Using Laser Technology to Decrypt the Cause of Micro Electronic Heating
In the 1970s, a man named Gordon Moore predicted his performance in the semiconductor industry by doubling the chip's performance every 18 months. This prediction over the past 40 years all the way to prove his right, and the transistor density of the chip also followed by doubling, doubling, and then double. For people who are familiar with the chip, high-performance is usually associated with this high fever, with our dependence on electronic products increasing, mobile phones, laser 5000mw,flat panel, notebook computers and other heating problems, not only negative impact on the experience, The manufacturers to design a more beautiful, lightweight new products.
To solve the electronic products, especially micro-electronic devices of the heat, we must first understand the root causes of these heat generated. And the answer may be hidden in the latest paper published by Dr. Liao Linlin. The former Sichuan Province college entrance exam tutor from Professor Chen Gang, this year from the Massachusetts Institute of Technology received a doctorate. His research team accurately measured the interaction between electrons and phonons, the results not only explain the micro-electronic equipment, the causes of fever, but also can be used to further improve the performance of thermoelectric materials.
With the development of semiconductor chips, more and more transistors are stuffed into smaller and smaller spaces. Massachusetts Institute of Technology engineers recently found that mobile phones, laptops and other electronic devices will be hot, the main reason is that electronic and thermal energy to carry the phonon interaction. This interaction was once overlooked by scientists, but the latest research results show that in microelectronic devices, this interaction has a significant impact on heat dissipation, the related research results published in the October 12 of the "Nature Communication ".
In the 1970s, a man named Gordon Moore predicted his performance in the semiconductor industry by doubling the chip's performance every 18 months. This prediction over the past 40 years all the way to prove his right, and the transistor density of the chip also followed by doubling, doubling, and then double. For people who are familiar with the 3000mw laser pointer chip, high-performance is usually associated with this high fever, with our dependence on electronic products increasing, mobile phones, flat panel, notebook computers and other heating problems, not only negative impact on the experience, The manufacturers to design a more beautiful, lightweight new products.
Thermoelectric materials have a very wide range of applications, including thermal detectors and NASA's latest proposed for space exploration equipment, nuclear batteries. The phenomenon of electron scattering by phonons is not new, but has long been neglected by scientists. With the continuous development of semiconductor technology, the concentration of electrons becomes higher and higher, this phenomenon can not be ignored. Scientists must think about how to manipulate the electron-phonon interaction in order to increase the efficiency of the thermoelectric device on the one hand and prevent the microelectronic device from heating up on the other.
Phonon and electronic bumper car games
Whether in 20000mw laser transistors (semiconductor materials, such as silicon) or wire (conductor material, such as copper), the electronic current movement is the main medium. The reason why resistors exist is that the electrons flow through a roadblock - a phonon carrying thermal energy collides with electrons, pushing it out of the current path. For a long time, scientists have been investigating the effects of electron-phonon interactions, but the focus has been on electrons rather than on how the interactions affect phonons. "Scientists rarely study the effects of this interaction on phonons, because they think this effect is not important," Liao Lin said, "but Newton's third law tells us that each force has a reaction force, but we do not know what The reaction will become important. "
Scattering, heat is difficult to coexist
According to Liao and colleagues, when the electron concentration exceeds 1019 electrons per cubic centimeter, the interaction of electrons and phonons in silicon, the most commonly used material in semiconducting materials, can produce a large scattering of phonons. When the electron concentration reaches 1021 per cubic centimeter, the heat dissipation capacity of the material will be reduced by phonon scattering by 50%. "This is a very significant effect, but many people are doubtful," Liao Lin Lin said. This is mainly because in previous experiments with high concentrations of electronic materials, scientists have assumed that the cooling capacity of the decline is not due to electron - phonon interaction, but due to material defects caused. These defects are due to the doping of materials, silicon, for example, phosphorus and boron are commonly used doping atoms, the purpose is to increase the material's electron concentration. Therefore, to verify Liao Linlin's theory, it is necessary to separate the electron-phonon interaction and the influence of defects on heat dissipation capacity. The specific method of implementation is to increase the electron concentration in the material, but not to introduce any defects.
The team developed a technique called three-pulse photoacoustic spectroscopy to optically increase the concentration of electrons in silicon crystal thin films and measure phonon production in the material Of any impact. The technique is an extension of the traditional "two-pulse photoacoustic spectroscopy" in which the scientists accurately control the timing of the two blue laser pointer beams. The first beam produces phonon pulses in the material and the second beam measures the scattering or attenuation of the phonon pulses. Liao Linlin introduced a third laser beam, which can accurately increase the electron concentration in the silicon material without introducing any defects. After the third laser beam is emitted, the measurement results show that the phonon pulse decay time is significantly shortened, which indicates that the electron concentration increases the phonon scattering and inhibits its activity.
The experimental results show that the introduction of the third burning laser pointer can shorten the decay time of the phonon pulse. The larger the laser intensity (the higher the electron concentration), the shorter the decay time of the phonon pulse. The result was a great excitement for Liao Lin's team, which was a good match for their previous calculations. "We can now determine the effect is very obvious, and we confirmed it in the experiment," Liao Lin Lin said, "This is the first can directly detect the electron - phonon interaction on the impact of phonons experiment." Interestingly, The concentration of 1019 electrons per cubic centimeter, than some of the existing transistor is even lower, in other words, the latest discovery of this phenomenon is part of the existing microelectronics fever one of the culprits. "According to our research, this effect will become increasingly important as the size of the circuit gets smaller," says Liao. "We must seriously consider this effect and study how to use or avoid its effects."
