Fabrication of oxide nanostructure using Sidewall Growth 田中研 M1 尾野篤志 Background strongly correlated electron system(強相関電子系) in nanosize (La, Pr,Ca)MnO3 film STM image LPCMO Ferromagnetic VO2 film SNIM image VO2 Metal Insulator Anti-Ferromagnetic 100nm 100nm M. Fäth et al, Science 285 (1999)1540 100nm 100nm 500nm M. M. Qazilbash et al, Science 318 (2007) 1750, Background strongly correlated electron system(強相関電子系) in nanosize • Nanostructure lead to sharp phase transition Insulator (La, Pr,Ca)MnO3 film Metal 500nm 1μm 500nm Charge Ordering Insulator Ferromagnetic metal Y. Yanagisawa et al Appl. PHYSICS LETTERS 89 (2006) 253121 Nano-structure fabrication technique Dimension-control Future advanced nano-device Size-control Fabrication of nanostructure Top down and Bottom up Bottom up Technique • Accumulate atoms by deposition For example ―Pulsed Laser Deposition ―Sputtering Deposition Top down Technique • Figure materials finely For example ―Nano Imprint Lithography ―AFM Lithography Top down Bottom up Complex pattern ○ △ Size control △(>101nm) ○(>10-1nm) Our nanostructure fabrication method Combination of Top down and Bottom up Size control Complex pattern Top down △(>101nm) ○ Top Down • Nano Imprint Technology Bottom up ○(>10-1nm) △ Combination ○(>10-1nm) ○ Bottom up • Pulsed Laser Deposisiton Purpose - Fabrication of oxide nanostructures and evaluation of their properties• Establishment of fabrication method ZnO nanobox ZnO: Semiconductor, Optical Device Amorphous @RT ⇒ Crystal @HT • Measurement of their physical properties • Application for devices Fabrication of the nanostructure ① Patterning by NIL ② Depositon using Sidewall growth ③ Removing patterns ( Ion milling and Cleaning) ④ Crystallization by annealing ⑤ Measurement of their physical properties Experimental method 1. Deposition on Plane Substrate 1-1. Control thin film’s thickness 1-2. Optimize crystallization condition by annealing 2. Deposition on Nano-pattaerne substrate ― Fabricate ZnO nanobox using sidewall growth Deposition@ Room temperature Result1-1: Deposition of ZnO time-dependency of sidewall thickness I measured thin films’ thickness Thickness 160 [nm] 180 140 120 d=1.30t 100 80 d: film’s thickness (nm) t: deposition time (min) 60 40 20 ZnO deposition: PLD method Substrate: Si(001) PO2=1.0×10-2Pa Deposition time: 30-120min. Evaluation method: Atomic Force Microscopy Deposition time [min.] 0 0 50 100 150 Film’s thickness∝Sidewall’s thickness Sidewall thickness : controllable Result1-2: Crystallization condition Optimize the condition of Crystallizing ZnO Intensity (a.u.) 950℃ 550℃ as-grown ZnO(0002) Annealing temperature: 550-950 ℃ Evaluation method: X-ray Diffraction 34 34.5 35 35.5 36 36.5 37 2θ [°] by Annealing •ZnO crystallization: higher than 550℃ Result2: Fabrication of ZnO nano-box Evaluation method: Scanning Electron Microscopy Polymers on substrate ZnO-deposited substrate 1μm Ion Milling 1μm Acetone cleaning 1μm 45nm 500nm Summary • I succeeded in fabrication of ZnO nanobox by the combination Top down (imprint) and Bottom up (PLD) technique. • The side wall thickness was 45nm. • I need to improve the accuracy and responsibility. This technique can be applied for another system. Various patterns can be formed. Example of various patterns Examples of the various patterns: Mo, Au 100 nm 150 nm 200 nm 2 µm 60nm 200 nm 150 nm N.-G. Cha et al. Nanotechnology 20 (2009) 395301 Next Step ―I am trying to fabricate Fe3-xZnxO4 nanowire 500nm 50nm!! Y. Yanagisawa et al Appl. PHYSICS FZO LETTERS 89 (2006) 253121 1.Strongly correlated electron system 2.Ferromagnetic semiconductor @ room temperature MR effect ⇒ Spintronics MRAM, Spin FET, …
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