SEM
Camscan Series II
Scanning Electron Microscope
Gould-Simpson room 118
Phone: 520-621-8107
- General Summary
- Instrument
- Software
- Analytical Capabilities
- Sample Requirements and preparation
- Checkout procedures
- Manuals
General
Summary
A scanning electron microscope is an electron microscope designed primarily for
high magnification imaging, and may also be used for semi-quantitative analysis
using an energy-dispersive spectrometer. It is capable of generally higher
spatial resolution but inferior analytical sensitivity compared to the electron
microprobe. This Camscan Series II SEM can acquire digital secondary-electron
and backscattered-electron images, and digital energy-dispersive x-ray maps.
Semi-quantitative energy-dispersive microanalysis can be performed as well.
Most of the periodic table can in principle be analyzed (Beryllium through
Uranium), subject to several important considerations and limitations related to
measurement using an energy-dispersive spectrometer. The analytical sensitivity
is typically 0.X% (i.e. several thousand ppm), but can be as high as several
weight percent for problem elements. The volume sampled is typically a few
cubic microns, corresponding to a weight of a few picograms. The quality of
imaging and analyses performed depend on the quality of sample preparation,
character of the sample material, and availability of appropriate primary and
secondary calibration standards for the desired elements. A precision
approaching a few percent relative and accuracy of 5-10% can be expected with
this instrument. We have acquired a Cameca Series II Camscan SEM equipped with
a LINK EDS detector. The instrument was installed in room 118 GS.
Instrument
The instrument is a Camscan Series II Scanning Electron Microscope. The Camscan
is capable of obtaining images over a wide range of accelerating potential
(from about 2 KV to 30 KV), and probe current (from low picoamp to about 15
nanoamps), which can be used to study a variety of materials. It is equipped
with an Everhart-Thornley secondary-electron collector for secondary-electron
imaging, a Robinson-type backscattered electron detector for
atomic-number-contrast imaging, and a relatively slow speed absorbed current
imaging system. The backscattered detector is a large-solid-angle, low noise,
high sensitivity detector that is capable of high atomic number contrast (less
than 0.1 Z) at comparatively low probe current. The instrument is optimized for
concurrent backscattered electron imaging and x-ray analysis at the same
working distance. An on-board frame averaging system allows one to integrate
several scan frames in order to reduce noise and obtain a cleaner image.
Compensated brightness and contrast adjustments are automatically performed by
the imaging system, and dynamic focussing is available for samples having a
highly tilted surface. The working resolution for this instrument is dependent
on the sample being studied, but is approximately of 100 nm.
The sample stage assembly is capable of motorized movements in the x-axis and
y-axis directions, and manual adjustments can be made for z-axis, z' eucentric,
rotation, and tilt. The sample chamber is capable of handling large samples,
although it is usually preferable to minimize the sample size if possible.
Sample holders are available for small samples via 1 cm pin-type mounts, 1 inch
circular thin sections, 1 inch thick mounts, petrographic thin sections, and
1.25 inch metallurgical mounts.
The instrument is
outfitted with a Link Analytical pentafet SiLi energy-dispersive x-ray
spectrometer which has a turret control that allows either a Beryllium window
or a Boron Carbide window to be used for normal or light element x-ray
acquisition, respectively. The Link detector is interfaced to an
Digital imaging and x-ray
mapping are performed using the 4Pi Systems Scanning Interface Unit for digital
beam control. Digital images may be acquired at magnifications up to 15,000X,
and a large number of x-ray maps may be acquired simultaneously, using the Link
EDS detector.
Software
Digital secondary-electron and backscattered-electron images and x-ray maps are
acquired using special acquisition plug-ins that can be used by the NIH Image
program. Digital images can be acquired using a range of pixel dwell times and
image resolutions suited to the needs of the sample being studied. Image
resolutions of about 2048x2048 pixels achieve the line resolution observed for
Polaroid film micrographs. Digital images can be acquired typically in about 30
seconds (longer for high resolution, long-dwell images), and x-ray maps can be
acquired in as little as 15-30 minutes, although mapping runs typically require
several hours.
Once acquired, digital images can be processed either on-line or off-line using
NIH Image, Adobe Photoshope, or a variety of digital image processing packages.
NIH Image allows one to perform spatial and fourier transform image filtering,
the application of a variety of color lookup tables, and can be used to
generate binary images which are then used for feature sizing. Automated
particle counting and sizing, morphometric feature analysis, and phase
abundance determinations can be performed using NIH Image.
Analytical Capabilities
Quantitative results with a relative accuracy of better than 5% and detection
limits of better than 0.5% can be readily obtained.
TOP
Sample Requirements
- Samples prepared for imaging applications can be
unpolished rough samples, but must be electrically conductive or need to
be coated with gold using the gold sputter coater.
- Samples prepared for analysis work should be prepared
as flat, polished solid mounts up to 1 inch in diameter, and coated with a
23 nm layer of carbon using the carbon evaporator.
- Samples must be clean and stable in a 10-5 torr vacuum
environment, and should be as small as possible to minimize outgassing and
charging effects.
Sample Preparation
Your samples should be
completely polished, coated, and mounted (if applicable and reasonable) before
the beginning of your session.
SEM Checkout Procedure
The Camscan SEM is easy to use, and digital imaging and x-ray analysis are
conveniently performed using the manuals. In order to use the SEM in an
unsupervised capacity, you need to obtain an instrument checkout. You can do
this as follows:
- Download a copy of the Camscan manual and read it.
You will be running the instrument on your own, so look through the manual
to prepare yourself for the checkout session.
- Download a copy of the Digital Imaging and X-ray
Mapping Guide. This set of instructions will show you how to acquire
digital images and x-ray maps.
- Download a copy of the DTSA Manual if you plan to do
energy-dispersive x-ray analysis (either qualitative or quantitative).
- If it is convenient for you, sit in with another SEM
user to observe how the basic operations are performed on the instrument.
Find out if a member of your research group is already checked out on the
instrument and see if you can sit in on their session.
- Schedule time with Lab Manager to get an SEM
checkout. Your checkout will probably take two sessions to complete. In
the first session you will be shown how to do sample prep and coating,
instrument startup, sample exchange, filament saturation and column alignment,
imaging, and shutdown. You will be able to work on your own sample, but it
will be a relatively short amount of time. In the second session you will
demonstrate that you can competantly perform the operations that you were
shown in the first session, and if applicable, use of the DTSA program and
EDS analysis topics will be covered.
- Lab Manager will place your name on the list of
authorized users if and when you are able to correctly use the instrument
and the software in an unsupervised capacity.
- You will be able to use the instrument during normal
facility hours after a checkout.
Download Manuals
You can download most of the manuals that you need from this web page. These
documents are in pdf format, so you will need Adobe Acrobat reader in order to
read them. The Acrobat reader for your computer platform can be obtained from
Adobe at this link.
Camscan SEM Manual
This manual covers the function and operation of the Camscan Series II Scanning
Electron Microscope. It guides you step-by-step through the startup, sample
exchange, filament saturation, imaging, and shutdown procedures. This manual is
the first you should read before getting a checkout on the Camscan. Download the Camscan SEM Manual.
Digital Imaging and X-ray Mapping
This is the manual you need in order to do digital secondary-electron and
backscattered-electron imaging and energy-dispersive x-ray mapping using the
Camscan. It guides you through the step by step procedure for acquiring digital
images and x-ray maps. It is the second manual you should read before using the
Camscan. Download the Digital Imaging and X-ray Mapping Manual.
NIH Image Program and Manuals
The NIH Image program is public domain software, and is available for the
MacIntosh and PC computers. You can download the software and documentation to
run on your computer, and you can also find links to many other sources of
digital image processing programs and related materials. The NIH Image web site
is http://rsb.info.nih.gov/nih-image/, and
you can also reach their ftp site at ftp://zippy.nimh.nih.gov.
Energy-Dispersive X-ray
Analysis
The DTSA manual is a step-by-step guide to setting up the DTSA program for
quantitative energy-dispersive analysis. This guide will show you how to set up
an analytical experiment, how to acquire EDS spectra, how to set up the
multiple linear least-squares fitting routine, and how to set up the CITZAF
correction program. This manual assumes that you know the basics of EDS
analysis. See the references section if you don't know anything about EDS. Download the DeskTop Spectrum Analyzer Guide.
TOP
For scheduling, prices
and other details, contact Dr. Ducea at ducea@geo.arizona.edu
or 621-5171.
This
page was last updated
Questions or comments mail to mducea@geo.arizona.edu