product field
product field2
contact field
contact field2
pdf download link

EM-Tec B100 Faraday cup for beam current measurements
# 36-000800

EM-Tec B100 Faraday cup

Introduction
Precise beam current measurements are needed to check the stability of the electron or ion beam over longer periods of time or to adjust to a specific beam current. This might be needed for:

  • quantitative X-ray micro-analysis when using references standards
  • uniform and reproducible X-ray mappings and line scan
  • electron beam lithography
  • comparative measurements
  • adjusting ion beam milling rates.

Measuring the beam current at the point where the beam hits the sample surface gives the most accurate results. A Faraday cup is a useful tool for precise measurements of the electron or ion beam. It consists of an enclosed cavity with a small opening through which the beam can be directed.
Sometimes beam measurements are made on graphite (carbon) or an electron beam aperture glued with carbon cement is used. Both methods are less precise:

  • measuring beam current on carbon will not account for backscattered and secondary electrons
  • an aperture glued with carbon cement lacks a larger cavity; it it only precise when underneath the aperture a larger cavity has been constructed.

 

EM-Tec B100 Faraday cup construction
The EM-Tec B100 consists of single piece of brass with outside dimensions of Ø2.5 x 2mm. The top of the Faraday cup includes a Ø100µm hole. Behind this 100µm aperture, there is a larger cavity of approximately Ø1.4 x 1.5mm.
When used, the EM-Tec B100 Faraday cup must be mounted on a sample stub or sample holder with conductive carbon cement and the small Ø100µm aperture facing the pole piece of the SEM.
When the electron or ion beam is directed into the middle of the small aperture; all primary, backscattered and virtually all secondary electrons are absorbed by the Faraday cup and hence the beam current can be determined. When properly used, the EM-Tec B100 Faraday cup efficiency is >99% in the 2-30kV range.

Specifications of the EM-Tec B100 Faraday cup:

Product #

#36-000800

Material

Brass

Outside Diameter

2.5mm

Height

2mm

Hole size

Ø100µm

Cavity size

Ø1.4 x 1.5mm

 

Directions for using the EM-Tec B100 Faraday cup
When using the EM-Tec B100 Faraday cup on your SEM, FESEM, FIB or Microprobe system, the holder with the Faraday cup must be electrically connected to the sample stage. Select point mode on your system and make sure that the beam is directed in the middle of the aperture of the Faraday cup. If your system includes an absorbed current meter you can use this meter to measure the beam current.
If your system does not include an absorbed current meter, you have to connect a pico-ammeter (range 10-3 to 10-12 A) using a ground connection on the outside of the SEM chamber. Most SEMs provide such a connection on the outside of the SEM chamber or on the SEM chamber door. This is most likely a BNC connector capped with a metal cap to ensure proper grounding. Removal of the metal cap and connecting the pico-ammeter enables measuring the beam current. The power to the pico-ammeter needs to be provided by the same electrical circuit as the SEM. When removing the pico-ammeter, re-install the metal cap on the connector.
If the grounding cable from the SEM sample stage is connected to the inside of the SEM chamber, please consult the manufacturer or your service engineer if they can provide an absorbed current feedthrough.

With the measurement circuit installed, mount the EM-Tec B100 Faraday cup on the SEM sample stage and position the Faraday cup under the beam. Use point mode (or very high magnification scanning mode) to direct the beam into the middle of the aperture of the Faraday cup. Adjust condenser settings to change or require the desired beam current, note the beam current.

 

Maintenance, handling and cleaning
Store the EM-Tec B100 Faraday cage in a dust free and clean environment. Remove dust for use with a blower or duster.
Handle the EM-Tec B100 Faraday cup with plastic tweezers or plastic tipped tweezers to avoid damage of the relatively soft brass.
When used under normal conditions there is no maintenance or cleaning needed. If the aperture opening gets contaminated or charging occurs, the aperture opening needs to be cleaned:

  • either use a plasma cleaner to remove carbon deposits
  • or use mechanical cleaning with Wenol metal polish (#53-000100) or diamond polishing paste (29-001599) and wooden picks (#52-005023). Sonicate afterward in a 50/50 solution of isopropanol/aceton and let dry. If solvents are used, remounting with conductive carbon cement will be necessary

 

TSB 36-000800 EM-Tec B100 Faraday cup 2016-07-15 Revision 1

 



SEM Supplies

TEM Supplies

Calibration

Sample Preparation

AFM / SPM

  SEM Sample Stubs
  Carbon tabs
  Sample Stub Adapters
  SEM Stage Adapters
  SEM Sample Holders
  SEM Preparation Stands
  Filaments/Cathodes
  Silicon Finder Grid
  Gatan 3View Pins
  FEI Volumescope Pins
  SEM Stub Storage Boxes
  Phenom Supplies
  JEOL NeoScope Supplies
  Hitachi TM series Supplies
  Field & lab sampler kits

Instruments


  Acoustic Enclosures
  Critical Point Dryers
  Cressington SEM Coaters
  HI-Res IR Chamberscope
  TEM Sample Prep
  TEM Grids
  TEM Support Films
  Silicon Nitride Films
  K-Kit wet cell holder
  Graphene Films
  Grid Storage Boxes
  Cryo Grid Box
  TEM sample staining
  3mm embedding tubes
  Filaments/Cathodes
  Cryo Pin for U-M
  Eyelash manipulators

FIB Supplies


  FIB Lift-out grids
  FIB low profile stubs
  FIB grid holders
  FIB pre-tilt holders
  FIB Grid Boxes
  SEM / FIB Magn. Calib.
  SEM Res. Test Spec.
  EDS / WDS Calibration
  TEM Calibration
  AFM / SPM Calibration
  LM Magn. Calibration

Vacuum Supplies


  Bullseye Vacuum Gauges
  Quick-check Gauges
  KF/NW Vacuum Parts
  Vacuum oil and grease
  Vacuum sealant
  Vacuum sample storage
  Evaporation materials
  Evaporation baskets
  Quartz QCM Crystals
  Sputter Targets
  Carbon Rods & Fibers
  Quartz QCM Crystals
  Supports & Substrates
  SEM Preparation Stands
  Tweezers
  Probes & Picks
  Cryo Jug & Container
  OCT cryo compound
  Applicators & Swabs
  Plastic Transfer Pipettes
  Cutting Tools / Scissors
  Conductive Paint/Cement
  Conductive Metal Powders
  Conductive Tapes &Tabs
  Non-conductive Adhesives
  Stainless Steel Mesh
  Sample Storage
  Tools
  Replication sheets
  Preparation mats & tiles
  Cleaning / Gloves
  Diamond Polishing Paste
  AFM/SPM Discs
  AFM/SPM Disc Pick-up Tool
  AFM/SPM Holders
  AFM/SPM Disc Storage
  Cantilever Tweezers
  AFM/SPM Discs Tweezers
  Mica Discs
  HOPG Substrates


LM


  Correlative Cover Slips
  Glass Microscope Slides
  Glass Cover Slips
  Quartz Microscope Slides
  Quartz Cover Slips
  Black metal slides
  Slide storage boxes
  Calibration
  Plastic Transfer Pipettes
  Optical Lens Tissue
  Glass Petri Dishes