Time-resolved imaging

Measure time dynamics with time-resolved cathodoluminescence

Understand the time dynamics associated with cathodoluminescence through time-resolved imaging. 

Download technical note
What we can help you to achieve
  • Perform lifetime imaging and g(2) imaging

  • Get insights into intrinsic material properties, nanoscale quality and defects
  • Study the quantum nature of light and single-photon emitters
  • Pump-probe cathodoluminescence imaging
MediaWDescr_Data g2

Lifetime mapping and cathodoluminescence g(2) imaging

Light emission from a material is a complex dynamic process in which many different mechanisms can play an important role. By studying these dynamics one can therefore obtain detailed insight into a large variety of physical processes and material properties. Time-resolved cathodoluminescence is a powerful technique, which is used for understanding time dynamics associated with light. Two types of imaging can be performed:  lifetime mapping (or emission decay) and g(2) imaging, which is also known in physics as the second-order correlation function. The lifetime is determined by how the light emission process occurs after the material is excited by the electron beam. CL decay-trace measurements are very useful for semiconductor materials used for optoelectronic devices.  

Another approach is using the g(2) function. The g(2) function, well-known from quantum optics, provides a very useful tool in this context. g(2) imaging can be used to identify and characterize single-photon emitters at the nanoscale. As such, it can be employed in the context of fundamental studies on quantum systems and their interaction with electron beams. Furthermore, it can be used to study bunching in extended systems with multiple emission centers which can be connected to the emission lifetime and excitation efficiency. One of the main benefits of this approach is that it can be performed with a continuous electron beam so no adaptations to the electron microscope are required. This approach is valuable for studies on dielectrics and semiconductor systems to name a few.

How can you perform time-resolved CL?

Time-resolved cathodoluminescence imaging observes exponential probability distribution for light decay at a particular time delay. This is possible to achieve by using electrostatic or laser triggered pulsed electron microscopy, which are the most common practices.

LAB Cube is an additional SPARC module for decay trace imaging using time-correlated single-photon counting. Filters inside of the LAB Cube allow measuring intensity or/and colour, while a single-photon detector  detects photons and sends the signal to time correlation electronics. By averaging over many electron pulses a histrogram is built up with enough statistics to observe the exponential decay and extract the lifetime. 

Another configuration of the LAB Cube consists of two single-photon detectors, which allows observing how photons are distributed in time. With g(2) imaging three characteristic behaviours can be observed: coherent (for a coherent source, such as laser), antibunching (for quantum emitter, such as single molecule or quantum dot), and bunching (for incoherent emitters). Additionally, with g(2) function it is possible to measure the lifetime and the excitation probability. 

A third approach is to perform pump-probe spectroscopy in which ultrafast electron pulses are overlapped with ultrafast laser pulses on a sample to extract dynamic information. Delmic offers solutions for pump-probe spectroscopy as well so enquire with the Delmic team about the possibilities

 

2021_CL_Time-Resolved Blend_A 2021_CL_Time-Resolved Blend_B
Decay-trace histograms acquired on an InGaN quantum well LED stack with (a) aλ < 500 nm short pass filter selecting the InGaN quantum well emission and (b) a λ =510 – 590 nm bandpass filter selecting the yellow band emission from the n-doped GaNlayer. The yellow band has a longer lifetime and clearly shows multiexponential decay characteristics. Imagescourtesy of Dr. SophieMeuret (AMOLF,Amsterdam) [8]

Use the right products to get the right results

Delmic CL solutions offers a range of powerful and user-friendly cathodoluminescence detectors, which can help you learn more about both bulk and nanostructured materials.

Talk to our expert

Talk to an expert

Get in touch with one of our experts to get more information.
Call +31 (0)15 744 01 58 or book a meeting in their agenda.

Book a meeting
Delmic sales expert Daan van Oosten Slingeland