Since the commercialization of the scanning electron microscope in the mid-1960s, research, development and quality control in the areas of medical and physical sciences have flourished. The scanning electron microscope, or SEM, has allowed researchers to observe things unseen by either the eye or light microscope, and is a key piece of instrumentation in virtually all modern laboratories. Today, the cost of an upper echelon field emission scanning electron microscope, with accessories, is approaching $1 million. This can be out of range for most laboratories. Even a new, traditional type of scanning electron microscope can be too cost prohibitive for a start-up, small company, or department within a major corporation or university. Always in the back of any manager’s mind is the cost of ownership this piece of equipment will entail. In cases such as this, a pre-owned scanning electron microscope becomes a cost-effective possibility.
Before moving to purchase any SEM, new or used, the first couple of questions that must be answered are:
- Is it a requirement that the samples be viewed in their natural state?
- What is the minimum resolution needed to observe a particular feature of interest on the sample?
- How large a sample needs to be imaged?
Besides asking about your timing and budget, one of the first topics that any SEM technical sales engineer will ask about is your application. By knowing your particular application, the engineer should be able to intelligently refine your search to focus on a particular type of SEM. The choices essentially come down to emitter type and detectors used to collect the electrons as they are reflected back off the sample.
There are three basic types of emitters, or sources used for electron emission: field emission (FE), tungsten (W), and lanthanum hexaboride (LaB6). The three methods of detecting these electrons are a standard Everhart-Thornley (E-T) detector, an upper detector, or a backscattered electron (BSE) detector. Today, for high-end nanotechnology applications, such as viewing individual carbon nanotubes or advanced semiconductor devices, field emission SEMs with an upper detector are required, as shown in Figure 1. For traditional applications, a standard FE-SEM will suffice.
In addition, while tungsten or LaB6 SEMs may appear in Figure 1 to approach the resolution of the FE-SEMs, they need to view the sample at higher accelerating voltages, which means that samples must be coated with a thin metallic layer. Since FE-SEMs can image at very low accelerating voltages, the need to coat samples with a metallic layer is substantially reduced. To address the issue of having to coat samples for observation with a tungsten or LaB6 SEM, the use of a BSE detector, combined with control of vacuum pressure, allows these SEMs, known as variable pressure (VP) SEMs, to view samples in their natural state. However, it is at the expense of lower resolution. To address the additional resolution requirements, VP FE-SEMs have recently become available.
Generally speaking, various applications have different resolution requirements, and this reality prompts the need to consider SEM type. The resolution a scanning electron microscope can provide at low-accelerating voltages is the major determinant of its selling price.
Purchase prices for scanning electron microscopes are primarily dictated by resolution. Other factors that determine the price are automation, chamber size, and optional SEM accessories, such as an elemental dispersive spectroscopy (EDS) system.
Figure 2 depicts how the price of FE-SEMs is related to resolution. As seen, the closer the SEM gets to 1 nanometer in resolution, the higher the price. Also, the price difference between new and used SEMs can approach 50 percent or more, depending on the circumstances. Such circumstances may include the seller’s urgency to move the SEM as quickly as possible and the age of the SEM. Typically though, if one is involved in a quick sale purchase, chances of running a representative sample or seeing the machine in a working state of operation is low. So the buyer must beware.
It should also be noted in Figure 2 that at the 3-nanometer resolution mark, SEM manufacturers introduced the upper detector, which has been the driving force for increased resolution right down to the 1-nanometer regime. Without an upper detector, a FE-SEM’s standard detector would not be able to resolve features below 4 nanometers. An upper detector is a factor in system pricing as the 1 nanometer mark is approached.
A recent SEM purchase
Earlier this year, the Nanometer Structure Consortium at Lund University in Sweden purchased a pre-owned Zeiss/LEO 1560 FE-SEM (shown in Figure 3). Before Lund University inspected the tool in the United States, samples were sent in advance and images were returned for initial review. After that, the local Zeiss customer service organization in the U.S. was contracted to perform an agreed-upon checklist procedure to note anything that might be problematic. The Zeiss service report (with comments) was sent to Lund University, and upon review of the report, Anders Kvennefors, a research engineer representing Lund University, made the trip to the U.S. to personally inspect the system before the final purchase.
According to Kvennefors, “Going through this procedure was our way of ensuring the system was going to meet our expectations and that we would not encounter any surprises upon its arrival.” In addition, Kvennefors notes, “SEMTech Solutions provided our nanotechnology facility with a nice, reconditioned SEM. It was a smooth transaction [with regards to all phases of the transaction: demonstration, shipping logistics, and installation]. The field emission resolution of this tool advanced our capabilities at a fraction of the cost of new equipment.”
Adding to this point, Mark Reynolds, CEO of SEMTech Solutions, explains: “The sale of this system is a win-win-win for all parties involved. Lund University wins by purchasing an excellent SEM at a great price, SEMTech Solutions wins by having sold such a quality system, and Zeiss’ customer service team in Sweden wins by gaining a new customer. It was a true partnership and collaborative effort by all three parties.”
Tips on buying a used SEM
Purchasing a used scanning electron microscope is a large investment that cannot be taken lightly, especially by a start-up or small company where cash flow can make or break a business. There are several factors to be wary of when looking for used equipment. First and foremost, consider the applications at hand. Have good knowledge of your required resolution and maximum sample size. Second, the SEM should be inspected personally to make certain it will perform well for your applications. Just because a machine is new or appears new does not mean it will work better. In addition, make sure that spare parts are available from either the original equipment manufacturer (OEM) or seller. Finally, inquire about potential upgrades that may be required for your applications in the future, such as EDS or BSE detectors, infrared chamber scopes, etc.
Furthermore, when buying a used SEM, cost of ownership should be factored in, to assess variables such as maintenance, associated running costs, and consumables. In addition, leasing, as opposed to an outright purchase, should be considered as well. The overall benefit of using a cost-of-ownership model is that it involves recognizing the lifetime costs of acquiring an asset, rather than simply focusing on the initial purchase price. Five years’ worth of reasonable equipment maintenance should be included as the basis for a cost-of-ownership model.
Things to consider
1. Know who you are buying from
- Is the business or seller you are dealing with well known, and do they maintain a good reputation?
- Can the seller demonstrate the SEM with your particular samples?
- Does the seller possess industry knowledge and have good references in terms of both sales and service capability?
- Can the seller or OEM provide a warranty?
- Can the seller or OEM provide parts?
- Is the seller willing to consider leasing the equipment to you?
- Can the seller train your staff on-site after the SEM has been installed?
- What are the payment terms?
2. Inspection of equipment
- Inspect the equipment before purchasing it. If you are outside the country and cannot personally inspect the SEM, find a reputable local technician in the area to inspect the machine for you. This can be fairly inexpensive and very beneficial. In most cases, a technician can find issues that you may miss.
- What additional options are available that you have future interest in?
- Can the seller or OEM provide these options before system inspection or on your site, and at what price?
- What type of documentation is provided with the equipment?
3. Shipping and installation
- Although you may be paying for these services, ask the seller to assist in coordinating the trucking and rigging of your SEM, if necessary. In the long run, it can save you time, money, and headaches.
- Make sure that all equipment is insured for loss during the transportation/ rigging process.
- Is there building work required in advance to support the installation of the SEM? Does your preferred location have:
- Adequate room size to accommodate the SEM and its accessories
- A quiet room that is low in acoustical emission
- A room with minimal floor vibrations
- EMI at a level that will not affect the imaging
- Facility issues, such as N2 gas for venting, water for cooling when necessary, compressed dry air, electrical hookups, etc.
Making a choice
No matter what avenue you choose to explore when adding pre-owned equipment to your laboratory, the benefits remain the same: the machine you want is ready for shipment, the delivery time is short, the equipment is reliable, and the cost is significantly less than the price of brandnew equipment. Taking the time to investigate which system is right for you will go a long way toward ensuring that your purchase stands the test of time in your laboratory.