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Cooper D, Bruas L, Bryan M, Boureau V. Measuring electrical properties in semiconductor devices by pixelated STEM and off-axis electron holography (or convergent beams vs. plane waves). Micron 2024; 179:103594. [PMID: 38340549 DOI: 10.1016/j.micron.2024.103594] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2023] [Revised: 01/24/2024] [Accepted: 01/25/2024] [Indexed: 02/12/2024]
Abstract
We demonstrate the use of both pixelated differential phase contrast (DPC) scanning transmission electron microscopy (STEM) and off-axis electron holography (EH) for the measurement of electric fields and assess the advantages and limitations of each technique when applied to technologically relevant samples. Three different types of samples are examined, firstly a simple highly-doped Si pn junction. Then a SiGe superlattice is examined to evaluate the effects of the mean inner potential on the measured signal. Finally, an InGaN/GaN microwire light-emitting diode (LED) device is examined which has a polarization field, variations of mean inner potential and a wurtzite crystal lattice. We discuss aspects such as spatial resolution and sensitivity, and the concept of pseudo-field is defined. However, the most important point is the need to limit the influence of diffraction contrast to obtain accurate measurements. In this respect, the use of a plane electron wave for EH is clearly beneficial when compared to the use of a convergent beam for pixelated DPC STEM.
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Affiliation(s)
- David Cooper
- Universite Grenoble Alpes, CEA, LETI, F-38000 Grenoble, France.
| | - Lucas Bruas
- Universite Grenoble Alpes, CEA, LETI, F-38000 Grenoble, France
| | - Matthew Bryan
- Universite Grenoble Alpes, CEA, LETI, F-38000 Grenoble, France
| | - Victor Boureau
- Universite Grenoble Alpes, CEA, LETI, F-38000 Grenoble, France; Interdisciplinary Center for Electron Microscopy, EPFL, 1015 Lausanne, Switzerland
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2
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Grieb T, Krause FF, Mehrtens T, Mahr C, Gerken B, Schowalter M, Freitag B, Rosenauer A. GaN atomic electric fields from a segmented STEM detector: Experiment and simulation. J Microsc 2024. [PMID: 38372408 DOI: 10.1111/jmi.13276] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2023] [Accepted: 01/31/2024] [Indexed: 02/20/2024]
Abstract
Atomic electric fields in a thin GaN sample are measured with the centre-of-mass approach in 4D-scanning transmission electron microscopy (4D-STEM) using a 12-segmented STEM detector in a Spectra 300 microscope. The electric fields, charge density and potential are compared to simulations and an experimental measurement using a pixelated 4D-STEM detector. The segmented detector benefits from a high recording speed, which enables measurements at low radiation doses. However, there is measurement uncertainty due to the limited number of segments analysed in this study.
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Affiliation(s)
- Tim Grieb
- Institute of Solid State Physics, University of Bremen, Bremen, Germany
| | - Florian F Krause
- Institute of Solid State Physics, University of Bremen, Bremen, Germany
| | - Thorsten Mehrtens
- Institute of Solid State Physics, University of Bremen, Bremen, Germany
| | - Christoph Mahr
- Institute of Solid State Physics, University of Bremen, Bremen, Germany
| | - Beeke Gerken
- Institute of Solid State Physics, University of Bremen, Bremen, Germany
| | - Marco Schowalter
- Institute of Solid State Physics, University of Bremen, Bremen, Germany
| | - Bert Freitag
- Thermo Fisher Scientific, Eindhoven, The Netherlands
| | - Andreas Rosenauer
- Institute of Solid State Physics, University of Bremen, Bremen, Germany
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3
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Lorenzen T, März B, Xue T, Beyer A, Volz K, Bein T, Müller-Caspary K. Imaging built-in electric fields and light matter by Fourier-precession TEM. Sci Rep 2024; 14:1320. [PMID: 38225247 PMCID: PMC10789819 DOI: 10.1038/s41598-024-51423-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2023] [Accepted: 01/04/2024] [Indexed: 01/17/2024] Open
Abstract
We report the precise measurement of electric fields in nanostructures, and high-contrast imaging of soft matter at ultralow electron doses by transmission electron microscopy (TEM). In particular, a versatile method based on the theorem of reciprocity is introduced to enable differential phase contrast imaging and ptychography in conventional, plane-wave illumination TEM. This is realised by a series of TEM images acquired under different tilts, thereby introducing the sampling rate in reciprocal space as a tuneable parameter, in contrast to momentum-resolved scanning techniques. First, the electric field of a p-n junction in GaAs is imaged. Second, low-dose, in-focus ptychographic and DPC characterisation of Kagome pores in weakly scattering covalent organic frameworks is demonstrated by using a precessing electron beam in combination with a direct electron detector. The approach offers utmost flexibility to record relevant spatial frequencies selectively, while acquisition times and dose requirements are significantly reduced compared to the 4D-STEM counterpart.
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Affiliation(s)
- Tizian Lorenzen
- Department of Chemistry and Center for NanoScience, Ludwig-Maximilians-Universität München, Butenandtstr. 11, 81377, München, Germany
| | - Benjamin März
- Department of Chemistry and Center for NanoScience, Ludwig-Maximilians-Universität München, Butenandtstr. 11, 81377, München, Germany
- Louisiana State University Shared Instrumentation Facility (LSUSIF), 121 Chemistry and Materials Building, 4048 Highland Rd., Baton Rouge, LA, 70803, USA
| | - Tianhao Xue
- Department of Chemistry and Center for NanoScience, Ludwig-Maximilians-Universität München, Butenandtstr. 11, 81377, München, Germany
| | - Andreas Beyer
- Department of Physics, Philipps University Marburg, Hans-Meerwein-Straße 6, 35032, Marburg, Germany
| | - Kerstin Volz
- Department of Physics, Philipps University Marburg, Hans-Meerwein-Straße 6, 35032, Marburg, Germany
| | - Thomas Bein
- Department of Chemistry and Center for NanoScience, Ludwig-Maximilians-Universität München, Butenandtstr. 11, 81377, München, Germany
| | - Knut Müller-Caspary
- Department of Chemistry and Center for NanoScience, Ludwig-Maximilians-Universität München, Butenandtstr. 11, 81377, München, Germany.
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Heimes D, Chejarla VS, Ahmed S, Hüppe F, Beyer A, Volz K. Impact of beam size and diffraction effects in the measurement of long-range electric fields in crystalline samples via 4DSTEM. Ultramicroscopy 2023; 253:113821. [PMID: 37562100 DOI: 10.1016/j.ultramic.2023.113821] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2023] [Revised: 06/27/2023] [Accepted: 07/25/2023] [Indexed: 08/12/2023]
Abstract
Measuring long-range electric fields by 4-dimensional scanning transmission electron microscopy (4DSTEM) is on the verge to becoming an established method, though quantifying and understanding all underlying processes remains a challenge. To gain further insight into these processes, experimental studies employing the center-of-mass (COM) method of the model system of a GaAs p-n junction are carried out in which three ranges of the semi-convergence angle α are identified, with an intermediate one where measuring the built-in potential Vbi is not feasible. STEM multislice simulations including both atomic and nm-scale fields prove that this intermediate range begins once diffraction disks start overlapping with the undiffracted beam. The range ends when the diffraction disks' intensities become so low that they do not affect the measurement significantly anymore and when high-intensity diffractions overlap the center disk completely. From simulations without influence of atoms it is concluded that measuring Vbi has advantages over measuring the electric-field strength, as the potential difference does neither show a significant dependence on the beam size, nor on the specimen thickness.
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Affiliation(s)
- Damien Heimes
- Material Sciences Center and Department of Physics, Philipps-Universität Marburg, Germany
| | - Varun Shankar Chejarla
- Material Sciences Center and Department of Physics, Philipps-Universität Marburg, Germany
| | - Shamail Ahmed
- Material Sciences Center and Department of Physics, Philipps-Universität Marburg, Germany
| | - Franziska Hüppe
- Material Sciences Center and Department of Physics, Philipps-Universität Marburg, Germany
| | - Andreas Beyer
- Material Sciences Center and Department of Physics, Philipps-Universität Marburg, Germany
| | - Kerstin Volz
- Material Sciences Center and Department of Physics, Philipps-Universität Marburg, Germany.
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Chejarla VS, Ahmed S, Belz J, Scheunert J, Beyer A, Volz K. Measuring Spatially-Resolved Potential Drops at Semiconductor Hetero-Interfaces Using 4D-STEM. SMALL METHODS 2023; 7:e2300453. [PMID: 37246264 DOI: 10.1002/smtd.202300453] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/05/2023] [Indexed: 05/30/2023]
Abstract
Characterizing long-range electric fields and built-in potentials in functional materials at nano to micrometer scales is of supreme importance for optimizing devices, e.g., the functionality of semiconductor hetero-structures or battery materials is determined by the electric fields established at interfaces which can also vary spatially. In this study, momentum-resolved four-dimensional scanning transmission electron microscopy (4D-STEM) is proposed for the quantification of these potentials and the optimization steps required to reach quantitative agreement with simulations for the GaAs/AlAs hetero-junction model system are shown. Using STEM the differences in the mean inner potentials (∆MIP) of two materials forming an interface and resulting dynamic diffraction effects have to be considered. This study shows that the measurement quality is significantly improved by precession, energy filtering and a off-zone-axis alignment of the specimen. Complementary simulations yielding a ∆MIP of 1.3 V confirm that the potential drop due to charge transfer at the intrinsic interface is ≈0.1 V, in agreement with experimental and theoretical values found in literture. These results show the feasibility of accurately measuring built-in potentials across hetero-interfaces of real device structures and its promising application for more complex interfaces of other polycrystalline materials on the nanometer scale.
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Affiliation(s)
- Varun Shankar Chejarla
- Department of Physics and Materials Science Center, Philipps-University Marburg, Hans-Meerwein Str. 6, 35032, Marburg, Germany
| | - Shamail Ahmed
- Department of Physics and Materials Science Center, Philipps-University Marburg, Hans-Meerwein Str. 6, 35032, Marburg, Germany
| | - Jürgen Belz
- Department of Physics and Materials Science Center, Philipps-University Marburg, Hans-Meerwein Str. 6, 35032, Marburg, Germany
| | - Jonas Scheunert
- Department of Physics and Materials Science Center, Philipps-University Marburg, Hans-Meerwein Str. 6, 35032, Marburg, Germany
| | - Andreas Beyer
- Department of Physics and Materials Science Center, Philipps-University Marburg, Hans-Meerwein Str. 6, 35032, Marburg, Germany
| | - Kerstin Volz
- Department of Physics and Materials Science Center, Philipps-University Marburg, Hans-Meerwein Str. 6, 35032, Marburg, Germany
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da Silva BC, Sadre Momtaz Z, Monroy E, Okuno H, Rouviere JL, Cooper D, Den Hertog MI. Assessment of Active Dopants and p-n Junction Abruptness Using In Situ Biased 4D-STEM. NANO LETTERS 2022; 22:9544-9550. [PMID: 36442685 DOI: 10.1021/acs.nanolett.2c03684] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
A key issue in the development of high-performance semiconductor devices is the ability to properly measure active dopants at the nanometer scale. In a p-n junction, the abruptness of the dopant profile around the metallurgical junction directly influences the electric field. Here, a contacted nominally symmetric and highly doped (NA = ND = 9 × 1018 cm-3) silicon p-n specimen is studied through in situ biased four-dimensional scanning transmission electron microscopy (4D-STEM). Measurements of electric field, built-in voltage, depletion region width, and charge density are combined with analytical equations and finite-element simulations in order to evaluate the quality of the junction interface. It is shown that all the junction parameters measured are compatible with a linearly graded junction. This hypothesis is also consistent with the evolution of the electric field with bias as well as off-axis electron holography data. These results demonstrate that in situ biased 4D-STEM can allow a better understanding of the electrostatics of semiconductor p-n junctions with nm-scale resolution.
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Affiliation(s)
| | | | - Eva Monroy
- Université Grenoble Alpes, CEA, Grenoble INP, IRIG, PHELIQS, F-38000Grenoble, France
| | - Hanako Okuno
- Université Grenoble Alpes, CEA, IRIG, MEM, LEMMA, F-38000Grenoble, France
| | - Jean-Luc Rouviere
- Université Grenoble Alpes, CEA, IRIG, MEM, LEMMA, F-38000Grenoble, France
| | - David Cooper
- Université Grenoble Alpes, CEA-LETI, F-38000Grenoble, France
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Quantitative electric field mapping in semiconductor heterostructures via tilt-scan averaged DPC STEM. Ultramicroscopy 2022; 238:113538. [DOI: 10.1016/j.ultramic.2022.113538] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2022] [Revised: 04/14/2022] [Accepted: 04/23/2022] [Indexed: 11/23/2022]
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8
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Towards the interpretation of a shift of the central beam in nano-beam electron diffraction as a change in mean inner potential. Ultramicroscopy 2022; 236:113503. [DOI: 10.1016/j.ultramic.2022.113503] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2021] [Revised: 02/18/2022] [Accepted: 02/23/2022] [Indexed: 11/19/2022]
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