MgB2 film Fabrication

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MgB2 film Fabrication

• Chu-Nan Chang
• Department of Physics, National Taiwan Normal
  University
• Coworkers
• C.H. Hsieh, H.C. Hsu, M.I. Chang, and G.Z. Huang
  (NTNU)
• H.C. Yang (NTU)
• J. M. Chen (NSRRC)

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1. Introduction
2. Apparatus
3. Characteristics of films

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Introduction

• Discovery 2001 by Nagamutsu et al.
• Chemical Form MgB2
• Crystal Structure AlB2
• Superconducting Transition Temperature 39K
• Hc2(T0) 12.5T
• Coherence Length (?0) 5.2 nm
• Penetration Depth (?) 140 nm
• Multi-gaps 6.8 meV and 1.8 meV

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Lattice structure

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Bonding states at the Fermi level derived from p
orbital of boron

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Apparatus

1. D. C. Magnetic Ion Sputtering System
2. Ultra-high Vacuum Electron Beam Evaporator System
   

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XANES of a precursor film
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XANES of the MgB2 films
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• Microstructures of the film by magnetic ion
  sputtering
• precursor
  annealed

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????/??(C/min) ???? ???? (K) ??(nm) ??
S6 N/A N/A N/A 400 ???
S7 750/40 ????????? 20 350
S8 750/30 ????????? 24 300
S9 800/30 ???? 25 350
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S8??1X1 µm,roughness 8 nm
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S9??2X2 µm,roughness 45 nm
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A Microwave Filter Fabricated by Using MgB2 Films

• A four-U hairpin microwave filter with the
  central frequency of 6.1 GHz has been fabricated
  by using MgB2 films.
• The method of UV lithography and Ar ion milling
  was used to form the desired pattern of the
  filter.
• The band width is 1.6 GHz.

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• The measured insertion loss is about 0.10 dB
• The simulation value of 0.03 dB.

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S21
S11
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MgB2
YBCO
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Characteristics of a Band-pass Microwave Filter
Fabricated by Using MgB2 films M. Y. Chang1, C.
N. Chang1, C. H. Hsiech1, H. K. Zeng2, J. Y.
Juang2, and Y. S. Gou 2 Abstract A four-U
hairpin microwave filter with the central
frequency of 6.1 GHz has been fabricated by using
MgB2 films. The method of UV lithography and Ar
ion milling was used to form the desired pattern
of the filter. The band width is 1.6 GHz. The
superconducting transition temperature (Tc) of
the MgB2 film is about 25 K. The network analysis
indicated that this filter had insertion loss of
about 0.1 dB at 5 K and revealed the sharp skirt
property. The values of the central frequency,
the bandwidth, and the skirt property are very
close to those obtained from the computer
simulation of a computer code ADS 2003A. The
insertion loss deviates a little from the
simulation value of 0.03 dB, probably due to the
impurities in the film. The decrease of the
insertion loss versus the reduced temperature
T/Tc was observed to be slower than that of a
hairpin filter with six U shape resonators made
by a high temperature superconducting film
of YBCO.
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