Limits...
Superlattices: problems and new opportunities, nanosolids.

Tsu R - Nanoscale Res Lett (2011)

Bottom Line: Superlattice is simply a way of forming a uniform continuum for whatever purpose at hand.However, new opportunities in component-based nanostructures may lead the field of endeavor to new heights.The all important translational symmetry of solids is relaxed and local symmetry is needed in nanosolids.

View Article: PubMed Central - HTML - PubMed

Affiliation: University of North Carolina at Charlotte, Charlotte, NC 28223 USA. Tsu@uncc.edu.

ABSTRACT
Superlattices were introduced 40 years ago as man-made solids to enrich the class of materials for electronic and optoelectronic applications. The field metamorphosed to quantum wells and quantum dots, with ever decreasing dimensions dictated by the technological advancements in nanometer regime. In recent years, the field has gone beyond semiconductors to metals and organic solids. Superlattice is simply a way of forming a uniform continuum for whatever purpose at hand. There are problems with doping, defect-induced random switching, and I/O involving quantum dots. However, new opportunities in component-based nanostructures may lead the field of endeavor to new heights. The all important translational symmetry of solids is relaxed and local symmetry is needed in nanosolids.

No MeSH data available.


Typical SSE with TiO2 on Pt. Applied E field increases from 1: 50 V/μm, to 2: 100 V/μm, to 3: with 140 V/μm, showing increasing electron tunneling from EF, left, to the vacuum, right.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC3211173&req=5

Figure 7: Typical SSE with TiO2 on Pt. Applied E field increases from 1: 50 V/μm, to 2: 100 V/μm, to 3: with 140 V/μm, showing increasing electron tunneling from EF, left, to the vacuum, right.

Mentions: The graphene adventure took off more than anything I have seen in my entire life of research in solid state and semiconductors. In a way it reminded me of porous silicon because it involves silicon, the most widely used materials in electronic industry. However, the real reason is the availability of facilities to create porous silicon. All one needs is a kitchen sink. Ultimately it did not make the grade because porous silicon is not robust and mechanically stable. Using exfoliation, a little flake can represent a single layer of graphite allowing many to participate in this endeavor. However, I predict that unless controlled growth of graphene can be realized, the feverish activity will cease if large-scale growth of graphene cannot be realized. There is another major problem to be overcome. Graphene, a two-dimensional entity with sp2 bonding configuration in reality does not exist, because we do not live in a two-dimensional world. And graphite consists of weak van der Waals bonding. Even in a single isolated layer, it is not graphene with only sp2 bonds, because any real surface consists of surface reconstruction as well as adsorbents. And a stack of graphene forming graphite is best considered as lubricant, without mechanical stability and robustness. The answer lies in creating a graphene-based superlattice. Figure 7 shows a computed Graphene/Si superlattice using DFT [27] How to realize such a structure? Intercalation method would not work because it is hardly possible to introduce something uniform into the space between graphite planes. However, we know that nature creates coal with the Kaolin molecules, basically silicates and aluminates [28], in between the graphite layers. What represents in Figure 8 may very well be an empty wish, however, at this reporting, we are working toward growing Si/C superlattice.


Superlattices: problems and new opportunities, nanosolids.

Tsu R - Nanoscale Res Lett (2011)

Typical SSE with TiO2 on Pt. Applied E field increases from 1: 50 V/μm, to 2: 100 V/μm, to 3: with 140 V/μm, showing increasing electron tunneling from EF, left, to the vacuum, right.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211173&req=5

Figure 7: Typical SSE with TiO2 on Pt. Applied E field increases from 1: 50 V/μm, to 2: 100 V/μm, to 3: with 140 V/μm, showing increasing electron tunneling from EF, left, to the vacuum, right.
Mentions: The graphene adventure took off more than anything I have seen in my entire life of research in solid state and semiconductors. In a way it reminded me of porous silicon because it involves silicon, the most widely used materials in electronic industry. However, the real reason is the availability of facilities to create porous silicon. All one needs is a kitchen sink. Ultimately it did not make the grade because porous silicon is not robust and mechanically stable. Using exfoliation, a little flake can represent a single layer of graphite allowing many to participate in this endeavor. However, I predict that unless controlled growth of graphene can be realized, the feverish activity will cease if large-scale growth of graphene cannot be realized. There is another major problem to be overcome. Graphene, a two-dimensional entity with sp2 bonding configuration in reality does not exist, because we do not live in a two-dimensional world. And graphite consists of weak van der Waals bonding. Even in a single isolated layer, it is not graphene with only sp2 bonds, because any real surface consists of surface reconstruction as well as adsorbents. And a stack of graphene forming graphite is best considered as lubricant, without mechanical stability and robustness. The answer lies in creating a graphene-based superlattice. Figure 7 shows a computed Graphene/Si superlattice using DFT [27] How to realize such a structure? Intercalation method would not work because it is hardly possible to introduce something uniform into the space between graphite planes. However, we know that nature creates coal with the Kaolin molecules, basically silicates and aluminates [28], in between the graphite layers. What represents in Figure 8 may very well be an empty wish, however, at this reporting, we are working toward growing Si/C superlattice.

Bottom Line: Superlattice is simply a way of forming a uniform continuum for whatever purpose at hand.However, new opportunities in component-based nanostructures may lead the field of endeavor to new heights.The all important translational symmetry of solids is relaxed and local symmetry is needed in nanosolids.

View Article: PubMed Central - HTML - PubMed

Affiliation: University of North Carolina at Charlotte, Charlotte, NC 28223 USA. Tsu@uncc.edu.

ABSTRACT
Superlattices were introduced 40 years ago as man-made solids to enrich the class of materials for electronic and optoelectronic applications. The field metamorphosed to quantum wells and quantum dots, with ever decreasing dimensions dictated by the technological advancements in nanometer regime. In recent years, the field has gone beyond semiconductors to metals and organic solids. Superlattice is simply a way of forming a uniform continuum for whatever purpose at hand. There are problems with doping, defect-induced random switching, and I/O involving quantum dots. However, new opportunities in component-based nanostructures may lead the field of endeavor to new heights. The all important translational symmetry of solids is relaxed and local symmetry is needed in nanosolids.

No MeSH data available.