SPI Supplies

Robinson™ Backscattered Electron (BSE) Detector for Scanning Electron Microscopes

Don't settle for anything less than the original (and best) BSE detector for your important work!


The Robinson series of Backscattered Detectors and Cathodoluminescence detectors are no longer being manufactured. Support for current systems will continue for now, but will also be phased out. Please contact SPI Supplies with any of your questions regarding the Robinson Backscattred Detectors.




Introduction:
Although the more common SEM images are formed with emitted secondary electrons, electrons that are backscattered (from the nucleus of an atom) can also contain quite valuable information about a sample's topography and composition. The larger the nucleus, the more the electrons that are backscattered. Often times, one need not resort to the use of EDS (energy dispersive spectroscopy) for elemental information, yet the use of a good, reliable backscattered electron (BSE) detector can give similar information far faster and for lower cost.

Click here for larger view Earlier SEMs typically came from the manufacturer without any BSE detector and if the user needed to obtain this type of information, a separate detector had to be purchased. At some point, some of the manufacturers started incorporating BSE detectors into their new instruments, and the detector used the most frequently was of course the original Robinson BSE detector. We want to stress "original" because over the years, there have been some who have tried to copy the design of the original BSE detector design but they have never been able to duplicate its performance.

Today, there are essentially two different approaches to BSE detectors, the first being the Robinson design, which is based on the use of scintillator technology, and the other based on a solid state detector which utilizes silicon diodes. Dr. Robinson has spent nearly his entire professional life time looking at how to improve an already outstanding product even better, but every time he has compared what one could get using a solid state detector vs. one based on scintillator detection, he has concluded, as have also most of the major column instrument manufacturers, that scintillator technology is clearly superior for most users. For example, with the Robinson BSE detector design, one enjoys high signal to noise at virtually all working distances but with the solid state design, comparable signal to noise data is possible only at short working distances, and a feature of such detectors that greatly limits their usefulness for many would-be users.

So why would I need a Robinson Backscattered Electron Detector on my SEM?
The first but obvious reason could be that you don't have one or perhaps the one you have just no longer works. But much of today's market for the Robinson BSE detector is made up of those who have purchased an SEM with a built in BSE detector that was either built by less experienced design people working for that OEM maker of SEMs or someone made an earlier decision to purchase a solid state design, not realizing the significant shortcomings relative to the Robinson design. Which leads to the next point we want to make: Not all BSE detectors are created equal....... and there are significant differences between the BSE detector that typically can be found as "standard" on a new SEM vs. the Robinson BSE Series 8 Detector.

JEOL® 6700F FESEM Backscattered electron image taken on a JEOL® 6700F FESEM equipped with a Robinson Series 8.6 Backscattered Electron Detector demonstrating changes consistent with severe glomerular nephritis.
So what are these differences?
Some might quite correctly say that it is the difference between "lite" vs. the "full blown" version. For example, low vs. high signal to noise ratio. With the detectors that come as "standard" equipment with new SEMs, one generally can not obtain data at low accelerating voltages whereas with the Robinson Series 8, one can operate at low accelerating voltages quite easily. And of course, with the "manufacturer supplied" detectors, one just can not get the spatial resolution required by most applications. So even though the detectors supplied by the manufactures with new equipment do produce acceptable atomic number (Z) resolution, for the other reasons cited above, a significant fraction of new detector sales are to replace these "standard" detectors that came already installed with one's instrument for a state of the art Robinson Series 8 BSE detector.

Of course, with the passing of time, and the improvements in electronics if not also the scintillator materials, the expression "they don't make them today like they used to" could not be more true. You would no more want to be using a twenty (or even a ten) year old computer than you would want to be using a ten or twenty year old BSE detector. Your work should just be too important to be willing to sacrifice the advantages of installing a new detector. And just like everything else electronic, the price of a new Robinson BSE detector is remarkably low, since with all of the technological advances of the past years, it becomes possible to make a more and more powerful detector for less and less money.

But of course, the real reason why one should consider upgrading their system to a new Robinson BSE detector simply is that it will extend the lifetime and utility of their present SEM. With a good BSE detector, significantly more information can be obtained from the same samples. It could delay by a year or more the day when one really is forced to upgrade their entire SEM laboratory. And in these days of limited or declining research budgets, this is no small consideration.

Last but not least, here is another reason!
Note the BSE image to the right. No, this is not a mistake. It is a BSE image done in a JEOL® 6700F FESEM equipped with a Robinson Series 8.6 Backscattered Electron Detector. Most people would say this is a TEM image. Well, it certain looks like a TEM image but it is not! The sample was from a kidney biopsy, image of a glomerulous with severe renal disease. Now this is really remarkable because absolutely no other BSE detector in the world has demonstrated such resolution and would in essence make an SEM "competitive" with TEM results. But think about it: When done by TEM, such samples are limited to what can be contained on a 3 mm diameter grid. But when done by SEM, one can look at samples enormously larger, ones than measure cm's in size. Several pathologists who routinely perform such biopsies have marveled at the increased productivity if not also higher quality result if the images are obtained by BSE imaging in a FESEM vs. a conventional TEM.

Comments about spatial resolution in the BSE imaging mode with the Robinson Series 8.6 detector:
Using a special colloidal gold cocktail developed by SPI Supplies, we can demonstrate that the Series 8.6 detector easily resolves gold colloid as small as 5 nm. In the BSE image to the right, one can easily see 30 nm, 10 nm and 5 nm. On the same SEM and everything else being equal, we could not resolve the 5 nm gold in with any other make of BSE detector (we tried two others besides the Series 8.6 Robinson detector. We now offer the BSE test sample as a new product from SPI Supplies for our customers who need to validate that their systems are working at rated performance levels. It is also a great sample to use when evaluating competitive detectors. Find out yourself which detectors really will resolve 5 nm gold on your SEM.

For those working with not only tissue samples but other samples where areas to be covered and examined are far greater than that allowed by a 3 mm TEM grid, then this approach is the answer.

Backscattered electron imaging as a function of voltage:
One of the benefits of any BSE detector is the ability to study how the BSE image changes with applied voltage. Other detectors lose resolution at lower voltages but for those with a Robinson detector, the resolution maintains itself even down to 2.4KV.

Specifics of the Robinson BSE detector vs. other detectors:
We have already mentioned that there are fundamental and important differences between scintillator vs. solid state detectors. The specifications for the Robinson BSE detector are not only second to none but exceed those of any other currently manufactured scintillator based BSE detector. It does not matter if the comparison is being made against a YAG based scintillator or some other scintillator, we would challenge anyone to show that there is an alternative design that would be superior to the Robinson design.

We also would make a similar kind of statement relative to anyone's solid state detector. Of course, at short working distances, the differences will be much smaller, and at times, the two contrasting designs might even produce comparable results. But once the working distance starts to exceed 10 mm, and of course much work is indeed done at larger working distances, the Robinson design wins hands down.

We don't normally make such claims but we would be happy to run a demo sample on the latest model of the Robinson detector (Series 8) and you could see for yourself the difference.

Accessories:
One can order their Robinson BSE detector with several different options:
We recognize that there is a general awareness of the value of BSE detection on one's instrument and how such data greatly compliments secondary electron emission (normal SEM images) data as well as EDS data. But these above listed options are not so well known. Therefore if you are contemplating the purchase of a Robinson BSE detector, we suggest that you take the few additional minutes to read the content about these optional accessories and determine if one or more of these accessories might be appropriate for you and your own work. The most efficient time for their purchase is at the time of purchase of the basic Robinson BSE detector.

Sliding "O" ring vs." Bellows" Detector:
All Robinson BSE detectors are "retractable". The Model 8.6 is manually retractable only, and the standard configuration is of a "sliding 'o' ring" design. This design has been used in literally thousands of SEMs all over the world without problem. The design of the sliding "o" configuration has been quite acceptable in terms of protecting the integrity of the SEM, especially non-UHV systems. The sliding "o" ring approach has also worked quite well on hundreds of UHV systems including a large number of FESEMs. However, some customers remain unconvinced, and demand that the Robinson BSE detector be installed with the "bellows" design, sometimes referred to as a "bellows detector". This does in essence double the price of the detector but for some of our customers, this more expensive design gives them a greater peace of mind for their extremely expensive FESEM and ultra clean vacuum system.

But we do want to make certain it is understood that whether it is the standard detector (sliding "o" ring) or a bellows detector, it is a manual withdrawal system and it would not have a motorized retraction mechanism.

Motorized retraction option:
This option is available only for customers selecting the "bellows" detector design.

Joy Stick Control:
The Robinson Series 8.6 BSE Detector is controlled by an easy to manipulate "joy" stick control.

How do we move our interest to learn more and get a firm price?
Our customer base is usually just too busy taking data and writing reports to make time for visits of "sales people" or long luncheon dates.......our challenge is to present this information in an accurate and compact way, one that is easy to understand, and with all of the data needed for a prospective customer to make a decision. Please complete the Robinson BSE Detector Prospective Customer Questionnaire and you will hear back from us with not only our recommendations but also, a firm price should your instrument be enough different from the "norm" that price higher than our standard one would be required.

Attachments:
Now offered is a STEM attachment which permits the Robinson BSE detector to be operated in the STEM mode of a TEM. It can be operated in either bright field or dark field mode. The change-over is done mechanically by inserting the attachment while the chamber is opened to atmosphere. The device relies upon the energy of the electrons hitting the attachment and being backscattered into the highly sensitive Robinson BSE detector. The standard configuration is for the attachment to come ready to accept both standard 1/2" (12.5 mm) SEM mounts or a standard 3.05 mm diameter standard TEM grid. Different SEM mount geometries can be specified and generally without additional cost.

RobDetector image
RobDetector image
Delivery times:
Everything is made to order. Delivery times are five weeks for all products except for bellows detectors which are eight weeks.

Installation:
Sufficient information is provided for a customer, at least moderately knowledgeable about the operation of their SEM to be able to do the installation without problem. Some customers feel more comfortable seeking assistance from the vendor who normally provides service to their SEM. There are so many Robinson Backscattered Electron Detectors installed worldwide that virtually all such service engineers have had experience doing such installations.

Of course, the service department of SPI Supplies as well as that of the manufacturer, ETP-Semra Pty. would be available to provide further assistance.




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Thursday October 23, 2014
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