Summary

In the study of physical properties, nanostructures often provide the best or the only testing ground for phenomena in fields such as quantum mechanics and condensed-matter physics. In electronic devices, there is a trend to use smaller numbers of electrons to get a taks done. With devices that emit light such as laser diodes, the emission wavelengths must be controlled. To improve both types of devices, structures that exploit quantum mechanical behavior are an option. This is achieved by reducing the size of the structure. If only one dimension is made small, the electron will only be partially confined; it will still behave as a free electron in the remaining two large dimensions. Quantum structures are, therefore, classified by how many dimensions provide confinement or, inversely, how many dimensions allow free-electron behavior. If a structure provides confinement in one dimension, it is called a quantum well. If a structure provides confinement in two dimensions, it is called a quantum wire. If a structure provides confinement in three dimensions, it is called a quantum box or quantum dot. Although the quantum mechanics are well established, the creation of quantum structures, in particular, quantum dots, is difficult.