An Eye On the Small
For analytical studies at the atomic level, the JEOL ARM-200F, an aberration-corrected scanning transmission electron microscope, offers resolution of 0.08 nm. Image: JEOL
Practical nanotechnology R&D cannot take place without analytical instrumentation. Part of the reason nanotechnology has advanced so rapidly in the past two decades has been related progress in the tools used to image small features.
Many specialized tools are available to researchers who need to characterize sub-100-nm features. For nanoparticle sizing, there are diffraction scattering systems. For lithography, there are measuring microscopes. But three types of systems really stand out for general purpose R&D at the nanoscale and near-nanoscale: the atomic force microscope (AFM) and scanning probe microscope, confocal and Raman optical microscopes, and the electron microscope.
The first is a non-optical method that relies on mechanical deflection to map surfaces. The AFM is often combined with other measurement techniques, such as thermal detection or spectroscopy, to supply more information.
The electron microscope derives information from interactions between electrons in a high energy beam and sample atoms, which may be near the surface of a bulk specimen (a scanning electron microscope or SEM) or anywhere along the beam’s transmission path through a thin specimen (transmission electron microscope or TEM). Electron microscopes have also evolved, becoming generally smaller and less expensive at the low end (benchtop SEM), and both pricey and powerful (sub nanometer SEM and sub-Angstrom TEM resolution) at the high end.
Optical solutions are generally not available below 100 nm because of the diffraction limit of light, but advances in interferometric methods have allowed manufacturers to begin marketing their instruments as crucial support vehicles in the nano-research mission. Why? Ease-of-use, lack of sample prep, and cost all mean that these instruments are useful ways to identify targets of research interest without resorting to other means.
Demand is growing for these instruments in general. Cumulative annual growth rates in sales for AFMs, electron microscopes, and scanning probe microscopes have hovered at or above 10% for much of the past decade, and have rebounded strongly after the recent recession. As a result, vendors have invested heavily in giving these systems the attributes that create demand in R&D labs. R&D Magazine asked vendors of analytical instrumentation for nanotechnology where they were seeing these changes.
Landmark advances in nanotech
The most remarkable change in nanotechnology is how much research interest it has attracted over the last 15 years. Assisted by government support, this R&D now amounts to billions of dollars. While the public in general has yet to realize the economic benefits to match this investment, instrument manufacturers have stepped up to provide tools capable of studying samples at the nanoscale. In some sense, they are among the early benefactors of nanotechnology.
According to electron microscope manufacturer FEI Company, Hillsboro, Ore., the most significant advance in nanotechnology in recent years is the ability to repeatedly synthesize complex materials with near-nanometer precision, particularly in the electronics and data storage industries—is one area where the economic impact of nanotechnology has been realized.
JEOL USA, another major electron beam instrument vendor, has seen substantial advancements in materials. “Thin-film technology is going further and further, from basic coatings to solar film to battle corrosion resistance,” says Natasha Erdman, FE-SEM product specialist at JEOL, Peabody, Mass. “The other big push is anything that has to do with communications, such as waveguides, and quantum dots. Everybody is trying to make size-dependent quantum dots and focusing on controlling the periodic structure on the nanoscale.”
Park Systems of Santa Clara, Calif., a maker of scanning probe instruments and atomic force microscopes, has been impacted greatly by the discovery of carbon nanotubes (CNTs), nanoparticles, and the techniques to manufacture them. The application of these materials to practical processes requires the use of AFMs and contact probes capable of extremely fine resolution.
But even optical instruments have advanced to the point where they can support fine-scale study of nanomaterials that are well under the 100-nm threshold. WITec, Maryville, Tenn., which specializes in Raman confocal microscopy that has found successful use in fluorescence microscopy for bio-applications, points to the latest achievements in the field of nanotube and graphene research, particularly with regard to electronics, as being a major step forward.
Olympus America, the optics expert based in Center Valley, Pa., has begun to enter the nanoscale sphere with its laser scanning confocal instruments, seeing demand for information-rich optical tools for materials analysis.
Thermo Scientific, Waltham, Mass., which includes nanoscale analysis products among its large catalog of instrumentation, also reports on the impact of CNTs, particularly with regard to transistor development. The company also cites the discovery and commercialization of graphene, the possibility of DNA nanotubes for drug delivery, and biosensor development for biomedical diagnostics as major findings and key targets for successful development.
“Spatial resolution has significantly increased in products such as SEMs and confocal microscopes. Non-contact profilometers are also speeding up while improving the amount of usable data. Digital technologies continue to evolve allowing engineers to use tools in more effective ways,” says Sean Gasparovic, product sales director, Keyence America, Woodcliff Lake, N.J.
The competitive edge
As expected for a field that attracts so much research attention, the push to provide extraordinary capabilities, whether specialized or general, has been the driver for remarkable advances in a nanoscale imaging in the last 10 years. Here are a few of the standout features of the vendors we surveyed, and the some of the advances that made them possible:
The company’s recent AFM products feature “superior resolution in both closed and open loop operation,” says Monteith Heaton, vice president of marketing. This is a major practical advance for users because it removes the need to make a decision before sample: whether to use closed- or open-loop operation. The resolution and accuracy are now equivalent in either mode. Heaton also cites faster imaging results, more sensitive force measurement, ease-of-use, flexibility, open architecture software, and technical support as standout features.
These capabilities were aided by improved resolution from in-house designed LVDT sensors, automated laser and photodetector alignment with a single mouse click, and the industry’s smallest laser spot for support of small cantilevers providing >10X faster imaging speeds and sub-picoNewton force measurements.
|Asylum Research, Santa Barbara, Calif.|
|Atomic force microscopy
Scanning probe microscopy
|Topography at nanoscale
Magnetic, electrical, electrochemical, etc.
Sub-picoNewton force measurements
Metrology at nano- and micro-scale
Compositional analysis via thermal analysis with subzeptoliter resolution (10 nm lateral resolution)
Surface charge/Zeta potential
Martin says CRAIC’s products, such as its 20/20 Microspectrophotometer, stand out because they are the only systems on the market for microscopy and microspectroscopy in the UV, visible, and NIR regions. Ever-changing optical designs continually improve their performance.
|CRAIC Technologies, San Dimas, Calif.|
UV-visible-NIR microscope spectrophotometry
Pharmaceutical quality control
JEOL’s user base benefits most from advancements in flexibility and ease-of-use, says Natasha Erdmann, technologist. More and more microscope operators are not high-level researchers. Yet their work is important for product development and commercialization. Other advancements are technological, including aberration-correction optics for the SEM, which are increasingly becoming adopted, and improvements in the detector design. A key advance for JEOL’s products is the monochromator, which minimizes energy spread from an emission gun and improves resolution.
|JEOL, Peabody, Mass.|
|Scanning electron microscopy
Transmission electron microscopy
Scanning probe microscopy
X-ray photoelectron spectrometry
WD/ED combined electron probe microanalysis
Focused ion beam microscopy
Field emission auger microprobe
|Topography at nanoscale
Materials characterization and development
Quality control and forensics
Sean Gasparovic, product sales director at Keyence says the company offers “incredibly fast” results for both spatial resolution and angle detection when profiling. A 1-nm linear scale offer a distinct data profile, a 408-nm laser offers strong IR information, and a 14-bit photomultiplier is sensitive enough to provide a wide-range laser intensity. Instruments such as the VK-9700 are easy to use and handle a wide range of applications with little or no sample preparation.
|Keyence, Woodcliff Lake, N.J.|
|Laser scanning confocal microscopy||Imaging
Surface analysis--profiling, roughness
The optical laser scanning LEXT platform provides an approachable platform for studies to 0.08-micrometers. The advantage researchers have found in the platform, says Smith, is the wealth of information available via a confocal microscope in addition to capabilties designed into the system, including characterization of surface angles 85 degrees (ideal for MEMS study).
|Olympus, Center Valley, Pa.|
|Laser measuring microscopy
Confocal laser microscopy
|Materials and metallurgy
Pharmaceutical quality control
According to Park, a conventional AFM uses a piezoelectric tube for the x-y-z scanner, where x-y motion is induced by bending the tube. The bending motion, however, causes z position errors, thus introducing background curvature to the recorded data. Instead of piezoelectric tubes, AFMs from Park Systems use flexure scanners, which completely decouple the Z-scanner from the XY-scanner and replace bending motions with orthogonal ones. This type of Z-scanner allows the use of a true non-contact mode AFM operation, which minimizes the chance for sample damage and extends the lifetime of the AFM’s cantilever tip.
In addition the company’s ion conductance microscopy (ICM), a non-invasive in-liquid scanning probe technique that does not apply any force over its sample surface, has enabled the nanoscale imaging of single live cells and their soft membrane surfaces. This capability has been virtually impossible until recently. ICM can be further adapted to enable a host of powerful applications in nano-manipulated electrophysiology and cell motility studies.
|Park Systems, Santa Clara, Calif.|
|Atomic force microscopy
Scanning capacitance microscopy
Scanning tunnelling microscopy
Ion conductance microscopy
Magnetic force microscopy
Force modulation microscopy
Scanning thermal microscopy
|Topography at nanoscale
Conductivity, electrostatic force measurement
Lateral force measurement
FEI has a long track record for its charged particle optical systems. One of standout instrument lines is its Titan class of corrected TEM and STEMs that are capable of 0.5 ? (.05 nm) resolution and composition analysis, including differentiating among light elements. According to the company, its products bring atom-by-atom characterization and mapping to reality for the researchers. In addition, the company’s Osiris class tool provides analytic capability in real time, and their cryo-class tools for structural biology have enabled life science researchers to image proteins and viruses three-dimensionally with resolution better than 4 ? (.4 nm).
Scheinfein says its emphasis has been focused less on the already-proven mechanical and electrical properties of the electron microscope and more on providing customers with domain knowledge in the form of application-specific software so that data can be extracted from the measurements that is meaningful for their requirements. The company has imported domain knowledge through its tools offered to the electronics industry to deploy similar solutions for the life science and natural resource markets.
|FEI, Hillsboro, Ore.|
|Scanning electron microscopy
Transmission electron microscopy
Scanning transmission electron microscopy
Focus ion beam microscopy
Thermo Scientific’s line of X-ray photospectrometers (XPS) offer class-leading energy resolution, sensitivity, and spatial resolution for a variety research applications that require the sort of chemical information x-ray wavelength studies can provide. The company has spent a considerable amount of time in refining these instruments so that they are easy to use, rugged, and are flexible for use in many situations.
These advances have been made possible through cheaper computing speed and processing power, CCD camera developments, CNC machining, and rapid proto-typing/photolithography production methods.
|Thermo Scientific, Waltham, Mass.|
|Atomic foce microscopy
X-ray photoelectron spectroscopy
Micro-analysis, EDS, WDS
|Nm to µm scale depth measurement
Chemical coposition and characterization
The molar design of WITec systems allows users to combine confocal Raman imaging, atomic force microscopy and/or SNOM in one single instrument for a more comprehensive sample analysis. Switching between the different modes is done by rotating the microscope turret. An automated series for large samples and multi area/multi-point measurements is available. The atomic force microscope always comes with a research grade optical microscope for easy cantilever alignment and sample survey.
In confocal Raman imaging, WITec provides the most sensitive system allowing 3D Raman imaging. A Raman image consist of tens of thousands spectra. Due to the sensitive setup, the acquisition time for one spectrum can be as low as 0.7 ms; a complete Raman image is taken in a minute or even faster. For scanning near-field optical microscopy, WITec uses patented cantilver SNOM sensors, which outperform conventional fiber probes in terms of robustness, flexibility, ease-of-use, and transmission coefficient. Optical imaging with a lateral resolution down to 60 nm can be easily achieved.
|WITec Instruments Corp., Maryville, Tenn.|
|Research-grade optical/fluorescence microscopy
Near-field scanning optical microscopy
Confocal Raman imaging
Chemical 3D imaging and depth profiling
Optical imaging below the diffraction limit
Nanotech roadblocks, the vendor’s perspective
Industry experts and top nanotechnology researchers told R&D Magazine that the limiting factors to nanotechnology R&D are mainly cost, quality, and scalability. Park Systems points to the reliable and scalable manufacturing of nanomaterials as a main barrier for nanotechnology, while WITEC believes the process of translating nanotechnology research into real products has yet to come into its own. Thermo Scientific cites the need to understand toxicity properties to guarantee the healthfulness and safety of nanotechnology products.
FEI says the progress researchers have made in both studying and making nanoscale products is substantial, but the cost of doing so has kept many products stuck in the lab. “One of the major challenges,” says Mike Scheinfein, executive vice president, business development and CTO of FEI Company, “is to provide nanotechnology solutions that are cost competitive with consumer products already on the market. Nanotechnology provides abundant opportunity for synthesis and characterization. But these solutions are difficult to deploy at the price point that consumers require.”
Resolution isn’t the end-all, be-all for R&D, even for nanotechnology. “At its smallest scale, nanotechnology requires AFMs and SEMs because the scales are so small. But in practical applications, you need to do something that is larger and larger in scale. The applicability for a more practical optical microscope is large,” says Matt Smith, director of sales and marketing, Olympus America. Choosing the right tool can be a difficulty, and some researchers don’t realize they need a certain type of information until they get an instrument that can provide it.
Monteith Heaton, vice president of marketing, at scanning probe and AFM manufacturer Asylum Research, Santa Barbara, Calif., says the main roadblock is in “producing products reliably with consistent quality and that meet industrial needs.”
Confocal microscopes, like this WITec alpha 300 AR Plus, are limited by light diffraction to 200 nm resolution. But their ability to collect chemical data helps these instruments support nanotechnology applications. Image: WITec
Scalability and quality is an issue instrument vendors are increasingly sensitive to, and even companies focused on optics, such as Olympus, have become more focused on repeatability and quantitative results. Some vendors do see another factor at play: their own products.
“Tools are the biggest limitations,” says Gasparovic. “Nearly every time a customer acquires a new technology, the benefits are recognized and then, in an instant, the demand for more capability increases. Tool manufacturers must meet this demand.”
Finally, Paul Martin, chief executive officer of CRAIC Technologies, San Dimas, Calif., gives voice to the prediction that nanotechnology will likely not devolve into “just another materials science”, but will keep its diversity in not only materials but in the development of nanoscale technologies. This is an important distinction for instrument makers, as they stand to be key players in a world where nanotechnology is a primary driver for economic activity.
A feature-rich environment
In prior surveys conducted by R&D Magazine of microscope users, resolution—the most crucial performance metric—was typically at the top of desired features. Several vendors concurred that resolution is by necessity a crucial feature of microscopes used for nanoscale study. But even in the rarified air of nanotechnology instruments, resolution is by no means the only feature that has the potential to make or break an instrument for a certain application.
CRAIC, Keyence, and WITec identified flexibility, not resolution, is the most important feature in today’s nanotechnology instrumentation.
“Flexibility is critical. The highest-end tools are often extremely expensive and very narrow in scope. The ability for one tool to spot correlations in features such as visual appearance and quantitative information in one evaluation can lead to faster discoveries,” says Gasparovic.
Robert Hirche, managing director of WITEC’s U.S. operations, also believes the ability to perform multiple analyses is “the most important feature in measurement system, as only such a flexibility allows the comprehensive and multi-facetted inspection of the various properties (chemical, structural, etc.) of a sample.”
Scheinfein also cites flexibility as an important component of performance: “In the discovery phase of R&D, resolution and the ability to perform multiple functions is key because time and cost pressure, which are common in volume manufacturing phase, are typically not present or as critical.”
FEI lists speed and repeatability as important features for imaging solutions. Repeatability, or traceability, was the feature of importance for other vendors, too, including Park Systems and Olympus.
CRAIC’s Martin added that flexibility will remain a crucial feature into the future, saying analytical techniques of the future will almost certainly differ from those of today.
According to Erdman, any high-end SEM can claim about 1 nm resolution, sometimes lower, sometimes higher. The real important feature, she says, is ease-of-use. “Signal-to-noise ratio was once an important point of reference, but now it no longer has the same impact. It’s not what limits you,” she says.
Sample preparation is one of the key aspects of any work with instruments like a transmission electron microscope (TEM). Samples must be well prepared to be observed at the half-Angstrom range and JEOL has spent considerable effort in holding training classes that help its users get the most of JEOL’s instruments.
Quantitative information is becoming a priority for AFM, which is expected to map surface topography down to the nanometer scale. However, says Sung Park, vice president and general manager, Park Systems' U.S. operations, these instruments have traditionally struggled to provide accurate absolute dimensions of surface features. “As the dimensions found in research and industrial applications become smaller and smaller, it is now more important than ever for AFMs to measure the absolute dimensions of surface features with accuracy and repeatability.”
At Olympus, traceability is now a design goal. “One of the key items front and center is the need for traceability and repeatability of the measurement,” says Smith. “Olympus is moving more toward a quantitative space and we’re finding ways to allow customers to track what they are doing.”
Thermo Scientific pointed to one additional instrument feature that can’t be overlooked when designing nanoscale devices: chemical characterization. The company says it is an absolute requirement for ensuring structural and chemical functionality.
Instrument vendors join the nanotechnology product chain
Unlike some commodity-oriented products, analytical instrumentation, particularly that used for such a demanding area of research, cannot be hands-off on the part of the vendor. The concept of customer assistance is strong with manufacturers, and product refinements often result from their direct interaction with customers.
Any successful technology platform based on nanotechnology will require more than analytical instrumentation, however. It will need a manufacturing platform vetted for scalability, throughput, quality, and cost-effectiveness. Instrumentation vendors know this, and have tried to provide solutions that make sense to researchers who wish to do more than just solve theoretical problems.
The balance of cost and capability is one that is necessary to keep research moving forward. But nanotechnology, an immature field by anyone’s definition, is full of wild cards. The biggest one, perhaps, is scalability.
Published in R & D magazine: Vol. 52, No. 6, October, 2010