Characterization of High Temperature Superconducting Thin Film Grown by Laser Ablation Method
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CHARACTERIZATION OF HIGH TEMPERATURE SUPERCONDUCTING THIN FILM GROWN BY LASER ABLATION METHOD K.Shimizu*,H.Nobumasa*,N.Nagai"*,T.Matsunobe'" AND T.Kawai*" "Toray Ind.Inc.,2-l.Sonoyama 3-chomeOtsuShiga 520 Japan "Toray Research Center Inc.,1-iSonoyama 3-chome, Otsu, Shiga 520 Japan "**Osaka University,IbarakiOsaka 567,Japan ABSTRACT function of complex dielectric We have measured the the near infrared region directly by samples in Bi 2 Sr 2 CaCu 2 0, As for both single crystal and thin film, spectroellipsometry. superconducting samples have a zero point in the real part (e,) of and a clear peak of the the complex dielectric function WC) almost the same frequency. imaginary part of the inverse E" at On the other hand, non-superconducting samples have no such E, zero Then we point, and the peak height of (-Im(l/E')) becomes small. this samples by of the superconductivity can determine spectroellipsometry measurement at room temperature. INTRODUCTION is an effective method to study the Optical measurement electronic structure of materials when the complex dielectric there is In high Tc superconductors constant is obtained[l]. a common feature such as the reflectivity edge in the near infrared for understanding the region which is thought to be essential However the customary way of superconducting mechanism [2-5]. by using the constants the complex dielectric obtaining from some uncertainties transformation suffers Kramers-Kronig because of the extrapolation. Spectroellipsometry directly provides the complex dielectric is very reliable for studying the details of functions which frequency dependence features[6]. We have investigated the relation of the material and the complex superconductivity between dielectric function, as measured at room temperature. EXPERIMENTAL Ellipsometry The complex dielectric function was measured directly by The details are from 5000cm-' to 25000cm-1. spectroellipsometry shown in Tablel. Samples Bi 2 Sr 2 CaCu 2O0 thin films were prepared by laser ablation was used as a method. A single crystal of Bi 2 Sr 2 Ca1Cu 2O0 The details are shown in Table2. standard. RESULTS AND DISCUSSION Results
of
an
ellipsometry
measurement
for
Mat. Res. Soc. Symp. Proc. Vol. 236. @1992 Materials Research Society
a
single
450
Table 1
Apparatus
Ellipsometry
Spectroellipsometer NPDM-1000 (Nikon)
Spectrometer
M-70
Source
Halogen lamp
Detector
Si-Ge
Polarizer, Analyzer
Gran-Thomson
Incident Angle
80*
Frequency Range
5000-25000cm-'
Table 2
Thin
Film
Bi 2 Sr2CaCu 2 O
Method
Excimer Laser (ArF) Ablation
Substrate Samples A
samples
Polished MgOSingle crystal Dimension
3000A(thickness)x5mmx5mm
Deposition Rate
10001/hr
Substrate temp.
660t
Dimension
5000i (thickness)x5mmx5mm
Deposition Rate
50001/hr
Substrate temp.
680t
(c-axis oriented)
Samples B
(c-axis oriented)
Single Crystal
Method
TSFZ
Dimension
lmmx5mmx7mm
Superconductivity
90K (Tc zero)
(made by Kitahama and Iloriuchi of Osaka Univ.)
451
R (Y.)
Single crystal
A (deg) 50.0
50.0 40.0 30.0 20.0 10.0
0.0
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