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vibration control technologies
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Vibration isolators aid nano-research
As Seen In Electronics Talk
vibration control technologies
Nanoelectronics pioneer uses negative-stiffness vibration isolation technology to eliminate ultralow environmental frequencies and improve dataset integrity in nanoelectronics AFM research.
Vibration isolation is key to accuracy As nanotech applications become more diverse, the need for reliable vibration control has become increasingly critical, says Jim McMahon.
David K Ferry heads up the Nanostructures Research Group at Arizona State University (ASU) in Tempe, a collection of faculty, staff and students working on research in the regimes of nanolithography, and the physics of nanostructures and ultrasmall semiconductor devices. The group is a part of the University's College of Engineering, centre for Solid State Electronics Research, whose alumni makes up a serious constituency throughout the nanoelectronics universe, in both industry and academia.
Their current interests lie in the area of quantum dots, quantum wires, and ultra-small semiconductor devices in a variety of materials.The group conducts a wide spectrum of theoretical studies of quantum transport in these very small devices.
For example, they are doing a process called scanning gate microscopy at low temperatures.
This involves taking the equivalent of an atomic force microscope and putting bias on it, and studying the change in conductance of small semiconductor structures as they move this bias tip around on a surface.
Their system is mounted in a large cryogenic cooler, an enclosed container with a helium-3 cooling system, an isotope of a helium molecule - which is brought down to 300mK, or 1000x below room temperature, about one-half a degree above absolute zero.
Dr Ferry's group is using a process called a piezoelectric sensor.They metalicise the AFM cantilevered tip with a very thin layer of metal so they can apply a voltage to it.Then use that voltage to perturb the structure they are looking at.
As the tip moves it creates a voltage across the plane, which is measured to determine certain mechanical property values.This is a technique that was developed at Harvard four to five years ago.
This type of experimentation is not uncommon, similar experiments are being done by a large number of universities.But what is not common is the system that the Nanostructures Research Group is using for vibration isolation: negative-stiffness vibration isolation, developed by Minus K Technology - which provides a significantly greater and more stable attenuation of the critical lower vibration frequencies, and therefore more reliable accrued datasets.
When measuring a very few angstroms or nanometres of displacement, you have got to have an absolutely stable surface on which to rest your instrument.If you do not, any of that vibration coupled into the mechanical structure of your instrument will cause vertical noise, and fundamentally an inability to measure these kinds of high resolution features.
Any kind of vibration noise in the system makes that AFM cantilever tip move, and that gives you bad signals and incorrect data, says Dr Ferry.
We actually went further than most university applications because we integrated a rather large magnet into our system, something that Harvard, for example, is just now putting into their operation.
The magnet allows us to look at different types of transport.We can turn the magnet on and look at the magneto-transport of the semiconductors.It is a quite a different mode of transport altogether.
The entire system had to be isolated, not just the cantilever, continues Dr Ferry.We required an extremely high level of vibration isolation given our research parameters.We are deriving modern electronic devices from our experiments.Future electronic devices are our interest.
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