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5 Aug 2002

Volume 81, Issue 6, pp. 951-1149

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Ordered arrays of vertically correlated GaAs and AlAs quantum wires grown on a GaAs(311)A surface

D. Litvinov, A. Rosenauer, D. Gerthsen, N. N. Ledentsov, D. Bimberg, G. A. Ljubas, V. V. Bolotov, V. A. Volodin, M. D. Efremov, V. V. Preobrazhenskii, B. R. Semyagin, and I. P. Soshnikov

Appl. Phys. Lett. 81, 1080 (2002); http://dx.doi.org/10.1063/1.1497994 (3 pages) | Cited 10 times

Online Publication Date: 30 July 2002

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We study GaAs–AlAs short-period superlattices (SPSLs) grown on a GaAs(311)A surface using plan-view transmission electron microscopy (TEM). A strong in-plane compositional modulation with a period of 3.2 nm along the [0math1] direction is revealed by TEM under chemically sensitive imaging conditions and in high-resolution TEM. Our results confirm the formation of highly ordered vertically aligned arrays of GaAs and AlAs quantum wires formed via self-organized growth. Bright photoluminescence (PL) at room temperature in the green and yellow spectral range is observed. © 2002 American Institute of Physics.
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68.65.La Quantum wires (patterned in quantum wells)
68.65.Cd Superlattices
78.67.Lt Quantum wires
78.55.Cr III-V semiconductors

Field emission from individual B–C–N nanotube rope

P. Dorozhkin, D. Golberg, Y. Bando, and Z.-C. Dong

Appl. Phys. Lett. 81, 1083 (2002); http://dx.doi.org/10.1063/1.1497194 (3 pages) | Cited 22 times

Online Publication Date: 30 July 2002

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The field-emission characteristics of individual ropes made of B–C–N nanotubes were measured in situ in a low-energy electron point source microscope. The tungsten field emission tip of the microscope was used as a movable electrode, approaching the rope, and acting as an anode during field-emission measurements. The atomic structure and chemical composition of the ropes were analyzed by high-resolution transmission electron microscopy and electron energy-loss spectroscopy. The tubes assembled within the ropes typically revealed open-tip ends, a small number of layers and zigzag chirality. We found that the field-emission properties of the B–C–N nanotube ropes are competitive with conventional C nanotubes, with the expected additional benefit that the B–C–N ropes exhibit higher environmental stability. © 2002 American Institute of Physics.
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79.70.+q Field emission, ionization, evaporation, and desorption
61.46.-w Structure of nanoscale materials
79.20.Uv Electron energy loss spectroscopy

Why do (2×4) GaAs and InAs (001) surfaces exposed to phosphorus have so different behavior? Elastic strain arguments

X. Wallart, C. Priester, D. Deresmes, T. Gehin, and F. Mollot

Appl. Phys. Lett. 81, 1086 (2002); http://dx.doi.org/10.1063/1.1499230 (3 pages) | Cited 2 times

Online Publication Date: 30 July 2002

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When exposed to phosphorus, the (2×4) GaAs surface tends rapidly to roughen whereas it is not the case for the (2×4) InAs one, even after long exposure times. X-ray photoemission measurements show that the incorporated phosphorus amount is similar in both cases. The elastic energy difference between these two materials with incorporated phosphorus, calculated within the valence force field approximation, appears to be strong enough to explain this phenomenon. The role of surface reconstruction, mainly dimerization, on phosphorus incorporation is also emphasized. © 2002 American Institute of Physics.
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68.35.B- Structure of clean surfaces (and surface reconstruction)
81.05.Ea III-V semiconductors
68.35.Gy Mechanical properties; surface strains
79.60.Dp Adsorbed layers and thin films
62.20.F- Deformation and plasticity
68.35.Md Surface thermodynamics, surface energies

Growth front roughening of room-temperature deposited copper nanocluster films

G. Palasantzas, S. A. Koch, and J. Th. M. De Hosson

Appl. Phys. Lett. 81, 1089 (2002); http://dx.doi.org/10.1063/1.1497200 (3 pages) | Cited 9 times

Online Publication Date: 30 July 2002

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Growth front aspects of copper nanocluster films deposited with low energy onto silicon substrates at room temperature are investigated by atomic force microscopy. Analyses of the height-difference correlation function yield a roughness exponent H of 0.45±0.05. The root-mean-sqaure roughness amplitude w evolves with deposition time as a power law, w∝tβ (β = 0.62±0.07), leading also to a power-law increase of the local surface slope ρ, ρ∝tc (c = 0.73±0.09). These scaling exponents, in combination with an asymmetrical height distribution, point at a complex nonlinear roughening mechanism dominated by the formation of voids resulting in a highly porous film. © 2002 American Institute of Physics.
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68.55.A- Nucleation and growth
81.07.Bc Nanocrystalline materials
61.46.-w Structure of nanoscale materials
81.16.Ta Atom manipulation
68.37.Ps Atomic force microscopy (AFM)
61.72.Qq Microscopic defects (voids, inclusions, etc.)

Electron charging and discharging in amorphous silicon quantum dots embedded in silicon nitride

Nae-Man Park, Suk-Ho Choi, and Seong-Ju Park

Appl. Phys. Lett. 81, 1092 (2002); http://dx.doi.org/10.1063/1.1497444 (3 pages) | Cited 20 times

Online Publication Date: 30 July 2002

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Electron charging and discharging were produced in metal-insulator-semiconductor structures containing amorphous silicon quantum dots (a-Si QDs) by increasing the applied voltage in a stepwise fashion without changing its sign. The metal-insulator-semiconductor structure was fabricated using an insulating silicon nitride film containing a-Si QDs by plasma-enhanced chemical vapor deposition. This charging behavior suggests that a-Si QDs in the silicon nitride are positively charged due to nitrogen dangling bonds. The surface state of the a-Si QDs is considered to play a dominant role in the charging properties such as electron storage and charge-loss rate in the a-Si QDs. © 2002 American Institute of Physics.
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73.21.La Quantum dots
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)

Blackbody radiation from resistively heated multiwalled carbon nanotubes during field emission

M. Sveningsson, M. Jönsson, O. A. Nerushev, F. Rohmund, and E. E. B. Campbell

Appl. Phys. Lett. 81, 1095 (2002); http://dx.doi.org/10.1063/1.1498493 (3 pages) | Cited 24 times

Online Publication Date: 30 July 2002

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We report the observation of blackbody radiation from aligned multiwalled carbon nanotubes undergoing field emission. The light intensity correlates with fluctuations in the emission current. The onset of light emission occurs at an emission current of 1 mA/cm2 and corresponds to a temperature on the order of 1550 K. Beyond this critical current irreversible changes occur in the nanotube film. The correlation between light intensity and emission current provides convincing evidence for Joule heating and stable operation for nanotube temperatures up to at least 2000 K and emission current densities on the order of 10 mA/cm2. © 2002 American Institute of Physics.
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78.60.Fi Electroluminescence
81.07.De Nanotubes
79.70.+q Field emission, ionization, evaporation, and desorption
73.63.Fg Nanotubes
78.67.Ch Nanotubes
44.40.+a Thermal radiation

Secondary electron emission from magnesium oxide on multiwalled carbon nanotubes

Won Seok Kim, Whikun Yi, SeGi Yu, Jungna Heo, Taewon Jeong, Jeonghee Lee, Chang Soo Lee, J. M. Kim, Hee Jin Jeong, Young Min Shin, and Young Hee Lee

Appl. Phys. Lett. 81, 1098 (2002); http://dx.doi.org/10.1063/1.1498492 (3 pages) | Cited 20 times

Online Publication Date: 30 July 2002

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We have investigated effects of electric fields on the yield of secondary electron emission (SEE) from the primary electron bombardment on magnesium oxide (MgO) covering vertically grown multiwalled carbon nanotubes (MWCNTs). We observe that the yield of SEE increases up to at least 22 000 at a special condition. The strong local field generated by the sharp tip of vertically grown MWCNTs accelerates secondary electrons generated by primary electrons. This eventually gives rise to so called Townsend avalanche effect, generating huge number of secondary electrons in a MgO film. Emission mechanism for such a high SEE will be further discussed with energy spectrum analysis. © 2002 American Institute of Physics.
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79.20.Hx Electron impact: secondary emission
73.50.Fq High-field and nonlinear effects
77.22.Jp Dielectric breakdown and space-charge effects
81.07.De Nanotubes
73.61.Ng Insulators

Carbon nanotubes as masks against ion irradiation: An insight from atomistic simulations

A. V. Krasheninnikov, K. Nordlund, and J. Keinonen

Appl. Phys. Lett. 81, 1101 (2002); http://dx.doi.org/10.1063/1.1499224 (3 pages) | Cited 20 times

Online Publication Date: 30 July 2002

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Recent experiments show that carbon nanotubes can be used as masks against ion irradiation to make metallic nanowires of a few nanometers in width. In order to ascertain the limitations of this technique, we use molecular dynamics and simulate ion irradiation of multiwalled nanotubes. We derive an equation which for a given nanowire material allows one to estimate the theoretical limit on the minimum width of the wire which can be made using this technique. © 2002 American Institute of Physics.
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61.82.Rx Nanocrystalline materials
61.80.Jh Ion radiation effects
85.40.Hp Lithography, masks and pattern transfer
81.16.Nd Micro- and nanolithography

Single-crystal Si formed on amorphous substrate at low temperature by nanopatterning and nickel-induced lateral crystallization

Jian Gu, Stephen Y. Chou, Nan Yao, Henny Zandbergen, and Jeffrey K. Farrer

Appl. Phys. Lett. 81, 1104 (2002); http://dx.doi.org/10.1063/1.1498146 (3 pages) | Cited 9 times

Online Publication Date: 30 July 2002

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Single-crystal silicon has been achieved by patterning amorphous silicon film on silicon dioxide substrate into nanoscale lines and nickel-induced lateral crystallization. Line width affects the single-crystal silicon formation significantly. Narrow line widths, 30 nm or less, resulted in little lateral crystallization; while for line widths above 250 nm, multiple grains started to form. In-situ transmission electron microscope observation has been used to study the crystallization process. Lithography-constrained single seeding is proposed to explain the single-crystal formation. © 2002 American Institute of Physics.
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81.15.Np Solid phase epitaxy; growth from solid phases
68.55.A- Nucleation and growth
81.05.Cy Elemental semiconductors
81.07.Bc Nanocrystalline materials
64.70.K- Solid-solid transitions
81.16.Nd Micro- and nanolithography
85.40.Hp Lithography, masks and pattern transfer
68.37.Lp Transmission electron microscopy (TEM)

Vertically stacking self-assembled quantum wires

Xiaodong Mu, Yujie J. Ding, Haeyeon Yang, and Gregory J. Salamo

Appl. Phys. Lett. 81, 1107 (2002); http://dx.doi.org/10.1063/1.1497993 (3 pages) | Cited 4 times

Online Publication Date: 30 July 2002

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Self-assembled InP/InAs/InP quantum wires (QWRs) have been stacked for ten vertical periods and characterized based on photoluminescence (PL) studies. Compared with single-period QWRs, behaviors in the PL spectra and some fundamental effects have been observed. Through the detailed analyses of the PL shapes, linewidths, and polarizations at different pump wavelengths, pump intensities, and sample temperatures, it is evidenced that the wire width and subband energy gradually decrease while the average wire thickness increases from the bottom period to the top one, period by period. Meanwhile, the average wire width gradually decreases. Following these results, growth conditions have been suggested, which can be essential to improving the optical quality of these self-assembled QWRs. © 2002 American Institute of Physics.
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78.66.Fd III-V semiconductors
78.55.Cr III-V semiconductors
68.65.La Quantum wires (patterned in quantum wells)

Transformation of BxCyNz nanotubes to pure BN nanotubes

Wei-Qiang Han, W. Mickelson, John Cumings, and A. Zettl

Appl. Phys. Lett. 81, 1110 (2002); http://dx.doi.org/10.1063/1.1498494 (3 pages) | Cited 54 times

Online Publication Date: 30 July 2002

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We demonstrate that multiwalled BxCyNz nanotubes can be efficiently converted to BN multiwalled nanotubes via an oxidation treatment. The microstructure and composition of the precursors and final products have been characterized by high-resolution transmission electron microscopy, electron energy-loss spectroscopy, and energy dispersive x-ray spectroscopy. The conversion process is monitored by thermogravimetric analysis. Carbon layers of BxCyNz nanotubes start to oxidize at 550 °C, thereby transforming BxCyNz nanotubes into pure BN nanotubes. The remarkable thermal stability of pure BN nanotubes in an oxidizing environment is also established. © 2002 American Institute of Physics.
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61.46.-w Structure of nanoscale materials
81.07.De Nanotubes
65.80.-g Thermal properties of small particles, nanocrystals, nanotubes, and other related systems
61.48.-c Structure of fullerenes and related hollow and planar molecular structures
82.30.Lp Decomposition reactions (pyrolysis, dissociation, and fragmentation)
82.60.Qr Thermodynamics of nanoparticles

Ultrathin CNx overcoats for 1 Tb/in.2 hard disk drive systems

D. J. Li, Murat U. Guruz, C. Singh Bhatia, and Yip-Wah Chung

Appl. Phys. Lett. 81, 1113 (2002); http://dx.doi.org/10.1063/1.1498866 (3 pages) | Cited 19 times

Online Publication Date: 30 July 2002

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Carbon nitride films were grown on silicon and hard disk substrates using pulsed dc magnetron sputtering in a single-cathode deposition system. Substrates were mounted on a specially designed holder that allowed 45° tilt angle and substrate rotation about the surface normal up to 20 rpm. The influence of substrate bias, substrate tilt, and rotation on film growth and properties was studied. Films with the lowest rms surface roughness and corrosion performance were obtained at −100 V substrate bias with substrate tilt and rotation. Atomic force microscope scans over 10×10 μm2 sampling areas showed that 50 nm thick CNx films prepared under these conditions have roughness almost four times lower than those prepared without substrate tilt and rotation. We observed a twofold reduction in corrosion damage for hard disk substrates with 1 nm thick CNx overcoats deposited with substrate tilt and rotation. This improved performance is likely a result of more efficient and uniform momentum transfer parallel to the surface during deposition in this configuration. © 2002 American Institute of Physics.
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68.55.-a Thin film structure and morphology
81.15.Cd Deposition by sputtering
81.65.Kn Corrosion protection
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.37.Ps Atomic force microscopy (AFM)

Fluorescence spectroscopy and transmission electron microscopy of the same isolated semiconductor nanocrystals

Felix Koberling, Alf Mews, Günther Philipp, Ute Kolb, Inga Potapova, Marko Burghard, and Thomas Basché

Appl. Phys. Lett. 81, 1116 (2002); http://dx.doi.org/10.1063/1.1499221 (3 pages) | Cited 8 times

Online Publication Date: 30 July 2002

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We present a method to establish a correlation between the crystalline structure and the fluorescence properties of isolated semiconductor nanocrystals. By using ultrathin silicon nitride substrates with markers, we have localized and investigated the same particles in both a high-resolution transmission electron microscope (TEM) and a confocal optical microscope. We have found that the observation of strong fluorescence emission does not require single domain particles. Additionally, we have correlated the size and shape of a particle as determined by TEM and its spectral properties like emission wavelength and spectral diffusion. © 2002 American Institute of Physics.
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78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
61.46.-w Structure of nanoscale materials
78.55.Et II-VI semiconductors
68.37.Lp Transmission electron microscopy (TEM)
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