Publications by authors named "Im Taek Yoon"

3 Publications

  • Page 1 of 1

Polarity Control of ZnO Films Grown on Ferroelectric (0001) LiNbO Substrates without Buffer Layers by Pulsed-Laser Deposition.

Nanomaterials (Basel) 2020 Feb 22;10(2). Epub 2020 Feb 22.

Department of Physics, Dongguk University, 26 Phildong 3ga, Chung gu, Seoul 100-715, Korea.

For this study, polarity-controlled ZnO films were grown on lithium niobate (LiNbO) substrates without buffer layers using the pulsed-laser deposition technique. The interfacial structure between the ZnO films and the LiNbO was inspected using high-resolution transmission electron microscopy (HR-TEM) measurements, and X-ray diffraction (XRD) measurements were performed to support these HR-TEM results. The polarity determination of the ZnO films was investigated using piezoresponse force microscopy (PFM) and a chemical-etching analysis. It was verified from the PFM and chemical-etching analyses that the ZnO film grown on the (+z) LiNbO was Zn-polar ZnO, while the O-polar ZnO occurred on the (-z) LiNbO. Further, a possible mechanism of the interfacial atomic configuration between the ZnO on the (+z) LiNbO and that on the (-z) LiNbO was suggested. It appears that the electrostatic stability at the substrate surface determines the initial nucleation of the ZnO films, leading to the different polarities in the ZnO systems.
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http://dx.doi.org/10.3390/nano10020380DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7075319PMC
February 2020

Influence of the Quantum Well Structure and Growth Temperature on a Five-Layer InGaMnAs Quantum Well with an InGaAs Buffer Layer.

J Nanosci Nanotechnol 2018 Jun;18(6):4355-4359

Institute of Microelectronics Technology and High-Purity Materials, Russian Academy of Sciences, Chernogolovka 142432, Russian Federation.

The influence of quantum well structure and growth temperature on a synthesized multilayer system composed of a five-layer InMnGaAs quantum well with an InGaAs buffer layer grown on semi-insulating (100)-oriented substrates prepared by low temperature molecular beam epitaxy was studied. The magnetization measurements using a superconducting quantum interference device indicated the existence of ferromagnetism with a Curie temperature above room temperature in the five-layer InGaMnAs quantum well structure with an InGaAs buffer layer in a GaAs matrix. X-ray diffraction and secondary ion mass spectroscopy measurements confirmed the second phase formation of ferromagnetic GaMn clusters. The ferromagnetism that exists in the five-layer of the InMnGaAs quantum well with the InGaAs buffer layer results from a superposition of the ferromagnetism of the low temperature region from the substitutional Mn ions into Ga sites or interstitial Mn ions as well as the presence of manganese ions dopant clusters such as GaMn clusters.
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http://dx.doi.org/10.1166/jnn.2018.15008DOI Listing
June 2018

GaN nanorods grown on Si (111) substrates and exciton localization.

Nanoscale Res Lett 2011 Jan 12;6(1):81. Epub 2011 Jan 12.

Department of Semiconductor Science, Dongguk University, Seoul, 100-715, South Korea.

We have investigated exciton localization in binary GaN nanorods using micro- and time-resolved photoluminescence measurements. The temperature dependence of the photoluminescence has been measured, and several phonon replicas have been observed at the lower energy side of the exciton bound to basal stacking faults (I1). By analyzing the Huang-Rhys parameters as a function of temperature, deduced from the phonon replica intensities, we have found that the excitons are strongly localized in the lower energy tails. The lifetimes of the I1 and I2 transitions were measured to be < 100 ps due to enhanced surface recombination.PACS: 78.47.+p, 78.55.-m, 78.55.Cr, 78.66.-w, 78.66.Fd.
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http://dx.doi.org/10.1186/1556-276X-6-81DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3212230PMC
January 2011
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