chronos - cathodoluminescence€¦ · overview the chronos is a variable temperature time-resolved...

OverviewThe 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 multi-user facility where users have multiple demands and throughput is important.

ChronosPicosecond time-resolved cathodoluminescence system

Be Part of the New Cathodoluminescence Revolution

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 200 nm (UV) to 1700 nm (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 10 K to room temperature

– Refer to the Allalin product description for additional benefits

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.

SEM maps on gold nanoparticles. Same zone comparison in pulsed (left) and continuous (right) mode. The signal to noise ratio decreases with pulsed excitation due to lower current, image resolution is better than 10 nm.

Pulsed 3 keV 3 keVCW

Attolight AG © 2018. We are constantly improving the performance of our products, so all specifications are subject to change without notice.

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Time-resolved CL analysis of diffusion of excitons in a strained ZnO micro belt : time resolved spectra from 3 different excitation zones along the diameter of the belt. These measurements allowed to set up and verify a strain induced diffusion model (ACS Nano, 8(4), 3412-3420, 2014).

Applications and examples

– Measurement of local radiative and non-radiative carrier lifetimes

– Excited carrier dynamics in semiconductor heterostructures

– Advanced pump / probe spectroscopy

Local carrier recombination in m-plane InGaN/GaN quantum wells (Applied Physics Letters 109, 232103 (2016)).

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CL intensity an effective lifetime change around a single dislocation on a GaN sample (Applied Physics Letters 109, 042101 (2016)).

Time-resolved CL decays and CL maps of single InGaN/GaN core-shell microrods (Applied Physics Letters 112, 052106 (2018)).

Other applicationsPlease refer to the publication list on our website for more applications and in-depth analysis of CL measurement.


System Configurations

Schematic setup of a Chronos system showing the main components.

Streak Camera: multichannel time-resolved detector in the 200 nm (UV) to 850 nm (NIR) rangeThe 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 2 ps and its detection frequency is directly synchronized to the laser repetition rate. System time-resolutions below 20 ps are easily achieved in every-day operation by using a streak camera.

Time-correlated single photon counting (TCSPC) in the 200 nm (UV) to 1700 nm (IR) wavelength rangeTCSPC is a fast single-channel time-resolved detection method that can be used with a multitude of different sin-gle 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.

Photomultiplier (PMT) in the 200 nm (UV) to 850 nm (NIR) wavelength rangeA PMT based TCSPC system can be very efficient solution in the UV–NIR wavelength range when time-resolutions around 200 ps are acceptable.

Avalanche Photodiode (APD) in the 900 nm (NIR) to 1700 nm (IR) wavelength rangeAPD based TCSPC systems are an excellent choice for detec-tion in the NIR to IR wavelength range. Time-resolutions as good as 100 ps can be achieved with these systems.

Super conducting single photon detectors (SSPD) in the 400 nm (UV) to 17 00nm (IR) wavelength rangeSSPD detectors are extremely fast and sensitive over a broad wavelength range. Time resolutions below 100 ps can be achieved with these systems.

Pump / probe spectroscopy (fig. 1)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 con-trolled and does not need any hardware re-configuration.The infinity corrected light collection system can also be used to inject an excitation source. The electron beam trig-gered 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 10 µm on the sample surface.

Other configurationsPlease refer to the Allalin system for further system configurations and options.


Schottky FEG, CW and pulsed emission

Gun lens

SE detector

Free space optical coupling

CCD cameraStreak camera

Syncronisation

Laser, > 10 ps, 80 MHzA Condenser lens

and integrated light collection

A

B Cryogenic nanopositioning stage 10 K–300 K

B

Imaging spectrometer

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.

Electron Optics – Automated switching from continuous to pulsed

electron emission mode– Electron spotsize in pulsed mode < 10 nm from

3 keV to 10 keV– Maximum photoelectric current from > 10 pA

Streak camera– Photocathode sensitivity over the range of 200 nm–

850 nm– Highest temporal resolution of 2 ps– Peak quantum efficiency over 20 % around 500 nm– Over 1000

– Electron spotsize in pulsed mode < 10 nm from 3 keV to 10 keV

– Maximum photoelectric current from > 10 pA

TCSPC electronics– Electronics with 20 ps FMWH time resolution– 4 input channels for up to four detectors– 1 GHz counters– High precision discriminator

System lay-out– Footprint : (length) 1437 mm × 1039 mm (width)– Recommended service area :

(length) 2236 mm × 2426 mm (width)– Tool weight : ~1170 kg

Attolight AG / EPFL Innovation Park / Building D / 1015 Lausanne / Switzerlandt +41 21 626 0100 / [email protected] / www.attolight.com

Fig. 1. Pump / probe spectroscopy


Schottky FEG, CW and pulsed emission

Gun lens

Optical filter and

beam expander

Free space optical coupling

CCD cameraStreak cameraSyncronisation

Optical delay line

Laser, 150 fs,

80 MHz, 355 nmA Condenser lens

and integrated light collection

A

B Cryogenic nanopositioning stage 10 K–300 K

B

Imaging spectrometer

chronos - cathodoluminescence€¦ · overview the chronos is a variable temperature time-resolved...

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