Question

What do you mean by "artificial atoms". (b) why are they called so?

Answer 1

"Artificial atom" is a common name for quantum dots, which are usually small islands of semiconductor enclosed within a larger volume of some other semiconductor.

These are normally chosen so that electrons have a lower energy in the island than on the surrounding semiconductor, which means that at low temperatures you can trap electrons there. Moreover, with careful engineering, you can get these to behave essentially like single-particle confined quantum systems, with the same sort of features (like quantization of energy into a small discrete set of possible states) that atoms show, though on different scales. (For example, the fact that the length scales are much longer means that the quantized energy levels are generally much lower.)