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( Sang Hyeok Im ),( Dong Hwan Kim ),( Young Hoon La ),( Nam Jin Kim ),( Cha Won Hwang ),( Jae Min Cha ),( Bong Ki Ryu ) 대한금속재료학회 ( 구 대한금속학회 ) 2010 재료마당 Vol.23 No.3
This study looks at crystallization and sintering behavior in B2O3 containing Li2O-Al2O3-SiO2 glass powder. The sintered sample was produced with glass powders measuring 44 μm. The relative density and transmittance of the sintered samples showed the highest value at the temperature of 650°C. At temperatures higher than 650°C, crystal growth occurred to decrease the densification of B2O3-Li2O-Al2O3-SiO2 (BLAS) glass powder. The main crystalline phase in the glass powder was a-spodumene. From non-isothermal differential thermal analysis, the crystallization of particles (Φ=44 μm) was observed at 640°C to 684°C with respect to the heating rate. The activation energy of crystallization (E(C)) and the Avrami constant (n) calculated by Kissinger and Ozawa equations indicated that the surface and the bulk crystallization occurred simultaneously in the glass. The optimum sintering temperature of this glass powder was 650°C without crystal growth of β-spodumene, although nucleation or nano-crystal growth occurred.
6.5% efficient perovskite quantum-dot-sensitized solar cell
Im, Jeong-Hyeok,Lee, Chang-Ryul,Lee, Jin-Wook,Park, Sang-Won,Park, Nam-Gyu Royal Society of Chemistry 2011 Nanoscale Vol.3 No.10
<P>Highly efficient quantum-dot-sensitized solar cell is fabricated using <I>ca.</I> 2–3 nm sized perovskite (CH<SUB>3</SUB>NH<SUB>3</SUB>)PbI<SUB>3</SUB> nanocrystal. Spin-coating of the equimolar mixture of CH<SUB>3</SUB>NH<SUB>3</SUB>I and PbI<SUB>2</SUB> in γ-butyrolactone solution (perovskite precursor solution) leads to (CH<SUB>3</SUB>NH<SUB>3</SUB>)PbI<SUB>3</SUB> quantum dots (QDs) on nanocrystalline TiO<SUB>2</SUB> surface. By electrochemical junction with iodide/iodine based redox electrolyte, perovskite QD-sensitized 3.6 μm-thick TiO<SUB>2</SUB> film shows maximum external quantum efficiency (EQE) of 78.6% at 530 nm and solar-to-electrical conversion efficiency of 6.54% at AM 1.5G 1 sun intensity (100 mW cm<SUP>−2</SUP>), which is by far the highest efficiency among the reported inorganic quantum dot sensitizers.</P> <P>Graphic Abstract</P><P>Highly efficient perovskite quantum-dot-sensitized solar cell. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c1nr10867k'> </P>
1/<i>f</i> noise characteristics of AlGaN/GaN HEMTs with periodically carbon-doped GaN buffer layer
Im, Ki-Sik,Choi, Jinseok,Hwang, Youngmin,An, Sung Jin,Roh, Jea-Seung,Kang, Seung-Hyeon,Lee, Jun-Hyeok,Lee, Jung-Hee Elsevier 2019 MICROELECTRONIC ENGINEERING Vol.215 No.-
<P><B>Abstract</B></P> <P>We investigate the DC and 1/<I>f</I> noise properties in Al<SUB>0.25</SUB>Ga<SUB>0.75</SUB>N/GaN high-electron mobility transistors (HEMTs) with two types of 2 μm-thick periodically carbon-doped GaN buffer layer (PC-doped GaN buffer) with and without inserting the 30 nm-thick Al<SUB>0.05</SUB>Ga<SUB>0.95</SUB>N back barrier layer between the GaN channel layer and the PC-doped GaN buffer. The PC-doped GaN buffer layer consists of multiple layers of 12 nm-thick C-doped GaN layer with doping concentration of 1 × 10<SUP>18</SUP> cm<SUP>−3</SUP> and 50 nm-thick undoped GaN layer with unintentional n-typing concentration of 2 × 10<SUP>16</SUP> cm<SUP>−3</SUP>. A reference AlGaN/GaN HEMT with 2 μm-thick highly-resistive GaN buffer layer without C-doping is also fabricated for comparison. Similarly to the reference AlGaN/GaN HEMT, the AlGaN/GaN HEMTs with PC-doped GaN buffer show typical 1/<I>f</I> noise characteristics mainly due to the trapping effects at the AlGaN/GaN interface from subthreshold region to strong-accumulation region, which indicates that the deep trapping effects in the PC-doped GaN buffer layer is negligible, and experience the correlated mobility fluctuations (CMF), which is convinced from the drain current power spectral density (PSD) versus drain current. At off-state (deep-subthreshold region), on the other hand, the HEMTs with the PC-doped GaN buffer layer exhibit 1/<I>f</I> <SUP>2</SUP> noise characteristics, which are closely related to the generation-recombination (g-r) noise caused by the spatial trapping/detrapping process between the deep acceptor in the C-doped layer and the shallow donor in the undoped layer in the PC-doped GaN buffer, while the reference HEMT still shows typical 1/<I>f</I> noise characteristics.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Noise characteristics in AlGaN/GaN HEMTs with/without PC-doped buffer layer were investigated. </LI> <LI> PC-doped buffer layer consists of 12 nm-thick carbon-doped GaN and 50 nm-thick un-doped GaN. </LI> <LI> All devices exhibited 1/<I>f</I> noise properties and CMFs from subthreshold to strong-accumulation. </LI> <LI> At off-state, PC-doped buffer devices exhibited 1/<I>f</I> <SUP>2</SUP> noise properties at frequency > 40 Hz. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>