Surface-Synthesized Graphene Nanoribbons for Room Temperature Switching Devices: Substrate Transfer and ex Situ Characterization

ABSTRACTIrradiation-induced amorphization of Cd2Nb2O7 pyrochlore was investigated by means of in-situ temperature-dependent ion-irradiation experiments in a transmission electron microscope, combined with ex-situ ion-implantation (at ambient temperature) and RBS/channeling analysis. The in-situ experiments were performed using Ne or Xe ions with energies of 280 and 1200 keV, respectively. For the bulk implantation experiments, the incident ion energies were 70 keV (Ne+) and 320 keV (Xe2+). The critical amorphization temperature for Cd2Nb2O7 is ∼480 K (280 keV Ne+) or ∼620 K (1200 keV Xe2+). The dose for in-situ amorphization at room temperature is 0.22 dpa for Xe2+, but is 0.65 dpa for Ne+ irradiation. Both types of experiments suggest a cascade overlap mechanism of amorphization. The results were analyzed in light of available models for the crystalline-to-amorphous transformation and were compared to previous ionirradiation experiments on other pyrochlore compositions.

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Phase Transformations in Sol-Gel PZT Thin Films

MRS Proceedings ◽

10.1557/proc-623-185 ◽

2000 ◽

Vol 623 ◽

Cited By ~ 1

Author(s):

D.P. Eakin ◽

M.G. Norton ◽

D.F. Bahr

Keyword(s):

Thin Films ◽

Heat Treatment ◽

Room Temperature ◽

Structural Changes ◽

Sol Gel ◽

Ex Situ ◽

Ambient Conditions ◽

Crystalline Films ◽

In Situ Heating

AbstractThin films of PZT were deposited onto platinized and bare single crystal NaCl using spin coating and sol-gel precursors. These films were then analyzed using in situ heating in a transmission electron microscope. The results of in situ heating are compared with those of an ex situ heat treatment in a standard furnace, mimicking the heat treatment given to entire wafers of these materials for use in MEMS and ferroelectric applications. Films are shown to transform from amorphous to nanocrystalline over the course of days when held at room temperature. While chemical variations are found between films crystallized in ambient conditions and films crystallized in the vacuum conditions of the microscope, the resulting crystal structures appear to be insensitive to these differences. Significant changes in crystal structure are found at 500°C, primarily the change from largely amorphous to the beginnings of clearly crystalline films. Crystallization does occur over the course of weeks at room temperature in these films. Structural changes are more modest in these films when heated in the TEM then those observed on actual wafers. The presence of Pt significantly influences both the resulting structure and morphology in both in situ and ex situ heated films. Without Pt present, the films appear to form small, 10 nm grains consisting of both cubic and tetragonal phases, whereas in the case of the Pt larger, 100 nm grains of a tetragonal phase are formed.

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Molecular Dynamics Study on Relaxation Characteristics of Graphene Nanoribbons at Room Temperature

Nanoscience and Nanotechnology Letters ◽

10.1166/nnl.2012.1457 ◽

2012 ◽

Vol 4 (12) ◽

pp. 1188-1193 ◽

Cited By ~ 6

Author(s):

Weidong Wang ◽

Chenglong Yi ◽

Xiang Ji ◽

Xiangyu Niu

Keyword(s):

Molecular Dynamics ◽

Room Temperature ◽

Graphene Nanoribbons ◽

Relaxation Characteristics

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Heteroepitaxy of Ge on Vicinal Si(100)

MRS Proceedings ◽

10.1557/proc-198-409 ◽

1990 ◽

Vol 198 ◽

Cited By ~ 4

Author(s):

Mohan Krishnamurthy ◽

Jeff S. Drucker ◽

J.A. Venables

Keyword(s):

Intermediate Layer ◽

Room Temperature ◽

Secondary Electron ◽

Elevated Temperatures ◽

Film Growth ◽

Growth Parameters ◽

Ex Situ ◽

Nucleation Density ◽

Size Distributions ◽

Surface Steps

ABSTRACTThe initial stages of germanium heteroepitaxy on vicinal Si(100) have been studied using in-situ deposition in a UHV STEM. Germanium was deposited using molecular beam techniques onto substrates misoriented 1° and 5* toward <110> held at room temperature, 375°C and 525°C. Film thicknesses were in the range 4-6 ML, just greater than the stable intermediate layer of 3-4ML (1ML = 0.14nm). The Ge clusters were observed using biassed secondary electron (b-SE) imaging with nanometer resolution. Comparisons were made between deposition at the elevated temperatures, and room temperature deposition followed by anneals at the same temperatures.Annealing the low temperature deposits produces coarsening of the islands which is similar on the 1° and 5° samples. Island size distributions and other film growth parameters obtained from the 375°C and 525°C anneals indicate that the coarsening is different at these temperatures and is possibly affected by instabilities in the intermediate layer. Results of the high temperature depositions indicate that neither surface steps nor the edges of islands act as perfect sinks, and that diffusion distances are of the order of several microns. The nucleation density and size distributions are markedly different for deposition at 375°C and 525°C possibly due to competitive capture at strong sinks.In a parallel set of experiments in a standard UHV chamber, macroscopic wafer samples were analyzed with RHEED, Auger and secondary electron spectroscopy. These correlate well with the intermediate layer thicknesses previously reported in the literature, and the large contrast observed in the b-SE images. Ex situ TEM studies of samples grown in this chamber show islands with various contrast features including those of coherent strain.

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Seed longevity, viability and germination of four weed-ruderal Asteraceae species of ethnobotanic value

Botanical Sciences ◽

10.17129/botsci.2743 ◽

2021 ◽

Vol 99 (2) ◽

pp. 279-290

Author(s):

Andrea Mariel Jiménez-Vázquez ◽

Alejandro Flores-Palacios ◽

Alejandro Flores-Morales ◽

Irene Perea-Arango ◽

María del Carmen Gutiérrez ◽

...

Keyword(s):

Room Temperature ◽

Storage Temperature ◽

Seed Viability ◽

Biological Properties ◽

Seed Longevity ◽

Ex Situ ◽

Cold Temperatures ◽

Design Production ◽

One Year ◽

Germination Experiments

Background: A high proportion of Asteraceae species are considered weeds, some of them have recognizable biological properties. To design production protocols and ex situ seed conservation programs is necessary to determine the effect of storage temperature on seed viability and longevity. It is known that cold temperatures maintain seed viability and thus prolong seed longevity. Hypotheses: The seeds of Aldama dentata, Verbesina virgata, Stevia origanoides and Roldana barba-johannis stored at low temperature (5 ºC) will have greater longevity than when stored at room temperature (16.45 ± 1.94 oC) and will decrease their viability as they age. Study site and dates: Seeds of the four Asteraceae were collected (November-December 2015) in The National Park “El Tepozteco”, Morelos, Mexico and in the “Chamilpa” campus of the Universidad Autónoma del Estado de Morelos. Methods: The monthly germination experiments (11) were implemented with seeds stored under both temperatures, germination (%) and mean germination time were registered to estimate seed longevity. The seed viability stored at room temperature was evaluated with the tetrazolium test. Results: Germination and viability decreased with seed age. Along the experiment, seed germination was similar at both storage temperatures. A. dentata and S. origanoides showed the highest germination but A. dentata alone reached the major seed viability. The oldest seeds germinated faster. Conclusions: Seed longevity of all the species exceeded one year. For propagation purposes, it is recommended to use seeds between 8 and 9 months of age, when their germination and viability are the highest.

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Optical and Physical Characterization of Cu2-xSe Thin Films for Real Time Spectroscopic Ellipsometry on Cu(In,Ga)Se2-based Photovoltaic Devices

MRS Proceedings ◽

10.1557/proc-1210-q06-02 ◽

2009 ◽

Vol 1210 ◽

Cited By ~ 2

Author(s):

James D Walker ◽

Himal Khatri ◽

Scott Little ◽

Vikash Ranjan ◽

Robert Collins ◽

...

Keyword(s):

Real Time ◽

Spectroscopic Ellipsometry ◽

Growth Temperature ◽

Room Temperature ◽

Optical Model ◽

High Efficiency ◽

Optical Feedback ◽

High Surface ◽

Ex Situ ◽

Photovoltaic Devices

AbstractIn situ, real time spectroscopic ellipsometry (RTSE) has been used to study the growth processes and optical properties of Cu2-xSe - an important binary compound in the fabrication of high efficiency copper indium gallium diselenide (CIGS) photovoltaic devices. It was found that the high surface roughness of the Cu2-xSe layers necessitated a “graded” optical model in order to extract meaningful dielectric functions at both 550 °C and room temperature. The optical model was verified at room temperature against SEM micrographs and reflectance measurements carried out ex situ. The growth temperature dielectric functions presented in this study are expected to allow for a greater level of control and understanding of the so-called 2- and 3-stage processes for CIGS fabrication in which a Cu2-xSe phase, present at the CIGS grain boundaries, acts as a fluxing agent for the growth of photovoltaic quality CIGS. Real time optical feedback via RTSE combined with the growth temperature dielectric functions presented here could play an important role in improving material fabrication on both the laboratory and industrial scales.

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Covalent Silicon Bonding At Room Temperature In Ultrahigh Vacuum

MRS Proceedings ◽

10.1557/proc-483-141 ◽

1997 ◽

Vol 483 ◽

Author(s):

Andreas Plöbl ◽

Heinz Stenzel ◽

Qin-Yi Tong ◽

Martin Langenkamp ◽

Cord Schmidthals ◽

...

Keyword(s):

Heat Treatment ◽

Room Temperature ◽

Ultrahigh Vacuum ◽

Bonding Process ◽

Ex Situ ◽

Hydrogen Passivation ◽

Bulk Silicon ◽

Chemical Cleaning ◽

Covalent Bonds ◽

Subsequent Activation

AbstractOne possibility of a low temperature joining techniques relies on the bonding of atomically clean surfaces. Results on the application of this method to silicon direct bonding are being presented. Clean surfaces for bonding were prepared by ex situ chemical cleaning with ensuing hydrogen passivation and their subsequent activation by thermal desorption of the hydrogen in ultrahigh vacuum (UHV). In UHV at room temperature, the wafers were gently brought into contact to initiate the bonding process. Without any subsequent heat treatment, the adhesive strength thus achieved was equivalent to the cohesion of bulk silicon: covalent bonds join the two crystals.

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Ex situ integration of iron oxide nanoparticles onto the exfoliated expanded graphite flakes in water suspension

Journal of the Serbian Chemical Society ◽

10.2298/jsc131121019j ◽

2014 ◽

Vol 79 (9) ◽

pp. 1155-1167 ◽

Cited By ~ 3

Author(s):

Natasa Jovic ◽

Maria Calatayud ◽

Beatriz Sanz ◽

Amelia Montone ◽

Gerardo Goya

Keyword(s):

Iron Oxide ◽

Iron Oxide Nanoparticles ◽

Room Temperature ◽

Expanded Graphite ◽

Ex Situ ◽

Hybrid Structures ◽

Chemical Characteristics ◽

Oxide Nanoparticles ◽

Physico Chemical ◽

Branched Polyethylenimine

Hybrid structures composed of exfoliated expanded graphite (EG) and iron oxide nanocrystals have been produced by an ex situ process. The iron oxide nanoparticles coated with meso-2,3-dimercaptosuccinic acid (DMSA), or poly(acrylic) acid (PAA) were integrated onto the exfoliated EG flakes by mixing their aqueous suspensions at room temperature under support of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC) and N-hydroxysuccin-nimide (NHS). EG flakes have been used both, naked and functionalized with branched polyethylenimine (PEI). Complete integration of two constituents has been achieved and mainteined stable for more than 12 months. No preferential spatial distribution of anchoring sites for attachement of iron oxide nanoparticles has been observed, regardless EG flakes have been used naked or functionalized with PEI molecules. The structural and physico-chemical characteristics of the exfoliated expanded graphite and its hybrids nanostructures has been investigated by SEM, TEM, FTIR and Raman techniques.

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