From the Transistor to the Integrated Circuit
The characteristics and states of the electrons in a solid form of matter, such as thermal conductivity, elasticity, and chemical reactivity, are substantially governed by their characteristics and states. Quantum effects play a decisive role here as well.
Quantum physics, among other things, provides a precise explanation for the electrical conductivity of objects, including semiconductors. Their conductivity is intermediate between that of electrical conductors (like copper) and non-conductors (like porcelain), but it may be significantly affected by a variety of factors.
Changing the temperature of some semiconductors, for example, modifies their conductivity in a way that differs from what happens in metals: it increases rather than decreases as the temperature rises.
Doping (the technique of introducing foreign atoms into their crystal structure) can also have a substantial impact on their conductivity.
Micro transistors are thus little more than a collection of differentially doped semiconductor components whose mode of operation is primarily dictated by the flow of electrons within them.
All of this, once again, is based on quantum physics rules.
Semiconductor components are the foundations of all electronics, as well as the computer and information technologies that have such a significant impact on our lives today.
They are packaged in billions on little chips in "integrated circuits," allowing very sophisticated electronic circuits to be coupled on parts as small as a few square millimeters (e.g., in microprocessors and memory chips).
Individual parts of these integrated circuits nowadays are made up of only a few hundred atomic layers (about 10 nm thick) and everything that happens inside them is governed by quantum physics.
Today's chips for computers, mobile phones, and other electronic gadgets could not be made without the help of quantum physics.
The tunnel effect is an example of a quantum phenomenon that is extremely essential in micro- scope transistors and diodes:
Quantum particles can cross a barrier with a high probability, even though they don't have the energy to do so according to conventional physics. Simply put, the particle penetrates through the energy barrier.
In our macro world, this means that if we fired a thousand rubber arrows against a lead wall, some would materialize on the other side, and we'd be able to calculate exactly how many arrows there would be.
Quantum tunneling is a strange property with very real and significant implications in today's modern world.
This is because when the distances between the conductive portions of circuits are reduced to 10 nm or less, difficulties arise: electrons tunnel uncontrolled, causing interference.
Engineers must devise a variety of strategies to avoid this. They mix multiple materials, for example, to trap electrons, making them less prone to tunnel.
Meanwhile, scientists have perfected the calculation of the tunnel effect to the point that they can build “tunnel-effect transistors” (TFETs) whose operation is solely dependent on the tunnel effect. Because the "tunnel current" may be manipulated as well.
In current microelectronics, the tunnel effect of quantum physics plays a fundamental role—on the one hand, as a barrier to ever-increasing downsizing, and on the other, as the foundation of a new transistor technology.
Aside from solids' electrical conductivity, common qualities like color, translucency, freezing point, magnetism, viscosity, deformability, and chemical properties, among others, can only be understood using quantum physics rules.
Without understanding of quantum phenomena, solid state physics would be impossible to comprehend.
Physicists continue to discover startling effects and behaviors, as well as amazing new macroscopic quantum phenomena that open the door to new applications. Superconductivity, for example, is the total elimination of electrical resistance in some metals at temperatures near absolute zero.
The “BCS theory,” named after John Bardeen, Leon Neil Cooper, and John Robert Schrieffer, who devised it in 1957, can explain this phenomenon, which was originally seen in 1911 and can be described by a specific many-particle quantum theory termed “BCS theory.”
(As a result, John Bardeen became the first and only person to win a second Nobel Prize in physics, in addition to the one for discovering the transistor effect.)
However, researchers found in 1986 that the temperature at which certain materials begin conducting electric current without resistance is substantially higher than the temperature at which all previously known superconducting metals begin carrying electricity without resistance (and this was rewarded by another Nobel Prize only one year later).
This event, like many others in quantum physics, is not fully understood (BCS theory does not explain it), yet it has enormous technological promise.
The goal of quantum engineers is to discover superconducting compounds at room temperature. This would allow power to be delivered across whole countries and continents with no energy loss—current power networks lose roughly 5% of their energy.
You may also want to read more about Quantum Computing here.
