The new approach comes with a snappy name: chiplets. You can think of them as something like high-tech Lego blocks. Instead of carving new processors from silicon as single chips, semiconductor companies assemble them from multiple smaller pieces of silicon—known as chiplets.
The technique involves cutting microfluidic channels into the die of FPGA devices, which were chosen for the research and trials because of their flexible configuration and extensive use in the military. Effectively this locates the cooling just microns from the problem, and even allows for the possibility of chip-stacking, which very few devices currently have the room or efficiency to achieve, given the necessity to dissipate heat from a central locus of adjacent chips.
The researchers used a cellulose material for the substrate of the chip, which is the part that supports the active semiconductor layer. Taken from cellulose, a naturally abundant substance used to make paper, cellulose nanofibril (CNF) is a flexible, transparent and sturdy material with suitable electrical properties.
In a conventional chip, the support substrate is made of the same material as the active layer, but in the CNF chip, only the active layer is semiconductor material
You can see such symmetry breaking in a once-common 20th century technology: the two-wire ribbons used during television’s first few decades to send RF signals from rooftop VHF antennas to television sets without any loss. The electric RF current in the two conductors flow in opposite directions and have opposite phase. Because of the translational symmetry (the two conductors are parallel) the radiation fields cancel each other out, so there is no net radiation into space. But if you would flare the ends of the two conductors at one end of the ribbon, they aren’t parallel anymore and you break the translational symmetry. The two electric fields are no longer aligned and don’t cancel each other out, causing the RF signal to be converted into electromagnetic radiation.
The simplest place to start is the materials. Silicon is incredibly important as a material in the industry because it’s a semiconductor. Of course, the name is self-explanatory, but there’s more to it. The key here is the band structure. Band structure refers to the “bands” of energy levels that form due to the sheer number of orbital states that can be occupied in molecules. Those that understand how electron orbitals work will point out that each energy level is discrete, but due to the sheer number of orbital configurations, a seemingly continuous distribution of energy can be seen. However, relatively large gaps still exist; known as a band gap, these are an energy state that an electron cannot occupy.
And on and on it goes. This is a great writeup for understanding how integrated circuits work.
This year’s Nobel Laureates are rewarded for having invented a new energy-efficient and environment-friendly light source – the blue light-emitting diode (LED). In the spirit of Alfred Nobel the Prize rewards an invention of greatest benefit to mankind; using blue LEDs, white light can be created in a new way. With the advent of LED lamps we now have more long-lasting and more efficient alternatives to older light sources.
When Isamu Akasaki, Hiroshi Amano and Shuji Nakamura produced bright blue light beams from their semi-conductors in the early 1990s, they triggered a funda-mental transformation of lighting technology. Red and green diodes had been around for a long time but without blue light, white lamps could not be created. Despite considerable efforts, both in the scientific community and in industry, the blue LED had remained a challenge for three decades.
It turns out that when you shrink a Vacuum transistor to absolutely tiny dimensions, you can recover some of the benefits of a vacuum tube and dodge the negatives that characterized their usage. According to a report in IEEE Spectrum, vacuum transistors can draw electrons across the gate without needing a physical connection between them. Make the vacuum area small enough, and reduce the voltage sufficiently, and the field emission effect allows the transistor to fire electrons across the gap without containing enough energy to energize the helium inside the nominal “vacuum” transistor. According to researchers, they’ve managed to build a successful transistor operating at 460GHz — well into the so-called “Terahertz Gap,” which sits between microwaves and infrared energy. The “gap” refers to the fact that we have a limited number of devices that can generate this frequency and only a handful of experimental applications for this energy band.
Thermoelectrics are slabs of semiconductor with a strange and useful property: heating them on one side generates an electric voltage that can be used to drive a current and power devices. To obtain that voltage, thermoelectrics must be good electrical conductors but poor conductors of heat, which saps the effect. Unfortunately, because a material’s electrical and heat conductivity tend to go hand in hand, it has proven difficult to create materials that have high thermoelectric efficiency—a property scientists represent with the symbol ZT.
The key to the ultralow thermal conductivity, Kanatzidis says, appears to be the pleated arrangement of tin and selenium atoms in the material, which looks like an accordion. The pattern seems to help the atoms flex when hit by heat-transmitting vibrations called phonons, thus dampening SbSe’s ability to conduct heat. The researchers report the results today in Nature.
The Oxford team, led by physicist Henry J. Snaith, made their solar cells using perovskites, a class of mineral-like crystalline materials that has recently grabbed much attention among researchers in photovoltaics. Perovskites have properties similar to inorganic semiconductors and show sunlight-to-electricity conversion efficiencies of more than 15%.
To understand how current flows in a material you first have to understand electrons behave in a material. The key feature of solid state physics is that many materials are crystals. This means that the atoms are spaced periodically. As you mention, band structures are the way that we summarize the effect of this periodic potential. Basically, a band structure just relates an electrons momentum p=mv=hbar k to its energy. The momentum can be positive or negative, the sign only denotes direction. In free space this is very boring, Energy=m v2 /2 = p2 /2m=hbar k2 /2m. When you throw in a periodic potential, this becomes modified and results in bands. Actually calculating band structures is quite difficult. The key idea is that there are ranges of energy where the electron can live and ranges of energy where the electron cannot live.