CHN gets a new AFM

My favorite days are the ones when I get to take field trips to labs. Last week, I was lucky enough to have two such expe­ri­ences in one day. In one, I even got to play sci­en­tist again by decking out in head-​​to-​​toe clean-​​room garb.

My reason for vis­iting the Center for High Rate Nanoman­u­fac­turing today was to see their new atomic force micro­scope, which was donated to CHN by the com­pany and will be avail­able for the entire North­eastern com­mu­nity to use. First I got a lesson in AFM, as those in the know like to call it, and then I got to see the instru­ment in person.

Stylin’ next to CHN’s new atomic force micro­scope. Can you tell how excited I am?

Every atom exerts a minis­cule force on its sur­round­ings, either pushing or pulling against what­ever is in its imme­diate vicinity. By imme­diate vicinity we’re talking angstrom scale — that’s some­where between a bil­lionth and tril­lionth of a meter. An AFM works by passing a tiny nanowire over the sur­face of a sample. Hanging from a minia­ture can­tilever, the wire moves up and down in response to these atomic forces.

Here the iPhone failed me a little. It’s blurry but it gives you a sense of the size. The can­tilever is vis­ible as a tiny line run­ning ver­ti­cally in the center of that little plate. The nanowire hangs off the can­tilever, per­pen­dic­ular to the plane of the image (your com­puter screen, I guess.)

A laser is focused on top of the can­tilever and bends in response to the nanowire’s move­ments. A photo detector trans­lates the angle of that light into data, resulting in a graph­ical image of the sur­face of the sample.

The kind of image the AFM produces.

CHN grad­uate stu­dent Hanchul Cho makes nan­otem­plates by lay­ering ele­ments like carbon nan­otubes onto a sub­strate. He needs to know exactly how many ele­ments have been deposited and how thick the tem­plates are in order to cal­cu­late the elec­trical prop­er­ties of the device. AFM is the method of choice for doing that.

The guts of the fancy new AFM.

Cho’s work is just one example of the many appli­ca­tions in which the micro­scope will be put to use at CHN said research sci­en­tist Siva Somu. It can also be used to figure out how tightly the nanoele­ments are bound to a sur­face and to deter­mine the effi­ciency of transfer when they move the ele­ments from a tem­plate onto a recip­ient substrate.

CHN already has one AFM, but it the new one, which is at the cut­ting edge of the tech­nology, over­comes some chal­lenges inherent to most AFMs. The new instru­ment is much better suited for extremely smooth sur­faces without sig­nif­i­cant step changes, said Cho.

Guts of the old AFM.

Cho, by the way, is great. He hails from Korea and has the lucky oppor­tu­nity to travel there for a ten day training ses­sion in using and main­taining the instru­ment. When he returns he’ll be the res­i­dent expert, so be sure to find him if you have any questions!

Cho and the AFM