Kính hiển vi điện tử quét độ phân giải siêu cao HITACHI SU9000II

The SU9000II is HITACHI's new premium SEM. It features unique electron optics, with the sample positioned inside a gap between the upper and lower parts of the objective lens pole piece. This so-called true in-lens concept - combined with the next generation of HITACHI's cold field emission technology - guarantees the highest possible system resolution (SE resolution 0.4 nm @ 30 kV, 0.7 nm @1.0 kV [with deceleration feature option]) and stability.

New coherent cold field emission source 

To make this resolving power usable in practical applications in your lab, the SU9000II utilizes an ultra-stable side-entry sample stage similar to high-end TEM systems and incorporates optimized vibration damping and a closed cabinet to shield the electron optics from environmental noise. Furthermore, the clean vacuum concept of the SU9000II offers a vacuum level in the gun and sample chamber that is one order of magnitude better than the previous generation, thereby minimizing sample contamination artifacts (effective pre-observation cleaning of the samples themselves can be achieved using Hitachi's ZONESEM sample cleaner).

Sample Cleaner ZONESEMⅡ 

To allow for stable data acquisition at the instrument‘s highest performance levels, the SU9000II offers new capabilities that render automated adjustments of the optical system—and the new EM Flow Creator software package as an option to render automated data acquisition, particularly sequential data collection.

Low-aberration in-lens objective lens

In-lens type objective lens has the advantage of reducing aberration by shortening the focal length. Reduced aberration can improve the resolution, allowing more stable observations for fine structures at the sub-10 nm scale or even below.
The figure on the left shows a backscattered-electron image of an ion-milled cross section of a PMOS transistor after cleaving.
The backscattered-electron signal clearly reveals information on the cross-sectional composition of the device, including the e-SiGe morphology.

Exploring new possibilities in LV STEM

Angle-selective Dark-Field STEM image

- BF/DF Duo-STEM detector(option) -

Lattice imaging by SEM/STEM

The SU9000II features a low-aberration in-lens objective lens and an optical system optimized for STEM observations. These features expand the range of available SEM/STEM observation techniques.
By controlling the convergence angle of the primary electron beam and generating interference fringes on the detection plane of transmitted electrons, lattice images can be observed in SEM/STEM.
The figure on the right shows a bright-field STEM image of pyrophyllite, revealing (020) plane lattice fringes with spacings of 0.445 nm.

Features

• The world's highest SE resolution of 0.4 nm at 30 kV is guaranteed.
• Usable magnification of up to 3,000,000x.
• Newly designed CFE GUN provides high brightness and an extremely stable emission current.
• Superior low kV performance for observing beam sensitive materials. The SE resolution of 0.7 nm even at 1.0 kV landing voltage (with deceleration feature option) is guaranteed.
• Newly capabilities that render automated adjustments of the optical system and an optional function that render automated data acquisition allow sequential data collection.
• Improved vacuum technology that allows for UHV levels for reduced sample contamination.
• Highly engineered instrument enclosure featuring both superior strength and stability to allow for high resolution imaging in a broad range of environmental conditions.
• Newly designed objective lens enables high resolution imaging at a low acceleration voltage.
• Side entry sample exchange system increases throughput by reducing the time required to change samples and automatically positioning the sample at the current WD.

In-lens SEM

S-900 launched with 1,000 units installed.
In 1986, Hitachi released the S-900, the world's first commercial in-lens FE-SEM. With 0.8 nm SE resolution and a usable magnification of up to 800.000x, the new concept of the S-900 truly opened up a new world for researchers in many fields.

The success story continued with the S-5000 (1990), S-5200 (2000) and S-5500 (2004), with each new model setting new standards.

In 2011 Hitachi celebrated 25 years of in-lens FE-SEM technology, and used that opportunity to introduce the new SU9000, the most powerful member in Hitachi's high-end FE-SEM product line-up.

LV-STEM

High-Resolution, Analytical STEM/SEM Providing Simultaneous Chemical and Bonding Analysis, Atomic Resolution, and Surface Imaging at 30kV and below

Investigating samples with the full capabilities of STEM at 30 keV and below is an extremely interesting and rapidly growing area of research: providing both Materials and Life Sciences with full SEM and STEM, inclusive EDX, and EELS capabilities, at low voltages. Less beam damage and higher contrast are the key arguments for the Low-Voltage STEM (LV-STEM), a capability that has been out of reach for researchers globally. With the LV-STEM, its low beam energy, increased contrast, and narrow energy spread, investigations of biological material in an unstained condition are becoming a reality for the first time.

Since the STEM unit has no imaging lens after the sample, electrons that were inelastically scattered by the sample do not really worsen image quality (they do for TEM). The significance of the lack of chromatic aberrations after the sample increases with decreasing electron energy; samples that typically would require a 100-keV TEM, at the very least, can be investigated with low-keV STEM. Multi-scattering processes and absorption of course still appear—ultimately limiting the acceptable thickness of the specimen. However, the use of high-end specimen preparation techniques, or working with thin samples as is typical in nano-research fields, allows 30-keV STEMs to cover much of the areas of conventional higher-keV TEMs, while at the same time, providing surface information through standard SEM methods, including SE, BSE, and high-angle BSE.

The well-established cold FEG of Hitachi’s high-end SEMs is a tremendous benefit for EELS capabilities as well as the point resolution of STEM. Despite the unusually low voltage for EELS and the increased impact of environmental conditions on low-voltage electrons, we are able to demonstrate better than 400-meV FWHM (full width half maximum, see Figure 1, left) for the ZLP (zero loss peak) of EELS, allowing clear and crisp EELS data for fine structure investigations. For example, eliciting the tiny changes in the π bonding for the Graphene as layer after layer is added demonstrates the sensitivity of the LV-STEM (see Figure 1, right). The LV-STEM also has a 2^nd dedicated EELS detector with 3 elements, allowing the rapid (10,000 fps) acquisition of energy-filtered BF STEM images, Plasmon images, or the rapid collection of elemental maps. Switching between both detectors is easy and relies on Hitachi’s own unique design.

The LV-STEM feature (Figure 2) complements SE imaging and makes no compromise. Typical images taken at 30 keV without a Cs corrector or Cc corrector approach 0.2-nm resolution establishing the LV-STEM as the true performance leader for ≤ 30 keV microscopy. The importance of simultaneously acquiring STEM and SE data is demonstrated in Figure 3.

As this microscope can handle samples up to 5.0 mm × 9.5 mm × 3.5 mm, the optional windowless EDX detector supports the analysis of both thin and bulk areas. At an incredible collection angle of 0.7 sr, acquisition times for EDX maps are short (see details in Figure 4), making the LV-STEM a truly ground-breaking microscope for both Materials and Life Sciences applications.

References

1. R.F. Egerton, “Electron Energy-Loss Spectroscopy in Electron Microscope”, Springer, New York
2. K. Suenaga et al., Nature, Vol.468 (2010), 1088-1090
3. G. Algara-Siller, O. Lehtinen, A. Turchanin and U. Kaiser, (2014). Appl. Phys. Lett., 104, 153115.
4. The authors wish to thank Dr. Tsuyohiko Fujigaya, Kyushu University for providing the samples.

Figure 1 Left: despite the low (± 30 keV) energy of these electrons, the energy spread of the electron beam, measured by our own Hitachi EELS is 400 meV or less:. Right: EELS spectra differentiating between single , double and triple layers of graphene , graphite, diamond, and amorphous carbon.

Figure 2 The low-pass-filtered BF STEM of Graphene at 30 keV shows a resolution of close to 0.2 nm; the 0.142 nm atom distances are not resolved.

Figure 3 Left: The high-resolution 30-keV BF STEM image by itself makes it difficult to model its 3D structure. Right: Only in combination with the (simultaneously acquired) high-resolution SE image, the real structure of this sample becomes obvious and modeling this structure as a 3D model would be quite manageable.