# OVERVIEW

BACK

The IR1 beamline is an endstation dedicated to infrared nanospectroscopy (nano-FTIR) in the range of mid-IR. Its main purpose is the analysis of chemical-optical properties of condensed matter in the nanoscale. In similar fashion to established infrared spectroscopy (FTIR), the nano-FTIR allows for identification and characterization of a chemical compound by means of its vibrational response, however, with nanoscale spatial resolution. Moreover, nano-FTIR is a technique based on near-field optics and, therefore, can be applied to the optical analysis in the sub-diffractional regime of plasmonic and photonic materials.

To overcome the diffraction limit of light, this experimental endstation uses the broadband synchrotron IR beam extracted from the LNLS storage ring as the light source for the experiment Scattering Near-Field Optical Microscopy (s-SNOM). In this experiment a metal coated atomic force microscopy (AFM) tip acts as an antenna for the light confinement at the its apex, creating a new source that no longer depends on the incident light wavelength but it is defined by the shape of the AFM probe, allowing for a spatial resolution of c.a. 25 nm.

The specifications of IR1 beamline of LNLS allows for multidisciplinary studies in Physics, Chemistry and Biology, in particular those studies in which the local chemical information is the central point in the research.

Potential applications are: Opto-electronics and vibrational properties of 2D materials, chemical analysis of sub-micron molecular domains in polymer blends, nano-drugs delivery, single cell chemistry, vibrational analysis of archeological micro-artefacts, new nanostructured materials for energy harvesting and conversion.

## CONTACT

Beamline Email: N/A

Beamline Telephone Number: +55 19 3517 5157

Coordinator: Raul Freitas

Coordinator Email: raul.freitas@lnls.br

Coordinator Telephone Number: +55 19 3715 5060

For more information on the Beamline Team, check out the Beamline Team’s page here

# OPTICAL ELEMENTS

ElementTypePosition[m]Description
SOURCEBending Magnet0.0Bending Magnet D03 exit A (4°), 1.67 T, 30 mrad x 80 mrad
M1Plane, 6 mm slot2.5Gold coated, aluminum substrate
M2Tangential cone-shaped3.1Gold coated, aluminum substrate
M3Tangential cylinder3.7Gold coated, aluminum substrate
CVDDiamond window7.020 mm diameter by 500 $\mu \rm m$ diamond window by Chemical Vapor Deposition
M4Tangential cylinder7.5Gold coated, aluminum substrate
M5Tangential cylinder7.9Gold coated, aluminum substrate

# PARAMETERS

ParameterValueObs. | Condition
Energy range [ $\rm cm^{-1}$ ]3000 - 700Broadband radiation limited by beamsplitter transmission and detector sensitivity
Energy resolution [ $\rm cm^{-1}$ ]Up to 3.3Limitted by the interferometer travel
Beam size at sample [nm, FWHM]< 40 nmNear-field spot defined by the size of the s-SNOM tip
Flux at first optical element [Phot/s/0.1%bw]$2.0 \times 10^{13}$at 1000 $\rm cm^{-1}$ (10 $\mu \rm m$)
AFM scanning stage (maximum travel) [ $\mu \rm m$ ]$\pm$45-
AFM scanning stage minimum step [nm]5-

# INSTRUMENTATION

InstrumentTypeModelSpecificationsManufacturer
s-SNOMNear-field Optical MicroscopeNeaSnom-NeaSpec
MCT DetectorSingle element Mercury-Cadmium-Telluride (MCT) KLD-0.1-J1208L750 $\rm cm^{-1}$ to 3000 $\rm cm^{-1}$, 100 $\mu \rm m$ element size, DC to 1 MHz BW, $\rm LN_{2}$ cooledKolmar Technologies
MCT DetectorSingle element MCTIRA-20-00103650 $\rm cm^{-1}$ to 3000 $\rm cm^{-1}$, 50 $\mu \rm m$ element size, 500 Hz to 2 MHz BW, $\rm LN_{2}$ cooledInfrared Associates Inc.
Si DetectorSingle element Silicon detectorPDA36A-EC350 nm to 1100 nm, 3.6 mm x 3.6 mm element size, DC to 10 MHz BW , air cooledThorlabs
InGaAs Detector Single element Indium-Gallium-Arsenide (InGaAs) detector PDA10D-EC PDA10D-EC Thorlabs
Lock-in amplifier2 input channels digital lock-in amplifierHF2LIDC to 50 MHz, 210 MSa/s, USB 2.0 high-speed, 480 Mbit/sZurich Instruments
Visible laserHeNe laserHNL150L15 mW HeNe (633 nm) laserThorlabs

# CONTROL AND DATA ACQUISITION

Data acquisition is performed directly in the native software of the NeaSnom microscope developed by Neaspec. S-SNOM image files are compatible with the free program Gwyddion (http://gwyddion.net) and point spectra, linescans and spectral images are postprocessed using Mathematica® routines developed by the IR1 team.

# APPLYING FOR BEAMTIME

Submission calls are usually announced twice per year, one for each semester. All the academic research proposals must be submitted electronically through the SAU Online portal. Learn more about how to submit a proposal here.

# PRE-CHARACTERIZATION AND SAMPLES REQUIREMENTS

In nano-FTIR just a small portion of the material (few thousands of molecules!) are involved in the scattering intensity that reaches the IR detector. In addition, the scattering power of s-SNOM is proportional to the polarizability of the material that is classified as STRONG for metals, MODERATE for semiconductors and polar minerals and WEAK for most of organics. Therefore, point spectra of nano-FTIR (25 nm by 25 nm areas) need at least 20 minutes, depending on the polarization strength of the material, and then it is a quite time-consuming technique which does not allow for pre-characterization. In this sense, samples to be measured in the IR1 must be previously characterized in the following aspects:

• Prediction for the vibrational modes to be monitored during the experiments. Conventional FTIR can offer a precise average overview of the vibrational response of the material. For the systems not accessible to FTIR, it is recommended for the user to provide a list of potential vibrational resonances of the material based on literature or other references.

• The sample surface should be AFM compatible. Hence, AFM images done prior to the beamtime are strongly recommended. The most successful experiments at this endstaion were done on surfaces with roughness bellow 30 nm.

For sample preparation, it is recommended the sample slices or films to have thickness between 50 nm and 150 nm. They should be deposited/transferred on a metal coated (e.g. Au) flat substrate (e.g. Si or Glass). The metal coating should not be thinner than 100 nm in order to avoid extra vibrational contributions from the substrate. In case the user is not able to prepare the metal coated substrates, please contact the beamline staff and we can provide few substrates. Recommended dimensions for the substrate are 10 mm (depth) x 10 mm (width) x 0.5 mm (thickness). In case of larger substrates, please contact the beamline staff for more discussing the feasibility.