Cathodoluminescence (CL)

About this technique

Cathodoluminescence (CL) is the non-incandescent emission of light (photons) from a luminescent material excited by an electron beam. CL photons (from ultraviolet, through visible to the near-infrared) are emitted as result of electronic transitions between the conduction and valence band and may also involve electronic transitions associated with defect levels within the band gap. The optical, electrical and mechanical properties of solids are dependent on the presence of microscopic defects (imperfections and impurities) and therefore CL microanalysis is a useful spectroscopy and imaging technique for characterising these properties with high sensitivity and spatial resolution.

Cathodoluminescence microanalysis in a scanning electron microscope (SEM) enables high-sensitivity detection of defect centers in a wide range of materials. CL image resolution can range from tens of nanometres to micrometres and is dependent on specimen configuration and interaction volume, carrier diffusion and electron beam parameters, etc. Quantitative CL microanalysis of defect and impurity concentrations is not generally achievable because of the lack of a general explanation for the complex nature of competitive recombination processes.

The preparation of a specimen for CL microanalysis in an SEM is similar to preparation for other SEM-based microanalytical techniques. Many luminescent specimens also need coating with a thin conductive film to minimise surface charging effects.


Output examples

Composite colour cathodoluminescence image of porous GaN on sapphire produced by electrochemical etching. The field of view is 25 μm across.

Contact an expert

The University of Western Australia
Dr Malcolm Roberts
T: 08 6488 2770

James Cook University
Dr Kevin Blake
T: 07 4781 4864

Curtin University
Dr Zakaria Quadir
T: 08 9266 1026

SARF – The University of Adelaide
Mr Angus Netting
T: 08 8303 3134

University of Wollongong
Dr David Mitchell
T: 02 4221 5312

University of Wollongong
Dr Mitchell Nancarrow
T: 02 4221 3272

University of Tasmania
Dr Karsten Goemann
T: 03 6226 2146