Two studies on carbon nanotubes by CEA DRECAM researchers have just been published in Physical Review Letters and Applied Physics Letters. The first study presents an innovative and experimentally verified theoretical law to predict and characterize the deformation of a carbon nanotube subject to an electrical field. The second study applies this knowledge to produce a nano-switch using innovative dimensioning and positioning control techniques.
MEMs technologies (microelectromechanical systems) combine mechanical, optical, electromagnetic, thermal and fluidic concepts with electronics to produce chip-based integrated systems performing sensor and/or actuator functions. MEMs are currently used in a large number of sectors such as the automobile industry (airbag sensors), the computer peripherals industry (inkjet printer cartridges), and also the defense, medical and space industries. These technologies accompany the advances in microelectronic miniaturization. For sizes less than one micron, the term NEMs is used (nanoelectromechanical systems). However, below a certain size, entirely different production techniques must be employed, one the one hand due to preeminent surface effects very difficult to control, and the other because the physics of the phenomena is susceptible to change in the quantic realm.
Carbon nanotubes are excellent candidates for the production of NEMs. The assembly of nano-objects is an elegant solution to the increasing difficulty of machining massive materials at nanometric scale. A few examples of carbon nanotube NEMs have been published in the literature over the past 4 or 5 years. However, the development of this field of research was limited by the absence of dimensioning control tools for carbon nanotube NEMs.
The study by CEA DRECAM researchers published in Physical Review Letters is an important first step toward the development of generic dimensioning tools for carbon nanotube NEMs. It concerns a carbon nanotube attached at both ends and suspended above a conductor support. When voltage is applied to the conductor, the nanotube is subject to an attractive electrostatic force and deforms. The CEA researchers have derived a scale law that links the deformation of the nanotube to geometric parameters (diameter, suspended length, suspension height) and electrostatic parameters (applied voltage, voltage potential waveform). This law enables the dimensioning of all NEMs based on suspended and electrostatically activated nanotube structures. The researchers were able to verify this law using a technique to directly measure nanotube deformations by atomic force microscopy.
In Applied Physics Letters, the CEA researchers announce the production of a nano-switch by combining knowledge of carbon nanotube deformation under the effect of an electric field with a technique enabling controlled positioning of nanotubes on a surface. When a voltage potential is applied to a carbon nanotube, it deforms and comes into contact with an electrode. Although various teams throughout the world have already produced a few nanocomponents, the NEMs developed at the CEA involved the implementation of techniques to control the positioning of the nanotubes. This is an additional step toward the controlled production of nanocomponents with predefined properties. In addition, once the nanotube is in contact with the electrode, the Van Der Waals interactions maintain the contact even under very low voltage, which can be advantageously used for the production of memories.
Many applications can be considered for NEMs based on suspended and electrostatically deformed nanotubes, ranging from ultra-low force sensors to oscillators and high-frequency signal switches for telecommunications. The nano-switch and the electronic control system must be integrated on the same chip. This hybridization problem is at the heart of NANO-RF, a new European project coordinated by the Federal Polytechnic Institute of Lausanne and involving the participation of various CEA laboratories , the CNRS, and three other European partners.
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