A Novel Technique to Probe Optical Absorption of 2D Materials by Cathodoluminescence

Nano Letters  has recently reported a novel technique to map the optical absorption of two-dimensional materials. It is a non-contact and non-destructive technique named Quantitative Nanoscale Absorption Mapping (QNAM). The inventors of QNAM come from EPFL (Lausanne, Switzerland), IMEM (Parma, Italy), the U.S. Army (New Jersey, USA) and the Instituto Nanoscienze (Pisa, Italy).

How does it work?

The original approach of QNAM is to probe the absorption properties of a 2D material using the CL emission of the underlying substrate as the light source.

Sketch of the working principle of QNAM

A bulk substrate topped with a two-dimensional layer is excited by an electron beam. As a result, the substrate emits light, via a cathodoluminescence process, that is partially absorbed by the 2D material.

What does it bring?

In their report, the authors first noticed an enhancement of the absorption in the UV range due to interlayer excitonic phenomena. Then, they extended the QNAM technique to measure the optical absorption of MoS2/MoSe2 van der Waals heterostructures. Finally, they used it to detect defects such as grain boundaries and ad-layers.

(a, b, c) MoS2 ML on sapphire substrate (d, e, f) MoSe2 flake on Al2O3. (a, d) Secondary electron image. (b, e) QNAM map. (c, f) CL spectra.

To find out more on the QNAM technique

Quantitative Nanoscale Absorption Mapping: A Novel Technique To Probe Optical Absorption of Two-Dimensional Materials, M.Negri, L.Francaviglia, D.Dumcenco, M.Bosi, D.Kaplan, V.Swaminathan, G.Salviati, A.Kis, F.Fabbri, A.Fontcuberta i Morral, Nano Lett. 2020, 20, 1, 567-576

Cambridge University - Grand Opening

On September 12th, 2019, the Department of Materials Science & Metallurgy of Cambridge University held a Grand Opening Ceremony for their brand-new Allalin Chronos tool.

Prof Rachel Oliver and her team gathered more than 50 researchers from the UK scientific and industrial community, to officially introduce this new tool, funded through an Engineering and Physical Sciences Research Council (EPSRC) grant.

The day started with the official opening ceremony by Prof Lindsay Greer (Head of the School of Physical Sciences), then went on with many talks about the first Cathodoluminescence results obtained on the tool. The results encompassed materials ranging from compound semiconductor materials and devices to perovskite and geological samples, hinting at promising publications to come.
Prof Rachel Oliver followed with the practicalities of access to the tool, which is a shared facility for the UK scientific community.

Attolight warmly thanks Prof Rachel Oliver and her team for their hospitality and the organisation of this great event !


Focus on CL in the Compound Semiconductor Magazine!

With the launch of the Säntis 300 by Attolight, Cathodoluminescence is going to revolutionize the quality control of semi-conductor devices by enabling a quick and non-invasive way to determining alloy compositions, exposing and buried defects and uncovering surface contamination.

Find out the full article about ‘Quantitative cathodoluminescence streamlines chip production’, published in the last issue of Compound Semiconductor Magazine of June 2019.