The evolution of the MgO(001) film morphology on Ag(001) was studied in dependence on the growth temperature (373À673 K) and grown MgO quantity (0.2À2 ML) by lowenergy electron diffraction and scanning tunneling microscopy. We evidence an island growth mode of MgO for all temperatures. At 373 K, the MgO film exhibits a high island density, which is due to a too small surface mobility of the film compounds during the film growth. At a growth temperature of 673 K, silver hampers a perfect growth of MgO islands due to its high mobility, which leads to dendrites of MgO. The flattest and largest MgO islands are obtained at a growth temperature of around 573 K, which is a compromise guaranteeing a sufficiently high Mg or MgO mobility but also an enough low diffusion of silver.

We present an electronic circuit that allows to calibrate and troubleshoot scanning probe microscopy (SPM) controllers with respect to their noise performance. The control signal in an SPM is typically highly nonlinear—the tunneling current in scanning tunneling microscopy (STM) varies exponentially with distance. The exponential current-versus-voltage characteristics of diodes allow to model the current dependence in STM. Additional inputs allow to simulate the effects of external perturbations and the reactions of the control electronics. We characterized the noise performance of the feedback controller using the apparent topography roughness of recorded images. For a comparison of different STM controllers, an optimal gain parameter was determined by exploring settling times through a rectangular perturbation signal. We used the circuit to directly compare the performance of two types of SPM controllers used in our laboratory.