  We characterized resistance drift in phase change memory devices in the 80 K
to 300 K temperature range by performing measurements on 20 nm thick, ~70-100
nm wide lateral Ge2Sb2Te5 (GST) line cells. The cells were amorphized using
1.5-2.5 V pulses with ~50-100 ns duration leading to ~0.4-1.1 mA peak reset
currents resulting in amorphized lengths between ~50 and 700 nm. Resistance
drift coefficients in the amorphized cells are calculated using constant
voltage measurements starting as fast as within a second after amorphization
and for 1 hour duration. Drift coefficients are in the range between ~0.02 and
0.1 with significant device-to-device variability and variations during the
measurement period. At lower temperatures (higher resistance states) some
devices show a complex dynamic behavior, with the resistance repeatedly
increasing and decreasing significantly over periods in the order of seconds.
