scispace - formally typeset
Search or ask a question
Author

Jihoon Lee

Bio: Jihoon Lee is an academic researcher from Kwangwoon University. The author has contributed to research in topics: Quantum dot & Dewetting. The author has an hindex of 25, co-authored 175 publications receiving 2215 citations. Previous affiliations of Jihoon Lee include Korea Electrotechnology Research Institute & University of Arkansas.


Papers
More filters
Journal ArticleDOI
TL;DR: In this paper, self-assembled InGaAs quantum dot molecules (QDMs) were studied and the number of QDs per GaAs mound ranges from two to six (bi-QDm to hexa-Qdm).
Abstract: Several distinctive self-assembled InGaAs quantum dot molecules (QDMs) are studied. The QDMs self-assemble around nanoscale-sized GaAs moundlike templates fabricated by droplet homoepitaxy. Depending on the specific InAs monolayer coverage, the number of QDs per GaAs mound ranges from two to six (bi-QDMs to hexa-QDMs). The Ga contribution from the mounds is analyzed in determining the morphologies of the QDMs, with respect to the InAs coverages ranging between 0.8 and 2.4 ML. Optical characterization shows that the resulting nanostructures are high-quality nanocrystals.

121 citations

Journal ArticleDOI
TL;DR: In this paper, a growth technique combining droplet epitaxy and molecular beam epitaxy (MBE) is developed to obtain a low density of InAs quantum dots (QDs) on GaAs nanoholes.
Abstract: A growth technique combining droplet epitaxy and molecular beam epitaxy (MBE) is developed to obtain a low density of InAs quantum dots (QDs) on GaAs nanoholes. This growth technique is simple, flexible, and does not require additional substrate processing. It makes possible separate control of the QD density via droplet epitaxy and the QD quality via MBE growth. In this letter the authors report the use of this technique to produce InAs QDs with a low density of 2.7×108cm−2 as well as good photoluminescence properties. The resulting samples are suitable for single QD device fabrication and applications.

70 citations

Journal ArticleDOI
TL;DR: The improved photoresponse with the AgAu alloy NPs is correlated with the simultaneous effect of strong plasmon absorption and scattering, increased injection of hot electrons into the GaN conduction band and reduced barrier height at the alloy Nps/GaN interface.
Abstract: Very small metallic nanostructures, i.e., plasmonic nanoparticles (NPs), can demonstrate the localized surface plasmon resonance (LSPR) effect, a characteristic of the strong light absorption, scattering and localized electromagnetic field via the collective oscillation of surface electrons upon on the excitation by the incident photons. The LSPR of plasmonic NPs can significantly improve the photoresponse of the photodetectors. In this work, significantly enhanced photoresponse of UV photodetectors is demonstrated by the incorporation of various plasmonic NPs in the detector architecture. Various size and elemental composition of monometallic Ag and Au NPs, as well as bimetallic alloy AgAu NPs, are fabricated on GaN (0001) by the solid-state dewetting approach. The photoresponse of various NPs are tailored based on the geometric and elemental evolution of NPs, resulting in the highly enhanced photoresponsivity of 112 A W−1, detectivity of 2.4 × 1012 Jones and external quantum efficiency of 3.6 × 104% with the high Ag percentage of AgAu alloy NPs at a low bias of 0.1 V. The AgAu alloy NP detector also demonstrates a fast photoresponse with the relatively short rise and fall time of less than 160 and 630 ms, respectively. The improved photoresponse with the AgAu alloy NPs is correlated with the simultaneous effect of strong plasmon absorption and scattering, increased injection of hot electrons into the GaN conduction band and reduced barrier height at the alloy NPs/GaN interface.

63 citations

Journal ArticleDOI
TL;DR: In this article, a strain-free GaAs/Al033Ga067As quantum ring solar cells fabricated by droplet epitaxy technique was reported. But the experimental results were limited to a single cell.
Abstract: Droplet epitaxy is a flexible nanomaterial growth technique and is a potential method to fabricate advanced electronic and optoelectronic devices Here, we report strain-free GaAs/Al033Ga067As quantum ring solar cells fabricated by droplet epitaxy technique Photoluminescence is used to study the electronic structure of the lattice-matched GaAs/Al033Ga067As quantum ring solar cells Post-growth thermal annealing is used to improve the optical quality of the solar cell as well as device efficiency A power conversion efficiency of 18% is demonstrated from a prototype quantum ring solar cell This work opens new opportunities for quantum dot solar cells with strain-free nanostructures

61 citations

Journal ArticleDOI
TL;DR: In this paper, the evolution between lattice-matched GaAs/Al0.7As single and double ring-like nanostructures was studied, with an emphasis on the construction and destruction of the observed outer ring.
Abstract: The evolution between lattice-matched GaAs/Al0.3Ga0.7As single and double ring-like nanostructures is studied, with an emphasis on the construction and destruction of the observed outer ring. Using droplet epitaxy, this was achieved by directly controlling the Ga surface diffusion on GaAs(100). Double ring-like nanostructures were observed at relatively low temperatures under a fixed As4 flux (beam equivalent pressure (BEP) of 6.4 µTorr) and at a fixed temperature under a high As4 flux. The construction of the outer ring can be controlled through surface diffusion by varying the substrate temperature or the As4 flux. Single ring-like nanostructures were realized both at relatively high temperatures under a fixed As4 flux, and at low temperatures under a relatively low As4 flux.

58 citations


Cited by
More filters
Journal Article
TL;DR: In the limit of a QD much smaller than the bulk exciton size, the linear spectrum will be a series of lines, and the phonon broadening of these lines is considered.
Abstract: We analyze theoretically the optical properties of ideal semiconductor crystallites so small that they show quantum confinement in all three dimensions [quantum dots (QD's)]. In the limit of a QD much smaller than the bulk exciton size, the linear spectrum will be a series of lines, and we consider the phonon broadening of these lines. The lowest interband transition will saturate like a two-level system, without exchange and Coulomb screening. Depending on the broadening, the absorption and the changes in absorption and refractive index resulting from saturation can become very large, and the local-field effects can become so strong as to give optical bistability without external feedback. The small QD limit is more readily achieved with narrow-band-gap semiconductors.

788 citations

Journal ArticleDOI
TL;DR: QDs are one of the first nanotechnologies to be integrated with the biological sciences and are widely anticipated to eventually find application in a number of commercial consumer and clinical products.
Abstract: This review introduces quantum dots (QDs) and explores their properties, synthesis, applications, delivery systems in biology, and their toxicity. QDs are one of the first nanotechnologies to be integrated with the biological sciences and are widely anticipated to eventually find application in a number of commercial consumer and clinical products. They exhibit unique luminescence characteristics and electronic properties such as wide and continuous absorption spectra, narrow emission spectra, and high light stability. The application of QDs, as a new technology for biosystems, has been typically studied on mammalian cells. Due to the small structures of QDs, some physical properties such as optical and electron transport characteristics are quite different from those of the bulk materials.

450 citations

Journal ArticleDOI
TL;DR: In this article, the formation mechanisms of titanate nanotubes during hydrothermal synthesis are discussed and structural modifications and current progress toward photocatalytic activity of titanates as photocatalyst is summarized.

430 citations

Journal Article
TL;DR: This study highlights a novel, highly active oxygen evolution catalyst and provides novel important insights into the structure and performance of bimetallic oxide OER electrocatalysts in corrosive acidic environments.
Abstract: Mixed bimetallic oxides offer great opportunities for a systematic tuning of electrocatalytic activity and stability. Here, we demonstrate the power of this strategy using well-defined thermally prepared Ir–Ni mixed oxide thin film catalysts for the electrochemical oxygen evolution reaction (OER) under highly corrosive conditions such as in acidic proton exchange membrane (PEM) electrolyzers and photoelectrochemical cells (PEC). Variation of the Ir to Ni ratio resulted in a volcano type OER activity curve with an unprecedented 20-fold improvement in Ir mass-based activity over pure Ir oxide. In situ spectroscopic probing of metal dissolution indicated that, against common views, activity and stability are not directly anticorrelated. To uncover activity and stability controlling parameters, the Ir–Ni mixed thin oxide film catalysts were characterized by a wide array of spectroscopic, microscopic, scattering, and electrochemical techniques in conjunction with DFT theoretical computations. By means of an in...

429 citations

Journal Article
TL;DR: In this paper, the result of the PtSi nanometer thin film based on silicon prepared by the pulsed laser deposition was described and the physical principle, unique characteristics and the proceeding of the study were introduced briefly.
Abstract: The pulsed laser deposition is a new technique for the growth of thin films,which has been attended generally by people recently The physical principle, unique characteristics and the proceeding of the study were introduced briefly In addation, the result of the PtSi nanometer thin film based on silicon prepared by the pulsed laser deposition was describedPULS

392 citations