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Actuators Based on Quasi One-Dimentional Conductors

#3933


Micro- and Nanoactuators on the Basis of Quasi One-Dimensional Conductors

Tech Area / Field

  • INS-DET/Detection Devices/Instrumentation
  • INS-MEA/Measuring Instruments/Instrumentation
  • MAN-MAT/Engineering Materials/Manufacturing Technology
  • MAT-OTH/Other/Materials
  • NNE-MEC/Miscellaneous Energy Conversion/Non-Nuclear Energy
  • PHY-SSP/Solid State Physics/Physics

Status
3 Approved without Funding

Registration date
13.01.2009

Leading Institute
Russian Academy of Sciences / Institute of Radioengineering and Electronics, Russia, Moscow

Collaborators

  • CNRS / Institut Neel / Département: Matière Condensée et Basses Températures, France, Grenoble\nDalhousie University / Department of Physics and Atmospheric Science, Canada, NS, Halifax\nUniversity of Kentucky / Department of Physics & Astronomy, USA, KY, Lexington\nTU Delft / Kavli Institute of Nanoscience, The Netherlands, Delft\nFraunhofer Einrichtung Elektronische Nanosysteme, Germany, Chemnitz

Project summary

The main subject of the Proposal concerns the widely developing area of modern applied physics – development of nano- and microelectromechanical systems (NEMS-MEMS). Devices in this area annually find new promising areas of application. Some of the most exciting applications are nanomanipulators, optical commutators and scanners, various cantilevers for scanning-probe microscopes, vibration generators, mechanical processors of electric signal – hi-frequency filters, frequency etalons, nano-weights. All such devices require a source of motion – an actuator. The publications of latest years have demonstrated large efforts of different laboratories in order to develop highly effective low-voltage actuators of micron and nanometer dimensions. The basic forces for actuation are of electrostatic and piezoelectric (intrinsically, also electrostatic) nature. The abilities of such forces are limited, the resulting displacements of the NEMS-MEMS elements are also small, even brought to perfection. For nanosized piezoactuators measurable displacements could be achieved only in resonance modes. Electrostatic forces drop with the square of distance, which strongly limits the displacements.

The current Proposal is planned as the prolongation and development of the ISTC Project 3201, entitled “Elements for Micro and Nanoelectromechanics Based on the Whiskers of Quasi One-Dimensional Conductors and HTSCs”. In the course of the 3201 Project a new effect has been found, namely large torsional strain (TS) of a number of charge-density wave (CDW) compounds under electric field: in comparison with piezoelectric effect, the deformation for the same values of electric field is at least 4-5 orders of magnitude higher, though the nature of the TS is quite different. The unique nature of the observation consists also in the direct attainment of torsional deformation under the conditions of unform electric field. The effect is intrinsic for quasi one-dimensional conductors with charge-density waves (CDW). The main features and dynamical characteristics of the TS have been studied; variants of applications of the effect are being worked over in the course of the 3rd year of ISTC 3201. Recently, TS was observed also at room temperature and above it. So, quasi one-dimensional conductors with charge-density wave (CDW) can play the role of unique powerful actuators driven by electric field, and the NEMS devices listed in the 1st paragraph can become extremely effective if actuated by the CDW conductors.

Apart from TS, other kinds of deformations have been also observed and are being studied. The effects have been observed not only for whiskers, but also for bulk CDW crystals.

The current Proposal is focused on the elaboration of particular micro- and nanomechanical devices actuated by Quasi One-Dimensional Conductors. Construction of one of them – an optical microscanner – looks at present as a clear engineering objective. Other perspective applications, such as actuators for scanning-probe cantilevers, nanomechanical resonators and processors of electrical signal, etc, will be also worked through. In parallel, fundamental studies of the mechanical properties of the CDW conductors will go on. Here we would like to mention such exciting recently observed effects, as TS in the normal state of the CDW conductors, strong enhancement of TS induced by radio-frequency field and generation of vibrations under DC electric current. Also, laboratory NEMS structures, such as MHz frequency vibrators, will be performed.

The work on the Proposal will go in close cooperation with the Collaborators. Dr. P. Monceau is the world leading specialist in the physics of CDW conductors, including their mechanical properties. Dr. H. van der Zant has a unique experience in the construction of nanosized mechanical devices, including CDW-based. Torsional nanoresonators based on the whiskers of TaS3 and NbS3 will be manufactured jointly within the current Proposal. Apart from the two collaborators, participating in the Project 3201, prof. T. Geßner, the representative of the applied institution, specializing on the MEMS-NEMS fabrication, is joining the work in the frame of ISTC. Jointly, an optical microscanner, as well as other NEMS-MEMS devices will be elaborated. So, the new feature of the current Proposal in comparison with No 3201 is elaboration of particular systems.

Summering the main direction of the work within the Proposal we would mention the following items:

  1. Studies of TS at room temperature and above it. Here the results for NbS3, which is in the Peierls state, and for some other compounds (TaS3, (TaSe4)2I,…), in which TS is attributed to the CDW fluctuations, will be gained and compared. The reason of such a large deformation in the normal state will be found. Fundamental results are expected. Also, compounds for the most efficient room-temperature actuators will be selected – either in the Peierls state (NbS3), or in the state of ‘fluctuative’ CDW.
  2. Studies of effects of RF and microwave radiation on the TS of different CDW compounds. Preliminary results show that such irradiation increases the amplitude of TS by an order of magnitude. Also, strong effects on TS are expected in the mode of Shapiro steps – synchronization (cohering) of the CDW motion under the irradiation. The effects are of fundamental interest, as they can help to understand, which kind of CDW deformation results in TS, and what are the contributions of different parts of the samples. The applied expectation is the growth of the amplitude, quality factor and cut-off frequency of the torsional oscillations under the RF and microwave radiation.
    A special goal is the excitation and studies of high-frequency torsional oscillations (see also item 5 below). A lock-in amplifier for the 10 MHz range coupled with a photodiode will be elaborated and constructed for the optical detection of the oscillations. Here the most intriguing issues would be the synchronization of the mechanical oscillations with the fundamental frequency of the CDW sliding, either in the conditions of the Shapiro steps or without external RF irradiation. Also, effects of low-frequency noise generated by the sliding CDW on the TS will be searched for and studied: here noise-like vibrations of the samples under DC electric current are expected.
  3. Studies of the TS and other kinds of deformation by means of the cryogenic (down to 10 K) high-vacuum AFM elaborated and constructed within the ISTC project 3201. The unique device will enable the following research unattainable before: studies of different kinds of deformations down to liquid-helium temperatures with the sensitivity to the displacement ~1 nm. Mostly, fundamental results are expected: analyzes of the sample deformation as a whole and of its behavior at low temperatures.
  4. Synthesis of the CDW compounds. Firstly, NbS3 and TaS3 whiskers will be synthesized. The technology will be perfected for growing of single phase crystals with coherent CDW showing the highest TS. Growth of large samples (needed, e.g., for the microscanning systems) will be also one of the goals.
  5. Development and characterization of electromechanical nanostuctures with utmost parameters: dimensions, frequencies, quality-factors. Torsional pendulums will be fabricated on the basis of the CDW whiskers ~1-10 μm length and <0.1 μm thickness. The oscillations will be actuated directly by passing currents through the whiskers and detected by micromirrors and the feedback signal. The structures will be fabricated and studied jointly with the collaborating organization – Nanoscience Department of Delft University of Technology. Oscillations in the MHz range are expected to be detected. The resulting structure will be the basis for development of a number of NEMS devices.Another direction here is development of an FIB (focused ion beam) set-up in IRE for fabrication of mechanical micro- and nanostructures. Apart from thinning of the whiskers, one of the goals is preparation of needle-like samples from K0.3MoO3 (the blue bronze) and some other CDW compounds synthesized as bulk crystals. Preliminarily, the blue bronze has demonstrated high TS under electric field.
  6. Development of laser scanning devices for projecting television-like set-ups. This elaboration is based on the scanning set-up already produced in the Fraunhofer Research Institution Elektronische Nanosysteme (ENAS), Chemnitz, one of the collaborating organizations. The set-up developed in Chemnitz is actuated by electrostatic forces. The central point of the work planned is to substitute the actuator with a whisker demonstrating TS at room temperature (see item 1). The resulting device is expected to exceed the original one at least by an order of magnitude in the ratio angle/voltage; it is also expected to demonstrate in practice the actuating properties of the CDW whiskers.
  7. Development and characterization of other NEMS elements: cantilevers, including self-sensitive ones, mechanical processors of electric signal, nano-weights, manipulators.

The participants of the Proposal are experienced in studying the CDW compounds, including (thermal) expansion and actuating properties. They are also specialists in development and operation of complex scanning-probe and optical devices, including cryogenic ones. This is confirmed by the successful march of the Project 3201. The Russian group will be in permanent contact with the collaborators, as it is clear from above.

The enumerated research directions are exclusively civil-oriented. They are expected to find application in the scanning microscopy, fabrication of micro- and nano-manipulators, generators of mechanical oscillations, in measurement technique. We cannot see prospects of military application of the research proposed. Realization of the presented Project will permit most of the participants from IRE to reorient their activity from weapon to peaceful sphere. Collaboration with the laboratories from different countries will promote better understanding between countries. The applied direction of the research will promote partial switching of the science in Russia to the market relations. Thus, the activities within the Project proposed doubtlessly answer the goals and objectives of ISTC.


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