The SnSe single crystal shows an outstanding figure of merit (ZT) of 2.6 at 973 K; thus, it is considered to be a promising thermoelectric material. However, the mass production of SnSe single crystals is difficult, and their mechanical properties are poor. Alternatively, we can use polycrystalline SnSe powder, which has better mechanical properties. In this study, surface modification by atomic layer deposition (ALD) is chosen to increase the ZT value of SnSe polycrystalline powder. SnSe powder is ground by a ball mill. An ALD coating process using a rotary-type reactor is adopted. ZnO thin films are grown by 100 ALD cycles using diethylzinc and H₂O as precursors at 100°C. ALD is performed at rotation speeds of 30, 40, 50, and 60 rpm to examine the effects of rotation speed on the thin film characteristics. The physical and chemical properties of ALD-coated SnSe powders are characterized by scanning and tunneling electron microscopy combined with energy-dispersive spectroscopy. The results reveal that a smooth oxygenrich ZnO layer is grown on SnSe at a rotation speed of 30 rpm. This result can be applied for the uniform coating of a ZnO layer on various powder materials.

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• Fabrication of Multilayer Core-Shell Structure for High Power Factor in Bi2Te2.7Se0.3 Thermoelectrics
  Su Min Eun, Jin Kyeong Shin, Se Been Jeong, Eui Seon Lee, Sung-Tag Oh, Byung Joon Choi
  Journal of Powder Materials.2026; 33(4): 299.     CrossRef
• Thermal Confinement and Filtering Effect of SnSe by Insertion of Atomic-Layer-Deposited ZnO Interfacial Layer
  Myeong Jun Jung, Su Min Eun, Hogyoung Kim, Seong Keun Kim, Jongmin Byun, Byung Joon Choi
  Korean Journal of Chemical Engineering.2025; 42(14): 3545.     CrossRef

In this study, (GaN)_1-x(ZnO)_x solid solution nanoparticles with a high zinc content are prepared by ultrasonic spray pyrolysis and subsequent nitridation. The structure and morphology of the samples are investigated by X-ray diffraction (XRD), field-emission scanning electron microscopy, and energy-dispersive X-ray spectroscopy. The characterization results show a phase transition from the Zn and Ga-based oxides (ZnO or ZnGa₂O₄) to a (GaN)_1-x (ZnO)_x solid solution under an NH3 atmosphere. The effect of the precursor solution concentration and nitridation temperature on the final products are systematically investigated to obtain (GaN)_1-x(ZnO)_x nanoparticles with a high Zn concentration. It is confirmed that the powder synthesized from the solution in which the ratio of Zn and Ga was set to 0.8:0.2, as the initial precursor composition was composed of about 0.8-mole fraction of Zn, similar to the initially set one, through nitriding treatment at 700°C. Besides, the synthesized nanoparticles exhibited the typical XRD pattern of (GaN)_1-x(ZnO)_x, and a strong absorption of visible light with a bandgap energy of approximately 2.78 eV, confirming their potential use as a hydrogen production photocatalyst.

We report on an all-solution-processed hydrothermal method to control the morphology of ZnO nanostructures on Si substrates from three-dimensional hemispherical structures to two-dimensional thin film layers, by controlling the seed layer and the molar contents of surfactants during their primary growth. The size and the density of the seed layer, which is composed of ZnO nanodots, change with variation in the solute concentration. The ZnO nanodots act as heterogeneous nucleation sites for the main ZnO nanostructures. When the seed layer concentration is increased, the ZnO nanostructures change from a hemispherical shape to a thin film structure, formed by densely packed ZnO hemispheres. In addition, the morphology of the ZnO layer is systematically controlled by using trisodium citrate, which acts as a surfactant to enhance the lateral growth of ZnO crystals rather than a preferential one-dimensional growth along the c-direction. X-ray diffraction and energy dispersive X-ray spectroscopy results reveal that the ZnO structure is wurtzite and did not incorporate any impurities from the surfactants used in this study.

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• La-doped p-type ZnO nanowire with enhanced piezoelectric performance for flexible nanogenerators
  Leeseung Kang, HyeLan An, Ji Young Park, Myung Hwan Hong, Sahn Nahm, Chan Gi Lee
  Applied Surface Science.2019; 475: 969.     CrossRef

We report on the successful fabrication of ZnO nanorod (NR)/polystyrene (PS) nanosphere hybrid nanostructure by combining drop coating and hydrothermal methods. Especially, by adopting an atomic layer deposition method for seed layer formation, very uniform ZnO NR structure is grown on the complicated PS surfaces. By using zinc nitrate hexahydrate [Zn(NO₃)₂ ·6H₂O] and hexamine [(CH₂)₆N₄] as sources for Zn and O in hydrothermal process, hexagonal shaped single crystal ZnO NRs are synthesized without dissolution of PS in hydrothermal solution. X-ray diffraction results show that the ZnO NRs are grown along c-axis with single crystalline structure and there is no trace of impurities or unintentionally formed intermetallic compounds. Photoluminescence spectrum measured at room temperature for the ZnO NRs on flat Si and PS show typical two emission bands, which are corresponding to the band-edge and deep level emissions in ZnO crystal. Based on these structural and optical investigations, we confirm that the ZnO NRs can be grown well even on the complicated PS surface morphology to form the chestnut-shaped hybrid nanostructures for the energy generation and storage applications.

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  Jung-Hwan Lee, Gun-Sub Lee, Eung-Nam Park, Dong-Hyeon Jo, So-Won Kim, Hee-Chul Lee
  Materials.2023; 16(5): 2099.     CrossRef
• Rapid consolidation of nanostuctured WC-FeAl3 by pulsed current activated heating and its mechanical properties
  In-Jin Shon, Seok-Jae Lee
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  Applied Surface Science.2017; 415: 2.     CrossRef
• Morphology Control of ZnO Nanostructures by Surfactants During Hydrothermal Growth
  Il-Kyu Park
  Journal of Korean Powder Metallurgy Institute.2016; 23(4): 270.     CrossRef

We report on the succesful fabrication of ZnO nanorod (NR)-based robust piezoelectric nanogenerators (PNGs) by using Cu foil substrate. The ZnO NRs are successfully grown on the Cu foil substrate by using all solution based method, a two step hydrothermal synthesis. The ZnO NRs are grown along c-axis well with an average diameter of 75~80 nm and length of 1~1.5 μm. The ZnO NRs showed abnormal photoluminescence specrta which is attributed from surface plasmon resonance assistant enhancement at specific wavelength. The PNGs on the SUS substrates show typical piezoelectric output performance which showing a frequency dependent voltage enhancement and polarity dependent charging and discharging characteristics. The output voltage range is 0.79~2.28 V with variation of input strain frequency of 1.8~3.9 Hz. The PNG on Cu foil shows reliable output performance even at the operation over 200 times without showing degradation of output voltage. The current output from the PNG is 0.7 μA/cm² which is a typical output range from the ZnO NR-based PNGs. These performance enhancement is attributed from the high flexibility, high electrical conductivity and excellent heat dissipation properties of the Cu foil as a substrate.

Citations

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• Fabrication of a Graphene/ZnO based p-n junction device and its ultraviolet photoresponse properties
  Young-Tae Kwon, Sung-Oong Kang, Ji-Ae Cheon, Yoseb Song, Jong-Jin Lee, Yong-Ho Choa
  Applied Surface Science.2017; 415: 2.     CrossRef
• Fabrication of Porous Polytetrafluoroethylene thin Film from Powder Dispersion-solution for Energy Nanogenerator Applications
  Il-Kyu Park
  Journal of Korean Powder Metallurgy Institute.2017; 24(2): 102.     CrossRef
• Morphology Control of ZnO Nanostructures by Surfactants During Hydrothermal Growth
  Il-Kyu Park
  Journal of Korean Powder Metallurgy Institute.2016; 23(4): 270.     CrossRef
• Fabrication of ZnO Nanorod/polystyrene Nanosphere Hybrid Nanostructures by Hydrothermal Method for Energy Generation Applications
  Seong-Ho Baek, Il-Kyu Park
  Journal of Korean Powder Metallurgy Institute.2015; 22(6): 391.     CrossRef