排序方式: 共有9条查询结果,搜索用时 15 毫秒
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Schramm A Tommila J Strelow C Hakkarainen TV Tukiainen A Dumitrescu M Mews A Kipp T Guina M 《Nanotechnology》2012,23(17):175701
We present the growth of single, site-controlled InAs quantum dots on GaAs templates using UV-nanoimprint lithography and molecular beam epitaxy. A large quantum dot array with a period of 1.5 μm was achieved. Single quantum dots were studied by steady-state and time-resolved micro-photoluminescence experiments. We obtained single exciton emission with a linewidth of 45 μeV. In time-resolved experiments, we observed decay times of about 670 ps. Our results underline the potential of nanoimprint lithography and molecular beam epitaxy to create large-scale, single quantum dot arrays. 相似文献
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We report on the effect of post-growth thermal annealing of [011]- ,[011(-)]-, and [010]-oriented quantum dot chains grown by molecular beam epitaxy on GaAs(100) substrates patterned by UV-nanoimprint lithography. We show that the quantum dot chains experience a blueshift of the photoluminescence energy, spectral narrowing, and a reduction of the intersubband energy separation during annealing. The photoluminescence blueshift is more rapid for the quantum dot chains than for self-assembled quantum dots that were used as a reference. Furthermore, we studied polarization resolved photoluminescence and observed that annealing reduces the intrinsic optical anisotropy of the quantum dot chains and the self-assembled quantum dots. 相似文献
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Juha Tommila Arto Aho Antti Tukiainen Ville Polojrvi Joel Salmi Tapio Niemi Mircea Guina 《Progress in Photovoltaics: Research and Applications》2013,21(5):1158-1162
We report on the performance of biomimicked antireflection coating applied to dilute nitride solar cell. The coating consists of nanostructures replicating the moth‐eye geometry and has been fabricated by nanoimprint lithography directly within the window layer covering the dilute nitride absorbing junction. The mean reflectivity within the spectral range of 320–1800 nm remains under 5% for incident angles up to 45°. The effect of the coating on the cell performance was assessed by measuring the current–voltage characteristics under simulated solar illumination. A clear performance increase was identified when comparing a solar cell with the moth‐eye coating with a solar cell having a standard SiNx/SiO2 coating. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
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Tommila JT Strelow C Schramm A Hakkarainen TV Dumitrescu M Kipp T Guina M 《Nanoscale research letters》2012,7(1):313
ABSTRACT: We report the temperature-dependent photoluminescence of single site-controlled and self-assembled InAs quantum dots. We have used nanoimprint lithography for patterning GaAs(100) templates and molecular beam epitaxy for quantum dot deposition. We show that the influence of the temperature on the photoluminescence properties is similar for quantum dots on etched nanopatterns and randomly positioned quantum dots on planar surfaces. The photoluminescence properties indicate that the prepatterning does not degrade the radiative recombination rate for the site-controlled quantum dots. 相似文献
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Juha M. Kontio Janne Simonen Juha Tommila Markus Pessa 《Microelectronic Engineering》2010,87(9):1711-2579
We introduce a novel method for fabricating nanocones of various metals. Based on a combination of UV-nanoimprint lithography and electron beam evaporation, the method enables fast, high volume, and reproducible fabrication of conical nanostructures on flat substrates. We investigate cone formation with eight different metals and find that the shape of the cone depends on the material characteristics of the deposited metal. 相似文献
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Jukka Viheriälä Juha Tommila Tomi Leinonen Mihail Dumitrescu Lauri Toikkanen Tapio Niemi Markus Pessa 《Microelectronic Engineering》2009,86(3):321-324
We show how to use a modified poly-dimethyl-siloxane (PDMS) soft stamp to reduce pattern deformation and residual layer thickness in soft UV-nanoimprint lithography. A soft stamp thinned with toluene reduces the residual layer of a resist by as much as 50% compared to an unthinned stamp. We apply the soft UV-nanoimprint to prepare nanopatterned waveguides for a single-frequency diode laser. This laser operates with a side-mode suppression ratio of 50 dB, which indicates that the patterns are precise and uniform over the whole imprint field. To the best of our knowledge, this is the first single-frequency laser fabricated by soft UV-nanoimprint technology. 相似文献
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Hakkarainen TV Tommila J Schramm A Tukiainen A Ahorinta R Dumitrescu M Guina M 《Nanotechnology》2011,22(29):295604
We combine nanoimprint lithography and molecular beam epitaxy for the site-controlled growth of InAs quantum dot chains on GaAs(100) substrates. We study the influence of quantum dot growth temperature and regrowth buffer thickness on the formation of the quantum dot chains. In particular, we show that by carefully tuning the growth conditions we can achieve equal quantum dot densities and photoluminescence ground state peak wavelengths for quantum dot chains grown on patterns oriented along the [011], [01 ?1], [011] and [001] directions. Furthermore, we identify the crystal facets that form the sidewalls of the grooves in the differently oriented patterns after capping and show that the existence of (411)A sidewalls causes reduction of the QD density as well as sidewall roughening. 相似文献
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Miretta Tommila Anne Jokilammi Perttu Terho Timothy Wilson Risto Penttinen Erika Ekholm 《Journal of the Royal Society Interface》2009,6(39):873-880
The presence of bone-marrow-derived stem cells was investigated in a wound-healing model where subcutaneously implanted cellulose sponges were used to induce granulation tissue formation. When cellulose was coated with hydroxyapatite (HA), the sponges attracted circulating haemopoietic and mesenchymal progenitor cells more efficiently than uncoated cellulose. We hypothesized that the giant cells/macrophages of HA-coated sponges recognize HA as foreign material, phagocyte or hydrolyse it and release calcium ions, which are recognized by the calcium-sensing receptors (CaRs) expressed on many cells including haemopoietic progenitors. Our results showed, indeed, that the HA-coated sponges contained more CaR-positive cells than untreated sponges. The stem cells are, most probably, responsible for the richly vascularized granulation tissue formed in HA-coated sponges. This cell-guiding property of HA-coated cellulose might be useful in clinical situations involving impaired wound repair. 相似文献
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