A new vista in spintronics was opened in 2004 with the observation of the spin Hall effect in GeAs at 20 K by David Awschlom and his group. In the spin Hall effect the electrons of a charge current flow in a nonmagnetic conducting material in the absence of an external magnetic field. An applied […]
Let’s take a p-type semiconductor with a very clean surface and place it right next to the clean surface of a n-type semiconductor. This type of device is called an n-p junction diode , or simply a diode . What happens? Scientists realized that the electrons in the conduction band of the n-type semiconductor are […]
Ionization is a fundamental process in chemistry and physics, lying at the heart of many fascinating phenomena. Ionization is the process of producing ions. Certain molecules ionize in solution, for example. But ions may also be formed when an atom or molecule loses one or more electrons as a result of energy gained in a […]
The most extensive use of semiconductors, such as silicon or germanium, including their use as transistors, arises from their behavior when, after being sufficiently purified of atoms other than the basic element (e.g., silicon or germanium), very small amounts of special impurities are carefully introduced. While the methods for first purifying then adding small amounts […]
Chemistry • Computer science • Condensed matter • Materials • Physics
A visionary perspective of molecular electronics is the use of single molecules as functional entities in electronic devices. In this context, some of the most important components are molecular switches, which are molecules that can be interconverted reversibly between at least two stable states, one for the OFF and one for the ON. In order […]
The most prevalent use today of semiconductors is forming them into transistors, the basic electronic building blocks of all “solid-state electronics” and computer microchips. Semiconductors are the most important materials in the burgeoning revolution in computers and other electronic devices today. Such applications also arose, beginning in the 1930s, from the quantum mechanics of the […]
The interactions between moving charges and magnetic fields can be quite complicated; more if we consider the quantum effects. One example is the collection of Hall effects. There are analogues of these effects for spin and the detection of the most sophisticated one in graphene, where, at least, it should not be strong, is something […]
Quantum mechanics was founded upon the existence of the wave–particle dualism of light and matter, and the enormous success of quantum mechanics, including the probability interpretation, seems to reinforce the importance of this dualism. But how can a particle be thought of as “really” having wave properties? And how can a wave be thought of […]
The band theory of metals has been subjected to experimental tests many times and is now the accepted model of the behaviour of conductors and insulators. But it has to be modified when it comes to superconductivity. Electrical resistance is due to collisions of the electrons (whether treated as particles or waves) with impurities, imperfections […]
In the early days of organic chemistry, the word aromatic was used to describe fragrant substances such as benzene (from coal distillate), benzaldehyde (from cherries, peaches, and almonds), and toluene (from tolu balsam). It was soon realized, however, that substances classed as aromatic differed from most other organic compounds in their chemical behaviour. Today, the […]