Size-dependent melting point depression of nanostructures: Nanocalorimetric measurements

Zhang, M.; Efremov, Mikhail Yu.; Schiettekatte, F.; Olson, E. A.; Kwan, A. T.; Lai, S. L.; Wisleder, T.; Greene, J. E.; Allen, L. H.

doi:10.1103/physrevb.62.10548

Cited by 445 publications

(322 citation statements)

References 34 publications

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“…For this to be true, the 1789℃ bulk melting point of Pt would have to be depressed to the 900℃ substrate temperature during growth. This could be achieved by a combination of Pt particle size effect 19 and Ga alloying.…”

mentioning

confidence: 99%

Focused-ion-beam platinum nanopatterning for GaN nanowires: Ohmic contacts and patterned growth

Nam

Kim

Fischer

2005

Applied Physics Letters

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Nanopatterned Pt by Ga + focused ion beam (FIB) decomposition of an organometallic precursor forms low resistance ohmic contacts on 40-70 nm diameter GaN nanowires (NWs) grown by thermal reaction of Ga 2 O 3 and NH 3 . With no intentional doping, the wires are presumed to be n-type. Thus, the linear I-V behavior is surprising since evaporated Pt usually forms Schottky barriers on n-GaN. Ohmic behavior was not obtained for 130-140 diameter wires, even with thicker Pt contacts. A second application of FIB Pt nanopatterning was demonstrated by position-selective growth of GaN NWs on Pt catalyst dots. NW locations and density are defined by the position, size, and thickness of the Pt deposit. Combining these techniques provides a versatile platform for nanostructure research and development. Letters, Volume 86, Article 193112, 2005, 3 Achieving reliable low resistance ohmic contacts to GaN is not trivial. High contact resistance often degrades the performance of GaN-based devices. 1 Low resistance ohmic contacts to n-type GaN are generally obtained by Ti deposition and conventional lithography. Similar metals and methods have been applied to GaN NWs, 2,3 but these require a tedious sequence of locating NWs on a substrate by atomic force microscopy (AFM), defining a contact pattern with e-beam lithography, metal deposition and removal of e-beam resist. In addition, achieving robust ohmic contacts requires work function tuning and deposition of an adhesion layer to insure mechanical stability. Attracted by its convenience and versatility, several groups reported the use of direct Pt deposition by focused ion beam (FIB) to make metal contacts on Bi and Ag NWs 4,5 and carbon nanotubes 5 . This is done by locally decomposing a fine jet of organometallic vapor with the highly focused and spatially controlled Ga + ion beam (I-beam). 5 Since most FIB systems are also equipped with high resolution scanning electron microscopy (SEM), the combination provides unique capabilities of fast and precise metal contact patterning. Here we demonstrate direct FIB nanopatterning of low resistance ohmic Pt contacts on n-type GaN NWs grown by Ga 2 O 3 -NH 3 reaction without intentional doping. It is surprising for FIB patterned Pt to form low resistance ohmic contacts on n-type GaN since Pt generally forms a Schottky barrier on n-type GaN. 6 In the second part of this letter we exploit the same spatial selectivity to create patterned Pt nano-catalysts, which constrain GaN NW nucleation to these small selected regions. Comments Postprint version. Published in Applied PhysicsThe details of GaN NW synthesis are described in a previous report. 7 We used sputter-deposited Au/Pd catalyst layers on Si substrates. Two different layer thicknesses yielded two different NW diameters, i.e. 40-70 nm and 130-140 nm, with which we could study the effect of NW diameter on I-V characteristics. NWs were then transferred to 200 nm SiO x on Si chips with Cr/Au (10 µm/50 µm) contact pads predeposited by e-beam lithography and thermal evaporation. Th...

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confidence: 99%

Focused-ion-beam platinum nanopatterning for GaN nanowires: Ohmic contacts and patterned growth

Nam

Kim

Fischer

2005

Applied Physics Letters

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“…This result indicated that the crystal morphology of the treated sodium selenate was changed from the control sample and The Trivedi Effect ® -Biofield Energy Healing might lead to a new polymorphic form of sodium selenate. The particle sizes d 10 , d 50 , and d 90 values of the treated sample were significantly decreased by 3.40%, 9.75%, and 8.52%, respectively as compared to the control sample. Additionally, the surface area of the treated sample was increased by 5.26% from the control sample.…”

Section: Resultsmentioning

confidence: 77%

“…Interestingly, the latent heat of fusion (∆H) of the treated sodium selenate (96.77 J/g) was lower by 8.01% from the control sample (∆H = 105.2 J/g). Literature demonstrated that decreased particle size depress the latent heat of fusion [50]. As the treated sample has reduced particle size, it has lower latent heat of fusion compared with the control sample.…”

Section: Differential Scanning Calorimetry (Dsc) Analysismentioning

confidence: 99%

“…Particle sizes (d 10 , d 50 , and d 90 ) and surface area of both the control and treated sodium selenate were explored and the results are presented in Table 2. The size of the particles at below 10% level (d 10 * denotes the percentage change in the particle size data (d10, d50, and d90) and surface area of Biofield Energy Treated sample with respect to the control sample.…”

Section: Particle Size Distribution (Psd) Analysismentioning

confidence: 99%

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Investigation of Physicochemical, Spectral, and Thermal Properties of Sodium Selenate Treated with the Energy of Consciousness (The Trivedi Effect<sup>®</sup>)

Trivedi¹

2017

AJLS

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Sodium selenate is used for the prevention and treatment of various disorders like cancer, diabetes, inflammation diseases, etc. The objective of the current study was to evaluate the effect of The Trivedi Effect ® -Energy of Consciousness Healing Treatment (Biofield Energy Treatment) on physicochemical, spectral, and thermal properties of The Trivedi Effect ® -Biofield Energy Treated sodium selenate using various analytical methods such as PXRD, PSD, FT-IR, UV-vis spectroscopy, TGA, and DSC analysis. Sodium selenate was divided into two parts -one part was control without any treatment and another part was treated with The Trivedi Effect ® -Biofield Energy Healing Treatment remotely by eighteen renowned Biofield Energy Healers and defined as The Trivedi Effect ® -Energy of Consciousness Healing Treated sample. The PXRD analysis showed the significant alteration of the crystallite size of the treated sample in the range of -36.36% to 133.24% as compared to the control sample. However, the average crystallite size of the treated sample was significantly decreased by 8.31% as compared to the control sample. Overall, the crystal morphology of the treated sample was different from the control sample. The particle sizes d 10 , d 50 , and d 90 values of the treated sample were significantly decreased by 3.40%, 9.75%, and 8.52%, respectively as compared to the control sample. Consequently, the surface area of the treated sample was significantly increased by 5.26% from the control sample. Both the control and treated FT-IR spectra indicated the presence of sharp and strong absorption bands at 887 cm -1 due to the Se=O stretching. The UV-vis spectroscopic analysis displayed that the wavelength for the maximum absorbance of both the control and treated samples were at 204.1 and 204.0 nm, respectively. TGA analysis revealed that the total weight loss of the treated sample was reduced by 1.24% as compared with the control sample. The DSC analysis showed that the treated sample (588.77°C) had higher melting point than the control sample (588.60°C). The latent heat of fusion was reduced in the treated sample by 8.01% compared to the control sample. Thus, The Trivedi Effect ® -Biofield Energy Healing might lead to generate a new polymorphic (enantiotropic) form of sodium selenate which would be more soluble, bioavailable, and thermally stable compared with the untreated sample. The Trivedi Effect treated sodium selenate would be very useful to design better nutraceutical and/or pharmaceutical formulations that might offer better therapeutic response against inflammatory diseases, immunological disorders, stress, aging, infectious diseases, cancer, diabetes, heart diseases, Alzheimer's disease, etc.

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“…Nano-calorimetry is a very sensitive calorimetry technique capable of measuring the thermodynamic properties of nano-quantities of materials. The technique has been applied to study phase transformations in thin-film samples with thickness as small as a few nanometers [5,16,54,55,61,82,[94][95][96]. A recently developed scanning AC nano-calorimetry technique can be used to measure heat capacity over a wide range of temperatures (up to 1300 K) and heating rates (from isothermal to 3000 K/s) [22,24,81].…”

Section: Introductionmentioning

confidence: 99%

Scanning AC Nanocalorimetry and Its Applications

Xiao

Vlassak

2016

Fast Scanning Calorimetry

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This thesis presents an AC nanocalorimetry technique that enables calorimetry measurements on very small quantities of materials over a wide range of scanning rates (from isothermal to 3×10^3 K/s), temperatures (up to 1200 K), and environments. Such working range bridges the gap between traditional scanning calorimetry of bulk materials and nanocalorimetry. The method relies on a micromachined nanocalorimeter with negligible thermal lags between heater, thermometer, and sample. The ability to perform calorimetry measurements over such a broad range of scanning rates makes it an ideal tool to characterize the kinetics of phase transformations, reactions at elevated temperatures or to explore the behavior of materials far from equilibrium. We By combining scanning DC and AC nano-calorimetry techniques, we study the nucleation behavior of undercooled liquid Bi at cooling rates ranging from 10^1 to 10^4 K/s. Upon initial melting, the Bi thin-film sample breaks up into isolated islands. The number of islands in a typical sample is sufficiently large that highly repeatable nucleation behavior is observed, despite the stochastic nature of the nucleation process.We establish a data reduction technique to evaluate the nucleation rate from DC and AC calorimetry results. The results show that the driving force for the nucleation of melted Bi is well described by classical nucleation theory over a wide range of cooling rates. The proposed technique provides a unique and efficient way to examine nucleation kinetics v with cooling rates over several orders of magnitude. The technique is quite general and can be used to evaluate reaction kinetics in other materials.Lastly, we apply the scanning AC nanocalorimetry technique to study solid-gas phase reactions by measuring the change in heat capacity of a sample during reaction. We apply this approach to evaluate the oxidation kinetics of thin-film samples of zirconium in air. The results confirm parabolic oxidation kinetics with an activation energy of 0.59±0.03 eV. The nano-calorimetry measurements were performed using a device that contains an array of micromachined nano-calorimeter sensors in an architecture designed for combinatorial studies. We demonstrate that the oxidation kinetics can be quantified using a single sample, thus enabling high-throughput mapping of the composition-dependence of the reaction rate.vi

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Size-dependent melting point depression of nanostructures: Nanocalorimetric measurements

Cited by 445 publications

References 34 publications

Focused-ion-beam platinum nanopatterning for GaN nanowires: Ohmic contacts and patterned growth

Focused-ion-beam platinum nanopatterning for GaN nanowires: Ohmic contacts and patterned growth

Investigation of Physicochemical, Spectral, and Thermal Properties of Sodium Selenate Treated with the Energy of Consciousness (The Trivedi Effect<sup>®</sup>)

Scanning AC Nanocalorimetry and Its Applications

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Size-dependent melting point depression of nanostructures: Nanocalorimetric measurements

Cited by 445 publications

References 34 publications

Focused-ion-beam platinum nanopatterning for GaN nanowires: Ohmic contacts and patterned growth

Focused-ion-beam platinum nanopatterning for GaN nanowires: Ohmic contacts and patterned growth

Investigation of Physicochemical, Spectral, and Thermal Properties of Sodium Selenate Treated with the Energy of Consciousness (The Trivedi Effect&lt;sup&gt;®&lt;/sup&gt;)

Scanning AC Nanocalorimetry and Its Applications

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Investigation of Physicochemical, Spectral, and Thermal Properties of Sodium Selenate Treated with the Energy of Consciousness (The Trivedi Effect<sup>®</sup>)