** MAIN FEATURES **
This environmental scanning electron microscope (ESEM), acquired in 2007, has been primarily used for the characterization of cementitious materials (clinkers, cements, concretes).
Its main application has been under high vacuum conditions, on samples embedded in resin, then polished and carbon-coated, for BSE (Backscattered Electron) imaging and EDS (Energy Dispersive Spectroscopy) analysis.
** BEAM **
– Emitter Type: Schottky Field Emission Gun (FEG)
– Acceleration Voltage Range: 200 V to 30 kV (continuously adjustable)
** RESOLUTION **
– HV mode (SE)=1.2nm (30kV) – 3nm (1kV)
– LV mode (SE)=1.5nm (30kV) – 3nm (3kV)
– Extended mode (ESEM) = 1.5nm (30kV)
The ESEM mode is designed for non-conductive and hydrated samples, where the gas environment helps neutralize charge, enabling imaging without coating, but can slightly impact the ultimate resolution compared to optimal high vacuum conditions.
** DETECTORS **
ETD (Everhart-Thornley Detector): This is the standard detector for High Vacuum SEM, primarily collecting Secondary Electrons (SE). It provides excellent topographic information (surface details) by attracting low-energy electrons emitted from the sample.
CBS (Concentric Backscatter Detector): A solid-state detector, usually annular, that primarily collects Backscattered Electrons (BSE). It provides strong compositional contrast (showing differences in atomic number) and can also offer some topographic information.
LFD (Large Field Detector): Designed for Low Vacuum (LoVac) and Environmental SEM (ESEM) modes, this detector collects Secondary Electrons (SE) by utilizing the gas in the chamber for signal amplification. It’s essential for imaging non-conductive and hydrated samples without coating, providing topographic details.
GAD (Gaseous Analytical Detector): An advanced detector for Low Vacuum (LoVac) and ESEM that efficiently collects both Backscattered Electrons (BSE) for compositional contrast and often Secondary Electrons (SE) via gas amplification. It’s designed to optimize signal quality for both imaging and elemental analysis (like EDS) in gaseous environments.
** STAGE **
– X & Y Travel: Typically 50 mm x 50 mm.
– Z Travel: 25 mm motorized range (50 mm total).
– Tilt (T): Approximately -15° to +75°.
– Rotation (R): 360° continuous.
** ACCESSORIES **
– No extra accessories
** CONDITION **
– The microscope sees limited use, and Thermo Fisher Scientific has performed a full maintenance service annually.
– The FEG (Field Emission Gun) tip was last replaced in December 2022.
