparticles-biopolymer composite thin films that were deposited using matrix assisted pulsed laser evaporation (MAPLE). A pulsed KrF* excimer laser source was used to deposit the aforementioned composite thin films, which were characterized using Fourier transform infrared spectroscopy (FT-IR), infrared microscopy (IRM), scanning electron microscopy (SEM), Grazing incidence X-ray diffraction (GIXRD) and atomic force microscopy (AFM). The antimicrobial activity of thin films was quantified using an adapted disk diffusion assay against Gram-positive and Gram-negative bacteria strains. FT-IR, AFM and SEM studies confirmed that MAPLE may be used to fabricate thin films with chemical properties corresponding to the input materials as well as surface properties that are appropriate for medical use. The silver nanoparticles and flavonoid-containing films exhibited an antimicrobial activity both against Gram-positive and Gram-negative bacterial strains demonstrating the potential use of these hybrid systems for the development of novel antimicrobial strategies.

Preparation of an orthodontic bracket coated with an nitrogen-doped TiO(2-x)N(y) thin film and examination of its antimicrobial performance.

PubMed

Cao, Baocheng; Wang, Yuhua; Li, Na; Liu, Bin; Zhang, Yingjie

2013-01-01

A bracket coated with a nitrogen-doped (N-doped) TiO(2-x)N(y) thin film was prepared using the RF magnetron sputtering method. The physicochemical properties of the thin film were measured using X-ray diffraction and energy-dispersive X-ray spectrometry, while the antimicrobial activity of the bracket against common oral pathogenic microbes was assessed on the basis of colony counts. The rate of antimicrobial activity of the bracket coated with nano-TiO(2-x)N(y) thin film against Streptococcus mutans, Lactobacillus acidophilus, Actinomyces viscous, and Candida albicans was 95.19%, 91.00%, 69.44%, and 98.86%, respectively. Scanning electron microscopy showed that fewer microbes adhered to the surface of this newly designed bracket than to the surface of the normal edgewise bracket. The brackets coated with the N-doped TiO(2-x)N(y) thin film showed high antimicrobial and bacterial adhesive properties against normal oral pathogenic bacterial through visible light, which is effective in prevention of enamel demineralization and gingivitis in orthodontic patients.

Transparent nanostructured Fe-doped TiO2 thin films prepared by ultrasonic assisted spray pyrolysis technique

NASA Astrophysics Data System (ADS)

Rasoulnezhad, Hossein; Hosseinzadeh, Ghader; Ghasemian, Naser; Hosseinzadeh, Reza; Homayoun Keihan, Amir

2018-05-01

Nanostructured TiO2 and Fe-doped TiO2 thin films with high transparency were deposited on glass substrate through ultrasonic-assisted spray pyrolysis technique and were used in the visible light photocatalytic degradation of MB dye. The resulting thin films were characterized by scanning electron microscopy (SEM), Raman spectroscopy, photoluminescence spectroscopy, x-ray diffraction (XRD), and UV-visible absorption spectroscopy techniques. Based on Raman spectroscopy results, both of the TiO2 and Fe-doped TiO2 films have anatase crystal structure, however, because of the insertion of Fe in the structure of TiO2 some point defects and oxygen vacancies are formed in the Fe-doped TiO2 thin film. Presence of Fe in the structure of TiO2 decreases the band gap energy of TiO2 and also reduces the electron–hole recombination rate. Decreasing of the electron–hole recombination rate and band gap energy result in the enhancement of the visible light photocatalytic activity of the Fe-doped TiO2 thin film.

Structural and optical properties of p-quaterphenyl thin films and application in organic/inorganic photodiodes

NASA Astrophysics Data System (ADS)

Attia, A. A.; Saadeldin, M. M.; Soliman, H. S.; Gadallah, A.-S.; Sawaby, K.

2016-12-01

Para-quaterpheny1 (p-4pheny1) thin films were deposited by the thermal evaporation method on glass/quartz substrates for structural and optical investigations. The XRD of p-4phenyl thin films showed that the as-deposited films have a monoclinic structure. The surface morphology of p-4phenyl thin film was studied using scanning electron microscope. The absorption spectrum of p-4phenyl thin film recorded in the wavelength range 200-2500 nm. Photoluminescence measurements revealed two emission peaks at 435 and 444 nm using N2-laser (337.8 nm). The energy gap obtained from the absorption and photoluminescence data was found to be 2.87 and 2.74 eV respectively with Stokes shift value of 0.13 eV. The current-voltage characteristics of p-4phenyl/p-Si heterojunction have been recorded in the dark and under illumination of laser (337.8 nm). Responsivity, Detectivity, External quantum efficiency and Response speed of (Au/p-4pheny1/p-Si/Al) photodetector have been determined using different laser sources at -1 V bias.

Impact of nanostructured thin ZnO film in ultraviolet protection.

PubMed

Sasani Ghamsari, Morteza; Alamdari, Sanaz; Han, Wooje; Park, Hyung-Ho

2017-01-01

Nanoscale ZnO is one of the best choices for ultraviolet (UV) protection, not only because of its antimicrobial properties but also due to its potential application for UV preservation. However, the behavior of nanostructured thin ZnO films and long-term effects of UV-radiation exposure have not been studied yet. In this study, we investigated the UV-protection ability of sol gel-derived thin ZnO films after different exposure times. Scanning electron microscopy, atomic force microscopy, and UV-visible optical spectroscopy were carried out to study the structure and optical properties of the ZnO films as a function of the UV-irradiation time. The results obtained showed that the prepared thin ZnO films were somewhat transparent under the visible wavelength region and protective against UV radiation. The UV-protection factor was 50+ for the prepared samples, indicating that they were excellent UV protectors. The deposited thin ZnO films demonstrated promising antibacterial potential and significant light absorbance in the UV range. The experimental results suggest that the synthesized samples have potential for applications in the health care field.

Effect of lead ion concentration on the structural and optical properties of nano-crystalline PbS thin films

NASA Astrophysics Data System (ADS)

Zaman, S.; Mehmood, S. K.; Mansoor, M.; Asim, M. M.

2014-06-01

PbS thin films have received considerable attention because of their potential applications in opto-electronics applications. Spontaneous reaction of lead acetate and thiourea in aqueous hydrazine hydrate has been used for depositing PbS thin films on glass substrates. Structural and optical properties of PbS thin films are greatly influenced by the morality of the reactants and crystal defects in the lattice. Our work focuses on the variation in lead ion concentration and its effect on the structural and optical properties of PbS thin films. The deposited films were analyzed using XRD, SEM, spectrophotometer and dark resistance measurement. XRD patterns indicated the formation of major phase of nano crystalline PbS with minor presence of lead oxide phase. We also noticed that peak intensity ratio of I111/I200 varied by changing the Pb ion concentration. The film thickness and dark resistance increased whereas optical band gap decreased with the decreasing Pb ion concentration. SEM scans showed that the grain size is less than 100 nm and is not affected by varying Pb ion concentration.

Highly spatially resolved structural and optical investigation of Bi nanoparticles in Y-Er disilicate thin films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Scarangella, A.; Dipartimento di Fisica e Astronomia, Università di Catania, Via S. Sofia 64, 95123 Catania; Amiard, G.

2016-08-08

Er-containing silicon compatible materials have been widely used as infrared emitters for microphotonics application. In this field, the additional introduction of a proper sensitizer permits to increase the Er excitation cross sections, thus increasing its optical efficiency. This work aims to investigate the influence of a post-transition metal, bismuth, on the optical properties of erbium-yttrium disilicate thin films synthesized by magnetron co-sputtering. After thermal treatments at 1000 °C in O{sub 2} or N{sub 2} environment, the presence of small precipitates, about 6 nm in diameter, was evidenced by transmission electron microscopy analyses. The spatially resolved chemical nature of the nanoparticles was discernedmore » in the Si and O rich environments by means of scanning transmission electron microscopy–energy dispersive X-ray and scanning transmission electron microscopy–electron energy loss spectroscopy analyses performed with nanometric resolution. In particular, metallic Bi nanoparticles were stabilized in the N{sub 2} environment, being strongly detrimental for the Er emission. A different scenario was instead observed in O{sub 2}, where the formation of Bi silicate nanoparticles was demonstrated with the support of photoluminescence excitation spectroscopy. In particular, a broad band peaked at 255 nm, correlated to the excitation band of Bi silicate nanoparticles, was identified in Er excitation spectrum. Thus Bi silicate clusters act as sensitizer for Er ions, permitting to improve Er emission up to 250 times with respect to the resonant condition. Moreover, the Er decay time increases in the presence of the Bi silicate nanoparticles that act as cages for Er ions. These last results permit to further increase Er optical efficiency in the infrared range, suggesting (Bi + Er)-Y disilicate as a good candidate for applications in microphotonics.« less

Subgrain boundary analyses in deformed orthopyroxene by TEM/STEM with EBSD-FIB sample preparation technique

NASA Astrophysics Data System (ADS)

Kogure, Toshihiro; Raimbourg, Hugues; Kumamoto, Akihito; Fujii, Eiko; Ikuhara, Yuichi

2014-12-01

High-resolution structure analyses using electron beam techniques have been performed for the investigation of subgrain boundaries (SGBs) in deformed orthopyroxene (Opx) in mylonite from Hidaka Metamorphic Belt, Hokkaido, Japan, to understand ductile deformation mechanism of silicate minerals in shear zones. Scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD) analysis of Opx porphyroclasts in the mylonitic rock indicated that the crystal orientation inside the Opx crystals gradually changes by rotation about the b-axis by SGBs and crystal folding. In order to observe the SGBs along the b-axis by transmission electron microscopy (TEM) or scanning TEM (STEM), the following sample preparation protocol was adopted. First, petrographic thin sections were slightly etched with hydrofluoric acid to identify SGBs in SEM. The Opx crystals whose b-axes were oriented close to the normal of the surface were identified by EBSD, and the areas containing SGBs were picked and thinned for (S) TEM analysis with a focused ion beam instrument with micro-sampling system. High-resolution TEM imaging of the SGBs in Opx revealed various boundary structures from a periodic array of dissociated (100) [001] edge dislocations to partially or completely incoherent crystals, depending on the misorientation angle. Atomic-resolution STEM imaging clearly confirmed the formation of clinopyroxene (Cpx) structure between the dissociated partial dislocations. Moreover, X-ray microanalysis in STEM revealed that the Cpx contains a considerable amount of calcium replacing iron. Such chemical inhomogeneity may limit glide motion of the dislocation and eventually the plastic deformation of the Opx porphyroclasts at a low temperature. Chemical profiles across the high-angle incoherent SGB also showed an enrichment of the latter in calcium at the boundary, suggesting that SGBs are an efficient diffusion pathway of calcium out of host Opx grain during cooling.

Effect of cadmium incorporation on the properties of zinc oxide thin films

NASA Astrophysics Data System (ADS)

Bharath, S. P.; Bangera, Kasturi V.; Shivakumar, G. K.

2018-02-01

Cd x Zn1- x O (0 ≤ x ≤ 0.20) thin films are deposited on soda lime glass substrates using spray pyrolysis technique. To check the thermal stability, Cd x Zn1- x O thin films are subjected to annealing. Both the as-deposited and annealed Cd x Zn1- x O thin films are characterized using X-ray diffraction (XRD), scanning electron microscope (SEM) and energy-dispersive X-ray analysis (EDAX) to check the structural, surface morphological and compositional properties, respectively. XRD analysis reveals that the both as-deposited and annealed Cd x Zn1- x O thin films are (002) oriented with wurtzite structure. SEM studies confirm that as-deposited, as well as annealed Cd x Zn1- x O thin films are free from pinholes and cracks. Compositional analysis shows the deficiency in Cd content after annealing. Optical properties evaluated from UV-Vis spectroscopy shows red shift in the band gap for Cd x Zn1- x O thin films. Electrical property measured using two probe method shows a decrease in the resistance after Cd incorporation. The results indicate that cadmium can be successfully incorporated in zinc oxide thin films to achieve structural changes in the properties of films.

Ultrashort pulse laser dicing of thin Si wafers: the influence of laser-induced periodic surface structures on the backside breaking strength

NASA Astrophysics Data System (ADS)

Domke, Matthias; Egle, Bernadette; Piredda, Giovanni; Stroj, Sandra; Fasching, Gernot; Bodea, Marius; Schwarz, Elisabeth

2016-11-01

High power electronic chips are usually fabricated on about 50 µm thin Si wafers to improve heat dissipation. At these chip thicknesses mechanical dicing becomes challenging. Chippings may occur at the cutting edges, which reduce the mechanical stability of the die. Thermal load changes could then lead to sudden chip failure. Ultrashort pulsed lasers are a promising tool to improve the cutting quality, because thermal side effects can be reduced to a minimum. However, laser-induced periodic surface structures occur at the sidewalls and at the trench bottom during scribing. The goal of this study was to investigate the influence of these periodic structures on the backside breaking strength of the die. An ultrafast laser with a pulse duration of 380 fs and a wavelength of 1040 nm was used to cut a wafer into single chips. The pulse energy and the number of scans was varied. The cuts in the wafer were investigated using transmitted light microscopy, the sidewalls of the cut chips were investigated using scanning electron and confocal microscopy, and the breaking strength was evaluated using the 3-point bending test. The results indicated that periodic holes with a distance of about 20-30 µm were formed at the bottom of the trench, if the number of scans was set too low to completely cut the wafer; the wafer was only perforated. Mechanical breaking of the bridges caused 5 µm deep kerfs in the sidewall. These kerfs reduced the breaking strength at the backside of the chip to about 300 MPa. As the number of scans was increased, the bridges were ablated and the wafer was cut completely. Periodic structures were observed on the sidewall; the roughness was below 1 µm. The surface roughness remained on a constant level even when the number of scans was doubled. However, the periodic structures on the sidewall seemed to vanish and the probability to remove local flaws increases with the number of scans. As a consequence, the breaking strength was increased to about 700 MPa.

Nanobelt formation of magnesium hydroxide sulfate hydrate via a soft chemistry process.

PubMed

Zhou, Zhengzhi; Sun, Qunhui; Hu, Zeshan; Deng, Yulin

2006-07-13

The nanobelt formation of magnesium hydroxide sulfate hydrate (MHSH) via a soft chemistry approach using carbonate salt and magnesium sulfate as reactants was successfully demonstrated. X-ray diffraction (XRD), energy dispersion X-ray spectra (EDS), selected area electron diffraction (SAED), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) analysis revealed that the MHSH nanobelts possessed a thin belt structure (approximately 50 nm in thickness) and a rectangular cross profile (approximately 200 nm in width). The MHSH nanobelts suffered decomposition under electron beam irradiation during TEM observation and formed MgO with the pristine nanobelt morphology preserved. The formation process of the MHSH nanobelts was studied by tracking the morphology of the MHSH nanobelts during the reaction. A possible chemical reaction mechanism is proposed.

Nanoscale-Barrier Formation Induced by Low-Dose Electron-Beam Exposure in Ultrathin MoS2 Transistors.

PubMed

Matsunaga, Masahiro; Higuchi, Ayaka; He, Guanchen; Yamada, Tetsushi; Krüger, Peter; Ochiai, Yuichi; Gong, Yongji; Vajtai, Robert; Ajayan, Pulickel M; Bird, Jonathan P; Aoki, Nobuyuki

2016-10-05

Utilizing an innovative combination of scanning-probe and spectroscopic techniques, supported by first-principles calculations, we demonstrate how electron-beam exposure of field-effect transistors, implemented from ultrathin molybdenum disulfide (MoS 2 ), may cause nanoscale structural modifications that in turn significantly modify the electrical operation of these devices. Quite surprisingly, these modifications are induced by even the relatively low electron doses used in conventional electron-beam lithography, which are found to induce compressive strain in the atomically thin MoS 2 . Likely arising from sulfur-vacancy formation in the exposed regions, the strain gives rise to a local widening of the MoS 2 bandgap, an idea that is supported both by our experiment and by the results of first-principles calculations. A nanoscale potential barrier develops at the boundary between exposed and unexposed regions and may cause extrinsic variations in the resulting electrical characteristics exhibited by the transistor. The widespread use of electron-beam lithography in nanofabrication implies that the presence of such strain must be carefully considered when seeking to harness the potential of atomically thin transistors. At the same time, this work also promises the possibility of exploiting the strain as a means to achieve "bandstructure engineering" in such devices.

Effect of an Interfacial Layer on Electron Tunneling through Atomically Thin Al2O3 Tunnel Barriers.

PubMed

Wilt, Jamie; Sakidja, Ridwan; Goul, Ryan; Wu, Judy Z

2017-10-25

Electron tunneling through high-quality, atomically thin dielectric films can provide a critical enabling technology for future microelectronics, bringing enhanced quantum coherent transport, fast speed, small size, and high energy efficiency. A fundamental challenge is in controlling the interface between the dielectric and device electrodes. An interfacial layer (IL) will contain defects and introduce defects in the dielectric film grown atop, preventing electron tunneling through the formation of shorts. In this work, we present the first systematic investigation of the IL in Al 2 O 3 dielectric films of 1-6 Å's in thickness on an Al electrode. We integrated several advanced approaches: molecular dynamics to simulate IL formation, in situ high vacuum sputtering atomic layer deposition (ALD) to synthesize Al 2 O 3 on Al films, and in situ ultrahigh vacuum scanning tunneling spectroscopy to probe the electron tunneling through the Al 2 O 3 . The IL had a profound effect on electron tunneling. We observed a reduced tunnel barrier height and soft-type dielectric breakdown which indicate that defects are present in both the IL and in the Al 2 O 3 . The IL forms primarily due to exposure of the Al to trace O 2 and/or H 2 O during the pre-ALD heating step of fabrication. As the IL was systematically reduced, by controlling the pre-ALD sample heating, we observed an increase of the ALD Al 2 O 3 barrier height from 0.9 to 1.5 eV along with a transition from soft to hard dielectric breakdown. This work represents a key step toward the realization of high-quality, atomically thin dielectrics with electron tunneling for the next generation of microelectronics.

Extremely thin layer plastification for focused-ion beam scanning electron microscopy: an improved method to study cell surfaces and organelles of cultured cells.

PubMed

VAN Donselaar, E G; Dorresteijn, B; Popov-Čeleketić, D; VAN DE Wetering, W J; Verrips, T C; Boekhout, T; Schneijdenberg, C T W M; Xenaki, A T; VAN DER Krift, T P; Müller, W H

2018-03-25

Since the recent boost in the usage of electron microscopy in life-science research, there is a great need for new methods. Recently minimal resin embedding methods have been successfully introduced in the sample preparation for focused-ion beam scanning electron microscopy (FIB-SEM). In these methods several possibilities are given to remove as much resin as possible from the surface of cultured cells or multicellular organisms. Here we introduce an alternative way in the minimal resin embedding method to remove excess of resin from two widely different cell types by the use of Mascotte filter paper. Our goal in correlative light and electron microscopic studies of immunogold-labelled breast cancer SKBR3 cells was to visualise gold-labelled HER2 plasma membrane proteins as well as the intracellular structures of flat and round cells. We found a significant difference (p < 0.001) in the number of gold particles of selected cells per 0.6 μm 2 cell surface: on average a flat cell contained 2.46 ± 1.98 gold particles, and a round cell 5.66 ± 2.92 gold particles. Moreover, there was a clear difference in the subcellular organisation of these two cells. The round SKBR3 cell contained many organelles, such as mitochondria, Golgi and endoplasmic reticulum, when compared with flat SKBR3 cells. Our next goal was to visualise crosswall associated organelles, septal pore caps, of Rhizoctonia solani fungal cells by the combined use of a heavy metal staining and our extremely thin layer plastification (ETLP) method. At low magnifications this resulted into easily finding septa which appeared as bright crosswalls in the back-scattered electron mode in the scanning electron microscope. Then, a septum was selected for FIB-SEM. Cross-sectioned views clearly revealed the perforate septal pore cap of R. solani next to other structures, such as mitochondria, endoplasmic reticulum, lipid bodies, dolipore septum, and the pore channel. As the ETLP method was applied on two widely different cell types, the use of the ETLP method will be beneficial to correlative studies of other cell model systems and multicellular organisms. © 2018 The Authors. Journal of Microscopy published by JohnWiley & Sons Ltd on behalf of Royal Microscopical Society.

Optical constants, dispersion energy parameters and dielectric properties of ultra-smooth nanocrystalline BiVO4 thin films prepared by rf-magnetron sputtering

NASA Astrophysics Data System (ADS)

Sarkar, S.; Das, N. S.; Chattopadhyay, K. K.

2014-07-01

BiVO4 thin films have been prepared through radio frequency (rf) magnetron sputtering of a pre-fabricated BiVO4 target on ITO coated glass (ITO-glass) substrate and bare glass substrates. BiVO4 target material was prepared through solid-state reaction method by heating Bi2O3 and V2O5 mixture at 800 °C for 8 h. The films were characterized by X-ray diffraction, UV-Vis spectroscopy, LCR meter, field emission scanning electron microscopy, transmission electron microscopy and atomic force microscopy. BiVO4 thin films deposited on the ITO-glass substrate are much smoother compared to the thin films prepared on bare glass substrate. The rms surface roughness calculated from the AFM images comes out to be 0.74 nm and 4.2 nm for the films deposited on the ITO-glass substrate and bare glass substrate for the deposition time 150 min respectively. Optical constants and energy dispersion parameters of these extra-smooth BiVO4 thin films have been investigated in detail. Dielectric properties of the BiVO4 thin films on ITO-glass substrate were also investigated. The frequency dependence of dielectric constant of the BiVO4 thin films has been measured in the frequency range from 20 Hz to 2 MHz. It was found that the dielectric constant increased from 145 to 343 at 20 Hz as the film thickness increased from 90 nm to 145 nm (deposition time increased from 60 min to 150 min). It shows higher dielectric constant compared to the literature value of BiVO4.

Environmentally induced chemical and morphological heterogeneity of zinc oxide thin films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jiang, Hua; Chou, Kang Wei; Petrash, Stanislas

Zinc oxide (ZnO) thin films have been reported to suffer from degradation in electrical properties, when exposed to elevated heat and humidity, often leading to failures of electronic devices containing ZnO films. This degradation appears to be linked to water and oxygen penetration into the ZnO film. However, a direct observation in the ZnO film morphological evolution detailing structural and chemical changes has been lacking. Here, we systematically investigated the chemical and morphological heterogeneities of ZnO thin films caused by elevated heat and humidity, simulating an environmental aging. X-ray fluorescence microscopy, X-ray absorption spectroscopy, grazing incidence small angle and widemore » angle X-ray scattering, scanning electron microscopy (SEM), ultra-high-resolution SEM, and optical microscopy were carried out to examine ZnO and Al-doped ZnO thin films on two different substrates—silicon wafers and flexible polyethylene terephthalate (PET) films. In the un-doped ZnO thin film, the simulated environmental aging is resulting in pin-holes. In the Al-doped ZnO thin films, significant morphological changes occurred after the treatment, with an appearance of platelet-shaped structures that are 100–200 nm wide by 1 μm long. Synchrotron x-ray characterization further confirmed the heterogeneity in the aged Al-doped ZnO, showing the formation of anisotropic structures and disordering. X-ray diffraction and X-ray absorption spectroscopy indicated the formation of a zinc hydroxide in the aged Al-doped films. Utilizing advanced characterization methods, our studies provided information with an unprecedented level of details and revealed the chemical and morphologically heterogeneous nature of the degradation in ZnO thin films.« less

Environmentally induced chemical and morphological heterogeneity of zinc oxide thin films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jiang, Hua; Chou, Kang Wei; Petrash, Stanislas

Zinc oxide (ZnO) thin films have been reported to suffer from degradation in electrical properties, when exposed to elevated heat and humidity, often leading to failures of electronic devices containing ZnO films. This degradation appears to be linked to water and oxygen penetration into the ZnO film. However, a direct observation in the ZnO film morphological evolution detailing structural and chemical changes has been lacking. Here, we systematically investigated the chemical and morphological heterogeneities of ZnO thin films caused by elevated heat and humidity, simulating an environmental aging. X-ray fluorescence microscopy, X-ray absorption spectroscopy, grazing incidence small angle and widemore » angle X-ray scattering, scanning electron microscopy (SEM), ultra-high-resolution SEM, and optical microscopy were carried out to examine ZnO and Al-doped ZnO thin films on two different substrates—silicon wafers and flexible polyethylene terephthalate (PET) films. In the un-doped ZnO thin film, the simulated environmental aging is resulting in pin-holes. In the Al-doped ZnO thin films, significant morphological changes occurred after the treatment, with an appearance of platelet-shaped structures that are 100–200 nm wide by 1μm long. Synchrotron x-ray characterization further confirmed the heterogeneity in the aged Al-doped ZnO, showing the formation of anisotropic structures and disordering. X-ray diffraction and X-ray absorption spectroscopy indicated the formation of a zinc hydroxide in the aged Al-doped films. In conclusion, utilizing advanced characterization methods, our studies provided information with an unprecedented level of details and revealed the chemical and morphologically heterogeneous nature of the degradation in ZnO thin films.« less

Environmentally induced chemical and morphological heterogeneity of zinc oxide thin films

DOE PAGES

Jiang, Hua; Chou, Kang Wei; Petrash, Stanislas; ...

2016-09-02

Zinc oxide (ZnO) thin films have been reported to suffer from degradation in electrical properties, when exposed to elevated heat and humidity, often leading to failures of electronic devices containing ZnO films. This degradation appears to be linked to water and oxygen penetration into the ZnO film. However, a direct observation in the ZnO film morphological evolution detailing structural and chemical changes has been lacking. Here, we systematically investigated the chemical and morphological heterogeneities of ZnO thin films caused by elevated heat and humidity, simulating an environmental aging. X-ray fluorescence microscopy, X-ray absorption spectroscopy, grazing incidence small angle and widemore » angle X-ray scattering, scanning electron microscopy (SEM), ultra-high-resolution SEM, and optical microscopy were carried out to examine ZnO and Al-doped ZnO thin films on two different substrates—silicon wafers and flexible polyethylene terephthalate (PET) films. In the un-doped ZnO thin film, the simulated environmental aging is resulting in pin-holes. In the Al-doped ZnO thin films, significant morphological changes occurred after the treatment, with an appearance of platelet-shaped structures that are 100–200 nm wide by 1μm long. Synchrotron x-ray characterization further confirmed the heterogeneity in the aged Al-doped ZnO, showing the formation of anisotropic structures and disordering. X-ray diffraction and X-ray absorption spectroscopy indicated the formation of a zinc hydroxide in the aged Al-doped films. In conclusion, utilizing advanced characterization methods, our studies provided information with an unprecedented level of details and revealed the chemical and morphologically heterogeneous nature of the degradation in ZnO thin films.« less

Tailoring and optimization of optical properties of CdO thin films for gas sensing applications

NASA Astrophysics Data System (ADS)

Rajput, Jeevitesh K.; Pathak, Trilok K.; Kumar, V.; Swart, H. C.; Purohit, L. P.

2018-04-01

Cadmium oxide (CdO) thin films have been deposited onto glass substrates using different molar concentrations (0.2 M, 0.5 M and 0.8 M) of cadmium acetate precursor solutions using a sol-gel spin coating technique. The structural, morphological, optical and electrical results are presented. X-ray diffraction patterns indicated that the CdO films of different molarity have a stable cubic structure with a (111) preferred orientation at low molar concentration. Scanning electron microscopy images revealed that the films adopted a rectangular to cauliflower like morphology. The optical transmittance of the thin films was observed in the range 200-800 nm and it was found that the 0.2 M CdO thin films showed about 83% transmission in the visible region. The optical band gap energy of the thin films was found to vary from 2.10 to 3.30 eV with the increase in molar concentration of the solution. The electrical resistance of the 0.5 M thin film was found to be 1.56 kΩ. The oxygen sensing response was observed between 20-33% in the low temperature range (32-200 °C).

Copper-Zinc-Tin-Sulfur Thin Film Using Spin-Coating Technology

PubMed Central

Yeh, Min-Yen; Lei, Po-Hsun; Lin, Shao-Hsein; Yang, Chyi-Da

2016-01-01

Cu2ZnSnS4 (CZTS) thin films were deposited on glass substrates by using spin-coating and an annealing process, which can improve the crystallinity and morphology of the thin films. The grain size, optical gap, and atomic contents of copper (Cu), zinc (Zn), tin (Sn), and sulfur (S) in a CZTS thin film absorber relate to the concentrations of aqueous precursor solutions containing copper chloride (CuCl2), zinc chloride (ZnCl2), tin chloride (SnCl2), and thiourea (SC(NH2)2), whereas the electrical properties of CZTS thin films depend on the annealing temperature and the atomic content ratios of Cu/(Zn + Sn) and Zn/Sn. All of the CZTS films were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDXS), Raman spectroscopy, and Hall measurements. Furthermore, CZTS thin film was deposited on an n-type silicon substrate by using spin-coating to form an Mo/p-CZTS/n-Si/Al heterostructured solar cell. The p-CZTS/n-Si heterostructured solar cell showed a conversion efficiency of 1.13% with Voc = 520 mV, Jsc = 3.28 mA/cm2, and fill-factor (FF) = 66%. PMID:28773647

Highly uniform resistive switching properties of amorphous InGaZnO thin films prepared by a low temperature photochemical solution deposition method.

PubMed

Hu, Wei; Zou, Lilan; Chen, Xinman; Qin, Ni; Li, Shuwei; Bao, Dinghua

2014-04-09

We report on highly uniform resistive switching properties of amorphous InGaZnO (a-IGZO) thin films. The thin films were fabricated by a low temperature photochemical solution deposition method, a simple process combining chemical solution deposition and ultraviolet (UV) irradiation treatment. The a-IGZO based resistive switching devices exhibit long retention, good endurance, uniform switching voltages, and stable distribution of low and high resistance states. Electrical conduction mechanisms were also discussed on the basis of the current-voltage characteristics and their temperature dependence. The excellent resistive switching properties can be attributed to the reduction of organic- and hydrogen-based elements and the formation of enhanced metal-oxide bonding and metal-hydroxide bonding networks by hydrogen bonding due to UV irradiation, based on Fourier-transform-infrared spectroscopy, X-ray photoelectron spectroscopy, and Field emission scanning electron microscopy analysis of the thin films. This study suggests that a-IGZO thin films have potential applications in resistive random access memory and the low temperature photochemical solution deposition method can find the opportunity for further achieving system on panel applications if the a-IGZO resistive switching cells were integrated with a-IGZO thin film transistors.

Nanoporous structures on ZnO thin films

NASA Astrophysics Data System (ADS)

Gür, Emre; Kılıç, Bayram; Coşkun, C.; Tüzemen, S.; Bayrakçeken, Fatma

2010-01-01

Porous structures were formed on ZnO thin films which were grown by an electrochemical deposition (ECD) method. The growth processes were carried out in a solution of dimethylsulfoxide (DMSO) zinc perchlorate, Zn(ClO 4) 2, at 120 ∘C on indium tin oxide (ITO) substrates. Optical and structural characterizations of electrochemically grown ZnO thin films have shown that the films possess high (0002) c-axis orientation, high nucleation, high intensity and low FWHM of UV emission at the band edge region and a sharp UV absorption edge. Nanoporous structures were formed via self-assembled monolayers (SAMs) of hexanethiol (C 6SH) and dodecanethiol (C 12SH). Scanning electron microscope (SEM) measurements showed that while a nanoporous structure (pore radius 20 nm) is formed on the ZnO thin films by hexanathiol solution, a macroporous structure (pore radius 360 nm) is formed by dodecanethiol solution. No significant variation is observed in X-ray diffraction (XRD) measurements on the ZnO thin films after pore formation. However, photoluminescence (PL) measurements showed that green emission is observed as the dominant emission for the macroporous structures, while no variation is observed for the thin film nanoporous ZnO sample.

Developing high-transmittance heterojunction diodes based on NiO/TZO bilayer thin films

PubMed Central

2013-01-01

In this study, radio frequency magnetron sputtering was used to deposit nickel oxide thin films (NiO, deposition power of 100 W) and titanium-doped zinc oxide thin films (TZO, varying deposition powers) on glass substrates to form p(NiO)-n(TZO) heterojunction diodes with high transmittance. The structural, optical, and electrical properties of the TZO and NiO thin films and NiO/TZO heterojunction devices were investigated with scanning electron microscopy, X-ray diffraction (XRD) patterns, UV-visible spectroscopy, Hall effect analysis, and current-voltage (I-V) analysis. XRD analysis showed that only the (111) diffraction peak of NiO and the (002) and (004) diffraction peaks of TZO were observable in the NiO/TZO heterojunction devices, indicating that the TZO thin films showed a good c-axis orientation perpendicular to the glass substrates. When the sputtering deposition power for the TZO thin films was 100, 125, and 150 W, the I-V characteristics confirmed that a p-n junction characteristic was successfully formed in the NiO/TZO heterojunction devices. We show that the NiO/TZO heterojunction diode was dominated by the space-charge limited current theory. PMID:23634999

Silicon solar cell performance deposited by diamond like carbon thin film ;Atomic oxygen effects;

NASA Astrophysics Data System (ADS)

Aghaei, Abbas Ail; Eshaghi, Akbar; Karami, Esmaeil

2017-09-01

In this research, a diamond-like carbon thin film was deposited on p-type polycrystalline silicon solar cell via plasma-enhanced chemical vapor deposition method by using methane and hydrogen gases. The effect of atomic oxygen on the functioning of silicon coated DLC thin film and silicon was investigated. Raman spectroscopy, field emission scanning electron microscopy, atomic force microscopy and attenuated total reflection-Fourier transform infrared spectroscopy were used to characterize the structure and morphology of the DLC thin film. Photocurrent-voltage characteristics of the silicon solar cell were carried out using a solar simulator. The results showed that atomic oxygen exposure induced the including oxidation, structural changes, cross-linking reactions and bond breaking of the DLC film; thus reducing the optical properties. The photocurrent-voltage characteristics showed that although the properties of the fabricated thin film were decreased after being exposed to destructive rays, when compared with solar cell without any coating, it could protect it in atomic oxygen condition enhancing solar cell efficiency up to 12%. Thus, it can be said that diamond-like carbon thin layer protect the solar cell against atomic oxygen exposure.

Fabrication of polymerized crystalline colloidal array thin film modified β-cyclodextrin polymer for paraoxon-ethyl and parathion-ethyl detection.

PubMed

Bui, Minh-Phuong N; Seo, Seong S

2014-01-01

We have developed an optical chemical sensor for the detection of organophosphate (OP) compounds using a polymerized crystalline colloidal array (PCCA) thin film composed of a close-packed colloidal array of polystyrene particles. The PCCA thin film was modified with β-cyclodextrin (β-CD) polymer as a capping cavity for the selective detection of paraoxon-ethyl and parathion-ethyl chemical agents. The fabrication of the modified PCCA thin film was optimized and the structure was characterized using scanning electron microscopy (SEM). The arrangement of polystyrene particles in the PCCA follows a pattern of the fcc (111) planes with strong diffraction peak in the visible spectral region and pH dependence. The diffraction peak of the β-CD modified PCCA thin film showed a red shift according to the change of paraoxon-ethyl and parathion-ethyl concentrations at a fast response time (10 s) and high sensitivity with detection limits of 2.0 and 3.4 ppb, respectively. Furthermore, the proposed interaction mechanism of β-CD with paraoxon-ethyl and parathion-ethyl in the β-CD modified PCCA thin film were discussed.

Influence of a novel co-doping (Zn + F) on the physical properties of nano structured (1 1 1) oriented CdO thin films applicable for window layer of solar cell

NASA Astrophysics Data System (ADS)

Anitha, M.; Saravanakumar, K.; Anitha, N.; Amalraj, L.

2018-06-01

Un-doped and co-doped (Zn + F) cadmium oxide (CdO) thin films were prepared by modified spray pyrolysis technique using a nebulizer on glass substrates kept at 200 °C. They were characterized by X-ray diffraction (XRD), X-ray photoelectron spectra (XPS), scanning electron microscopy (SEM), UV-vis spectroscopy, Hall Effect and photoluminescence (PL) respectively. The thin films were having thickness in the range of 520-560 nm. They were well crystalline and displayed high transparency of about >70% in the visible region. It was clearly seen from the SEM photographs that co-doping causes notable changes in the surface morphology. Electrical study exhibited the resistivity of co-doped CdO thin films drastically fell to 1.43 × 10-4 Ω-cm compared with the un-doped CdO thin film. The obtained PL spectra were well corroborated with the structural and optical studies. The high transparency, wide band gap energy and enhanced electrical properties obtained infer that Zn + F co-doped CdO thin films find application in optoelectronic devices, especially in window layer of solar cells.

Carbon abundances, major element chemistry, and mineralogy of hydrated interplanetary dust particles

NASA Technical Reports Server (NTRS)

Keller, L. P.; Thomas, K. L.; Mckay, D. S.

1993-01-01

Hydrated interplanetary dust particles (IDP's) comprise a major fraction of the interplanetary dust particles collected in the stratosphere. While much is known about the mineralogy and chemistry of hydrated IDP's, little is known about the C abundance in this class of IDP's, the nature of the C-bearing phases, and how the C abundance is related to other physical properties of hydrated IDP's. Bulk compositional data (including C and O) for 11 hydrated IDP's that were subsequently examined by the transition electron microscopy (TEM) to determine their mineralogy and mineral chemistry are reported. Our analysis indicates that these hydrated IDP's are strongly enriched in C relative to the most C-rich meteorites. The average abundance of C in these hydrated IDP's is 4X CI chondrite values. The bulk compositions (including C and O) of 11 hydrated IDP's were determined by thin-window, energy-dispersive x ray (EDX) spectroscopy of the uncoated IDP's on Be substrates in the scanning electron microscopy (SEM). As a check on our C measurements, one of the IDP's (L2006H5) was embedded in glassy S, and microtome thin sections were prepared and placed onto Be substrates. Thin-film EDX analyses of multiple thin sections of L2006H5 show good agreement with the bulk value determined in the SEM. Following EDX analysis, the mineralogy and mineral chemistry of each IDP was determined by analyzing ultramicrotome thin sections in a TEM equipped with an EDX spectrometer.

Controlling Surface Morphology and Circumventing Secondary Phase Formation in Non-polar m-GaN by Tuning Nitrogen Activity

NASA Astrophysics Data System (ADS)

Chang, C. W.; Wadekar, P. V.; Guo, S. S.; Cheng, Y. J.; Chou, M.; Huang, H. C.; Hsieh, W. C.; Lai, W. C.; Chen, Q. Y.; Tu, L. W.

2018-01-01

For the development of non-polar nitrides based optoelectronic devices, high-quality films with smooth surfaces, free of defects or clusters, are critical. In this work, the mechanisms governing the topography and single phase epitaxy of non-polar m-plane gallium nitride ( m-GaN) thin films are studied. The samples were grown using plasma-assisted molecular beam epitaxy on m-plane sapphire substrates. Growth of pure m-GaN thin films, concomitant with smooth surfaces is possible at low radio frequency powers and high growth temperatures as judged by the high resolution x-ray diffraction, field emission scanning electron microscopy, and atomic force microscopy measurements. Defect types and densities are quantified using transmission electron microscopy, while Raman spectroscopy was used to analyze the in-plane stress in the thin films which matches the lattice mismatch analysis. Energy dispersive spectroscopy and cathodoluminescence support a congruent growth and a dominant near band edge emission. From the analysis, a narrow growth window is discovered wherein epitaxial growth of pure m-plane GaN samples free of secondary phases with narrow rocking curves and considerable smooth surfaces are successfully demonstrated.

Growth, stability and decomposition of Mg2Si ultra-thin films on Si (100)

NASA Astrophysics Data System (ADS)

Sarpi, B.; Zirmi, R.; Putero, M.; Bouslama, M.; Hemeryck, A.; Vizzini, S.

2018-01-01

Using Auger Electron Spectroscopy (AES), Scanning Tunneling Microscopy/Spectroscopy (STM/STS) and Low Energy Electron Diffraction (LEED), we report an in-situ study of amorphous magnesium silicide (Mg2Si) ultra-thin films grown by thermally enhanced solid-phase reaction of few Mg monolayers deposited at room temperature (RT) on a Si(100) surface. Silicidation of magnesium films can be achieved in the nanometric thickness range with high chemical purity and a high thermal stability after annealing at 150 °C, before reaching a regime of magnesium desorption for temperatures higher than 350 °C. The thermally enhanced reaction of one Mg monolayer (ML) results in the appearance of Mg2Si nanometric crystallites leaving the silicon surface partially uncovered. For thicker Mg deposition nevertheless, continuous 2D silicide films are formed with a volcano shape surface topography characteristic up to 4 Mg MLs. Due to high reactivity between magnesium and oxygen species, the thermal oxidation process in which a thin Mg2Si film is fully decomposed (0.75 eV band gap) into a magnesium oxide layer (6-8 eV band gap) is also reported.

The study of structural properties of carbon nanotubes decorated with NiFe₂O₄ nanoparticles and application of nano-composite thin film as H₂S gas sensor.

PubMed

Hajihashemi, R; Rashidi, Ali M; Alaie, M; Mohammadzadeh, R; Izadi, N

2014-11-01

Nano-composite of multiwall carbon nanotube, decorated with NiFe2O4 nanoparticles (NiFe2O4-MWCNT), was synthesized using the sol-gel method. NiFe2O4-MWCNTs were characterized using different methods such as X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), high resolution transmission electron microscopy (HRTEM), atomic force microscopy (AFM) and vibrating sample magnetometer (VSM). The average size of the crystallites is 23.93 nm. The values of the saturation magnetization (MS), coercivity (HC) and retentivity (MR) of NiFe2O4-MWCNTs are obtained as 15 emu g(-1), 21Oe and 5 emu g(-1), respectively. In this research, NiFe2O4-MWCNT thin films were prepared with the spin-coating method. These thin films were used as the H2S gas sensor. The results suggest the possibility of the utilization of NiFe2O4-MWCNT nano-composite, as the H2S detector. The sensor shows appropriate response towards 100 ppm of H2S at 300°C. Copyright © 2014 Elsevier B.V. All rights reserved.

Microbial colonization of biopolymeric thin films containing natural compounds and antibiotics fabricated by MAPLE

NASA Astrophysics Data System (ADS)

Cristescu, R.; Surdu, A. V.; Grumezescu, A. M.; Oprea, A. E.; Trusca, R.; Vasile, O.; Dorcioman, G.; Visan, A.; Socol, G.; Mihailescu, I. N.; Mihaiescu, D.; Enculescu, M.; Chifiriuc, M. C.; Boehm, R. D.; Narayan, R. J.; Chrisey, D. B.

2015-05-01

Although a great number of antibiotics are currently available, they are often rendered ineffective by the ability of microbial strains to develop genetic resistance and to grow in biofilms. Since many antimicrobial agents poorly penetrate biofilms, biofilm-associated infections often require high concentrations of antimicrobial agents for effective treatment. Among the various strategies that may be used to inhibit microbial biofilms, one strategy that has generated significant interest involves the use of bioactive surfaces that are resistant to microbial colonization. In this respect, we used matrix assisted pulsed laser evaporation (MAPLE) involving a pulsed KrF* excimer laser source (λ = 248 nm, τ = 25 ns, ν = 10 Hz) to obtain thin composite biopolymeric films containing natural (flavonoid) or synthetic (antibiotic) compounds as bioactive substances. Chemical composition and film structures were investigated by Fourier transform infrared spectroscopy and X-ray diffraction. Films morphology was studied by scanning electron microscopy and transmission electron microscopy. The antimicrobial assay of the microbial biofilms formed on these films was assessed by the viable cell counts method. The flavonoid-containing thin films showed increased resistance to microbial colonization, highlighting their potential to be used for the design of anti-biofilm surfaces.

Optical coherence tomography study of retinal changes in normal aging and after ischemia.

PubMed

Shariati, Mohammad Ali; Park, Joyce Ho; Liao, Yaping Joyce

2015-05-01

Age-related thinning of the retinal ganglion cell axons in the nerve fiber layer has been measured in humans using optical coherence tomography (OCT). In this study, we used OCT to measure inner retinal changes in 3-month-, 1-year-, and 2-year-old mice and after experimental anterior ischemic optic neuropathy (AION). We used OCT to quantify retinal thickness in over 200 eyes at different ages before and after a photochemical thrombosis model of AION. The scans were manually or automatically segmented. In normal aging, there was 1.3-μm thinning of the ganglion cell complex (GCC) between 3 months and 1 year (P < 0.0001) and no further thinning at 2 years. In studying age-related inner retinal changes, measurement of the GCC (circular scan) was superior to that of the total retinal thickness (posterior pole scan) despite the need for manual segmentation because it was not contaminated by outer retinal changes. Three weeks after AION, there was 8.9-μm thinning of the GCC (circular scan; P < 0.0001), 50-μm thinning of the optic disc (posterior pole scan; P < 0.0001), and 17-μm thinning of the retina (posterior pole scan; P < 0.0001) in the 3-month-old group. Changes in the older eyes after AION were similar to those of the 3-month-old group. Optical coherence tomography imaging of a large number of eyes showed that, like humans, mice exhibited small, age-related inner retinal thinning. Measurement of the GCC was superior to total retinal thickness in quantifying age-related changes, and both circular and posterior pole scans were useful to track short-term changes after AION.

Formation of thin film like assembly of exfoliated C3N4 nanoflakes by solvent non-evaporative method using centrifuge

NASA Astrophysics Data System (ADS)

Tejasvi, Ravi; Basu, Suddhasatwa

2017-12-01

A simple method for depositing a thin film of nanomaterial on a substrate using centrifugation technique has been developed, whereby solvent evaporation is prevented and solvent reuse is possible. The centrifuge technique of deposition yields uniform, smooth thin film irrespective of substrate surface texture. The deposited TiO2/eC3N4 film studied, through field emission scanning electron microscope, atomic force microscope, and optical surface profilometer, shows variation in surface roughness on the basis of centrifugation speeds. Initially film coverage improves and surface roughness decreases with the increase in rpm of the centrifuge and the surface roughness slightly increases with further increase in rpm. The photoelectrochemical studies of TiO2/eC3N4 films suggest that the centrifuge technique forms better heterojunctions compared to that by spin coating technique leading to enhanced photoelectrochemical water splitting.

Stimulated Emission and Optical Properties of Solid Solutions of Cu(In,Ga)Se2 Direct Band Gap Semiconductors

NASA Astrophysics Data System (ADS)

Svitsiankou, I. E.; Pavlovskii, V. N.; Lutsenko, E. V.; Yablonskii, G. P.; Mudryi, A. V.; Borodavchenko, O. M.; Zhivulko, V. D.; Yakushev, M. V.; Martin, R.

2018-05-01

Stimulated emission, optical properties, and structural characteristics of non-irradiated and proton-irradiated Cu(In,Ga)Se2 thin films deposited on soda lime glass substrates using co-evaporation of elements in a multistage process were investigated. X-ray diffraction analysis, scanning electron microscopy, X-ray spectral analysis with energy dispersion, low-temperature photoluminescence, optical transmittance and reflectance were used to study the films. Stimulated emission at low temperatures of 20 K was found in non-irradiated and proton-irradiated Cu(In,Ga)Se2 thin films upon excitation by laser pulses of nanosecond duration with a threshold power density of 20 kW/cm2. It was shown that the appearance and parameters of the stimulated emission depend strongly on the concentration of ion-induced defects in Cu(In,Ga)Se2 thin films.

Synthesis and characterization thin films of conductive polymer (PANI) for optoelectronic device application

NASA Astrophysics Data System (ADS)

Jarad, Amer N.; Ibrahim, Kamarulazizi; Ahmed, Nasser M.

2016-07-01

In this work we report preparation and investigation of structural and optical properties of polyaniline conducting polymer. By using sol-gel in spin coating technique to synthesize thin films of conducting polymer polyaniline (PANI). Conducting polymer polyaniline was synthesized by the chemical oxidative polymerization of aniline monomers. The thin films were characterized by technique: Hall effect, High Resolution X-ray diffraction (HR-XRD), Fourier transform infrared (FTIR) spectroscopy, Field emission scanning electron microscopy (FE-SEM), and UV-vis spectroscopy. Polyaniline conductive polymer exhibit amorphous nature as confirmed by HR-XRD. The presence of characteristic bonds of polyaniline was observed from FTIR spectroscopy technique. Electrical and optical properties revealed that (p-type) conductivity PANI with room temperature, the conductivity was 6.289×10-5 (Ω.cm)-1, with tow of absorption peak at 426,805 nm has been attributed due to quantized size of polyaniline conducting polymer.

Fabrication and characterization of functionalized surfaces with 3-amino propyltrimethoxysilane films for anti-infective therapy applications

NASA Astrophysics Data System (ADS)

Grumezescu, Valentina; Andronescu, Ecaterina; Holban, Alina Maria; Socol, Gabriel; Grumezescu, Alexandru Mihai; Ficai, Anton; Lazar, Veronica; Chifiriuc, Mariana Carmen; Trusca, Roxana; Iordache, Florin

2015-05-01

The purpose of this study was the fabrication of functionalized anti-adherent surfaces based on the polyvinyl chloride (PVC) coated with 3-amino propyltrimethoxysilane (APTMS) by matrix assisted pulsed laser evaporation (MAPLE) in order to improve the resistance of PVC based prosthetic devices to microbial colonization. Infrared microscopy (IRM) investigations of APTMS thin films proved the compositional homogeneity of the prepared thin film. Scanning electron microscopy (SEM) micrographs revealed a granular morphology with microspheres harboring a diameter between 15 and 60 nm. The microbiological assays proved that MAPLE deposited APTMS films inhibited the adherence capacity and biofilm development of Pseudomonas aeruginosa and Staphylococcus aureus strains. Furthermore, this material proved to be highly biocompatible, allowing the normal growth and development of human endothelial cells. These traits highlight the fact that the fabricated APTMS thin films may be efficiently used for improving different surfaces of medical use, including prostheses and implantable devices.

Fabrication of luminescent SrWO{sub 4} thin films by a novel electrochemical method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen Lianping; Gao Yuanhong

2007-10-02

Highly crystallized SrWO{sub 4} thin films with single scheelite structure were prepared within 60 min by a cell electrochemical method. X-ray diffraction analysis shows that SrWO{sub 4} thin films have a tetragonal structure. Scanning electron microscopy examinations reveal that SrWO{sub 4} grains grow well in tetragonal tapers and grains like flowers or bunches, which can usually form by using the electrolysis electrochemical method, have disappeared under cell electrochemical conditions. X-ray photoelectron spectra and energy dispersive X-ray microanalysis examinations demonstrate that the composition of the film is consistent with its stoichiometry. These SrWO{sub 4} films show a single blue emission peakmore » (located at 460 nm) using an excitation wave of 230 nm. The speed of cell electrochemical method can be controlled by changing temperature. The optimum treatment temperature is about 50-60 deg. C.« less

Self Exchange Bias and Bi-stable Magneto-Resistance States in Amorphous TbFeCo and TbSmFeCo Thin Films

NASA Astrophysics Data System (ADS)

Ma, Chung; Li, Xiaopu; Lu, Jiwei; Poon, Joseph; Comes, Ryan; Devaraj, Arun; Spurgeon, Steven

Amorphous ferrimagetic TbFeCo and TbSmFeCo thin films are found to exhibit strong perpendicular magnetic anisotropy. Self exchange bias effect and bi-stable magneto-resistance states are observed near compensation temperature by magnetic hysteresis loop, anomalous Hall effect and transverse magneto-resistance measurements. Atom probe tomography, scanning transmission electron microscopy, and energy dispersive spectroscopy mapping have revealed two nanoscale amorphous phases with different Tb concentration distributed within the amorphous films. The observed exchange anisotropy originates from the exchange interaction between the two nanoscale amorphous phases. Exchange bias effect is used for increasing stability in spin valves and magnetic tunneling junctions. This study opens up a new platform for using amorphous ferrimagnetic thin films that require no epitaxial growth in nanodevices.. The work was supported by the Defense Threat Reduction Agency Grant and the U.S. Department of Energy.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Di, Jun; Chen, Chao; Yang, Shi -Ze

Photocatalytic solar energy conversion is a clean technology for producing renewable energy sources, but its efficiency is greatly hindered by the kinetically sluggish oxygen evolution reaction. Herein, confined defects in atomically-thin BiOCl nanosheets were created to serve as a remarkable platform to explore the relationship between defects and photocatalytic activity. Surface defects can be clearly observed on atomically-thin BiOCl nanosheets from scanning transmission electron microscopy images. Theoretical/experimental results suggest that defect engineering increased states of density and narrowed the band gap. With combined effects from defect induced shortened hole migratory paths and creation of coordination-unsaturated active atoms with dangling bonds,more » defect-rich BiOCl nanosheets displayed 3 and 8 times higher photocatalytic activity towards oxygen evolution compared with atomically-thin BiOCl nanosheets and bulk BiOCl, respectively. As a result, this successful application of defect engineering will pave a new pathway for improving photocatalytic oxygen evolution activity of other materials.« less

The Effect of Sodium Dodecyl Sulfate on PEDOT:PSS and Its Application to Organic Photovoltaic Solar Cells.

PubMed

Hwang, Ki-Hwan; Seo, Hyeon Jin; Nam, Sang-Hun; Boo, Jin-Hyo

2015-10-01

Recently, the use of PSS in flexible device electrodes has been reported. PSS treatment consists of a step in which a small amount of surfactant is added to enhance the adhesion between PSS and the substrate or TCO materials. However, basic research into the effect of the surfactant is lacking. We studied the effects of sodium dodecyl sulfate (SDS) at controlled concentrations in aqueous PSS solution and that it enhanced the conductivity in the mixed thin films with surfactant and PSS. The thin films were prepared by the spin coating method. To study the structural effects on the resulting electrical properties, the thin films were investigated by FE-SEM (Field Emission Scanning Electron Microscopy) and AFM (Atomic Force Microscopy). At the same time, the electrical properties were investigated using a 4-point probe and solar simulator.

Cathodic cage plasma deposition of TiN and TiO{sub 2} thin films on silicon substrates

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sousa, Romulo R. M. de; Sato, Patricia S.; Nascente, Pedro A. P., E-mail: nascente@ufscar.br

2015-07-15

Cathodic cage plasma deposition (CCPD) was used for growing titanium nitride (TiN) and titanium dioxide (TiO{sub 2}) thin films on silicon substrates. The main advantages of the CCPD technique are the uniformity, tridimensionality, and high rate of the film deposition that occurs at higher pressures, lower temperatures, and lower treatment times than those used in conventional nitriding treatments. In this work, the influence of the temperature and gas atmosphere upon the characteristics of the deposited films was investigated. The TiN and TiO{sub 2} thin films were characterized by x-ray diffraction, scanning electron microscopy, and Raman spectroscopy to analyze their chemical,more » structural, and morphological characteristics, and the combination of these results indicates that the low-cost CCPD technique can be used to produce even and highly crystalline TiN and TiO{sub 2} films.« less

Structural and Optoelectronic Properties of SnO2 Thin Films Doped by Group-Ia Elements

NASA Astrophysics Data System (ADS)

Benhebal, Hadj; Benrabah, Bedhiaf; Ammari, Aek; Madoune, Yacine; Lambert, Stéphanie D.

This paper presents the results of an experimental work devoted to the synthesis and the characterization of tin dioxide (SnO2) thin layers doped with group-IA elements (Li, Na and K). The materials were synthesized by the sol-gel method and deposited by dip-coating, using tin (II) chloride dihydrate as a source of tin and absolute ethyl alcohol as solvent. Thin films prepared were characterized by several techniques including X-ray diffraction (XRD), scanning electron microscopy (SEM), infrared spectroscopy (IR), visible and ultraviolet spectroscopy and complex impedance method. The results obtained show that the materials kept their tetragonal rutile structure with preferred orientation of (101), whereas doping leads to a reduction of their energy band gap. The complex impedance analysis suggests that the different processes occurring at the electrode interface are modeled by an electrical circuit not affected by the doping.

Growth of different phases and morphological features of MnS thin films by chemical bath deposition: Effect of deposition parameters and annealing

NASA Astrophysics Data System (ADS)

Hannachi, Amira; Maghraoui-Meherzi, Hager

2017-03-01

Manganese sulfide thin films have been deposited on glass slides by chemical bath deposition (CBD) method. The effects of preparative parameters such as deposition time, bath temperature, concentration of precursors, multi-layer deposition, different source of manganese, different complexing agent and thermal annealing on structural and morphological film properties have been investigated. The prepared thin films have been characterized using the X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX). It exhibit the metastable forms of MnS, the hexagonal γ-MnS wurtzite phase with preferential orientation in the (002) plane or the cubic β-MnS zinc blende with preferential orientation in the (200) plane. Microstructural studies revealed the formation of MnS crystals with different morphologies, such as hexagons, spheres, cubes or flowers like.

Substrate effects on photoluminescence and low temperature phase transition of methylammonium lead iodide hybrid perovskite thin films

NASA Astrophysics Data System (ADS)

Shojaee, S. A.; Harriman, T. A.; Han, G. S.; Lee, J.-K.; Lucca, D. A.

2017-07-01

We examine the effects of substrates on the low temperature photoluminescence (PL) spectra and phase transition in methylammonium lead iodide hybrid perovskite (CH3NH3PbI3) thin films. Structural characterization at room temperature with X-ray diffraction (XRD), scanning electron microscopy (SEM), and Raman spectroscopy indicated that while the chemical structure of films deposited on glass and quartz was similar, the glass substrate induced strain in the perovskite films and suppressed the grain growth. The luminescence response and phase transition of the perovskite thin films were studied by PL spectroscopy. The induced strain was found to affect both the room temperature and low temperature PL spectra of the hybrid perovskite films. In addition, it was found that the effects of the glass substrate inhibited a tetragonal to orthorhombic phase transition such that it occurred at lower temperatures.

High-resolution structural characterization and magnetic properties of epitaxial Ce-doped yttrium iron garnet thin films

NASA Astrophysics Data System (ADS)

Li, Zhong; Vikram Singh, Amit; Rastogi, Ankur; Gazquez, Jaume; Borisevich, Albina Y.; Mishra, Rohan; Gupta, Arunava

2017-07-01

Thin films of magnetic garnet materials, e.g. yttrium iron garnet (Y3Fe5O12, YIG), are useful for a variety of applications including microwave integrated circuits and spintronics. Substitution of rare earth ions, such as cerium, is known to enhance the magneto-optic Kerr effect (MOKE) as compared to pure YIG. Thin films of Ce0.75Y2.25Fe5O12 (Ce:YIG) have been grown using the pulsed laser deposition (PLD) technique and their crystal structure examined using high resolution scanning transmission electron microscopy. Homogeneous substitution of Ce in YIG, without oxidation to form a separate CeO2 phase, can be realized in a narrow process window with resulting enhancement of the MOKE signal. The thermally generated signal due to spin Seebeck effect for the optimally doped Ce:YIG films has also been investigated.

Effect of copper doping sol-gel ZnO thin films: physical properties and sensitivity to ethanol vapor

NASA Astrophysics Data System (ADS)

Boukaous, Chahra; Benhaoua, Boubaker; Telia, Azzedine; Ghanem, Salah

2017-10-01

In the present paper, the effect of copper doping ZnO thin films, deposited using a sol-gel dip-coating technique, on the structural, optical and ethanol vapor-sensing properties, was investigated. The range of the doping content is 0 wt. %-5 wt. % Cu/Zn and the films’ properties were studied using x-ray diffraction, scanning electron microscopy and a UV-vis spectrophotometer. The obtained results indicated that undoped and copper-doped zinc oxide thin films have polycrystalline wurtzite structure with (1 0 1) preferred orientation. All samples have a smooth and dense structure free of pinholes. A decrease in the band gap with Cu concentration in the ZnO network was observed. The influence of the dopant on ethanol vapor-sensing properties shows an increase in the film sensitivity to the ethanol vapor within the Cu concentration.

Brilliant iridescence of Morpho butterfly wing scales is due to both a thin film lower lamina and a multilayered upper lamina.

PubMed

Giraldo, M A; Stavenga, D G

2016-05-01

Butterflies belonging to the nymphalid subfamily, Morphinae, are famous for their brilliant blue wing coloration and iridescence. These striking optical phenomena are commonly explained as to originate from multilayer reflections by the ridges of the wing scales. Because the lower lamina of the scales of related nymphalid butterflies, the Nymphalinae, plays a dominant role in the wing coloration, by acting as a thin film reflector, we investigated single blue scales of three characteristic Morpho species: M. epistrophus, M. helenor and M. cypris. The experimental data obtained by spectrophotometry, scatterometry and scanning electron microscopy demonstrated that also in the Morpho genus the lower lamina of both the cover and ground scales acts as an optical thin film reflector, contributing importantly to the blue structural coloration of the wings. Melanin pigment has a contrast-enhancing function in a sub-class of ground scales.

Laser-induced dewetting of silver-doped chalcogenide glasses

NASA Astrophysics Data System (ADS)

Douaud, Alexandre; Messaddeq, Sandra Helena; Boily, Olivier; Messaddeq, Younès

2018-07-01

We report the observation of laser-induced dewetting responsible for the formation of periodic relief structures in silver-based chalcogenide thin-films. By varying the concentration of silver in the Agx(As20S80)100-x system (with x = 0, 4, 9 and 36), different surface relief structures are formed. The evolution of the surface changes as a function of laser parameters (power density, duration of exposure, and polarisation) as well as film thickness and silver concentration has been investigated. The scanning electron microscopy and atomic force microscopy images of irradiated spots show periodic ripples aligned perpendicularly to the electric field of incident light. Our results show that addition of silver into sulphur-rich chalcogenide thin-films improves the dewetting when compared to pure As20S80 thin-films. The changes in surface morphology were attributable to photo-induced chemical modifications and a laser-driven molecular rearrangement.

Excitation of propagating surface plasmons with a scanning tunnelling microscope.

PubMed

Wang, T; Boer-Duchemin, E; Zhang, Y; Comtet, G; Dujardin, G

2011-04-29

Inelastic electron tunnelling excitation of propagating surface plasmon polaritons (SPPs) on a thin gold film is demonstrated. This is done by combining a scanning tunnelling microscope (STM) with an inverted optical microscope. Analysis of the leakage radiation in both the image and Fourier planes unambiguously shows that the majority (up to 99.5%) of the detected photons originate from propagating SPPs with propagation lengths of the order of 10  µm. The remaining photon emission is localized under the STM tip and is attributed to a tip-gold film coupled plasmon resonance as evidenced by the bimodal spectral distribution and enhanced emission intensity observed using a silver STM tip for excitation.

Real-Space Analysis of Scanning Tunneling Microscopy Topography Datasets Using Sparse Modeling Approach

NASA Astrophysics Data System (ADS)

Miyama, Masamichi J.; Hukushima, Koji

2018-04-01

A sparse modeling approach is proposed for analyzing scanning tunneling microscopy topography data, which contain numerous peaks originating from the electron density of surface atoms and/or impurities. The method, based on the relevance vector machine with L1 regularization and k-means clustering, enables separation of the peaks and peak center positioning with accuracy beyond the resolution of the measurement grid. The validity and efficiency of the proposed method are demonstrated using synthetic data in comparison with the conventional least-squares method. An application of the proposed method to experimental data of a metallic oxide thin-film clearly indicates the existence of defects and corresponding local lattice distortions.

Reconstruction of the 3-D Shape and Crystal Preferred Orientation of Olivine: A Combined X-ray µ-CT and EBSD-SEM approach

NASA Astrophysics Data System (ADS)

Kahl, Wolf-Achim; Hidas, Károly; Dilissen, Nicole; Garrido, Carlos J.; López-Sánchez Vizcaíno, Vicente; Jesús Román-Alpiste, Manuel

2017-04-01

The complete reconstruction of the microstructure of rocks requires, among others, a full description of the shape preferred orientation (SPO) and crystal preferred orientation (CPO) of the constituent mineral phases. New advances in instrumental analyses, particularly electron backscatter diffraction (EBSD) coupled to focused ion beam-scanning electron microscope (FIB-SEM), allows a complete characterization of SPO and CPO in rocks at the micron scale [1-2]. Unfortunately, the large grain size of many crystalline rocks, such as peridotite, prevents a representative characterization of the CPO and SPO of their constituent minerals by this technique. Here, we present a new approach combining X-ray micro computed tomography (µ-CT) and EBSD to reconstruct the geographically oriented, 3-D SPO and CPO of cm- to mm-sized olivine crystals in two contrasting fabric types of chlorite harzburgites (Almírez ultramafic massif, SE Spain). The semi-destructive sample treatment involves drilling of geographically oriented micro drills in the field and preparation of oriented thin sections from µ-CT scanned cores. This allows for establishing the link among geological structures, macrostructure, fabric, and 3-D SPO-CPO at the thin section scale. Based on EBSD analyses, different CPO groups of olivine crystals can be discriminated in the thin sections and allocated to 3-D SPO in the µ-CT volume data. This approach overcomes the limitations of both methods (i.e., no crystal orientation data in µ-CT and no spatial information in EBSD), hence 3-D orientation of the crystallographic axes of olivines from different orientation groups could be correlated with the crystal shapes of olivine grains. This combined µ-CT and EBSD technique enables the correlation of both SPO and CPO and representative grain size, and is capable to characterize the 3-D microstructure of olivine-bearing rocks at the hand specimen scale. REFERENCES 1. Zaefferer, S., Wright, S.I., Raabe, D., 2008. Three-Dimensional orientation microscopy in a focused ion beam-scanning electron microscope: A new dimension of microstructure characterization. Metallurgical and Materials Transactions A 39, 374-389. 2. Burnett, T.L., Kelley, R., Winiarski, B., Contreras, L., Daly, M., Gholinia, A., Burke, M.G., Withers, P.J., 2016. Large volume serial section tomography by Xe Plasma FIB dual beam microscopy. Ultramicroscopy 161, 119-129.

Structure and growth of the mesoscopic surfactant/silica thin films

NASA Astrophysics Data System (ADS)

Zhou, Linbo

1999-10-01

We report the study of the structure and the growth of the mesoscopic surfactant/silica thin films. We use X-ray diffraction coupled with Scanning Electron Microscope (SEM), Atomic Force Microscope (AFM), Transmission Electron Microscope (TEM) and light scattering techniques to study the structure, lattice strain and the drying effect of the thin films as well as the growth kinetics and mechanism. The surfactant/silica materials are synthesized using the supramolecular assemblies of the surfactant molecules to template the condensation of the inorganic species. The subsequent calcination yields the mesoporous silica materials, which have many application properties such as unusual electronic, optical, magnetic and elastic characteristics. The films are grown on mica, graphite and silicon substrates in an acidic CTAC (Cetyltrimethyl Ammonium Chloride)/TEOS (Tetraethyl Orthosilicate) solution and are found to consist of the hexagonally packed tubules. The substrate plays an important role in the epitaxial arrangement of the film. We use the light scattering and cryo TEM to study the micelle morphology and aggregation in the solution and use synchrotron radiation X-ray diffraction to study the growth of the film at the solid/liquid interfaces in-situ. An induction time is found followed by the growth of the film at a nonlinear growth rate. The induction time depends on the ratio of the concentrations of CTAC to TEOS in the high CTAC concentration regime. The growth kinetics and mechanism are elucidated in a context of a growth model. For the technological application, Micromolding in Capillaries (MIMIC) technique and the field guided growth are used to process the patterned mesoscopic surfactant/silica thin films and align the nanotubules into the desired orientation. X-ray diffraction characterization has been performed to study the structure and orientation of the thin films. The combined influence of the electric field and the confinement of the mold allows the synthesis of the surfactant/silica thin films with the controlled orientation.

Structure, Surface Morphology, and Optical and Electronic Properties of Annealed SnS Thin Films Obtained by CBD

NASA Astrophysics Data System (ADS)

Reghima, Meriem; Akkari, Anis; Guasch, Cathy; Turki-Kamoun, Najoua

2014-09-01

SnS thin films were initially coated onto Pyrex substrates by the chemical bath deposition (CBD) method and annealed at various temperatures ranging from 200°C to 600°C for 30 min in nitrogen gas. X-ray diffraction (XRD) analysis revealed that a structural transition from face-centered cubic to orthorhombic occurs when the annealing temperature is over 500°C. The surface morphology of all thin layers was investigated by means of scanning electron microscopy and atomic force microscopy. The elemental composition of Sn and S, as measured by energy dispersive spectroscopy, is near the stoichiometric ratio. Optical properties studied by means of transmission and reflection measurements show an increase in the absorption coefficient with increasing annealing temperatures. The band gap energy is close to 1.5 eV, which corresponds to the optimum for photovoltaic applications. Last, the thermally stimulated current measurements show that the electrically active traps located in the band gap disappear after annealing at 500°C. These results suggest that, once again, annealing as a post-deposition treatment may be useful for improving the physical properties of the SnS layers included in photovoltaic applications. Moreover, the thermo-stimulated current method may be of practical relevance to explore the electronic properties of more conventional industrial methods, such as sputtering and chemical vapor deposition.

Combining Electronic and Geometric Effects of ZnO-Promoted Pt Nanocatalysts for Aqueous Phase Reforming of 1-Propanol

DOE PAGES

Lei, Yu; Lee, Sungsik; Low, Ke -Bin; ...

2016-04-26

Compared with Pt/Al 2O 3, sintering-resistant Pt nanoparticle catalysts promoted by ZnO significantly improved the reactivity and selectivity toward hydrogen formation in the aqueous phase reforming (APR) of 1-propanol. The improved performance was found to benefit from both the electronic and geometric effects of ZnO thin films. In situ small-angle X-ray scattering and scanning transmission electron microscopy showed that ZnO-promoted Pt possessed promising thermal stability under APR reaction conditions. In situ X-ray absorption spectroscopy showed clear charge transfer between ZnO and Pt nanoparticles. The improved reactivity and selectivity seemed to benefit from having both Pt-ZnO and Pt-Al 2O 3 interfaces.

CdTe Photovoltaics for Sustainable Electricity Generation

NASA Astrophysics Data System (ADS)

Munshi, Amit; Sampath, Walajabad

2016-09-01

Thin film CdTe (cadmium telluride) is an important technology in the development of sustainable and affordable electricity generation. More than 10 GW of installations have been carried out using this technology around the globe. It has been demonstrated as a sustainable, green, renewable, affordable and abundant source of electricity. An advanced sublimation tool has been developed that allows highly controlled deposition of CdTe films onto commercial soda lime glass substrates. All deposition and treatment steps can be performed without breaking the vacuum within a single chamber in an inline process that can be conveniently scaled to a commercial process. In addition, an advanced cosublimation source has been developed to allow the deposition of ternary alloys such as Cd x Mg1- x Te to form an electron reflector layer which is expected to address the voltage deficits in current CdTe devices and to achieve very high efficiency. Extensive materials characterization, including but not limited to scanning electron microscopy, transmission electron microscopy, energy dispersive x-ray spectroscopy, high resolution transmission electron microscopy and electron back-scatter diffraction, has been performed to get a better understanding of the effects of processing conditions on CdTe thin film photovoltaics. This combined with computer modeling such as density function theory modeling gives a new insight into the mechanism of CdTe photovoltaic function. With all these efforts, CdTe photovoltaics has seen great progress in the last few years. Currently, it has been recorded as the cheapest source of electricity in the USA on a commercial scale, and further improvements are predicted to further reduce the cost while increasing its utilization. Here, we give an overview of the advantages of thin film CdTe photovoltaics as well as a brief review of the challenges that need to be addressed. Some fundamental studies of processing conditions for thin film CdTe are also presented along with fabrication conditions using the closed-space sublimation method.

Three-dimensional scanning transmission electron microscopy of biological specimens.

PubMed

de Jonge, Niels; Sougrat, Rachid; Northan, Brian M; Pennycook, Stephen J

2010-02-01

A three-dimensional (3D) reconstruction of the cytoskeleton and a clathrin-coated pit in mammalian cells has been achieved from a focal-series of images recorded in an aberration-corrected scanning transmission electron microscope (STEM). The specimen was a metallic replica of the biological structure comprising Pt nanoparticles 2-3 nm in diameter, with a high stability under electron beam radiation. The 3D dataset was processed by an automated deconvolution procedure. The lateral resolution was 1.1 nm, set by pixel size. Particles differing by only 10 nm in vertical position were identified as separate objects with greater than 20% dip in contrast between them. We refer to this value as the axial resolution of the deconvolution or reconstruction, the ability to recognize two objects, which were unresolved in the original dataset. The resolution of the reconstruction is comparable to that achieved by tilt-series transmission electron microscopy. However, the focal-series method does not require mechanical tilting and is therefore much faster. 3D STEM images were also recorded of the Golgi ribbon in conventional thin sections containing 3T3 cells with a comparable axial resolution in the deconvolved dataset.

Three-Dimensional Scanning Transmission Electron Microscopy of Biological Specimens

PubMed Central

de Jonge, Niels; Sougrat, Rachid; Northan, Brian M.; Pennycook, Stephen J.

2010-01-01

A three-dimensional (3D) reconstruction of the cytoskeleton and a clathrin-coated pit in mammalian cells has been achieved from a focal-series of images recorded in an aberration-corrected scanning transmission electron microscope (STEM). The specimen was a metallic replica of the biological structure comprising Pt nanoparticles 2–3 nm in diameter, with a high stability under electron beam radiation. The 3D dataset was processed by an automated deconvolution procedure. The lateral resolution was 1.1 nm, set by pixel size. Particles differing by only 10 nm in vertical position were identified as separate objects with greater than 20% dip in contrast between them. We refer to this value as the axial resolution of the deconvolution or reconstruction, the ability to recognize two objects, which were unresolved in the original dataset. The resolution of the reconstruction is comparable to that achieved by tilt-series transmission electron microscopy. However, the focal-series method does not require mechanical tilting and is therefore much faster. 3D STEM images were also recorded of the Golgi ribbon in conventional thin sections containing 3T3 cells with a comparable axial resolution in the deconvolved dataset. PMID:20082729

New Developments in Cathodoluminescence Spectroscopy for the Study of Luminescent Materials

PubMed Central

den Engelsen, Daniel; Fern, George R.; Harris, Paul G.; Ireland, Terry G.; Silver, Jack

2017-01-01

Herein, we describe three advanced techniques for cathodoluminescence (CL) spectroscopy that have recently been developed in our laboratories. The first is a new method to accurately determine the CL-efficiency of thin layers of phosphor powders. When a wide band phosphor with a band gap (Eg > 5 eV) is bombarded with electrons, charging of the phosphor particles will occur, which eventually leads to erroneous results in the determination of the luminous efficacy. To overcome this problem of charging, a comparison method has been developed, which enables accurate measurement of the current density of the electron beam. The study of CL from phosphor specimens in a scanning electron microscope (SEM) is the second subject to be treated. A detailed description of a measuring method to determine the overall decay time of single phosphor crystals in a SEM without beam blanking is presented. The third technique is based on the unique combination of microscopy and spectrometry in the transmission electron microscope (TEM) of Brunel University London (UK). This combination enables the recording of CL-spectra of nanometre-sized specimens and determining spatial variations in CL emission across individual particles by superimposing the scanning TEM and CL-images. PMID:28772671

Fabrication of Eu doped CdO [Al/Eu-nCdO/p-Si/Al] photodiodes by perfume atomizer based spray technique for opto-electronic applications

NASA Astrophysics Data System (ADS)

Ravikumar, M.; Ganesh, V.; Shkir, Mohd; Chandramohan, R.; Arun Kumar, K. Deva; Valanarasu, S.; Kathalingam, A.; AlFaify, S.

2018-05-01

In this study, thin films of cadmium oxide (CdO) with different concentrations (0, 1, 3, and 5 wt%) of Eu doping were deposited onto Si and glass substrates by a novel and facile spray technique using simple perfume atomizer for the first time. Prepared films were characterized for structural, morphological, optical properties and the photo diode studies, using X-ray diffraction, scanning electron microscope, UV-Vis spectrophotometer, Isbnd V characteristics, and fundamental parameters are reported. All the prepared Eu:CdO films exhibit cubic structure. The preferential orientation is along (200) plane. Scanning electron microscopy study indicates the growth of smooth and pin-hole free films with clusters of homogeneous grains. The values of band gap energy are found to be varying from 2.42 to 2.33 eV for various Eu doping concentration from 0 to 5 wt%. EDAX studies revealed the presence of Eu, Cd and O elements without any other impurities. FTIR spectra showed a peak at 575 cm-1 confirming the stretching mode of Cdsbnd O. The resistivity (ρ), high carrier concentration (n) and carrier mobility (μ) for 3 wt% CdO thin film are found to be 0.452 × 10-3(Ω.cm), 17.82 × 1020 cm-3 and 7.757 cm2/V, respectively. Current-voltage measurements on the fabricated nanostructured Al/Eu-nCdO/p-Si/Al heterojunction device showed a non-linear electric characteristics indicating diode like behaviour.

Conductivity and local structure in LaNiO3

NASA Astrophysics Data System (ADS)

Fowlie, Jennifer; Gibert, Marta; Tieri, Giulio; Gloter, Alexandre; à+/-Iguez, Jorge; Filippetti, Alessio; Catalano, Sara; Gariglio, Stefano; StéPhan, Odile; Triscone, Jean-Marc

In this study we approach the thickness-dependence of the properties of LaNiO3 films along multiple, complementary avenues: sophisticated ab initio calculations, scanning transmission electron microscopy and electronic transport. Specifically, we find an unexpected maximum in conductivity in films of thickness 6 - 10 unit cells (3 nm) for several series of LaNiO3 films. Ab initio transport based on the detailed crystal structure also reveals a maximum in conductivity at the same thickness. In agreement with the structure obtained from scanning transmission electron microscopy (STEM), our simulated structures reveal that the substrate- and surface-induced distortions lead to three types of local structure (heterointerface, interior-layer, surface). Based on this observation, a 3-element parallel conductor model neatly reproduces the trend of conductivity with thickness. This study addresses the question of how structural distortions at the atomic scale evolve in a thin film under the influence of the substrate and the surface. This topic is key to the understanding of the physics of heterostructures and the design of functional oxides.

Characterizing the Three-Dimensional Structure of Block Copolymers via Sequential Infiltration Synthesis and Scanning Transmission Electron Tomography

DOE Office of Scientific and Technical Information (OSTI.GOV)

Segal-Peretz, Tamar; Winterstein, Jonathan; Doxastakis, Manolis

Understanding and controlling the three-dimensional structure of block copolymer (BCP) thin films is critical for utilizing these materials for sub-20 nm nanopatterning in semiconductor devices, as well as in membranes and solar cell applications. Combining an atomic layer deposition (ALD) based technique for enhancing the contrast of BCPs in transmission electron microscopy (TEM) together with scanning TEM (STEM) tomography reveals and characterizes the three-dimensional structures of poly(styrene-block-methyl methacrylate) (PS-b-PMMA) thin films with great clarity. Sequential infiltration synthesis (SIS), a block-selective technique for growing inorganic materials in BCPs films in ALD, and an emerging tool for enhancing the etch contrast ofmore » BCPs, was harnessed to significantly enhance the high-angle scattering from the polar domains of BCP films in the TEM. The power of combining SIS and STEM tomography for three dimensional (3D) characterization of BCPs films was demonstrated with the following cases: self-assembled cylindrical, lamellar, and spherical PS-PMMA thin films. In all cases, STEM tomography has revealed 3D structures that were hidden underneath the surface, including: 1) the 3D structure of defects in cylindrical and lamellar phases, 2) non-perpendicular 3D surface of grain boundaries in the cylindrical phase, and 3) the 3D arrangement of spheres in body centered cubic (BCC) and hexagonal closed pack (HCP) morphologies in the spherical phase. The 3D data of the spherical morphologies was compared to coarse-grained simulations and assisted in validating the simulations’ parameters. STEM tomography of SIS-treated BCP films enables the characterization of the exact structure used for pattern transfer, and can lead to better understating of the physics which is utilized in BCP lithography.« less

X-ray microscopy as an approach to increasing accuracy and efficiency of serial block-face imaging for correlated light and electron microscopy of biological specimens.

PubMed

Bushong, Eric A; Johnson, Donald D; Kim, Keun-Young; Terada, Masako; Hatori, Megumi; Peltier, Steven T; Panda, Satchidananda; Merkle, Arno; Ellisman, Mark H

2015-02-01

The recently developed three-dimensional electron microscopic (EM) method of serial block-face scanning electron microscopy (SBEM) has rapidly established itself as a powerful imaging approach. Volume EM imaging with this scanning electron microscopy (SEM) method requires intense staining of biological specimens with heavy metals to allow sufficient back-scatter electron signal and also to render specimens sufficiently conductive to control charging artifacts. These more extreme heavy metal staining protocols render specimens light opaque and make it much more difficult to track and identify regions of interest (ROIs) for the SBEM imaging process than for a typical thin section transmission electron microscopy correlative light and electron microscopy study. We present a strategy employing X-ray microscopy (XRM) both for tracking ROIs and for increasing the efficiency of the workflow used for typical projects undertaken with SBEM. XRM was found to reveal an impressive level of detail in tissue heavily stained for SBEM imaging, allowing for the identification of tissue landmarks that can be subsequently used to guide data collection in the SEM. Furthermore, specific labeling of individual cells using diaminobenzidine is detectable in XRM volumes. We demonstrate that tungsten carbide particles or upconverting nanophosphor particles can be used as fiducial markers to further increase the precision and efficiency of SBEM imaging.

X-ray Microscopy as an Approach to Increasing Accuracy and Efficiency of Serial Block-face Imaging for Correlated Light and Electron Microscopy of Biological Specimens

PubMed Central

Bushong, Eric A.; Johnson, Donald D.; Kim, Keun-Young; Terada, Masako; Hatori, Megumi; Peltier, Steven T.; Panda, Satchidananda; Merkle, Arno; Ellisman, Mark H.

2015-01-01

The recently developed three-dimensional electron microscopic (EM) method of serial block-face scanning electron microscopy (SBEM) has rapidly established itself as a powerful imaging approach. Volume EM imaging with this scanning electron microscopy (SEM) method requires intense staining of biological specimens with heavy metals to allow sufficient back-scatter electron signal and also to render specimens sufficiently conductive to control charging artifacts. These more extreme heavy metal staining protocols render specimens light opaque and make it much more difficult to track and identify regions of interest (ROIs) for the SBEM imaging process than for a typical thin section transmission electron microscopy correlative light and electron microscopy study. We present a strategy employing X-ray microscopy (XRM) both for tracking ROIs and for increasing the efficiency of the workflow used for typical projects undertaken with SBEM. XRM was found to reveal an impressive level of detail in tissue heavily stained for SBEM imaging, allowing for the identification of tissue landmarks that can be subsequently used to guide data collection in the SEM. Furthermore, specific labeling of individual cells using diaminobenzidine is detectable in XRM volumes. We demonstrate that tungsten carbide particles or upconverting nanophosphor particles can be used as fiducial markers to further increase the precision and efficiency of SBEM imaging. PMID:25392009

Thermochromic properties of W-doped VO2 thin films deposited by aqueous sol-gel method for adaptive infrared stealth application

NASA Astrophysics Data System (ADS)

Liu, Dongqing; Cheng, Haifeng; Xing, Xin; Zhang, Chaoyang; Zheng, Wenwei

2016-07-01

The W doped VO2 thin films with various W contents were successfully deposited by aqueous sol-gel method followed by a post annealing process. The derived thin films were characterized by X-ray diffraction, Raman spectra, scanning electron microscopy and atomic force microscopy. Besides, the resistance-temperature relationship and infrared emissivity in the waveband 7.5-14 μm were analyzed, and the effects of W doping on the thermochromic properties of VO2 thin films were studied. The results show that W atoms enter the crystal lattice of VO2 and the transition temperature decreases gradually with increasing doping amount of W. The emissivity of VO2-W-4% thin films has dropped to 0.4 when its real temperature is above 30 °C. The thermal infrared images were also examined under different temperature by thermal imager. The results indicate that the temperature under which W doped VO2 thin films begin to have lower emissivity decreases gradually with increasing doping amount of W. W doped VO2 thin films can control its infrared radiation intensity actively at a lower temperature level of 30 °C, which has great application prospects in the adaptive infrared stealth technology.

Mechanical and physicochemical properties study on gellan gum thin film prepared using film casting method

NASA Astrophysics Data System (ADS)

Ismail, Nur Arifah; Razali, Mohd Hasmizam; Amin, Khairul Anuar Mat

2017-09-01

The GG thin films were prepared by film casting technique using gelzan (GG1) and kelcogel (GG2) respectively. The physical appearances of the thin films were observed and their mechanical and chemical properties were investigated. Chemical characterizations were done by Attenuated Total Reflectance-Fourier Transform Infrared Spectroscopy (ATR-FTIR), UV-Vis Spectroscopy, and Scanning Electron Microscopy (SEM). Based on the ATR-FTIR result, GG1 and GG2 thin films show a broad peak in the range of 3600-3200 cm-1 assigned to -OH functional group. A broad peaks also was observed at 3000-2600 cm-1 and 1800-1600 cm-1 which are belong to -CH and C=O functional group, respectively. The UV-Vis Spectroscopy analysis shows that single absorption peak was observed at 260 nm for both films. For mechanical properties, GG1 thin film has high tensile strength (80±12), but low strain at break (2±1), on the other hand GG2 thin film has low tensile strength (3±0.08) but high strain at break (13±0.58). The Water Vapour Transmission Rates (WVTR) and swelling of GG1 and GG2 thin films were (422±113, 415±26) and (987±113, 902±63), respectively.

Evolution of the mechanical and tribological properties of DLC thin films doped with low-concentration hafnium on 316L steel

NASA Astrophysics Data System (ADS)

Qi, Meng; Xiao, Jianrong; Gong, Chenyang; Jiang, Aihua; Chen, Yong

2018-01-01

Low concentrations (<1 at%) of hafnium doped into diamond-like thin films (Hf-DLC) were deposited on 316L stainless steel and silicon (1 0 0) substrates by magnetron sputtering to attain superior mechanical and tribological properties. Ar and CH4 were used as source gases. The microstructure, chemical composition, and morphology of the Hf-DLC thin films in various concentrations were analyzed using x-ray diffraction, Raman spectroscopy, x-ray photoelectron spectroscopy, scanning electron microscopy and atomic force microscopy. Results showed that Hf species transferred from the particulate microstructure to Hf carbide phases, and the surface roughness increased monotonically with increasing Hf concentration. Moreover, the hardness and elastic modulus exhibited high values when the doped Hf concentration was 0.42 at%. Similarly, the tribological behaviors and wear life of Hf-DLC thin films had a low friction coefficient and excellent wear resistance at 0.42 at% Hf concentration. Therefore, 0.42 at% Hf is an optimal doping concentration to improve the mechanical and tribological properties of DLC thin films. Generally, the use of low-concentration Hf doping into DLC thin films is novel, and the present results provide guidance for the selection of suitable and effective concentration to optimize Hf-DLC thin films with superior performance.

Indium droplet formation in InGaN thin films with single and double heterojunctions prepared by MOCVD

PubMed Central

2014-01-01

Indium gallium nitride (InGaN) samples with single heterojunction (SH) and double heterojunction (DH) were prepared using metal-organic chemical vapor deposition. SH has a layer of InGaN thin film (thicknesses, 25, 50, 100, and 200 nm) grown on an uGaN film (thickness, 2 μm). The DH samples are distinguished by DH uGaN film (thickness, 120 nm) grown on the InGaN layer. Reciprocal space mapping measurements reveal that the DH samples are fully strained with different thicknesses, whereas the strain in the SH samples are significantly relaxed with the increasing thickness of the InGaN film. Scanning electron microscopy results show that the surface roughness of the sample increases when the sample is relaxed. High-resolution transmission electron microscopy images of the structure of indium droplets in the DH sample indicate that the thickness of the InGaN layer decreases with the density of indium droplets. The formation of these droplets is attributed to the insufficient kinetic energy of indium atom to react with the elements of group V, resulting to aggregation. The gallium atoms in the GaN thin film will not be uniformly replaced by indium atoms; the InGaN thin film has an uneven distribution of indium atoms and the quality of the epitaxial layer is degraded. PMID:25024692

Plasma-Assisted Atomic Layer Deposition of High-Density Ni Nanoparticles for Amorphous In-Ga-Zn-O Thin Film Transistor Memory

NASA Astrophysics Data System (ADS)

Qian, Shi-Bing; Wang, Yong-Ping; Shao, Yan; Liu, Wen-Jun; Ding, Shi-Jin

2017-02-01

For the first time, the growth of Ni nanoparticles (NPs) was explored by plasma-assisted atomic layer deposition (ALD) technique using NiCp2 and NH3 precursors. Influences of substrate temperature and deposition cycles on ALD Ni NPs were studied by field emission scanning electron microscope and X-ray photoelectron spectroscopy. By optimizing the process parameters, high-density and uniform Ni NPs were achieved in the case of 280 °C substrate temperature and 50 deposition cycles, exhibiting a density of 1.5 × 1012 cm-2 and a small size of 3 4 nm. Further, the above Ni NPs were used as charge storage medium of amorphous indium-gallium-zinc oxide (a-IGZO) thin film transistor (TFT) memory, demonstrating a high storage capacity for electrons. In particular, the nonvolatile memory exhibited an excellent programming characteristic, e.g., a large threshold voltage shift of 8.03 V was obtained after being programmed at 17 V for 5 ms.

Growth process optimization of ZnO thin film using atomic layer deposition

NASA Astrophysics Data System (ADS)

Weng, Binbin; Wang, Jingyu; Larson, Preston; Liu, Yingtao

2016-12-01

The work reports experimental studies of ZnO thin films grown on Si(100) wafers using a customized thermal atomic layer deposition. The impact of growth parameters including H2O/DiethylZinc (DEZn) dose ratio, background pressure, and temperature are investigated. The imaging results of scanning electron microscopy and atomic force microscopy reveal that the dose ratio is critical to the surface morphology. To achieve high uniformity, the H2O dose amount needs to be at least twice that of DEZn per each cycle. If the background pressure drops below 400 mTorr, a large amount of nanoflower-like ZnO grains would emerge and increase surface roughness significantly. In addition, the growth temperature range between 200 °C and 250 °C is found to be the optimal growth window. And the crystal structures and orientations are also strongly correlated to the temperature as proved by electron back-scattering diffraction and x-ray diffraction results.

Atomic scale imaging of competing polar states in a Ruddlesden-Popper layered oxide.

PubMed

Stone, Greg; Ophus, Colin; Birol, Turan; Ciston, Jim; Lee, Che-Hui; Wang, Ke; Fennie, Craig J; Schlom, Darrell G; Alem, Nasim; Gopalan, Venkatraman

2016-08-31

Layered complex oxides offer an unusually rich materials platform for emergent phenomena through many built-in design knobs such as varied topologies, chemical ordering schemes and geometric tuning of the structure. A multitude of polar phases are predicted to compete in Ruddlesden-Popper (RP), An+1BnO3n+1, thin films by tuning layer dimension (n) and strain; however, direct atomic-scale evidence for such competing states is currently absent. Using aberration-corrected scanning transmission electron microscopy with sub-Ångstrom resolution in Srn+1TinO3n+1 thin films, we demonstrate the coexistence of antiferroelectric, ferroelectric and new ordered and low-symmetry phases. We also directly image the atomic rumpling of the rock salt layer, a critical feature in RP structures that is responsible for the competing phases; exceptional quantitative agreement between electron microscopy and density functional theory is demonstrated. The study shows that layered topologies can enable multifunctionality through highly competitive phases exhibiting diverse phenomena in a single structure.

Atomic scale imaging of competing polar states in a Ruddlesden–Popper layered oxide

PubMed Central

Stone, Greg; Ophus, Colin; Birol, Turan; Ciston, Jim; Lee, Che-Hui; Wang, Ke; Fennie, Craig J.; Schlom, Darrell G.; Alem, Nasim; Gopalan, Venkatraman

2016-01-01

Layered complex oxides offer an unusually rich materials platform for emergent phenomena through many built-in design knobs such as varied topologies, chemical ordering schemes and geometric tuning of the structure. A multitude of polar phases are predicted to compete in Ruddlesden–Popper (RP), An+1BnO3n+1, thin films by tuning layer dimension (n) and strain; however, direct atomic-scale evidence for such competing states is currently absent. Using aberration-corrected scanning transmission electron microscopy with sub-Ångstrom resolution in Srn+1TinO3n+1 thin films, we demonstrate the coexistence of antiferroelectric, ferroelectric and new ordered and low-symmetry phases. We also directly image the atomic rumpling of the rock salt layer, a critical feature in RP structures that is responsible for the competing phases; exceptional quantitative agreement between electron microscopy and density functional theory is demonstrated. The study shows that layered topologies can enable multifunctionality through highly competitive phases exhibiting diverse phenomena in a single structure. PMID:27578622

Ambipolar transport of silver nanoparticles decorated graphene oxide field effect transistors

NASA Astrophysics Data System (ADS)

Sarkar, Kalyan Jyoti; Sarkar, K.; Pal, B.; Kumar, Aparabal; Das, Anish; Banerji, P.

2018-05-01

In this article, we report ambipolar field effect transistor (FET) by using graphene oxide (GO) as a gate dielectric material for silver nanoparticles (AgNPs) decorated GO channel layer. GO was synthesized by Hummers' method. The AgNPs were prepared via photochemical reduction of silver nitrate solution by using monoethanolamine as a reducing agent. Morphological properties of channel layer were characterized by Field Effect Scanning Electron Microscopy (FESEM). Fourier Transform Infrared Spectroscopy (FTIR) was carried out to characterize GO thin film. For device fabrication gold (Au) was deposited as source-drain contact and aluminum (Al) was taken as bottom contact. Electrical measurements were performed by back gate configuration. Ambipolar transport behavior was explained from transfer characteristics. A maximum electron mobiliy of 6.65 cm2/Vs and a hole mobility of 2.46 cm2/Vs were extracted from the transfer characteristics. These results suggest that GO is a potential candidate as a gate dielectric material for thin film transistor applications and also provides new insights in GO based research.

An alternative route for the synthesis of silicon nanowires via porous anodic alumina masks

PubMed Central

2011-01-01

Amorphous Si nanowires have been directly synthesized by a thermal processing of Si substrates. This method involves the deposition of an anodic aluminum oxide mask on a crystalline Si (100) substrate. Fe, Au, and Pt thin films with thicknesses of ca. 30 nm deposited on the anodic aluminum oxide-Si substrates have been used as catalysts. During the thermal treatment of the samples, thin films of the metal catalysts are transformed in small nanoparticles incorporated within the pore structure of the anodic aluminum oxide mask, directly in contact with the Si substrate. These homogeneously distributed metal nanoparticles are responsible for the growth of Si nanowires with regular diameter by a simple heating process at 800°C in an Ar-H2 atmosphere and without an additional Si source. The synthesized Si nanowires have been characterized by field emission scanning electron microscopy, high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, and Raman. PMID:21849077

Effects of Na Doping on Structural, Optical, and Electronic Properties of ZnO Thin Films Fabricated by Sol-Gel Technique

NASA Astrophysics Data System (ADS)

Fan, Heliang; Yao, Zhen; Xu, Cheng; Wang, Xinqiang; Yu, Zhichao

2018-04-01

Undoped and Na-doped ZnO thin films were fabricated by sol-gel technique on quartz glass substrates and annealed at 500°C for 1 h. The structural properties of the films were characterized using x-ray diffraction analysis, which revealed hexagonal wurtzite structure with no peaks corresponding to Na2O or other Na phases being found. Surface morphology observations by scanning electron microscopy revealed that the crystallite size and topographical properties of the ZnO films were influenced by the Na doping concentration. X-ray photoelectron spectra revealed presence of Na+ in ZnO regime. The transmittance spectra indicated that the average transmittance of Na-doped ZnO film was above 80% in the visible range, superior to that of the undoped film. There was a blue-shift in the ultraviolet absorption edge with increase of the Na content. Photoluminescence spectra illustrated two peaks, corresponding to ultraviolet near-band-edge and visible emission.

Calcium copper-titanate thin film growth: tailoring of the operational conditions through nanocharacterization and substrate nature effects.

PubMed

Lo Nigro, Raffaella; Toro, Roberta G; Malandrino, Graziella; Fragalà, Ignazio L; Losurdo, Maria; Giangregorio, Michelaria M; Bruno, Giovanni; Raineri, Vito; Fiorenza, Patrick

2006-09-07

A novel approach based on a molten multicomponent precursor source has been applied for the MOCVD fabrication of high-quality CaCu(3)Ti(4)O(12) (CCTO) thin films on various substrates. The adopted in situ strategy involves a molten mixture consisting of Ca(hfa)(2).tetraglyme, Ti(tmhd)(2)(O-iPr)(2), and Cu(tmhd)(2) [Hhfa = 1,1,1,5,5,5-hexafluoro-2,4-pentanedione; tetraglyme = 2,5,8,11,14-pentaoxapentadecane; Htmhd = 2,2,6,6-tetramethyl-3,5-heptandione; O-iPr = isopropoxide] precursors. Film structural and morphological characterizations have been carried out by several techniques [X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM)], and in particular the energy filtered TEM mapping and X-ray energy dispersive (EDX) analysis in TEM mode provided a suitable correlation between nanostructural properties of CCTO films and deposition conditions and/or the substrate nature. Correlation between the nanostructure and optical/dielectric properties has been investigated exploiting spectroscopic ellipsometry.

Atomic scale imaging of competing polar states in a Ruddlesden-Popper layered oxide

NASA Astrophysics Data System (ADS)

Stone, Greg; Ophus, Colin; Birol, Turan; Ciston, Jim; Lee, Che-Hui; Wang, Ke; Fennie, Craig J.; Schlom, Darrell G.; Alem, Nasim; Gopalan, Venkatraman

2016-08-01

Layered complex oxides offer an unusually rich materials platform for emergent phenomena through many built-in design knobs such as varied topologies, chemical ordering schemes and geometric tuning of the structure. A multitude of polar phases are predicted to compete in Ruddlesden-Popper (RP), An+1BnO3n+1, thin films by tuning layer dimension (n) and strain; however, direct atomic-scale evidence for such competing states is currently absent. Using aberration-corrected scanning transmission electron microscopy with sub-Ångstrom resolution in Srn+1TinO3n+1 thin films, we demonstrate the coexistence of antiferroelectric, ferroelectric and new ordered and low-symmetry phases. We also directly image the atomic rumpling of the rock salt layer, a critical feature in RP structures that is responsible for the competing phases; exceptional quantitative agreement between electron microscopy and density functional theory is demonstrated. The study shows that layered topologies can enable multifunctionality through highly competitive phases exhibiting diverse phenomena in a single structure.

THz conductivities of indium-tin-oxide nanowhiskers as a graded-refractive-index structure.

PubMed

Yang, Chan-Shan; Chang, Chia-Hua; Lin, Mao-Hsiang; Yu, Peichen; Wada, Osamu; Pan, Ci-Ling

2012-07-02

Indium-tin-oxide (ITO) nanowhiskers with attractive electrical and anti-reflection properties were prepared by the glancing-angle electron-beam evaporation technique. Structural and crystalline properties of such nanostructures were examined by scanning transmission electron microscopy and X-ray diffraction. Their frequency-dependent complex conductivities, refractive indices and absorption coefficients have been characterized with terahertz time-domain spectroscopy (THz-TDS), in which the nanowhiskers were considered as a graded-refractive-index (GRIN) structure instead of the usual thin film model. The electrical properties of ITO GRIN structures are analyzed and fitted well with Drude-Smith model in the 0.2~2.0 THz band. Our results indicate that the ITO nanowhiskers and its bottom layer atop the substrate exhibit longer carrier scattering times than ITO thin films. This signifies that ITO nanowhiskers have an excellent crystallinity with large grain size, consistent with X-ray data. Besides, we show a strong backscattering effect and fully carrier localization in the ITO nanowhiskers.

Enhanced stress corrosion cracking resistance and electrical conductivity of a T761 treated Al-Zn-Mg-Cu alloy thin plate

NASA Astrophysics Data System (ADS)

Chen, Xu; Zhai, Sudan; Gao, Di; Liu, Ye; Xu, Jing; Liu, Yang

2018-01-01

The stress corrosion cracking (SCC) behavior, electrical conductivity and mechanical properties of an Al-Zn-Mg-Cu alloy pre-stretched thin plate for wing skin were researched in this paper. The microstructures and SCC fracture surfaces of the alloy treated at different conditions were characterized by transmission electron microscopy, optical microscopy and scanning electron microscopy. Results indicated that with the increasing of aging temperature, the electrical conductivity and the elongation increased greatly, while the strength decreased gradually which were closely associated with the type and morphology of the precipitates. Compared with the T6 treated alloy, the SCC resistance of the T761 treated Al-Zn-Mg-Cu alloy was improved greatly. The SCC behavior of the T6 treated alloy was dominated by anodic dissolution theory, whereas the hydrogen induced cracking controlled the fracture behavior of the T761 treated alloy which was influenced by the morphology of grain boundary precipitates in this investigated alloy.

Human cardiac telocytes: 3D imaging by FIB-SEM tomography

PubMed Central

Cretoiu, D; Hummel, E; Zimmermann, H; Gherghiceanu, M; Popescu, L M

2014-01-01

Telocyte (TC) is a newly identified type of cell in the cardiac interstitium (www.telocytes.com). TCs are described by classical transmission electron microscopy as cells with very thin and long telopodes (Tps; cellular prolongations) having podoms (dilations) and podomers (very thin segments). TCs’ three-dimensional (3D) morphology is still unknown. Cardiac TCs seem to be particularly involved in long and short distance intercellular signalling and, therefore, their 3D architecture is important for understanding their spatial connections. Using focused ion beam scanning electron microscopy (FIB-SEM) we show, for the first time, the whole ultrastructural anatomy of cardiac TCs. 3D reconstruction of cardiac TCs by FIB-SEM tomography confirms that they have long, narrow but flattened (ribbon-like) telopodes, with humps generated by the podoms. FIB-SEM tomography also confirms the network made by TCs in the cardiac interstitium through adherens junctions. This study provides the first FIB-SEM tomography of a human cell type. PMID:25327290

Ellipsometric analysis and optical absorption characterization of gallium phosphide nanoparticulate thin film

NASA Astrophysics Data System (ADS)

Zhang, Qi-Xian; Wei, Wen-Sheng; Ruan, Fang-Ping

2011-04-01

Gallium phosphide (GaP) nanoparticulate thin films were easily fabricated by colloidal suspension deposition via GaP nanoparticles dispersed in N,N-dimethylformamide. The microstructure of the film was performed by x-ray diffraction, high resolution transmission electron microscopy and field emission scanning electron microscopy. The film was further investigated by spectroscopic ellipsometry. After the model GaP+void|SiO2 was built and an effective medium approximation was adopted, the values of the refractive index n and the extinction coefficient k were calculated for the energy range of 0.75 eV-4.0 eV using the dispersion formula in DeltaPsi2 software. The absorption coefficient of the film was calculated from its k and its energy gaps were further estimated according to the Tauc equation, which were further verified by its fluorescence spectrum measurement. The structure and optical absorption properties of the nanoparticulate films are promising for their potential applications in hybrid solar cells.

Heavily-doped ZnO:Al thin films prepared by using magnetron Co-sputtering: Optical and electrical properties

NASA Astrophysics Data System (ADS)

Moon, Eun-A.; Jun, Young-Kil; Kim, Nam-Hoon; Lee, Woo-Sun

2016-07-01

Photovoltaic applications require transparent conducting-oxide (TCO) thin films with high optical transmittance in the visible spectral region (380 - 780 nm), low resistivity, and high thermal/chemical stability. The ZnO thin film is one of the most common alternatives to the conventional indium-tin-oxide (ITO) thin film TCO. Highly transparent and conductive ZnO thin films can be prepared by doping with group III elements. Heavily-doped ZnO:Al (AZO) thin films were prepared by using the RF magnetron co-sputtering method with ZnO and Al targets to obtain better characteristics at a low cost. The RF sputtering power to each target was varied to control the doping concentration in fixed-thickness AZO thin films. The crystal structures of the AZO thin films were analyzed by using X-ray diffraction. The morphological microstructure was observed by using scanning electron microscopy. The optical transmittance and the band gap energy of the AZO thin films were examined with an UV-visible spectrophotometer in the range of 300 - 1800 nm. The resistivity and the carrier concentration were examined by using a Hall-effect measurement system. An excellent optical transmittance > 80% with an appropriate band gap energy (3.26 - 3.27 eV) and an improved resistivity (~10 -1 Ω·cm) with high carrier concentration (1017 - 1019 cm -3) were demonstrated in 350-nm-thick AZO thin films for thin-film photovoltaic applications.

Studies of x-ray localization and thickness dependence in atomic-scale elemental mapping by STEM energy-dispersive x-ray spectroscopy using single-frame scanning method

DOE PAGES

Lu, Ping; Moya, Jaime M.; Yuan, Renliang; ...

2018-03-01

The delocalization of x-ray signals limits the spatial resolution in atomic-scale elemental mapping by scanning transmission electron microscopy (STEM) using energy-dispersive x-ray spectroscopy (EDS). In this study, using a SrTiO 3 [001] single crystal, we show that the x-ray localization to atomic columns is strongly dependent on crystal thickness, and a thin crystal is critical for improving the spatial resolution in atomic-scale EDS mapping. A single-frame scanning technique is used in this study instead of the multiple-frame technique to avoid peak broadening due to tracking error. The strong thickness dependence is realized by measuring the full width at half maximamore » (FWHM) as well as the peak-to-valley (P/V) ratio of the EDS profiles for Ti K and Sr K+L, obtained at several crystal thicknesses. A FWHM of about 0.16 nm and a P/V ratio of greater than 7.0 are obtained for Ti K for a crystal thickness of less than 20 nm. In conclusion, with increasing crystal thickness, the FWHM and P/V ratio increases and decreases, respectively, indicating the advantage of using a thin crystal for high-resolution EDS mapping.« less

Studies of x-ray localization and thickness dependence in atomic-scale elemental mapping by STEM energy-dispersive x-ray spectroscopy using single-frame scanning method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lu, Ping; Moya, Jaime M.; Yuan, Renliang

The delocalization of x-ray signals limits the spatial resolution in atomic-scale elemental mapping by scanning transmission electron microscopy (STEM) using energy-dispersive x-ray spectroscopy (EDS). In this study, using a SrTiO 3 [001] single crystal, we show that the x-ray localization to atomic columns is strongly dependent on crystal thickness, and a thin crystal is critical for improving the spatial resolution in atomic-scale EDS mapping. A single-frame scanning technique is used in this study instead of the multiple-frame technique to avoid peak broadening due to tracking error. The strong thickness dependence is realized by measuring the full width at half maximamore » (FWHM) as well as the peak-to-valley (P/V) ratio of the EDS profiles for Ti K and Sr K+L, obtained at several crystal thicknesses. A FWHM of about 0.16 nm and a P/V ratio of greater than 7.0 are obtained for Ti K for a crystal thickness of less than 20 nm. In conclusion, with increasing crystal thickness, the FWHM and P/V ratio increases and decreases, respectively, indicating the advantage of using a thin crystal for high-resolution EDS mapping.« less

Near-field transport imaging applied to photovoltaic materials

DOE PAGES

Xiao, Chuanxiao; Jiang, Chun -Sheng; Moseley, John; ...

2017-05-26

We developed and applied a new analytical technique - near-field transport imaging (NF-TI or simply TI) - to photovoltaic materials. Charge-carrier transport is an important factor in solar cell performance, and TI is an innovative approach that integrates a scanning electron microscope with a near-field scanning optical microscope, providing the possibility to study luminescence associated with recombination and transport with high spatial resolution. In this paper, we describe in detail the technical barriers we had to overcome to develop the technique for routine application and the data-fitting procedure used to calculate minority-carrier diffusion length values. The diffusion length measured bymore » TI agrees well with the results calculated by time-resolved photoluminescence on well-controlled gallium arsenide (GaAs) thin-film samples. We report for the first time on measurements on thin-film cadmium telluride using this technique, including the determination of effective carrier diffusion length, as well as the first near-field imaging of the effect of a single localized defect on carrier transport and recombination in a GaAs heterostructure. Furthermore, by changing the scanning setup, we were able to demonstrate near-field cathodoluminescence (CL), and correlated the results with standard CL measurements. In conclusion, the TI technique shows great potential for mapping transport properties in solar cell materials with high spatial resolution.« less

Studies of x-ray localization and thickness dependence in atomic-scale elemental mapping by STEM energy-dispersive x-ray spectroscopy using single-frame scanning method.

PubMed

Lu, Ping; Moya, Jaime M; Yuan, Renliang; Zuo, Jian Min

2018-03-01

The delocalization of x-ray signals limits the spatial resolution in atomic-scale elemental mapping by scanning transmission electron microscopy (STEM) using energy-dispersive x-ray spectroscopy (EDS). In this study, using a SrTiO 3 [001] single crystal, we show that the x-ray localization to atomic columns is strongly dependent on crystal thickness, and a thin crystal is critical for improving the spatial resolution in atomic-scale EDS mapping. A single-frame scanning technique is used in this study instead of the multiple-frame technique to avoid peak broadening due to tracking error. The strong thickness dependence is realized by measuring the full width at half maxima (FWHM) as well as the peak-to-valley (P/V) ratio of the EDS profiles for Ti K and Sr K + L, obtained at several crystal thicknesses. A FWHM of about 0.16 nm and a P/V ratio of greater than 7.0 are obtained for Ti K for a crystal thickness of less than 20 nm. With increasing crystal thickness, the FWHM and P/V ratio increases and decreases, respectively, indicating the advantage of using a thin crystal for high-resolution EDS mapping. Published by Elsevier B.V.