CONTROL OF LEAKAGE RESISTANCE IN PB(ZR,TI)O-3 THIN-FILMS BY DONOR DOPING

Donor doping, with La and Nb, has been used successfully to improve the leakage resistance of Pb(Zr,Ti)O-3 (PZT) films. Donor doping of Pb(Zr0.5Ti0.5)O-3 films has led to an improvement in the leakage resistance of over 2 1/2 orders of magnitude at elevated temperatures (T greater than or equal to 100 degrees C). The effect on leakage resistance is the same for the A-site (La) and B-site (Nb) dopants. However, the improvement is only about 1 order of magnitude near room temperature. This temperature effect is due to an increase in the transition temperature from a low activation energy mechanism to a higher activation energy mechanism. Similar improvements in leakage resistance have also been obtained by increasing the Pb concentration in the starting solution, which implies that Pb vacancies are the dominant acceptor species in the undoped films. In addition, donor doping has been effective in improving the electrical breakdown strength at elevated temperatures. Consequently, donor-doped PZT films have been shown to be superior to undoped films for applications requiring high leakage resistance, such as decoupling capacitors.