ARAC

ARAC

Atomic resolution at ambient conditions

Atomic resolution at ambient conditions

A cutting-edge exploratory platform designed for pioneers

Aiming at developing tools that perfectly match the need of a researcher, Nanosurf fosters the direct exchange of ideas and novel concepts. Originating from such collaboration between industry and academia, ARAC is a high-end platform for researchers to explore new approaches to measuring at the atomic scale. Designed for maximum flexibility, it provides the perfect toolkit to assemble an individual purpose-built experimental system.

We are eager to work with you on developing new measurement techniques and are happy to hear about any challenging scientific questions you would like to address.

  • Prof. Franz Giessibl

    “Among all physical quantities, time and frequency can be measured with the greatest precision. I am happy to see that with the qPlus sensor, Nanosurf brings this precision, which is inspired by Swiss time keeping technology, to atomic force microscopy in ambient conditions.” — Prof. Franz Giessibl

System overview: ARAC scanhead with mounted optics module, together with CX controller and high voltage amplifier

Features

  • qPlus Sensors: self-sensing probes with a high spring constant enabling small amplitudes in the range of inter-atomic distances.
  • High-resolution 10 µm x 10 µm x 3 µm sample scanner.
  • No perturbing light sources thanks to the all-electronic readout.
  • High resolution optical access through the optics module (50x, NA=0.55).
  • Sample scanner: ideal for experiments such as tip-enhanced optical experiments.
  • Lowest-noise electronics with user-definable inputs and outputs (CX Controller).

qPlus Sensor working principle

The heart of the ARAC system is the qPlus Sensor, a self-sensing force sensor based on the piezoelectricity of α-quartz. It features extraordinary stiffness between 1 kN/m and 30 kN/m, allowing to probe high force gradients without the risk of snapping-into-contact. Moreover, the stiffness enables vibration amplitudes smaller than interatomic distances such that the measurements can be carried out close to in the repulsive force regime with a high sensitivity to short-range forces enabling high resolution imaging.

The all-electronic readout of the self-sensing qPlus Sensor ensures that the read-out is tuned to the optimum without the hassle of accurately positioning the laser spot on a beam-deflection system.

Modular and flexible

The ARAC exploratory platform is built up from five distinct modules: qPlus sensor holder, housing, scanner, housing positioner and a granite base. Thanks to the modularity, modifications for specific requirements, e.g. an upgrade of the optics module or the active vibration isolation, are effortlessly possible.

The minimum space required to operate the ARAC (w/o top view microscope and base) is 16 cm x 16 cm.

Nanosurf CX Controller: lowest noise and additional flexibility

Fast and simultaneously low-noise electronics are of paramount importance for high-precision systems like the ARAC. Noise translates directly into poor image quality, either via the scan-piezos or via the sensor excitation and readout.

Furthermore, low-latency evaluation of the measured interaction is required for fast feedback algorithms. The CX Controller meets these demands thanks to its fast and low-noise electronics and its highly performant processor. State of the art signal handling allows for atomic resolution with a lateral scan range as large as 12 µm. The numerous user inputs and outputs allow for recording additional signals from external sources.

  • User-definable inputs: 4 high-resolution inputs (20 bit, 1 MS/s) and 1 fast input (16 bit, 100 MS/s)
  • User-definable low-noise outputs: 4 high-resolution outputs (28 bit, BW 200 kHz) and 1 fast output (16 bit, BW 10 MHz)

Sensor types

Nanosurf offers both original qPlus Sensors as invented by Prof. Franz Giessibl, as well as the Nanosurf-developed EV (enhanced visibility) types that allow for better optical access to the tip. The rigid prong design allows easy mounting of the tip material of your choice.

Type Resonance frequency (kHz)  Spring constant (kN/m)
S1.0 32.8 1.8
S0.8 52.6 3.6
M5B 105 4.4
ev_V1 39.5 1.1
ev_V5 95.3 4.4

Areas of application and application examples

ARAC is an instrument with promising potential in various areas of research. Currently ARAC is in use in the labs of the first pioneers to gain new insights in the following areas:

  • Graphene and 2D materials
  • Growth and quality of layers
  • Defect density
  • Analysis of surface coatings

The below measurement images show the potential of this innovative approach to material analysis

Topography of KBr crystal (sapphire tip)
Topography of KBr crystal (sapphire tip)
Quasi-constant height image of muscovite mica
Quasi-constant height image of muscovite mica. The slow parameters of the Z-controller correct for drift effects, while the image appears in the shift of the qPlus resonance (sapphire tip)
Scanning tunnelling image of HOPG (PtIr tip). A qPlus sensor with conductive tip allows for simultaneous AFM/STM operation.
Scanning tunnelling image of HOPG (PtIr tip). A qPlus sensor with conductive tip allows for simultaneous AFM/STM operation

Further reading

  1. The qPlus sensor, a powerful core for the atomic force microscope, Review of Scientific Instruments, Volume 90, 011101 (2019)
  2. Characterization of hydrogen plasma defined graphene edges, Carbon, Volume 150, September 2019, Pages 417-424
  3. Imaging in Biologically-Relevant Environments with AFM Using Stiff qPlus Sensors, Scientific Reports, Volume 8, Article number: 9330 (2018)

Interested in becoming an ARAC pioneer yourself? Contact us now to be among the first researchers to obtain access to this unique instrument.