Browsing by Subject "nanostructures"

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Doping Nanocrystals And The Role Of Quantum Confinement
(2007-09) Chan, T. L.; Tiago, M. L.; Chelikowsky, J. R.; Chan, Tzu‐Liang; Tiago, Murillo L.; Chelikowsky, James R.
Recent progress in developing algorithms for solving the electronic structure problem for nanostructures is illustrated. Key ingredients in this approach include pseudopotentials implemented on a real space grid and the use of density functional theory. This procedure allows one to predict electronic properties for many materials across the nano-regime, i.e., from atoms to nanocrystals of sufficient size to replicate bulk properties. We will illustrate this method for doping silicon nanocrystals with phosphorous.
Omnidirectional Current Enhancement From Laminated Moth-Eye Textured Polymer Packaging for Large-Area, Flexible III-V Solar Modules
(2021) Cossio, Gabriel; Yu, Evan D.; Tatavarti, Sudersena Rao; Scandrett, Brad; Yu, Edward T.
Epitaxial lift-off (ELO) processes have allowed for cheaper development of mechanically ﬂexible, ultra-thin, and high- efﬁciency III-V solar cells. ELO solar cells are natural candidates for applications where solar cells must conform to curved surfaces and provide high efﬁciency and high speciﬁc power generation (W/kg). Such examples include power generation for unmanned aerial vehicles, electric vehicles, and portable electrical power. However, when considering these mobile solar applications, large variations in angle of incidence (AOI) that inevitably occur can greatly decrease overall system efﬁciency due to signiﬁcant Fresnel reﬂections. In this article, we demonstrate the integration of moth- eye antireﬂection nanostructures on the polymer packaging layer of ELO solar cell arrays using a low-cost, colloidal self-assembly process. The moth-eye structures mitigate Fresnel reﬂections and increase photocurrent generation over all measured angles of inci- dence relative to ELO solar cell arrays with traditional untextured polymer packaging. The nanostructures survive a commercial lam- ination procedure, an important criterion that must be met to ensure the feasibility of integration into commercial processing. Outdoor solar characterization measurements are performed and, under direct optical illumination, moth-eye textured solar cell ar- rays show a maximum Isc enhancement of ∼58% at 79° AOI rela- tive to traditional untextured polymer packaged solar cell arrays, and when exposed to both direct and diffuse optical illumination a maximum Isc enhancement of ∼23% at 79° AOI is observed.
Programmable Three-Dimensional Self-Assembly
(2015) Glazener, William Stanton; Willson, Carlton Grant
The development of modern technology has emphasized the utility of nanomaterials and efficient design of nanostructures. Self-assembly is a powerful, bottom-up approach for the fabrication of nanomaterials. The Hammer and Tongs method that we have developed signifies the advent of a holistic approach to programmable, three-dimensional self-assembly. This method integrates biochemistry and chemical engineering techniques to create DNA-mediated, self-assembling polymer cubes. Selective functionalization of cubic faces with complimentary DNA sequences provides a programmable route for self-assembly. The development of this method and its process steps demonstrates the potential to form complex structures on extremely small scales.
A Reaction Diffusion Model Of Pattern Formation In Clustering Of Adatoms On Silicon Surfaces
(2012-09) Bagarti, T.; Roy, A.; Kundu, K.; Dev, B. N.; Roy, Anupam
We study a reaction diffusion model which describes the formation of patterns on surfaces having defects. Through this model, the primary goal is to study the growth process of Ge on Si surface. We consider a two species reaction diffusion process where the reacting species are assumed to diffuse on the two dimensional surface with first order interconversion reaction occuring at various defect sites which we call reaction centers. Two models of defects, namely a ring defect and a point defect are considered separately. As reaction centers are assumed to be strongly localized in space, the proposed reaction-diffusion model is found to be exactly solvable. We use Green's function method to study the dynamics of reaction diffusion processes. Further we explore this model through Monte Carlo (MC) simulations to study the growth processes in the presence of a large number of defects. The first passage time statistics has been studied numerically. Copyright 2012 Author(s). This article is distributed under a Creative Commons Attribution 3.0 Unported License. [http://dx.doi.org/10.1063/1.4757592]