Hi, this is an introduction to Mini-course 2. Here, we're going to look at certain aspects of the unit cell. We'll talk about, the packing factor, planar density. It's important to understand these things because they dictate properties. In case if I build a bipolar transistor, I build it on a 111 plane, and I build MOSFET transistors, I've built it on a 001 plane. Different planes have different properties. When I build my device, they will have different properties. The bipolar, I want to make it go faster, crank up the current MOSFET. Which are the majority of our devices these days, I want to go fast and make them smaller. With that, we have to understand these things about the unit cell. Because the unit cells properties, they are not just for the unit cell, they translate to the bulk. Understanding yourself, now I understand bulk properties. Like atomic density. Atoms per centimeter cubed, for the unit cell has translate to the bulk. If I measured the atoms per centimeter cube for a piece of copper and I hold in my hand, that's going to be almost the same as the unit cell. You say, why is it different? Well, there are these things called defects. These defects will influence slightly those measurements. We will look at defects from zero d, what we refer to them by the dimensionality. Zero defects, 1, 2, 3 d defects. Then we'll look at how these deep bags will employ certain properties, say, the dislocation, how it glides and causes mechanical deformation. We'll also look at these defects in silicon, where we intentionally introduce them to alter the electrical properties. In certain cases, certain materials, we will introduce them to alter the optical property. Lot of times we just want to be able to control the effects, can't get rid of them. I can't get rid of all, but we can actually introduce them and control them, to actually alter the property. Again, we're looking at this thing called structure processing property. That's what we want to understand. How can I alter the material, to alter the properties by altering the structure?
