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6 Dec 2004

Volume 85, Issue 23, pp. 5499-5791

Issue Cover Spotlight Figure

Appl. Phys. Lett. 85, 5694 (2004); http://dx.doi.org/10.1063/1.1828575 (3 pages)

M. Y. Shen, C. H. Crouch, J. E. Carey, and E. Mazur
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Growth and morphology of 0.80 eV photoemitting indium nitride nanowires

M. C. Johnson, C. J. Lee, E. D. Bourret-Courchesne, S. L. Konsek, S. Aloni, W. Q. Han, and A. Zettl

Appl. Phys. Lett. 85, 5670 (2004); http://dx.doi.org/10.1063/1.1831563 (3 pages) | Cited 36 times

Online Publication Date: 8 December 2004

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InN nanowires with high efficiency photoluminescence emission at 0.80 eV are reported. InN nanowires were synthesized via a vapor solid growth mechanism from high purity indium metal and ammonia. The products consist of only hexagonal wurtzite phase InN. Scanning electron microscopy showed wires with diameters of 50–100 nm and having fairly smooth morphologies. High-resolution transmission electron microscopy revealed high quality, single crystal InN nanowires which grew in the 〈0001〉 direction.
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81.07.Bc Nanocrystalline materials
81.05.Ea III-V semiconductors
61.46.-w Structure of nanoscale materials
68.35.B- Structure of clean surfaces (and surface reconstruction)
78.55.Cr III-V semiconductors
78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
68.37.Hk Scanning electron microscopy (SEM) (including EBIC)
68.37.Lp Transmission electron microscopy (TEM)

Universal shapes of self-organized semiconductor quantum dots: Striking similarities between InAs∕GaAs(001) and Ge∕Si(001)

G. Costantini, A. Rastelli, C. Manzano, R. Songmuang, O. G. Schmidt, K. Kern, and H. von Känel

Appl. Phys. Lett. 85, 5673 (2004); http://dx.doi.org/10.1063/1.1829164 (3 pages) | Cited 51 times

Online Publication Date: 8 December 2004

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The model systems for self-organized quantum dots formed from elemental and compound semiconductors, namely Ge grown on Si(001) and InAs on GaAs(001), are comparatively studied by scanning tunneling microscopy. It is shown that in both material combinations only two well-defined families of faceted and defect-free nanocrystals exist (and coexist). These three-dimensional islands, pyramids, and domes show common morphological characteristics, independent of the specific material system. A universal behavior is further demonstrated in the capping-passivation process that turns the nanocrystals in true quantum dots.
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68.65.Hb Quantum dots (patterned in quantum wells)
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)

Effect of the polar surface on GaN nanostructure morphology and growth orientation

C. Y. Nam, D. Tham, and J. E. Fischer

Appl. Phys. Lett. 85, 5676 (2004); http://dx.doi.org/10.1063/1.1829780 (3 pages) | Cited 34 times

Online Publication Date: 8 December 2004

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Wurtzite gallium nitride nanostructures were grown by thermal reaction of gallium oxide and ammonia. The resulting morphology varied depending on ammonia flow rate. At 75 sccm only nanowires were obtained, while polyhedral crystals and nanobelts were observed at 175 sccm. Scanning electron microscopy and transmission electron microscopy revealed both thin smooth and thick corrugated nanowires. The growth orientations of most of the smooth ones, as well as the nanobelts, were perpendicular to the c axis (〈0001〉), while the corrugated nanowires and the large polyhedra grew parallel to 〈0001〉. We propose a model to explain these variations of morphology and growth orientation in terms of the Ga∕N ratio and the different characteristic length of {0001} polar surface in the different nanostructures.
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81.07.Bc Nanocrystalline materials
81.05.Ea III-V semiconductors
81.15.Kk Vapor phase epitaxy; growth from vapor phase
61.46.-w Structure of nanoscale materials
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.37.Hk Scanning electron microscopy (SEM) (including EBIC)
68.37.Lp Transmission electron microscopy (TEM)

Super-miniature x-ray tube

S. Senda, Y. Sakai, Y. Mizuta, S. Kita, and F. Okuyama

Appl. Phys. Lett. 85, 5679 (2004); http://dx.doi.org/10.1063/1.1832733 (3 pages) | Cited 38 times

Online Publication Date: 8 December 2004

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A transmission x-ray tube super-miniature in size is described. The x-ray tube is 5 mm in diameter, and comprised of a built-in electron-emitter assembly and a grounded planar target. The key component of the emitter assembly is a Kovar pipe 2 mm in diameter, inside which carbon nanofibers aligned on an electro-polished molybdenum tip are loaded to serve as the electron emitter. This type of electron emitter is highly robust in non-ultrahigh vacuum, continuing to field emit electrons for 100 h or longer at pressures in the 10−5 Pa region. This x-ray tube provides clear x-ray images.
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07.85.Fv X- and γ-ray sources, mirrors, gratings, and detectors

Field-emission from long SnO2 nanobelt arrays

Y. J. Chen, Q. H. Li, Y. X. Liang, T. H. Wang, Q. Zhao, and D. P. Yu

Appl. Phys. Lett. 85, 5682 (2004); http://dx.doi.org/10.1063/1.1833557 (3 pages) | Cited 65 times

Online Publication Date: 8 December 2004

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We report on field emission from SnO2 nanobelt arrays with the length of about 90 μm grown on silicon substrates. The turn-on field of the nanobelt arrays at the current density of 1 μA∕cm2, is 4.5, 3.0, 2.4, and 2.3 V∕μm as the distance between anode and cathode (d) is 0.1, 0.2, 0.35, and 0.5 mm, respectively. The current density rapidly reaches 2.1 mA∕cm2 at the electrical field of 4.4 V∕μm at d=0.35 mm. The current density is higher than or comparable to those of the carbon nanotubes and other one-dimensional nanostructured materials. We also discuss the mechanism of high current densities and estimate the enhancement factor according to both the Fowler–Nordheim law and the reported model on micrometer-long of carbon nanotubes.
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79.70.+q Field emission, ionization, evaporation, and desorption
61.46.-w Structure of nanoscale materials

Quantitative investigations of optical absorption in InAs∕InP (311)B quantum dots emitting at 1.55 μm wavelength

C. Cornet, C. Labbé, H. Folliot, N. Bertru, O. Dehaese, J. Even, A. Le Corre, C. Paranthoen, C. Platz, and S. Loualiche

Appl. Phys. Lett. 85, 5685 (2004); http://dx.doi.org/10.1063/1.1832750 (3 pages) | Cited 18 times

Online Publication Date: 8 December 2004

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We have measured the absorbance of InAs∕InP quantum dots emitting at 1.55 μm wavelength with a Fourier transform infrared spectrometer. The sample is a 12-stack InAs quantum dots grown by molecular beam epitaxy on (311)B InP oriented substrate. The absorption coefficient is estimated at 4400 cm−1 for 3 nm height and 5×1010 cm−2 surface density. The absorption of the quantum dot structures is found to be similar to quantum well structures when the number of atoms considered absorbing is equivalent. The Stokes shift between the absorbance and the photoluminescence spectra is also investigated at 4 and 293 K.
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81.05.Ea III-V semiconductors
78.67.Hc Quantum dots
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
42.55.Px Semiconductor lasers; laser diodes
81.07.Ta Quantum dots
78.55.Cr III-V semiconductors

Photoluminescence mapping study of gettering effect of polycrystalline Si on ultrathin silicon-on-insulator

Z. Q. Li, M. Tajima, N. Kitai, H. Yoshida, and S. Kishino

Appl. Phys. Lett. 85, 5688 (2004); http://dx.doi.org/10.1063/1.1831556 (3 pages) | Cited 1 time

Online Publication Date: 8 December 2004

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High-resolution photoluminescence (PL) mapping measurement was performed to study the gettering effect of polycrystalline Si on ultrathin silicon-on-insulator (SOI) wafers. A 150-mm-diam Unibond SOI wafer was patterned and partially gettered by polycrystalline Si process at 600 °C for 1 h. Then the wafer was annealed in H2 atmosphere at 400 °C for 1 h. PL mapping clearly demonstrated the difference between the gettered and ungettered parts, before and after H2 annealing. Before H2 annealing, almost no variation was obvious between the gettered and ungettered parts. After H2 annealing, however, we found the PL intensity was substantially increased, and the gettered area gave 24.7% higher PL intensity than the ungettered part. This coincided with the results of charge pumping measurements, which indicated a negligible difference of the interface trap density for the two areas before H2 annealing, while remarkable decrease of this density for the gettered region after H2 annealing. H2 annealing thus decreased the interface trap density, and made the gettering effect more obvious. This result indicated that PL mapping is effective and sensitive in characterizing the gettering effect of ultrathin SOI structures.
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78.66.Li Other semiconductors
78.55.Hx Other solid inorganic materials
61.72.Yx Interaction between different crystal defects; gettering effect
61.72.Cc Kinetics of defect formation and annealing

Parallel writing on zirconium nitride thin films by local oxidation nanolithography

N. Farkas, J. R. Comer, G. Zhang, E. A. Evans, R. D. Ramsier, S. Wight, and J. A. Dagata

Appl. Phys. Lett. 85, 5691 (2004); http://dx.doi.org/10.1063/1.1833569 (3 pages) | Cited 12 times

Online Publication Date: 8 December 2004

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Parallel pattern transfer of submicrometer-scale oxide features onto zirconium nitride thin films is reported. The oxidation reaction was verified by Auger microprobe analysis and secondary ion mass spectrometry. Oxide features of ∼70 nm in height can be formed and selectively etched in a dilute aqueous hydrogen fluoride solution. This provides an interesting route to potential new applications for high-melting point, biocompatible surfaces that possess small feature sizes with controlled geometries.
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81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)
68.55.-a Thin film structure and morphology
81.16.Nd Micro- and nanolithography
81.65.Mq Oxidation
81.65.Cf Surface cleaning, etching, patterning
81.16.Rf Micro- and nanoscale pattern formation
81.16.Pr Micro- and nano-oxidation
68.37.Xy Scanning Auger microscopy, photoelectron microscopy

Femtosecond laser-induced formation of submicrometer spikes on silicon in water

M. Y. Shen, C. H. Crouch, J. E. Carey, and E. Mazur

Appl. Phys. Lett. 85, 5694 (2004); http://dx.doi.org/10.1063/1.1828575 (3 pages) | Cited 76 times

Online Publication Date: 8 December 2004

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We fabricate submicrometer silicon spikes by irradiating a silicon surface that is submerged in water with 400 nm, 100 fs laser pulses. These spikes are less than a micrometer tall and about 200 nm wide—one to two orders of magnitude smaller than the microspikes formed by laser irradiation of silicon in gases or vacuum. Scanning electron micrographs of the surface show that the formation of the spikes involves a combination of capillary waves on the molten silicon surface and laser-induced etching of silicon. Chemical analysis and scanning electron microscopy of the spikes show that they are composed of silicon with a 20-nm-thick surface oxide layer.
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81.65.Cf Surface cleaning, etching, patterning
79.20.Ds Laser-beam impact phenomena
71.55.Cn Elemental semiconductors
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
61.82.Fk Semiconductors
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.37.Hk Scanning electron microscopy (SEM) (including EBIC)

Capping process of InAs∕GaAs quantum dots studied by cross-sectional scanning tunneling microscopy

Q. Gong, P. Offermans, R. Nötzel, P. M. Koenraad, and J. H. Wolter

Appl. Phys. Lett. 85, 5697 (2004); http://dx.doi.org/10.1063/1.1831564 (3 pages) | Cited 11 times

Online Publication Date: 8 December 2004

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The capping process of self-assembled InAs quantum dots (QDs) grown on GaAs(100) substrates by molecular-beam epitaxy is studied by cross-sectional scanning tunneling microscopy. GaAs capping at 500 °C causes leveling of the QDs which is completely suppressed by decreasing the growth temperature to 300 °C. At elevated temperature the QD leveling is driven in the initial stage of the GaAs capping process while it is quenched during continued overgrowth when the QDs become buried. For common GaAs growth rates, both phenomena take place on a similar time scale. Therefore, the size and shape of buried InAs QDs are determined by a delicate interplay between driving and quenching of the QD leveling during capping which is controlled by the GaAs growth rate and growth temperature.
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81.07.Ta Quantum dots
81.05.Ea III-V semiconductors
68.65.Hb Quantum dots (patterned in quantum wells)
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
81.40.Gh Other heat and thermomechanical treatments
68.35.B- Structure of clean surfaces (and surface reconstruction)

Ordered growth of germanium hut islands on Si (001) molecular bonded substrates

V. Poydenot, R. Dujardin, J. L. Rouvière, A. Barski, and F. Fournel

Appl. Phys. Lett. 85, 5700 (2004); http://dx.doi.org/10.1063/1.1829795 (3 pages) | Cited 3 times

Online Publication Date: 8 December 2004

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Ordered germanium hut islands are grown by molecular-beam epitaxy on high twist angle molecular bonded silicon (001) substrates (twist angle higher than 20°). We show that the growth organization is induced by an array of interfacial tilt dislocations. Plan-view transmission electron microscopy and atomic force microscopy observations show that the orientation and period of the tilt dislocation array determine the orientation, period, and length of elongated germanium hut islands. The strain field generated by an array of tilt dislocations is proposed as the driving force of the reported organization.
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81.05.Cy Elemental semiconductors
68.55.A- Nucleation and growth
68.55.-a Thin film structure and morphology
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
68.35.Gy Mechanical properties; surface strains
68.35.B- Structure of clean surfaces (and surface reconstruction)
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.60.Bs Mechanical and acoustical properties
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
68.37.Ps Atomic force microscopy (AFM)
68.37.Lp Transmission electron microscopy (TEM)

Family behavior of the optical transition energies in single-wall carbon nanotubes of smaller diameters

Ge. G. Samsonidze, R. Saito, N. Kobayashi, A. Grüneis, J. Jiang, A. Jorio, S. G. Chou, G. Dresselhaus, and M. S. Dresselhaus

Appl. Phys. Lett. 85, 5703 (2004); http://dx.doi.org/10.1063/1.1829160 (3 pages) | Cited 85 times

Online Publication Date: 8 December 2004

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Using the extended tight-binding model that allows bond lengths and angles to vary, the optical transition energies Eii in single-wall carbon nanotubes are calculated as a function of inverse tube diameter. After geometrical structure optimization, the 2n+m=constant family behavior observed in photoluminescence (PL) experiments is obtained, and detailed agreement between the calculations and PL experiments is achieved after including many-body corrections.
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73.22.-f Electronic structure of nanoscale materials and related systems
78.67.Ch Nanotubes
61.50.Lt Crystal binding; cohesive energy
71.15.Ap Basis sets (LCAO, plane-wave, APW, etc.) and related methodology (scattering methods, ASA, linearized methods, etc.)
61.46.-w Structure of nanoscale materials
78.55.Hx Other solid inorganic materials

Charge transport in a CoPt3 nanocrystal microwire

P. Beecher, G. De Marzi, A. J. Quinn, G. Redmond, E. V. Shevchenko, and H. Weller

Appl. Phys. Lett. 85, 5706 (2004); http://dx.doi.org/10.1063/1.1830684 (3 pages) | Cited 2 times

Online Publication Date: 8 December 2004

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The electrical characteristics of single CoPt3 nanocrystal microwires formed by magnetic field-directed growth from colloidal solutions are presented. The wires comprise disordered assemblies of discrete nanocrystals, separated from each other by protective organic ligand shells. Electrical data indicate that the activated charge transport properties of the wires are determined by the nanocrystal charging energy, governed by the size and capacitance of the individual nanocrystals. Focused ion beam-assisted deposition of Pt metal at the wire-electrode junctions is employed to optimize the wire-electrode contacts, whilst maintaining the nanocrystal-dominated transport characteristics of these one-dimensional nanocrystal structures.
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73.63.Rt Nanoscale contacts
73.40.Cg Contact resistance, contact potential
61.46.-w Structure of nanoscale materials
81.15.Jj Ion and electron beam-assisted deposition; ion plating

Temperature profile and pressure effect on the growth of silicon nanowires

Sau-Wan Cheng and Ho-Fai Cheung

Appl. Phys. Lett. 85, 5709 (2004); http://dx.doi.org/10.1063/1.1830683 (3 pages) | Cited 7 times

Online Publication Date: 8 December 2004

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The excess temperature at the tip of silicon nanowires during their growth is calculated and found to be generally low. Therefore the special adhesive property of the tip cannot be explained by the excess temperature. The effect of surface tension is analyzed and we found that it cannot cause a significant lowering of melting point at the tip. Based on the charge-assisted mechanism proposed earlier by us, we note that charge accumulation at the tip results in a strong negative pressure. We propose that this is the key force driving the nanowire to have only one-dimensional growth.
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68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
68.03.Cd Surface tension and related phenomena
81.07.-b Nanoscale materials and structures: fabrication and characterization
81.05.Cy Elemental semiconductors
64.70.D- Solid-liquid transitions
68.35.Np Adhesion
66.70.-f Nonelectronic thermal conduction and heat-pulse propagation in solids; thermal waves
61.46.-w Structure of nanoscale materials

Structure and optical properties of Au-polyimide nanocomposite films prepared by ion implantation

G. Maggioni, A. Vomiero, S. Carturan, C. Scian, G. Mattei, M. Bazzan, C. de Julián Fernández, P. Mazzoldi, A. Quaranta, and G. Della Mea

Appl. Phys. Lett. 85, 5712 (2004); http://dx.doi.org/10.1063/1.1829390 (3 pages) | Cited 17 times

Online Publication Date: 8 December 2004

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Au-polyimide nanocomposites have been synthesized by implanting different doses of Au+ ions in 100 nm thick films of pyromellitic dianhydride-4,4′ oxydianiline polyimide, prepared by glow discharge vapor deposition polymerization. Unambiguous evidence of Au nanoclusters growth is found only at the highest implantation doses (5×1016 Au+∕cm2). Structural, compositional, and optical characterizations show that the implantation induces the compactation of the initial film due to H and C loss. The resulting structure is a composite containing 2–3 nm gold nanoparticles arranged in a layer of about 40 nm and, just beneath the sample surface, a 15 nm thick carbon-rich layer. Optical simulations suggest the presence of a gold-carbon core-shell structure in the nanoparticles.
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82.35.Np Nanoparticles in polymers
61.46.-w Structure of nanoscale materials
61.41.+e Polymers, elastomers, and plastics
68.55.-a Thin film structure and morphology
68.55.A- Nucleation and growth
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
78.66.Bz Metals and metallic alloys
78.66.Qn Polymers; organic compounds
61.72.up Other materials
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
78.40.Kc Metals, semimetals, and alloys
78.40.Pg Disordered solids
78.35.+c Brillouin and Rayleigh scattering; other light scattering
78.30.Er Solid metals and alloys
68.37.Lp Transmission electron microscopy (TEM)

Localization of excitons in disordered quantum wires probed by single-photon correlation spectroscopy

A. Malko, M. H. Baier, E. Pelucchi, D. Y. Oberli, K. Leifer, D. Chek-al-kar, and E. Kapon

Appl. Phys. Lett. 85, 5715 (2004); http://dx.doi.org/10.1063/1.1830689 (3 pages) | Cited 5 times

Online Publication Date: 8 December 2004

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Single-photon correlation and microphotoluminescence spectroscopy are employed to characterize the emission from disordered InGaAs∕AlGaAs quantum wires grown in inverted tetrahedral pyramids. Recombinations of neutral and charged excitons, localized by wire potential fluctuations, are identified. Antibunched photon emission is observed from both excitonic species that are shown to recombine at the same disordered wire site. This demonstrates the use of single-photon correlation spectroscopy for obtaining spatial information on optical processes in nanostructures.
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73.21.Hb Quantum wires
81.05.Ea III-V semiconductors
73.63.Nm Quantum wires
78.67.Lt Quantum wires
73.22.Lp Collective excitations
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
79.60.Ht Disordered structures
78.55.Cr III-V semiconductors
79.60.Bm Clean metal, semiconductor, and insulator surfaces
79.60.Jv Interfaces; heterostructures; nanostructures

Photoluminescence studies of GaN nanorods on Si (111) substrates grown by molecular-beam epitaxy

Y. S. Park, C. M. Park, D. J. Fu, T. W. Kang, and J. E. Oh

Appl. Phys. Lett. 85, 5718 (2004); http://dx.doi.org/10.1063/1.1832739 (3 pages) | Cited 45 times

Online Publication Date: 8 December 2004

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We have investigated the optical properties of dislocation-free vertical GaN nanorods grown on (111) Si substrates by radio-frequency plasma-assisted molecular-beam epitaxy. The hexagonal shape nanorods with lateral diameters from 80 to 190 nm are obtained. They are fully relaxed and have a very good crystal quality characterized by extremely strong and narrow photoluminescence excitonic lines near 3.47 eV. Three distinct features are observed in photoluminescence. First, free exciton transition is observed at 3.477 eV for GaN nanorods of decreased diameter. Second, the photoluminescence spectra show an abnormal behavior with increasing temperature. The third feature is the size effect in that the PL peak energies are blueshifted with decreasing diameter of the GaN nanorod. The activation energy of the free exciton for the GaN nanorods with different diameters was evaluated.
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78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
73.22.Lp Collective excitations
78.55.Cr III-V semiconductors

Enhanced luminescence from electron–hole droplets in silicon nanolayers

Satoshi Nihonyanagi and Yoshihiko Kanemitsu

Appl. Phys. Lett. 85, 5721 (2004); http://dx.doi.org/10.1063/1.1829161 (3 pages) | Cited 5 times

Online Publication Date: 8 December 2004

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We have studied photoluminescence (PL) from the condensed phase in silicon-on-insulator samples with different Si layer thickness from 50 to 340 nm. Two major PL bands are observed at low temperatures, originating from free excitons (FE) and electron–hole droplets (EHD). It is found that with an increase of the excitation intensity the EHD PL shows a linear increase in the 50-nm-thick layer while a superlinear increase in the 340-nm-thick layer. The intensity ratio of the EHD PL to the FE PL in the 50-nm-thick layer is much larger than that in the 340-nm-thick layer under the same experimental conditions. The luminescence from the EHD is enhanced in thin Si nanolayers. These results suggest that highly dense electrons and holes are formed in the Si nanolayer and the interfaces act as the nucleation center of the EHD.
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78.66.Db Elemental semiconductors and insulators
78.55.Ap Elemental semiconductors
71.35.Ee Electron-hole drops and electron-hole plasma
73.22.Lp Collective excitations

Highly nonlinear contact interaction and dynamic energy dissipation by forest of carbon nanotubes

Chiara Daraio, Vitali F. Nesterenko, and Sungho Jin

Appl. Phys. Lett. 85, 5724 (2004); http://dx.doi.org/10.1063/1.1829778 (3 pages) | Cited 15 times

Online Publication Date: 8 December 2004

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Mechanical response and energy dissipation of an array of carbon nanotubes under high-strain rate deformation was studied using a simple drop-ball test with the measurement of the dynamic force between the ball and forest of nanotubes. This convenient process allows extracting force–displacement curves and evaluating dissipated energy by the nanotubes. The contact force exhibits a strongly nonlinear dependence on displacement being fundamentally different than the Hertz law. The forest of vertically aligned nanotubes may be used as a strongly nonlinear spring in discrete systems for monitoring signal propagation speed, and as a microstructure for localized energy absorption.
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81.07.De Nanotubes
81.70.Bt Mechanical testing, impact tests, static and dynamic loads
81.40.Jj Elasticity and anelasticity, stress-strain relations
62.25.-g Mechanical properties of nanoscale systems
62.20.D- Elasticity
62.20.F- Deformation and plasticity

Scanning-tunneling-microscopy-based nanolithography of diamond-like carbon films

Thomas Mühl

Appl. Phys. Lett. 85, 5727 (2004); http://dx.doi.org/10.1063/1.1831567 (3 pages) | Cited 11 times

Online Publication Date: 8 December 2004

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We demonstrate an approach for nanometer-scale lithography of diamond-like carbon films employing a local electron injection from a scanning tunneling microscope tip under ultrahigh-vacuum conditions. The electrons induce a graphitization of the tetrahedrally bound carbon. With this technique, complex patterns of conducting lines and dots smaller than 10 nm can be written. Tunneling spectroscopy and conductive force microscopy were used to further characterize the carbon nanostructures.
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81.05.U- Carbon/carbon-based materials
68.55.-a Thin film structure and morphology
81.16.Nd Micro- and nanolithography
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
61.43.Er Other amorphous solids
68.37.Ps Atomic force microscopy (AFM)
73.61.Ng Insulators
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths

Nanotransfer printing by use of noncovalent surface forces: Applications to thin-film transistors that use single-walled carbon nanotube networks and semiconducting polymers

Seung-Hyun Hur, Dahl-Young Khang, Coskun Kocabas, and John A. Rogers

Appl. Phys. Lett. 85, 5730 (2004); http://dx.doi.org/10.1063/1.1829774 (3 pages) | Cited 83 times

Online Publication Date: 8 December 2004

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We report a purely additive nanotransfer printing process that uses noncovalent surface forces to guide the transfer of thin metal films from low-energy surfaces of high-resolution stamps to a variety of substrates. Structures with dimensions as small as a few hundred nanometers, with edge roughness as small as 10 nm are demonstrated. Metal multilayer stacks patterned in this way have electrical resistances that are the same as those formed by evaporation and conventional lithography. Thin-film transistors that use source/drain electrodes printed directly onto thin films of the semiconducting polymer regioregular polythiophene and networks of single-walled carbon nanotubes exhibit device mobilities and on/off ratios that are comparable to or higher than those of devices fabricated using standard methods.
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85.30.Tv Field effect devices
81.16.Nd Micro- and nanolithography
68.35.B- Structure of clean surfaces (and surface reconstruction)
73.61.Ph Polymers; organic compounds
73.63.Fg Nanotubes

Surfactant free fabrication of polyimide nanoparticles

J. Y. Xiong, X. Y. Liu, S. B. Chen, and T. S. Chung

Appl. Phys. Lett. 85, 5733 (2004); http://dx.doi.org/10.1063/1.1828598 (3 pages) | Cited 4 times

Online Publication Date: 8 December 2004

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Polyimide nanoparticles are fabricated using a combined liquid–liquid phase separation and solvent/nonsolvent mixing technology. This technology allows us to produce stable polyimide nanoparticles with tunable size without any surfactants. Selective solvation and electron pair donor/electron pair acceptor interaction are employed to stabilize nanoparticles. The formation of polyimide nanoparticles is governed by a nucleation-dominated process and therefore the particle size is controlled by the nucleation rate. A very high level of supersaturation can be attained under the intensive local motions induced by ultrasound, resulting in a very high nucleation rate. This effect is found extremely useful in the fabrication of sub-50-nm polyimide nanoparticles.
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81.05.Lg Polymers and plastics; rubber; synthetic and natural fibers; organometallic and organic materials
61.41.+e Polymers, elastomers, and plastics
61.46.-w Structure of nanoscale materials
64.60.Q- Nucleation
64.75.-g Phase equilibria
82.30.Nr Association, addition, insertion, cluster formation
64.70.Ja Liquid-liquid transitions
81.20.-n Methods of materials synthesis and materials processing

Methyl monolayers suppress mechanical energy dissipation in micromechanical silicon resonators

Yu Wang, Joshua A. Henry, Debodhonyaa Sengupta, and Melissa A. Hines

Appl. Phys. Lett. 85, 5736 (2004); http://dx.doi.org/10.1063/1.1832735 (3 pages) | Cited 8 times

Online Publication Date: 8 December 2004

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The quality factor and long-term stability of megahertz-range micromechanical silicon resonators can be significantly improved by a methyl monolayer directly bonded to the silicon surface. Mechanical energy dissipation in functionalized resonators is shown to be a sensitive function of surface chemistry. At least 18% and 41% of the dissipation in H-terminated and long-chain alkyl-terminated resonators, respectively, is surface related. Surface-induced dissipation is poorly correlated with the mechanical properties of the terminating layer, but may be related to the surface defect density.
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85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices
68.47.Pe Langmuir-Blodgett films on solids; polymers on surfaces; biological molecules on surfaces
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
07.10.Cm Micromechanical devices and systems

In situ observation of field emissions from an individual carbon nanotube by Lorenz microscopy

T. Fujieda, K. Hidaka, M. Hayashibara, T. Kamino, H. Matsumoto, Y. Ose, H. Abe, T. Shimizu, and H. Tokumoto

Appl. Phys. Lett. 85, 5739 (2004); http://dx.doi.org/10.1063/1.1834713 (3 pages) | Cited 9 times

Online Publication Date: 8 December 2004

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In situ observation of field emissions from an individual carbon nanotube (CNT) was performed by Lorenz microscopy. A bright spot appeared by Lorenz microscopy at the end of the CNT tip during field emission. The bright spot is assumed to be related to the emission site on the CNT. A drastic fluctuation was observed in the emission current above a few tens of microamperes, which was closely related to structural changes at the tip of the CNT. The layers of the CNT were peeled off and they worked as a second emission site by concentration of the electric field.
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79.70.+q Field emission, ionization, evaporation, and desorption
61.46.-w Structure of nanoscale materials

Experimental and theoretical studies on the structure of N-doped carbon nanotubes: Possibility of intercalated molecular N2

Hyun Chul Choi, Seung Yong Bae, Jeunghee Park, Kwanyong Seo, Changwook Kim, Bongsoo Kim, Ha Jin Song, and Hyun-Joon Shin

Appl. Phys. Lett. 85, 5742 (2004); http://dx.doi.org/10.1063/1.1835994 (3 pages) | Cited 30 times

Online Publication Date: 8 December 2004

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The concentration distribution and electronic structure of N atoms doped in multiwalled banboo-like carbon nanotubes (CNTs) are examined by photon energy-dependent x-ray photoelectron spectroscopy and x-ray absorption near edge structure. The inner part of the nanotube wall has a higher N concentration and contains molecular N2 presumably intercalated between the graphite layers. These results are supported by the self-consistent charge-density-functional-based tight-binding calculation of double-walled CNTs, showing that the intercalation of N2 is energetically possible and the graphite-like N structure conformer becomes more stable when the inner wall is more heavily doped.
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73.22.-f Electronic structure of nanoscale materials and related systems
79.60.Bm Clean metal, semiconductor, and insulator surfaces
78.70.Dm X-ray absorption spectra
71.15.Ap Basis sets (LCAO, plane-wave, APW, etc.) and related methodology (scattering methods, ASA, linearized methods, etc.)
71.15.Mb Density functional theory, local density approximation, gradient and other corrections
61.46.-w Structure of nanoscale materials
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