مره اخري اقول اننا علي اعتاب ثورة تقنية جديدة وهذا عدد هذا الشهر ، ديسمبر ٢٠١٤ مع خالص تحياتي وتقديري يا اهل النانو واوعوا تناموا مجدي Home > Publishers > AIP Publishing > Physics Today > Daily edition > Enterprise > Post AVS 2014: Moving beyond silicon with unconventional electronics Northwestern University researchers explore novel materials to create innovative printed electronics. Laurel Hamers December 2014 PREVIOUS POSTENTERPRISENEXT POST facebook twitter Share this page separator email print this page Enterprise: AVS 2014: Moving beyond silicon with unconventional electronics Brewing scientific knowledge at Carlsberg IPF 2014: The entrepreneurial professor IPF 2014: Detecting stealth crop diseases IPF 2014: Industrial physics goes global While electronic devices have become steadily smaller over the past few decades, moving from the room-sized computers of the mid-20th century to the pocket-sized smartphones of today, the circuits that make them up are still somewhat rigid. “Each time a company like Intel wants to change a chip, it takes millions of dollars, and yet the New York Times is reprinted each day,” said Northwestern Universitys Tobin Marks during the plenary lecture of the American Vacuum Societys 61st annual meeting. But what if creating a circuit was as cheap and easy as printing a newspaper? Marks is one of a growing group of researchers trying to bridge this gap and to create stable electronics that can be printed rapidly and inexpensively. The building blocks of small-scale circuits like those used in computers and modern electronics are tiny transistors, which can amplify current or switch it on and off. When combined by the thousands, as they are in computer chips, they allow computers to carry out complex operations rapidly. The Marks lab is searching for innovative materials that can improve the performance of these transistors and, ultimately, the devices in which they are found. One avenue of research moves toward improving the semiconductors used in the circuits. Organic semiconductors have several advantages over the more commonly used inorganic ones. They’re cheaper, making them better suited to covering large areas, and they can be flexible. But whereas the best semiconductors have a high density of charge carriers with high mobility, organic semiconductors tend to have lower charge mobility, limiting their usefulness. The Marks lab tackled this challenge, creating a collection of stable organic semiconductors with high electron mobility. Marks envisions that these semiconductors could be used as an ink and printed onto flexible plastic sheets to create electronic newspapers or cheap mass-produced RFID tags. In a flashier project, Marks lab researchers are developing amorphous oxides, organic semiconductors that are optically transparent and mechanically flexible. Such materials could be used to make inconspicuous—almost invisible—circuits and devices. The Marks lab isn’t focusing solely on semiconductors, though. They’re also working on a new type of dielectric, an insulating layer that stabilizes the charge carriers in the semiconductors. A good dielectric decreases the voltage that a transistor needs to function, making it more efficient. Silicon dioxide has traditionally been used as the gate dielectric in semiconductor technology, but when electronics are scaled down—and the SiO2 layer becomes too thin—it becomes a less effective insulator. Tobin Markss lab built this graphene field-effect transistor (G-FET) on a four-layer self-assembled nanodielectric (SAND) on top of a silicon substrate. (a) Schematic. (b) Chemical structure of the organic PAE molecule sandwiched between hafnium or zirconium oxide layers. (c) Optical micrograph of several two-probe G-FETs on a four-layer hafnium-SAND. The black scale bar corresponds to 250 μm. (d) Magnified optical micrograph of a G-FET, where the dashed black line outlines the patterned CVD graphene. (e) Representative Raman spectrum of CVD graphene on a Hf-SAND. (The figure was taken from V. K. Sangwan et al., Appl. Phys. Lett. 104, 083503, 2014.) Tobin Markss lab built this graphene field-effect transistor (G-FET) on a four-layer self-assembled nanodielectric (SAND) on top of a silicon substrate. (a) Schematic. (b) Chemical structure of the organic PAE molecule sandwiched between hafnium or zirconium oxide layers. (c) Optical micrograph of several two-probe G-FETs on a four-layer hafnium-SAND. The black scale bar corresponds to 250 μm. (d) Magnified optical micrograph of a G-FET, where the dashed black line outlines the patterned CVD graphene. (e) Representative Raman spectrum of CVD graphene on a Hf-SAND. (The figure was taken from V. K. Sangwan et al., Appl. Phys. Lett. 104, 083503, 2014.) To solve this problem, the group searched instead for a material with a higher dielectric constant—that is, an intrinsically greater ability to store charge. In response, they developed self-assembled nanodielectrics (SANDs), made up of self-assembling layers of crosslinked organosilane molecules. The SANDs work well with both organic and inorganic semiconductors, and function at a lower voltage than traditional dielectrics. This makes them well suited to use in a variety of efficient devices, especially since they can be printed at temperatures low enough to be used on plastic surfaces. The researchers are working to commercialize their novel electronic circuitry, bringing them from the lab to the real world through a startup company, Polyera, which offers a growing library of materials with which tech manufacturers can advance their products. Laurel Hamers is an intern in the media services division of the American Institute of Physics. COMMENTS START THE CONVERSATION
Posted on: Mon, 08 Dec 2014 16:24:51 +0000
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