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11-10 :: October 2011
nanotimes News in Brief
A recent study carried out by researchers from the University of Girona, with the support of laborato- ries operated by the University of Barcelona and the French National Centre for Scientific Research (CNRS) has revealed that the energy of amorphous silicon – the state in which it exhibits the greatest stability – is 50% lower than the value commonly accepted until now. In the study published in the Physica Status Solidi–Rapid Research Letters, diffe- rential scanning calorimetry was used to measure the energy of 20 samples grown by several depo- sition techniques. It was found that although dif- ferent values were obtained for samples deposited in the same way, the minimum value coincided for all deposition techniques. This fact, together with observations based on previous studies, has led to the conclusion that the value of the minimum energy corresponds to the relaxed state. The value obtained is 50% lower than the standard figure ac- cepted until now and is a crucial finding for specia- lists in amorphous silicon structure, since theoretical models will be more or less realistic depending on their proximity to this value.
F. Kail, J. Farjas, P. Roura, C. Secouard, O. Nos, J. Ber- tomeu, P. Roca i Cabarrocas: The configurational ener- gy gap between amorphous and crystalline silicon, In: Physica Status Solidi – Rapid Research Letters, Vol. 5(2011), Issue 10-11, November 2011, Pages 361-363, DOI: 10.1002/pssr.201105333: http://dx.doi.org/10.1002/pssr.201105333
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A collaboration between researchers at the Univer- sity of Surrey’s Advanced Technology Institute and the Faculty of Mechatronics of Warsaw Uni- versity of Technology in Poland reports that low electrical loss at frequencies of up to 220 GHz are possible in screen printed carbon nanotube- polymer composites. Producing such low electrical loss materials potentially opens up new types of high frequency large area electronic devices.
Building upon previous EPSRC-funded research in carbon nanotube polymer composite electronics, this study shows that CNT composites have elec- trical losses of less than 0.3 dB/mm over a wide frequency range. Embedding CNTs in a polymer, in this case PMMA, allows accurate control of the nanotube content and control over the conductive phase of the composite which was screen printed into coplanar waveguides to produce structures tens of mm in length. Using a screen printing technology allows for ease of scalability for production and relaxes many of the constraints found in high end manufacturing techniques. Possible applications include new types of microwave mixers, phase shifters and antennas.
Dr. David Carey from the Advanced Technology Institute of the University of Surrey said: “The success of the research is to be found by employing the unique high frequency electrical characterisati- on facilities at Surrey to explore electrical conduc- tion in large area carbon nanotube based compo- sites. Understanding what controls the conduction at the nanometer scale in these new materials can lead to the development of new high frequency carbon nanotube based electronics.”