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Diatome Diamond Knives for Ultramicrotomy

October 1, 2020

Synthesis of large-area single-crystal diamond

September 21, 2020

Summer is over. Welcome to the new reality.

September 1, 2020



Diatome Diamond Knives for Ultramicrotomy

October 1, 2020

Ultramicrotomy is a well-recognized technique for cutting ultrathin sections of biological and materials research samples. The diamond knives are mounted in an ultramicrotome, a very precise cutting machine. Typical section thicknesses are 20-100nm. In some biological applications the section thickness may be in the micron range (for observing the sections in optical microscopes).

The sections are imaged in TEM’s (Transmission Electron Microscope), or in SEM’s (Scanning Electron Microscopes).

Besides generating ultrathin sections one can achieve an extremely smooth sample surface for SEM imaging, or even more demanding, in an AFM (Atomic Force Microscope).

Another cutting application in which our diamond knives are used is the sectioning process performed in the vacuum chamber of an SEM. A section is cut, the surface of the remaining sample surface is scanned by the electron beam, an image is taken, a section is cut again, etc. The technique is called Serial Block Face Scanning Electron Microscopy.

In the early days of Electron Microscopy (in the fifties of last century), researchers cut their samples with glass knives. Only soft materials could be cut, glass knives lasted for a few sections only.

The first diamond knives were manufactured by Prof. Fernández Morán in Venezuela. He realized that an ultramicrotomy knife needs to be a more durable cutting edge as the currently used glass knives.

When we started 1970 making diamond knives for ultramicrotomy, we came from the manufacturing of diamond tools for watch industry. We had to redesign the polishing machines, our polishing technique. It took us 5 years to have a production of knives ready. Over the years we further optimized the polishing and other processing technique involved. The cutting performance had to be adjusted to the needs in the different applications.

The preparation of a natural diamond for making a knife was laborious: A crystal was sawn, preground, mounted in a shank by sintering, the sintered knife machined into a slot, the diamond freed from the metal, the knife polished, tested, mounted in the boat.

About 10 years ago we were able to buy the first man-made single crystal diamonds ( lab grown diamonds ) of high quality. The crystal structure of these diamonds is more homogeneous andmade it easier for us to generate perfect cutting edges.

Our diamond knives are extremely sharp: in holographic studies the radius curvature was found to be 2-4nm (Proc. 3d Beijing Conference and Exhibition on Instrument Analysis, 1989). This was confirmed by AFM (T.R. Matzelle et al., Journal of Microscopy 2003).

The extreme sharpness and smoothness are needed for the entire cutting-edge length. The widest knives we make have cutting edge lengths of 10mm.

Ultramicrotomy in Biology

In Biology standard ultramicrotomy is done at room temperature. The knife trough is filled with distilled water. The water reaches the diamond knife edge, the sections slide on the water surface thanks to the high surface tension of water. The tissues and cells are embedded in an epoxy or acrylate resin.

A common problem in ultrathin sectioning is “compression”. The sections are shorter than the sample height. We were able to improve by reducing the knife angle from the classical 45° to 35°, later to 25° (for cryo sectioning).

We realized that reducing the knife angle leads to a shorter service time. Our R&D led to an oscillating knife (D. Studer et al., Journal of Microscopy 2000). With a piezo stack the knife is moved a few nm parallel with the cutting edge, resulting in sections without compression. In 2020 we introduced an improved version of this knife, the ultra sonic Maxi.

ultra-sonic-Maxi-300x188Nowadays biologists want to do 3D reconstructions of section series. Long section series need to be cut, mounted on substrates such as glass or silicon, imaged in SEM’s. It is found that our knives are very durable, many thousand sections can be cut on the same knife portion. Projects are running in different research labs for cutting through an entire mouse brain. It is obvious that for the sectioning of thousands or millions of sections the knives must be durable.

A more modern way of preparing biological samples for Electron Microscopy is cryo processing. Tissues and cells are cryo immobilized. The sectioning is done in the cryo chamber mounted on the ultramicrotome. The temperature is typically hold at -100°C (for sucrose infiltrated samples in immunocytochemistry), at -150°C (for frozen hydrated samples). For the dry cryo-sectioning we have optimized the knife surfaces for best section gliding.

A major problem in dry ultramicrotomy (room- and cryo temperatures) is electrostatic charging. After years of R&D we have introduced the first antistatic device in ultramicrotomy (M. Michel et al., Journal of Microscopy, 1990). Later this invention was further improved by adding a charging function for attaching ultrathin cryo sections to a TEM grid (J. Pierson et al., Journal of Structural Biology 2010).

For facilitating the handling of dry cryo sections, we developed the double manipulators (D. Studer et al., Journal of Structural Biology, 2014).

Ultramicrotomy in Materials Research:

The advantages of ultramicrotomy as compared to other preparation techniques: no beam damage (as for ion beam thinning, FIB), no smearing (as for polishing techniques). A great number of Materials Research sample types may be processed with diamond knives on an ultramicrotome.

  • Polymers for TEM, SEM or AFM imaging (both at room- and cryo temperatures).
  • Paper, wood, liquids, cosmetics, pharmaceuticals, etc.
  • Metals (except those who attack diamond chemically).

Brittle materials: ceramics, crystals, semiconductors, superconducting oxides, battery materials, etc, for TEM, SEM or AFM imaging.

For water or atmospherically sensitive materials (oxide forming metals, lithium, etc) the ultramicrotome is mounted in a vacuum chamber or in a glovebox with protective gas.

In fact most materials softer than diamond can be processed by ultramicrotomy.

The long years experience in developing and using diamond knives allows us to offer a unique sample testing service: researchers send us samples, we process them and report on our findings. This service is highly respected in the research community.

Helmut Gnaegi
Managing Director Diatome Ltd

The Diamond Academy Helmut Gnaegi

Helmut Gnaegi

Synthesis of large-area single-crystal diamond

September 21, 2020

Single-crystal diamond (SCD) features a unique combination of extreme material properties. They provide the base for a large range of applications in mechanics, optics and electronics. Recently diamond has also proven to be one of the most promising base materials for future nano and quantum technology. Many applications still lack form the availability of wafer-scale SCD.

Nowadays, two synthesis methods for SCD are established: (A) high-pressure high-temperature (HPHT) technique which mimics the natural formation process of diamond deep inside the earth and (B) chemical vapor deposition (CVD) which works far from thermodynamic equilibrium below ambient pressure. The following compares important characteristics of both synthesis methods for producing large-area SCD.

The majority of synthetic diamond for industrial applications is produced by HPHT. The grain size ranges from ~10 µm to rough stones of more than 50 ct weight. Despite such unique octahedral shaped stones, standard HPHT plate size is still below 10 mm. In addition, the occurrence of several growth sectors with different defect density can limit potential applications.

The CVD diamond process comprises a carbon-containing gas (e.g. CH4) diluted in hydrogen. In a reaction chamber a plasma is formed by activation of the gas phase, most commonly via microwave radiation. The diamond condenses layer-by-layer out of the gas-phase on a suitable substrate.

The established method called homoepitaxy uses a diamond substrate itself with typically (001)-orientation. It turned out that CVD growth on {100} crystal faces yields the lowest density in structural defects. Growth rates up to 150 µm/h on small areas (< 1 cm2) were reported using high gas pressure (up to 500 mbar) and high microwave discharge power densities. Up-scaling of such small and intense plasma discharges for the synthesis of large-area SCD is technologically not feasible. The introduction of 915 MHz microwave reactors with their higher wavelength as compared to the common 2.45 GHz systems facilitates an increase in the maximum size of the plasma discharge. Nowadays, SCD can be deposited fairly homogeneous on areas above 4 inch diameter with deposition rates of ~10 µm/h. Homoepitaxial diamond deposition can yield SCD of high quality and low dislocation density of below 103 cm-2. The lack of available seed substrates limits the plate sizes to below 1 inch diameter. Principally, diamond plates produced by overgrowth of tiled clones can overcome some size limitations (mosaic crystals of 40×20 mm2 were reported). However, the connection lines contain a high defect density and are detrimental for applications which require homogeneous SCD over large area.

Heteroepitaxy (i.e. the oriented growth of one crystalline material on the surface of another one) overcomes the size limitations of available diamond seed substrates. The company Augsburg Diamond Technology GmbH (audiatec) commercialized the first SCD crystals grown via this novel approach in 2015. The multilayer substrate iridium/yttria-stabilized zirconiumdioxide/silicon was developed by the founders of audiatec and is the key to SCD diamond wafers. The base material silicon shows a close fit with the thermal expansion coefficients of diamond which results in low thermal stress after cool-down from process temperature (~1000°C). The diamond nucleation on a single crystal iridium surface turns out to be unique in terms of the attainable diamond crystal quality compared to all other technologically relevant substrate materials. Finally, the thin oxide layer allows the integration of iridium on silicon. Freestanding SCD wafers with diameter up to 92 mm and 155 ct weight were deposited with this novel concept by audiatec.

audiatec sells SCD plates according to customer specifications (dimension, geometry,..) for different industrial applications. Recently, audiatec contributed the raw material for the world´s first wearable CVD lab-grown diamond ring, manufactured by Dutch Diamond Technologies.

Dr Stefan Gsell / Dr. Martin Fisher
CEO’s Audiatec

The Diamond Academy - Dr. Stefan Gsell

Dr. Stefan Gsell

The Diamond Academy - Dr. Martin Fisher

Dr. Martin Fisher

Summer is over. Welcome to the new reality.

September 1, 2020

From my own experience I have learned what it means to transform an ornamental diamond cutting company into a company that makes diamond products for the tech industry. In the nineties of the last century, we made the transition from Mined diamonds to Labgrown diamond in the same company. These were all steps that made the diamond product available for new applications and took the company to a new phase, and often to a higher level.

We have continued the experiences gained at DD Technologies. We are now a modern leading and innovative diamond company with a clear vision and mission. We would like to share our experiences and introduce you to new developments. Together with colleagues and partners we offer you access to more than 60 years of diamond experience.

That is why we founded The Diamond Academy. This will be a platform where certain topics are discussed and we let passionate people speak who are happy to inform you about their work. The Diamond Academy is a platform for and by scientists, developers, diamond users and manufacturers of diamond tools and instruments.

I would like to invite you to follow The Diamond Academy on our social media and our website.

The Diamond Academy - Dr. Ton Janssen

Dr. Ton Janssen,
CEO Dutch Diamond Technologies


As we’ve all noticed, the world has changed dramatically in 2020. What no one thought possible 6 months ago has suddenly become reality. Changes do not necessarily mean deterioration, but it does require a new perspective. You will have to think about how to deal with the new situation and find your chances again. That process requires an open and a creative mind. The diamond world has traditionally been a closed and conservative world. The supply of traditional diamond products has hardly changed in recent decades. For example, in the technical market diamonds are still mainly used for cutting tools despite various other applications. In the GEM market there is the tendency that millennials are hardly interested in diamond jewelry. The 2020 situation also seems to be causing an accelerated response here, with themes such as origin and sustainability playing an increasingly important role in making choices. If you add that to the rise of labgrown diamonds, you know that a moment has come when the diamond world has to reinvent itself. A new reality is emerging…

We have continued the experiences gained at DD Technologies. We are now a modern leading and innovative diamond company with a clear vision and mission. We would like to share our experiences and introduce you to new developments. That is why we founded The Diamond Academy. This will be a platform where certain topics are discussed and we let passionate people speak who are happy to inform you about their work.

I would like to invite you to follow The Diamond Academy on our social media.

The Diamond Academy - Dr. Ton Janssen

Dr. Ton Janssen,
CEO Dutch Diamond Technologies