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3 Jun 2002

Volume 80, Issue 22, pp. 4085-4270

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Molecular patterning through high-resolution polymethylmethacrylate masks

Qingling Hang, Yuliang Wang, Marya Lieberman, and Gary H. Bernstein

Appl. Phys. Lett. 80, 4220 (2002); http://dx.doi.org/10.1063/1.1481784 (3 pages) | Cited 11 times

Online Publication Date: 23 May 2002

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Electron beam lithography was used to make nanometer trenches in thin polymethylmethacrylate (PMMA). After development, the wafers were dipped in an aqueous solution of the Creutz–Taube ion [(NH3)5Ru(pyrazine)Ru(NH3)5](o-toluenesulphonate)5 (CT5), and the PMMA was removed with acetone or dichloromethane. Atomic force microscopy and x-ray photoelectron spectroscopy were used to investigate the surface characteristics of wafers after dissolution of the PMMA and to confirm the binding of a monolayer of CT5 molecules on the wafer within the areas delimited by the PMMA trenches. This masking technique has so far been demonstrated to pattern 35 nm lines of a monolayer of CT5 molecules on silicon dioxide. © 2002 American Institute of Physics.
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85.65.+h Molecular electronic devices
81.16.Nd Micro- and nanolithography
85.40.Hp Lithography, masks and pattern transfer

Size-dependent oxidation of hydrogenated silicon clusters

R. Q. Zhang, W. C. Lu, and S. T. Lee

Appl. Phys. Lett. 80, 4223 (2002); http://dx.doi.org/10.1063/1.1473876 (3 pages) | Cited 2 times

Online Publication Date: 23 May 2002

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We show explicitly the size-dependent chemical reactivity of hydrogenated silicon clusters reacting with water. A unique trend of decreasing reactivity with decreasing cluster size has been deduced from reaction energetics, frontier orbital analysis, and chemical reaction rates determined by the transition state theory in conjunction with ab initio calculations at Hartree–Fock and Møller–Plesset perturbation levels of theory, for water reaction with both dihydride and trihydride silicon configurations. This study indicates the possibility of fabricating stable hydrogenated silicon structures by reducing their size to nanometers. © 2002 American Institute of Physics.
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81.05.Cy Elemental semiconductors
81.65.Mq Oxidation
61.46.-w Structure of nanoscale materials
81.07.Bc Nanocrystalline materials

Template-catalyst-free growth of highly ordered boron nanowire arrays

L. M. Cao, K. Hahn, C. Scheu, M. Rühle, Y. Q. Wang, Z. Zhang, C. X. Gao, Y. C. Li, X. Y. Zhang, M. He, L. L. Sun, and W. K. Wang

Appl. Phys. Lett. 80, 4226 (2002); http://dx.doi.org/10.1063/1.1483131 (3 pages) | Cited 16 times

Online Publication Date: 23 May 2002

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Well-aligned boron nanowire arrays were grown vertically on silicon substrates over areas up to several tens of square centimeters using radio-frequency magnetron sputtering of highly pure boron. During growth and self-assembly of boron nanowire arrays, no template or catalyst was needed. The morphology, structure, and composition of the self-organized boron nanowires were characterized in detail using scanning electron microscopy, transmission electron microscopy, and electron energy-loss spectroscopy. Our results might provide insight into the controllable formation of a wide variety of ordered nanostructures with advanced properties. © 2002 American Institute of Physics.
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61.46.-w Structure of nanoscale materials
81.15.Cd Deposition by sputtering
68.65.La Quantum wires (patterned in quantum wells)
81.16.Dn Self-assembly
73.63.Fg Nanotubes
81.07.De Nanotubes
68.37.Hk Scanning electron microscopy (SEM) (including EBIC)
68.37.Lp Transmission electron microscopy (TEM)
79.20.Uv Electron energy loss spectroscopy

Spin splitting of the electron ground states of InAs quantum dots

G. Medeiros-Ribeiro, M. V. B. Pinheiro, V. L. Pimentel, and E. Marega

Appl. Phys. Lett. 80, 4229 (2002); http://dx.doi.org/10.1063/1.1483112 (3 pages) | Cited 26 times

Online Publication Date: 23 May 2002

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Here, we present results on the spin splitting of electrons in the ground state of InAs self-assembled quantum dots (QDs). The spin splitting is assessed by capacitance spectroscopy, which allows direct measurement of the electronic g-factor modulus. By applying the magnetic field parallel to the [001], [110], and [1math0] crystallographic directions, we found that for magnetic fields below 5 T the g factor depends on the orientation, reflecting the QD anisotropy. For higher fields, the g factor does not exhibit the same degree of anisotropy, indicating a compression of the wave function inside the QD along the [001] direction, and consequently, a dependence on the magnitude of the applied field. © 2002 American Institute of Physics.
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73.21.La Quantum dots
71.70.-d Level splitting and interactions

Metalorganic vapor-phase epitaxial growth of vertically well-aligned ZnO nanorods

W. I. Park, D. H. Kim, S.-W. Jung, and Gyu-Chul Yi

Appl. Phys. Lett. 80, 4232 (2002); http://dx.doi.org/10.1063/1.1482800 (3 pages) | Cited 453 times

Online Publication Date: 23 May 2002

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We report metalorganic vapor-phase epitaxial growth and structural and photoluminescent characteristics of ZnO nanorods. The nanorods were grown on Al2O3(00⋅1) substrates at 400 °C without employing any metal catalysts usually needed in other methods. Electron microscopy revealed that nanorods with uniform distributions in their diameters, lengths, and densities were grown vertically from the substrates. The mean diameter of the nanorods is as narrow as 25 nm. In addition, x-ray diffraction measurements clearly show that ZnO nanorods were grown epitaxially with homogeneous in-plane alignment as well as a c-axis orientation. More importantly, from photoluminescence spectra of the nanorods strong and narrow excitonic emission and extremely weak deep level emission were observed, indicating that the nanorods are of high optical quality. © 2002 American Institute of Physics.
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81.07.Bc Nanocrystalline materials
81.05.Dz II-VI semiconductors
61.46.-w Structure of nanoscale materials
81.15.Kk Vapor phase epitaxy; growth from vapor phase
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
78.55.Et II-VI semiconductors
78.66.Hf II-VI semiconductors
78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
68.35.Ct Interface structure and roughness
71.35.-y Excitons and related phenomena

X-ray photoemission spectroscopy study of fluorinated single-walled carbon nanotubes

Kay Hyeok An, Jeong Goo Heo, Kwan Goo Jeon, Dong Jae Bae, Chulsu Jo, Cheol Woong Yang, Chong-Yun Park, Young Hee Lee, Young Seak Lee, and Young Su Chung

Appl. Phys. Lett. 80, 4235 (2002); http://dx.doi.org/10.1063/1.1482801 (3 pages) | Cited 51 times

Online Publication Date: 23 May 2002

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We have investigated the change of atomic and electronic structures of fluorinated single-walled carbon nanotubes (SWCNTs) using x-ray photoemission spectroscopy (XPS), electrical resistivity measurements, and transmission electron microscopy (TEM). The fluorine content increases with increasing reaction temperature up to 300 °C. XPS indicated that the fluorinated SWCNT reveals an ionic-bonding character at low concentration and covalent-bonding character at high concentration. The resistivity increases with reaction temperatures, resulting from the band gap enlargement at high fluorine concentration. It is also observed from TEM that the fluorination at reaction temperature above 250 °C leads to the disintegration of the CNT structures and formation of various phases such as multiwall-like and turbostratic morphologies. © 2002 American Institute of Physics.
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73.22.-f Electronic structure of nanoscale materials and related systems
61.46.-w Structure of nanoscale materials
73.63.Fg Nanotubes
81.07.De Nanotubes
68.37.Lp Transmission electron microscopy (TEM)
82.20.-w Chemical kinetics and dynamics

Classical microwave response of coupled quantum dots in single-wall carbon nanotubes

K. Ishibashi, M. Suzuki, T. Ida, and Y. Aoyagi

Appl. Phys. Lett. 80, 4238 (2002); http://dx.doi.org/10.1063/1.1483127 (3 pages)

Online Publication Date: 23 May 2002

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The dc transport properties of coupled quantum dots in single-wall carbon nanotubes have been studied below 100 mK under microwave irradiation. The Coulomb oscillations for different microwave power were similar to those for different bias voltages without microwave. The current–voltage curves showed simple shifts as the microwave power was increased. These experimental observations may be explained by the classical response of the coupled quantum dots to the microwave irradiation. © 2002 American Institute of Physics.
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73.63.Fg Nanotubes
73.63.Kv Quantum dots
73.50.Mx High-frequency effects; plasma effects

Metalorganic chemical vapor deposition of aluminum oxide on Si: Evidence of interface SiO2 formation

A. Roy Chowdhuri, C. G. Takoudis, R. F. Klie, and N. D. Browning

Appl. Phys. Lett. 80, 4241 (2002); http://dx.doi.org/10.1063/1.1483903 (3 pages) | Cited 25 times

Online Publication Date: 23 May 2002

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Thin films of aluminum oxide were deposited on H-passivated Si(100) substrate using trimethylaluminum and oxygen at 0.5 Torr and 300 °C. Fourier transform infrared (FTIR) and x-ray photoelectron spectroscopic analyses of these films showed no aluminum silicate phase at the film–substrate interface. The O/Al ratio in the deposited film was found to be higher than that in stoichiometric Al2O3. On annealing the as-deposited samples in Ar at 900 °C, an absorption peak due to the transverse optical phonon for the Si�O�Si stretching mode appeared in the FTIR spectra. A combination of Z-contrast imaging and electron energy-loss spectroscopy in the scanning transmission electron microscope confirmed that the annealed samples developed a layer of silicon dioxide at the aluminum oxide–Si interface. Our results suggest that excess oxygen present in the deposited film reacts with the underlying Si substrate and forms silicon oxide. © 2002 American Institute of Physics.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
61.72.Cc Kinetics of defect formation and annealing
68.35.Fx Diffusion; interface formation
68.55.Nq Composition and phase identification

Mechanics of nanosprings: Stiffness and Young’s modulus of molybdenum-based nanocrystals

C. Durkan, A. Ilie, M. S. M. Saifullah, and M. E. Welland

Appl. Phys. Lett. 80, 4244 (2002); http://dx.doi.org/10.1063/1.1483927 (3 pages) | Cited 3 times

Online Publication Date: 23 May 2002

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We describe measurements of the stiffness and Young’s modulus, Y of single crystals of molybdenum-based compounds. Atomic force microscopy is used first to image, and then to perform stiffness measurements on crystals which are growing up out of a substrate. Y is extracted by comparing the measured stiffness with that calculated from a continuum elasticity model of the crystals, whose experimentally indeterminate parameters are the Young’s modulus and the geometry. We find a value for Y in the range 0.8–1.4 TPa, depending on the assumed geometry of the nanocrystal. As these crystals are essentially perfectly ordered on the micron scale, this opens the possibility of forming composite materials of immense strength. © 2002 American Institute of Physics.
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62.20.D- Elasticity
81.40.Jj Elasticity and anelasticity, stress-strain relations
68.37.Ps Atomic force microscopy (AFM)
62.25.-g Mechanical properties of nanoscale systems
61.46.-w Structure of nanoscale materials
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