What is a Quantum Dot?
A quantum dot is a particle having an approximate size of one nanometer which has the display properties of a semiconductor. A semiconductor is a solid material that possesses some amount of electrical conductivity. Silicon is one of the most popular materials used in creating a quantum dot. The size of the quantum dot, one-billionth of a meter, can cause it to exhibit unusual properties that are not present in larger samples of a semiconductor material. These properties could have some benefits to humans including, but not limited to, energy and light production. Unlike some forms of nanotechnology, the quantum dot is not theoretical. It has been created in a real-world setting. The key to the quantum dot is in the electrons. Electrons occupy one of two bands in a material’s crystal. By providing the proper stimuli, an electron, or perhaps more than one, can be encouraged to move from one band to the other. As it moves from one band to the other, it creates a hole, which is positively
Introduction Quantum dots are tiny crystals that have been carefully crafted to control the movement of electrical charge within them. Each quantum dot is extremely small; several million quantum dots could fit into the width of a person’s thumb. Quantum dots can be produced in many different shapes and with many different chemicals, but they all share the ability to glow, or fluoresce, when light is shined on them. Quantum dots with different structures will glow in different colors, and scientists can now make quantum dots in almost every color of the rainbow including white. Since quantum dots are a fairly new technology, they are not yet widely used in many areas, but they show a lot of promise for applications in a wide range of industries. In the near future, quantum dots will likely be used in fields as diverse as medicine, home lighting, and generating electricity. How Quantum Dots Work At the heart of how a quantum dot works is its ability to constrain the movement of electric
Confinement of few electrons: Quantum Dots (QDs) are solid state structures made of semiconductors or metals that confine a countable, small number of electrons into a small space. The confinement of electrons is achieved by the placement of some insulating material(s) around a central, well conducting region. If the insulation of the QD is strong enough and if the QD is small enough quantum mechanical effects due to the discrete electron charge and/or discrete electron energies can be observed macroscopically. QDs have therefore also been called artificial atoms. Neighboring, weakly coupled QDs have been called artificial molecules. Critical Energies: Quantum dots used in electron transport experiments are typically characterized by energies needed to add a single enelctron. The device arrangement has to be such that the energy needed to add a single electron to the dot is large compared to the thermal environment energy kT. This electron addition energy (E) can be understood to consi
Asked by: Jean-Sébastien Answer Imagine a piece of pure semiconductor. Electrons in this bulk are free to move around, in three dimensions. In solid state physics, these electrons are sometimes referred to as an electron gas. It is possible to constrain the movement of the electrons by disallowing one dimension — that is, by reducing one degree of freedom. The electrons can then move freely in only two dimensions. A system of electrons confined to a plane is called a two-dimensional electron gas, or 2DEG. Quantum wires have only 1 degree of freedom, and quantum dots have 0 degrees of freedom. It is important to note that confinement is not perfect. A quantum dot is often defined as confinement to a very small volume of space, such as a sphere that has a diameter on the order of the material’s Exciton Bohr Radius. At this size the energy bands of the semiconductor are no longer continuous, which results in the confinement. Quantum confinement gives rise to many interesting effects, and
