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Structural and Optical Properties of GaN Nanowires Formed on Si(111)
Sangmoon Han,Ilgyu Choi,Jihoon Song,Cheul-Ro Lee,Il-Wook Cho,Mee-Yi Ryu,Jin Soo Kim 한국진공학회(ASCT) 2018 Applied Science and Convergence Technology Vol.27 No.5
We discuss the structural and optical characteristics of GaN nanowires (NWs) grown on Si(111) substrates by a plasmaassisted molecular-beam epitaxy. The GaN NWs with high crystal quality were formed by adopting a new growth approach, so called Ga pre-deposition (GaPD) method. In the GaPD, only Ga was supplied without nitrogen flux on a SiN/Si surface, resulting in the formation of Ga droplets. The Ga droplets were used as initial nucleation sites for the growth of GaN NWs. The GaN NWs with the average heights of 60.10 to 214.62 nm obtained by increasing growth time. The hexagonal-shaped top surfaces and facets were observed from the field-emission electron microscope images of GaN NWs, indicating that the NWs have the wurtzite (WZ) crystal structure. Strong peaks of GaN (0002) corresponding to WZ structures were also observed from double crystal x-ray diffraction rocking curves of the NW samples. At room temperature, free-exciton emissions were observed from GaN NWs with narrow linewidth broadenings, indicating to the formation of high-quality NWs.
Structural and Optical Properties of GaN Nanowires Formed on Si(111)
Han, Sangmoon,Choi, Ilgyu,Song, Jihoon,Lee, Cheul-Ro,Cho, Il-Wook,Ryu, Mee-Yi,Kim, Jin Soo The Korean Vacuum Society 2018 Applied Science and Convergence Technology Vol.27 No.5
We discuss the structural and optical characteristics of GaN nanowires (NWs) grown on Si(111) substrates by a plasma-assisted molecular-beam epitaxy. The GaN NWs with high crystal quality were formed by adopting a new growth approach, so called Ga pre-deposition (GaPD) method. In the GaPD, only Ga was supplied without nitrogen flux on a SiN/Si surface, resulting in the formation of Ga droplets. The Ga droplets were used as initial nucleation sites for the growth of GaN NWs. The GaN NWs with the average heights of 60.10 to 214.62 nm obtained by increasing growth time. The hexagonal-shaped top surfaces and facets were observed from the field-emission electron microscope images of GaN NWs, indicating that the NWs have the wurtzite (WZ) crystal structure. Strong peaks of GaN (0002) corresponding to WZ structures were also observed from double crystal x-ray diffraction rocking curves of the NW samples. At room temperature, free-exciton emissions were observed from GaN NWs with narrow linewidth broadenings, indicating to the formation of high-quality NWs.
Han, Sangmoon,Lee, Seoung-Ki,Choi, Ilgyu,Song, Jihoon,Lee, Cheul-Ro,Kim, Kangmin,Ryu, Mee-Yi,Jeong, Kwang-Un,Kim, Jin Soo American Chemical Society 2018 ACS APPLIED MATERIALS & INTERFACES Vol.10 No.44
<P>In this study, we report highly efficient and flexible photosensors with GaN nanowires (NWs) horizontally embedded in a graphene sandwich structure fabricated on polyethylene terephthalate. GaN NWs and the graphene sandwich structure are used as light-absorbing media and the channel for carrier movement, respectively. To form uniform high-quality crystalline GaN NWs on Si(111) substrates, the initial nucleation behavior of the NWs was manipulated by applying the new growth technique of Ga predeposition. High-resolution transmission electron microscopic images obtained along the vertical direction of GaN NWs showed that stacking faults, typically observed in Si-based (In,Ga)As NWs, were rare. Consequently, narrow and strong optical emission was observed from the GaN NWs at wavelengths of 365.12 nm at 300 K. The photocurrent and photoresponsivity of the flexible photosensor with 802 nm long GaN NWs horizontally embedded in the graphene sandwich channel were measured as 9.17 mA and 91.70 A/W, respectively, at the light intensity of 100 mW/cm<SUP>2</SUP>, which are much higher than those previously reported. The high optical-to-electrical conversion characteristics of our flexible photosensors are attributed to the increase in the effective interface between the light-absorbing media and the carrier channel by the horizontal distribution of the GaN NWs within the graphene sandwich structure. After 200 cyclic-bending test of the GaN NW photosensor at the strain of 3%, the photoresponsivity under strain was measured as 89.04 A/W at 100 mW/cm<SUP>2</SUP>, corresponding to 97.1% of the photoresponsivity obtained before bending. The photosensor proposed in this study is relatively simple in device design and fabrication, and it requires no sophisticated nanostructural design to minimize the resistance to metal contacts.</P> [FIG OMISSION]</BR>
Formation Mechanism of GaN Nanowires with Various Shapes on Si(111)
Noh Siyun,Han Sangmoon,Choi Ilgyu,Kim Jin Soo,Ryu Mee-Yi 한국물리학회 2020 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.77 No.3
We discuss the formation mechanism of GaN nanowires (NWs) with various shapes grown on Si(111) by using a plasma-assisted molecular-beam epitaxy. The GaN NWs have not only symmetrical structures but also various features such as reverse-mesa and reverse-funnel shapes. To manipulate the shape of GaN NWs, we controlled the growth kinetics of gallium (Ga) atoms by varying V/III ratio, defined as the ratio of the nitrogen (N) flux to the Ga flux, and the growth time. Narrow linewidth broadenings of the x-ray diffraction rocking curves and the coherent crystal structure, which are confirmed by using Cs-corrected transmission electron microscope images, indicate the formation of highly crystalline GaN NWs. The formation of GaN NWs, particularly reverse-funnel shaped NWs (RFS-NWs), can be explained by using the so-called wedding-cake growth mechanism, which is related to a reduction in the number of Ga atoms reaching the top surfaces of the GaN NWs from the surface of SiNx/Si(111) as the height of the GaN NWs increases. Photoluminescence spectra from the GaN RFS-NWs show a double-peak feature at wavelengths of 361.79 and 373.58 nm, which is attributed to two different widths of the GaN NWs in the vertical direction.
Do-Not-Resuscitate 결정의도 관련 연구경향
김미지(Kim, Miji),노상미(Noh, Sangmi),류은정(Ryu, Eunjung),신상문(Shin, Sangmoon) 대한종양간호학회 2014 Asian Oncology Nursing Vol.14 No.4
Purpose: The purpose of this study was to identify a research trend of studies related to the Do-Not-Resuscitate (DNR) decision making process in Korea. Methods: Assessing through five computerized databases, 889 studies were reviewed and of these 32 were included. An integrative literature review and text network analysis were applied to examine the research. The keywords from each article’s abstracts were extracted by using a program, KrKwic. Results: The number of studies on DNR decision has been increasing, especially since 2011. A descriptive study design (59%) was most commonly used in the research. In relation to factors affecting DNR decision, 97% of the studies stated patient factors and 66% stated family factors. ‘Patient’, ‘DNR’, ‘decision’, ‘treatment’, ‘life’, ‘family’ were the major keywords, and ‘patient’ and ‘care’ were dominant keywords that ranked high in coappearance frequency. Conclusion: Studies related to DNR decision have been increasing, and themes of the studies have also been broader. Further research is required to investigate factors affecting DNR decision in specific populations such as cancer patients, the elderly, patients with end-stage of chronic diseases etc. Moreover, a comparative study is necessary to define differences of research trends related to DNR decision making process between Korea and other countries.
Preparation of large Cu3Sn single crystal by Czochralski method
Kong Minsik,Park Sang-Eon,Kim Hye Jung,Song Sehwan,Ryu Dong-Choon,Kang Baekjune,Sohn Changhee,Kim Hyun Jung,Kim Youngwook,Yoon Sangmoon,Go Ara,Jeen Hyoungjeen,Park Sungkyun,Jeong Se-Young,Kang Chang-J 한국물리학회 2022 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.81 No.7
Cu3Sn was recently predicted to host topological Dirac fermions, but related research is still in its infancy. The growth of large and high-quality Cu3Sn single crystals is, therefore, highly desired to investigate the possible topological properties. In this work, we report the single crystal growth of Cu3Sn by Czochralski (CZ) method. Crystal structure, chemical composition, and transport properties of Cu3Sn single crystals were analyzed to verify the crystal quality. Notably, compared to the mm-sized crystals from a molten Sn fux, the cm-sized crystals obtained by the CZ method are free from contamination from fux materials, paving the way for the follow-up works.