Light Collection / Injection for STEM (CL STEM Add-On)

Overview

The Mönch add-on is a unique tool that can operate in either a light collection or light injection mode, thanks to its specific mirror design. In addition, the flexibility of the add-on allows an external coupling either in free space or via an optical fiber.

In light collection mode, the Mönch add-on has been designed to achieve an unprecedented signal-to-noise ratio thanks to:

• A proprietary collection mirror with a curvature radius that fits in a small pole piece gap (down to 5mm) and a precise sub-micrometer alignment for a perfect adjustment of the mirror with respect to the sample.
• A working distance reduced to 300µm to optimize light collection efficiency
• A patented asymmetric optical fiber designed to preserve brightness and spectral resolution.

In light injection mode, an unprecedented level of performance is reached thanks to:

• A beam size reduced to few microns for localized excitation of your samples. Light injection can be operated to locally heat specific areas of the sample surface.
• The ability to perform injection and light collection measurements simultaneously.

Mode	Excitation source	Analysis (detection)
Light collection Light collection after surface excitation	E-beam, Laser, Thermal, Electrical…	Cathodoluminence (light)
Light injection Electron imaging after light/thermal excitation	Laser, other sources of light	Electron imaging (electron) in photo emission/thermo-ionic regimes
Light injection + collection Light emission after light/thermal excitation	Laser, other sources of light	Photoluminesence (light)

 

Features

The Mönch is an add-on system connected to a TEM. A retractable arm holds a proprietary reflective mirror to collect or inject light on the sample. 

Mirror independent from sample holder

• Flexibility, ease of alignment vs. e-beam and sample
• Free sample displacement (enables to scan a large sample surface)
• High curvature parabolic mirror (NA>0,4)

Motorized arm (X travel 30mm)

• Fine alignment (precision better than 100nm)
• Full retractation arm to enable EDX, EELS, 4D-STEM… analyses

Low mirror-sample distance

• Maximize light collection/injection
• Spot size down to 2µm-diameter

High mirror reflection

• Up to 90% from 200nm to nIR.
• Various mirror coatings available (ex: Gold coating for l>1.7µm)

Optimized module

• User-proof actuation system with absolute encoders (position recovered after power cut-off without need for calibration)
• Stage touch alarm
• Compatible with 120°C system vacuum bakeout
• Compatible optical fiber or free space (switch takes few seconds)

Collection mode

• Free space or through a fiber

Patented asymmetric fiber

• Fibers arrangement parallel to the entrance slit of the imaging spectrograph
• Brightness and spectral resolution are preserved

 

Applications

• Study of advanced materials, such as:
  • Nitrides (GaN, InGaN, AlGaN, …);
  • III-V (GaP, InP, GaAs, …);
  • II-VI (CdTe, ZnO, …)
• Wide band-gap materials (diamond, AlN, BN)
• Compositional inhomogeneities in compound materials (e.g. Indium clustering in InGaN)
• Confined structures or heterostructures morphology to their optical properties
• Defects (vacancies, threading dislocations, stacking defaults, …)
• Plasmonics …