VS-LEIS Localized Electrochemical Impedance Spectroscopy

• Control voltage of a sample and use a dual-element probe to measure local current, leading to calculated local impedance 
• Sweep frequency at fixed position or Map area at fixed frequency
• LEIS provides spatial resolution to all the applications that benefit from EIS measurements
• Wide measurement bandwidth and high measurement accuracy combine to benefit local State-of-Charge (SoC) measurements and Coatings failure analysis

The VersaSCAN Scanning Electrochemical Workstation is a single platform capable of providing spatial resolution to both electrochemical and materials-based measurements.  This system integrates a positioning system, measurement instrumentation and probe to provide local information.  Traditional electrochemical experiments measure an average response over the entire electrode, electrolyte interface.  Rarely is a sample homogenous.  Samples often consist of local sites of passivate or active nature and sites of anodic or cathodic character.  This need to investigate localized phenomenon led to the emergence of scanning probe electrochemistry.

Positioning System:

• VersaSCAN is unique in the use of piezoelectric motors to drive the stages on all axes.
• Piezos are materials that move with very high precision, accuracy, repeatability but over small distances.  We use them to drive stages; therefore we reach a combination of scan area and scan resolution that is unmatched.
• AFMs do not move with the same scan range (usually piezo-element only; without the stage)
• Alternative positioning system designs use step motors, exclusive or as a basis for a hybrid system, and cannot move with the same resolution.

System Installation and Training:

This is full ‘white-glove’ service. An experienced team member arrives on site – unpacked the instrumentation, assembles, levels the system.  A developed checkout procedure is executed on a test sample to verify the system (installation).  The fundamentals of the technique are covered.  The users are trained to execute the same test (training).

Multi-Technique platform:

The VersaSCAN platform offers the ability to leverage the positioning system and software as common components for other scanning probe techniques.  The best-in-class measurement characteristics of AMETEK equipment combines with this unique positioning system for high-resolution measurements even at large areas.

The VersaSTAT 3F applies an AC voltage to the sample emerged in electrolyte. This "global" voltage generates AC current to flow at the electrode / electrolyte interface. A dual-element probe is positioned in solution close to the surface of the sample. The electrometer measures a differential voltage measure between the two measurement elements as a measure of local voltage-drop in solution. This voltage-drop exists in solution because of current flow from local reactions at the sample, the resistance of the electrolyte and the spatial separation of the dual measurement elements.

The VersaSCAN’s electrometer inputs its measured voltage to the Auxiliary Differential Voltage Input available with the VersaSTAT 3F.

Software integration converts the measured local voltage-drop at the probe to local AC current.

The ratio of local measured current to the global applied voltage gives the localized impedance magnitude and phase shift.

There are two different test methods for the experimentalist to use LEIS to evaluate their samples: 
A) Chart the local response of a sample from a range of applied AC frequencies in a single location. Data can be viewed in either a Bode or Nyquist representation.
B) Create a series of data maps to characterize an AC response as a function of probe position. Data can be used to create a map, using either Magnitude or Phase as the response

• Localized EIS measurements giving spatially resolved impedance analysis of substrates.

• Capable of Time-Resolved Imaging when programmed as a sequence

• Single frequency or multiple frequency sweeps for complete electrochemical characterization

 

VersaSCAN Positioning System

Specifications	VersaSCAN Base (VS-BASE)
Positioning System Range	X-axis:  100 mm Y-axis:  100 mm  Z-axis:  100 mm
Positioning Motor Technology	X-axis:  Piezoelectric motors,            no stepper-motor Y-axis:  Piezoelectric motors,            no stepper-motor Z-axis:  Piezoelectric motors,            no stepper-motor

LEIS Measurement Technology

Specifications	VersaSTAT3F
Voltage Measurement	Differential Auxiliary Voltage Input
Max Current Output	±2 A (standard) up to ±20 A
Compliance Voltage	±12 V
EIS Capability	1 MHz, Option
Min Current Range	± 4 nA (122 fA resolution) down to ±4 pA (122 aA)
E and I Filters	200 kHz to 1 Hz,  including None
Grounding	Floating, Isolated