1
|
Tian Y, Yang D, Ma Y, Li Z, Li J, Deng Z, Tian H, Yang H, Sun S, Li J. Spatiotemporal Visualization of Photogenerated Carriers on an Avalanche Photodiode Surface Using Ultrafast Scanning Electron Microscopy. NANOMATERIALS (BASEL, SWITZERLAND) 2024; 14:310. [PMID: 38334581 PMCID: PMC10857202 DOI: 10.3390/nano14030310] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/21/2023] [Revised: 01/25/2024] [Accepted: 01/30/2024] [Indexed: 02/10/2024]
Abstract
The spatiotemporal evolution of photogenerated charge carriers on surfaces and at interfaces of photoactive materials is an important issue for understanding fundamental physical processes in optoelectronic devices and advanced materials. Conventional optical probe-based microscopes that provide indirect information about the dynamic behavior of photogenerated carriers are inherently limited by their poor spatial resolution and large penetration depth. Herein, we develop an ultrafast scanning electron microscope (USEM) with a planar emitter. The photoelectrons per pulse in this USEM can be two orders of magnitude higher than that of a tip emitter, allowing the capture of high-resolution spatiotemporal images. We used the contrast change of the USEM to examine the dynamic nature of surface carriers in an InGaAs/InP avalanche photodiode (APD) after femtosecond laser excitation. It was observed that the photogenerated carriers showed notable longitudinal drift, lateral diffusion, and carrier recombination associated with the presence of photovoltaic potential at the surface. This work demonstrates an in situ multiphysics USEM platform with the capability to stroboscopically record carrier dynamics in space and time.
Collapse
Affiliation(s)
- Yuan Tian
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China; (Y.T.); (D.Y.); (Y.M.); (Z.L.); (J.L.); (Z.D.); (H.T.); (H.Y.); (S.S.)
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Dong Yang
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China; (Y.T.); (D.Y.); (Y.M.); (Z.L.); (J.L.); (Z.D.); (H.T.); (H.Y.); (S.S.)
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Yu Ma
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China; (Y.T.); (D.Y.); (Y.M.); (Z.L.); (J.L.); (Z.D.); (H.T.); (H.Y.); (S.S.)
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Zhongwen Li
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China; (Y.T.); (D.Y.); (Y.M.); (Z.L.); (J.L.); (Z.D.); (H.T.); (H.Y.); (S.S.)
| | - Jun Li
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China; (Y.T.); (D.Y.); (Y.M.); (Z.L.); (J.L.); (Z.D.); (H.T.); (H.Y.); (S.S.)
| | - Zhen Deng
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China; (Y.T.); (D.Y.); (Y.M.); (Z.L.); (J.L.); (Z.D.); (H.T.); (H.Y.); (S.S.)
| | - Huanfang Tian
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China; (Y.T.); (D.Y.); (Y.M.); (Z.L.); (J.L.); (Z.D.); (H.T.); (H.Y.); (S.S.)
| | - Huaixin Yang
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China; (Y.T.); (D.Y.); (Y.M.); (Z.L.); (J.L.); (Z.D.); (H.T.); (H.Y.); (S.S.)
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Shuaishuai Sun
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China; (Y.T.); (D.Y.); (Y.M.); (Z.L.); (J.L.); (Z.D.); (H.T.); (H.Y.); (S.S.)
- Songshan Lake Materials Laboratory, Dongguan 523808, China
| | - Jianqi Li
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China; (Y.T.); (D.Y.); (Y.M.); (Z.L.); (J.L.); (Z.D.); (H.T.); (H.Y.); (S.S.)
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100049, China
- Songshan Lake Materials Laboratory, Dongguan 523808, China
| |
Collapse
|
2
|
Wang L, Wang H, Nughays R, Ogieglo W, Yin J, Gutiérrez-Arzaluz L, Zhang X, Wang JX, Pinnau I, Bakr OM, Mohammed OF. Phonon-driven transient bandgap renormalization in perovskite single crystals. MATERIALS HORIZONS 2023; 10:4192-4201. [PMID: 37431707 DOI: 10.1039/d3mh00570d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/12/2023]
Abstract
Tailoring the electronic structure of perovskite materials on ultrafast timescales is expected to shed light on optimizing optoelectronic applications. However, the transient bandgap renormalization observed upon photoexcitation is commonly explained by many-body interactions of optically created electrons and holes, which shrink the original bandgap by a few tens of millielectronvolts with a sub-picosecond time constant, while the accompanying phonon-induced effect remains hitherto unexplored. Here we unravel a significant contribution of hot phonons in the photo-induced transient bandgap renormalization in MAPbBr3 single crystals, as evidenced by asymmetric spectral evolutions and transient reflection spectral shifts in the picosecond timescale. Moreover, we performed a spatiotemporal study upon optical excitation with time-resolved scanning electron microscopy and identified that the surface charge carrier diffusion and transient bandgap renormalization are strongly correlated in time. These findings highlight the need to re-evaluate current theories on photo-induced bandgap renormalization and provide a new approach for precisely controlling the optical and electronic properties of perovskite materials, enabling the design and fabrication of high-performance optoelectronic devices with exceptional efficiency and unique properties.
Collapse
Affiliation(s)
- Lijie Wang
- Advanced Membranes and Porous Materials Centre (AMPM), Division of Physical Science and Engineering, King Abdullah University of Science and Technology, Thuwal 23955-6900, Kingdom of Saudi Arabia.
| | - Hong Wang
- Advanced Membranes and Porous Materials Centre (AMPM), Division of Physical Science and Engineering, King Abdullah University of Science and Technology, Thuwal 23955-6900, Kingdom of Saudi Arabia.
- KAUST Catalysis Centre, Division of Physical Sciences and Engineering, King Abdullah University of Science and Technology, Thuwal 23955-6900, Kingdom of Saudi Arabia
| | - Razan Nughays
- Advanced Membranes and Porous Materials Centre (AMPM), Division of Physical Science and Engineering, King Abdullah University of Science and Technology, Thuwal 23955-6900, Kingdom of Saudi Arabia.
| | - Wojciech Ogieglo
- Advanced Membranes and Porous Materials Centre (AMPM), Division of Physical Science and Engineering, King Abdullah University of Science and Technology, Thuwal 23955-6900, Kingdom of Saudi Arabia.
| | - Jun Yin
- Department of Applied Physics, The Hong Kong Polytechnic University, Kowloon 999077, Hong Kong, P. R. China
| | - Luis Gutiérrez-Arzaluz
- Advanced Membranes and Porous Materials Centre (AMPM), Division of Physical Science and Engineering, King Abdullah University of Science and Technology, Thuwal 23955-6900, Kingdom of Saudi Arabia.
- KAUST Catalysis Centre, Division of Physical Sciences and Engineering, King Abdullah University of Science and Technology, Thuwal 23955-6900, Kingdom of Saudi Arabia
| | - Xinyuan Zhang
- KAUST Catalysis Centre, Division of Physical Sciences and Engineering, King Abdullah University of Science and Technology, Thuwal 23955-6900, Kingdom of Saudi Arabia
| | - Jian-Xin Wang
- Advanced Membranes and Porous Materials Centre (AMPM), Division of Physical Science and Engineering, King Abdullah University of Science and Technology, Thuwal 23955-6900, Kingdom of Saudi Arabia.
| | - Ingo Pinnau
- Advanced Membranes and Porous Materials Centre (AMPM), Division of Physical Science and Engineering, King Abdullah University of Science and Technology, Thuwal 23955-6900, Kingdom of Saudi Arabia.
| | - Osman M Bakr
- KAUST Catalysis Centre, Division of Physical Sciences and Engineering, King Abdullah University of Science and Technology, Thuwal 23955-6900, Kingdom of Saudi Arabia
| | - Omar F Mohammed
- Advanced Membranes and Porous Materials Centre (AMPM), Division of Physical Science and Engineering, King Abdullah University of Science and Technology, Thuwal 23955-6900, Kingdom of Saudi Arabia.
- KAUST Catalysis Centre, Division of Physical Sciences and Engineering, King Abdullah University of Science and Technology, Thuwal 23955-6900, Kingdom of Saudi Arabia
| |
Collapse
|
3
|
Garming MWH, Bolhuis M, Conesa-Boj S, Kruit P, Hoogenboom JP. Lock-in Ultrafast Electron Microscopy Simultaneously Visualizes Carrier Recombination and Interface-Mediated Trapping. J Phys Chem Lett 2020; 11:8880-8886. [PMID: 32909435 PMCID: PMC7569669 DOI: 10.1021/acs.jpclett.0c02345] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2020] [Accepted: 09/10/2020] [Indexed: 06/11/2023]
Abstract
Visualizing charge carrier flow over interfaces or near surfaces meets great challenges concerning resolution and vastly different time scales of bulk and surface dynamics. Ultrafast or four-dimensional scanning electron microscopy (USEM) using a laser pump electron probe scheme circumvents the optical diffraction limit, but disentangling surface-mediated trapping and ultrafast carrier dynamics in a single measurement scheme has not yet been demonstrated. Here, we present lock-in USEM, which simultaneously visualizes fast bulk recombination and slow trapping. As a proof of concept, we show that the surface termination on GaAs, i.e., Ga or As, profoundly influences ultrafast movies. We demonstrate the differences can be attributed to trapping-induced surface voltages of approximately 100-200 mV, which is further supported by secondary electron particle tracing calculations. The simultaneous visualization of both competing processes opens new perspectives for studying carrier transport in layered, nanostructured, and two-dimensional semiconductors, where carrier trapping constitutes a major bottleneck for device efficiency.
Collapse
Affiliation(s)
- Mathijs W. H. Garming
- Department
of Imaging Physics, Delft University of
Technology, 2628 CN Delft, The Netherlands
| | - Maarten Bolhuis
- Kavli
Institute of Nanoscience, Delft University
of Technology, 2628 CJ Delft, The Netherlands
| | - Sonia Conesa-Boj
- Kavli
Institute of Nanoscience, Delft University
of Technology, 2628 CJ Delft, The Netherlands
| | - Pieter Kruit
- Department
of Imaging Physics, Delft University of
Technology, 2628 CN Delft, The Netherlands
| | - Jacob P. Hoogenboom
- Department
of Imaging Physics, Delft University of
Technology, 2628 CN Delft, The Netherlands
| |
Collapse
|
4
|
Zhao J, Bakr OM, Mohammed OF. Ultrafast electron imaging of surface charge carrier dynamics at low voltage. STRUCTURAL DYNAMICS (MELVILLE, N.Y.) 2020; 7:021001. [PMID: 32266302 PMCID: PMC7105398 DOI: 10.1063/4.0000007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/07/2020] [Accepted: 03/10/2020] [Indexed: 06/11/2023]
Abstract
The performance of optoelectronic devices strongly depends on charge carrier dynamics on top of surfaces of the absorber layers. Unfortunately, this information cannot be selectively probed using conventional ultrafast laser spectroscopic methods, due to the large penetration depth (tens of nm to μm) of the photon pulses in the pump-probe configurations. Therefore, ultrafast time-resolved approaches that can directly and selectively visualize the behavior of the surface carrier dynamics are urgently needed. Here, we introduce a novel methodology of low-voltage scanning ultrafast electron microscopy that can take ultrafast time-resolved images (snapshots) of the surface of materials at the sub-nanometer level. By this approach, the surface of the photoactive materials is optically excited and imaged, using a pulsed low-voltage electron beam (1 keV) that interacts with the surface to generate secondary electrons with an energy of a few eV, and that are emitted only from the top surface of materials, providing direct information about the carrier dynamics and the localization of electron/holes in real space and time. An outlook on the potential applications of this low voltage approach in different disciplines will also be discussed.
Collapse
Affiliation(s)
- Jianfeng Zhao
- Division of Physical Science and Engineering, King Abdullah University of Science and Technology, Thuwal 23955-6900, Saudi Arabia
| | - Osman M Bakr
- Division of Physical Science and Engineering, King Abdullah University of Science and Technology, Thuwal 23955-6900, Saudi Arabia
| | - Omar F Mohammed
- Division of Physical Science and Engineering, King Abdullah University of Science and Technology, Thuwal 23955-6900, Saudi Arabia
| |
Collapse
|
5
|
Shaheen BS, El-Zohry AM, Zhao J, Yin J, Hedhili MN, Bakr OM, Mohammed OF. Real-Space Mapping of Surface-Oxygen Defect States in Photovoltaic Materials Using Low-Voltage Scanning Ultrafast Electron Microscopy. ACS APPLIED MATERIALS & INTERFACES 2020; 12:7760-7767. [PMID: 31951364 DOI: 10.1021/acsami.9b20215] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Ultrathin layers of native oxides on the surface of photovoltaic materials may act as very efficient carrier trapping/recombination centers, thus significantly affecting their interfacial photophysical properties. How ultrathin oxide layers affect the surface and interface carrier dynamics cannot be selectively accessed by conventional ultrafast transient spectroscopic methods due to the deep penetration depth (tens to thousands of nanometers) of the pump/probe laser pulses. Herein, scanning ultrafast electron microscopy (S-UEM) at a low voltage of 1 keV electrons was recently developed at KAUST to selectively map the ultrafast charge carrier dynamics of a few layers on the top surfaces of photovoltaic materials. Unlike high-voltage 30 keV experiments, at 1 keV, the depth of detected secondary electrons (SEs) underneath the surface is significantly reduced 5 times, thus making it possible to visualize the dynamics of charge carrier from the uppermost surface of photoactive layers. More specifically, this new approach has been employed to explore and decipher the tremendous impact of native oxide layers and oxygen defect states on charge carrier dynamics in space and time simultaneously at sub-nanometer levels on several photovoltaic material surfaces, including Si, GaAs, CdTe, and CdZnTe single crystals. Interestingly, the contrast in the SEs time-resolved difference images switched from a dark "energy-loss mechanism" to a bright "energy-gain mechanism" only by removing the layers of surface oxides. Moreover, the charge carrier recombination was estimated and found to be dramatically affected by the native oxide layers. The density functional theory (DFT) calculations demonstrate that the work function of oxygen-terminated Si surface also increases slightly upon optical excitation and makes for less SE intensity, providing another piece of evidence that the origin of the dark contrast observed on these material surfaces should be assigned to the surface oxide formation, mainly oxygen defect states in the band gap and/or work function increment. Our findings provide a new method and pave the way for evaluating the effect of surface morphology and defects, including but not limited to native oxide, on charge carrier dynamics, and interfacial properties of photovoltaic absorber layers.
Collapse
Affiliation(s)
- Basamat S Shaheen
- Division of Physical Science and Engineering , King Abdullah University of Science and Technology , Thuwal 23955-6900 , Kingdom of Saudi Arabia
| | - Ahmed M El-Zohry
- Division of Physical Science and Engineering , King Abdullah University of Science and Technology , Thuwal 23955-6900 , Kingdom of Saudi Arabia
| | - Jianfeng Zhao
- Division of Physical Science and Engineering , King Abdullah University of Science and Technology , Thuwal 23955-6900 , Kingdom of Saudi Arabia
| | - Jun Yin
- Division of Physical Science and Engineering , King Abdullah University of Science and Technology , Thuwal 23955-6900 , Kingdom of Saudi Arabia
| | - Mohamed N Hedhili
- Core Labs , King Abdullah University of Science and Technology , Thuwal 23955-6900 , Kingdom of Saudi Arabia
| | - Osman M Bakr
- Division of Physical Science and Engineering , King Abdullah University of Science and Technology , Thuwal 23955-6900 , Kingdom of Saudi Arabia
| | - Omar F Mohammed
- Division of Physical Science and Engineering , King Abdullah University of Science and Technology , Thuwal 23955-6900 , Kingdom of Saudi Arabia
| |
Collapse
|