TOF-SIMS system and viewing optics; no primary ion gun

This system would be of interest to someone who already has a pulsing, microfocused gun that can be rastered across the sample surface, or who wishes to purchase such an ion column from a third party manufacturer. The SED system permits primary beam focusing. Please note that to acquire TOF-SIMS images into the data system, the Kore SIMS imaging module requires that the primary column raster scanner has external X and Y scanning inputs, and that the gun also has suitable pulsing plates for fast pulsing. Kore is also able to supply a suitable fast pulser for the ion column if required – details upon request.

• Flight tube and R-500-6 dual slope reflectron analyser with effective flight length of ~3metres, capable of producing mass resolutions of up to 4,000 (FWHM) under suitable (primary column) conditions
• Adjustable reflect and retard voltages for setting energy acceptance and optimising time focussing
• SIMS extraction optics for secondary ions, with X, Y deflectors. 1mm field of view for the secondary ion optics
• 25mm diameter dual micro channel plate detector (DMCP) with flange mounted pre-amplifier
• 3U HV controller powering the DMCP detector, the spectrometer, ion gun blanking / unblanking, electron gun control
• 3U TOF-MS logic controller for switching easily between positive and negative SIMS
• 3U HV supplies unit housing all the high voltage supplies, and providing sample potential adjustment (energy filtering)
• Stage pulser. This unit applies the extraction field between the sample and the SIMS extraction lens. Therefore, the sample must be able to float away from ground potential. A tuneable, delayed extraction allows ‘electrodynamic bunching’ of the secondary ions, resulting in high mass resolution in the mass spectra
• 4GHz (0.25ns) time-to-digital converter (TDC)
• Data acquisition computer- typically a 3U rack-mounted PC with GRAMS A/I spectroscopy software and Kore Technology mass spectral extensions for TOF-SIMS, 19″ LCD screen etc
• Pulsing, low-energy electron gun for charge compensation of insulating materials (~30eV electrons) and emission-stabilised electron gun electronics (fitted into HV controller)
• 3U Sample viewing control unit, providing secondary electron imaging electronics, sample illumination power (on/off and low/medium/high) and camera power
• Zoom microscope optics (optical view) with colour camera (all demountable for baking)
• Monitor for camera output
• Dichroic chamber light
• Secondary electron detector (Channeltron®) and SED pre-amplifier unit
• Imaging electronics and Kore software extension for imaging

As above (System 1), plus:

• 5keV Cs⁺ primary ion column (two lens) with high-speed pulser producing 50ns pulses at the sample every TOF cycle of 100 microseconds. Typical primary current for static SIMS analysis is 5-10nA (d.c. beam before pulsing). Primary probe size down to ~100-200um
• Cs column controller with ion source heater control, X, Y beam steering, Lens1 and Lens2 control, raster scanning, Faraday cup for beam current measurement

The Cs beam is normally pulsed, resulting in low primary ion fluxes at the sample surface (for static SIMS analyses). However for sputter cleaning, the beam can be rastered and turned on continuously to remove unwanted surface hydrocarbons from inorganic samples.

System 1:

The spectrometer will be pumped out to a suitable vacuum level, and cabled to the control electronics. All the control voltages will be applied and mass ‘spectra’ (essentially dark noise) acquired into the data acquisition system to demonstrate that it is functional. The system will be switched between positive and negative ion SIMS, and checks will be made for the appropriate voltage switches. Oscilloscope traces will be captured and presented for the output of the ion detector. The optical microscope system, camera and illumination will also be tested

System 2:

The spectrometer will be fitted to a Kore test chamber along with the Cs ion gun, and cabled to the various control electronics. The primary beam will be pulsed and bombard a sample. The stage pulser will be attached to the floating sample. Secondary ions will be extracted. Data in positive and negative SIMS will be acquired into the data acquisition system and mass spectral data presented as evidence of a readiness to ship the system. The mass resolution will be >1000M/dm (FWHM) for atomic species > mass 40, and >2000M/dm (FWHM) for organic molecular ions > mass 40.

We have provided the standard ‘re-entrant’ distances of the various Kore components into the client vacuum chamber (see accompanying sketch). The extraction nose of the secondary ion optics is intended to be located at 5mm from the sample surface. Requests to alter the re-entrant distance of the optics can be considered, but will incur some extra design costs and affect the magnification of the optics.

The Cs ion column has a re-entrant distance of 228mm, but could be shortened by considering an additional 70OD CF pipe section.

Feel free to contact us, and one of our mechanical engineers will be happy to advise you on how to match our components to an existing chamber.

For now we assume that you already have a sample stage. The key issue is that it should be possible to apply a high voltage of ~2kV to the sample stage in your TOF-SIMS chamber, i.e. the sample holder must be able to float away from ground potential. This is a key property. The Kore stage pulser needs to be connected via an SHV connector to the sample stage.