11-0037-22_1300983942 NSI FESEM minimum requirements current.pdf

Naval Research Lab FESEM Requirements

• The Field Emission Scanning Electron Microscope (FESEM or SEM) with a crossover free technology design for high resolution and greatest flexibility in analysis. It will be configured with a Schottky emitter. The FESEM must be controlled by one 64- bit computer system using Microsoft Windows 10 LTSC2019 as an operation system with a flexible and easy to use graphical user interface. The beam path of the SEM must be designed to be cross-over free to minimize the statistical Coulomb interactions (“Boersch effect”) between beam electrons. A beam booster must be an integral part of the electron optical column to maintain a high energy throughout the entire column. This is to ensure that the beam is extremely well protected against stray fields, even when the SEM is operated at very low voltages. No hybrid electron optic designs will be acceptable.

• The objective lens design of the FESEM will produce a reduced magnetic field at the specimen surface. Sub 4 nm resolution imaging of dia-, para-, or ferromagnetic samples is possible even at working distances (WD) below 2 mm and low accelerating voltages (AV). • High resolution imaging of ferromagnetic steel @ WD = 3 mm; AV = 1 kV @ 100.000x Mag is required

• The FESEM will have a probe current range of at least a minimum value of 4 pico amps to a maximum 20 nano amps.

• The FESEM will incorporate a pneumatic scanning transmission electron microscopy (STEM) detector of diode design consisting of a central segment (BF) and 4 additional segments for dark field (DF) detection with the following modes: Normal dark field (DF), Oriented dark field (ODF), Annular dark field (ADF) and High angle annular dark field (HAADF). The STEM detector will allow for parallel read-out of up to 4 virtual STEM modes. The STEM detector will accommodate 3mm grids.

• The FESEM must provide the capability to select backscattered electrons according to energy within its in-column detection system. Parallel in-column detection of secondary electrons and backscattered electrons is required. The in-lens detectors for both the secondary and backscattered detectors must be on-axis and perpendicular to the final crossover on the sample at zero degrees tilt. This requirement is to ensure the highest collection efficiency.

• The FESEM will provide highest flexibility to enable both high resolution work and flexibility to image a wide range of different sample materials including insulating materials, which requires variable pressure imaging, and magnetic or magnetizable materials. The SEM will have a resolution as follows:

0.4 nm at 30 kV (STEM)

0.5 nm at 15 kV

0.8 nm at 1 kV

1.0 nm at 0.5 kV In lens BSD Detector resolution:

1.0 nm at 1 kV

All the above requirements are in High Vacuum Mode. This resolution must be achieved without sample bias in order to enable high resolution imaging of samples or sample geometries, which cannot be used together with sample biasing. Also imaging at beam energies down to 20 V without sample biasing shall be required.

• The FESEM will have the ability to have vacuum range from 10 to 500 Pa, adjustable in steps of 1 Pa.

The variable pressure mode will allow the in-lens secondary electron (SE) and back scatter electron (BSE) detectors to be used when in operation as well as the lower lens detectors. The resolution achieved will be at least 1.4 nm at chamber pressure of 30 Pa and 3 kV and 1.0 nm at chamber pressure of 30 Pa and 15 kV

• The Energy-dispersive X-ray spectroscopy (EDS) analytical working distance must be at least 9mm or shorter and be adjustable to 20 mm.

• The FESEM must be configured with Variable Pressure operation and have the capability to use the In-column SE and In-column BSE detectors during variable pressure operation.

• The vacuum design for simplicity will be designed for variable pressure operation using one dry scroll pump, one turbo molecular drag pump and two ion pumps.

• The chamber must provide at least 12 ports. Three of them for analytic (EDX, Wavelength-dispersive X-ray spectroscopy (WDX)), the nine other for e.g. BS-, cathodoluminescent (CL) detector, air lock, or Electron backscatter diffraction (EBSD). An EDX port must be configured above the EBSD port and orthogonal to the tilt-axis

• The SEM must provide a pneumatic local charge compensation needle as an option that will enable both the chamber in-lens SE and in-lens ESB for highly charging-non-conductive materials.

• The SEM must have a high precision fully motorized stage allowing movements of at least X = 125 mm, Y = 125 mm, Z = 50 mm, T = -4º to 70º, and R = 360º. 2. The SEM will be able to load specimen up to 179 mm in diameter and will be able to move the sample to full X and Y travel range provided and have a weight capacity of at least 2 kilograms.

• The FESEM scanning system must provide a 16Bit scan precision and large image store up to at least 30k x 20k for storing of larger images.

• The Magnification range should be from 8x to 2.000.000x for SE imaging and BSE imaging

• Live simultaneous mixing of different signals must be possible at any ratio. Parallel in-lens EsB and in-lens SE detection as well as parallel in-lens SE and chamber SE detection using the Everhart-Thornley detector is required at all magnifications and accelerating voltages