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17 Jul 2006

Volume 89, Issue 3, Articles (03xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 89, 031107 (2006); http://dx.doi.org/10.1063/1.2222329 (3 pages)

Jiaguang Han, Zhiyuan Zhu, Sanith Ray, Abul K. Azad, Weili Zhang, Mingxia He, Shihong Li, and Yiping Zhao
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Metallic behavior of copper sulfide nanowires grown within Na-4 mica

Pijush Kanti Mukherjee, Anindita Bose, and Dipankar Chakravorty

Appl. Phys. Lett. 89, 033101 (2006); http://dx.doi.org/10.1063/1.2221873 (3 pages) | Cited 1 time

Online Publication Date: 17 July 2006

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Copper sulfide nanowires of diameter of ∼ 1.2 nm were grown within the crystal channels of Na-4 mica. These consist of both CuS and Cu2S strands. Electrical conduction over the temperature range of 130–300 K was characterized by very low activation energies in the range of 0.008–0.004 eV. The nanocomposites exhibit giant dielectric permittivity of ∼ 1617 which has been explained on the basis of one-dimensional metallic nanowires as predicted by the Gorkov-Eliashberg [Sov. Phys. JETP 21, 940 (1965) ] and Rice-Bernasconi [Phys. Rev. Lett. 29, 113 (1972) ] models.
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73.63.Nm Quantum wires
68.65.La Quantum wires (patterned in quantum wells)
81.07.Vb Quantum wires
81.16.-c Methods of micro- and nanofabrication and processing

Direct synthesis and characterization of CdS nanobelts

Z. Q. Wang, J. F. Gong, J. H. Duan, H. B. Huang, S. G. Yang, X. N. Zhao, R. Zhang, and Y. W. Du

Appl. Phys. Lett. 89, 033102 (2006); http://dx.doi.org/10.1063/1.2222237 (3 pages) | Cited 30 times

Online Publication Date: 17 July 2006

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A method to directly synthesize single crystalline CdS nanobelts has been developed. The advantages of the method in rapid synthesis within several minutes and catalyst free comparing to the previous method propose a potential avenue to the further practical device production and applications. The as-synthesized CdS nanobelts grow along the [100] crystalline direction with usually 500–2000 nm in width and about tens to several hundred micrometers in length. Two luminescence peaks around 516 and 758 nm in room-temperature photoluminescence spectrum are ascribed to the band-to-band and trap emission, respectively.
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81.05.Dz II-VI semiconductors
81.16.Be Chemical synthesis methods
78.67.-n Optical properties of low-dimensional, mesoscopic, and nanoscale materials and structures
78.55.Et II-VI semiconductors

Using infrared laser to enhance field emission of carbon nanotube

J. D. Hwang, K. F. Chen, L. H. Chan, and Y. Y. Chang

Appl. Phys. Lett. 89, 033103 (2006); http://dx.doi.org/10.1063/1.2222337 (3 pages) | Cited 5 times

Online Publication Date: 17 July 2006

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Infrared laser has been used to irradiate carbon nanotube (CNT) powders and the performance of CNT emitter was enhanced. The CNTs were prepared by conventional electric arc discharge method and laser irradiation was processed by Nd:YAG infrared laser with a wavelength of 1064 nm. It was found that the turn-on electric field was significantly decreased for laser treated sample. As compared to the sample of no laser treatment, the emission current density was enhanced by a magnitude of 16.56 for 225 J/cm2 treated plus annealing one. Possible mechanism is discussed here.
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79.70.+q Field emission, ionization, evaporation, and desorption
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)

Single-electron transistors in GaN/AlGaN heterostructures

H. T. Chou, D. Goldhaber-Gordon, S. Schmult, M. J. Manfra, A. M. Sergent, and R. J. Molnar

Appl. Phys. Lett. 89, 033104 (2006); http://dx.doi.org/10.1063/1.2226454 (3 pages) | Cited 5 times

Online Publication Date: 17 July 2006

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We report transport properties of two single-electron transistors (SETs) on a GaN/AlGaN heterostructure. The first SET formed accidentally in a quantum point contact near pinchoff. Its small size produces large energy scales (a charging energy of 7.5 meV and well-resolved excited states). The second, intentionally fabricated SET is much larger. More than 100 uniformly spaced Coulomb oscillations yield a charging energy of 0.85 meV. Excited states are not resolvable in Coulomb diamonds, and Coulomb blockade peak height remains constant with increasing temperature, indicating that transport is through multiple quantum levels even at the 450 mK base electron temperature of our measurements. Coulomb oscillations of both SETs are highly stable, comparable to the best GaAs SETs.
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85.35.Gv Single electron devices

Enhanced light extraction from circular Bragg grating coupled microcavities

Mark Y. Su and Richard P. Mirin

Appl. Phys. Lett. 89, 033105 (2006); http://dx.doi.org/10.1063/1.2222345 (3 pages) | Cited 2 times

Online Publication Date: 18 July 2006

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A sevenfold enhancement of light extraction over a 130 nm bandwidth from a semiconductor at room temperature was achieved using circular Bragg gratings (CBGs) etched around the periphery of a vertical-cavity light-emitting structure. The CBG defined an in-plane circular cavity for light trapped in guided modes. Maximum enhancement was observed with CBGs that efficiently coupled circular cavity modes into resonant extracted modes of the vertical cavity. The enhancement factor corresponded to a 41% external efficiency.
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42.79.Dj Gratings

Special cantilever geometry for the access of higher oscillation modes in atomic force microscopy

S. Sadewasser, G. Villanueva, and J. A. Plaza

Appl. Phys. Lett. 89, 033106 (2006); http://dx.doi.org/10.1063/1.2226993 (3 pages) | Cited 12 times

Online Publication Date: 18 July 2006

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Employing higher oscillation modes of microcantilevers promises higher sensitivity when applied as sensors, for example, for mass detection or in atomic force microscopy. Introducing a special cantilever geometry, we show that the relation between the resonance frequencies of the first and second resonance modes can be modified to separate them further or to bring them closer together. In atomic force microscopy the latter is of special interest as the photodiode of the beam deflection detection limits the accessible frequency range. Using finite element simulations, we optimized the design of the modified cantilever geometry for a maximum reduction of the frequency of the second oscillation mode with respect to the first mode. Cantilevers were fabricated by silicon micromachining and subsequently utilized in an ultrahigh vacuum Kelvin probe force microscope imaging the surface potential of C60 on graphite.
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07.79.Lh Atomic force microscopes
68.37.Ps Atomic force microscopy (AFM)

Oxidation treatment of carbon nanotubes: An essential process in nanocomposite with RuO2 for supercapacitor electrode materials

Yong-Tae Kim and Tadaoki Mitani

Appl. Phys. Lett. 89, 033107 (2006); http://dx.doi.org/10.1063/1.2221872 (3 pages) | Cited 8 times

Online Publication Date: 19 July 2006

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In the nanocomposite of multiwalled carbon nanotubes (MWNTs) and RuO2 for supercapacitor electrode materials, upon immersion of the purified MWNT into a RuCl3 solution, Ru metal having no contribution to pseudocapacitance was unexpectedly formed on the MWNT surface by spontaneous reduction, because of the higher Fermi level of MWNT than the absolute energy level of Ru/RuCl3 pair. In contrast, no such phenomenon was observed for oxidized MWNT, because of lowered Fermi level and the surface carboxyl groups as protector against charge transfer. The oxidation treatment of MWNT is therefore not optional but rather is an essential process in nanocomposite.
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81.16.Pr Micro- and nano-oxidation
81.65.Mq Oxidation
82.47.Uv Electrochemical capacitors; supercapacitors
82.45.Fk Electrodes
81.07.De Nanotubes
84.32.Tt Capacitors

Self-assembling of InAs nanocrystals on GaAs: The effect of electronic coupling and embedded gold nanoparticles on the photoluminescence

Y. Paltiel, A. Aharoni, U. Banin, O. Neuman, and R. Naaman

Appl. Phys. Lett. 89, 033108 (2006); http://dx.doi.org/10.1063/1.2221886 (3 pages) | Cited 6 times

Online Publication Date: 19 July 2006

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InAs/ZnSe core/shell nanoparticles (NP) were self-assembled on GaAs substrates using different organic molecules of varying length and properties as linkers. The molecules provide control over the coupling and tunneling properties between the substrate and the nanocrystals. By coadsorbing of gold NP on the GaAs substrate, enhancement of the photoluminescence from the InAs NP was achieved. The enhancement factor was found to depend on the properties of the organic linkers.
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81.16.Dn Self-assembly
78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
73.63.Bd Nanocrystalline materials
73.40.Gk Tunneling
78.55.Cr III-V semiconductors
68.43.Mn Adsorption kinetics

Deterministic nanoassembly: Neutral or plasma route?

I. Levchenko, K. Ostrikov, M. Keidar, and S. Xu

Appl. Phys. Lett. 89, 033109 (2006); http://dx.doi.org/10.1063/1.2222249 (3 pages) | Cited 60 times

Online Publication Date: 19 July 2006

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It is shown that, owing to selective delivery of ionic and neutral building blocks directly from the ionized gas phase and via surface migration, plasma environments offer a better deal of deterministic synthesis of ordered nanoassemblies compared to thermal chemical vapor deposition. The results of hybrid Monte Carlo (gas phase) and adatom self-organization (surface) simulation suggest that higher aspect ratios and better size and pattern uniformity of carbon nanotip microemitters can be achieved via the plasma route.
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81.07.Bc Nanocrystalline materials
52.77.Dq Plasma-based ion implantation and deposition
81.16.Dn Self-assembly
81.16.Rf Micro- and nanoscale pattern formation
68.35.Fx Diffusion; interface formation
85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices

Thermal contributions to the bending of bimaterial cantilever sensors

Jun Zhao, Rüdiger Berger, and Jochen S. Gutmann

Appl. Phys. Lett. 89, 033110 (2006); http://dx.doi.org/10.1063/1.2222346 (3 pages) | Cited 6 times

Online Publication Date: 19 July 2006

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The thickness dependent contribution of thermal expansion and surface potential to the thermal response behavior of polymer coated micromechanical cantilevers is investigated. Polystyrene films in a thickness range of 2–150 nm are used as coatings on silicon micromechanical cantilever arrays. Depending on coating thickness, either thermal expansion or interfacial tension dominates the response. For thick films we obtain a thermal expansion coefficient of 2.3×10−5±1.0×10−5 °C−1 for the polystyrene coating. Using this value a temperature coefficient of interfacial tension of −50×10−5±14×10−5 J m−2 °C−1 is determined for the silicon oxide/polystyrene interface. This establishes a method to measure the temperature coefficient of interfacial tension at solid/solid interfaces.
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07.10.Cm Micromechanical devices and systems
65.80.-g Thermal properties of small particles, nanocrystals, nanotubes, and other related systems
81.40.Lm Deformation, plasticity, and creep
62.20.F- Deformation and plasticity
07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices

Investigations of InAs surface dots on InP

C. Ellström, J. Trägårdh, L. Samuelson, W. Seifert, M.-E. Pistol, S. Lemeshko, and C. Pryor

Appl. Phys. Lett. 89, 033111 (2006); http://dx.doi.org/10.1063/1.2226699 (3 pages) | Cited 1 time

Online Publication Date: 19 July 2006

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We have fabricated InAs dots on the surface of InP, determined their structure, and measured the optical transition energy. This energy was found to be in excellent agreement with theoretical calculations, where no free parameters have been used. The calculations were performed using eight-band k∙p theory in the envelope function approximation. We conclude that this theory is adequate to describe quantum dots also when one of the confining materials is vacuum.
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81.07.Ta Quantum dots
81.05.Ea III-V semiconductors
68.65.Hb Quantum dots (patterned in quantum wells)
73.21.La Quantum dots
78.67.Hc Quantum dots
71.20.Nr Semiconductor compounds

Inhomogeneous effect of particle size on core-level and valence-band electrons: Size-dependent electronic structure of Cu3N nanoparticles

B. Balamurugan and Toshiro Maruyama

Appl. Phys. Lett. 89, 033112 (2006); http://dx.doi.org/10.1063/1.2227632 (3 pages) | Cited 4 times

Online Publication Date: 19 July 2006

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The present study reports a clear evidence and physical significance of an inhomogeneous effect of particle size on electrons originating from various electronic levels of copper nitride nanoparticles. X-ray photoelectron and optical absorption spectroscopy studies reveal that a direct modification of the valence band due to size effects explained by the more appropriate surface bond contraction model results in a strong increase in the binding energy of valence-band electrons as compared to core-level electrons.
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73.22.-f Electronic structure of nanoscale materials and related systems
79.60.Bm Clean metal, semiconductor, and insulator surfaces
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)
71.15.Nc Total energy and cohesive energy calculations

Fabrication of half-pitch 32 nm resist patterns using near-field lithography with a-Si mask

Toshiki Ito, Tomohiro Yamada, Yasuhisa Inao, Takako Yamaguchi, Natsuhiko Mizutani, and Ryo Kuroda

Appl. Phys. Lett. 89, 033113 (2006); http://dx.doi.org/10.1063/1.2227633 (3 pages) | Cited 5 times

Online Publication Date: 19 July 2006

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We evaluated the performances of Cr and amorphous Si (a-Si) films as light absorber materials for photomasks of near-field lithography on the basis of numerical studies using finite-difference time domain method and experimental results of fabrication process. With exposure experiments using both a Cr mask and an a-Si mask, fine performance of an a-Si near-field mask was demonstrated with respect to resolution. A half-pitch 32 nm resist pattern of 120 nm high was fabricated through the near-field lithography using the a-Si mask and a subsequent trilayer resist process.
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85.40.Hp Lithography, masks and pattern transfer
81.16.Nd Micro- and nanolithography
81.16.Rf Micro- and nanoscale pattern formation

Vertical GaP nanowires arranged at atomic steps on Si(111) substrates

K. Tateno, H. Hibino, H. Gotoh, and H. Nakano

Appl. Phys. Lett. 89, 033114 (2006); http://dx.doi.org/10.1063/1.2227800 (3 pages) | Cited 17 times

Online Publication Date: 20 July 2006

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We report vertical GaP nanowires self-arranged in lines formed from Au islands that were initially arranged at single-layer steps on Si(111) substrates. These Au islands are spontaneously arranged by controlling the deposition. There are three aspects to the growth of vertical GaP wires: the cosupply of TMGa and PH3, two growths at different temperatures, and a low PH3 flow rate. The grown wires are quite ordered in lines of several micrometers. Electrical measurement confirmed selective current flow at the wires and we confirmed photoluminescence from the wires. This bottom-up technique is promising for nano-hetero-device integration on Si circuits.
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81.07.Vb Quantum wires
73.63.Nm Quantum wires
68.65.La Quantum wires (patterned in quantum wells)
78.55.Cr III-V semiconductors
78.66.Fd III-V semiconductors
81.16.Dn Self-assembly

One-step synthesis and enhanced blue emission of carbon-encapsulated single-crystalline ZnSe nanoparticles

B. Y. Geng, Q. B. Du, X. W. Liu, J. Z. Ma, X. W. Wei, and L. D. Zhang

Appl. Phys. Lett. 89, 033115 (2006); http://dx.doi.org/10.1063/1.2227964 (3 pages) | Cited 7 times

Online Publication Date: 20 July 2006

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Carbon-encapsulated ZnSe nanoparticles with diameters about 50 nm were synthesized by noncatalytic one-step thermal evaporation method. The ZnSe cores have a wurtzite crystal structure. The as-synthesized products are uniform and composed of single-crystalline ZnSe nanoparticles enwrapped with polycrystalline graphite layers. The photoluminescence measurement of the carbon-encapsulated nanoparticles shows that the blue emission enhances dramatically compared with the naked ZnSe nanoparticles. This synthetic strategy might exploit a favorable route to synthesize carbon-encapsulated semiconductor nanostructures, which are potentially important for optoelectronic nanodevices.
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81.05.Dz II-VI semiconductors
78.55.Et II-VI semiconductors
81.07.Bc Nanocrystalline materials

Force-strain relation of bundles of carbon nanotubes

Tan Xiao, Yu Ren, Ping Wu, and Kin Liao

Appl. Phys. Lett. 89, 033116 (2006); http://dx.doi.org/10.1063/1.2227987 (3 pages) | Cited 5 times

Online Publication Date: 20 July 2006

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The force-strain relation and tensile strength of carbon nanotube bundles are studied based on the assumption that the tensile strength of individual carbon nanotubes (CNTs) obeys the Weibull distribution, with nonlinear stress-strain behavior. The Weibull modulus of the CNT that characterizes the dispersion of tensile strength can be estimated in terms of the maximum sustained force and the failure strain of the bundle. Bundles of single-walled carbon nanotubes (SWNTs) were subjected to tensile testing using a nanomechanical testing device. Results show that the nonlinear behavior of SWNTs does affect the force-strain relation of SWNT bundles, more apparent at large strain.
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81.40.Lm Deformation, plasticity, and creep
61.46.Fg Nanotubes
62.20.F- Deformation and plasticity
81.40.Jj Elasticity and anelasticity, stress-strain relations

Effect of gravity on the growth of vertical single-walled carbon nanotubes in a chemical vapor deposition process

C. M. Yeh, M. Y. Chen, J. S. Syu, J.-Y. Gan, and J. Hwang

Appl. Phys. Lett. 89, 033117 (2006); http://dx.doi.org/10.1063/1.2228068 (3 pages) | Cited 3 times

Online Publication Date: 20 July 2006

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Vertically aligned single-walled carbon nanotubes (SWCNTs) can be fabricated on the Co/Si(100) substrate in a gravity assisted chemical vapor deposition process. The Co/Si(100) substrate is tilted such that its surface normal points downwards in the chemical vapor deposition process. All the SWCNTs are lined up with the direction of gravity. The length of SWCNTs increases with growth time. A modified vapor-liquid-solid mechanism is proposed to explain the role of gravity in the precipitation of SWCNTs and in the lineup behavior of SWCNTs.
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81.16.-c Methods of micro- and nanofabrication and processing
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.30.Mh Solid-phase precipitation

Characterization and photoluminescence properties of aluminum borate nanorods doped with Eu

J. Lin, Y. Huang, J. Zhang, H. S. Song, E. M. Elssfah, S. J. Liu, J. J. Luo, X. X. Ding, S. R. Qi, and C. C. Tang

Appl. Phys. Lett. 89, 033118 (2006); http://dx.doi.org/10.1063/1.2234240 (3 pages) | Cited 3 times

Online Publication Date: 20 July 2006

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Aluminum borate (Al18B4O33) nanorods doped with Eu3+ and Eu2+ were synthesized via a simple calcination method. Both nanorods are of straight morphology and smooth surface, with the average diameter of ∼ 80 nm. The structural and compositional characteristics have been investigated by x-ray diffraction, infrared spectra, and various microscopy techniques. A possible growth mechanism was proposed for the synthesis of the doped Al18B4O33 nanorods. Photoluminescence measurements indicate that Al18B4O33:Eu3+ nanorods exhibit emission peaks at 590, 595, 612, and 617 nm, and Al18B4O33:Eu2+ nanorods display a broad green emission band centered at ∼ 540 nm.
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78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
78.55.Hx Other solid inorganic materials
81.07.Bc Nanocrystalline materials
61.72.up Other materials
78.30.Hv Other nonmetallic inorganics

Spin-polarized transport in magnetically assembled carbon nanotube spin valves

R. Thamankar, S. Niyogi, B. Y. Yoo, Y. W. Rheem, N. V. Myung, R. C. Haddon, and R. K. Kawakami

Appl. Phys. Lett. 89, 033119 (2006); http://dx.doi.org/10.1063/1.2221910 (3 pages) | Cited 7 times

Online Publication Date: 20 July 2006

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Spin polarized transport over 5 μm long carbon nanotubes (CNTs) is observed in magnetically assembled spin valves with electrochemically deposited ferromagnetic (FM) electrodes. An annealing procedure is developed to produce stable devices with highly transmissive FM/CNT contacts. The devices exhibit magnetoresistance (MR) with magnitudes up to 4%, and the sign of MR is consistently negative. The temperature dependence is investigated and MR is observed up to 14 K. Bias dependence is also investigated, with MR persisting up to ∼ 300 mV.
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85.70.Kh Magnetic thin film devices: magnetic heads (magnetoresistive, inductive, etc.); domain-motion devices, etc.
85.35.Kt Nanotube devices

Remotely coupled surface plasmons in a metal/insulator/Si structure perforated with periodic square hole arrays

Tzu-Hung Chuang, Ming-Wei Tsai, Yi-Tsung Chang, and Si-Chen Lee

Appl. Phys. Lett. 89, 033120 (2006); http://dx.doi.org/10.1063/1.2234290 (3 pages) | Cited 6 times

Online Publication Date: 20 July 2006

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The zero-order transmission of radiation through a metal/dielectric structure perforated with square hole arrays is strongly enhanced when incident light resonates with surface plasmons (SPs). Surprisingly, when a metal/dielectric double layer, such as Ag/SiO2, is fabricated on a silicon substrate, the Ag/Si SP mode by coupling Ag and Si across the intermediate dielectric film has been found. It is named the remotely coupled surface plasmon. The transmission intensity is investigated as a function of the intermediate SiO2 thickness. The coupling lengths between Ag and Si in order to form the Ag/Si SP mode are determined as well, and they turn out to be 500 and 130 nm for couplings through air and a SiO2 layer, respectively.
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73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
77.55.-g Dielectric thin films
78.68.+m Optical properties of surfaces
68.35.B- Structure of clean surfaces (and surface reconstruction)

Direct observation of resonant energy transfer between quantum dots of two different sizes in a single water droplet

Ling Xu, Jun Xu, Zhongyuan Ma, Wei Li, Xinfan Huang, and Kunji Chen

Appl. Phys. Lett. 89, 033121 (2006); http://dx.doi.org/10.1063/1.2226980 (3 pages) | Cited 8 times

Online Publication Date: 20 July 2006

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Water soluble CdTe nanocrystals (NCs) of two different sizes capped by thioglycolic acid were synthesized and were dispersed in pure water. We have observed that the emission color of CdTe NCs has been changed in a single droplet of water during the evaporation of the solvent. This is attributed to Förster resonance energy transfer between CdTe NCs, when their concentration becomes high enough to ensure close proximity. By combining our results of photoluminescence with quantitative analysis we conclude that the coupling between different sized CdTe NCs via long-range dipole-dipole interactions was enhanced in aqueous solution due to Brownian motion.
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78.67.Hc Quantum dots
78.55.Et II-VI semiconductors
64.70.F- Liquid-vapor transitions

Multibit memories using a structure of SiO2/partially oxidized amorphous Si/HfO2

Sangjin Park, Young-Kwan Cha, Daigil Cha, Youngsoo Park, In-Kyeong Yoo, Jung-Hyun Lee, Kwang Soo Seol, and Suk-Ho Choi

Appl. Phys. Lett. 89, 033122 (2006); http://dx.doi.org/10.1063/1.2219999 (3 pages) | Cited 4 times

Online Publication Date: 21 July 2006

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Memory capacitors with a structure of SiO2/partially oxidized amorphous Si (a-Si)/HfO2 have been prepared by sequential processes: atomic layer deposition (ALD) of 6 nm a-Si on 3.5 nm SiO2, thermal oxidation at 900 °C, and another ALD of 12 nm HfO2. The memory devices offer hybrid type of charge memory: the interface states of partially oxidized a-Si/SiO2 tend to act as hole traps, resulting in a negative shift of flatband voltage in capacitance-voltage (C-V) curve, and the partially oxidized a-Si/HfO2 interface has dominantly electron-trap centers, leading to a positive voltage shift. By this hybrid effect, the memory window in C-V curve is observed to be enlarged enough to realize four-level (2 bit) memories, which is demonstrated through measurements of program/erase speeds and charge-loss rates.
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84.30.Sk Pulse and digital circuits
84.32.Tt Capacitors
85.40.Sz Deposition technology

Extreme undercooling (down to 90 K) of liquid metal nanoparticles

G. B. Parravicini, A. Stella, P. Ghigna, G. Spinolo, A. Migliori, F. d’Acapito, and R. Kofman

Appl. Phys. Lett. 89, 033123 (2006); http://dx.doi.org/10.1063/1.2221395 (3 pages) | Cited 4 times

Online Publication Date: 21 July 2006

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Low-melting-point metal nanoparticles show remarkable undercoolings: exceptional values ΔT/Tm ≅ 0.5 were previously reported for confined Ga droplets in the 100–1000 nm range. This was considered a characteristic limiting temperature for Ga. We here give evidence that Ga nanoparticles in the 3–15 nm range can be undercooled at least down to 90 K (ΔT/Tm ≥ 0.7) without crystallization. Since computations and experiments on clusters with <50  atoms show on the contrary the signatures of melting at temperatures well above the bulk value, the result is particularly relevant in stressing the importance of interfacial and finite-size effects on the thermodynamics of the nanoscale.
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61.25.Mv Liquid metals and alloys
64.70.D- Solid-liquid transitions
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