AR-PPLN Test Sample
For Piezoresponse Force Microscopy
The AR-PPLN Test Sample is a convenient and reliable sample for practice, setup, and verification for a wide variety of Piezoresponse Force Microscopy (PFM) techniques. This includes, but is not limited to, imaging and point hysteresis loops. The reference sample has stripe domains permanently polarized for easy identification and optimization of PFM parameters.
The AR-PPLN Test Sample is produced on a lithium niobate wafer. The process starts with poling the wafer with a very strong electric field to create a homogeneously poled substrate with a polarization axis orthogonal to the wafer surface. A single lithographic photomask is used to print a mask of parallel stripes on one side of the wafer. It is then polarized in the opposite direction, which affects only the unmasked striped areas and propagates through the entire thickness of the wafer. Because of the close spacing of the unmasked regions, the polarization can “wander” laterally through the wafer thereby making the 10µm pitch periodic polarization best on one side of the wafer and somewhat random on the other side.
For PFM investigation of the AR-PPLN Test Sample, the sample should be electrically connected to a sample holder in an AFM setup (Figure 1). The Test Sample should be stable for PFM applications at applied potentials less than 50V because of its high coercive field. The Phase and Amplitude data channels show the piezoelectric effect (Figure 2). For typical PFM hysteresis loops, the switching voltage frequently exceeds 100V (Figure 3). To attain these large voltages, the use of an integrated high voltage amplifier, such as Asylum’s HVA220 Amplifier, is necessary.
Specifications subject to change.
Figure 1: The AR-PPLN (unmounted) clipped into a High Voltage sample holder. Note that the sample is mounted at ~45° relative to the axes of the scanner, insuring domain contrast if the cantilever is scanned at either 0° or 90°.
Figure 2: Vertical PFM phase (a) and amplitude (b) overlaid on the rendered topography for the AR-PPLN Test Sample. Lateral phase (c) and amplitude (d) were imaged simultaneously. Imaging performed with an Olympus Electri-lever. 50μm scan.
Figure 3: PFM-DART (Dual AC Resonance Tracking) image of reversal domains created by applying negative 120V in a 6x6 square array, 6μm scan.