as a TCO. [1-3] This material is superior in conductivity to ITO, [1] and it is composed of abundant elements. In addition to its potential as a TCO, SVO constitutes the metallic endmember of several Mott-insulating systems such as La 1−x Sr x VO 3. [4-6] These systems attract interest both for their fundamental physics [7] and their potential for novel types of Mott-electronics. [8,9] It is therefore highly desirable to synthesize high quality films of this material, in order to unlock its full potential as TCO and to allow access to its interesting fundamental physics without the masking of high defect concentrations. To date, the highest quality SVO films have been demonstrated via hybrid molecular beam epitaxy (hMBE), where vanadium is supplied by a metal-organic precursor and strontium by a conventional thermal source. [10-12] In hMBE, by carefully calibrating the growth parameters, a self-limiting growth window can be obtained, [11,13-17] which provides the ultimate route for precise stoichiometry. [18] The lattice constant of epitaxial oxides provides a sensitive probe of their order and stoichiometry. [19] In addition, for many conductive oxides the residual resistivity ratio, RRR, is the most accurate probe, [20] since its sensitivity to defects far exceeds that of most structural and chemical analyses. RRR is the ratio between the room temperature and low temperature (2-5 K) resistivity. Based on Matthiessen's rule, RRR gauges the relative scattering by lattice defects versus the phonon scattering, and high values attest to the quality of the crystal structure and accuracy of the stoichiometry. The hMBE examples above have consistently reported RRR values exceeding 200, demonstrating the unrivaled accuracy of properly calibrated hMBE. Recently, significant efforts have been applied to understand and optimize the pulsed laser deposition (PLD) and growth kinetics of SVO, [21] with a record RRR value of 11.5. [3] While hMBE and PLD can be used to grow epitaxial oxides on conventional semiconductors, [22-25] an insulating interfacial layer forms at the contact with the semiconductor, preventing efficient charge collection from the substrate. Conventional molecular beam epitaxy (MBE) is the only method to date to allow atomically abrupt epitaxial interfaces between conducting oxides and conventional semiconductors such as Si and GaAs. [26] Such abrupt interfaces are crucial for efficient transport of charge across the interface. [27-29] Furthermore, MBE is a scalable method that is being used by the industry The correlated metal SrVO 3 is an attractive earth-abundant transparent conducting oxide (TCO), a critical component of many optoelectronic and renewable energy devices. A key challenge is to synthesize films with low resistivity, due to the prevalence of defects that cause electron scattering. In addition to the material's promise as a TCO, its interesting correlated-electron physics is often obscured by a high defect concentration, which inhibits its further development into new types of devices. A rou...
Migration of additives to organic/metal interfaces can be used to self-generate interlayers in organic electronic devices. To generalize this approach for various additives, metals, and organic electronic devices it is first necessary to study the dynamics of additive migration from the bulk to the top organic/metal interface. In this study, we focus on a known cathode interlayer material, polyethylene glycol (PEG), as additive in P3HT:PCBM blends and study its migration to the blend/Al interface during metal deposition and its effect on organic solar cell (OSC) performance. Using dynamic secondary ion mass spectroscopy (DSIMS) depth profiles and X-ray photoelectron spectroscopy surface analysis (XPS), we quantitatively correlate the initial concentration of PEG in the blend and sequence of thermal annealing/metal deposition processes with the organic/Al interfacial composition. We find that PEG is initially distributed within the film according to the kinetics of the spin coating process, i.e., the majority of PEG accumulates at the bottom substrate, while the minority resides in the film. During electrode evaporation, PEG molecules kinetically "trapped" near the film surface migrate to the organic/Al interface to reduce the interfacial energy. This diffusion-limited process is enhanced with the initial concentration of PEG in the solution and with thermal annealing after metal deposition. In contrast, annealing the film before metal deposition stalls PEG migration. This mechanism is supported by corresponding OSC devices showing that V increases with PEG content at the interface, up to a saturation value associated with the formation of a continuous PEG interlayer. Presence of a continuous interlayer excludes the driving force for further migration of PEG to the interface. Revealing this mechanism provides practical insight for judicious selection of additives and processing conditions for interfacial engineering of spontaneously generated interlayers.
Surfaces of correlated electron oxides are of significant interest from both fundamental and applied perspectives. Many such oxides feature a near-surface region (NSR) that differs from the bulk's properties. The NSR can significantly affect the interpretation of the material's electronic structure, especially for those in thin film form, and have detrimental effects for applications such as field effect devices and catalysts. In this work, we study the changes in the composition and the electronic structure of the NSR of SrVO 3 (SVO) thin films. We employ x-ray photoelectron spectroscopy (XPS) and compare TiO x -capped SVO films to identical uncapped films that were exposed to ambient conditions. The significant overoxidation of the SVO surface in the bare film, illustrated by a primary V 5+ component, is prevented by the TiO x layer in the capped film. The capped film further exhibits a decrease in Sr surface phases. These results demonstrate the importance and potential of such capping layers in preserving the bulk properties of correlated oxides in their NSR, enabling more accurate probes for their underlying physics and offering a route for their integration into devices.
In Mott materials strong electron correlation yields a spectrum of complex electronic structures. Recent synthesis advancements open realistic opportunities for harnessing Mott physics to design transformative devices. However, a major bottleneck in realizing such devices remains the lack of control over the electron correlation strength. This stems from the complexity of the electronic structure, which often veils the basic mechanisms underlying the correlation strength. This study presents control of the correlation strength by tuning the degree of orbital overlap using picometer‐scale lattice engineering. This study illustrates how bandwidth control and concurrent symmetry breaking can govern the electronic structure of a correlated SrVO3 model system. This study shows how tensile and compressive biaxial strain oppositely affect the SrVO3 in‐plane and out‐of‐plane orbital occupancy, resulting in the partial alleviation of the orbital degeneracy. The spectral weight redistribution under strain is derived and explained, which illustrates how high tensile strain drives the system toward a Mott insulating state. Implementation of such concepts can push correlated electron phenomena closer toward new solid‐state devices and circuits. These findings therefore pave the way for understanding and controlling electron correlation in a broad range of functional materials, driving this powerful resource for novel electronics closer toward practical realization.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
Copyright © 2025 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.