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Interface-Driven Structural Distortions and Composition Segregation in Two-Dimensional Heterostructures

Angewandte Chemie - International Edition

Medlin, Douglas L.

The discovery of emergent phenomena in 2D materials has sparked substantial research efforts in the materials community. A significant experimental challenge for this field is exerting atomistic control over the structure and composition of the constituent 2D layers and understanding how the interactions between layers drive both structure and properties. While no segregation for single bilayers was observed, segregation of Pb to the surface of three bilayer thick PbSe–SnSe alloy layers was discovered within [(PbxSn1−xSe)1+δ]n(TiSe2)1 heterostructures using electron microscopy. This segregation is thermodynamically favored to occur when PbxSn1−xSe layers are interdigitated with TiSe2 monolayers. DFT calculations indicate that the observed segregation depends on what is adjacent to the PbxSn1−xSe layers. The interplay between interface- and volume-free energies controls both the structure and composition of the constituent layers, which can be tuned using layer thickness.

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TYPE Journal Article YEAR 2017
DOIOSTIScopus

Strong Photothermoelectric Response and Contact Reactivity of the Dirac Semimetal ZrTe5

ACS Applied Materials and Interfaces

Leonard, Francois; Yu, Wenlong; Celio, Kimberlee C.; Medlin, Douglas L.; Sugar, Joshua D.; Talin, Albert A.; Pan, Wei

The family of three-dimensional topological insulators opens new avenues to discover novel photophysics and to develop novel types of photodetectors. ZrTe5 has been shown to be a Dirac semimetal possessing unique topological, electronic, and optical properties. Here, we present spatially resolved photocurrent measurements on devices made of nanoplatelets of ZrTe5, demonstrating the photothermoelectric origin of the photoresponse. Because of the high electrical conductivity and good Seebeck coefficient, we obtain noise-equivalent powers as low as 42 pW/Hz1/2, at room temperature for visible light illumination, at zero bias. We also show that these devices suffer from significant ambient reactivity, such as the formation of a Te-rich surface region driven by Zr oxidation as well as severe reactions with the metal contacts. This reactivity results in significant stresses in the devices, leading to unusual geometries that are useful for gaining insight into the photocurrent mechanisms. Our results indicate that both the large photothermoelectric response and reactivity must be considered when designing or interpreting photocurrent measurements in these systems.

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TYPE Journal Article YEAR 2017
DOIOSTIScopus
Results 76–100 of 222
Results 76–100 of 222
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