Figure 3
Pulsed bipolar reset characteristics.
(a) R measured after the application of a negative voltage pulse of amplitude VA on a PCM device initially prepared in the set state. Pulses with variable pulse-width tP were applied, from 100 ns to 100 μs. For tP below 10 μs, resistance increases above the melting point due to amorphization. For tP = 10 μs and 100 μs, an additional increase of resistance is observed just below melting, at −1.3 V and −1.2 V, respectively. This additional feature can be attributed to ionic migration and the formation of a depleted barrier with high resistance close to the BE interface. (b–d) Waveforms of the PCM current during pulses indicated as points 1, 2 and 3, respectively, in (a). The current remains low for VA = −1 V (b), shows a sudden drop indicative of bipolar switching for VA = −1.34 V (c) and remains equal to a high value for VA = −1.7 V.
