A Look at Technology in 2022 – Nanomaterials, MEMS/NEMS, Metamaterials

As 2022 begins, predicting (guessing) where technology will go is almost always wrong.  This is an opportunity to highlight some of the developments that that appear possible to occur.

Nanomaterials:

Nanomaterials have been around for more than a couple of decades.  The initial examples of nanomaterial applications were in commercial products that increased the strength of material while decreasing the weight.  Carbon Nano Tubes (CNTs) were incorporated in Toyota bumpers replacing steel with better performance and less weight.  Zyvex Technologies provided material that was employed to make lighter and stronger tennis rackets among other sports equipment. 

Now research is moving into the realm where there are surprising findings.  A Northwestern professor [Ref. 1] was working on superconducting materials.  The researcher found a material, which is 4 atoms thick, that permits examining in only two dimensions the motion of charged particles.  Existing research on materials can examine particle movement in three dimensions, but not in two.  Future work will be directed at examining possible materials for energy storage.

The ability to design new materials has been inhibited due to the inability of existing laboratory equipment to create conditions required for the formation of the new material.  As the techniques are developed and the equipment becomes available, there should be significant advances in discoveries of the capabilities of new materials.

MEMS/NEMS:

Micro Electro Mechanical Systems (MEMS) are miniaturized systems that can preform at the micro scale the same way typical gears, sensors, transducers, analog clocks work.  The need to shrink the size of a product or function within a product.  Examples of MEMS in today’s world include the airbag deployment sensor in vehicles (accelerometers), devices that detect a person falling, orientation (portrait or landscape) of a smart phone, miniaturized sensors that can be swallowed, and many more.

The process for making the MEMS devices is in many ways similar to semiconductor processing.  The process deviates from the typical semiconductor process in that some of the portions of the device is actually etched away to create the sensitivity/function required by the end product. 

Nano Electro Mechanical Systems (NEMS) is not a term that might be familiar to the general public.  It is similar in function to MEMS but has different properties due to the interactions at the nano scale.  One example [Ref. 2] is from the University of Florida where they have demonstrated efficient mechanical signal amplification using nanoscale mechanical resonators.  They have created “drumheads of thickness from under 1nm to just under 8nm stretched over a 1.8micrometer void.  NEMS resonators will involves some portion of the device that is no more than a few nanometers thick.

Metamaterials:

A metamaterial is a material designed to exhibit specific properties that are not found in naturally occurring materials.   These materials can affect different kinds of waves, i.e., light, electromagnetic radiation, sound.  The key item is that the metamaterials are formulated in repetitive patterns, which patterns are smaller than the wavelength of the wave to be impacted.  Efforts on the index of refraction of lenses are working to create a negative index for specific wavelengths. Reference 3 is an overview of metamaterials at a very high level.  More detailed information is available through internet searches.  

Thoughts:

Research and the equipment needed to develop new materials and material structures are becoming available.  The access to new types of equipment will provide interesting developments at the very small scale of nano and sub-nano.

References:

  1. https://scitechdaily.com/unplanned-discovery-a-super-material-for-batteries-and-other-energy-conversion-devices/
  2. https://phys.org/news/2021-10-highest-amplification-tiny-nanoscale-devices.html
  3. https://www.azom.com/article.aspx?ArticleID=21097  

Posted in Misc Ramblings, Science

Ultra-pure material

We already reported on the development of two-dimensional nano-sheet transistors and other two-dimensional materials.  One of the challenges that has been previously mentioned is the fact that we do not know the material properties of “pure” materials.  Current technology provides the ability to achieve purities within a range of parts per million.  In the percentage parlance that is 99.9999% pure material.  It is expensive and needed.  Doping silicon wafers with specific impurities can change the bandgap (conductivity increase or decrease) of the resultant material to enable the desired structure flow of electrons.  While the percentage of material purity Sound excellent, there is another way of looking at the analysis. 

Reference 1 refers to an analysis by Flavio Matsumoto on the number of osmium atoms in a cubic centimeter.  He performs the calculation tow different ways and the answers are close.  Both result in 7 x 1022 atoms, with a fractional difference.  Depending on the specific element, the number will vary.  If the material (osmium in this example) is 99.9999999% pure, there will be 7 x 1013 non osmium atoms in the cubic centimeter.  If one then reduces the size in question to one micron cubed, there will be 7 non osmium atoms present.  What happens when materials get near being without impurities?   

Princeton researchers [Ref. 2] have created a sample of gallium arsenide with impurities of one atom in ten billion.  The size of the material was 5 or 6 millimeters cubed.  To test the material, the cooled it to temperatures equivalent to space and inserted the material in a strong magnetic field.  They were interested in observing the changes in the electron flow.  They were surprised in that they found that many of the advanced physics phenomena were able to be observed at weaker magnetic fields.  From the data, it appears that the resultant effects could be observed at two orders of magnitude less than fields required to observe the phenomena in less pure materials. 

Our current technology permits us to make changes in the electrical conductivity of materials by adding a small amount of specific impurities (doping).  It is also known that adding impurities changes the structural lattice to advance or retard the ability of electrons to move within the lattice.  Since the lattice structure is changed, the question that remains is what happens to various other properties of the material.  In order to address that question, various quantities of absolutely pure material need to be created.  The raises the challenge on developing the processes for removing the impurities for the current methods of obtaining the current “high purity” materials.

This is a non-trivial problem.  Graphene has been manufactured for 20 plus years.  There is still a challenge to obtain a large area of graphene without structural defects.  Impurities can create those structural defects.  The work being done on two-dimensions transistors, which can accommodate some defects, has not developed a process that can be employed to create the billions of transistors required for one microprocessor chip.

The new year, 2022, should provide some interesting developments that further our understanding of pure materials.

References:

  1. https://www.quora.com/How-many-atoms-of-osmium-are-there-in-one-cubic-centimeter-I-honestly-cant-find-any-internet-help-whatsoever
  2. https://phys.org/news/2021-11-ultra-pure-semiconductor-frontier-electrons.html

Posted in Science

Experiments & Results

Previously, we have covered the challenges of experiments and the need for reproducibility.  Recently, there has been an additional occurrence that merits discussion.  There has been a study where roughly 100 peer reviewed articles that were published in respectable journals that had sufficient details on the experiments for the results to be validated by other researchers.  In that evaluation, 87 of the published results were unable to be verified by researchers.  In some cases, even the original researcher was unable to obtain results that could be considered within the experimental error.  If this is a problem, what about all the research that is published which does not include enough information to be able to independently validate the initial results.  How can these efforts be considered valid?  That is not a question that will be answered in this blog.

In previous blogs, I have mentioned the use of equipment that might have the same model number as a published experiment.  The fact that the model number indicates the equipment is similar, it may not be identical.  In the particular instance that was observed.  Two researchers locate hundreds of miles apart ran experiments of a nanomaterial. Each had samples of the material from the same lot produced by a reputable manufacturer.  They ran a predetermined process, used similar test procedures and recently calibrated equipment. But, they obtained different results.  They exchanged material samples and each duplicate their original results on the new, to them, material, which differed from their colleague’s results.  The question was what was happening.  It took a lot of work, but they finally found the source of the problem.  In the course of a routine maintenance along with the required calibration, some of the worn parts were replaced by factory “originals”.  One of the “original” parts had gone through a redesign to make a stirring process more efficient.  It worked and was more efficient, but that meant the duration of the process created a different distribution of particle size than the equipment with the original unchanged part.  So, checking just model numbers and type may not be sufficient. 

Another example involved a supplier and a researcher.  There was certification of the properties of material by the supplier, which was retested by the researchers.  The material was shipped via standard commercial transport.  The research tested the material and found different results.  A reshipment of another batch of the certified material was shipped, and the researcher found a difference from the supplier’s certification.  After a number of conversations and equipment checks, it was determined there was an external cause.  The determination revealed that the material, which had been certified, acquired enough oxygen on the surface of the material to change the characteristics of the nanomaterials.  This is an important point to remember with nanomaterials.

While this seemed to cover the possible causes of deflection of results in experiments, a new one was found.  While not involving normal experimental equipment, this one involves a standard, commercial over the range microwave that contains two small lights in its bottom surface.  One bulb failed.  The solution is simple, look at the manual, which identifies the bulb by part number, and order one.  Well, simpler said than done.  The bulb, in this case a 40W bulb, is no longer available.  There is a manufacturer approved 50W specified as a replacement.  Fine, order the bulb and installed when it was received.  The illumination was considerably better than the original bulb next to it.  Over the weeks, noticed that the bottom of the microwave was warm to the touch.  When the second bulb failed, searched for a lower wattage bulb.  There was a 35W bulb, but it was not available.  Decision was made to try to find information on the existing bulb.  It turns out there was some very small marking on the second bulb, which itself is not large.  It was possible to make out a 20W marking.  Two 20W bulbs were ordered and installed upon receipt.  The resulting illumination was of the same level as the original bulbs.  The instructions and part identification in the manufacturer’s manual were wrong!  So someone following the instructions per the manufacturer’s manual would be replacing incorrect parts. 

The point of these examples is that in performing research, no assumption should be made without verification of the equipment, materials, and processes being employed.  Even manufacturer supplied directions/instructions may be in error.

Posted in Misc Ramblings, Science

Interesting Times due to Interesting Discoveries

In previous blogs, two dimensional semiconductors have been discussed.  Work at Singapore University of Technology and Design has developed a different approach to solving the issues of very small transistors that will be required for future generations of semiconductors [Ref. 1].  Their work demonstrated that the 2D semiconductors using MoSi2N4 and WSi2N4 form Ohmic contacts with titanium, scandium and nickel.  These structures are free from Fermi Level Pinning (FLP), which is present in other 2D semiconductors.  Their approach to minimize the FLP requires a precise positioning of the metal on top of the semiconductor, which employs the 2D metal as contact material.  Their material is shielded due to the formation of an inert Si-N layer shielding the semiconductor layer from defects and material interactions at the contact interface.  They are planning to employ computer evaluations of similar materials to determine other potential materials.

Work is continuing to find improved material for Chemical energy, which could provide storage via chemical energy that can be converted into mechanical energy.  Chemical energy is a term for the energy stored in covalent bonds holding atoms together in molecules.  Work accomplished at the University of Buffalo, University of Maryland and Army Research Labs evaluated the potential of combining energic materials with ferroelectrics to create a high power density energy source that would be chemically driven.  The reported results are that two dissimilar materials (molecular energetic materials and ferroelectrics) can be combined to obtain chemically created electrical energy with a specific power of 1.8kW/kg.  Employing a polarization of molecular energetic ferroelectrics can provide control of both the energy density and the rate of energy release.

Work at Northwestern University and Argonne National Labs has developed a material that is four atoms thick and allows the evaluation of charged particle motion in only two dimensions [Ref. 3].   The target material was a combination of silver, potassium, and selenium.  Heating this material to over 450F, it became a relatively symmetrical layered structure.  Before the heating, the silver ions were fixed within the two dimensional material.  After the transition due to heating, the silver atoms had small movement.  This discovery has the potential to provide a platform for the evaluation of materials that could be constructed to have both high ionic conductivity and low thermal conductivity.  One of the potential outcomes is the ability to develop membranes that could provide environmental clean including desalting of water. 

A team of researchers at the University of Florida and Florida Institute of Technology have produced a high-efficiency mechanical signal amplification in nanoscale resonators operating at radio frequencies [Ref. 4].  The researchers observed parametric amplification in nanoscale devices.  The device contains a nanoscale drumhead mechanical amplifier consisted of a two dimensions semiconducting  molybdenum disulfide membrane with drum head thickness of 0.7, 2.8, and 7.7 nanometers.  The drum head was 1.8 microns in diameter with a volume of 0.020 m3.  The drum head was fabricated by transferring nanosheet exfoliated from bulk crystals over microcavities to make the thin nanodrums.  Amplification gains of up to 3600 were obtained.  This process can be employed in developing nanoscale sensors and actuators. 

What we are witnessing is the development of new materials that have been able to be developed due to the ongoing research in nanotechnology and the resultant development of tools for analysis of the various materials. 

References:

  1. https://scitechdaily.com/newly-discovered-family-of-2d-semiconductors-enables-more-energy-efficient-electronic-devices/
  2.  https://www.nanowerk.com/spotlight/spotid=58913.php
  3.   https://scitechdaily.com/unplanned-discovery-a-super-material-for-batteries-and-other-energy-conversion-devices/
  4. https://phys.org/news/2021-10-highest-amplification-tiny-nanoscale-devices.html

Posted in Misc Ramblings

Evolving nano developments

With the emphasis on nanotechnologies and the emphasis on two-dimensional materials, other areas that are pushing boundaries are often overlooked.  A recent article [Ref. 1] summarizes work done at King’s College London on relieving pain.  Their treatment employs a ultra-low frequency neuromodulation to safely relieve chronic pain.  Neuromodulation employs electrical current to block transmission of pain signals between neurons.  The procedure normally requires implanting a device and sending signals.  Spinal cord stimulation is one example of this procedure.  Unfortunately, the success of that process has been less than desired.  This new method, employs a type of ultralow frequency biphasic current with a period of 10 seconds.  The process mimics the direct current applications, which can cause tissue damage and electrode degradation.  Due to the nature of the alternating polarity there is the potential for much reduced tissue damage.  Work is continuing in the area.  For further information the Wolfson Centre for Age-Related Diseases [Ref. 2] has additional information regarding their ongoing work.

A team of Chinese researchers has developed an interesting “twist” to graphene [Ref. 3].  By placing a second layer of graphene over the first and creating a slight misalignment, they created a Moire superlattice.  As the angle approaches 108 degrees, the material begins to show properties that imply low temperature superconductivity.  The result is that the kinetic energy of the electrons is suppressed and form localized accumulations at points where the two sheets interact.  There are additional effects that include correlated insulator states.   This is important because integrated photonics require nanolasers.  (Data transmission on a chip can travel at the speed of light.)  The work to produce these nanolasers has focused on a number of approaches, but the material properties for th4ese approaches has not been developed at the nano scale required for inclusion on semiconductor devices.  The referenced paper provides specifics on the low power required for lasing.  The researchers indicate their opinion that this development has the potential to impact many fields including “nonlinear optics and cavity quantum electrodynamics at the nanoscale.” [Ref. 4]

Researchers from Rice University and Northwestern University created a stable sheet of double layered borophene [Ref. 5].  This is a material structure is similar to graphene (Carbon sheets).  The atomic number of Boron is 4.  Carbon is 6.  Research is indicating that the borophene has electrical and mechanical properties that could rival graphene.  The difference is that the borophene is much more challenging to create.  The researchers succeeded in growing the material on a metal substrate.  Boron, when attempts to create the double sheet structure, tends to revert to its three dimensional structure.  The researchers think that the borophene structure could produce a much greater type of structures than graphene.  One projection is the potential for inserting a layer of lithium to create a superior two dimensional battery. 

As always, these developments don’t happen over night.  The work on borophene has taken over 6 years.  This will be followed by experimentation to develop a reasonable means of creating the materials. Only after that is available can products be produced that will appear in the public arena.

References:

  1. https://physicsworld.com/a/ultralow-frequency-neuromodulation-safely-relieves-chronic-pain/
  2. https://www.kcl.ac.uk/neuroscience/about/departments/card
  3. https://physicsworld.com/a/moire-superlattice-makes-magic-angle-laser/
  4. https://www.nature.com/articles/s41565-021-00956-7
  5. https://physicsworld.com/a/double-layered-borophene-is-created-at-long-last/

Posted in Nanotechnology

More on Semiconductors

Last month, this blog covered some of the challenges of continually shrinking semiconductor geometries and the related difficulties with traditional transistor designs.  This month’s blog explores transistor geometry.  In May 2021, IBM announced a 2nm nanosheet semiconductor technology. [Ref. 1]  Their claim is that this configuration will improve performance while consuming only 45& the energy as the current generation of chips. 

The nanosheet technology is one where the transistors are constructed from three horizontal sheets of silicon with the gate material surrounding the silicon.    The nanosheet technology is projected to replace the existing FinFet technology, which is approaching the limits where is can function properly due to material characteristic limitations.  The transistor configuration has developed through various shape configurations, but the materials have remained the same. [Ref. 2]  The transistor employed in microprocessors consist of a gate stack, a channel region, a source electrode, and the drain electrode.  The latter three are all based on silicon but have different doping atoms (impurity atoms introduced during processing to create the desired electrical properties).  The gate stack consists of a gate electrode on a layer of dielectric material.  The dielectric material is employed to ensure that the electrons flow when appropriately charged and not subject to random leakage of electrons. 

When the size shrinkage became too small to prevent current leakage, today’s FinFET transistor was invented and introduced into production in 2011.  With current production at the 7nm node and moving to the 5nm, Samsung has stated the FinFET design has run out of capability at 3nm.  A new design needs to be developed.  The new design is the nanosheet, although there are a few other names, like GAA (gate-all-around).  The picture below (from Ref. 2) depicts the design evolution of transistors.  The nanosheet design was announced by IBM for the 2nm node (Intel is call the node the 20 Angstrom node).

The introduction of a change in design will provide a number of challenges that manufacturing needs to overcome.  Since there is similarity between the nanosheet and the Fin FET, some of the process learning can be accelerated.   There are innovations required.  [Ref. 3]  The first is the need for epitaxially grown multilayers of Si and SiGe to define the channel.    Next, the nanosheet design requires an inner spacer, which is additional dielectric material for source/drain isolation.  Third is the separation of nanosheets from each other, which requires a very selective etch process.   Finally, there is the deposition and patterning of metal around and in between the nanosheet layers.  As mentioned earlier, this design enhancement is anticipated to reduce power usage by 45%. 

What happens when nanosheet runs it course?  There are designs being considered called forksheet.  [Ref. 3]  The challenges are numerous and also include a concern about electrostatic discharge.  Also, under consideration is something called a CFET or complementary FET.  This design employs vertically stacked nMOS and pMOS. 

Consequently, changes are coming to semiconductors.  The devices will become smaller, more powerful, and use less energy.  The manufacture of the devices will push the existing limits of current manufacturing and require the invention of new techniques and new equipment.  It will be very interesting to observe the changes in devices as semiconductors move to smaller and smaller node and start reducing power required.  Good things are coming.

References:

  1. https://spectrum.ieee.org/ibm-introduces-the-worlds-first-2nm-node-chip
  2. https://spectrum.ieee.org/the-nanosheet-transistor-is-the-next-and-maybe-last-step-in-moores-law
  3. https://www.eetimes.com/entering-the-nanosheet-transistor-era/#

Posted in Semiconductor Technology

The Shrinking Dimensions

As semiconductor manufacturing continues the dimensional shrinking process, novel ideas are required to achieve the ability to continue shrinking the dimensions while increasing the performance.  There are some thoughts that this potion of the Moore’s law curve will provide some additional benefits.

As the industry moves into the sub 10 nanometer nodes, physical properties become major role players in what will be able to be manufactured in volume *with sufficient yields) and what won’t work.  Intel has released its roadmap [Ref. 1] for the smaller dimensions and is moving away from the nanometer scale.  After the 3nm node, it will not be the 2nm node. Instead, it will be the 20 Angstrom node. That will be followed by the 18 Angstrom node.  [An Angstrom is 10-9 meters or a tenth of a nanometer.  It is not a new term. Angstroms were used in optics for hundreds of years.].

While the size terminology is interesting, it is the actual physical propertied and the manufacturing of the completed devices that are the objective. 

Filed Effect Transistors [FETs], and specifically MOSFETs manage current flow by controlling current flow.  The gate electrode and the channel are two plates of a capacitor.  Unfortunately, the gate capacitance depends on the material properties at the dimensions required.  The loss of the needed parameters as size shrinks is driving the investigation to what are being called two-dimensional semiconductors. [Ref. 2] More detail on this topic is available in our April 2021 blog. [Ref. 3]

In the article with Intel’s planned roadmap, there is mention that starting at 20A, Intel is considering changing to a “gate all-around” structure [GAA].  The Intel approach is somewhat different from others working on GAA and their modification is being called the ribbonFET.  [Ref. 1]

Another topic of current interest is “chiplets”.  [Ref. 4] The concept behind this is to create individual segments for a system and be able to place them in positions that are favorable to data transfer and processing.  This approach is a means of reducing costs while achieve apparent scaling benefits.  On a larger scale there are many companies working on various approached to reduce dimensions by using multiple levels (this is not multiple layers) with interconnections to complete the system interconnections.  I know of one sensor system that has multiple levels for a complete autonomous sensor system with capabilities of working in temperatures of over 120C and over 10K PSI.  It has sensors and can store data for up to a week before being wirelessly interrogated for data transmission.  This device is under 8mm in diameter.  It will be shrunk to under 5mm in the near future but taking it to under 1,000 microns would be a challenge without moving to something like the chiplet approach.

While the topic of semiconductors is mainly about shrinking feature sizes and increasing processing capability, the real changes will come from nanomaterial characteristics.  The fact that today, researchers are developing a method to layer different 2-dimensional materials together indicates the direction.  For this to be successful, the method to develop large scale 2-D material without defects still remains a challenge.  It will happen, but will require development efforts.

References:

  1. https://www.eetimes.com/intel-charts-manufacturing-course-to-2025/#
  2. https://semiengineering.com/thinner-channels-with-2d-semiconductors/
  3. http://www.nano-blog.com/?m=202104
  4. https://semiengineering.com/piecing-together-chiplets/?cmid=291477a6-f062-4738-b59f-1ec44fd21e39

Posted in Misc Ramblings, Nanotechnology

More on Cement and other Nano

Just prior to the end of June, there were two articles on cement/concrete.  “How to Make a ‘Smarter’ Cement” [Ref. 1] covers reports from Northwestern University’s team that introduced nanoparticles into ordinary cement.  They investigated two types of nanoparticles and the impact on fracture toughness.  The material employed was graphene in both the shape of rolled tubes (carbon nanotubes) and also as flakes.  Incorporating small amounts of nanomaterial improved the bonding due to tightening the pore structure, which reduced the air voids.  It was pointed out that this structure was replicating nature.  They chose to replicate the multilevel structure with the nanoparticles and the cement.

The second article [Ref. 2] address the variety of application.  This BBC report covers the vast array of cement that is being employed around the world.  The article is interesting in the fact that it includes a vast array of structures both modern and ancient.  The Pantheon in Rome was built in the second century AD and is still the world’s largest unreinforced concrete dome.  This structure’s existence  implies that Roman Cement was superior to what we are currently using in present day construction.  (cf. last month’s blog)

There is more material in published reports on the need for 2D semiconductors.  This is especially true as the dimensional for the 3nm and 2nm semiconductor nodes are investigated.   Reference 3 is one of many such articles.  As the dimensions of the transistor decrease, there needs to be a corresponding reduction in thickness.  Control of the electron flow is critical.  Nanosheets and nanowires are being considered along with the gate-all-around transistor.  The issues arise at the 3nm scale with trapped imperfections in the materials.  2D material appears to provide a possible solution.

From my viewpoint, the issue with 2D material is the production of large quantities of defect free material.  There are various materials being investigated with transition metal dichalcogenides (MoS2, WS2, and WSe2 are most commonly proposed).  The materials of choice are flakes of material exfoliated from bulk material.  (Might bring back some memories of the early carbon nanotube work.)  Atomic Layer Deposition (ALD) can provide think layers but there are residues left behind by the process that can contaminate the desired material.  There is a lot of research being conducted, but much more needs to be accomplished before the 2D process can be ready for producing semiconductors on the scale needed.

From the medical standpoint, graphene and CNTs are being employed in developing sensors.  A team from Harvard [Ref. 4] has created a flexible electrode array that conforms to surfaces of the body.  The example application was described as being applied in difficult to reach places in order to provide recording or stimulation of electrical pulses without the potential of damaging nearby organs.  The team developed the gel and needed to create the required circuitry.  They developed a combination of graphene flakes and CNTs that could provide a continuous conductor path.  When created on the gel, the long CNTs provide a “long” continuous pathway by multiple point contact among numerous CNTs.  They then insulate it on the gel so that only the desired points are exposed.  They have successfully tested the gel in stimulation a mouse heart.  A key point in their development is that they needed to find some means of reducing the metal content required for conductivity.  And, they succeeded.

What we are witnessing is novel thinking in applying different type nanomaterials to solve problems that challenging to resolve with current technology applications.

References:

  1. https://www.techbriefs.com/component/content/article/tb/stories/blog/39416
  2. https://www.bbc.com/future/article/20210628-concrete-the-material-that-defines-our-age
  3. https://semiengineering.com/thinner-channels-with-2d-semiconductors/
  4. https://www.graphene-info.com/graphene-and-cnts-assist-creating-viscoelastic-electrode-arrays

Posted in Nanotechnology

Nanomaterials and Cement

It has been an interesting month as the country starts coming back to “normal”.  I was fortunate to have the opportunity to “attend” (virtually) a presentation by a University of Texas at Austin professor.  Professor Hugh Daigle provided a very informative presentation on “Nanotechnology for Upstream Oil and Gas Operations”. [Ref. 1]  Whether you are interested in Oil and Gas or not, there are some very interesting points that are important where your nanotechnology interests are.  The reference is to a YouTube video of the presentation. 

The presentation starts out with establishing the baseline of what is nanomaterial.  The slide at roughly 7:35 of the presentation presents why nanoparticles are so interesting.  This is followed by covering the forces that are important to consider at the small scale.  Most are aware of Electrostatic and van der Waals forces.  The Steric forces are not mentioned as much as the two previous ones.  The description of the application is interesting and has a good explanation of applications. 

Jumping forward to roughly 22:24 in the presentation the explanation of controlling nanoparticle surface charges is important to improving the properties of cement.  At roughly 25:30, he goes into an explanation of why this sizing of the nanoparticles can improve the properties of the cement.

Daigle’s presentation fits into an special area of my interest.  We know that the Roman Coliseum is still standing after 2,000 years.  We can not duplicate their efforts.  Research has been done and there are some interesting findings.  Reference 2 has the explanation that has been acccepted without too much understanding.  Basically, the Roman cement was superior due to using volcanic ash from the regions around the Gulf of Naples.  Also, it is known that the Roman cement cures under water, salt water to be precise.

The work reported in Nature by Alexandra Witze [Ref. 3] has taken this a step further.  A team headed by Marie Jackson discovered there is a very rare mineral formed in the Roman cement. [Ref. 4]  This mineral, aluminum tobermorite comes from a silicate mineral, phillipsite, which is common in volcanic rocks.  Their finding also identified crystals of aluminum tobermorite growing from it.  Apparently the tobermorite is grown from phillipsite by the action of salt water washing through the cement.  This increases the alkalinity of the cement.  It is a rare material.  The tobermorite strengthens the cement due to a plate-like structure that permits flexure not observed in today version of cement. 

Now, I come back to Professor Daigle’s presentation.  He talked about the size of the nanoparticle has a significant influence of the strength of the cement. To me the question I have is did the Romans develop a process that created a consistent size of nanoparticle that yielded the optimum size for the most strong cement?

For the doubters that think the Romans would not have sufficient knowledge/understanding to know that they needed a certain size material (nanoparticle), consider this fact.  In the Middle Ages, the artisans knew they needed a certain size gold nanoparticle to create the red coloring in stain glass windows.  Did they call it gold nanoparticles?  Of course not, but there had to be a process, probably milling, that after a certain time of processing yielded the proper size material to create the red color.  It is possible that the Romans could have had a similar process for the phillipsite.

It does provide some interesting questions about the capability of the Romans and their cement. 

References:

  1. https://youtu.be/cWzzR5h535g
  2. https://newscenter.lbl.gov/2013/06/04/roman-concrete/
  3. https://www.nature.com/news/seawater-is-the-secret-to-long-lasting-roman-concrete-1.22231
  4. https://www.degruyter.com/document/doi/10.2138/am-2017-5993CCBY/html

Posted in Nanotechnology

2D Materials are Making Progress

The recent past few months have seen a few published articles on 2D materials and their applications.  The pace is picking up.

One of the challenges of 2D materials is that the materials need to be incorporated into some other material.  A future possibility for semiconductor device transistors requires there must be a means of combining the 2D material with the silicon (or other material) substrate rapidly and in volume.   There are two significant issue with this combination.  One of the issues is that the 2D material and the semiconductor substrate require different temperatures that can damage the material already on the substrate.  The other is that the existing processes are not compatible with high-volume manufacturing.  Researchers in Sweden and Germany [Ref. 1] have developed a process that uses a standard dielectric and available wafer bonding equipment. 

The researchers attached the 2D material, which in on a wafer, and the semiconductor wafer.  Using pressure at room temperature, the two wafers are pressed together, and the temperature raised until the dielectric becomes viscous and allows the 2D material to conform to the surface of the existing material on the semiconductor wafer.  There efforts have been successfully demonstrated on a 100mm silicon wafer with uniform coverage and little strain in the 2D structures.

The development of 2D transistors has also been improving [Ref. 2], Professor Saptarschi Das of Penn State has worked on the viability of transistors from 2D materials.  The purpose of the research is to determine if the 2D transistor can be the future of semiconductors with a significantly reduced footprint.  This also implies the potential for faster speeds.  Reference 3 addresses the promises and prospects of 2D transistors.  It points out that there have been many proof-of-concept demonstrations.  There might be a need to evaluate the 2D transistors to a slightly different criteria to determine the performance of the devices.  This concept of transistor evaluation is also addressed in an Applied Physics Letters [Ref. 4], and it addresses specific parameters that need to be considered. 

Imec researchers are of the opinion that transistors made from 2D materials could become available in the near future [Ref. 5].  While they indicate that silicon will remain the primary source for the microscale electronics, transistors constructed from transition metal dichalcogenides have potential.  The challenge is creating a single atom layer that is a natural semiconductor. 

The need for the change in the transistor construction is due to the every shrinking geometry of the current transistor.  As the structure of the transistor becomes smaller and smaller, the potential for unwanted/spurious leakage of electrons continues to increase.  This is caused by the physical limits of the material property.  There have been design changes in the structure of the transistors, but the limits of material properties and the designs needed to circumvent this issue are continually getting more difficult.    A detailed discussion of the challenges of 2D materials and their application to transistor is available in Reference 6

The challenges of developing the most suitable material, creating an electronic structure that is efficient and fast, along with engineering a manufacturing process that is both high-speed and high-yield is non-trivial.  2D material transistors are coming, but it will take some time before 2D transistors are in main-stream production.  But, the 2D materials are coming.

References:

  1. https://www.techbriefs.com/component/content/article/tb/insiders/electronics-sensors/stories/38954?
  2. https://www.techbriefs.com/component/content/article/tb/insiders/electronics-sensors/stories/38953?
  3. https://www.nature.com/articles/s41586-021-03339-z
  4. https://aip.scitation.org/doi/10.1063/5.0029712
  5. https://spectrum.ieee.org/semiconductors/materials/coming-soon-to-a-processor-near-you-atomthick-transistors
  6. https://pubs.rsc.org/en/content/articlelanding/2015/nr/c5nr01052g#!divAbstract

Posted in Nanotechnology, Semiconductor Technology