Temperature-triggered shape-transformations in layer-by-layer microtubes

2014 ◽  
Vol 2 (15) ◽  
pp. 2088-2092 ◽  
Author(s):  
Choonghyun Sung ◽  
Ajay Vidyasagar ◽  
Katelin Hearn ◽  
Jodie L. Lutkenhaus
Keyword(s):  
High Temperatures ◽  
Layer By Layer ◽  
Shape Transformations ◽  
Rayleigh Instabilities

Freely released microtubes in water transform to ellipsoids and spheres at high temperatures, while microtubes bound to the template surface showed periodic voids suggestive of Rayleigh instabilities.

High Temperature n- and p-type Doped Microcrystalline Silicon Layers Grown by VHF PECVD Layer-by-Layer Deposition

2003 ◽  
Vol 762 ◽  
Author(s):  
A. Gordijn ◽  
J.K. Rath ◽  
R.E.I. Schropp
Keyword(s):  
Activation Energy ◽  
High Temperature ◽  
High Temperatures ◽  
Continuous Wave ◽  
Hydrogen Plasma ◽  
Silicon Layer ◽  
Dark Conductivity ◽  
High Deposition Rate ◽  
Layer By Layer ◽  
Microcrystalline Silicon

AbstractDue to the high temperatures used for high deposition rate microcrystalline (μc-Si:H) and polycrystalline silicon, there is a need for compact and temperature-stable doped layers. In this study we report on films grown by the layer-by-layer method (LbL) using VHF PECVD. Growth of an amorphous silicon layer is alternated by a hydrogen plasma treatment. In LbL, the surface reactions are separated time-wise from the nucleation in the bulk. We observed that it is possible to incorporate dopant atoms in the layer, without disturbing the nucleation. Even at high substrate temperatures (up to 400°C) doped layers can be made microcrystalline. At these temperatures, in the continuous wave case, crystallinity is hindered, which is generally attributed to the out-diffusion of hydrogen from the surface and the presence of impurities (dopants).We observe that the parameter window for the treatment time for p-layers is smaller compared to n-layers. Moreover we observe that for high temperatures, the nucleation of p-layers is more adversely affected than for n-layers. Thin, doped layers have been structurally, optically and electrically characterized. The best n-layer made at 400°C, with a thickness of only 31 nm, had an activation energy of 0.056 eV and a dark conductivity of 2.7 S/cm, while the best p-layer made at 350°C, with a thickness of 29 nm, had an activation energy of 0.11 V and a dark conductivity of 0.1 S/cm. The suitability of these high temperature n-layers has been demonstrated in an n-i-p microcrystalline silicon solar cell with an unoptimized μc-Si:H i-layer deposited at 250°C and without buffer. The Voc of the cell is 0.48 V and the fill factor is 70 %.

Long-Term Stability at High Temperatures for Birefringence in PAZO/PAH Layer-by-Layer Films

2012 ◽  
Vol 4 (3) ◽  
pp. 1470-1477 ◽  
Author(s):  
Quirina Ferreira ◽  
Paulo A. Ribeiro ◽  
Osvaldo N. Oliveira ◽  
Maria Raposo
Keyword(s):  
High Temperatures ◽  
Layer By Layer ◽  
Term Stability ◽  
Long Term Stability

scholarly journals Volume-by-volume bioprinting of chondrocytes-alginate bioinks in high temperature thermoplastic scaffolds for cartilage regeneration

2019 ◽  
Vol 244 (1) ◽  
pp. 13-21 ◽  
Author(s):  
JM Baena ◽  
G Jiménez ◽  
E López-Ruiz ◽  
C Antich ◽  
C Griñán-Lisón ◽  
...  
Keyword(s):  
Lactic Acid ◽  
High Temperature ◽  
Cell Viability ◽  
High Temperatures ◽  
Cartilage Tissue ◽  
Poly Lactic Acid ◽  
Layer By Layer ◽  
3D Bioprinting ◽  
Thermoplastic Polymers ◽  
Mesh Structure

Biofabrication technologies with layer-by-layer simultaneous deposition of a polymeric matrix and cell-laden bioinks (also known as bioprinting) offer an alternative to conventional treatments to regenerate cartilage tissue. Thermoplastic polymers, like poly-lactic acid, are easy to print using fused deposition modeling, and the shape, mesh structure, biodegradation time, and stiffness can be easily controlled. Besides some of them being clinically approved, the high manufacturing temperatures used in bioprinting applications with these clinically available thermoplastics decrease cell viability. Geometric restriction prevents cell contact with the heated printed fibers, increasing cell viability but comprising the mechanical performance and biodegradation time of the printed parts. The objective of this study was to develop a novel volume-by-volume 3D-biofabrication process that divides the printed part into different volumes and injects the cells after each volume has been printed, once the temperature of the printed thermoplastic fibers has decreased. In order to show the suitability of this process, chondrocytes were isolated from osteoarthritic patient samples and after characterization were used to test the feasibility of the process. Human chondrocytes were bioprinted together with poly-lactic acid and apoptosis, proliferation and metabolic activity were analyzed. This novel volume-by-volume 3D-biofabrication procedure prints a mesh structure layer-by-layer with a high adhesion surface/volume ratio, driving a rapid decrease in the temperature, avoiding contact with cells in high temperature zones. In our study, chondrocytes survived the manufacturing process, with 90% of viability, 2 h after printing, and, after seven days in culture, chondrocytes proliferated and totally colonized the scaffold. The use of the volume-by-volume-based biofabrication process presented in this study shows valuable potential in the short-term development of bioprint-based clinical therapies for cartilage injuries. Impact statement 3D bioprinting represents a novel advance in the area of regenerative biomedicine and tissue engineering for the treatment of different pathologies, among which are those related to cartilage. Currently, the use of different thermoplastic polymers, such as PLA or PCL, for bioprinting processes presents an important limitation: the high temperatures that are required for extrusion affect the cell viability and the final characteristics of the construct. In this work, we present a novel bioprinting process called volume-by-volume (VbV) that allows us to preserve cell viability after bioprinting. This procedure allows cell injection at a safe thermoplastic temperature, and also allows the cells to be deposited in the desired areas of the construct, without the limitations caused by high temperatures. The VbV process could make it easier to bring 3D bioprinting into the clinic, allowing the generation of tissue constructs with polymers that are currently approved for clinical use.

High-Temperature Dielectric Materials from Atomically-Thin Perovskites

2016 ◽  
Vol 2016 (CICMT) ◽  
pp. 000164-000168
Author(s):  
Minoru Osada ◽  
Takayoshi Sasaki
Keyword(s):  
Thermal Stability ◽  
High Temperature ◽  
High Temperatures ◽  
Electronic Materials ◽  
Dielectric Materials ◽  
Layered Compound ◽  
Layer By Layer ◽  
High K ◽  
Thermal Stability Of

Abstract The search of new electronic materials for high-temperature applications has been a significant challenge in recent years. In automotive industries, for example, cutting-edge technology requires electronic components operable at high temperatures (> 200 °C). The absence of suitable capacitors is one of the major barriers to meet this goal. Here we provide a solution to these issues by using an atomically-thin perovskite nanosheet (Ca2Nb3O10), a two-dimensional material derived from the exfoliation of a layered compound. Through in-situ characterizations, we found a robust thermal stability of Ca2Nb3O10 nanosheet even in a monolayer form (~ 2 nm). Furthermore, layer-by-layer assembled nanocapacitors retained both size-free high-εr characteristic and high insulation resistance at high temperatures up to 250 °C. The simultaneous improvement of εr and thermal stability in high-k nanodielectrics is of critical technological importance for the use of high-temperature capacitors.

Microstructural characterization of CoPtCr/Cr thin film disks by cross-section TEM and elongated probe micro-diffraction

1991 ◽  
Vol 49 ◽  
pp. 762-763
Author(s):  
M.A. Parker ◽  
K.E. Johnson ◽  
C. Hwang ◽  
A. Bermea
Keyword(s):  
Magnetic Recording ◽  
Electron Probe ◽  
Microstructural Characterization ◽  
Crystallographic Structure ◽  
Recording Media ◽  
Layer By Layer ◽  
Cross Sectional ◽  
New Techniques ◽  
Polished Side

We have reported the dependence of the magnetic and recording properties of CoPtCr recording media on the thickness of the Cr underlayer. It was inferred from XRD data that grain-to-grain epitaxy of the Cr with the CoPtCr was responsible for the interaction observed between these layers. However, no cross-sectional TEM (XTEM) work was performed to confirm this inference. In this paper, we report the application of new techniques for preparing XTEM specimens from actual magnetic recording disks, and for layer-by-layer micro-diffraction with an electron probe elongated parallel to the surface of the deposited structure which elucidate the effect of the crystallographic structure of the Cr on that of the CoPtCr.XTEM specimens were prepared from magnetic recording disks by modifying a technique used to prepare semiconductor specimens. After 3mm disks were prepared per the standard XTEM procedure, these disks were then lapped using a tripod polishing device. A grid with a single 1mmx2mm hole was then glued with M-bond 610 to the polished side of the disk.

In situ REM imaging of surface processes on ceramic bulk crystals from 300 to 1670 K in a conventional TEM

1991 ◽  
Vol 49 ◽  
pp. 660-661
Author(s):  
Z. L. Wang ◽  
J. Bentley
Keyword(s):  
High Temperatures ◽  
Image Resolution ◽  
Atomic Processes ◽  
Crystal Surfaces ◽  
Beam Radiation ◽  
Surface Areas ◽  
Transmission Electron ◽  
Reflection Electron Microscopy ◽  
Gas Reactions

Studying the behavior of surfaces at high temperatures is of great importance for understanding the properties of ceramics and associated surface-gas reactions. Atomic processes occurring on bulk crystal surfaces at high temperatures can be recorded by reflection electron microscopy (REM) in a conventional transmission electron microscope (TEM) with relatively high resolution, because REM is especially sensitive to atomic-height steps.Improved REM image resolution with a FEG: Cleaved surfaces of a-alumina (012) exhibit atomic flatness with steps of height about 5 Å, determined by reference to a screw (or near screw) dislocation with a presumed Burgers vector of b = (1/3)<012> (see Fig. 1). Steps of heights less than about 0.8 Å can be clearly resolved only with a field emission gun (FEG) (Fig. 2). The small steps are formed by the surface oscillating between the closely packed O and Al stacking layers. The bands of dark contrast (Fig. 2b) are the result of beam radiation damage to surface areas initially terminated with O ions.

Epitaxial growth manner and structure of superconducting oxide films

1990 ◽  
Vol 48 (4) ◽  
pp. 2-3
Author(s):  
Yoshichika Bando ◽  
Takahito Terashima ◽  
Kenji Iijima ◽  
Kazunuki Yamamoto ◽  
Kazuto Hirata ◽  
...  
Keyword(s):  
Ultrathin Films ◽  
Film Surface ◽  
High Energy ◽  
Epitaxial Films ◽  
Layer By Layer ◽  
Initial Growth ◽  
In Situ Growth ◽  
High Quality ◽  
Activated Reactive Evaporation

The high quality thin films of high-Tc superconducting oxide are necessary for elucidating the superconducting mechanism and for device application. The recent trend in the preparation of high-Tc films has been toward “in-situ” growth of the superconducting phase at relatively low temperatures. The purpose of “in-situ” growth is to attain surface smoothness suitable for fabricating film devices but also to obtain high quality film. We present the investigation on the initial growth manner of YBCO by in-situ reflective high energy electron diffraction (RHEED) technique and on the structural and superconducting properties of the resulting ultrathin films below 100Å. The epitaxial films have been grown on (100) plane of MgO and SrTiO, heated below 650°C by activated reactive evaporation. The in-situ RHEED observation and the intensity measurement was carried out during deposition of YBCO on the substrate at 650°C. The deposition rate was 0.8Å/s. Fig. 1 shows the RHEED patterns at every stage of deposition of YBCO on MgO(100). All the patterns exhibit the sharp streaks, indicating that the film surface is atomically smooth and the growth manner is layer-by-layer.

Compact back-scattered electrons' energy analyzer for standard SEM

1994 ◽  
Vol 52 ◽  
pp. 488-489
Author(s):  
S. Likharev ◽  
A. Kramarenko ◽  
V. Vybornov
Keyword(s):  
Depth Resolution ◽  
High Energy ◽  
Primary Beam ◽  
Layer By Layer ◽  
Energy Analyzer ◽  
High Energy Part ◽  
Small Window ◽  
Energy Part ◽  
Wide Range ◽  
High Voltage Supply

At present time the interest is growing considerably for theoretical and experimental analysis of back-scattered electrons (BSE) energy spectra. It was discovered that a special angle and energy nitration of BSE flow could be used for increasing a spatial resolution of BSE mode, sample topography investigations and for layer-by layer visualizing of a depth structure. In the last case it was shown theoretically that in order to obtain suitable depth resolution it is necessary to select a part of BSE flow with the directions of velocities close to inverse to the primary beam and energies within a small window in the high-energy part of the whole spectrum.A wide range of such devices has been developed earlier, but all of them have considerable demerit: they can hardly be used with a standard SEM due to the necessity of sufficient SEM modifications like installation of large accessories in or out SEM chamber, mounting of specialized detector systems, input wires for high voltage supply, screening a primary beam from additional electromagnetic field, etc. In this report we present a new scheme of a compact BSE energy analyzer that is free of imperfections mentioned above.

Transmission Electron Microscopy characterization of epitaxial III-V semiconductor thin films grown on Si(100) by ion-assisted deposition

1990 ◽  
Vol 48 (4) ◽  
pp. 686-687
Author(s):  
L. Hultman ◽  
C.-H. Choi ◽  
R. Kaspi ◽  
R. Ai ◽  
S.A. Barnett
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Ion Irradiation ◽  
High Energy ◽  
Nucleation Mechanism ◽  
Layer By Layer ◽  
Extended Defect ◽  
Island Formation ◽  
Si Substrates ◽  
Transmission Electron

III-V semiconductor films nucleate by the Stranski-Krastanov (SK) mechanism on Si substrates. Many of the extended defects present in the films are believed to result from the island formation and coalescence stage of SK growth. We have recently shown that low (-30 eV) energy, high flux (4 ions per deposited atom), Ar ion irradiation during nucleation of III-V semiconductors on Si substrates prolongs the 1ayer-by-layer stage of SK nucleation, leading to a decrease in extended defect densities. Furthermore, the epitaxial temperature was reduced by >100°C due to ion irradiation. The effect of ion bombardment on the nucleation mechanism was explained as being due to ion-induced dissociation of three-dimensional islands and ion-enhanced surface diffusion.For the case of InAs grown at 380°C on Si(100) (11% lattice mismatch), where island formation is expected after ≤ 1 monolayer (ML) during molecular beam epitaxy (MBE), in-situ reflection high-energy electron diffraction (RHEED) showed that 28 eV Ar ion irradiation prolonged the layer-by-layer stage of SK nucleation up to 10 ML. Otherion energies maintained layer-by-layer growth to lesser thicknesses. The ion-induced change in nucleation mechanism resulted in smoother surfaces and improved the crystalline perfection of thicker films as shown by transmission electron microscopy and X-ray rocking curve studies.

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