Semiconductors and Nanotechnology

There is a rule developed by Gordon Moore that projected the increase of density of semiconductors.  For many years the path “Moore’s Law” predicted (a doubling of density roughly every 18 months) has been followed.   The driver for this pattern was increased computing power for more and more complex operations.  For a number of years, the decreasing size was identified by the node, which is based on the smallest half-pitch.  (The half-pitch is one half of the minimum spacing between adjacent smallest metal lines.)  In the 1990s, the node designation changed from the minimum spacing due to technology challenges.  [Cf. Bill Arnold’s article for a in depth presentation. Ref. #1].

Once the material sizing requirements moves into the nano realm, there can be issues.  Under 50nm line widths, there can be differences in the conductivity of interconnect lines.  Copper conductors in this size range can have changes in resistance due to crystalline structures with grain boundaries causing conductance variations from line to line.  That is only one of many possible problems.  The chart below is adapted from the wikichip reference [Ref. #2] with the year added that a particular node is scheduled for volume production.

wikichip-org-technology-node

Table from wikichip.org [Ref. #2]

While production is currently in the size range where some effects of nanomaterials can occur, more impact is coming shortly.  The semiconductor industry is working on many different options including three-D stacking and innovative designs for transistors.  However, the projection is still to go to smaller and smaller sizes with the increasing challenges.  The last two blogs have provided some thoughts on the challenges.

There are numerous “surprises” with nanomaterials.  The fact that non-magnetic material can have magnetic properties at 13 atoms is interesting.  I am unaware of anyone who is investigating that property in incorporate in an application.  Transition metal in five different  states: as hydrated atom; metal complexed in a small protein; metal adsorbed to surface on 1nm mineral particle; metal adsorbed to surface of 20nm particle; the same except to a 200nm particle. [Ref. #3]  In addition, size may matter for crystal orientation preferences.  For example, CeO2 < 10nm prefers being a truncated octahedron with {100} and {111} faces.  CeO2 > 10nm shifts toward {111} octahedron. [Ref. #4]

So, what is going to be done?  There are many different portions to solving the problem.  Consider the time it takes a signal to cross from one side of a semiconductor chip to the other side.  How can the timing be maintained?    One possibility is to use light.  This requires some type of light guide on the semiconductor.  Research in this area has been ongoing for many years.  Recently there have been some initial publications of employing two dimensional material, like graphene, to create tunable gratings on the nano scale.  Is that where semiconductors are going?  Not in the near future, but it is one possible avenue of research for smaller and faster circuitry.

One item that has not been mentioned is the fact that at small scale, circuitry tends to increase the amount of energy lost, especially as heat.  As the computing power increases, the amount of heat generated increases.  As the amount of power required increases, the size of the power supply increases.  That makes portable electronics a problem.  While there is work ongoing to improve the capacity of batteries, the improvements have not experienced any breakthroughs.  A number of published articles have demonstrated advances by carefully controlling the nanomaterials employed in the battery.

The above is just a few of the potential challenges for the future.  The manufacturing challenges have not been mentioned, but they are substantial.  The development of increased capability electronics will witness learning more about and how to properly incorporate nanomaterials in a manner that improves performance and decreases the proportional power requirements.

References:

  1. https://spectrum.ieee.org/semiconductors/design/shrinking-possibilities
  2. https://en.wikichip.org/wiki/technology_node
  3. Hochella, Michael F. Jr.. Nanogeoscience: From Origins to Cutting Edge Applications. December 2008 issue. Vol. 4, pp. 373-379.
  4. Waychunas, Glenn A., Hengzhong Zhang. Structure, Chemistry, and Properties of Mineral Nanoparticles.  December 2008 issue. Elements.  4, pp381-387.

 

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Nano Material Properties and the need for multi-dimensional representations

Material properties are “well” defined.  If one goes to a reference source, the various properties of a pure material can be found.  For example, the atomic number of Lithium is 3.  It has an atomic weight of 6.941.  Its specific gravity is 0.534, with a melting point of 180.5C, and a boiling point of 1,347C.  Similarly, the atomic number of gold is 79 with an atomic weight of 196.9665.  Its specific gravity is 19.32 (20C), with a melting point of 1,064 and a boiling point of 2807C.

From last month’s blog, the “bulk” material properties may not represent the properties of nanoparticles of the material.  Consequently, there is a need to consider various individual isotopes of the materials that are being investigated.  The chart below {Ref. #1] shows the change in melting point as the size of the gold nanoparticle diminishes.  (Other examples are available in my September 14th, 2013 blog.)  The melting point of a number of materials starts to decrease when the particle size is near 50nm. Blog_1710_pix1What is the effect of increasing pressure?  Will it increase or decrease the melting point and/or the boiling point?  The answer is not initially obvious.  The answer is dependent on whether the material becomes more dense or less dense at higher temperatures.   If the material requires more space as it melts, the higher pressure increases the melting point.  If the material requires less space as it melts (think water), then higher pressure decreases the melting point.  The boiling point typically has an inverse relation with vapor pressure of the liquid and a positive relationship with atmospheric pressure.

Blog_1710_pix2The figure above [Ref. #2] shows the relationship of the boiling point of water to pressure.  (Consequently, the need for pressure cookers at higher altitudes for proper cooking temperatures.)

The figure above is an excellent visual representation of the impact of altitude (pressure) on the boiling point of water.  Similar graphs could be done for gold or lithium.  But how can one visualize the impact of the change in size at the nano realm.  Does there need to be another chart for 10nm gold and another for 15nm gold, etc.  Or would it be better to have a single pressure point and look at the change in melting point, which is the first figure.  Would it then be necessary to have a multitude of curves at various particle sizes?  Is it possible to develop a three-dimensional graph that has temperature, pressure, and size as the axes?  That could be done.

What happens when the other properties of the materials need to be considered.  Do the electrical properties change as the material becomes smaller?  Yes.  Do the magnetic properties change?  One could indicate no, but that would not explain the magnetic moment of 13 atoms of silver.  Does the ability of the material to interact with other materials change with size?  Again, the answer is yes.  Can the material change shapes?  Certain ones can.  The list of differences at the nano realm is very large.

How should this be handled?  There is a need to define key characteristics of nanomaterials that have a strong impact on the performance of the materials.  (Do we also do this for each of the predominant isotopes?)  Initially this effort needs to be established at 50, 45, 40, 35, 30, 25, 20 nanometers.  Below 20nm, it should be done at 2 nanometer intervals.  It is a lot of work, but to fully understand and apply the nanomaterials, the information is needed.  Each time new characteristics are determined, that data needs to incorporated into the available data.

The objection could be that there is no means of using all the multiple charts that would be developed.  The development of an effort like this can apply the rapidly developing field of augmented reality.  The ability to flip through various three-dimensional graphs to observe trends is easier if the data can be projected, rotated, and translated.   Visualization is a powerful tool.    We need a lot more data on nanomaterials and a means of using the data.

References:

  1. http://en.wikipedia.org/wiki/Melting-point_depression
  2. http://chemed.chem.purdue.edu/genchem/topicreview/bp/ch14/melting.php

 

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Are we missing the important capability of nanomaterials?

Particles with a dimension that is 100nm or less in size are considered nanomaterials.  But, size is not what provides the unique nanomaterial properties that are being observed. Consider the following:  80nm aluminum particles are dangerous as a possible inhalant.  30nm aluminum particles are very reactive (explosive) when they come in contact with air/oxygen.  70nm gold particles are fine dust, but below 20nm, these particles when added to glass change the color of the glass.  Just because a particle is less than 100nm does not give it special properties just because it is less than 100nm.

There are other interesting changes in behavior in the sub-100nm range that can impact how materials behave.  One example is that the adhesion forces of particles to surfaces change as the particles get smaller.  Below roughly 70nm, van der Waals forces become the dominate adhesion mechanism.  Most changes in material property and behavior start to occur somewhere in the 30nm to 70nm size region.  (Part of this reason for change is that the size of a particle diminishes into the region where a significant portion of the atoms have “access” to the particle’s surface with the resultant increased opportunity to react with other material.)

Currently, research in the nanotechnology realm work with basic elements and combinations of nano-scaled materials, which has created some materials with interesting properties.  Carbon has been the most researched with single walled nanotubes and multi-walled nanotubes having a lot of early interest.  The ability of the carbon nanoteubes to increase strength of other materials with a decrease in weight has been utilized in automotive and sports industries to name a couple areas.  Depending on the chirality of the carbon nanotubes, the resultant material can be either conducting or semi-conducting.  “Unrolling“ a single walled carbon nanotube results in the material called graphene, which is called a “two-dimensional” material due to being only one atom thick.  It is conductive.  Contaminating the surface with oxygen produces a material called graphane, which is non-conducting (different name, different properties – graphane not graphene). [Ref. 1, 2, & 3]

What if we are not considering all the possibilities?

The current published research focuses on using various bulk materials to develop experiments and find the new properties of the nanomaterial.  But, what if, nano-scale material is also different from bulk material due to the various isotopes of the material?

          Bulk material containing various isotopes

Bulk material consists of various isotopes of the specific element(s) in a ratio that has been determined through various techniques and has been quantified. [Ref. 4]  In general, one makes an assumption that the nano-scale material has the same isotope ratios as the bulk.  One also assume that the different isotopes of the bulk material have identical properties when present together.  Is it possible that individual isotopes are different from the bulk containing various isotopes?  Is this possible?

One example that shows there is a different in isotopes is uranium.  A specific form of the element (isotope) uranium is 235U, which makes up 0.07% of typical uranium in the mined ore.  238U is the predominant form on the element and has a half-life of 4.5 billion years, while 235U is more reactive and can be split to produce energy. [Ref. 5]  The isotope that is useful, 235U, is separated from other isotopes of that material.  It might be expensive and challenging, but if a specific isotope is useful, it will be obtained.

Another example of different properties of isotopes involves water.  A water molecule consists of two hydrogen atoms and one oxygen atom.  However, there are other forms (isotopes) of hydrogen that have one or two extra neutrons.  Water molecules that consist of oxygen and deuterium (hydrogen with one extra neutron) are called heavy-water and are employed in damping nuclear radiation.  So, one form of hydrogen has properties that the other does not.

It can be stated that in this case, the extra neutron causes a significant percentage increase in the atom’s mass.  Work has been done that states the impact of additional neutrons are the greatest on the elements with the lowest mass.  Some projections imply that the additional of extra neutrons does not have a significant, if any, impact on the material properties.  Is this true?  What about 235U?

Consider Lithium with two stable isotopes, 6Litium and 7Lithium, with 7Lithium accounting for over 92% of the material.  There are also a number of short lived lithium isotopes. [Ref. 6 & 7]  It is known that 6Lithium has a greater affinity than 7Lithium for the element mercury.  This fact is used in the separation of the two isotopes of Lithium.  How is this possible if the extra neutron does not change the material properties?  Maybe it does!

Is it possible that we need to think about research that works with specific isotopes of “common” materials?  If various isotopes have different reactions with other materials, is it possible that “lumping” all isotopes of an element into an experiment actually degrades the performance that a single isotope might have? At a minimum, research that works with specific isotopes of “common” materials should clearly state the isotopes used, including any percentage of other isotopes that may be present, which may impact performance.

          Material purity

There are various levels of material purity that can be purchased.  Very high purity copper can be obtained that at 99.9999% pure.  That is one part per million pure material.  Other materials are not available in purities of greater than 99.99% and some are not even close to 99%.

It is known that doping of semiconductors with a very small percentage of different elements can change the properties of the combined material.  Doping in silicon (semiconductors to increase the charge carrier concentration) can range from lightly doped (parts per billions) to heavily doped (parts per thousands) of the doping material.  Depending on the materials employed, other effects besides carrier concentrations can be impacted.  Lithium can be employed for increasing the resistance of solar material (solar cells) to the sun’s radiation.

Has anyone examined the percentage impurity of isotopes in common materials, like carbon or copper?  In order to conduct that experiment it would be necessary to have pure material and then add impurities.  How difficult is that?  Consider that conventional computer hard drives require more than 1 million atoms per bit and over ½ billion atoms per byte!  Consider a 2µm copper sphere.  Calculations yield that it should have 3.56 x 1011 atoms.  If the material is six 9s pure, it contains 356,000 contaminant atoms! [Ref. 8 & 9] Do we really know the true properties of materials?

When the materials are in the nano-scale region, the total quantity of atoms is smaller.  A 30nm aluminum particle has roughly 850,000 atoms in it.  “Super pure” aluminum can be as much as five 9s pure.  That would still leave 9 contaminant atoms.  Is that enough to modify material properties?

          Material isotope homogeneity

Another question is whether anyone has worked with a pure isotope of common materials.  Granted that there are techniques for separating the isotopes, e.g., uranium, which can produce high purity materials.  But, when the desired isotope exists as a very small percentage of the total material, it takes many passes through a process to achieve the desired concentration and that concentration is not 100%.  It may be enough to be effective, but it is not 100%.

Copper has 29 isotopes with the two predominant being 63Cu (69%) and 65Cu (30.8%).  That implies that the pure copper one can acquire will typically be 69% of one type and 31% of the other.  Aluminum is interesting in the that for all practical purposes, 100% of aluminum is 27Al.  So any changes to the properties would be due to contaminants and not isotopes of aluminum.

Thoughts

If we have found that different isotopes of materials may have different properties in the bulk, is it not reasonable to anticipate that there will be different properties in the nano realm?  Maybe we should start to investigate the properties of various isotopes of nanomaterials?  Are we missing some potentially important properties when we do not investigate the isotopes on various nanomaterials?  Do we have the concept of nanotechnology research mis-focused or just misunderstood?  Any thoughts?  Send to: Ideas at nano-blog.com (The email address has been written with “at” in place of the “at symbol” to avoid spam filling the mail box.)

Acknowledgements:

Special thanks to Deb, Evelyn, and Harold for critical review and suggestions to improve this blog.

References:

  1. Carbon – http://www.rsc.org/periodic-table/element/6/carbon
  2. CNT – https://web.stanford.edu/group/cpima/education/nanotube_lesson.pdf
  3. CNT – https://www.nature.com/articles/ncomms5892
  4. Isotopes – https://en.wikipedia.org/wiki/Isotope
  5. Uranium – http://www.world-nuclear.org/information-library/nuclear-fuel-cycle/introduction/what-is-uranium-how-does-it-work.aspx
  6. Lithium – https://en.wikipedia.org/wiki/Isotopes_of_lithium
  7. Lithium – http://www.rsc.org/periodic-table/element/3/lithium
  8. Atoms – http://gizmodo.com/5875674/ibm-figures-out-how-many-atoms-it-takes-to-hold-a-bit-hint-its-12
  9. # of atoms – https://socratic.org/questions/a-pure-copper-sphere-has-a-radius-0-929-in-how-many-copper-atoms-does-it-contain

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2-dimentional material and other nano properties

Material: Two-dimensional materials seem to have a staying power in various technical news magazines.  The US Department of Energy released a report on efforts involving the Lawrence Berkeley National Laboratory work on molybdenum disulfide (MoS2). [Ref. 1]  Granted that the quantity production of this or any other 2-D material is difficult.   Research is ongoing to determine the properties of the various 2-D materials with the knowledge that when some material exhibits characteristics that are very important for device development, someone will develop a means of producing the material in sufficient quantity.  The researchers measured the bandgap of the material and found it to be 30% higher than theoretically predicted.  The fact that they are able to develop a means of accurately measuring the bandgap holds promise for evaluating other materials.  The researchers also found a relation between electron density and the bandgap.  There findings indicate a possible application in sensors where optical or electrical effects can produce the complimentary effect.

There was a caution that the molybdenum disulfide is extremely sensitive to its local environment.  This is not different from the impact of exposure of graphene to the atmosphere.  Considering that 2-D materials are one atom think, it means that 100% of the atoms are on the surface and able to react with the environment.  Contamination by external factors ends up reducing the properties of the basic material.  This fact makes some of the planned applications challenging.

Nano-scale motion:  Researchers at CalTech have made measurements of spherical gold nanoparticles moving in in water using a technique called liquid-cell 4D electron microscopy. [Ref. 2]  A key element in observing the motion was the application of femtosecond laser pulses.  Their efforts were of a liquid, a few hundreds of nanometers thick, captured between parallel plates.  The particles appear to be driven by steam nanobubbles near the particles surface.  This provides the initial action and then the resultant motion is a random motion as particles bounce of other particles.  The hope is that the knowledge gained from this work will provide knowledge to develop both micro and nano actuated transport mechanisms.

Light induced crystal shape changes: Work by scientists at KAUST demonstrated photostriction in Perovskite crystals.  In particular the researchers focused on MAPbBr3.  When illuminated by light, the material’s photostriction changes the internal strain in the material.  Their technique which employs in-situ Raman spectroscopy with confocal microscopy was able to measure intrinsic photoinduced lattice deformation.  The researchers demonstrated that only a part of the change was due to the photovoltaic effect.  They theorize that the generation of positive and negative charges due to the light polarizes the material which creates a change in the material structure.  The researchers think that understanding the mechanisms behind the structural changes could provide a significant benefit in developing greater efficiency solar cells.  Other possible applications include optoelectronic devices.

Thoughts: The tools for working in the nano-realm are improving.  The discovery of different properties that could be applied to new devices are increasing.  The “nano” revolution has been around for a number of years.  There are application of nanomaterials being applied to commercial products for increased performance.  Medicine is using the nano-sized carriers to combat diseases.  But, are we missing something basic?  Are we really using the properties of the nano-scale?  More on this line of thinking later.

Reference:

  1. http://www.newswise.com/doescience/?article_id=680155&returnurl=aHR0cHM6Ly93d3cubmV3c3dpc2UuY29tL2FydGljbGVzL2xpc3Q=
  2. http://nanotechweb.org/cws/article/tech/69765
  3. https://phys.org/news/2017-08-photosensitive-perovskites-exposed.html

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Nano-Safety Educational Efforts

There is a book being published in late 2017 by De Gruyter called “Nano-Safety, Wheat We Need to Know to Protect Workers” [Ref. 1].  (Full disclosure, I am one of the editors for the tome and co-author of two of the chapters.)   I am covering this topic because we, the editors, are at the completion of a process that has taken well over two years.  When you see a technical book, you may think “I could have done that.  It would be easy.”  So, I want to tell a story.  The concept for the book came after more than six years in trying to establish the importance on nanotechnology safety and the need for training people in the proper handling of nanomaterials.  This builds on my blog of December 13, 2014 that talks about the efforts to get contracts to develop the needed procedures.

The material in the book is partially based on the evaluation of various feedback received from both students and professional reviewers of the two courses that were created.  Once we had the feedback and the emphasis a that there was a need to develop a book that addresses nanotechnology safety (Nano-Safety), there was a need to find a publisher.  This was not an easy process.  One needs a technical publisher that is interested in the topic.  Everyone wants nanotechnology this or nanotechnology that, but nanotechnology safety?  That was another story.

Of course, the publisher needs to see the outline of the chapters and the potential authors of chapters.  The outline will go through  a number of revisions, partially because the publisher is looking for some specific ideas,  There is also a need to have the authors still be working in the specific topic identified.  This normally requires some modifications to content as authors change.

Once there is a contract in place, the real work starts.  Authors are informed to move forward and given a deadline of a year or so.  Not hearing anything from the authors greater 9 months or more is usually a sign of some issues developing.  Sometimes, a new author must be found.  People get sick or change jobs or something else.  So there is a need for the new author to meet a much tighter time schedule.  Once the draft chapters are in hand, each must be reviewed by three or more people competent in the field.  This is always a problem in emerging fields.

Having the reviews of the chapters in hand, each author must be contacted a provided the comments from the reviewers, who are anonymous.  Then the authors revise their manuscripts and submit them to the editors.  Depending on the severity of the comments, the documents may need to go through another review process.  If the comments are minor, the editors may check to ensure all the concerns were addressed properly.  Then the manuscripts are sent to the publisher, who also reviews them.  There may be interaction with editors on minor points.

Next, the galley proofs arrive and each author needs to address the minor issues that are identified.  Finally, the book is ready to move to the publisher’s printing schedule.  Considering everything that takes place, two years is not a long time.

Reference 1: Nano-Safety, Dominick Fazarro, Walt Trybula, Jitendra Tate, Craig Hanks,  De Gruyter Publisher 2017, ISBN 978-3-11-037375-2

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Two-dimensional materials and moving them into production

There has been more work reporter on 2-D materials, also called atomic level materials.  Typically, this term refers to a sheet of material that is only atom thick with the other two dimensions that extend as far as can be produced, which normally is not to great.  The first material that was referred to this way was graphene.  There are interesting properties. Graphene provides strength as well as electrical properties.  There have been claims that 2-D materials will lead to improved performance in solar cells, new electronics based on 2-D transistors, various filtering mechanisms, and even a novel type of semiconductor.

This development has been ongoing for over 10 years.  Like carbon nanotubes, the applications seem almost infinite, but the actual release of products based on the materials is very slowly moving forward.  You could ask why.  For the researcher, the development of novel ideas is what get papers published or patents issued.  Moving a product into production is a totally different story.  The concerns include customer acceptance, the ability to have a sufficient quantity of quality material required for the products, a distribution channel, and a guaranty of a quality product.

As the iPhone is approaching its 110 anniversary, it is hard to remember what it was like before the iPhone.  One of the more advanced phones was produced by Blackberry.  It had an actual keyboard, albeit small, that could be used for entering data.  The competition had the 12 keypad that required multiple taps to go from a number, to an underlying capital letter and finally to a small letter.  Since each key had at least three letters along with a number, it was a task.  The keyboards took approximately ½ of the phone face.

Apple took a huge bet to create a phone with a larger screen and incorporated the keyboard onto the screen through the touch display.  That with the addition of additional functions for the phone enabled the sales to skyrocket.  Other companies had to change their models to compete and stay viable.  Apple had gambled and it paid off.  What if it failed?  Apple would not be the household word it is today and it might not have survived.

Manufacturing of a product also has risks.  Someone comes along and has a process or material that will take 10% off the cost of the final product, yet companies are reluctant to try it.  Why?  A 10% or 15% cost reduction sounds like something that should be done immediately.  The issue is that no new material or new process is introduced and immediately starts providing dividends.  Typically, when a new process is introduced, there is a slow done in production due to working our process bugs or material issues.  Yields normally decline until the bugs are worked out.  All of this is lost sales/revenue.  If the modification can not be implemented to the level desired, there is more lost product with the corresponding losses.  Sometimes even a 50% improvement might not be sufficient to try introducing a novel change.

So how does this impact 2-D materials?  One of the greatest problems with 2-D materials is getting sufficient quantities of the quality product needed.  I know of a significant stride in measuring pressure that employed a 2-D material.  This effort crashed when there was an attempt to make more than a few laboratory samples.  The quality, quantity, and size required were not capable of being obtained.

2-D materials need to progress further in development so the quality of the materials can  be relied on.  After that is achieved, the size and volume of material needs to be developed.  All of this happens after the applications are first proven in the lab.  This takes time, although all would like it to happen faster.  It is coming but it is coming slowly.   Without any question, more effort is needed to address the manufacturing challenges.

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More Proof that the Nanoscale is Different

Results reported in the May 24, 2017 issue of Phys.org is titled: “Water is surprisingly ordered on the nanoscale.”  (Reference is at the end of the blog.) “Researchers from AMOLF and Swiss EPFL have shown that the surface of minuscule water drops surrounded by a hydrophobic substance such as oil is surprisingly ordered. At room temperature, the surface water molecules of these droplets have much stronger interactions than at a normal water surface.  This may shed new light on a variety of atmospheric, biological and even geological processes.

The article indicates that the researchers have developed an ultraviolet laser with overlapping, very short pulse duration, which enabled them to measure water droplets in the region of 25nm to 50nm.  The purpose of this work was to develop an understanding of the interaction these size droplets have in interacting with other particles.   Water droplets this size occur naturally in the atmosphere.  Specific investigations were looking at the reaction in a hydrophobic environment.

The resulting findings indicate that the surface of the water is more organized than expected.  There is a very hydrogen bond that appears in supercooled liquid at least 50 degrees higher than anticipated.  Researcher Sylvie Roke commented: “The chemical properties of these drops depend on how the water molecules are organized on the surface, so it’s really important to understand what’s going on there.”  Future work will target the water surface with different materials including salt.

For me the interesting part of the work is that it is examining liquid molecules and not solid material.  If one examines the work that has been done on material like iron or aluminum, there exists a more reactive material when the particle size get slightly smaller than 50nm.  Why?  The reason is that the number of atoms on the surface and able to react with external forces is a significant portion of the total atoms.  A very rough rule-of-thumb that I use is at 50nm about 3% of the atoms can be influenced by the surface interactions.  At 3nm, roughly 50% of the atoms can be influenced by surface interactions.  Somewhere between these two extremes, there is sufficient interaction to cause a change in atomic and molecular behavior.

The fact that the researchers can observe results on nano-sized  liquids is very promising.  Work has been ongoing on solids for years and we are still learning about how the surface interactions influence the reactions.  Being able to move into the liquid realm should provide for some interesting and unexpected results.

Remember that the material properties continue to change as the size gets smaller.  The pictures of different size gold particles in solution with each exhibiting different colors is just one example of changing properties.  Imagine what will be found if different sized molecules of the same molecules can be individually examined.  This work could be the first steps in an interesting and promising new field of research.

References: https://phys.org/news/2017-05-surprisingly-nanoscale.html

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A Key Nano Device Manufacturing Challenge

The use of “nano” has become commonplace.  Projections are made about creating individual items/molecules/devices at the nano-scale.  There are examples of nano clocks, vehicles, etc.  Given enough effort, funding, and time, it is possible to create a large variety of nano-things.  Making one is not the problem.  It is manufacturing them in volume quickly and efficiently.

Today’s semiconductors may contain over one billion transistors.  The devices are made on silicon wafers that can be as large as 450 mm (about 18”).  The devices themselves are millimeters in dimensions, which provides the ability to create thousands of devices on a single wafer.  The processing of the wafers is normally done in lots of multiple wafers to efficiently use the very expensive equipment required for making semiconductors.  As the dimensions of the transistors have been decreasing, the cost of the equipment to build a semiconductor manufacturing fabrication facility (also known as a Fab) is increasing and will be in the $10s of billions.  The changes in the size of features has been following a observed rule, called Moore’s Law, that projects a reduction in dimensions of 70% over a period of 18 to 24 months.  (70% in length and 70% in width yields a 50% reduction in area or a doubling in density.) The current and next generation of equipment to manufacture the smaller sizes are requiring equipment that is larger and larger.  The tools used for creating the images on the wafers are increasingly complex and becoming much larger.  In addition to the size shrinkage, more complex circuitry requires more supporting connections, which increases the number of levels each device has.  Additional levels require more equipment to be able to manufacture the devices.  It is to the point that the new equipment does not fit into many existing facilities.  Thus, new facilities need to be constructed.

What does that have to do with nano devices?   The nano devices need to be manufactured somehow. Currently available 3D printing technology has a limit of about 25 micrometers or about 0.001 inch, and it is not very fast.   If we consider the current state of semiconductor production, tolerances are a fraction of the desired feature.  If one is considering 14 nm features, the placement of related features needs to be a small fraction of that dimensions.  How is that achieved.  There are many ways, but consider two.  The creation of a fiducial mark on the silicon substrate can be employed for alignment, but the ability to register to the fiducial marks must be very accurate.  It is possible to also register from a carefully created edge on the material, which is easier to find than the fiducial mark.  This appears to be a couple of good means for establishing relative positioning.  There is one issue.  If the 14 nm features are considered, the tolerance is going to be less than 3 nm.  How does one create material with an edge or a fiducial mark that is accurate to 3 nm?  It is not easy.

In order to manufacture something in quantities, it is necessary to be able to measure the characteristics of the object to at least an order of magnitude smaller than the dimension being measured.  If the 3 nm dimension is considered, an order of magnitude smaller means measuring atoms.

So the Key Challenge is the development of tools that can quickly and accurately measure dimensions that are very small with nanometer and sub-nanometer precision.

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Science Fiction continues to become Science Fact

This blog is an update of a topic from my November 2014 blog.  In those comments, I mentioned the science fiction of the Star Trek programs that have evolved into the today’s (and tomorrow’s) commercial products.  The communicator can be seen as a direct influencer of today’s “smart” phones.  Since then, there have been some interesting developments related to phones.  But we are not near the potential of the communication devices (I am changing the description from phones).

There have been significant improvements in hearing aids.  These are developing features that are bringing additional capabilities to hearing (communication) assistance devices.  Currently some hearing aids have Bluetooth capabilities.  The coupling can be done directly to iPhones.  Android phones are capable of similar coupling with enabled hearing aids.  (I have been informed that the battery usage with Android devices is slighter greater, which should improve in the next generation of features.)  So it is possible, to have your phone go directly to a hearing assisted device (HAD).  There is no need for other devices to listen to your phone conversation.   The interesting point is that there is at least one type of hearing aid that is not coupled as a pair to Bluetooth.  What does that mean?  It is possible to have each ear primarily receiving signals from separate devices or the environment and a device.

Why should we care?  There is a new product that will be available later this year called “Travis” [Ref. 1].  “Travis” indicates that it will have the capability of translating 20 different spoken languages off-line and 80 with an on-line connection.  The program does not auto select, but requires input of the desired language.  [Disclaimer: This product is in early development as a crowd sourced effort, and is not available to the general public yet.  Consequently, the full performance and accuracy are unknown.]  Why mention this?  “Travis” will have Bluetooth capabilities.

This will be the first of many such devices that will be able to couple to HADs.  Given that capability and the ability to have the device in each ear coupled with different devices opens up some interesting possibilities.  For this to be effective, the performance needs to be very good.  One of the issues with conventional hearing aids is that they end up with less than ideal performance.  In the article discussing new approaches, there is mention that only 25% of people who need a hearing aid actually use one. [Ref. 2]  There is work being done on developing methods to sort different streams of input signals so that the person is able to sort out what s/he needs.  This need is explained by the term “cocktail party problem”, which explains that distinguishing separate voices from the background noise is done through the brain separating incoming signals into separate streams.  That capability is not incorporated into hearing assist devices – yet.

There are more issues before we can get to a device that is represented by the Star Trek communicator.  The directional microphone that is incorporated into the emblem worn in the program is not available, but could be.  With the ever increasing power of computers, many of the functions of translating and communicating will be available in packages much smaller than today’s phones. Power is another issue that is slowly being solved.  Some efforts are being made to use energy harvesting from a person’s normal daily activities.  The incorporation of nano-sized devices is being investigated for various applications, which would assist in prolonging battery life.

There are still many things that need to be developed.  Memory is a major problem.  The need to store not only words but nuances of other languages starts to rapidly increase the memory size, especially as different languages are added.  There have been some articles that indicate a vocabulary of 2,000 words provides the ability to “get by” in a language.  For business/technical conversations, that number increase by a least an order of magnitude.

Take the translator function one step farther.  There is a need to be separate Bluetooth connections to a phone for the HAD and for the microphone.  The latter is needed to translate the spoken phrase into the receiving language.  The other needed function is to be able to reproduce the speaker’s actual voice in that language, which will be coming in the future.

There have been more developments of the tri-corder.  This will be covered in a future blog.  Enjoy being part of the future as it develops.

References:

  1. travistranslator.com
  2. http://spectrum.ieee.org/consumer-electronics/audiovideo/deep-learning-reinvents-the-hearing-aid?utm_source=Tech+Alert&utm_medium=Email&utm_campaign=TechAlert_03-02-17&bt_ee=iwcLpC+/eyxsWaLSQGFnO2NaksMjYJEI/KuJiv/R2opOzjAJb98d78xAvJ4tyZlL&bt_ts=1488467072351

Disclaimer: While mentioning “Travis the translator” in this blog, this is not an endorsement of the device being developed.  I have no financial interest in the company outside of having ordered a unit.

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Applications based on the properties of new materials

Composites: An interesting set of articles have appeared on composite metal foams.  Research conducted at North Carolina State University (NCSU) by Professor Afsaneh Rabiei [Ref. 1] has developed a material with sufficient properties to stop an armor piercing bullet.  The national Institute of Justice specification is that a bullet be stopped with an indentation of less than 44 mm at the back of the armor.  This particular CMF under an inch thick can stop the bullet with less than an 8 mm indentation at the back.

Metal foams are materials that can be produced by pumping gas through molten metal as it cools.   Cornell University has a different process that places foam into molten metal in a vacuum, where the foam fills the pores within the metal structure.  This material is composed of a soft alloy with a porous silicone foam.  The resultant material is lead free, which opens up many different applications.

The properties of the NCSU composite material is very light weight and appears to have the potential for being employed in nuclear waste storage, since it has some radiation absorbing properties.

Transistors: Applications of graphene transistors have been increasing.  A Japanese research team at Japan’s National Institute for Materials Science designed a graphene field-effect transistor (GFET) consisting of titanium-gold electrons on a single layer graphene deposited in a silicon substrate.  [Ref. 2] The “GFETs can detect harmful genes through DNA hybridization, which occurs when a ‘probe DNA’ combines, of hybridizes, with its complementary ‘target DNA’   Electrical conduction changes in the transistor when hybridization occurs.”

The current procedure detects the DNA hybridization through a labeling of the target with a fluorescent dye, which will shine brightly when it combines with its probe.  This is a complicated and expensive procedure, which also requires expensive laser scanners to detect the fluorescence.  The researchers look to the development of biosensor applications that are focused on genetic disease detection.

Better Magnets through observing Graphene: A system of tri-layer graphene has been has been developed that allows observations of electronic interactions within the three layers of graphene. [Ref. 3] Their work sheds light on magnetism of electrons in three layers of graphene at -272 Celsius and occurs from coordinated weak interactions among many electrons.  Their explanation is that metals have a large density of electrons. Observing the wave nature of elections requires a metal wire of a few atoms wide.  The scattering of atoms occurs in 100nm or less.  Graphene, which has a smaller density of electrons can travel up to 10 microns before scattering.  Observing electrons in graphene between layers for boron nitride provides the ability to observe the electron interactions and the faint “whispers” (as the researchers call it) of electrons interacting with each other.  Understand the interactions will enable the construction of materials with greater interactions.  While they are not projecting future efforts, it is very possible that the understanding of the interaction could lead to the properties required for a material to be a room temperature super conductor.

The developments based on increased understanding of material properties at the nano level can lead to very promising developments in novel material properties.  Stay tuned for more developments in 2017.

References:

  1. https://news.ncsu.edu/2016/04/metal-foam-tough-2016/
  2. https://phys.org/news/2017-02-dna-detecting-transistors.html
  3. http://www.graphene-info.com/tri-layer-graphene-supports-new-type-magnet

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