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High Fidelity Polycrystalline CdTe/CdS Heterostructures via Molecular Dynamics

MRS Advances

Aguirre, Rodolfo; Chavez, Jose J.; Zhou, Xiaowang Z.; Zubia, David

Molecular dynamics simulations of polycrystalline growth of CdTe/CdS heterostructures have been performed. First, CdS was deposited on an amorphous CdS substrate, forming a polycrystalline film. Subsequently, CdTe was deposited on top of the polycrystalline CdS film. Cross-sectional images show grain formation at early stages of the CdS growth. During CdTe deposition, the CdS structure remains almost unchanged. Concurrently, CdTe grain boundary motion was detected after the first 24.4 nanoseconds of CdTe deposition. With the elapse of time, this grain boundary pins along the CdS/CdTe interface, leaving only a small region of epitaxial growth. CdTe grains are larger than CdS grains in agreement with experimental observations in the literature. Crystal phase analysis shows that zinc blende structure dominates over the wurtzite structure inside both CdS and CdTe grains. Composition analysis shows Te and S diffusion to the CdS and CdTe films, respectively. These simulated results may stimulate new ideas for studying and improving CdTe solar cell efficiency.

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TYPE Journal Article YEAR 2017
ScopusOSTIDOI

High Fidelity Modeling of Ionic Conduction in Solids

Zhou, Xiaowang Z.; Doty, Fred P.; Foster, Michael E.; Yang, Pin Y.; Fan, Hongyou F.

TlBr has the properties to become the leading radiation detection semiconductor. It has not yet been deployed due to a short lifetime of only hours to weeks. While the rapid structural deteriorations must come from ionic conduction under operating electrical fields, detailed aging mechanisms have not been understood. As a result, progress to extend lifetime has been limited despite extensive studies in the past. We have developed new atomistic simulation capabilities to enable study of ionic conduction under electrical fields. Our combined simulations and experiments indicate that dislocations in TlBr climb under electrical fields. This climb is the root cause for structural deterioration. Hence, we discovered new strengthening methods to reduce aging. Our new atomistic simulation approach can have broader impact on other Sandia programs including battery research. Our project results in 4 publications, a new invention, new LAMMPS capabilities, solution to mission relevant materials, and numerous presentations.

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TYPE SAND Report YEAR 2016
OSTIDOI
Results 51–75 of 151
Results 51–75 of 151