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Title: Size-dependent near-field coupling observed from InN nanodotsgrown on nitrided sapphire

Abstract

Optical contrast from InN nanodots grown on nitrided sapphire is investigated using apertureless near-field scanning optical microscopy at two different visible wavelengths, 633 nm and 532 nm. The dependence of the near-field signal on the size of the dots is described using a coupled dipole model expanded to four dipoles. The near-field signal from InN dots with a height of <1 nm is detected due to dipole-dipole coupling.

Authors:
; ; ;
Publication Date:
Research Org.:
COLLABORATION - UCBerkeley
OSTI Identifier:
917343
Report Number(s):
LBNL-63505
Journal ID: ISSN 0009-2614; CHPLBC; TRN: US200816%%535
DOE Contract Number:
DE-AC02-05CH11231
Resource Type:
Journal Article
Resource Relation:
Journal Name: Chemical Physics Letters; Journal Volume: 443; Journal Issue: 4-6; Related Information: Journal Publication Date: 08/2007
Country of Publication:
United States
Language:
English
Subject:
37; DIPOLES; OPTICAL MICROSCOPY; SAPPHIRE; WAVELENGTHS

Citation Formats

Stebounova, L.V., Romanyuk, Y.E., Dengel, R.G., and Leone, S.R. Size-dependent near-field coupling observed from InN nanodotsgrown on nitrided sapphire. United States: N. p., 2007. Web. doi:10.1016/j.cplett.2007.06.093.
Stebounova, L.V., Romanyuk, Y.E., Dengel, R.G., & Leone, S.R. Size-dependent near-field coupling observed from InN nanodotsgrown on nitrided sapphire. United States. doi:10.1016/j.cplett.2007.06.093.
Stebounova, L.V., Romanyuk, Y.E., Dengel, R.G., and Leone, S.R. Sat . "Size-dependent near-field coupling observed from InN nanodotsgrown on nitrided sapphire". United States. doi:10.1016/j.cplett.2007.06.093.
@article{osti_917343,
title = {Size-dependent near-field coupling observed from InN nanodotsgrown on nitrided sapphire},
author = {Stebounova, L.V. and Romanyuk, Y.E. and Dengel, R.G. and Leone, S.R.},
abstractNote = {Optical contrast from InN nanodots grown on nitrided sapphire is investigated using apertureless near-field scanning optical microscopy at two different visible wavelengths, 633 nm and 532 nm. The dependence of the near-field signal on the size of the dots is described using a coupled dipole model expanded to four dipoles. The near-field signal from InN dots with a height of <1 nm is detected due to dipole-dipole coupling.},
doi = {10.1016/j.cplett.2007.06.093},
journal = {Chemical Physics Letters},
number = 4-6,
volume = 443,
place = {United States},
year = {Sat Apr 14 00:00:00 EDT 2007},
month = {Sat Apr 14 00:00:00 EDT 2007}
}
  • A series of self-assembled InN dots are grown by radio frequency (RF) plasma-assisted molecular beam epitaxy (MBE) directly on nitrided sapphire. Initial nitridation of the sapphire substrates at 900 C results in the formation of a rough AlN surface layer, which acts as a very thin buffer layer and facilitates the nucleation of the InN dots according to the Stranski-Krastanow growth mode, with a wetting layer of {approx}0.9 nm. Atomic force microscopy (AFM) reveals that well-confined InN nanoislands with the greatest height/width at half-height ratio of 0.64 can be grown at 460 C. Lower substrate temperatures result in a reducedmore » aspect ratio due to a lower diffusion rate of the In adatoms, whereas the thermal decomposition of InN truncates the growth at T>500 C. The densities of separated dots vary between 1.0 x 10{sup 10} cm{sup -2} and 2.5 x 10{sup 10} cm{sup -2} depending on the growth time. Optical response of the InN dots under laser excitation is studied with apertureless near-field scanning optical microscopy and photoluminescence spectroscopy, although no photoluminescence is observed from these samples. In view of the desirable implementation of InN nanostructures into photonic devices, the results indicate that nitrided sapphire is a suitable substrate for growing self-assembled InN nanodots.« less
  • InN quantum dots (QDs) were grown on Si (111) by epitaxial Stranski-Krastanow growth mode using plasma-assisted molecular beam epitaxy. Single-crystalline wurtzite structure of InN QDs was verified by the x-ray diffraction and transmission electron microscopy. Scanning tunneling microscopy has been used to probe the structural aspects of QDs. A surface bandgap of InN QDs was estimated from scanning tunneling spectroscopy (STS) I-V curves and found that it is strongly dependent on the size of QDs. The observed size-dependent STS bandgap energy shifts with diameter and height were theoretical explained based on an effective mass approximation with finite-depth square-well potential model.
  • The energy spectra of electrons field emitted from individual, supported Au clusters have been measured as a function of cluster size. Data are presented for clusters with nominal diameters in the range 1.3--3.2 nm. For the smallest clusters, the energy of the field-emitted electrons lies below the Fermi level of the substrate and fine structure in the energy distribution is observed. As the cluster size increases, the energy distribution shifts toward the Fermi level of the substrate and the fine structure disappears.
  • Despite the fact the alloys of wurtzite AlN, GaN, and InN are widely used in electronics, the studies on their thermal conductivities (κ) are inadequate, and the intrinsic limits are still unknown. In this work, the intrinsic κ of alloys and their films are calculated from first-principles within the virtual crystal treatment. The κ of alloys are strongly suppressed even by a small amount of alloying. For instance, with only 1% alloying of Al or In, κ of GaN decreases about 60%. At relatively high alloying, with concentration between 0.2 and 0.8, the κ of alloys are not significantly changed.more » At room temperature, the minimal a-axis κ are about 18, 22, and 8 W m{sup −1} K{sup −1}, while the minimal c-axis κ are about 22, 27, and 10 W m{sup −1} K{sup −1} for Al{sub x}Ga{sub 1−x}N, In{sub x}Ga{sub 1−x}N, and In{sub x}Al{sub 1−x}N, respectively. The size effect in films can persist up to a few tens of micrometers, and κ can be reduced by half in about 100 nm thick films.« less