VS-SVET Scanning Vibrating Electrode Technique

• Uses a Pt/Ir microelectrode to map the voltage-field in solution from local current events, such as corrosion pits or galvanic couples
• Our SR 7230 ensures superior signal measurement enabling high-resolution measurements

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 Scanning Vibrating Electrode Technique uses a single wire to measures voltage drop in solution. This voltage drop is a result of local current at the surface of a sample. Measuring this voltage in  solution images the current at the sample surface. Current can be naturally occurring from a corrosion or biological process, or the current can be externally controlled using a galvanostat.

A piezo unit vibrates the probe in Z-direction (axis parallel to the sample). The amplitude of vibration may be only 10s of microns peak-to-peak. This small vibration provides a very small voltage to be measured.

Therefore, the response (signal + noise) at the probe is then gained by the electrometer. The gained output of the electrometer is then input to a Lock-In Amplifier. This, in turn, uses a phase detector along with a Reference at the same frequency of vibration to extract the small AC signal from the entire measured response. The VersaSCAN capitalizes on Ametek’s industry-leading Noise Characteristics of the Signal Recovery 7230 Lock-In Amplifier to provide superior measurement of these small signals.

The voltage recorded and the probe is repositioned. A data map results as voltage versus position are displayed.

A key application of SVET is to study corrosion process of bare metals. These metals could be galvanic couples or these could occur from local non-uniform corrosion events, such as pits or crevices.

Time-lapse experiment series provide the capability to literally watch the corrosion events happen – as different areas passivate and activate.

Additionally, there are many applications and references for the use and results of SVET used in biological systems.

• Measures localized voltage gradient between tip and substrate for determination of localized current density.
• Developed for analysis of non-uniform corrosion events, such as pits, welds and galvanic couples.
• Capable of Time-Resolved Imaging when programmed as a sequence

 

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

SVET Measurement Technology

Specifications
Electrometer Range	± 10 Volts
Electrometer Gains	1x to 10,000x in decades
Piezo Vibration Unit	0 - 30 µm perpendicular to sample
SR 7230 Lock-in Amplifier
DSP Stability (not analog-based, impervious to temperature drift)
High Stability (no fan for failure)
Radically better Noise Sensitivity (13 fA/√Hz)