Chronos

Picosecond time-resolved cathodoluminescence microscope

The Chronos is a variable temperature time-resolved nanometer resolution spectroscopy instrument that builds on the Allalin quantitative CL system. In continuous operation mode, the Chronos works like the Allalin system using the same high current density Schottky field emission gun.

In time-resolved mode, the same gun is driven by an ultrafast laser to create short electron pulses. Attolight’s highly efficient quantitative CL collection system is a crucial component of the Chronos since excitation currents in pulsed mode are up to thousand times less intense than in continuous mode.

Careful synchronization of the excitation laser and the detectors makes time-resolved CL in the picosecond regime a reality. Switching between pulsed and continuous mode is automated and takes a couple of minutes, which makes the system a perfect fit for a multiuser facility where users have multiple demands and throughput is important.

The Chronos is built for researchers who need to access dynamic spectroscopic information with nanometer spatial and picosecond temporal resolutions.

The Chronos features a comprehensive set of ultrafast detectors to cover the UV to IR wavelength range and to optimize performance for your applications. The Chronos’ versatile design also makes it capable of performing advanced methods such as pump/probe spectroscopy and dynamic SEM.

Key benefits


  • Automated switching between continuous and time-resolved mode within minutes
  • No degradation of spatial resolution when switching from continuous to pulsed mode
  • Same dedicated graphical user interface and control software as the Allalin, featuring time-resolved detectors
  • Extension to include advanced characterization techniques such as pump / probe spectroscopies or dynamic SEM
  • Large choice of detectors and detector technologies to cover the wavelength range from 200nm (UV) to 1700nm (IR)
  • Scripting functionality to automate measurements and configure the system for specific needs
  • Highest collection efficiency CL system adapted to low excitations currents in pulsed mode
  • Ultrastable helium cryostat system to work at temperatures from 10K to room temperature
  • Refer to the Allalin product description for additional benefits

System Configurations

Schematic setup of a Chronos system showing the main components.

The streak camera is the fastest and most convenient detector for time-resolved CL measurements: it is a highly parallel detector that registers the decay time of a full spectrum. This enables the measurement of time-resolved hyperspectral data. The streak camera has an instrument resolution of up to 2ps and its detection frequency is directly synchronized to the laser repetition rate. System time-resolutions below 20ps are easily achieved in everyday operation by using a streak camera.

TCSPC is a fast single-channel time-resolved detection method that can be used with a multitude of different single channel detectors. The TCSPC electronics measures the time difference between a signal on the detector and the exciting electron (laser) pulse and creates a histogram over time that corresponds to the signal evolution over time.
Depending on the application, Attolight recommends a specific set of detectors and detection methods. Here is a brief description of the most used detectors for TCSPC.

A PMT based TCSPC system can be very efficient solution in the UV – NIR wavelength range when time-resolutions around 200ps are acceptable.

APD based TCSPC systems are an excellent choice for detection in the NIR to IR wavelength range. Time-resolutions as good as 100ps can be achieved with these systems.

SSPD detectors are extremely fast and sensitive over a broad wavelength range. Time resolutions below 100ps can be achieved with these systems.

The infinity corrected light collection system can also be used to inject an excitation source. The electron beam triggered by photons and the laser operate at the same frequency, the optical delay line allows for precise tuning of the delay between the pump and probe pulse. The laser spot can be focused to under 10µm on the sample surface.

Attolight can add up to two spectrometers per CL system, this allows for a total of four detectors connected to the CL setup. Switching between the detectors is computer controlled and does not need any hardware re-configuration.
Please refer to the Allalin system for further system configurations and options.

Specifications

The Chronos is based on the Allalin system. We outline the Chronos specific specifications here. Please refer to the Allalin brochure for additional specifications.

  • Automated switching from continuous to pulsed electron emission mode
  • Electron spotsize in pulsed mode < 10nm from 3keV to 10keV
  • Maximum photoelectric current from > 10pA
  • Photocathode sensitivity over the range of 200nm – 850nm
  • Highest temporal resolution of 2ps
  • Peak quantum efficiency over 20% around 500nm
  • over 1000
  • Electron spotsize in pulsed mode < 10nm from 3keV to 10keV
  • Maximum photoelectric current from > 10pA
  • electronics with 20ps FMWH time resolution
  • 4 input channels for up to four detectors
  • 1 GHz counters
  • High precision discriminator

System layout

Layout example with Helium Dewar for low temperature operation and operator desk.