Abstract
The advances in the fields of scanning probe microscopy, scanning tunneling spectroscopy, point contact spectroscopy, and point contact Andreev reflection spectroscopy to study the properties of conventional and quantum materials under cryogenic conditions have prompted the development of nanopositioners and nanoscanners with enhanced spatial resolution. Piezoelectric-actuator stacks as nanopositioners with working strokes of 10μm and positioning resolution ∼(1-10) nm are desirable for both basic research and industrial applications. However, information on the performance of most commercial piezoelectric actuators in cryogenic environment and in the presence of magnetic fields in excess of 5T is generally not available. In particular, the magnitude, the rate, and the associated hysteresis of the piezo-displacement at cryogenic temperatures are the most relevant parameters that determine whether a particular piezoelectric actuator can be used as a nanopositioner. Here, the design and realization of an experimental setup based on interferometric techniques to characterize a commercial piezoelectric actuator over a temperature range of 2K ≤ T ≤ 260K and magnetic fields up to 6T are presented. The studied piezoelectric actuator has a maximum displacement of 30μm at room temperature for a maximum driving voltage of 75V, which reduces to 1.2μm with an absolute hysteresis of 9.1±3.3nm at T = 2K. The magnetic field is shown to have no substantial effect on the piezo-properties of the studied piezoelectric-actuator stack.
Highlights
The development of precise nanopositioning systems with spatial resolution ∼(1–10) nm and time constant ∼(10–100) μs is relevant for both basic and applied research, as well as for industrial applications.1 The positioning resolution of conventional actuator systems including hydraulic and ac/dc motors is too coarse for most modern technologies, even though these actuators are able to provide large output force and working strokes
The displacement rate dRpiezo of a piezoelectric actuators (PEAs) stack is defined as the change in dimension per unit applied voltage, and the knowledge of dRpiezo for a given piezo-actuator at any arbitrary T is essential for an efficient control of the PEA stack or the mechanical stage to which it is attached
The PEA stack is mounted on a scitation.org/journal/rsi piezo-stage and placed inside a cryostat equipped with a superconducting magnet
Summary
The development of precise nanopositioning systems with spatial resolution ∼(1–10) nm and time constant ∼(10–100) μs is relevant for both basic and applied research, as well as for industrial applications. The positioning resolution of conventional actuator systems including hydraulic and ac/dc motors is too coarse for most modern technologies, even though these actuators are able to provide large output force and working strokes. By introducing a dynamic mode to the static PCAR setup, a lateral degree of freedom in the sample plane is added and makes it possible to map the sample surface. This improvement is expected to open new perspectives for the characterization of quantum materials. One major challenge in employing PEA stacks as scanners is represented by their limited displacements at cryogenic temperatures.. The piezo-hysteresis as a function of T determines whether a particular PEA stack can be employed as a position scanner with nm resolution, in techniques for mapping surfaces such as STM and SPCAR.
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