A5050780872- Electronic and Structural Properties of Oxides
- Semiconductor materials and devices
- Ferroelectric and Piezoelectric Materials
- ZnO doping and properties
- Magnetic and transport properties of perovskites and related materials
- Advanced Condensed Matter Physics
- Multiferroics and related materials
- Copper-based nanomaterials and applications
- Graphene research and applications
- Gas Sensing Nanomaterials and Sensors
- Ga2O3 and related materials
- MXene and MAX Phase Materials
- 2D Materials and Applications
- Surface and Thin Film Phenomena
- Catalytic Processes in Materials Science
- Force Microscopy Techniques and Applications
- Nanowire Synthesis and Applications
- Machine Learning in Materials Science
- Molecular Junctions and Nanostructures
- Advanced Materials Characterization Techniques
- Advanced Photocatalysis Techniques
- Perovskite Materials and Applications
- Photorefractive and Nonlinear Optics
- High-Temperature Coating Behaviors
- Luminescence Properties of Advanced Materials
Cornell University
2019-2024
Interface (United States)
2019-2024
University of St Andrews
2022
University of Virginia
2017-2021
The concept of remote epitaxy involves a two-dimensional van der Waals layer covering the substrate surface, which still enable adatoms to follow atomic motif underlying substrate. mode growth must be carefully defined as defects, e.g., pinholes, in materials can allow direct from substrate, which, combination with lateral epitaxial overgrowth, could also form an epilayer. Here, we show several unique cases that only observed for epitaxy, distinguishable other material-based mechanisms. We...
Ferroelectric nanomaterials offer the promise of switchable electronic properties at surface, with implications for photo- and electrocatalysis. Studies to date on effect ferroelectric surfaces in electrocatalysis have been primarily limited nanoparticle systems where complex interfaces arise. Here, we use MBE-grown epitaxial BaTiO3 thin films atomically sharp as model demonstrate polarization structure, intermediate binding energy, electrochemical activity toward hydrogen evolution reaction...
Strain-engineering is a powerful means to tune the polar, structural, and electronic instabilities of incipient ferroelectrics. KTaO3 near polar instability shows anisotropic superconductivity in electron-doped samples. Here, we demonstrate growth high-quality thin films by molecular-beam epitaxy. Tantalum was provided either suboxide source emanating TaO2 flux from Ta2O5 contained conventional effusion cell or an electron-beam-heated tantalum source. Excess potassium combination ozone...
We report the in situ, direct epitaxial synthesis of (0001)-oriented PdCoO2 thin films on c-plane sapphire using ozone-assisted molecular-beam epitaxy. The resulting have smoothness, structural perfection, and electrical characteristics that rival best situ grown literature. Metallic conductivity is observed as ∼2.0 nm. contain 180° in-plane rotation twins. Scanning transmission electron microscopy reveals growth (0001) surface Al2O3 begins with CoO2 layer.
In an effort to discover a high-mobility p-type oxide, recent computational studies have focused on Sn2+-based ternary oxides. Ta2SnO6 has been suggested as potentially useful material based the prediction of simultaneously high hole mobility and wide range synthesis conditions over which it is energetically favored phase. this study, we synthesized epitaxially for first time evaluated its properties experimentally. We measured band gap be 2.4 eV attempted substitutionally dope titanium...
The growing interest in the growth and study of thin films low-dimensional metallic delafossites, with general formula ABO2, is driven by their potential to exhibit electronic magnetic characteristics that are not accessible bulk systems. layered structure these compounds introduces unique surface states as well structural reconstructions, making investigation behavior pivotal understanding intrinsic structure. In this work, we phenomena epitaxially grown PtCoO2, PdCoO2, PdCrO2 films,...
Abstract Strong coupling between polarization ( P ) and strain (ɛ) in ferroelectric complex oxides offers unique opportunities to dramatically tune their properties. Here colossal tuning of ferroelectricity epitaxial KNbO 3 thin films grown by sub‐oxide molecular beam epitaxy is demonstrated. While bulk exhibits three transitions a Curie temperature T c ≈676 K, phase‐field modeling predicts that biaxial as little −0.6% pushes its > 975 decomposition air, for −1.4% strain, 1325 melting...
When it comes to providing the unusual combination of optical transparency, $p$-type conductivity, and relatively high mobility, ${\mathrm{Sn}}^{2+}$-based oxides are promising candidates. Epitaxial films simplest ${\mathrm{Sn}}^{2+}$ oxide, SnO, grown in an adsorption-controlled regime at $380{\phantom{\rule{0.16em}{0ex}}}^{\ensuremath{\circ}}\mathrm{C}$ on ${\mathrm{Al}}_{2}{\mathrm{O}}_{3}$ substrates by molecular-beam epitaxy, where excess volatile ${\mathrm{SnO}}_{x}$ desorbs from film...
Homologous series are layered phases that can have a range of stoichiometries depending on an index n. Examples perovskite-related homologous include (ABO3)nAO Ruddlesden–Popper and (Bi2O2) (An−1BnO3n+1) Aurivillius phases. It is challenging to precisely control n because other members the similar stoichiometry phase with desired degenerate in energy syntactic intergrowths among values; this challenge amplified as increases. To improve ability synthesize targeted precise atomic layering, we...
Molecular-beam epitaxy (MBE) is the gold standard for epitaxial growth of complex oxides with best material properties as determined by respective figures merit. Unfortunately, once more than one cation involved in desired, MBE often becomes plagued difficulties stoichiometry control. Instead relying on a quartz crystal microbalance to measure fluxes individual molecular beams, which lacks accuracy, or reflection high-energy electron diffraction oscillations targeted multication oxide...
Contact Resistance (RC) is a major limiting factor in the performance of graphene devices.RC sensitive to quality interface and composition contact, which are affected by transfer process contact deposition conditions.In this work, linear correlation observed between Ti contacts, characterized X-ray photoelectron spectroscopy, Ti/graphene (Gr) resistance measured length method.We find that tunable via rate base pressure.Reactor pressure found effect resultant resistance.The conditions on...
Remote epitaxy is taking center stage in creating freestanding complex oxide thin films with high crystallinity that could serve as an ideal building block for stacking artificial heterostructures distinctive functionalities. However, there exist technical challenges, particularly the remote of perovskite oxides associated their harsh growth environments, making graphene interlayer difficult to survive. Transferred graphene, typically used a template, poses limitations ensuring yield films,...
TbScO3 is a wide bandgap semiconductor with potential applications in charge trap memory devices and acts as an alternate gate dielectric fully depleted transistors also substrate for epitaxial thin film growth. has orthorhombic crystal structure, which gives rise to optical anisotropy. Generalized ellipsometric spectra are measured multiple in-plane rotations of (110) (001) oriented single crystals over photon energy range 0.7–8.5 eV determine the complex function (ε = ε1 + iε2) electric...
Abstract To understand the atomistic phenomenon behind initial oxidation processes, we have studied nanoscale evolution of oxide growth prior to formation a complete layer on Ni–15 wt%Cr(100) alloy surface using scanning tunneling microscopy/spectroscopy (STM/STS). At onset oxidation, NiO superlattice forms wedges across step edges, eventually growing terraces. The completion is followed by nucleation next layer, which always commences at groove site superlattice. Cr-oxide initiates as...
We outline a method to synthesize (ATiO3)nAO Ruddlesden–Popper phases with high-n, where the A-site is mixture of barium and strontium, by molecular-beam epitaxy. The precision consistency described demonstrated growth an unprecedented (SrTiO3)50SrO epitaxial film. proceed investigate incorporation into structure, which limited few percent in bulk, we find that amount can be incorporated depends on both substrate temperature strain state At optimal temperature, demonstrate as much 33%...
Ferroelectric nanomaterials are of interest in catalysis, nonvolatile memory, and neuromorphic computing among other applications because their switchable structure that can alter the electronic interface properties a single material. The investigation role polarization on surface chemistry ferroelectric is longstanding challenge, as it ideally requires combination both nanoscale imaging chemical spectroscopy. In this work, we study model BaTiO3 thin film by synchrotron X-ray scanning...
The low dielectric loss underlying the record performance of strained (SrTiO3)nSrO Ruddlesden–Popper films as tunable microwave dielectrics was postulated to arise from (SrO)2 faults accommodating local non-stoichiometric defects. Here, we explore effect non-stoichiometry on using positron annihilation lifetime spectroscopy a composition series 300 nm thick n = 6 (Sr1+δTiO3)nSrO thin films. These show titanium-site vacancies across stoichiometry series, with evidence that TiOx vacancy...
The Ruddlesden–Popper (An+1BnO3n+1) compounds are highly tunable materials whose functional properties can be dramatically impacted by their structural phase n. negligible differences in formation energies for different n produce local variations arising from small stoichiometric deviations. Here, we present a Python analysis platform to detect, measure, and quantify the presence of n-phases based on atomic-resolution scanning transmission electron microscopy (STEM) images. We employ image...
We systematically investigate the role of defects, introduced by varying synthesis conditions and carrying out ion irradiation treatments, on structural ferroelectric properties commensurately strained bismuth ferrite BixFe2−xO3 layers grown SrRuO3-coated DyScO3(110)o substrates using adsorption-controlled ozone molecular-beam epitaxy. Our findings highlight as an effective approach for reducing through-layer electrical leakage, a necessary condition development reliable ferroelectrics-based...
Over the past decade, it has become apparent that extreme sensitivity of 2D crystals to surface interactions presents a unique opportunity tune material properties through functionalization and mechanical assembly heterostructures. However, this carries with concurrent challenge: an enhanced contamination introduced by standard patterning techniques is exacerbated difficulty in cleaning these atomically thin materials. Here, we report templated MoS2 growth technique wherein Mo deposited onto...
We demonstrate the epitaxial growth of first two members, and n=∞ member homologous Ruddlesden–Popper series Ban+1InnO2.5n+1 which n=1 was previously unknown. The films were grown by suboxide molecular-beam epitaxy where indium is provided a molecular beam indium-suboxide [In2O (g)]. To facilitate ex situ characterization highly hygroscopic barium indate films, capping layer amorphous SiO2 deposited prior to air exposure. structural quality assessed x-ray diffraction, reflective high-energy...
Utilizing the powerful combination of molecular-beam epitaxy (MBE) and angle-resolved photoemission spectroscopy (ARPES), we produce study effect different terminating layers on electronic structure metallic delafossite PdCoO2. Attempts to introduce unpaired electrons synthesize new antiferromagnetic metals akin isostructural compound PdCrO2 have been made by replacing cobalt with iron in PdCoO2 films grown MBE. Using ARPES, observe similar bulk bands these Pd-, CoO2-, FeO2-termination....
Abstract It has been suggested that Ba 3 In 2 O 6 might be a high- T c superconductor. Experimental investigation of the properties was long inhibited by its instability in air. Recently epitaxial with protective capping layer demonstrated, which finally allows electronic characterization. The optical bandgap is determined to 2.99 eV in-the (001) plane and 2.83 along -axis direction spectroscopic ellipsometry. First-principles calculations were carried out, yielding result good agreement...
Generalized ellipsometry measurements are used to extract the complex dielectric function (ε=ε1+iε2) spectra of GdScO3 single crystals over 0.7–8.5 eV photon energy range. is a wide bandgap semiconductor with high constant, and potential applications include replacing SiO2 in silicon-based transistors as an epitaxial substrate for thin film growth. This work presents anisotropic optical properties electric fields oscillating parallel a-, b-, c-crystallographic axes. A direct identified at...