When you look at the performance curve of computer CPU according to the year of production, a variant that is known as "Moore's Law", we see that the clock speed, which was 3 GHz in 2002, was ... 3 GHz in 2007, when it should have been 24 GHz! One reason for this stagnation - that was remedied by increasing the number of cores - is looking to increase the power dissipation and thus temperature, in processors, as their size decreases . The problem affects both the performance, because the leakage currents at the gates of transistors increases exponentially with temperature, and operating costs, including large data centers, where costs associated

The proposed solutions is the leading manufacturer of thermoelectric or Pettier effect. Discovered in 1834 by Jean-Charles Pettier, this physical phenomenon that depends on a driver in the bearing of heat and electricity are the same entity, the electron at the same time, the amount of heat transported per unit charge is function of the material. If you think a junction between two conductors, and if one applies a potential difference at the ends of the junction, we obtain an electric current, which is obviously continuous through the junction. The flow of heat, it is not generally the same in different materials: heat flux is discontinuous at the junction, resulting in the appearance of a source or of Heat a well as the sense current. The junction can operate as a heat pump. Another way to describe the mechanism is as follows: at equilibrium, the Fermi levels of the two materials and electrons are transferred from one material to another. This creates an electric field which opposes the passage of electrons, and achieves a steady state. By polarizing the junction, electrons must overcome a difference in electrical potential additional. If it strengthens the initial electric field, electrons have to spend more energy to overcome, and is extracted from the heat.

The resulting cooling can reach 40° C, and the Pettier modules are used in many applications that require a cool environment with little space: portable fridges, cameras, satellites and other spacecraft ... and computer components. Two materials that are commonly used for thermocouples (whose operation is based on another thermoelectric effect) are tellurium and bismuth. Recently, an article in Nature Nanotechnology announced the completion of a Pettier module comprising a multilayer structure in which thin films of super networks of bismuth telluride and antimony telluride (type p) alternate with super networks basis of pure bismuth telluride and selenium doped (n type). The structure is deposited by vapor phase epitaxy to metalloid-organic, on a GaAs substrate.

The advantage of this thermoelectric module compared to those made with silicon and germanium is not so much in efficiency, since the authors of the article, said a cooling of about 15° C, still far 40 degrees theoretically possible. Indeed, components Si / Ge generally show a sharp deterioration in performance once integrated into the back of the chip, which is not the case with the new component.

The technique, certainly promising, was developed in the Intel labs in Arizona, in collaboration with Arizona State, and two companies of North Carolina.