STM Homepage

This page is dedicated to the new STM I am building as part of the Ray Ashoori group in the Department of Physics here at MIT. It's a bit preliminary right now: I'll be editing and enhancing it over the next couple of months.

Status

Feb 24: Walking is now working with the ramps. The tricks are: ramps have to be polished to a mirror finish, this mirror finish has to be coating with molebdenum disulphide powder, and the ramps have to be heavy enough (at least 17 grams). The ramps alone with no screw or sample platform are only 6 grams. They will not walk upwards like this. However, putting a 11 gram nut on top of them, they will walk up with no problem. Sweet.

Feb 20: All of the wiring for the piezos is now finished. The walking piezos are working, and I can walk around using a glass slide. I will now be working on getting walking working reliably with the ramps.

Design

Our STM is designed to be mounted on the end of a stick and run interchangably in our different low temperature rigs. The microscope I'm currently building is mostly a copy of our existing microscope. (See here for some information about the work we've been doing with it.)

The first modification was that the bore was reduced from 1.5 inches down to 0.959 inches to fit comfortably into the dilution fridge. The new design also added a threaded support for the scan tube, with the big advantage being that we can now interchange scan tubes to get different resolutions and scan ranges.

I plan on adding a lot to this section, including some figures and diagrams, in the future.

Results

None yet...but hopefully soon...

Pictures and Movies

Below are some pictures of the stick and the microscope, as well as some movies of my first walking test.

These are the walking piezos. This plate will later be mounted on the bottom of the microscope body can using screws.

The lower half of the stick. On the left are the seven SSMC connectors for the signal wires, and on the right are the connectors we use for the piezo voltage wires.

A close up of the peizo voltage connectors. They were made from samtec connectors. The wires are mangenin magnet wires.

A close up of the SSMC connectors. We used stainless steel coax for it's low thermal conductivity.

A NW16 to NW40 adapter turned out perfect for adding space for more SMA connectors at the top of the stick.

These are the ramps. The pitch angle on these is 4 degrees. They were polished to a mirror finish using 0.3 micron polishing paste and a dremel tool.

A picture of the ramps resting on the walking piezos.

On the bottom is the STM body, and above it is the large range scan tube.

A close-up of the long scan tube. The brass piece at the top screws into the microscope body.

Electronics boxes I've built for the STM. The top one is the breakout box. In the middle are the scan tube low pass filter box on the left, and the piezo switchbox on the right. The piezo switch box is used to change the walking mode of the bottom piezos: x tranlation, y tranlation, rotation, and ground all quadrands. At the bottom is a 500 MHz two channel analog multiplier box.

An mpg movie showing the piezos walking a roll of tape on top of a glass slide in the x dirction. Click on the image to see the movie. You should be able to view it using window media player in windows, or using gtv in linux.

This movie shows the piezos moving in rotational mode. Note that they are actually walking to the side a bit too: it turns out I had mixed up piezo's 2 and 3 when I wired the connectors at the bottom. I've rewired them now and it will now rotate without walking sideways.