Researchers develop integrated nanomechanical sensor for atomic force microscopy

June 2, 2011
Researchers develop integrated nanomechanical sensor for atomic force microscopy
Scanning electron micrograph of the cantilever-microdisksystem. The image has a calculated z-component of the magnetic field overlaid on the structure. 

( -- The atomic force microscope (AFM) is an important tool for nanoscale surface metrology. Typical AFMs map local tip-surface interactions by scanning a flexible cantilever probe over a surface. They rely on bulky optical sensing instrumentation to measure the motion of the probe, which limits the sensitivity, stability, and accuracy of the microscope, and precludes the use of probes much smaller than the wavelength of light.

As reported in , CNST researchers have fabricated a novel integrated sensor combining a nanomechanical cantilever probe with a nanophotonic on a single . Replacing the bulky laser detection system allowed them to build cantilevers orders of magnitude smaller than those used in conventional AFMs.

Because each of these smaller structures has an effective mass less than a picogram, the detection bandwidth is dramatically increased, reducing the system response time to a few hundred nanoseconds.

While probe was kept comparable to conventional microcantilevers in order to maintain high mechanical gain (how much the tip moves when it senses a force change), the probe size was reduced to a mere 25 µm in length, 260 nm in thickness, and only 65 nm in width.

Readout is based on “cavity optomechanics”, with the probe fabricated adjacent to a microdisk optical cavity at a gap of less than 100 nm. Due to this close separation, light circulating within the cavity is strongly influenced by the motion of the probe tip.

The cavity has a high optical quality factor (Q), meaning that the light makes tens of thousands of round-trips inside the cavity before leaking out of it, all the time accumulating information about the probe’s position.

The combination of small probe-cavity separation and high Q gives the device sensitivity to probe motion at less than 1 fm/√Hz, while the cavity is able to sense changes in probe position with high bandwidth.

The entire device is nanofabricated as a single, monolithic unit on a silicon wafer. It is therefore compact (chip-scale), self-aligned, and stable.

Fiber optic waveguides couple light into and out of the sensor, so that it can be easily interfaced with standard optical sources and detectors.

Finally, through simple changes to the probe geometry, the mechanics of the probe tip can be greatly varied, allowing for the different combinations of mechanical gain and bandwidth needed for a variety of AFM applications.

Explore further: Outsmarting light

More information: Optomechanical transduction of an integrated silicon cantilever probe using a microdisk resonator, K. Srinivasan, et al., Nano Letters 11, 791-797 (2011).

Related Stories

Outsmarting light

October 13, 2005

A team of scientists headed by Dr. Christoph Lienau of the Max Born Institute for Nonlinear Optics and Short Pulse Spectroscopy (MBI) in Berlin develops and utilizes novel nanoptical techniques for imaging structures that ...

Nanoscale zipper cavity responds to single photons of light

June 4, 2009

Physicists at the California Institute of Technology have developed a nanoscale device that can be used for force detection, optical communication, and more. The device exploits the mechanical properties of light to create ...

IBM Scientists Effectively Eliminate Wear at the Nanoscale

September 7, 2009

( -- IBM scientists have demonstrated a promising and practical method that effectively eliminates the mechanical wear in the nanometer-sharp tips used in scanning probe-based techniques. This discovery can potentially ...

Researchers Holding Steady in an Atomic-Scale Tug-of-War

March 31, 2010

( -- How hard do you have to pull on a single atom of -- let's say -- gold to detach it from the end of a chain of like atoms?* It's a measure of the astonishing progress in nanotechnology that questions that ...

Recommended for you

New nanomaterial maintains conductivity in 3-D

September 4, 2015

An international team of scientists has developed what may be the first one-step process for making seamless carbon-based nanomaterials that possess superior thermal, electrical and mechanical properties in three dimensions.

Graphene made superconductive by doping with lithium atoms

September 2, 2015

(—A team of researchers from Germany and Canada has found a way to make graphene superconductive—by doping it with lithium atoms. In their paper they have uploaded to the preprint server arXiv, the team describes ...

Making nanowires from protein and DNA

September 3, 2015

The ability to custom design biological materials such as protein and DNA opens up technological possibilities that were unimaginable just a few decades ago. For example, synthetic structures made of DNA could one day be ...

For 2-D boron, it's all about that base

September 2, 2015

Rice University scientists have theoretically determined that the properties of atom-thick sheets of boron depend on where those atoms land.


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.