Electron excitation refers to the movement of electrons from a lower energy state to a higher energy state. Such a phenomenon is possible by carrying out photoexcitation (PE) or by electrical excitation. In the former case, the original electron absorbs a photon and attains all the energy for itself. In the latter case, the original electron absorbs the energy of another energetic electron.
Inside every semiconductor crystal lattice, thermal excitation is a process where lattice vibrations can supply enough energy to cause electrons to achieve a higher energy band. The opposite process of electron relaxation is said to have happened when the high-energy electron falls back to a lower energy level. Such a reverse phenomenon occurs when a photon is radiated or the energy is given to a third spectator particle.
Properties of materials are known to change properties of materials. With techniques based on the concept of electron excitation, it is possible to remove surface material and deposit it for the purpose of coating or use it for analysis. The secondary ion mass spectrometry (SIMS) technique is one such process that makes use of the phenomenon of electron excitation. It is possible to deposit modify the layers on the surfaces of materials, like the case of diamond-like carbon films by the use of low-energy ions of nitrogen in order to remove hydrogen from surface hydrocarbons.
Other processes that make use of electron excitation are:
- The modification of the bulk of a certain material, like in the case of doping of silicon using neutron transmutation.
- The alteration of the rate of a chemical process, as seen in the effects of low-energy electrons that bring about silicon oxidation.
- The switching of one process to another.
- For damage production. This process may be desirable, as in the case of isolation of regions of a semiconductor device. An undesirable form of electron excitation is seen when the mechanical properties of a certain material are degraded, resulting in brittleness being caused.
Electron excitation can take several forms. It can involve a beam of ion, for instance, or be manifest in the selective excitation of the electrons by electromagnetic (EM) radiation. Experimental research continues to be carried out in this domain to come up with improved understanding of the role of electron excitation in chemical processes.