Synthesis of nanowires and nanotubes

Transcription

1 Synthesis of nanowires and nanotubes Laser-assisted Catalytic Growth Source target with catalyst is evaporated by laser. Nanomaterials are collected on a cold finger. Synthesized semiconductor NWs - Si, Ge, GaN, GaAs, GaP, InP, InAs, ZnS, ZnSe, CdS, CdSe NW

2 Synthesis of NWs Thermal chemical vapor deposition P. Yang, Adv. Funct. Mater. 2002, 12, 323 Mixed source powder is evaporated by heating ZnO Nanowire is grown on the Aucoated Si or Sapphire substrate. ZnO is reduced by C to generate Zn vapor.

3 GaN Nanowire Nanodevice Field effect transistors(fets) based on a GaN nanowire have been fabricated Lieber, Nano lett. 2002, 2, 101 The investigation of the carrier mobility(μ) in these n-type GaN nanowire FETs di dv g C = µ( ) V L 2 sd The slopes depend on electron mobility The electron mobility of nanowire is higher than that of GaN thin film: 소자의응답속도개선

4 Nanoscale Light Emitting Diode (LED) Nature 2001, 409, 66 Multicolor nanowire LED A p-doped Si nanowire (hole) is crossed with three different n-doped (electron) nanowires (GaN, CdS, and InP) When a voltage is applied to the silicon nanowire, current runs into each of the crossed wires causing emission of blue, green and red light at the respective crossing points.

5 Nanowire UV Photodetector and Optical Switches Adv. Mater. 2002, 14, 158 UV Photodetector Reversible optical switch When ZnO nanowires are exposed to UV, resistivity decreases by 4 to 6 orders of magnitude. ON : the UV-exposed conducting state OFF : the insulating state Nanowires can be reversibly switched between the low and high conductivity state.

6 Nanowire nanolasers Science 2001, 292, 1897 Optically pumped nanolaser Schematic drawing <0001> oriented ZnO nanowire arrays LASER Nanolaser Under optical excitation, surfaceemitting lasing action at 385 nm

7 브라운관의내부구조 벽걸이형 TV(FED) 벽걸이형 TV 내부구조 전자총 전자총 array Metal tip 벽걸이형 TV 를위한전계방출소자 (FED) 는브라운관과유사한원리를이용한 평판디스플레이로, 브라운관의높은휘도, 넓은시야각등의특성을유지하면서, 두께가얇고가볍다는장점을가지고있어차세대디스플레이로서주목받고있다. 이소자의핵심기술은전자총소재의개발인데, 최근기존의금속재료대신, 안정성이 뛰어나고, 전자방출효율이좋은탄소나노튜브및 ZnO 나노선등이신소재로서사용되고있다. 특히 3D TV 의경우좌우눈을위한두개의상을보여주어야하기때문에화면이더 bright 해 야하므로새로운 display 의개발이요구된다. Carbon nanotube tips

8 수직성장된 ZnO 를이용한 FED 제작

9 Flexible Field Emission Display (Adv. Mat. 2009) Co 5 Ge 7 NW on graphene

10 Lattice match for the epitaxial growth of Co 5 Ge 7 on graphite

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12 Field emission current density versus applied electrical field at a working distance of 500 μm. The emission current density is as high as 1.7 ma cm -2 at a field of 2.8 V μm -1, and the turn-on field of the sample is about 1.6 V μm -1. The emission of bare HOPG without NWs shows no FE data. Inset shows a schematic illustration of a field emission experimental setup.

13 Vertical Fe 1.3 Ge NW Arrays Integrated on Few-Layer Graphene for an Effective Field Emitter Good epitaxial lattice match (2.7%) Fe 1.3 Ge NWs (on Graphene) Single-crystalline NW

14 Fe 1.3 Ge NWs on Few-layer Graphene & FE property FE of Fe 1.3 Ge NWs (on Graphene) (~1580) (~2700) Decreased G band & blue-shifted 2D band; few graphene layers (3-5).

15 Ag NWs synthesized on a sapphire substrate Single crystalline Ag NW SEM image Equivalent to an FFT pattern of a TEM image High-resolution TEM image SAED image (Selected area electron diffraction)

16 MicroRaman 100 배대물렌즈 Excitation source : nm Ar ion laser Laser power : 0.5 mw

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19 Time-Resolved Innovative Nanowire Diffraction Laboratory Center

20 Visualizing SERS Hot Spots by Crossing NWs BCB dye, 514 nm laser

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22 BCB - Ag nanowire i) Parallel case Intensity (a.u) Wavelength (cm -1 )

23 SERS 의응용 : selective biosensor 1.Thiol is self-assembled on the surface of Ag. 3. 최근상업화된 SERS 기판칩 2. 자기조립된물질의끝에유용한작용기도입 : biotin, SpA(protein), U1A(antigen)

24 2)Single NW on-film as a SERS platform JACS (2009)

25 Reproducibile and Stable SERS signal of SNOF SNOF provides reliable reproducible and highly stable SERS signals.

26 7.Multiplex Pathogen DNA Detection By Au Particle-on-Wire SERS Sensor Nano Lett. (2010) First Multiplex SERS pathogen Diagnosing Sensor

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28 a) Two Au NWs functionalized with different probe DNAs (Efm and Sau001-20) are incubated in mixed solution of target DNAs (T1 and T2) and immersed into a solution of Au NPs modified with reporter DNAs (R1 and R2). Because R1 and R2 contains Cy5 and TAMRA as a Raman dye, respectively, the upper particle-on-wire structure gives SERS signal of Cy5 and the lower one gives SERS signal of TAMRA, respectively. b) (b) SERS spectra of Cy5 and TAMRA from Au particle-on-wire systems after DNA hybridization. The inset is an optical microscope image of particle-on-wire structures from which we obtain SERS. The scale bar denotes 5 μm.

29 (a)schematic representation for the patterned multiplex pathogen DNA detection using a particle-on-wire SERS sensor. (b)sers spectra from each of the four particle-on-wire system when the sample included two kinds of target DNAs (E. faecium and S. maltophilia). SERS spectra of Cy5 were detected only at the blue- and green-tagged sensors. The right figures are an SEM image (upper) and an optical microscope image (lower). The scale bar represents 5 μm. (c)sers intensities of 1580 cm -1 band measured on each particle-on-wire sensor with a sample containing only one kind of target DNA of a concentration of 10-8 M. (d)sers intensities of 1580 cm -1 band when the sample contains two, three, and four kinds of target DNAs, of which concentrations are 10-8 M each.

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31 Concentration dependent Au POW system The single Au POW structure can be a welldefined SERS sensor Multiplex biosensor of a µm size can be fabricated by individually modifying multiple Au NWs and combining them together on one substrate.

32 Reproducibility and sensitivity Detection Limit : 10 pm Dynamic range of 3 orders Quantitative detection of target DNA

33 8.It s Superconducting! Superconducting junction of a single-crystalline Au NW for an ideal Josephson device ACS Nano, Al + Au NW 1.Highest Transparency (0.95) 2.Coherent multiple Andreev reflection (MAR) 3.Fractional Shapiro steps 4.Andreev qubit or πjunction : quantum device

34 Al + Au NWs Nov filemane: IV-B0-T320mK-4 T = 260 mk V (µv) I (µa) KRISS Dr. M. Jung and Dr. J. Kim

35 9. Cell Nanoinjector PNAS 2007, 104, 8218

36 (A) 다중벽탄소나노튜브로만들어진 AFM tip 의 SEM 사진 (B) TEM image of the tip region of A. (C) TEM image of a MWNT-AFM tip coated with linker 1 and conjugated with QD streptavidin

37 금나노선을황산용액에넣어서전기분해실험을해보고있음. (+) 전압을 NW 에걸어준경우노란원속에보이는것처럼물방울이나노선으로올라옴. ( ) 전압을걸어주면나노선이짧아지는것을보면금이녹아나가는것을알수있다.

38 텅스텐프로브에 Ag paste 접착제로금나노선을붙인사진. 텅스텐프로브는끝이구부러져있음. 오른쪽은금나노선의확대사진.

39 Ultramicroelectrode (UME) - Diameter : < 25 μm 10. NW nanoelectrode - Radial diffusion enhanced mass transport Conventionally-sized electrode Planar diffusion - Advantages 1) working in highly resistive media (nonpolar solvent, polymer ) 2) working in high-speed CV 3) applicable to samples of small volume (single brain cell ) Ultramicroelectrode Radial diffusion Nano-scale electrode?

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42 스핀트로닉스 스핀트로닉스는 21 세기일렉트로닉스의뉴패러다임! Electronics Spintronics 실리콘반도체기술의한계한계극복이가능한가? 전하가움직일때열이발생 소자가특정크기이하로는작아질수없다 스핀의반전에는전혀열이발생하지않음 극미소자를만들수있다

43 스핀의특성 초고속 고집적성 비휘발성 빛의원편광과상호작용 전자는항상스핀보유 스핀은새로운 degree of freedom 이다! 스핀의반전에는피코초만소요 스핀자체가하나의트랜지스터역할 전원이꺼진후에도정보보존 스핀광소자제작 스핀소자와전자소자는언제나융합가능

44 스핀트로닉스 1.spin + transport + electronics 2.spin을 1만들어내고2전달하고3process하고검출해야한다. 금속기반 GiantMagnetoresis tance 및 Tunnel Magnetoresistance 하드디스크 MRAM 스핀양자전자소자 반도체기반 spin FET spin LED spin resonant tunneling diode

45 스핀트로닉스의화두는 자성반도체만들기 스핀의생성 : 강자성금속 스핀의전달 : 반도체나노선 이때둘사이의전도도차이 (conductivity mismatch) 때문에전달된스핀의생존확률이 5% 미만으로낮아짐.

46 어떻게단결정강자성 반도체 NW 를만드나? 기존연구의한계 DMS (Diluted Magnetic Semiconductor)NW 단결정반도체에자성을가지는금속원소를불순물로주입 단결정강자성나노선 금속실리콘 NW 열역학적으로안정한강자성반도체 NW 합성 일정한조성의도핑어려움. 홀도핑때문에스핀수명짧음. 도핑없음. 실리콘기판위성장가능

47 Ferromagnetic Vertical Ni 3 Co NWs (Chem. Mat. 2010) Perfect Single-crystal Ferromagnetic NW Spin-torque Transfer Memory Development

48 Vertical Fe 1.3 Ge NW Arrays Integrated on Few-Layer Graphene for an Effective Field Emitter Good epitaxial lattice match (2.7%) Fe 1.3 Ge NWs (on Graphene) Single-crystalline NW

49 5.NWs for Spintronics! Spin Injection (Half-metal with 100 % spin polarization) Spin LED Spin FET FM Semiconductor FM (ferromagnetic) Memory devices (Room temperature ferromagnet) GMR sensor Racetrack Memory MRAM

50 Synthesis of Heusler Alloy Fe 3 Si NWs Nano Lett. (2010) FeSi NW reacts with O 2 and becomes Fe 3 Si NW. 1.Difficult NWs can be synthesized. 2.Fe 3 Si is ferromagnetic half-metallic NW!

51 6.NWs for Phase Change Memory In-situ TEM Observation of Heterogeneous Phase Transition of a Constrained Single-crystalline Ag 2 Te NWs Monoclinic to FCC transition study of Ag 2 Te NWs by in-situ TEM at Nano Lett. (2010)

52 Overlap of monoclinic and fcc (Moire fringe) White square Completely converted to fcc

53 plate-like BCC penetrating into FCC matrix at 200