DuoScan™ Macro and Sub-Micron Raman Mapping

The innovative DuoScan™ Imaging system extends the imaging capabilities of HORIBA Scientific’s Raman instruments from sub-micron to macro-scale mapping. Generating confocal images becomes faster, easier and more flexible, from the deep UV to the IR.

The DuoScan™ Imaging technology available on the instruments of the LabRAM Series introduces a new imaging mode, based on a combination of scanning mirrors that scan the laser beam across a pattern chosen by the operator: a line for linear profiles, or an area for two-dimensional mapping.  It can be used to generate a rastored "macro laser spot" for large area mapping; alternatively, its 50 nm step piezo controllers are ideally suited for Raman mapping of sub-micron features.

How DuoScan works – the three modes

1. Averaging mode

In averaging mode the laser spot is continuously scanned across a user-defined square surface

Comparison between standard point measurement and DuoScan^TM averaging mode with corresponding laser spot size and power densities on sample

2. Step-by-Step mode

In step-by-step mode a sample area is selected and the sample is scanned point by point across the chosen area.

Mapping without moving the sample with 50 nm step size

3. Macro-mapping mode

Macro-mapping mode enables large sample surfaces to be raster-scanned to record an average spectrum across the whole surface, ideal for component distribution or to locate contaminents.

Macro-mapping with full sample coverage using DuoScan^TM with motorized stage

DuoScan™ Application Examples

Example 1 – Pharmaceutical Tablet

In this example a 12.5 mm by 12.5 mm pharmaceutical tablet is analysed using a DuoScan™ macro-pixel for fast large area mapping – this ensures that the entire surface area of the tablet is analysed, without ‘stepping over’ any small features.  Subsequently high resolution point-by-point mapping using the DuoScan™ piezo controlled mirrors allows a detailed image of microscopic features to be visualised.

Example 2 – Carbon Nanotubes

Isolated SWCNTs aligned on a Silicon sample. The colors correspond to the integrated intensity of the Si band (red) and of the respective G bands of the CNTs (green and blue).

DuoScan™ was used in macro-mapping mode to find the isolated CNTs. A high-definition image of the CNT was then obtained with DuoScan™ in step-by-step micro-mapping mode. The apparent width of the CNT is a convolution of the tube diameter with the laser spot size.

Sample courtesy of Dr Kalbac, Heyrovský Institute, Prague, Czech Republic

Other applications

• Large area component mapping (contaminant screening, survey scans, etc.)

• Chemical imaging at sub-micron scale

• Raman analysis and imaging of photosensitive biological samples

• Mapping on large and heavy samples that cannot be moved easily

• Prevention of photodegradation of organic materials when working with UV excitation