In the Tit-bit titled "Nanosizing RE: GaN while retaining optical properties", we saw that it is indeed possible to minimize the size of nitride particles while retaining the optical properties. This is done using a carefully designed ball-milling process (which is basically a clever way of hammering!). To enhance the engineering relevance of these nanoparticles, it is desirable to "paint" large surfaces with these tiny particles. This would enable use of these particles in devices such as surface conduction electron displays (SEDs). One of the ways to "paint" a substrate uniformly would be by using electric fields.

The idea of using electric fields to obtain particle coverage on a large surface area seems like an exotic idea at first, but the principle has been around since the early days of colloid chemistry and electrochemistry. Of course, getting the conditions just right to get a really flat layer of these particles is not that. That really requires quite a bit of hit and trial. The operational principle is the following: these nanoparticles, if carefully dispersed in a liquid will result in a stable colloid. These nanoparticles pick up a surface charge, while they bounce around in the solution. One can hence direct these particles by application of electric fields. We eventually succeeded getting fairly crackfree thin films of these nanoparticles. We are in conversations with some display-tech companies who seem interested in using our phosphors, and this large scale deposition technology.