Crystalline Molybdenum Oxide Thin-Films for Application as Interfacial Layers in Optoelectronic Devices.
The ability to control the interfacial properties in metal-oxide thin films through surface defect engineering is vital to fine-tune their optoelectronic properties and thus their integration in novel optoelectronic devices. This is exemplified in photovoltaic devices based on organic, inorganic or hybrid technologies, where precise control of the charge transport properties through the interfacial layer is highly important for improving device performance. In this work, we study the effects of in situ annealing in nearly stoichiometric MoOx(x ∼ 3.0) thin-films deposited by reactive sputtering. We report on a work function increase of almost 2 eV after inducing in situ crystallization of the films at 500 °C, resulting in the formation of a single crystalline α-MoO3overlaid by substoichiometric and highly disordered nanoaggregates. The surface nanoaggregates possess various electronic properties, such as a work function ranging from 5.5 eV up to 6.2 eV, as determined from low-energy electron microscopy studies. The crystalline underlayer possesses a work function greater than 6.3 eV, up to 6.9 eV, characteristic of a very clean and nearly defect-free MoO3. By combining electronic spectroscopies together with structural characterizations, this work addresses a novel method for tuning, and correlating, the optoelectronic properties and microstructure of device-relevant MoOxlayers.
NanoSYD, University of Southern Denmark , Alsion 2, 6400-Sønderborg, Denmark.
André L
http://orcid.org/0000-0002-0537-7793
AL
F Cauduro
National Center for Electron Microscopy, The Molecular Foundry, LBNL, Berkeley, California 94720, United States.
Roberto
http://orcid.org/0000-0002-6011-6078
R
Dos Reis
National Center for Electron Microscopy, The Molecular Foundry, LBNL, Berkeley, California 94720, United States.
Gong
G
Chen
National Center for Electron Microscopy, The Molecular Foundry, LBNL, Berkeley, California 94720, United States.
Andreas K
AK
Schmid
Sorbonne Universités, UPMC Univ Paris 06, CNRS UMR 7197, Laboratoire de Réactivité de Surface (LRS), 4 place Jussieu, 75005 Paris, France.
Christophe
C
Méthivier
NanoSYD, University of Southern Denmark , Alsion 2, 6400-Sønderborg, Denmark.
Horst-Günter
HG
Rubahn
Sorbonne Universités, UPMC Univ Paris 06, UMR CNRS 7588, Institut des Nanosciences de Paris (INSP), 4 place Jussieu, 75005 Paris, France.
Léo
L
Bossard-Giannesini
Sorbonne Universités, UPMC Univ Paris 06, UMR CNRS 7588, Institut des Nanosciences de Paris (INSP), 4 place Jussieu, 75005 Paris, France.
Hervé
H
Cruguel
Sorbonne Universités, UPMC Univ Paris 06, UMR CNRS 7588, Institut des Nanosciences de Paris (INSP), 4 place Jussieu, 75005 Paris, France.
Nadine
N
Witkowski
NanoSYD, University of Southern Denmark , Alsion 2, 6400-Sønderborg, Denmark.
Morten
M
Madsen
Reactive sputtering; electronic properties of metal-oxide surfaces; postannealing; single crystalline MoO3 thin films; substoichiometric nanoaggregates