PhD Thesis Arne Lüker final version V4 - Cranfield University

Tunability [%]
100
90
80
70
60
50
40
30
20
10
0
Sol-Gel derived Ferroelectric Thin Films for Voltage Tunable Applications
Unfortunately the Cr/Au top electrodes of the four samples blistered away at different
fields, making a direct comparison of the shown data in Fig. 6.5 rather complicated. The
blistering could be a result of different adhesion strengths due to contaminations of the
surface of the ferroelectric thin films prior to the deposition of the electrodes or an
insufficient vacuum during the evaporation. To get a clearer picture the formula
developed in section 2.1.2 was fitted to the measured data. The result is plotted in Fig. 6.6
-20 -15 -10 -5 0 5 10 15 20
Bias Voltage [V]
The result shows that the tunability of Pb0.4Sr0.6Mn0.01Ti0.99O3 is slightly higher than
that of Pb0.4Sr0.6Mn0.03Ti0.97O3. Actually no surprise as we discovered in the last section
that the hopping of the charge carriers between the Mn sites begins to occur in 2 mol%
pure calc.
1% Mn calc.
3% Mn calc.
5% Mn calc.
pure meas.
Fig. 6.6: Comparison of the measured and calculated tunability of (Pb0.4,Sr0.6)(Ti1-x,Mnx)O3.
1% Mn meas.
3% Mn meas.
5% Mn meas.
The fitting parameters Cmax[nF]/V2[V] are: pure 9.5/5.1; 1% 15/3.5;3% 13.8/4.5; 5% 5.7/8.5
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