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FEI Sirion Scanning Electron Microscope (SEM)

Overview

The instrument is an FEI XL30 Sirion SEM with FEG source and EDS detector located on the first floor of McCullough Building, Room 108.

Principles of operation: In a scanning electron microscope (SEM), a fine beam of electrons is scanned across the surface of a specimen in synchronism with a spot on the display screen. A detector monitors the intensity of a chosen secondary signal from the specimen (for example, secondary electrons) and the brightness of the display spots controlled by an amplified version of the detected signal. If, for any reason, the intensity of the emitted secondary signal changes across the specimen then contrast will be seen in the image on the display screen. The resulting image is strikingly similar to what would be seen through an optical microscope; the illumination and shadowing show a natural-seeming topography.

It is important to remember that the image formed in an SEM is not necessarily that of the surface. As the electron beam penetrates the sample, the interaction causes excitation of secondary, backscatter, and Auger electrons; characteristic and Bremsstrahlung x-rays; and photons. It is possible, by choosing the electron energy, to control the depth to which the electrons penetrate and the type of emitted signal used to form the image. While this gives the microscopist a great deal of control over the nature of the final image, an understanding of how the image is formed is required to interpret it sensibly.

 

 

Available spot sizes and beam currents (UHR mode):

Spot

1 kV
WD = 2 mm

5 kV
WD = 4 mm

15 kV
WD = 5 mm

30 kV
WD = 6.2 mm

nm
pA
nm
pA
nm
pA
nm

pA

1
2.5
0.7
2.3
3.0
1.5
9.0
1.5
20
2
2.5
5.2
2.3
18
1.5
33
1.5
40
3
2.7
20
2.4
71
2.2
130
1.7
140
4
2.8
90
2.5
310
2.5
550
1.8
550
5
3.1
390
3.7
1400
3.5
2200
2.0
2200
6
3.6
1400
4.7
7200
5.0
9300
3.8
8500

Note: These spot sizes are approximate, and are highly dependent on instrument and specimen conditions. This chart is to be used as a guideline only.

Advanced techniques:

  • Energy Dispersive Spectroscopy (EDS)

Restrictions on samples:

The sample material must be able to withstand a high vacuum environment without outgassing. It must be clean. It may be attached to the sample holder using a suitable SEM vacuum-quality adhesive (ie., C or Ag paint), or clips. The sample should be electrically grounded to the sample holder to minimize charging. If the sample is nonconductive, the sample may be coated with a conductive layer (we can provide C or Au/Pd coating upon request). Note that rough surfaces should be conformally coated. The workstation can accommodate up to 100 mm (4”) wafers.

For Au/Pd (60:40 ratio) coating on your samples, please do the following:

  • Bring your mounted sample(s) in a case (labeled with your contact info, any non-standard parameters, and the time of your scheduled microscope session) to the Sample Mounting Lab in McCullough 101.  The overhead cabinet to the right of the coater is labeled with one side where you will drop off your sample (“Samples to be coated”), and the other for where we will place the coated samples.
  • Email “samplecoat@lists.stanford.edu” to let us know that you have dropped off your sample(s) - similarly indicate when your microscope session will be.  Please remember that we may not be able to get to it immediately, so last-second requests will be difficult.
  • When we are finished coating, we will put it back in the “Coated samples” side of the cabinet and you can pick it up.

Contact Information

Richard Chin
Office: (650) 723-8142

Ann Marshall
Office: (650) 723-3572

McCullough 108
Office: (650) 724-9077

 

Research Examples

SEM image of Silica Nanoshells. See Stanford News for more details on the research. Image courtesy of Yan Yao (Cui Group, Stanford)

Getting Started

In order to become a qualified user on the Sirion SEM, you need to follow these steps:

Training Information

It is recommended to have three training sessions (generally, 2 standard plus 1 final) to become authorized on the Sirion SEM.  To sign up for training on the Sirion, please read and follow these instructions in the order listed here:

  • Startup instructions for the instruments available here. It would be helpful for you to print them out and bring them to your sessions.
  • Basic training for inexperienced SEM users requires a minimum of three two-hour sessions which can be done in groups of two, save the final training which is done solo. Training slots are regularly posted on the SEM calendar for up to two weeks in advance. Additional training in specific SEM techniques is available on an as-needed basis following basic training. SEM users with prior experience will be trained at the level required.
  • To edit fields on the calendar, you must log in (found on the right hand side).
    Username: sirion
    Password: xlD1540 (Note: the second character is a lower-case "L")
  • Look for training slots on the respective sign-up calendars marked "training w/(trainer)" (note: "reserved for trainers" does not equal "training w/ (trainer)"; early entries into such slots will be deleted). Click on the pencil icon to add your name (to the subject line) and contact info (further down the page). The final entries should look like:
    "training w/ rich/ jane/ joe" for a regular training, and
    "training w/ rich/ pat (final)" for a final training.
    Training slots are posted Monday mornings for the second following week. No more than two people per session, please, and only one person if it is a final. Furthermore, please do not sign up for successive trainings on the same day; from past experience, the information is not absorbed as well, and all too often people have to re-take their final.

 

Notes:

  • If you are having difficulty scheduling your "final" training, please email Rich Chin (rwchin@stanford.edu) your availability, AFTER you have signed up for your first two trainings, and he will put you in a final training slot. Note that a range of times will be necessary, as the slots are determined by the availability of the trainers. Check the calendar for your final.
  • For the first several sessions following the successful completion of a "final" training, you will be allowed to sign up by yourself, but only during business hours. Further details will be explained when you receive your beginner's permit. Full (24hrs/7days) access will be granted after successful completion of the permit.
  • For advanced techniques (i.e., EDS):
    • After you have passed your final training, you may sign up for one of the technique sessions. These advanced sessions are offered on an as-needed basis, and up to 6 people may sign up for each one. These are designed to provide a basic introduction to the technique, and further training may be required by the instructor. Note: you will be charged for no-shows if you do not let us know at least 12 hours in advance of your scheduled time. 

Any further inquiries may be directed to Richard Chin (rwchin@stanford.edu).

Other information