Maria Hilse

Pennsylvania State University

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Roman Engel‐Herbert

Forschungsverbund Berlin

J. Herfort

Forschungsverbund Berlin

Lutz Geelhaar

Paul Drude Institute for Solid State Electronics

Stephanie Law

University of Delaware

Derrick Liu

NeuroNascent (United States)

B. Jenichen

Paul Drude Institute for Solid State Electronics

Steffen Breuer

Fraunhofer Institute for Telecommunications, Heinrich Hertz Institute

H. Riechert

École Polytechnique

A. Trampert

Paul Drude Institute for Solid State Electronics

F. C. Peiris

Kenyon College

Cooperative Institutions

Pennsylvania State University

Paul Drude Institute for Solid State Electronics

Forschungsverbund Berlin

Georgia Institute of Technology

Massachusetts Institute of Technology

University of Illinois Urbana-Champaign

Cornell University

Millennium Engineering and Integration (United States)

National Institute of Standards and Technology

The Ohio State University

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Molecular beam epitaxy of PtSe₂ using a co-deposition approach

2D Materials (2022)

Maria Hilse Ke Wang Roman Engel‐Herbert

Abstract The structural properties of co-deposited ultrathin PtSe 2 films grown at low temperatures by molecular beam epitaxy on c-plane Al 2 O 3 are studied. By simultaneously supplying a Se flux from a Knudsen cell and Pt atoms from an electron-beam evaporator, crystalline (001)-oriented PtSe 2 films were formed between 200 °C and 300 °C. The long separation between substrate and electron beam evaporator of about 60 cm ensured minimal thermal load. At optimum deposition temperatures, a ten times or even higher supply rate of Se compared to Pt ensured that the pronounced volatility of the Se was compensated and the PtSe 2 phase was formed and stabilized at the growth front. Postgrowth anneals under a Se flux was found to dramatically improve the crystalline quality of the films. Even before the postgrowth anneal in Se, the crystallinity of PtSe 2 films grown with the co-deposition method was superior to films realized by thermal assisted conversion. Postgrowth annealed films showed Raman modes with narrower peaks and more than twice the intensity. Transmission electron microscopy investigations revealed that the deposited material transitioned to a two-dimensional layered structure only after the postgrowth anneal. PtSe 2 growth was found to start as single layer islands that preferentially nucleated at atomic steps of the substrate and progressed in a layer-by-layer like fashion. A close to ideal wetting behavior resulted in coalesced PtSe 2 films after depositing about 1.5 PtSe 2 layers. Detailed Raman investigation of the observed PtSe 2 layer breathing modes of films grown under optimized co-deposition conditions revealed an interlayer coupling force constant of 5.0–5.6 × 10 19 N m −3 .

Wetting layer

10.1088/2053-1583/ac606f

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Citations (2)

GaAs-Fe3Si Semiconductor–Ferromagnet Core–Shell Nanowires for Spintronics

Maria Hilse B. Jenichen J. Herfort

This chapter presents an overview of the fabrication and properties of such GaAs-Fe3Si Semiconductor–ferromagnet core–shell nanowires (SFCSNW). SFCSNW hybrid structures were grown by molecular beam epitaxy and analyzed by scanning and transmission electron microscopy, X-ray diffraction, Mossbauer spectroscopy, superconducting quantum interference device magnetometry, and magnetic force microscopy. SFCSNW with a high-quality ferromagnet like the binary Heusler alloy Fe3Si are regarded as promising candidates to enable the fabrication of new forward-looking devices in the field of spintronics and magnetic recording. Spintronics is based on the generation, manipulation, and detection of spin-polarized currents. Among other techniques for generation and detection, all-electrical spin-injection and detection is regarded as the only technique that is suitable for large-scale device production. Scanning electron microscopy images of as-grown SFCSNWs and close-up images of the middle part of single NW. Magnetization of the SFCSNWs oriented perpendicular to the substrate forming nano-bar magnets can indeed be achieved.

10.1201/9781315364407-7

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Incorporation of the dopants Si and Be into GaAs nanowires

Applied Physics Letters (2010)

Maria Hilse M. Ramsteiner Steffen Breuer Lutz Geelhaar H. Riechert

We studied the doping with Si and Be of GaAs nanowires (NWRs) grown by molecular beam epitaxy. Regarding the NW morphology, no influence was observed for Si doping but high Be doping concentrations cause a kinking and tapering of the NWRs. We investigated local vibrational modes by means of resonant Raman scattering to determine the incorporation sites of the dopant atoms. For Si doping, both donors on Ga sites and acceptors on As sites have been observed. Be was found to be incorporated as an acceptor on Ga sites. However, at high doping concentration, Be is also incorporated on interstitial sites.

Acceptor

10.1063/1.3428358

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Review of Nanolayered Post-transition Metal Monochalcogenides: Synthesis, Properties, and Applications

ACS Applied Nano Materials (2024)

Mingyu Yu Maria Hilse Qihua Zhang Yongchen Liu Zhengtianye Wang

Nanolayered post-transition metal monochalcogenides (PTMMCs) stand out as promising advanced two-dimensional (2D) materials. Beyond inheriting the general advantages associated with traditional 2D materials, they exhibit unique properties, including a wide bandgap range covering the ultraviolet to the mid-infrared spectral ranges, thickness-dependent bandgap behaviors, good nonlinear optical performance, high thermoelectric coefficients, and ferroelectricity. Consequently, these materials hold significant potential in diverse applications such as photodetectors, field effect transistors, thermoelectrics, ferroelectrics, photovoltaics, and electrochemical devices, especially in the manufacturing of nanoscale devices. However, there is still a lack of systematic understanding of the PTMMC family. This study provides a broad overview of the crystal structures, bandgap structures, synthesis methods, physical properties, and state-of-the-art applications of PTMMC materials with a motif of X-M-M-X (M=Ga, In, Ge, Sn; X=S, Se, Te). An outlook for the development trends is emphasized at the end, underscoring the critical importance of this work to the future exploration of nanolayered PTMMCs.

10.1021/acsanm.3c05984

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Growth Conditions and Interfacial Misfit Array in SnTe (111) Films Grown on InP (111)A Substrates by Molecular Beam Epitaxy

ACS Applied Materials & Interfaces (2024)

Qihua Zhang Maria Hilse Wesley Auker Jennifer L. Gray Stephanie Law

Tin telluride (SnTe) is an IV–VI semiconductor with a topological crystalline insulator band structure, high thermoelectric performance, and in-plane ferroelectricity. Despite its many applications, there has been little work focused on understanding the growth mechanisms of SnTe thin films. In this manuscript, we investigate the molecular beam epitaxy synthesis of SnTe (111) thin films on InP (111)A substrates. We explore the effect of substrate temperature, Te/Sn flux ratio, and growth rate on the film quality. Using a substrate temperature of 340 °C, a Te/Sn flux ratio of 3, and a growth rate of 0.48 Å/s, fully coalesced and single crystalline SnTe (111) epitaxial layers with X-ray rocking curve full-width-at-half-maxima of 0.09° and root-mean-square surface roughness as low as 0.2 nm have been obtained. Despite the 7.5% lattice mismatch between the SnTe (111) film and the InP (111)A substrate, reciprocal space mapping indicates that the 15 nm SnTe layer is fully relaxed. We show that a periodic interfacial misfit (IMF) dislocation array forms at the SnTe/InP heterointerface, where each IMF dislocation is separated by 14 InP lattice sites/13 SnTe lattice sites, providing rapid strain relaxation and yielding the high quality SnTe layer. This is the first report of an IMF array forming in a rock-salt on zinc-blende material system and at an IV–VI on III–V heterointerface, and highlights the potential for SnTe as a buffer layer for epitaxial telluride film growth. This work represents an important milestone in enabling the heterointegration between IV–VI and III–V semiconductors to create multifunctional devices.

Mosaicity

10.1021/acsami.4c10296

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Vapor-liquid-solid nucleation of GaAs on Si(111): Growth evolution from traces to nanowires

Physical Review B (2010)

Steffen Breuer Maria Hilse A. Trampert Lutz Geelhaar H. Riechert

GaAs nanowires were grown on Si(111) substrates by molecular-beam epitaxy employing Au droplets for the vapor-liquid-solid mechanism. The nucleation happens in three stages, which coincide with the abundance of one of three different GaAs manifestations: first Au-induced lateral traces, then three-dimensional islands, and finally Au-induced vertical nanowires. During deposition of the first 7 ML of GaAs no nanowires grew. By reflection high-energy electron diffraction and transmission electron microscopy, the crystal structure of the GaAs manifestations was examined. Traces and islands adopted the zinc-blende crystal structure and include twins, while nanowires grew in the hexagonal wurtzite structure. The delay in nanowire formation was observed to increase for higher growth temperatures. The gradual covering of the Si by GaAs was comparable to the case of Au-free growth and appears to be linked with the evolution from trace to nanowire growth. During trace formation, Au droplets kept in contact with the Si substrate and were pushed sideways by precipitating GaAs. The nucleation stages could thus be explained by considering that any Au droplet created a trace while in contact with the Si surface and a nanowire after having been pushed onto GaAs. This mechanism of trace growth was explained by the lower interface energy of liquid Au droplets on Si when compared with that on GaAs, as supported by numerical estimates.

Wurtzite crystal structure

Vapor–liquid–solid method

Crystal (programming language)

10.1103/physrevb.82.075406

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Citations (42)

Growth of 2D semiconductors and topological insulators

Elsevier eBooks (2024)

Maria Hilse Nicholas Trainor Andrew R. Graves Run Xiao Max Stanley

Topological insulator

10.1016/b978-0-323-96027-4.00031-0

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Real structure of lattice matched GaAs–Fe3Si core–shell nanowires

Journal of Crystal Growth (2014)

B. Jenichen Maria Hilse J. Herfort A. Trampert

Vapor–liquid–solid method

Faceting

10.1016/j.jcrysgro.2014.10.017

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Citations (6)

Spectroscopic ellipsometry as an in-situ monitoring tool for Bi2Se3 films grown by molecular beam epitaxy

Journal of Crystal Growth (2021)

Maria Hilse Xiaoyu Wang Phoebe Killea F. C. Peiris Roman Engel‐Herbert

Ellipsometry

10.1016/j.jcrysgro.2021.126177

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Measuring and Then Eliminating Twin Domains in SnSe Thin Films Using Fast Optical Metrology and Molecular Beam Epitaxy

ACS Nano (2022)

Wouter Mortelmans Maria Hilse Qian Song Seong Soon Jo Kevin Ye

van der Waals (vdW) layered chalcogenides have strongly direction-dependent (i.e., anisotropic) properties that make them interesting for photonic and optoelectronic applications. Orthorhombic tin selenide (α-SnSe) is a triaxial vdW material with strong optical anisotropy within layer planes, which has motivated studies of optical phase and domain switching. As with every vdW material, controlling the orientation of crystal domains during growth is key to reliably making wafer-scale, high-quality thin films, free from twin boundaries. Here, we demonstrate a fast optical method to quantify domain orientation in SnSe thin films made by molecular beam epitaxy (MBE). The in-plane optical anisotropy results in white-light being reflected into distinct colors for certain optical polarization angles and the color depends on domain orientation. We use our method to confirm a high density of twin boundaries in SnSe epitaxial films on MgO substrates, with square symmetry that results in degeneracy between SnSe 90° domain orientations. We then demonstrate that growing on a-plane sapphire, with rectangular lattice-matched symmetry that breaks the SnSe domain degeneracy, results in single-crystalline films with one preferred orientation. Our SnSe bottom-up film synthesis by MBE enables future applications of this vdW material that is particularly difficult to process by top-down methods. Our optical metrology is fast and can apply to all triaxial vdW materials.

10.1021/acsnano.2c02459

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Citations (5)