Semiconductor Contact
If metal touches a semiconductive material, or if two different semiconductors are placed into contact, one becomes charged slightly positive and the other slightly negative. It is found that if this junction between semiconductors is connected to a power supply, and if the power supply is set to a voltage slightly higher than the natural voltage appearing because of contact electrification, then for one polarity of voltage there will be a current between the two semiconductor parts, but if the polarity is reversed, the current stops. Thus contact electrification leads to the invention of the diode or rectifier and triggers the revolution in Semiconductor electronics and physics.
In materials with a direct band gap, if bright light is aimed at one part of the contact area between the two semiconductors, the voltage at that spot will rise, and an electric current will appear. When light meets contact electrification, the light energy is changed directly into electrical energy, allowing creation of solar cells. Later it was found that the same process can be reversed, and if a current is forced backwards across the contact region between the semiconductors, sometimes light will be emitted, allowing creation of the LED.
Read more about this topic: Contact Electrification
Famous quotes containing the word contact:
“I stand in awe of my body, this matter to which I am bound has become so strange to me. I fear not spirits, ghosts, of which I am one,—that my body might,—but I fear bodies, I tremble to meet them. What is this Titan that has possession of me? Talk of mysteries! Think of our life in nature,—daily to be shown matter, to come in contact with it,—rocks, trees, wind on our cheeks! the solid earth! the actual world! the common sense! Contact! Contact! Who are we? where are we?”
—Henry David Thoreau (1817–1862)