Past exam of the MPhil in micro- and nanotechnology enterprise course of the University of Cambridge / 2019 / Paper 1 / Section A(i) / 1 / ii / Solution

piezoelectric scanner creep is the continued slow displacement after a step in scanner drive, even when the commanded voltage has stopped changing. The scanner's strain continues to relax, and the motion can resemble a slowly decaying, approximately logarithmic drift. After changing scan size, position or offset, early lines can therefore have stretched or compressed coordinates. Allow settling, avoid large abrupt moves, use a position-sensor closed-loop control system, and compare repeated images. This time-dependent response differs from the direction-dependent piezoelectric hysteresis and from ordinary thermal drift.