Things to Consider When Purchasing a Scanning Electron Microscope

Things to Consider When Purchasing a Scanning Electron Microscope

Oct 15, 2021, 10:28:46 AM Business

The growing focus on nanotechnology is the driving force behind the rise of the scanning electron microscope (SEM) market. The increasing demand for Critical Dimension (CD SEMs) is also expected to bolster the SEM market even further.

 

Credit the growing need for product miniaturization, combined with increased market demand to the popularity of nanotechnology at present. Nanotechnology, which employs nanoparticles, has become an indispensable part of our everyday lives. It has found endless uses in several industries, such as medicine, food and cosmetics, the environment, and advanced manufacturing.

 

Nanostructure requires the use of electron microscopes such as SEMs. Due to the numerous benefits of nanotechnology in biomaterials, electronics, medicine, and microfabrication, both the private and public sectors are investing heavily in research and development to capitalize on the potential benefits of nanotechnology. Ultimately, significant breakthroughs in nanotechnology will contribute to the increased demand for SEMs.


What is a Scanning Electron Microscope?

A scanning electron microscope is the second most common type of electron microscope, which produces nanoscale specimen images by scanning their surface with a focused electron beam. It’s primarily designed for imaging the external portion of bulk samples, with the capability of imaging both cryo (hydrated) and dehydrated specimens.

 

There are thermionic and field emission sources available, which are similar to those found in transmission electron microscopes (TEMs). Environmental SEM (ESEM) and variable pressure (VP) systems have just been introduced as one of the latest types of SEM models available, requiring minimal sample preparation before imaging.

 

Surface imaging is the primary objective of SEM, so controlling the electron specimen interaction volume is needed to ensure that only surface information is obtained. When testing SEMs, it's essential to monitor the machine's imaging capability at low accelerating voltages.

 

Compared to other electron microscopes, SEMs have a broader range of applications. Some SEM systems can be configured to image thin samples in scanning transmission electron microscopy (STEM) mode using a specially developed STEM detector. In contrast, others are designed to capture broad areas of surface information using image stitching and acquisition automation software.


How Much Does a Scanning Electron Microscope Cost?

If you work in an academic institution, research, and development, or the commercial industry, procuring an in-house electron microscope is highly beneficial. However, before purchasing, you need to be aware of everything you need to consider to have an idea of how much an electron microscope costs, 

 

Firstly, you need to know that electron microscope are available in several styles and unique variations. These advanced imaging instruments range in price between thousands to millions of dollars, depending on the type of electron microscope you are eyeing to have. For traditional tabletop SEMs, a safe price range is between $50,000 to $200,000, or up to a million dollars for the higher-end ones,

 

As a result, the range of their capabilities is extensive. The increased precision of resolution (aka magnification) and sample size both exponentially affect the prices of electron microscopes. Before delving into the exciting choices available from various suppliers, you must first develop a clear plan about your needs.

 

In this write-up, we will list the top things you need to consider when purchasing an SEM. Feel free to use this as a guide to help you make the best buying decision.


Tip #1: Determine who’s going to use the device and for what specific application.

Before purchasing, it’s best to consider who’s going to use the device. Will there be at least one or up to a few experienced users, or will there be multiple operators with different levels of EM experience? Are all of the system's users familiar with SEM, or should you adopt a "black box" solution?

 

You need to be aware that most of the systems out in the market today have built-in features that allow even inexperienced users to achieve good imaging results. Ask for the availability of these features that assist novice users and prevent potential harm, but not before making sure that these options won't restrict the system's capabilities in the future.

 

With regards to application, standard desktop SEMs are usually appropriate for single-user or simple applications. However, for bigger laboratories with a user group that has varying skill levels and needs, a more advanced tabletop or entry-level full-size SEM system might be a better fit.


Tip #2: Tabletop System vs. Floor Model

When purchasing an SEM, your choice will come down to which is more appropriate, a tabletop or floor model?

 

Your first instinct might be to choose one of the relatively recent, compact Tabletop or Desktop SEM systems to avoid recurring service or maintenance costs associated with older and pricier large floor model systems. Although in recent years, a range of portable floor models have been launched, which are often easier to maintain than tabletop systems since they're crammed full of components to reduce their overall size.

 

If there are restrictions prohibiting a compact floor model from being installed in your facility, you may opt for a Tabletop SEM. They are reasonably easy to maintain and repair with or without the help of a technician. Further, there’s no longer a need to settle for a Desktop SEM that can restrict your capabilities and potential expandability in the future. Compact floor models are now very similar in terms of size to traditional tabletop or desktop SEM systems.

 

Another thing to consider is the price involved. At present, the cost of tabletop systems and newer compact floor models have gotten much closer, blurring the right choice from a cost standpoint.


Tip #3: Determine the Accelerating Voltage that’s the Right Fit for your Application

Are your samples beam-sensitive? Most tabletop SEMs have a low voltage limit of 5 kV. If you’re working with beam-sensitive specimens, consider a model with variable voltages down to 1kV, comparable to full-size SEMs. They often allow voltages as low as 0.1kV. In line with this, it's also important to measure how well the SE detector can process images at such low voltages.

 

Will you or any of the users be performing Energy Dispersive X-Ray Spectroscopy (EDS)? The majority of tabletop SEMs have a maximum accelerating voltage for the electron beam of 15 kV. This minimal accelerating voltage doesn't allow the collection of acceptable spectra in the 8-15 keV range for many essential elements such as Molybdenum, Bromine, Zinc, etc. This 15 kV restriction requires spectral peaks with energies less than five keV, which often have several overlapping components. By matching the beam to the sample's composition, an electron beam with an accelerating voltage of up to 30 kV will provide better imaging and EDS results.

 

Keep in mind that the device's ability to capture SE images on non-conductive samples at varying accelerating voltages allows you to conduct a comprehensive analysis of surface processes.


Tip #4: Determine the Imaging Capacities You’ll Require

An electron beam can interact with a specimen in a variety of ways. Most tabletop SEM suppliers advertise models with a single backscatter electron detector (BSE) for imaging and secondary electron imaging as "optional." BSE helps determine elemental contrast or atomic number in a sample, but not surface topography.

 

However, the most recent models out in the market now provide either a regular or optional Secondary Electron (SE) detector, which produces excellent images for surface morphology and topography.

 

You should look for SE detectors that are the same as those used in full-size SEMs. In the case of non-conductive samples, determine if the SE detector can process imaging in charge reduction or low vacuum modes. Since some SEM systems on the market produce very flat images with no contrast, the SE detector’s contrast range is typically an essential capability you need to grasp fully.

 

Without an Everhart-Thornley type SE detector, your images will never have the best topographic information and will lack the contrast of images acquired with more sophisticated SEM systems.

 

Finally, identify if you need Transmission Electron Microscopy to analyze tissue sections, nanoparticles, or thin metallic sections. Several full-size SEMs and a few Tabletop SEMs have STEM detectors that enable you to analyze samples on standard TEM grids. This feature gives the SEM dual functionality, making it a more valuable tool in your lab.


Tip #5: Take Note of your Magnification and Resolution Requirements

Most tabletop SEM companies advertise Magnifications of up to 100,000x or more. As a primary user, it's up to you to fully understand what this number means for your applications.

 

In reality, however, actual magnification relies on the size of the image on display. Having said this, you must keep in mind that resolution is a better indicator of the microscope's true capabilities.

 

When projected in a presentation, a 10,000x magnification on a microscope display could easily become 100,000x. The increase is only meaningful if it provides you or any of the other users with additional information. There is such a thing as "hollow or empty magnification," which occurs when the device reveals no further detail resulting from the image resolution. Avoid being drawn in by silly claims of 1,000,000X magnification made by some suppliers. At 1,000,000X, a single ATOM (around 0.1 nm) will appear in an image at 100 microns across, approximately five times the diameter of a human hair, and easily observable but isn't at all feasible at this price range.

 

The actual image resolution is also affected by electron optics and imaging control setpoints. Consider the type of electron gun and other factors that are likely to influence beam cohesion, such as a fixed aperture or the ability to change the aperture size.

 

This functionality allows you to configure the optics to achieve the best image detail possible. Similarly, having operational control over beam stigmation at high magnification helps you come up with better images.

 

Eventually, you can turn to your applications to serve as a guide. Answer the question, "What do I need to see in this sample?" While standard desktop SEMs will do just fine for samples requiring lower resolution, you should be willing to invest in a desktop SEM capable of capturing finer detail in the sub-micron range.


Summary and Key Takeaway

Once you decide to purchase a new SEM, you're likely to be aware of your need for increased SEM capability. The primary decision parameters when choosing an SEM are its cost, usage and applications, as well as the operators that'll be involved.

 

As in all other fields, the secret to success in microscopy is to match the instrument to the application. Invariably, the question you should have right at the start is, "How good is good enough?"

 

Ultimately, you shouldn't base your decision solely on the scanning electron microscope cost. The buying process requires extensive research and a series of impartial tests to narrow down your machine choices.

Published by Simon Wilson

Written by Simon Wilson

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