Classes

ME 498 (FA20) Project (3 credit hours): Humidity Controller

Project title: Low noise humidity controller for nanoscale imaging
Course title: Humidity Controller

Project Description

The objectives of this project are to:

  1. Develop and test a low noise humidity controller.  
  2. Use the humidity controller to study the effect humidity on microscopy based electrical measurements.

An atomic force microscope (AFM) consists of a cantilever mounted, nanometer scale tip interacting with a surface.  In AFM, nanoscale imaging is obtained by scanning the tip over the surface.  If an electrical potential is applied to the tip, the electrical properties of the surface can be probed. 

The presence or absence of water on a surface mediates tip-surface interactions in AFM.  For example, a water layer that forms between the surface and tip will affect the contact area, conductivity, capacitance, stiffness, and adhesion of the contact between the tip and sample.    In turn, these variations affect AFM measurements of resistance, conductance, piezoelectricity, ferroelectricity, and electrostatic forces.  A low noise, fast controller that uses PID control to adjust the humidity of the imaging environment would be a valuable tool for understanding interactions between the surface, water, and tip.  The goal of this project is to build a humidity controller and use it to study the effect of humidity on electrical AFM measurements.

Figure: (a) A low noise system for generating a flow of humid air [1]. (b) Piezoresponse force microscope (PFM) image of ferroelectric switching of a hafnium zinc oxide film by a locally applied voltage [2]. This is an example of a measurement the humidity controller will be used to study.

References:

[1] Gaponenko, I., Gamperle, L., Herberg, K., Muller, S. C., & Paruch, P. (2016). Low-noise humidity controller for imaging water-mediated processes in atomic force microscopy. Review of Scientific Instruments, 87(6), 063709. https://doi.org/10.1063/1.4954285
[2] Cheema, S. et al. (2020). Enhanced ferroelectricity in ultrathin films grown directly on silicon. Nature, 580. https://doi.org/10.1038/s41586-020-2208-x
[3] https://engineering.purdue.edu/~rbwagner/

Applicant Requirements

  • Junior or senior standing
  • GPA greater than or equal to 3.0
  • Sufficient time to devote to the project, approximately 9 to 12 hours per week.
  • A desire to undertake design and manufacturing work.

Project Responsibilities

  1. Review the prior literature on humidity control methods and electrical atomic force microscopy methods
  2. Design a humidity controller.
  3. Build the humidity controller.  
  4. Demonstrate performance of the humidity controller.
  5. Work with collaborators to use the humidity controller to study the influence of humidity on electrical AFM measurements.
  6. Help prepare a manuscript summarizing the results.

Grading Criteria

A: Satisfactory completion of project responsibilities 1-5.
B: Satisfactory completion of project responsibilities 1-4.
C: Satisfactory completion of project responsibilities 1-3.
D: Satisfactory completion of project responsibilities 1-2.
F: Completion of project responsibilities 1 or less.

Interested? Contact Professor Wagner (rbwagner@purdue.edu)

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