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6 May 2002

Volume 80, Issue 18, pp. 3247-3450

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Subwavelength-sized aperture fabrication in aluminum by a self-terminated corrosion process in the evanescent field

D. Haefliger and A. Stemmer

Appl. Phys. Lett. 80, 3397 (2002); http://dx.doi.org/10.1063/1.1476059 (3 pages) | Cited 2 times

Online Publication Date: 29 April 2002

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We present a simple, one-step process to fabricate apertures of high quality for scanning near-field optical microscope probes based on aluminum-coated silicon-nitride cantilevers. An evanescent optical field at the glass–water interface is used to heat up the aluminum at the tip apex due to light absorption. The heat induces breakdown of the passivating oxide layer and corrosion of the metal. Apertures with a protruding silicon-nitride tip of up to 30 nm height and minimal diameter of 38 nm are fabricated. The diameter is predefined by the lateral dimension of the silicon-nitride tip while the tip height is controlled by the penetration depth of the evanescent field. The corrosion process proves to be self-terminating, yielding highly reproducible tip heights. Near-field optical resolution in the transmission mode of 85 nm is demonstrated. © 2002 American Institute of Physics.
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07.79.Fc Near-field scanning optical microscopes

Apertureless optical near-field fabrication using an atomic force microscope on photoresists

Alvarado Tarun, Marlon Rosendo H. Daza, Norihiko Hayazawa, Yasushi Inouye, and Satoshi Kawata

Appl. Phys. Lett. 80, 3400 (2002); http://dx.doi.org/10.1063/1.1476956 (3 pages) | Cited 15 times

Online Publication Date: 29 April 2002

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We present an apertureless optical near-field fabrication using an atomic force microscope. With this technique, we can directly pattern 100 nm lines that are smaller than the diameter of the incident far-field diffraction spot on positive photoresist spin coated over glass substrate. The nanostructure fabrication was carried out by the field enhancement generated at the tip apex of an apertureless probe illuminated with a 403 nm laser light. Results also show that the amount of energy required to induce photolysis seems to decrease in the presence of the tip. © 2002 American Institute of Physics.
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81.16.Ta Atom manipulation
81.16.Nd Micro- and nanolithography
85.40.Hp Lithography, masks and pattern transfer

Terahertz conductivity of anisotropic single walled carbon nanotube films

Tae-In Jeon, Keun-Ju Kim, Chul Kang, Seung-Jae Oh, Joo-Hiuk Son, Kay Hyeok An, Dong Jae Bae, and Young Hee Lee

Appl. Phys. Lett. 80, 3403 (2002); http://dx.doi.org/10.1063/1.1476713 (3 pages) | Cited 56 times

Online Publication Date: 29 April 2002

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Absorption and dispersion of singlewalled carbon nanotube films were measured using an optoelectronic THz beam system for THz time-domain spectroscopy. The anisotropically aligned nanotube films were prepared through simple mechanical squeezing with a bar coater. The angle-dependent absorption and dispersion values were then measured. Results indicate that the index of refraction decreases with increasing frequency (0.1–0.8 THz), whereas the real conductivity increases with increasing frequency. The real conductivity measured is not congruent with the simple Drude model, but it follows a Maxwell–Garnett model, where the nanotubes are embedded in a dielectric host. © 2002 American Institute of Physics.
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73.63.Fg Nanotubes
73.50.Mx High-frequency effects; plasma effects
73.25.+i Surface conductivity and carrier phenomena

Self-assembly of Si nanoclusters on 6H–SiC(0001)-(3×3) reconstructed surface

W. J. Ong, E. S. Tok, H. Xu, and A. T. S. Wee

Appl. Phys. Lett. 80, 3406 (2002); http://dx.doi.org/10.1063/1.1476398 (3 pages) | Cited 7 times

Online Publication Date: 29 April 2002

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Scanning tunneling microscopy (STM) and x-ray photoelectron spectroscopy (XPS) were used to observe the formation of metastable (6×6)-Si nanoclusters (diameter ∼ 16.5±0.1 A) on 6H–SiC(0001)-(3×3) surface. STM and XPS data suggest that these clusters are derived from the ejection of the Si-tetracluster unit of the initial (3×3) reconstruction at elevated temperatures and occur in a less Si-rich environment than the initial surface. The observed surface restructuring is related to the reconfiguration of coplanar Si bonds within the (3×3) unit cell. The occurrence of these regularly sized “magic” clusters demonstrates the potential of nanostructure formation of Si on SiC. © 2002 American Institute of Physics.
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68.43.Hn Structure of assemblies of adsorbates (two- and three-dimensional clustering)
81.16.Dn Self-assembly
68.35.B- Structure of clean surfaces (and surface reconstruction)
61.46.-w Structure of nanoscale materials
81.07.Bc Nanocrystalline materials
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
79.60.Dp Adsorbed layers and thin films

Writing of high-density patterned perpendicular media with a conventional longitudinal recording head

M. Albrecht, A. Moser, C. T. Rettner, S. Anders, T. Thomson, and B. D. Terris

Appl. Phys. Lett. 80, 3409 (2002); http://dx.doi.org/10.1063/1.1476062 (3 pages) | Cited 35 times

Online Publication Date: 29 April 2002

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We have fabricated arrays of magnetic islands in perpendicular CoCrPt media with ∼100 nm lateral dimension using a focused ion beam. A quasistatic write/read tester was used to study aspects of the recording physics of these patterned media. We present results on the variation of the readback signal as the phase of the written square wave changes with respect to the patterned array as a function of island size and write current. Using an analytic near-field expression for head field we are able to model how the observed dependence between phase shift and readback signal as a function of write current arises. This analysis allows us to gain an insight into the role of the island switching field distribution and the write head magnetic field gradient in the patterned media writing process. © 2002 American Institute of Physics.
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85.70.Kh Magnetic thin film devices: magnetic heads (magnetoresistive, inductive, etc.); domain-motion devices, etc.
75.50.Ss Magnetic recording materials

Mapping strain fields in ultrathin bonded Si wafers by x-ray scattering

M. Nielsen, M. Poulsen, O. Bunk, C. Kumpf, R. Feidenhans’l, R. L. Johnson, F. Jensen, and F. Grey

Appl. Phys. Lett. 80, 3412 (2002); http://dx.doi.org/10.1063/1.1476702 (3 pages) | Cited 4 times

Online Publication Date: 29 April 2002

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X-ray scattering reveals the atomic displacements arising from rotational misalignment in ultrathin silicon bonded wafers. For a 4.3 nm top wafer, the strain field penetrates from the bonded interface to the surface and produces distinctive finite-size oscillations in x-ray data. Analytical calculations permit the atomic displacements throughout the thin top wafer to be modeled. © 2002 American Institute of Physics.
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68.35.Gy Mechanical properties; surface strains
61.05.cf X-ray scattering (including small-angle scattering)

Absorption spectra and chirality of single-walled 4 Å carbon nanotubes

WanZhen Liang, GuanHua Chen, Zhaoming Li, and Zi-Kang Tang

Appl. Phys. Lett. 80, 3415 (2002); http://dx.doi.org/10.1063/1.1478155 (3 pages) | Cited 23 times

Online Publication Date: 29 April 2002

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Absorption spectrum of recently discovered single-walled 4 Å carbon nanotubes is measured. The semiempirical PM3 localized-density-matrix method is employed to evaluate the absorption spectra of three possible 4 Å single-walled carbon nanotubes, (3,3), (4,2), and (5,0). Both experimental and calculated results reveal that these nanotubes have finite optical gaps and strong anisotropic optical responses. When the electric field is perpendicular to the nanotubes, they are transparent to visible lights; and this is confirmed and explained by the calculations. Compared to the measured absorption spectrum, calculated absorption spectra are used to determine the chirality of the nanotubes synthesized in the channels of porous zeolites. © 2002 American Institute of Physics.
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78.67.Ch Nanotubes
61.46.-w Structure of nanoscale materials
78.40.Ri Fullerenes and related materials
31.15.bu Semi-empirical and empirical calculations (differential overlap, Hückel, PPP methods, etc.)
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
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