Using an SEM to Statically and Dynamically Investigate the Chemical Quartering of a Piezoelectric Tu

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Using an SEM to Statically and Dynamically
Investigate the Chemical Quartering of a
Piezoelectric Tube

• Matthew Sztelle
• Research Assistant for Professor Joe Lyding
• Scanning Tunneling Microscopy Group Beckman
  Institute

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STMs Need Piezoceramics

• Insulating Ceramic
• Change Dimensions to Applied Electric Fields
• Motion is Linear in the Angstrom Regime w/
  Respect to Voltage
• Work Horse of the Scanning Tunneling Microscope
  (STM)

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Our Application Piezo-Tubes

• Geometric Concerns Cylindrical
• Material PZT-5A (Lead Ziconate Titanate)
• Nickel Coated
• 4 Axial Cuts Provide x y Manipulation

Inner Piezo-Tube (x-y Manipulation)
Tip Assembly
Tip Holder
Base Assembly
Tip
Axial Cut
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Our Situation

• Early 90s
• Initial Batches Displayed Strong Spatial
  Response to Applied Fields
• Tubes Came As Is and No Further Work Required
• No Outside Test Desired or Required Before Scope
  Assembly
• Late 90s
• Newer Batches Response to Applied Field Less
  Robust Than Previously Seen

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What Was Different?

• Initial Observation Revealed Axial Cuts
  Significantly Deeper
• However, Nothing Conclusive

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Motivated ESEM Analysis

• Static Test
• Allows High Resolution Images of the Surface
• Possible to Accurately Determine Depth of Cut
• Possible to See Cracks and Fissures
• Dynamic Test
• Electrical Feedthrough
• Observe Displacement of Tube Under Applied Voltage

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Dynamic ESEM Test Procedure

• Solder Lead Wire to Each Quadrant
• Stick to Viewing Surface With Tape
• Feed Lead Wires Through Feedthrough to Power
  Supply
• Find Edge of Tube in ESEM
• Apply Voltages At Increments and View Motion

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SEM Results

• Old Tubes
• Shallower Cuts
• Approximately 60 um of Motion Under 150V Applied
  Bias
• New Tubes
• Deeper Cuts
• Approximately 10 um of Motion Under 150V Applied
  Bias

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SEM Conclusions

• Depth of Cut May Be an Issue
• Mechanical Stress is Clearly an Issue
• The Quartering Method Employed by the Company Can
  Not Meet Our Rigorous Specifications

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In-House Quartering Methods

• Scribe Using Diamond Carbide Knife
• Machine Shop Tools With Precision
• Chemical Etching
• Wax and Acid Bath
• Photo-Resist and Acid Bath

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Stress Fissures at Scribe Marks
Typical Fissures Seen From Mechanical Scribing
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Fissures In Piezo Bulk Material
Larger Than Normal Fissure
Typical Bulk Fissure
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Chemical Etching

• Significant Advantage Vs Other Techniques
• No Mechanical Stressing of the Tube
• Disadvantages
• Labor Intensive
• Lines Not as Pure as Mechanical Solutions

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Etching Procedure

• Cover Tube in Beeswax
• Scribe Line in Wax With Needle
• Place in 11 Mix HClHNO3
• Remove Wax
• Repeat 3 More Times
• Take to SEM for Analysis

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SEM Results

• Nothing to See No Visible Cracks or Fissures
• Best Dynamic Response Equivalent to Half That of
  Old Tubes
• However, Not All Dynamic Responses Were Equal

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Conclusions

• Clearly Our New Technique Causes No Mechanical
  Stress to Tube
• Work Pending
• Investigation of Test Set-up
• Not the Same as Previous Test Set-up
• Not Time Tested Either
• Actual Live Testing of Tube In Microscope

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Acknowledgements

• Professor Joe Lyding
• Nathan Guisinger
• Jixin Yu
• Scott Robinson
• STM Nanofabrication and Characterization Group
  (University of Illinois)
• ONR Multidisciplinary University Research
  Initiative (MURI)