TY  - JOUR
A1  - Crovetto, Andrea
A1  - Hempel, Hannes
A1  - Rusu, Marin
A1  - Choubrac, Leo
A1  - Kojda, Sandrino Danny
A1  - Habicht, Klaus
A1  - Unold, Thomas
T1  - Water adsorption enhances electrical conductivity in transparent p-type CuI
JF  - ACS applied materials & interfaces
N2  - CuI has been recently rediscovered as a p-type transparent conductor with a high figure of merit. Even though many metal iodides are hygroscopic, the effect of moisture on the electrical properties of CuI has not been clarified. In this work, we observe a 2-fold increase in the conductivity of CuI after exposure to ambient humidity for 5 h, followed by slight long-term degradation. Simultaneously, the work function of CuI decreases by almost 1 eV, which can explain the large spread in the previously reported work function values. The conductivity increase is partially reversible and is maximized at intermediate humidity levels. On the basis of the large intragrain mobility measured by THz spectroscopy, we suggest that hydration of grain boundaries may be beneficial for the overall hole mobility.
KW  - transparent conductors
KW  - CuI
KW  - copper iodide
KW  - conductivity
KW  - humidity
KW  - p-type
KW  - work function
Y1  - 2020
U6  - https://doi.org/10.1021/acsami.0c11040
SN  - 1944-8244
SN  - 1944-8252
VL  - 12
IS  - 43
SP  - 48741
EP  - 48747
PB  - American Chemical Society
CY  - Washington, DC
ER  - 
TY  - JOUR
A1  - Crovetto, Andrea
A1  - Kojda, Danny
A1  - Yi, Feng
A1  - Heinselman, Karen N.
A1  - LaVan, David A.
A1  - Habicht, Klaus
A1  - Unold, Thomas
A1  - Zakutayev, Andriy
T1  - Crystallize It before It diffuses
BT  - kinetic stabilization of thin-film phosphorus-rich semiconductor CuP2
JF  - Journal of the american chemical society
N2  - Numerous phosphorus-rich metal phosphides containing both P-P bonds and metal-P bonds are known from the solid-state chemistry literature. A method to grow these materials in thin-film form would be desirable, as thin films are required in many applications and they are an ideal platform for high-throughput studies. In addition, the high density and smooth surfaces achievable in thin films are a significant advantage for characterization of transport and optical properties. Despite these benefits, there is hardly any published work on even the simplest binary phosphorus-rich phosphide films. Here, we demonstrate growth of single-phase CuP2 films by a two-step process involving reactive sputtering of amorphous CuP2+x and rapid annealing in an inert atmosphere. At the crystallization temperature, CuP2 is thermodynamically unstable with respect to Cu3P and P-4. However, CuP2 can be stabilized if the amorphous precursors are mixed on the atomic scale and are sufficiently close to the desired composition (neither too P poor nor too P rich). Fast formation of polycrystalline CuP2, combined with a short annealing time, makes it possible to bypass the diffusion processes responsible for decomposition. We find that thin-film CuP2 is a 1.5 eV band gap semiconductor with interesting properties, such as a high optical absorption coefficient (above 10(5) cm(-1)), low thermal conductivity (1.1 W/(K m)), and composition-insensitive electrical conductivity (around 1 S/cm). We anticipate that our processing route can be extended to other phosphorus-rich phosphides that are still awaiting thin-film synthesis and will lead to a more complete understanding of these materials and of their potential applications.
Y1  - 2022
U6  - https://doi.org/10.1021/jacs.2c04868
SN  - 0002-7863
SN  - 1520-5126
VL  - 144
IS  - 29
SP  - 13334
EP  - 13343
PB  - American Chemical Society
CY  - Washington
ER  -