The underlying question that motivates my current work is, “What are the forces on atoms and ions associated with surfaces that result in these particles leaving or reattaching to the surface when stimulated with an outside agent?”
These surfaces may be surrounded by very high vacuum or by an aqueous solution. The stimulation that assists the motion of the atoms or ions may be a laser or electron beam, or it might be a very sharp, hard tip pushing on the surface. In all cases, the rate of particle removal or attachment, the speeds or energies of the particles involved, and even the direction they fly or attach, are of interest. With careful physical measurements we are able to detect these properties and compare the behavior of these particles with models based on fundamental physics and chemistry. Nevertheless, the details of how these particles are displaced are still poorly understood.
—Tom Dickinson, Professor of Physics
Think small. Think very small.
Dickinson studies surfaces at the nano-scale. Nano means one-billionth (10 -9). Dickinson uses an atomic force microscope to manipulate single atoms.
Going tribo.
Imagine trying to wash your dishes without water. Using mechanical means to clean dried food off a plate would be laborious. Using water and soap puts dishwashing in the science of “tribochemistry,” using both mechanical and chemical means to break the bonds of that dried food from the surface of the plate.
Dickinson uses tribochemistry in a “one-two” punch to break bonds on surfaces of selected materials. In the photographs, he has used an atomic force microscope and water to remove atoms from the surface of a piece of brushite, a biomineral the occurs naturally in the early stages of bone and kidney stone formation.
Why would anyone want to remove atoms from a surface?
Dickinson’s work is of great interest to the microchip industry. A process called “chemical mechanical planarization” is at the heart of the chip industry. Think polishing. Microchips have to be very smooth. In fact, chips are polished as many as 15 times during manufacturing. The details of how the process works, says Dickinson, are not well understood. Use too much abrasive material, and the chip’s destroyed. Rely too much on chemicals, and nothing happens. Put the two together, and you have CMP.
Sounds simple, right?
Again, think nano-scale. Smaller chips for smaller computers. This planarization process is an annual subject at three international professional meetings.