Current-voltage and activation energy measurements can be used to probe grain boundary potential barriers. A common type of activation energy for Current conduction in a polycrystalline material is that due to the grain boundary potential barrier. Activation energy can be related directly to grain boundary barrier height. The height of this barrier depends on occupation of grain boundary states. Its decrease with applied voltage accounts for the superohmic current-voltage behavior of polycrystalline silicon and of ZnO varistors. It also accounts for positive temperature coefficient device behavior. A similar voltage dependence is reported here for barrier layer and COG type capacitors, where activation energies decrease from 0.99 to 0.44 eV and from 1.61 to 0.90 eV, respectively. Such decreases are not seen for X7R devices, even though currents are superohmic. Several mechanisms account for this. It is concluded that the grain boundary potential barrier may offer a major source of impedance to leakage current in multilayer ceramic capacitors, and its decrease may result in device failure.
[1]
C. Grovenor.
Grain boundaries in semiconductors
,
1985
.
[2]
L. Burton,et al.
Leakage Currents in Multilayer Ceramic Capacitors
,
1984
.
[3]
S. Tominaga,et al.
Electrical Conduction of ZnO Varistors under Continuous DC Stress
,
1980
.
[4]
D. Payne,et al.
Characterization of internal boundary layer capacitors
,
1980
.
[5]
C. H. Seager,et al.
Grain boundary states and varistor behavior in silicon bicrystals
,
1979
.
[6]
C. H. Seager,et al.
The dc voltage dependence of semiconductor grain‐boundary resistance
,
1979
.
[7]
H. R. Philipp,et al.
Theory of conduction in ZnO varistors
,
1979
.
[8]
J. D. Levine.
Theory of varistor electronic properties
,
1975
.
[9]
W. Heywang,et al.
Resistivity Anomaly in Doped Barium Titanate
,
1964
.
[10]
Lawrence L. Kazmerski,et al.
Polycrystalline and amorphous thin films and devices
,
1980
.
[11]
P. Nagels.
Experimental Hall Effect Data for a Small-Polaron Semiconductor
,
1980
.