Magneto-Optical Kerr Effect
Bi-Axial MOKE Measurement Stage
I designed and 3D printed this stage for making repeated Magneto-Optical Kerr Effect measurements in both Polar (left) and Longitudinal (right) orientations. Magnetic thin films grown on silicon wafers are temporarily attached to a microscope slide. The slide is then inserted into the base in the desired orientation. The screws in the front right and back left allow the stage to pitch back and forth on two orthogonal axes. This provides all necessary adjustment when switching between samples or orientations, allowing the laser source and the detection device to remain fixed in place. This design significantly reduced set-up time between consecutive MOKE measurements in our lab, and allowed me to collect all of the data for my 2016 FRAMS poster in less than a week.
CPW-FMR Measurement Apparatus
Over the summer of 2018 I designed and assembled a complete system for conducting Ferromagnetic Resonance measurements with a coplanar waveguide. I 3D printed a fixture to hold the CPW between the poles of an electromagnet, and to reduce stress on the cables carrying the microwave signal. I also coded LabVIEW programs to control the measurement and to fit the complex data using the Levenberg-Marquardt algorithm. Fitting the data to a complex function (rather than splitting it into real and imaginary components) requires fewer unknown variables and consequently produces a more accurate fitting result.
Projector Photolithography Apparatus
For many tests our lab conducts, it is necessary to use photolithography to pattern samples before deposition. These patterns can be made incredibly small with advanced manufacturing techniques, but often times millimeter scale patterns can be useful as well. Instead of relying on a professional manufacturer to produce large patterned samples for us, we've managed to replicate the entire process in our lab. This has saved us hundreds of dollars and countless hours between prototypes, and allows us to modify parameters and observe same day results.
We use a retired classroom projector as our light source, and a combination of laser-cut acrylic and 3D printed parts to elevate it above the exposure stage and direct the light downwards. These rapid manufacturing processes are relatively easy to get started with, and have allowed us to significantly improve both the look and function of our lab. The array of tapped holes on the table allow us to fix custom-made alignment components to the surface, such that repeated exposures will be under near identical conditions.
Laser Cut Lithography Masks
Thinner sheets of laser cut black acrylic are used as masks to transfer custom patterns onto silicon wafers coated in photoresist. The mask pictured can be rotated 180 degrees after the first deposition, in order to deposit an adjacent set of lines which are a constant distance from the original (see image below). The micrometer adjustor and associated 3D printed parts in the left of the picture allow us to precisely control the line separation.
The university's new Innovation space has a student accessible laser cutter, and it's less than a block away from our research lab. Since learning to use the machine, I've become capable of making and testing several masks in a single day before settling on my final design. This has been a huge improvement over our previous approach, and has led to significantly better measurement quality as well.
With this device we have the ability to measure the electric behavior of a thin film samples while manipulating a variety of conditions:
- In-plane magnetic field, with 360 degrees of rotation and programmatically controlled magnitude
- Perpendicular-to-plane magnetic field with programmatically controlled magnitude
- Perpendicular-to-plane temperature gradient
- Hand-wrapped electromagnet capable of switching perpendicular-to-plane (z) magnetization
- Air gap to allow z magnet to rotate with xy magnet, independent of the measurement stack
- Custom milled water cooling block with slim profile
- Thermo-electric cooler (transfers energy from cooling block to sample)
- Aluminum block with embedded thermocouple, to measure top temperature and help with uniform heat transmission from TEC
- Insulating tape, to prevent the sample from touching the aluminum block
- Test sample, deposited on a silicon wafer approx. 1mm thick
- Thermal tape to affix the sample to the cold block and encourage heat flux
- Aluminum block with embedded thermocouple, to measure bottom temperature and help with uniform heat transmission
- Thermo-electric cooler (transfers energy from sample to cooling block)
- Water cooling block, to take heat from the hot side of the TEC
The entire stack is locked in place on a custom 3D printed holder, while the magnet array is capable of rotating around it. This allows us to test nearly every magnetic configuration imaginable without modifying the test stack whatsoever. Furthermore, tests from different configurations can be directly compared, considering that the conditions aside from the magnetic field remain unchanged between tests.
In-Plane Temperature Gradient
Using many similar components, as well as a custom-machined pair of sample clamps, I have built an apparatus for measuring samples with the temperature gradient flowing in-plane.
Again, a combination of Acrylic and ABS parts were custom made to enclose the magneto-thermo-electric measurement apparatus. This enclosure keeps the water cooling components (the computer fan and copper coil in the left of the photo) away from the ongoing measurement, and prevents drafts of air from affecting the sensitive thermal conditions under which we conduct our studies. With the box around the apparatus, we are capable of maintaining temperature gradients exceeding 50K across a silicon wafer (>1mm thick) with negligible fluctuation.
Snap Fit Front Panel
This series of 3D printed parts allows the front panel of the enclosure to snap onto the remaining pieces, as well as provide support for the lid. I particularly like this exhibition of parts because all of the print striations are oriented in different directions. 3D printed ABS is incredibly versatile, and can tolerate repeated stress very well. The flexible part of this assembly still shows no signs of wear, and all of the tapped holes work as well as the first time they were used.