In many cases semiconductor industry leads the application of technology shrinkage. Each “generation” of new devices employs smaller and smaller dimensional structures in the circuitry. There is work being done on qualifying the processes for the 3nm and 2nm generation. Since future shrinkage will be fractions of a nanometer, Intel Corporation has indicated it is switching terminology from the 2nm to 20 Angstroms. (The term Angstrom has been employed in optics for centuries.) The next metric dimension identified is “pico” for 10-12 meters. That scale is well into the atomic structure.
Research has demonstrated that materials have different properties at the nanoscale from their bulk properties, which is commonly associated with the materials. One example is that silver has anti-bacteria properties in the low double-digit nanometers. Another example is that aluminum becomes highly reactive in the low double-digit nanoscale.
There are two phrases “floating” around in various publications: metamaterials and mesoscale materials. The former is human constructs of materials that are not normally found in nature and the term prominently employed in publications. Mesoscale, as defined by the Los Alamos National Labs [Ref.1] “is the spatial scale beyond atomic, molecular, and nanoscale where a material’s structure strongly influences its macroscopic behaviors and properties.” Stated differently, mesoscale can include the behaviour of a particular section of a large weather event, i.e., how the tornado interacts with the entire storm system, to the behaviour of a submicron section of material within the bulk material. It is the properties of a small section of a larger system that may have significantly different characteristics.
Metamaterials is usually identified by indicating this material has characteristics that are not seen in nature. “Metamaterials are a novel class of functional materials that are designed around unique micro-and nanoscale patterns of structures, which cause them to interact with light and other forms of energy in ways not found in nature. [Ref. 2] The properties of these materials are directly due to the combination of various material characteristic involving both their shape and thickness.
The ability to produce two-dimensional materials has provided the means of being able to investigate novel material properties. The vast majority of the work in metamaterials is focused on the modifying or influencing the behaviour of electromagnetic waves. These waves include the RF (radio spectrum), microwaves, and even infrared and visible light. Some details on these applications and what they can accomplish will be the subject of future blogs.
The point of this blog is to focus on the application of nanomaterials to create structures that do not exist in nature. As mentioned in previous blogs, during the Middle Ages, the artisans knew that adding certain size gold nanoparticles to the manufacture of glass would create the red color in stained glass windows. They could not measure the particles, but probably had a process or recipe that they followed to create the desired size particle. There are industries where ball milling is employed to provide a means of obtaining a sufficiently uniform particle size to enable the manufacture of the final product.
Next month, the blog will start covering details of the structure of metamaterials. One example that is employed to explain metamaterials involves light. When the light rays enter a material, the light is distorted by an amount that is related to the index of refraction, which is related to the amount of speed reduction of the speed of light in that material. Metamaterials can actually have a negative index of refraction. That means that the light will been in the opposite direction that is observed in nature.
There are many applications that are being considered. This could be a very important field to develop novel products that can produce effects that are currently impossible. More next time.