The FEI NanoSEM is a Schottky field emitter SEM that has very high resolution down to low accelerating voltages, thanks to the UHR immersion mode in which the focussing field(gradient) extends below the pole piece of the final lens so that the specimen can be placed 'in' the lens at very small working distance.
The resolution at 15 kV is 1 nm (1.3 was measured in the acceptance test) and 1.8 nm at 1 kV (2.0 nm was measured in the acceptance test). The resolution in STEM mode is sub-1 nm!
The NanoSEM has a mechanical stage with motorized x, y, z and rotation, manual tilt from -10 to +90 degrees is possible. The stage is tilt-eucentric at a working distance of 5.000 mm. The stage travel is 50 mm in X and Y direction. Accuracy is 100-200 nm. Available working distance is 1-25 mm, minimum working distance depends on accelerating voltage (1 mm at 1 kV, 4.6 mm at 15 kV)
The system has a HV (specimen chamber pressure is below 1e-6 mbar) mode and a LOWVAC mode where the chamber pressure can be up to 1.5 mbar. In the LOWVAC mode degassing specimen can be observed, and for chemical processing and avoiding charging (in the case of a nonconducting specimen) water or an auxilary gas can be introduced in the sample chamber (pressure can be set in the control software). When the chamber pressure is 1.5 mbar, the final lens is pumped by the drag stage of the TMP, the aperture pumped to 1e-6 mbar by the TMP, pressure in the lower IGP is 1e-8 mbar and the FEG source is still kept at 1e-10 mbar by a series of apertures! In the HV mode the vacuum can be improved by using a cryo-can (an LN2 cryopump) to reduce contamination.
Detectors are a standard ETD with variable bias, a backscatter detector, a TTL-S/B detector, a LVD gaseous detector for low vacuum, a CRT/LVD detector with a larger PLA, a GAD/BSD backscatter detector and a STEM detector (bright and dark field) for transmission mode. The ETD counts secondaries (having a low kinetic energy and only escaping from the specimen if they are created near the surface) and backscattered electrons (that interact with a nucleus and 'bounce' back at near incident beam energy) at positive bias, if a sufficient negative bias is applied the secondaries can't reach the ETD). The backscatter detector has a larger backscatter yield than the ETD. At very low working distances in the UHR immersion mode the yield of the normal detectors will drop, in this case the in-lens detector is used (the electrons spiral into the lens, are accelerated away from the lens axis and detected. Depending on bias, secondary (plus backscatter) or backscatter electrons are counted. At high pressures electrons collide with the gas before reaching any detector, the gaseous detector accelerates the electrons so that in 1 mean free path the ionization energy of the gas is reached: the a collision avalanche in the gas acts as the amplifier (too high potentials creating sparks or a continuous discharge must be avoided of course). The STEM detector has multiple segments so that Z-contrast, bright and dark field are available. A CCD camera with infrared LED illumination is present in the vacuum chamber so that the stage, specimen and their position with respect to the final lens, detectors etc. can be observed continously.
The system has place for 2 GIS's. Currently a Pt deposition GIS is mounted. It is configured for use at eucentric height (5mm). When the GIS needle is inserted it drives to a position 75 um above eucentric height and 100 um to the side of the beam center. The GIS can heat a substance and when a valve is opened it injects gas onto the substrate at the beam incidence point. The gas can be used for EBID or etching.
A cryo-transfer system is mounted that allows a sample to be cryo-fixated by rapid cooling to 77K and subsequently be transferred to the SEM via the cryo-transfer system's loadlock. In the loadlock a sputtering source is present.
A manipulator to mount single carbon nanotubes onto various substrates has been developed.
Technical backups of the user PC will be made periodically. There are no arrangements with system management to do a full periodic backup right now, so you are responsible for backing up your own data, this can be changed by request.
It is necessary to follow the 'NanoSEM intro' before starting. This will typically take an hour or two (but is depending on your SEM experience) and will enable you to use the SEM in HV mode for imaging. Your software account will be created and you will get NanoSEM access to the reservation system.
If you want to use the system for special applications and need to use a GIS, change detectors or do any other activity that requires more tools than the Allen key for stub mounting it is necessary to follow an 'application intro'. Contact Marcel Hesselberth in this case.
If the SEM will not be used for a while (say, more than 2 days), go to standby mode by stopping the microscope, exiting the microscope server and shutting down the control PC (BUT DO NOT PRESS 'SHUTDOWN' button in the microscope server)
If you want to tilt or use a GIS, you need to set eucentric height. For tilting it is handy so set eucentric very accurately, it is done as follows:
If the microscope computer crashes:
Always deposit at eucentric height! (below eucentric height the deposition rate is very low. Driving the GIS needle in above eucentric will cause a collision between the needle and the specimen!)
Material | Date | Sample ID | Process parameters | Measured with | Result | Rate |
---|---|---|---|---|---|---|
Pt | 20050415 | Pt1 (Marcel) | Spot 5, 50% overlap, 1000 passes, 1 us dwell | AFM | - | |
Pt | 20050601 | Pt (Christianne) | Spot 4, 50% overlap, 248932 passes, 1 us dwell, Vol per Dose = 0.0178 um3/nC, Z-size = 500 nm | nanoSEM (43 degrees tilt) | thickness: 495 nm (+/- 20 nm) | - |