Diagram of the pyroelectric measurement circuit. L, modulated laser beam; S, sample; B, voltage bias source; A, lock-in current amplifier; and C, relay switch.
A sequence of voltage pulses, used in poling-switching experiments, and an example of the pyroelectric current, recorded from a 35-layer film. The parameters , , , and are durations and amplitudes of poling and switching pulses, respectively. The currents and are measured after relaxation, as shown. The net switched current is .
The time evolution of the pyroelectric response in the 35-layer sample, recorded at room temperature after applying a switching pulse of amplitude and duration indicated on the right. Zero time corresponds to the end of the switching pulse. The sample was poled with a pulse of amplitude and duration and then short circuited for approximately before application of the switching pulses. The initial pyroelectric response for all the traces is within the hatched zone.
The net change in pyroelectric signal due to switching with pulses of varying amplitude and duration recorded at room temperature with the 35-layer sample (solid symbols) and 30-layer sample (open circles). The poling pulse was the same for all measurements.
The relaxation of pyroelectric response after the end of the switching pulse in the 30-layer sample as a function of sample temperature. The poling pulse and switching pulse were the same for each measurement.
The decadal pyroelectric relaxation rate in the 30-layer film obtained from curves like those in Fig. 5. The poling pulse was the same for all measurements. (a) The dependence of the rate on sample temperature for a switching pulse amplitude . (b) The dependence of the rate on the switching pulse duration at different sample temperatures for a switching pulse amplitude . (c) The dependence of the rate on the switching pulse amplitude for a sample temperature of and a switching pulse duration .
Switching of a 30-layer film at room temperature by a series of switching pulses. A poling pulse applied before each series. (a) Pyroelectric current measured during a series of pulses with amplitude and duration . (b) Pyroelectric current measured immediately before each ensuing pulse in a series like the one shown in (a), but for a several different switching pulse amplitudes .
Pyroelectric hysteresis measured at room temperature with a 35-layer sample, obtained using a sequence of switching pulses with amplitudes cycling with a triangular envelope. (a) The hysteresis loops for three different pulse durations. (b) The dependence of the loop half-width (, left axis) and the remanent height (, right axis) on the pulse duration. (c) The full hysteresis loop for pulses showing the initial segment starting a zero amplitude and zero sample polarization. The dashed lines show the values of the pyroelectric current measured after applying pulses of amplitude and duration, for comparison.
The critical-switching-time distribution obtained by differentiating and smoothing the experimental relaxation curves (Fig. 4). Inset: the pulse duration necessary to switch half of the polarization as a function of reciprocal electric field .
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