NanowiresConnie Chang-Hasnain EECS Dept.UC BerkeleyEE C 235/NSE 203Lecture 192Outline Introduction Vapor Liquid Solid mechanism III-V NW growth methods Metal-organic chemical vapor deposition (MOCVD) Laser Ablation CVD Molecular Beam Epitaxy Chemical Beam Epitaxy Uses gas sources to in an MBE chamber Phosphin (PH3) and Arsin (AsH3) as precursors Triethyl-Gallium, Ga(C2H5)3 Trimethyl-Indium, In(CH3)3 and Triethyl-Antimony, Sb(C2H5)3. Basic material characterization techniques SEM TEM Photoluminescence Devices34Materials Synthesis TemplatesMaterials Synthesis TemplatesReinforcement for composite materialsReinforcement for composite materialsModel systems for novel physicsModel systems for novel physicsNanoprobesNanoprobesDevicesDevicesNanowiresNanowiresfillingcoatingconvertingNEMSSensorsFETDiode lasers FunctionalizedAnd high aspect ratio SPM probesNanowire ApplicationsField Emission DisplaySolar Cells5First VLS DemonstrationVapor Liquid Solid (VLS) growth mechanism suggested in 1964:Bell Telephone Laboratories, Inc. (New Jersey, USA)R. S. Wagner and W. C. Ellis, Appl. Phys. Lett. 4, 189 (1964)Bell Telephone Laboratories, Inc. (New Jersey, USA)678GaAs NW on GaAs Substrate First VLS grown III-V (InAs) nanowires reported in 1991 (MOCVD) NW crystal Growth aligned in [111] direction Aligned on (111)B substrate Ægrowth is dominant on As terminated surface. Zinc-blende if Tg 460-500C Wurtzite if Tg <420 or >500C Twin type along growth axis Quantum-size effect PL blue shifts for 35-100 nm width PL 4X stronger along wire direction Demosntrated p-n junction along the wire RT CW electroluminescence Deposited Au Annealing temperature determines size Growth temperature Determines shape, width and growth rate Width and length Depends on growth time Independent of III or V flow rates Growth mechanism Deduced that growth is limited by Au and determined by surface reaction between Au-substrate and sources. Rotational twin and wurtzite structures unknown K. Hiruma, et al., J. Appl. Phys. 74, 3162 (1993)Central Research Laboratory, Hitachi Ltd. (Tokyo, Japan)K. Haraguchi, et al., Appl. Phys. Lett. 60, 745 (1992)Central Research Laboratory, Hitachi Ltd. (Tokyo, Japan)9GaAs NW PL- Quantum Size Effect Blue shift ~5 meV (2.7 nm) from a to c Very small for quantization effect FWHM ~7 meV (3.75 nm) Very narrow – too good to be true?10GaAs Diode NW on GaAs SubstrateK. Haraguchi, et al., Appl. Phys. Lett. 60, 745 (1992); M. Koguchi, et al., Jpn. J. Appl. Phys. 31, 2061 (1992); K. Hiruma, et al., J. Appl. Phys. 74, 3162 (1993); Central Research Laboratory, Hitachi Ltd. (Tokyo, Japan) Claimed the emission is not from GaAs substrate EL Peak is 1.485 eV GaAs peak = 1.483 eV Red shift by 2 meV; with linewidth of 55 meV~55 meV11GaAs and InAs NW on GaAs Substrate Consisting of Both ZB and WZ StructuresM. Koguchi, et al., Jpn. J. Appl. Phys. 31, 2061 (1992), Central Research Laboratory, Hitachi Ltd. (Tokyo, Japan)12GaAs NW on GaAs Using MOCVD: Lateral GrowthT. Shimada, et al., Superlattices and Microstruct. 24, 453 (1998); K. Haraguchi, et al., J. Vac. Sci. Technol. B15, 1688 (1997), Central Research Laboratory, Hitachi Ltd. (Tokyo, Japan) Started to hypothesize that Au droplet determine NW diameter andgrowth time on its length. Use step height to control NW diameter. Use pattered evaporation to control Au size and position.1314GaAs NW using Laser-Assisted Catalytic Growth (LCG)X. Duan, et al., Appl. Phys. Lett. 76, 1116, (2000), Harvard Univ. (Massachusetts, USA) Difference from MOCVD NWs MOCVD NWs are produced on surfaces and not in bulk quantities (??) MOCVD NWs are tapered Diameters: MOCVD @ 10-15 nm and LCG @ 3-5 nm.15GaAs NW using LCGX. Duan, et al., Appl. Phys. Lett. 76, 1116, (2000)Harvard Univ. (Massachusetts, USA) PL of individual NW at RT PL peaks at 752, 794 and 836 nm, corresponding to 1.65, 1.56 and 1.48 eV Blue shift are ~90 and ~170 meV PL linewidths are very wide, corresponding to 195~254 meV Authors claimed this may be due to exciton diffusion along the wire More evidence was under investigation Æ NEED to follow up on this.130 nm~254 meV100 nm~195 meV100 nm~195 meV16X. Duan, et al., Nature 409, 66 (2001)Harvard Univ. (Massachusetts, USA)InP NW using LCG EL emission @ 820 nm for InP(925 nm) Æ puzzling! quantum efficiency ~0.001%1718Various NWs Using LCGX. Duan, et al., Adv. Mater. 12, 298 (2000), Harvard Univ. (Massachusetts, USA)19InP on Patterned Si Using MOCVDY. Watanabe, et al., Physica E24, 133 (2004); NTT Co. (Kawagawa, Japan) Growth on (100) Si and patterned (100) Si substrate Alignment in 111 direction Blue-shifted PL show quantum confinement Authors claimed ~100 meV shift from bulk value Æ NW 10~20 nm wide Deposited in 10-20 nm size patterned Si substrate to form Au nanoparticles”100 meV20InP NW on InP with MOCVDS. Bhunia, et al., Physica E21, 583 (2004), NTT Co. (Kawagawa, Japan) Wafer scale 10-20 nm Au colloidal nano particles Annealing and growth temperature dependence21InP NW on InP Using MOCVDS. Bhunia, et al., Physica E21, 583 (2004), NTT Co. (Kawagawa, Japan) 22InP NW on InP Using MOCVDS. Bhunia, et al., Physica E21, 583 (2004), NTT Co. (Kawagawa, Japan) Blue shift is 25 and 32 meV (a) the reference (b) NW grown on 10 nm Au (c) NW grown on 20 nm Au particles. The histograms of the insets show the distribution in diameter of the respective nanowires.1.375 eV1.382 eV87 meV77 meVInP Eg(RT) = 1.346 eV (920 nm) ; Eg (6K) = 1.415 eV (875 nm)23GaAs/AlGaAs QD in NW24GaAs/AlGaAs QD in NW25GaAs/AlGaAs QD in NW26GaAs/AlGaAs QD in NW27GaAs/AlGaAs QD in NW28T. Mårtensson, et al., Nano Lett. 4, 699 (2004); Lund Univ. (Lund, Sweden)InP NW on InP using MOCVD + Nanoimprint & E-Beam Relatively large NWs: 210-310 nm diameter NW size determined by Au particles Used EBL and NIL to define Au Mean deviation: EBL 8.3% and NIL 10.8%29InAs QD in GaAs NW on GaAsN. Panev, et al., Appl. Phys. Lett. 83, 2238 (2003), Lund Univ. (Lund, Sweden) CBE is used 40 nm Au nanoparticle Single QD PL shows narrow linewidth (200 µeV) at 4K similar to SK QDs4KComparison with SK InAs QDs30GaAsP Heterostructure NW on SiT. Mårtensson, et al., Nano Lett. 4, 1987 (2004); Lund Univ. (Lund, Sweden) MOCVD is used 40 nm Au nanoparticle GaAs, InP, GaP and GaAsP NWs are
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