Characterization of VO2 films grown on a 3-inch r plane sapphire substrate
Penn State Materials scientist have just discovered a way to give the workhorse transistor a big boost, using a new technique to incorporate vanadium oxide, one of a family of materials called functional oxides, into the device.
Vanadium dioxide have an unusual property: metal-to-insulator transition. In the metal state, electrons move freely, while in the insulator state, electrons cannot flow. This on/off transition, inherent to vanadium dioxide, is also the basis of computer logic and memory.
Benchmark of VO2 thin films.
If they could add vanadium oxide close to the transistor it could boost the transistor’s performance. Likewise, by adding it to the memory cell, it could improve the stability and energy efficiency to read, write and maintain the information state. The major challenge they faced was that vanadium dioxide of sufficiently high quality had never been grown in a thin film form on the scale required to be of use to industry, the so-called wafer scale. Although vanadium dioxide looks simple, it is very difficult to synthesize. In order to create a sharp metal-to-insulator transition, the ratio of vanadium to oxygen needs to be precisely controlled. When the ratio is exactly right, the material will show a >4X magnitude change in resistance, enough for a sufficiently strong on/off response.
The Penn State team reports for the first time the growth of thin films of vanadium dioxide on 3-inch sapphire wafers with a perfect 1:2 ratio of vanadium to oxygen across the entire wafer. The material can be used to make hybrid field effect transistors, called hyper-FETs, which could lead to more energy efficient transistors. Addition of vanadium dioxide provided steep and reversible switching at room temperature, reducing the effects of self-heating and lowering the energy requirements of the transistor + benefit existing memory technologies
A selector insures that reading or writing information on a memory chip is done within a single memory cell, without bleeding over into neighboring cells. It works by changing the resistivity of the cell, which vanadium dioxide does extremely well. In addition, the change in resistivity of vanadium oxide can be used to significantly increase the robustness of the read operation. The vanadium dioxide thin film material grown with this method has also been used to make super high frequency switches. http://www.newswise.com/articles/electronics-get-a-power-boost-with-the-addition-of-simple-material
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