Transistors - Page 2

Researchers at Northwestern University, MIT, Harvard University, CIFAR Azrieli Global Scholars Program and Japan's National Institute for Materials Science have developed a graphene-based synaptic transistor capable of higher-level thinking.

The device simultaneously processes and stores information just like the human brain. In new experiments, the researchers demonstrated that the transistor goes beyond simple machine-learning tasks to categorize data and is capable of performing associative learning.

An international team of researchers, including scientists from University of California San Diego, Chinese Academy of Sciences, University of Texas Medical Branch and University of Illinois Urbana-Champaign, has developed a handheld, non-invasive graphene-based device that can detect biomarkers for Alzheimer’s and Parkinson’s Diseases. The biosensor can also transmit the results wirelessly to a laptop or smartphone.

The biosensor consists of a chip with a highly sensitive transistor, made of a graphene layer that is a single atom thick and three electrodes–source and drain electrodes, connected to the positive and negative poles of a battery, to flow electric current, and a gate electrode to control the amount of current flow. Image credit: UCSD

The team tested the device on in vitro samples from patients. The tests reportedly showed the device is as accurate as other state-of-the-art devices. Ultimately, researchers plan to test saliva and urine samples with the biosensor. The device could be modified to detect biomarkers for other conditions as well.

Archer Materials, a semiconductor company advancing the quantum computing and medical diagnostics industries, has demonstrated multiplexing readout for its advanced Biochip graphene field effect transistor (“gFET”) device.

Archer confirmed single-device multiplexing using four advanced gFETs as sensors, which were integrated into the Archer advanced Biochip platform. This is significant as Archer intends to apply its multiplexing capability in the Biochip to test for multiple diseases on a single chip at once.

Researchers at Graphenea, University of Utah and Kairos Sensors have examined a perovskite-based graphene field effect transistor (P-GFET) device for X-ray detection. 

The device architecture consisted of a commercially available GFET-S20 chip, produced by Graphenea, with a layer of methylammonium lead iodide (MAPbI₃) perovskite spin coated onto the top of it. This device was exposed to the field of a molybdenum target X-ray tube with beam settings between 20 and 60 kVp (X-ray tube voltage) and 30–300 μA (X-ray tube current). Dose measurements were taken with an ion-chamber and thermo-luminescent dosimeters and used to determine the sensitivity of the device as a function of the X-ray tube voltage and current, as well as source-drain voltage. 

A research team from the University of Illinois Urbana-Champaign and the University of California has reported that the friction on a graphene surface can be dynamically tuned using external electric fields. 

The team studied the friction at a single asperity nanoscale contact between the graphene surface of graphene FETs and an AFM tip in a dry nitrogen atmosphere, while the doping level of graphene was modulated in situ by changing the potential applied to the device’s back gate. In contrast to conducting or insulating contacts, graphene in contact with semiconducting tips exhibits an enhanced and tunable friction sensitive to the charge density in graphene.

Archer Materials has had its advanced graphene field effect transistor (“gFET”) chip design validated by a commercial foundry partner in the Netherlands with a whole four-inch wafer run.
 

The new advanced gFET device designs have been fabricated and the whole wafer run foundry process was reportedly successful. The electronic and spectroscopic characteristics of the gFET chips, and the foundry fabrication process yield, are said to be consistent with what Archer expected. The gFET chips are also compatible with Archer’s biochip system platform.

A team of researchers, led by the University of Wisconsin-Milwaukee, recently developed a path to mass-manufacture high-performance graphene sensors that can detect heavy metals and bacteria in flowing tap water. This advance could bring down the cost of such sensors to just US $1 each, allowing people to test their drinking water for toxins at home.

The sensors have to be extraordinarily sensitive to catch the minute concentrations of toxins that can cause harm. For example, the U.S. Food and Drug Administration states that bottled water must have a lead concentration of no more than 5 parts per billion. Today, detecting parts-per-billion or even parts-per-trillion concentrations of heavy metals, bacteria, and other toxins is only possible by analyzing water samples in the laboratory, says Junhong Chen, a professor of molecular engineering at the University of Chicago and the lead water strategist at Argonne National Laboratory. But his group has developed a sensor with a graphene field-effect transistor (FET) that can detect toxins at those low levels within seconds.

Researchers from Seoul National University of Science and Technology (SeoulTech) and Kwangwoon University recently used a novel approach called UV-assisted atomic layer deposition (UV-ALD) to treat graphene electrodes. The choice of this technique resulted in the successful production of a high-performance graphene-dielectric interface. 

The research team became the first to apply UV-ALD to the deposition of dielectric films onto the surface of graphene. Atomic layer deposition (ALD) involves adding ultra-thin layers at the atomic scale to a substrate, and its significance has grown considerably as semiconductor components have shrunk in size. UV-ALD, which combines ultraviolet light with the deposition process, enables more dielectric film placement than traditional ALD. However, no one had explored the application of UV-ALD for 2D materials such as graphene.

Researchers from Shanghai Jiao Tong University, Chinese Academy of Fishery Sciences,  BOKU-University of Natural Resources and Life Sciences, University of Oslo and Oslo University Hospital, MIT, 2bind and Avalon GloboCare have designed a novel sensor that could detect the same molecules that naturally occurring cell receptors can identify.

The researchers created a prototype sensor that can detect an immune molecule called CXCL12, down to tens or hundreds of parts per billion. This is an important first step towards developing a system that could be used to perform routine screens for hard-to-diagnose cancers or metastatic tumors, or as a highly biomimetic electronic “nose,” the researchers say.

Archer Materials has reported the completion of a proof-of-concept biosensing graphene transistor for use in its biochip, and submitted the technology
design to a commercial foundry to verify scalability.

Archer’s optical lithography has electrodes, bond pads, and other graphene componentry, that allow the biochip’s sensor device design to scale more easily to produce complete wafers in collaboration with commercial foundries. The Archer-designed gFET sensing chips will be produced by a commercial foundry, with the aim of Archer validating its design to ensure appropriate scalability for the manufacturing process.