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Injun Jeon,Jin Hyun Hwang,Tae Gyun Kim,Linghong Yin,이형우,Jong Pil Kim,Hyung Soo Ahn,조채용 한양대학교 세라믹연구소 2021 Journal of Ceramic Processing Research Vol.22 No.2
Peony flower-like γ-Ga2O3 nanosheets (γ-Ga2O3 NSs) were synthesized and carbon layers were coated on their surfaces usinga simple hydrothermal process with subsequent carbonization. The γ-Ga2O3 NSs comprised ultrathin layers, which are tensof nanometers in thickness. The carbon-coated γ-Ga2O3 NS (γ-Ga2O3@C NS) electrode exhibited a specific capacity of 598mAh g−1 at 200 cycles, at a current density of 0.5 A g−1, higher than that of γ-Ga2O3 NSs (60 mAh g−1). Furthermore, a specificcapacity of 100 mAh g−1 at 5 A g−1 was achieved owing to the low charge transfer resistance through the carbon layers. Thisstudy suggests that two-dimensional γ-Ga2O3@C NSs with both large specific area and high charge carrier transport arepromising active materials for lithium-ion battery anodes with better electrochemical performance.
광전음극 소자용 GaAs/AlGaAs 구조의 LPE 성장
배숭근,전인준,김경화,Bae, Sung Geun,Jeon, Injun,Kim, Kyoung Hwa 한국결정성장학회 2017 韓國結晶成長學會誌 Vol.27 No.6
본 논문에서는 광전 음극 이미지 센서로 사용될 수 있는 광소자용 재료로 III-V 족 화합물 반도체인 GaAs/AlGaAs 다층 구조를 LPE(Liquid Phase Epitaxy) 방법에 의해 성장하였다. n형 GaAs 기판 위에 수십 nm의 GaAs 완충층을 형성 한 후 Zn가 도핑된 p-AlGaAs 에칭 정지 층(etching stop layer)과 Zn가 도핑된 p-GaAs 층 그리고 Zn가 도핑된 p-AlGaAs 층을 성장하였다. 성장된 시료의 특성을 조사하기 위하여 주사전자현미경(SEM)과 이차이온질량분석기(SIMS) 그리고 홀(Hall) 측정 장치 등을 이용하여 GaAs/AlGaAs 다층 구조를 분석하였다. 그 결과 $1.25mm{\times}25mm$의 성장 기판에서 거울면(mirror surface)을 가지는 p-AlGaAs/p-GaAs/p-AlGaAs 다층 구조를 확인할 수 있었으며, Al 조성은 80 %로 측정 되었다. 또한 p-GaAs층의 캐리어 농도는 $8{\times}10^{18}/cm^2$ 범위까지 조절할 수 있음을 확인하였다. 이 결과로부터 LPE 방법에 의해 성장된 p-AlGaAs/p-GaAs/AlGaAs 다층 구조는 광전 음극 이미지 센서의 소자로서 이용될 수 있을 것으로 기대한다. In this paper, GaAs/AlGaAs multi-layer structure was grown by liquid phase epitaxy with graphite sliding boat, which can be used as a device structure of a photocathode image sensor. The multi-layer structure was grown on an n-type GaAs substrate in the sequence as follows: GaAs buffer layer, Zn-doped p-type AlGaAs layer as etching stop layer, Zn-doped p-type GaAs layer, and Zn-doped p-type AlGaAs layer. The Characteristics of GaAs/AlGaAs structures were analyzed by using scanning electron microscope (SEM), secondary ion mass spectrometer (SIMS) and hall measurement. The SEM images shows that the p-AlGaAs/p-GaAs/p-AlGaAs multi-layer structure was grown with a mirror-like surface on a whole ($1.25mm{\times}25mm$) substrate. The Al composition in the AlGaAs layer was approximately 80 %. Also, it was confirmed that the free carrier concentration in the p-GaAs layer can be adjusted to the range of $8{\times}10^{18}/cm^2$ by hall measurement. In the result, it is expected that the p-AlGaAs/p-GaAs/p-AlGaAs multi-layer structure grown by the LPE can be used as a device structure of a photoelectric cathode image sensor.
Yin, Linghong,Gao, Ying Jun,Jeon, Injun,Yang, Hang,Kim, Jong-Pil,Jeong, Se Young,Cho, Chae Ryong Elsevier 2019 CHEMICAL ENGINEERING JOURNAL -LAUSANNE- Vol.356 No.-
<P><B>Abstract</B></P> <P>We synthesized nanoarchitectures comprising γ-Fe<SUB>2</SUB>O<SUB>3</SUB>@C nanofibers with one-dimensional rice-panicle-like morphologies via a facile electrospinning and annealing process for use as anodes in lithium-ion batteries (LIBs). A thin carbon layer grown on the surface of γ-Fe<SUB>2</SUB>O<SUB>3</SUB> provides a synergistic effect to relieve the stress and alleviate the volume expansion occurring during the lithium-ion insertion/extraction process. The unique structure not only offers good electron transport routes, but also enhances the lithium-ion conductive channels, resulting in excellent electrochemical activity and electrical conductivity of the LIB anode material. A high reversible specific capacity of 1252 mAh g<SUP>−1</SUP> was achieved after 200 cycles even at the current density of 10 A g<SUP>−1</SUP>. When examined at the scan rate of 5 mV s<SUP>−1</SUP>, a high capacitive contribution ratio of 88.5% was achieved. The short lithium-ion diffusion pathways avoid structural damage to the active material and provide excellent rate capacities. This work suggests a new method to improve the electrochemical performance of LIBs through the synergistic design of uniquely structured metal oxides.</P> <P><B>Highlights</B></P> <P> <UL> <LI> 1D rice-panicle-like γ-Fe<SUB>2</SUB>O<SUB>3</SUB>@C nanofibers are successfully fabricated. </LI> <LI> Sufficient active sites for lithium storage are provided by unique structure. </LI> <LI> High rate capability of γ-Fe<SUB>2</SUB>O<SUB>3</SUB>@C electrode was achieved. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>One-dimensional γ-Fe<SUB>2</SUB>O<SUB>3</SUB>@C NFs with rice-panicle-like morphology was successfully fabricated via a facile electrospinning and post annealing process. A stable and high reversible specific capacity of 1252 mAh g<SUP>−1</SUP> was achieved after 200 cycles at a current density of 10 A g<SUP>−1</SUP>, which was ascribed to the synergistic effect of a novel combination between ultrathin carbon layer and γ-Fe<SUB>2</SUB>O<SUB>3</SUB> nanocrystallites.</P> <P>[DISPLAY OMISSION]</P>
HVPE 방법에 의해 성장된 graded AlGaN 에피층의 특성
이찬빈,전헌수,이찬미,전인준,양민,이삼녕,안형수,김석환,유영문,Lee, Chanbin,Jeon, Hunsoo,Lee, Chanmi,Jeon, Injun,Yang, Min,Yi, Sam Nyung,Ahn, Hyung Soo,Kim, Suck-Whan,Yu, Young Moon,Sawaki, Nobuhiko 한국결정성장학회 2015 한국결정성장학회지 Vol.25 No.2
Compositionally graded AlGaN epilayer was grown by HVPE (hydride vapor phase epitaxy) on (0001) c-plane sapphire substrate. During the growth of graded AlGaN epilayer, the temperatures of source and the growth zone were set at $950^{\circ}C$ and $1145^{\circ}C$, respectively. The growth rate of graded AlGaN epilayer was about 100 nm/hour. The changing of Al contentes was investigated by field emission scanning electron microscope (FE-SEM) and energy dispersive spectroscopy (EDS). From the result of atomic force microscope (AFM), the average of roughness in 2 inch substrate of graded AlGaN epilayer was a few nanometers scale. X-ray diffraction (XRD) with the result that the AlGaN (002) peak ($Al_{0.74}Ga_{0.26}N$) and AlN (002) peak were appeared. It seems that the graded AlGaN epilayer was successfully grown by the HVPE method. From these results, we expect to use of the graded AlGaN epilayer grown by HVPE for the application of electron and optical devices. 본 논문에서는 Al 조성이 점진적으로 변화된 AlGaN 에피층을 HVPE (hydride vapor phase epitaxy) 방법에 의하여 성장하였다. 소스영역의 온도는 $950^{\circ}C$, 성장 영역의 온도는 $1145^{\circ}C$에서 연속적으로 (0001) 사파이어 기판위에 성장되었고, AlGaN 에피층은 시간당 100 nm의 성장률을 보였다. FE-SEM 측정과 EDS 측정으로부터 성장층의 Al 변화를 확인하였으며, AFM 측정결과 2인치 기판위에 성장된 graded AlGaN 에피층의 거칠기는 수십 nm였다. Al 조성의 변화는 XRD 측정에 의하여 확인하였으며, Al 조성 74 %의 (002) AlGaN의 주피크 관측과 함께 연속적으로 (002) AlN 층의 피크가 확인되었다. 이는 하나의 층에 사파이어 기판으로부터 Al 조성이 점진적으로 변화하는 에피층을 HVPE 방법으로 얻었음을 증명하며, 이 결과로부터 다양한 광소자 및 전자소자의 응용이 기대된다.
고효율 파워 반도체 소자를 위한 Mg-doped AlN 에피층의 HVPE 성장
배숭근,전인준,양민,이삼녕,안형수,전헌수,김경화,김석환,Bae, Sung Geun,Jeon, Injun,Yang, Min,Yi, Sam Nyung,Ahn, Hyung Soo,Jeon, Hunsoo,Kim, Kyoung Hwa,Kim, Suck-Whan 한국결정성장학회 2017 韓國結晶成長學會誌 Vol.27 No.6
AlN는 넓은 밴드 갭 및 높은 열전도율로 인해 넓은 밴드 갭 및 고주파 전자 소자로 유망한 재료이다. AlN은 전력 반도체의 재료로서 더 큰 항복전압과 고전압에서의 더 작은 특성저항의 장점을 가지고 있다. 높은 전도도를 갖는 p형 AlN 에피층의 성장은 AlN 기반 응용 제품 제조에 중요하다. 본 논문에서는 Mg이 도핑된 AlN 에피층을 혼합 소스 HVPE에 의해 성장하였다. Al 및 Mg 혼합 금속은 Mg-doped AlN 에피 층의 성장을 위한 소스 물질로 사용하였다. AlN 내의 Mg 농도는 혼합 소스에서 Mg 첨가 질량의 양을 조절함으로써 제어되었다. 다양한 Mg 농도를 갖는 AlN 에피 층의 표면 형태 및 결정 구조는 FE-SEM 및 HR-XRD에 의해 조사하였다. Mg-doped AlN 에피 층의 XPS 스펙트럼으로 부터 혼합 소스 HVPE에 의해 Mg을 AlN 에피 층에 도핑할 수 있음을 증명하였다. AlN is a promising material for wide band gap and high-frequency electronics device due to its wide bandgap and high thermal conductivity. AlN has advantages as materials for power semiconductors with a larger breakdown field, and a smaller specific on-resistance at high voltage. The growth of a p-type AlN epilayer with high conductivity is important for a manufacturing an AlN-based applications. In this paper, Mg doped AlN epilayers were grown by a mixed-source HVPE. Al and Mg mixture were used as source materials for the growth of Mg-doped AlN epilayers. Mg concentration in the AlN was controlled by modulating the quantity of Mg source in the mixed-source. Surface morphology and crystalline structure of AlN epilayers with different Mg concentrations were characterized by FE-SEM and HR-XRD. XPS spectra of the Mg-doped AlN epilayers demonstrated that Mg was doped successfully into the AlN epilayer by the mixed-source HVPE.
Gao, Yingjun,Yin, Linghong,Kim, Su Jae,Yang, Hang,Jeon, Injun,Kim, Jong-Pil,Jeong, Se Young,Lee, Hyung Woo,Cho, Chae Ryong Pergamon Press 2019 Electrochimica Acta Vol. No.
<P><B>Abstract</B></P> <P>We synthesized polycrystalline ZnFe<SUB>2</SUB>O<SUB>4</SUB> nanofibers via a facile electrospinning and annealing process. The ZnFe<SUB>2</SUB>O<SUB>4</SUB> nanofibers exhibit continuous frameworks and uniform porosity through the abrupt combustion of the polymer and crystallization of inorganic elements. This well-defined structure and morphology facilitates Li<SUP>+</SUP> transport, enhances the effective contact area with the electrolyte, and offers abundant active sites. For the ZnFe<SUB>2</SUB>O<SUB>4</SUB> nanofiber anode, the reversible capacity reaches 753 mAh g<SUP>−1</SUP> after 200 cycles at the high current density of 5 A g<SUP>−1</SUP> and the anode shows excellent rate performance. The enhanced electrochemical performance can be attributed to the one-dimensional nanostructure and shortened diffusion pathways, which ensure full conversion reactions during lithiation-delithiation between Zn, Fe, and Li<SUP>+</SUP>, relieve volume expansion, and prevent pulverization/aggregation upon prolonged cycling at high current densities. Thus, we believe that ZnFe<SUB>2</SUB>O<SUB>4</SUB> nanofibers present great potential as anode materials for Li-ion batteries.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Facile electrospinning and annealing process to synthesis polycrystalline ZnFe<SUB>2</SUB>O<SUB>4</SUB> nanofibers. </LI> <LI> Continuous structural framework with uniform pores on the surface. </LI> <LI> High specific reversible capacity and enhanced cycle stability of ZnFe<SUB>2</SUB>O<SUB>4</SUB> NFs due to well-defined morphology. </LI> </UL> </P>