Fabrication of oxide nanostructure using Sidewall Growth 田中研 M1 尾野篤志

VO 2 LPCMO Background strongly correlated electron system( 強相関電子系 ) in nanosize 100nm M. Fäth et al, Science 285 (1999)1540 Ferromagnetic Anti-Ferromagnetic M. M. Qazilbash et al, Science 318 (2007) 1750, Metal Insulator (La, Pr,Ca)MnO 3 film STM image VO 2 film SNIM image 500nm

Nanostructure lead to sharp phase transition Background strongly correlated electron system( 強相関電子系 ) in nanosize Nano-structure fabrication technique Size-control InsulatorMetal Y. Yanagisawa et al Appl. PHYSICS LETTERS 89 (2006) nm Future advanced nano-device Dimension-control (La, Pr,Ca)MnO 3 film Charge Ordering Insulator Ferromagnetic metal 1μm

Fabrication of nanostructure Top down and Bottom up Top down Technique Figure materials finely For example ―Nano Imprint Lithography ―AFM Lithography Bottom up Technique Accumulate atoms by deposition For example ―Pulsed Laser Deposition ―Sputtering Deposition Top downBottom up Complex pattern○ △ Size control △ (>10 1 nm) ○(>10 -1 nm)

Our nanostructure fabrication method Combination of Top down and Bottom up Top Down Nano Imprint Technology Bottom up Pulsed Laser Deposisiton Top downBottom upCombination Size control △ (>10 1 nm) ○(>10 -1 nm) Complex pattern ○ △ ○

Purpose - Fabrication of oxide nanostructures and evaluation of their properties- Establishment of fabrication method ZnO nanobox Measurement of their physical properties Application for devices ZnO: Semiconductor, Optical Device ⇒

Fabrication of the nanostructure ①Patterning 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 Room temperature

Result1-1: Deposition of ZnO time-dependency of sidewall thickness Deposition time [min.] Film’s thickness ∝ Sidewall’s thickness I measured thin films’ thickness Sidewall thickness : controllable Thickness [nm] ZnO deposition: PLD method Substrate: Si(001) P O2 =1.0×10 -2 Pa Deposition time: min. Evaluation method: Atomic Force Microscopy d: film’s thickness (nm) t: deposition time (min) d=1.30t

Result1-2: Crystallization condition Optimize the condition of Crystallizing ZnO by Annealing ZnO crystallization: higher than 550 ℃ Annealing temperature: ℃ Evaluation method: X-ray Diffraction 2θ [°] Intensity (a.u.)

1μm 500nm 45nm Polymers on substrate Ion Milling Result2: Fabrication of ZnO nano-box Evaluation method: Scanning Electron Microscopy ZnO-deposited substrate Acetone cleaning

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.

2 µm 100 nm 200 nm 60nm 150 nm Examples of the various patterns: Mo, Au Example of various patterns N.-G. Cha et al. Nanotechnology 20 (2009)

Next Step ―I am trying to fabricate Fe 3-x Zn x O 4 nanowire 500nm 50nm!! MR effect ⇒ MRAM, Spin FET, … Spintronics Y. Yanagisawa et al Appl. PHYSICS LETTERS 89 (2006) FZO 1.Strongly correlated electron system 2.Ferromagnetic room temperature Magnetic Field