Andrew Wee
Degree: PhD
Position: Professor
Affiliation: NUS – Department of Physics
Research Type: Experiment
Office: S13 03-12
Email: phyweets@nus.edu.sg
Contact: (65) 6516 6362
Website: http://www.physics.nus.edu.sg/~phyweets/
Research Interests
Scanning tunneling microscopy (STM) and synchrotron radiation studies of the molecule-substrate interface, graphene and 2D materials, and related device studies
CA2DM Publications:
2024 |
Lu, Bin; Xia, Yuze; Ren, Yuqian; Xie, Miaomiao; Zhou, Liguo; Vinai, Giovanni; Morton, Simon A; Wee, Andrew T S; van der Wiel, Wilfred G; Zhang, Wen; Wong, Ping Kwan Johnny When Machine Learning Meets 2D Materials: A Review Journal Article ADVANCED SCIENCE, 11 (13), 2024. @article{ISI:001149703000001, title = {When Machine Learning Meets 2D Materials: A Review}, author = {Bin Lu and Yuze Xia and Yuqian Ren and Miaomiao Xie and Liguo Zhou and Giovanni Vinai and Simon A Morton and Andrew T S Wee and Wilfred G van der Wiel and Wen Zhang and Ping Kwan Johnny Wong}, doi = {10.1002/advs.202305277}, times_cited = {0}, year = {2024}, date = {2024-01-26}, journal = {ADVANCED SCIENCE}, volume = {11}, number = {13}, publisher = {WILEY}, address = {111 RIVER ST, HOBOKEN 07030-5774, NJ USA}, abstract = {The availability of an ever-expanding portfolio of 2D materials with rich internal degrees of freedom (spin, excitonic, valley, sublattice, and layer pseudospin) together with the unique ability to tailor heterostructures made layer by layer in a precisely chosen stacking sequence and relative crystallographic alignments, offers an unprecedented platform for realizing materials by design. However, the breadth of multi-dimensional parameter space and massive data sets involved is emblematic of complex, resource-intensive experimentation, which not only challenges the current state of the art but also renders exhaustive sampling untenable. To this end, machine learning, a very powerful data-driven approach and subset of artificial intelligence, is a potential game-changer, enabling a cheaper - yet more efficient - alternative to traditional computational strategies. It is also a new paradigm for autonomous experimentation for accelerated discovery and machine-assisted design of functional 2D materials and heterostructures. Here, the study reviews the recent progress and challenges of such endeavors, and highlight various emerging opportunities in this frontier research area.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The availability of an ever-expanding portfolio of 2D materials with rich internal degrees of freedom (spin, excitonic, valley, sublattice, and layer pseudospin) together with the unique ability to tailor heterostructures made layer by layer in a precisely chosen stacking sequence and relative crystallographic alignments, offers an unprecedented platform for realizing materials by design. However, the breadth of multi-dimensional parameter space and massive data sets involved is emblematic of complex, resource-intensive experimentation, which not only challenges the current state of the art but also renders exhaustive sampling untenable. To this end, machine learning, a very powerful data-driven approach and subset of artificial intelligence, is a potential game-changer, enabling a cheaper - yet more efficient - alternative to traditional computational strategies. It is also a new paradigm for autonomous experimentation for accelerated discovery and machine-assisted design of functional 2D materials and heterostructures. Here, the study reviews the recent progress and challenges of such endeavors, and highlight various emerging opportunities in this frontier research area. |
2023 |
Tian, Mingming; Chen, Qian; Wong, Ping Kwan Johnny; Liu, Ruobai; Silly, Fabien; Silly, Mathieu G; Ohresser, Philippe; You, Biao; Du, Jun; Wee, Andrew T S; Rojas-Sanchez, Juan-Carlos; Huang, Zhaocong; Zhang, Wen; Zhai, Ya Modulation of magneto-dynamic properties of permalloy/holmium heterostructures with antiferromagnetic coupled interface Journal Article APPLIED PHYSICS LETTERS, 123 (26), 2023, ISSN: 0003-6951. @article{ISI:001133695400003, title = {Modulation of magneto-dynamic properties of permalloy/holmium heterostructures with antiferromagnetic coupled interface}, author = {Mingming Tian and Qian Chen and Ping Kwan Johnny Wong and Ruobai Liu and Fabien Silly and Mathieu G Silly and Philippe Ohresser and Biao You and Jun Du and Andrew T S Wee and Juan-Carlos Rojas-Sanchez and Zhaocong Huang and Wen Zhang and Ya Zhai}, doi = {10.1063/5.0169500}, times_cited = {0}, issn = {0003-6951}, year = {2023}, date = {2023-12-25}, journal = {APPLIED PHYSICS LETTERS}, volume = {123}, number = {26}, publisher = {AIP Publishing}, address = {1305 WALT WHITMAN RD, STE 300, MELVILLE, NY 11747-4501 USA}, abstract = {Magneto-dynamics and its interfacial modulation have attracted much attention in energy-efficient and nonvolatile spintronic devices. In particular, the antiferromagnetic coupling at the interface plays a crucial role in spin dynamic behaviors. In this work, we utilize rare-earth holmium (Ho) to interface with transition-metal alloy Ni80Fe20(Py) and achieve a naturally formed antiferromagnetic coupling between Py and interfacial Ho via the magnetic proximity effect, as confirmed by element-specific synchrotron radiation x-ray magnetic circular dichroism hysteresis loops. Importantly, the antiferromagnetic coupled interface is preserved even at a low temperature of 4.2 K, which is below the Curie temperature of Ho. Using ferromagnetic resonance analysis, we reveal that the Gilbert damping and the interfacial spin mixing conductance of the Py/Ho bilayers are much larger than those of the Py/Pt and Py/Pd, suggesting a superior spin transparent efficiency on such an interface with an antiferromagnetic coupling. More importantly, upon the insertion of 2-nm-thick Cu, the antiferromagnetic coupling disappears, associated with the evident suppression of Gilbert damping. This strengthens the critical role of the antiferromagnetic coupled interface in the magneto-dynamics of the transition-metal/rare-earth bilayers and provides a promising way of magneto-dynamics modulation in antiferromagnet-based devices.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Magneto-dynamics and its interfacial modulation have attracted much attention in energy-efficient and nonvolatile spintronic devices. In particular, the antiferromagnetic coupling at the interface plays a crucial role in spin dynamic behaviors. In this work, we utilize rare-earth holmium (Ho) to interface with transition-metal alloy Ni80Fe20(Py) and achieve a naturally formed antiferromagnetic coupling between Py and interfacial Ho via the magnetic proximity effect, as confirmed by element-specific synchrotron radiation x-ray magnetic circular dichroism hysteresis loops. Importantly, the antiferromagnetic coupled interface is preserved even at a low temperature of 4.2 K, which is below the Curie temperature of Ho. Using ferromagnetic resonance analysis, we reveal that the Gilbert damping and the interfacial spin mixing conductance of the Py/Ho bilayers are much larger than those of the Py/Pt and Py/Pd, suggesting a superior spin transparent efficiency on such an interface with an antiferromagnetic coupling. More importantly, upon the insertion of 2-nm-thick Cu, the antiferromagnetic coupling disappears, associated with the evident suppression of Gilbert damping. This strengthens the critical role of the antiferromagnetic coupled interface in the magneto-dynamics of the transition-metal/rare-earth bilayers and provides a promising way of magneto-dynamics modulation in antiferromagnet-based devices. |
Koh, See Wee; Rekhi, Lavie; Arramel, ; Birowosuto, Muhammad Danang; Trinh, Quang Thang; Ge, Junyu; Yu, Wei; Wee, Andrew T S; Choksi, Tej S; Li, Hong Tuning the Work Function of MXene via Surface Functionalization Journal Article ACS APPLIED MATERIALS & INTERFACES, 2023, ISSN: 1944-8244. @article{ISI:001158819600001, title = {Tuning the Work Function of MXene via Surface Functionalization}, author = {See Wee Koh and Lavie Rekhi and Arramel and Muhammad Danang Birowosuto and Quang Thang Trinh and Junyu Ge and Wei Yu and Andrew T S Wee and Tej S Choksi and Hong Li}, doi = {10.1021/acsami.3c11857}, times_cited = {0}, issn = {1944-8244}, year = {2023}, date = {2023-12-14}, journal = {ACS APPLIED MATERIALS & INTERFACES}, publisher = {AMER CHEMICAL SOC}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {MXenes, a class of two-dimensional materials, have garnered significant attention due to their versatile surface chemistry and customizable properties. In this study, we investigate the work function (WF) tuning capabilities of MXene Ti3C2Tx, where T-x denotes the surface termination, synthesized via both conventional hydrogen fluoride-etched and recently reported molten salt-etched routes. When MXene samples are subjected to gas phase reactions, WF variations exceeding 0.6 eV are achieved, highlighting the potential for precise WF control. Notably, the WF increases from similar to 4.23 eV (in N-doped MXene etched using molten salt) to similar to 4.85 eV (N-doped MXene etched using HF). Complementary density functional theory (DFT) calculations reveal WF tuning across a >1 eV range via modification of the surface with different terminal groups (bare metal, F*, O*, N*, and Cl*). These changes in WF are attributed to surface termination modifications and the formation of TiO2 and TiN phases during annealing. DFT calculations further unveil an inverse correlation between the WF and the electron affinity of surface terminations. The findings from this comprehensive study provide insights into the tunable WF of MXenes, paving the way for their potential applications as interfacial layers in photovoltaic, energy conversion, and storage technologies.}, keywords = {}, pubstate = {published}, tppubtype = {article} } MXenes, a class of two-dimensional materials, have garnered significant attention due to their versatile surface chemistry and customizable properties. In this study, we investigate the work function (WF) tuning capabilities of MXene Ti3C2Tx, where T-x denotes the surface termination, synthesized via both conventional hydrogen fluoride-etched and recently reported molten salt-etched routes. When MXene samples are subjected to gas phase reactions, WF variations exceeding 0.6 eV are achieved, highlighting the potential for precise WF control. Notably, the WF increases from similar to 4.23 eV (in N-doped MXene etched using molten salt) to similar to 4.85 eV (N-doped MXene etched using HF). Complementary density functional theory (DFT) calculations reveal WF tuning across a >1 eV range via modification of the surface with different terminal groups (bare metal, F*, O*, N*, and Cl*). These changes in WF are attributed to surface termination modifications and the formation of TiO2 and TiN phases during annealing. DFT calculations further unveil an inverse correlation between the WF and the electron affinity of surface terminations. The findings from this comprehensive study provide insights into the tunable WF of MXenes, paving the way for their potential applications as interfacial layers in photovoltaic, energy conversion, and storage technologies. |
Hu, Junxiong; Han, Yulei; Chi, Xiao; Omar, Ganesh Ji; Ezzi, Mohammed Mohammed Esmail Al; Gou, Jian; Yu, Xiaojiang; Andrivo, Rusydi; Watanabe, Kenji; Taniguchi, Takashi; Wee, Andrew Thye Shen; Qiao, Zhenhua; Ariando, A Tunable Spin-Polarized States in Graphene on a Ferrimagnetic Oxide Insulator Journal Article ADVANCED MATERIALS, 36 (8), 2023, ISSN: 0935-9648. @article{ISI:001113825300001, title = {Tunable Spin-Polarized States in Graphene on a Ferrimagnetic Oxide Insulator}, author = {Junxiong Hu and Yulei Han and Xiao Chi and Ganesh Ji Omar and Mohammed Mohammed Esmail Al Ezzi and Jian Gou and Xiaojiang Yu and Rusydi Andrivo and Kenji Watanabe and Takashi Taniguchi and Andrew Thye Shen Wee and Zhenhua Qiao and A Ariando}, doi = {10.1002/adma.202305763}, times_cited = {0}, issn = {0935-9648}, year = {2023}, date = {2023-12-06}, journal = {ADVANCED MATERIALS}, volume = {36}, number = {8}, publisher = {WILEY-V C H VERLAG GMBH}, address = {POSTFACH 101161, 69451 WEINHEIM, GERMANY}, abstract = {Spin-polarized two-dimensional (2D) materials with large and tunable spin-splitting energy promise the field of 2D spintronics. While graphene has been a canonical 2D material, its spin properties and tunability are limited. Here, this work demonstrates the emergence of robust spin-polarization in graphene with large and tunable spin-splitting energy of up to 132 meV at zero applied magnetic fields. The spin polarization is induced through a magnetic exchange interaction between graphene and the underlying ferrimagnetic oxide insulating layer, Tm3Fe5O12, as confirmed by its X-ray magnetic circular dichroism (XMCD). The spin-splitting energies are directly measured and visualized by the shift in their Landau-fan diagram mapped by analyzing the measured Shubnikov-de-Haas (SdH) oscillations as a function of applied electric fields, showing consistent fit with the first-principles and machine learning calculations. Further, the observed spin-splitting energies can be tuned over a broad range between 98 and 166 meV by field cooling. The methods and results are applicable to other 2D (magnetic) materials and heterostructures, and offer great potential for developing next-generation spin logic and memory devices.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Spin-polarized two-dimensional (2D) materials with large and tunable spin-splitting energy promise the field of 2D spintronics. While graphene has been a canonical 2D material, its spin properties and tunability are limited. Here, this work demonstrates the emergence of robust spin-polarization in graphene with large and tunable spin-splitting energy of up to 132 meV at zero applied magnetic fields. The spin polarization is induced through a magnetic exchange interaction between graphene and the underlying ferrimagnetic oxide insulating layer, Tm3Fe5O12, as confirmed by its X-ray magnetic circular dichroism (XMCD). The spin-splitting energies are directly measured and visualized by the shift in their Landau-fan diagram mapped by analyzing the measured Shubnikov-de-Haas (SdH) oscillations as a function of applied electric fields, showing consistent fit with the first-principles and machine learning calculations. Further, the observed spin-splitting energies can be tuned over a broad range between 98 and 166 meV by field cooling. The methods and results are applicable to other 2D (magnetic) materials and heterostructures, and offer great potential for developing next-generation spin logic and memory devices. |
Zhang, Wen; Fu, Qiang; Li, Jiahui; Lian, Beilei; Xia, Yuze; Zhou, Liguo; Wee, Andrew Thye Shen; Wong, Ping Kwan Johnny Probing van der Waals magnetic surface and interface via circularly polarized X-rays Journal Article APPLIED PHYSICS REVIEWS, 10 (4), 2023, ISSN: 1931-9401. @article{ISI:001111315300002, title = {Probing van der Waals magnetic surface and interface via circularly polarized X-rays}, author = {Wen Zhang and Qiang Fu and Jiahui Li and Beilei Lian and Yuze Xia and Liguo Zhou and Andrew Thye Shen Wee and Ping Kwan Johnny Wong}, doi = {10.1063/5.0164400}, times_cited = {0}, issn = {1931-9401}, year = {2023}, date = {2023-12-01}, journal = {APPLIED PHYSICS REVIEWS}, volume = {10}, number = {4}, publisher = {AIP Publishing}, address = {1305 WALT WHITMAN RD, STE 300, MELVILLE, NY 11747-4501 USA}, abstract = {Advances in research of magnetic two-dimensional van der Waals (2D vdW) materials have opened up new opportunities in miniaturization of spintronic devices at the atomically thin limit. One major research thrust, which is the subject of this review, is that the magnetism of 2D vdW materials and their derived hetero-interface may be significantly affected by the local atomic geometry and environment. As a result, there is a pressing need for powerful advanced technique to characterize magnetic vdW surface and interface. Circularly polarized X-rays from synchrotron radiation light sources are key to this endeavor, as they can probe the microscopic magnetism of a specific element, for their atomic sensitivity, element-specificity, core-level excitation as well as capability of separation for the spin and orbit moments. We review a series of representative experimental achievements, exploiting circularly polarized X-rays, in (1) 2D vdW magnet, (2) magnetic metal/vdW interface, (3) molecule/vdW interface as well as (4) vdW/2D interface. On the basis of the review, advantages of probing magnetic vdW surface and interface by circularly polarized X-rays are presented, and challenges and opportunities are also discussed.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Advances in research of magnetic two-dimensional van der Waals (2D vdW) materials have opened up new opportunities in miniaturization of spintronic devices at the atomically thin limit. One major research thrust, which is the subject of this review, is that the magnetism of 2D vdW materials and their derived hetero-interface may be significantly affected by the local atomic geometry and environment. As a result, there is a pressing need for powerful advanced technique to characterize magnetic vdW surface and interface. Circularly polarized X-rays from synchrotron radiation light sources are key to this endeavor, as they can probe the microscopic magnetism of a specific element, for their atomic sensitivity, element-specificity, core-level excitation as well as capability of separation for the spin and orbit moments. We review a series of representative experimental achievements, exploiting circularly polarized X-rays, in (1) 2D vdW magnet, (2) magnetic metal/vdW interface, (3) molecule/vdW interface as well as (4) vdW/2D interface. On the basis of the review, advantages of probing magnetic vdW surface and interface by circularly polarized X-rays are presented, and challenges and opportunities are also discussed. |
Subagyo, Riki; Maulida, Pramitha Y D; Kowal, Dominik; Hartati, Sri; Muslimawati, Rossyaila M; Zetra, Yulfi; Diguna, Lina J; Akhlus, Syafsir; Mahyuddin, Muhammad H; Zhang, Lei; Tang, Chi S; Diao, Caozheng; Wee, Andrew T S; Birowosuto, Muhammad D; Arramel, Andrivo; Rusydi, Andrivo; Kusumawati, Yuly Spectroscopic Evidence of Localized Small Polarons in Low-Dimensional Ionic Liquid Lead-Free Hybrid Perovskites Journal Article ACS APPLIED MATERIALS & INTERFACES, 15 (47), pp. 54677-54691, 2023, ISSN: 1944-8244. @article{ISI:001111123400001, title = {Spectroscopic Evidence of Localized Small Polarons in Low-Dimensional Ionic Liquid Lead-Free Hybrid Perovskites}, author = {Riki Subagyo and Pramitha Y D Maulida and Dominik Kowal and Sri Hartati and Rossyaila M Muslimawati and Yulfi Zetra and Lina J Diguna and Syafsir Akhlus and Muhammad H Mahyuddin and Lei Zhang and Chi S Tang and Caozheng Diao and Andrew T S Wee and Muhammad D Birowosuto and Andrivo Arramel and Andrivo Rusydi and Yuly Kusumawati}, doi = {10.1021/acsami.3c12889}, times_cited = {0}, issn = {1944-8244}, year = {2023}, date = {2023-11-15}, journal = {ACS APPLIED MATERIALS & INTERFACES}, volume = {15}, number = {47}, pages = {54677-54691}, publisher = {AMER CHEMICAL SOC}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {Rational design is an important approach to consider in the development of low-dimensional hybrid organic-inorganic perovskites (HOIPs). In this study, 1-butyl-1-methyl pyrrolidinium (BMP), 1-(3-aminopropyl)imidazole (API), and 1-butyl-3-methyl imidazolium (BMI) serve as prototypical ionic liquid components in bismuth-based HOIPs. Element-sensitive X-ray absorption spectroscopy measurements of BMPBiBr4 and APIBiBr(5) reveal distinct resonant excitation profiles across the N K-edges, where contrasting peak shifts are observed. These 1D-HOIPs exhibit a large Stokes shift due to the small polaron contribution, as probed by photoluminescence spectroscopy at room temperature. Interestingly, the incorporation of a small fraction of tin (Sn) into the APIBiBr(5) (Sn/Bi mole ratio of 1:3) structure demonstrates a strong spectral weight transfer accompanied by a fast decay lifetime (2.6 ns). These phenomena are the direct result of Sn-substitution in APIBiBr(5), decreasing the small polaron effect. By changing the active ionic liquid, the electronic interactions and optical responses can be moderately tuned by alteration of their intermolecular interaction between the semiconducting inorganic layers and organic moieties.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Rational design is an important approach to consider in the development of low-dimensional hybrid organic-inorganic perovskites (HOIPs). In this study, 1-butyl-1-methyl pyrrolidinium (BMP), 1-(3-aminopropyl)imidazole (API), and 1-butyl-3-methyl imidazolium (BMI) serve as prototypical ionic liquid components in bismuth-based HOIPs. Element-sensitive X-ray absorption spectroscopy measurements of BMPBiBr4 and APIBiBr(5) reveal distinct resonant excitation profiles across the N K-edges, where contrasting peak shifts are observed. These 1D-HOIPs exhibit a large Stokes shift due to the small polaron contribution, as probed by photoluminescence spectroscopy at room temperature. Interestingly, the incorporation of a small fraction of tin (Sn) into the APIBiBr(5) (Sn/Bi mole ratio of 1:3) structure demonstrates a strong spectral weight transfer accompanied by a fast decay lifetime (2.6 ns). These phenomena are the direct result of Sn-substitution in APIBiBr(5), decreasing the small polaron effect. By changing the active ionic liquid, the electronic interactions and optical responses can be moderately tuned by alteration of their intermolecular interaction between the semiconducting inorganic layers and organic moieties. |
Noviyanto, Alfian; Amalia, Ratih; Maulida, Pramitha Yuniar Diah; Dioktyanto, Mudzakkir; Arrosyid, Bagas Haqi; Aryanto, Didik; Zhang, Lei; Wee, Andrew T S; Arramel, Anomalous Temperature-Induced Particle Size Reduction in Manganese Oxide Nanoparticles Journal Article ACS OMEGA, 8 (47), pp. 45152-45162, 2023, ISSN: 2470-1343. @article{ISI:001110569800001, title = {Anomalous Temperature-Induced Particle Size Reduction in Manganese Oxide Nanoparticles}, author = {Alfian Noviyanto and Ratih Amalia and Pramitha Yuniar Diah Maulida and Mudzakkir Dioktyanto and Bagas Haqi Arrosyid and Didik Aryanto and Lei Zhang and Andrew T S Wee and Arramel}, doi = {10.1021/acsomega.3c08012}, times_cited = {0}, issn = {2470-1343}, year = {2023}, date = {2023-11-13}, journal = {ACS OMEGA}, volume = {8}, number = {47}, pages = {45152-45162}, publisher = {AMER CHEMICAL SOC}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {The intricate role of temperature in the structure-property relationship of manganese oxide nanoparticles (Mn3O4 NPs) remains an open question. In this study, we successfully synthesized Mn3O4 NPs using the hydrothermal method with two differing temperatures, namely, 90 and 150 degrees C. Interestingly, a smaller average particle size is found when Mn3O4 NPs are synthesized at 150 degrees C compared to 90 degrees C, corresponding to 46.54 and 63.37 nm, respectively. This was confirmed by the time variation of temperature setting of 150 degrees C where the size evolution was insignificant, indicating a competing effect of nucleation and growth particles. Under varying NaOH concentrations (2-6 M) at 150 degrees C, a reduction in the particle size is found at the highest NaOH concentration (6 M). The particle grows slightly, indicating that the growth state is dominant compared to the nucleation state at low concentrations of NaOH. This finding implies that the high nucleation rate originates from the excessive monomer supply in the high-temperature reaction. In terms of crystallinity order, the structural arrangement of Mn3O4 NPs (150 degrees C) is largely decreased; this is likely due to a facile redox shift to the higher oxidation state of manganese. In addition, the higher ratio of adsorbed oxygen and lattice oxygen in Mn3O4 NPs at 150 degrees C is indirectly due to the higher oxygen vacancy occupancies, which supported the crystallinity decrease. Our findings provide a new perspective on manganese oxide formation in hydrothermal systems.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The intricate role of temperature in the structure-property relationship of manganese oxide nanoparticles (Mn3O4 NPs) remains an open question. In this study, we successfully synthesized Mn3O4 NPs using the hydrothermal method with two differing temperatures, namely, 90 and 150 degrees C. Interestingly, a smaller average particle size is found when Mn3O4 NPs are synthesized at 150 degrees C compared to 90 degrees C, corresponding to 46.54 and 63.37 nm, respectively. This was confirmed by the time variation of temperature setting of 150 degrees C where the size evolution was insignificant, indicating a competing effect of nucleation and growth particles. Under varying NaOH concentrations (2-6 M) at 150 degrees C, a reduction in the particle size is found at the highest NaOH concentration (6 M). The particle grows slightly, indicating that the growth state is dominant compared to the nucleation state at low concentrations of NaOH. This finding implies that the high nucleation rate originates from the excessive monomer supply in the high-temperature reaction. In terms of crystallinity order, the structural arrangement of Mn3O4 NPs (150 degrees C) is largely decreased; this is likely due to a facile redox shift to the higher oxidation state of manganese. In addition, the higher ratio of adsorbed oxygen and lattice oxygen in Mn3O4 NPs at 150 degrees C is indirectly due to the higher oxygen vacancy occupancies, which supported the crystallinity decrease. Our findings provide a new perspective on manganese oxide formation in hydrothermal systems. |
Whitcher, T J; Fauzi, A D; Diao, C; Chi, X; Syahroni, A; Asmara, T C; Breese, M B H; Neto, Castro A H; Wee, A T S; Majidi, M A; Rusydi, A Reply to: Reassessing the existence of soft X-ray correlated plasmons Journal Article NATURE COMMUNICATIONS, 14 (1), 2023. @article{ISI:001089230100018, title = {Reply to: Reassessing the existence of soft X-ray correlated plasmons}, author = {T J Whitcher and A D Fauzi and C Diao and X Chi and A Syahroni and T C Asmara and M B H Breese and Castro A H Neto and A T S Wee and M A Majidi and A Rusydi}, doi = {10.1038/s41467-023-40652-9}, times_cited = {0}, year = {2023}, date = {2023-10-24}, journal = {NATURE COMMUNICATIONS}, volume = {14}, number = {1}, publisher = {NATURE PORTFOLIO}, address = {HEIDELBERGER PLATZ 3, BERLIN, 14197, GERMANY}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
Tang, Chi Sin; Zeng, Shengwei; Wu, Jing; Chen, Shunfeng; Naradipa, Muhammad A; Song, Dongsheng; Milosevic, M V; Yang, Ping; Diao, Caozheng; Zhou, Jun; Pennycook, Stephen J; Breese, Mark B H; Cai, Chuanbing; Venkatesan, Thirumalai; Ariando, Ariando; Yang, Ming; Wee, Andrew T S; Yin, Xinmao "Detection of two-dimensional small polarons at oxide interfaces by optical spectroscopy" (vol 10, 031406 2023) Journal Article APPLIED PHYSICS REVIEWS, 10 (3), 2023, ISSN: 1931-9401. @article{ISI:001062976900001, title = {"Detection of two-dimensional small polarons at oxide interfaces by optical spectroscopy" (vol 10, 031406 2023)}, author = {Chi Sin Tang and Shengwei Zeng and Jing Wu and Shunfeng Chen and Muhammad A Naradipa and Dongsheng Song and M V Milosevic and Ping Yang and Caozheng Diao and Jun Zhou and Stephen J Pennycook and Mark B H Breese and Chuanbing Cai and Thirumalai Venkatesan and Ariando Ariando and Ming Yang and Andrew T S Wee and Xinmao Yin}, doi = {10.1063/5.0173910}, times_cited = {0}, issn = {1931-9401}, year = {2023}, date = {2023-09-01}, journal = {APPLIED PHYSICS REVIEWS}, volume = {10}, number = {3}, publisher = {AIP Publishing}, address = {1305 WALT WHITMAN RD, STE 300, MELVILLE, NY 11747-4501 USA}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
Tang, Chi Sin; Zeng, Shengwei; Wu, Jing; Chen, Shunfeng; Naradipa, Muhammad A; Song, Dongsheng; Milosevic, M V; Yang, Ping; Diao, Caozheng; Zhou, Jun; Pennycook, Stephen J; Breese, Mark B H; Cai, Chuanbing; Venkatesan, Thirumalai; Ariando, Ariando; Yang, Ming; Wee, Andrew T S; Yin, Xinmao Detection of two-dimensional small polarons at oxide interfaces by optical spectroscopy Journal Article APPLIED PHYSICS REVIEWS, 10 (3), 2023, ISSN: 1931-9401. @article{ISI:001038283300001, title = {Detection of two-dimensional small polarons at oxide interfaces by optical spectroscopy}, author = {Chi Sin Tang and Shengwei Zeng and Jing Wu and Shunfeng Chen and Muhammad A Naradipa and Dongsheng Song and M V Milosevic and Ping Yang and Caozheng Diao and Jun Zhou and Stephen J Pennycook and Mark B H Breese and Chuanbing Cai and Thirumalai Venkatesan and Ariando Ariando and Ming Yang and Andrew T S Wee and Xinmao Yin}, doi = {10.1063/5.0141814}, times_cited = {0}, issn = {1931-9401}, year = {2023}, date = {2023-09-01}, journal = {APPLIED PHYSICS REVIEWS}, volume = {10}, number = {3}, publisher = {AIP Publishing}, address = {1305 WALT WHITMAN RD, STE 300, MELVILLE, NY 11747-4501 USA}, abstract = {Two-dimensional (2D) perovskite oxide interfaces are ideal systems to uncover diverse emergent properties, such as the arising polaronic properties from short-range charge-lattice interactions. Thus, a technique to detect this quasiparticle phenomenon at the buried interface is highly coveted. Here, we report the observation of 2D small-polarons at the LaAlO3/SrTiO3 conducting interface using high-resolution spectroscopic ellipsometry. First-principles investigations show that interfacial electron-lattice coupling mediated by the longitudinal phonon mode facilitates the formation of these polarons. This study resolves the long-standing question by attributing the formation of interfacial 2D small polarons to the significant mismatch between experimentally measured interfacial carrier density and theoretical values. Our study sheds light on the complexity of broken periodic lattice-induced quasi-particle effects and its relationship with exotic phenomena at complex oxide interfaces. Meanwhile, this work establishes spectroscopic ellipsometry as a useful technique to detect and locate optical evidence of polaronic states and other emerging quantum properties at the buried interface.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Two-dimensional (2D) perovskite oxide interfaces are ideal systems to uncover diverse emergent properties, such as the arising polaronic properties from short-range charge-lattice interactions. Thus, a technique to detect this quasiparticle phenomenon at the buried interface is highly coveted. Here, we report the observation of 2D small-polarons at the LaAlO3/SrTiO3 conducting interface using high-resolution spectroscopic ellipsometry. First-principles investigations show that interfacial electron-lattice coupling mediated by the longitudinal phonon mode facilitates the formation of these polarons. This study resolves the long-standing question by attributing the formation of interfacial 2D small polarons to the significant mismatch between experimentally measured interfacial carrier density and theoretical values. Our study sheds light on the complexity of broken periodic lattice-induced quasi-particle effects and its relationship with exotic phenomena at complex oxide interfaces. Meanwhile, this work establishes spectroscopic ellipsometry as a useful technique to detect and locate optical evidence of polaronic states and other emerging quantum properties at the buried interface. |
Hu, Junxiong; Tan, Junyou; Ezzi, Mohammed Al M; Chattopadhyay, Udvas; Gou, Jian; Zheng, Yuntian; Wang, Zihao; Chen, Jiayu; Thottathil, Reshmi; Luo, Jiangbo; Watanabe, Kenji; Taniguchi, Takashi; Wee, Andrew Thye Shen; Adam, Shaffique; Ariando, A Controlled alignment of supermoire lattice in double-aligned graphene heterostructures Journal Article NATURE COMMUNICATIONS, 14 (1), 2023. @article{ISI:001029450400007, title = {Controlled alignment of supermoire lattice in double-aligned graphene heterostructures}, author = {Junxiong Hu and Junyou Tan and Mohammed Al M Ezzi and Udvas Chattopadhyay and Jian Gou and Yuntian Zheng and Zihao Wang and Jiayu Chen and Reshmi Thottathil and Jiangbo Luo and Kenji Watanabe and Takashi Taniguchi and Andrew Thye Shen Wee and Shaffique Adam and A Ariando}, doi = {10.1038/s41467-023-39893-5}, times_cited = {0}, year = {2023}, date = {2023-07-12}, journal = {NATURE COMMUNICATIONS}, volume = {14}, number = {1}, publisher = {NATURE PORTFOLIO}, address = {HEIDELBERGER PLATZ 3, BERLIN, 14197, GERMANY}, abstract = {The supermoire lattice, built by stacking two moire patterns, provides a platform for creating flat mini-bands and studying electron correlations. An ultimate challenge in assembling a graphene supermoire lattice is in the deterministic control of its rotational alignment, which is made highly aleatory due to the random nature of the edge chirality and crystal symmetry. Employing the so-called "golden rule of three", here we present an experimental strategy to overcome this challenge and realize the controlled alignment of double-aligned hBN/graphene/hBN supermoire lattice, where the twist angles between graphene and top/bottom hBN are both close to zero. Remarkably, we find that the crystallographic edge of neighboring graphite can be used to better guide the stacking alignment, as demonstrated by the controlled production of 20 moire samples with an accuracy better than similar to 0.2 degrees. Finally, we extend our technique to low-angle twisted bilayer graphene and ABC-stacked trilayer graphene, providing a strategy for flat-band engineering in these moirematerials.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The supermoire lattice, built by stacking two moire patterns, provides a platform for creating flat mini-bands and studying electron correlations. An ultimate challenge in assembling a graphene supermoire lattice is in the deterministic control of its rotational alignment, which is made highly aleatory due to the random nature of the edge chirality and crystal symmetry. Employing the so-called "golden rule of three", here we present an experimental strategy to overcome this challenge and realize the controlled alignment of double-aligned hBN/graphene/hBN supermoire lattice, where the twist angles between graphene and top/bottom hBN are both close to zero. Remarkably, we find that the crystallographic edge of neighboring graphite can be used to better guide the stacking alignment, as demonstrated by the controlled production of 20 moire samples with an accuracy better than similar to 0.2 degrees. Finally, we extend our technique to low-angle twisted bilayer graphene and ABC-stacked trilayer graphene, providing a strategy for flat-band engineering in these moirematerials. |
Gou, Jian; Bai, Hua; Zhang, Xuanlin; Huang, Yu Li; Duan, Sisheng; Ariando, A; Yang, Shengyuan A; Chen, Lan; Lu, Yunhao; Wee, Andrew Thye Shen Two-dimensional ferroelectricity in a single-element bismuth monolayer Journal Article NATURE, 617 (7959), pp. 67-+, 2023, ISSN: 0028-0836. @article{ISI:000990835100012, title = {Two-dimensional ferroelectricity in a single-element bismuth monolayer}, author = {Jian Gou and Hua Bai and Xuanlin Zhang and Yu Li Huang and Sisheng Duan and A Ariando and Shengyuan A Yang and Lan Chen and Yunhao Lu and Andrew Thye Shen Wee}, doi = {10.1038/s41586-023-05848-5}, times_cited = {0}, issn = {0028-0836}, year = {2023}, date = {2023-04-05}, journal = {NATURE}, volume = {617}, number = {7959}, pages = {67-+}, publisher = {NATURE PORTFOLIO}, address = {HEIDELBERGER PLATZ 3, BERLIN, 14197, GERMANY}, abstract = {Ferroelectric materials are fascinating for their non-volatile switchable electric polarizations induced by the spontaneous inversion-symmetry breaking. However, in all of the conventional ferroelectric compounds, at least two constituent ions are required to support the polarization switching(1,2). Here, we report the observation of a single-element ferroelectric state in a black phosphorus-like bismuth layer(3), in which the ordered charge transfer and the regular atom distortion between sublattices happen simultaneously. Instead of a homogenous orbital configuration that ordinarily occurs in elementary substances, we found the Bi atoms in a black phosphorous-like Bi monolayer maintain a weak and anisotropic sp orbital hybridization, giving rise to the inversion-symmetry-broken buckled structure accompanied with charge redistribution in the unit cell. As a result, the in-plane electric polarization emerges in the Bi monolayer. Using the in-plane electric field produced by scanning probe microscopy, ferroelectric switching is further visualized experimentally. Owing to the conjugative locking between the charge transfer and atom displacement, we also observe the anomalous electric potential profile at the 180 degrees tail-to-tail domain wall induced by competition between the electronic structure and electric polarization. This emergent single-element ferroelectricity broadens the mechanism of ferroelectrics and may enrich the applications of ferroelectronics in the future.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Ferroelectric materials are fascinating for their non-volatile switchable electric polarizations induced by the spontaneous inversion-symmetry breaking. However, in all of the conventional ferroelectric compounds, at least two constituent ions are required to support the polarization switching(1,2). Here, we report the observation of a single-element ferroelectric state in a black phosphorus-like bismuth layer(3), in which the ordered charge transfer and the regular atom distortion between sublattices happen simultaneously. Instead of a homogenous orbital configuration that ordinarily occurs in elementary substances, we found the Bi atoms in a black phosphorous-like Bi monolayer maintain a weak and anisotropic sp orbital hybridization, giving rise to the inversion-symmetry-broken buckled structure accompanied with charge redistribution in the unit cell. As a result, the in-plane electric polarization emerges in the Bi monolayer. Using the in-plane electric field produced by scanning probe microscopy, ferroelectric switching is further visualized experimentally. Owing to the conjugative locking between the charge transfer and atom displacement, we also observe the anomalous electric potential profile at the 180 degrees tail-to-tail domain wall induced by competition between the electronic structure and electric polarization. This emergent single-element ferroelectricity broadens the mechanism of ferroelectrics and may enrich the applications of ferroelectronics in the future. |
Guo, Qiangbing; Qi, Xiao-Zhuo; Zhang, Lishu; Gao, Meng; Hu, Sanlue; Zhou, Wenju; Zang, Wenjie; Zhao, Xiaoxu; Wang, Junyong; Yan, Bingmin; Xu, Mingquan; Wu, Yun-Kun; Eda, Goki; Xiao, Zewen; Yang, Shengyuan A; Gou, Huiyang; Feng, Yuan Ping; Guo, Guang-Can; Zhou, Wu; Ren, Xi-Feng; Qiu, Cheng-Wei; Pennycook, Stephen J; Wee, Andrew T S Ultrathin quantum light source with van der Waals NbOCl2 crystal Journal Article NATURE, 613 (7942), pp. 53-+, 2023, ISSN: 0028-0836. @article{ISI:000955711300008, title = {Ultrathin quantum light source with van der Waals NbOCl_{2} crystal}, author = {Qiangbing Guo and Xiao-Zhuo Qi and Lishu Zhang and Meng Gao and Sanlue Hu and Wenju Zhou and Wenjie Zang and Xiaoxu Zhao and Junyong Wang and Bingmin Yan and Mingquan Xu and Yun-Kun Wu and Goki Eda and Zewen Xiao and Shengyuan A Yang and Huiyang Gou and Yuan Ping Feng and Guang-Can Guo and Wu Zhou and Xi-Feng Ren and Cheng-Wei Qiu and Stephen J Pennycook and Andrew T S Wee}, doi = {10.1038/s41586-022-05393-7}, times_cited = {9}, issn = {0028-0836}, year = {2023}, date = {2023-01-05}, journal = {NATURE}, volume = {613}, number = {7942}, pages = {53-+}, publisher = {NATURE PORTFOLIO}, address = {HEIDELBERGER PLATZ 3, BERLIN, 14197, GERMANY}, abstract = {Interlayer electronic coupling in two-dimensional materials enables tunable and emergent properties by stacking engineering. However, it also results in significant evolution of electronic structures and attenuation of excitonic effects in two-dimensional semiconductors as exemplified by quickly degrading excitonic photoluminescence and optical nonlinearities in transition metal dichalcogenides when monolayers are stacked into van der Waals structures. Here we report a van der Waals crystal, niobium oxide dichloride (NbOCl2), featuring vanishing interlayer electronic coupling and monolayer-like excitonic behaviour in the bulk form, along with a scalable second-harmonic generation intensity of up to three orders higher than that in monolayer WS2. Notably, the strong second-order nonlinearity enables correlated parametric photon pair generation, through a spontaneous parametric down-conversion (SPDC) process, in flakes as thin as about 46 nm. To our knowledge, this is the first SPDC source unambiguously demonstrated in two-dimensional layered materials, and the thinnest SPDC source ever reported. Our work opens an avenue towards developing van der Waals material-based ultracompact on-chip SPDC sources as well as high-performance photon modulators in both classical and quantum optical technologies(1-4).}, keywords = {}, pubstate = {published}, tppubtype = {article} } Interlayer electronic coupling in two-dimensional materials enables tunable and emergent properties by stacking engineering. However, it also results in significant evolution of electronic structures and attenuation of excitonic effects in two-dimensional semiconductors as exemplified by quickly degrading excitonic photoluminescence and optical nonlinearities in transition metal dichalcogenides when monolayers are stacked into van der Waals structures. Here we report a van der Waals crystal, niobium oxide dichloride (NbOCl2), featuring vanishing interlayer electronic coupling and monolayer-like excitonic behaviour in the bulk form, along with a scalable second-harmonic generation intensity of up to three orders higher than that in monolayer WS2. Notably, the strong second-order nonlinearity enables correlated parametric photon pair generation, through a spontaneous parametric down-conversion (SPDC) process, in flakes as thin as about 46 nm. To our knowledge, this is the first SPDC source unambiguously demonstrated in two-dimensional layered materials, and the thinnest SPDC source ever reported. Our work opens an avenue towards developing van der Waals material-based ultracompact on-chip SPDC sources as well as high-performance photon modulators in both classical and quantum optical technologies(1-4). |
2022 |
Han, Shulun; Tang, Chi Sin; Li, Linyang; Liu, Yi; Liu, Huimin; Gou, Jian; Wu, Jing; Zhou, Difan; Yang, Ping; Diao, Caozheng; Ji, Jiacheng; Bao, Jinke; Zhang, Lingfeng; Zhao, Mingwen; Milosevic, Milorad V; Guo, Yanqun; Tian, Lijun; Breese, Mark B H; Cao, Guanghan; Cai, Chuanbing; Wee, Andrew T S; Yin, Xinmao Orbital-Hybridization-Driven Charge Density Wave Transition in CsV3Sb5 Kagome Superconductor Journal Article ADVANCED MATERIALS, 35 (8), 2022, ISSN: 0935-9648. @article{ISI:000903664200001, title = {Orbital-Hybridization-Driven Charge Density Wave Transition in CsV_{3}Sb_{5} Kagome Superconductor}, author = {Shulun Han and Chi Sin Tang and Linyang Li and Yi Liu and Huimin Liu and Jian Gou and Jing Wu and Difan Zhou and Ping Yang and Caozheng Diao and Jiacheng Ji and Jinke Bao and Lingfeng Zhang and Mingwen Zhao and Milorad V Milosevic and Yanqun Guo and Lijun Tian and Mark B H Breese and Guanghan Cao and Chuanbing Cai and Andrew T S Wee and Xinmao Yin}, doi = {10.1002/adma.202209010}, times_cited = {0}, issn = {0935-9648}, year = {2022}, date = {2022-12-23}, journal = {ADVANCED MATERIALS}, volume = {35}, number = {8}, publisher = {WILEY-V C H VERLAG GMBH}, address = {POSTFACH 101161, 69451 WEINHEIM, GERMANY}, abstract = {Owing to its inherent non-trivial geometry, the unique structural motif of the recently discovered kagome topological superconductor AV(3)Sb(5) (A = K, Rb, Cs) is an ideal host of diverse topologically non-trivial phenomena, including giant anomalous Hall conductivity, topological charge order, charge density wave (CDW), and unconventional superconductivity. Despite possessing a normal-state CDW order in the form of topological chiral charge order and diverse superconducting gaps structures, it remains unclear how fundamental atomic-level properties and many-body effects including Fermi surface nesting, electron-phonon coupling, and orbital hybridization contribute to these symmetry-breaking phenomena. Here, the direct participation of the V3d-Sb5p orbital hybridization in mediating the CDW phase transition in CsV3Sb5 is reported. The combination of temperature-dependent X-ray absorption and first-principles studies clearly indicates the inverse Star-of-David structure as the preferred reconstruction in the low-temperature CDW phase. The results highlight the critical role that Sb orbitals play and establish orbital hybridization as the direct mediator of the CDW states and structural transition dynamics in kagome unconventional superconductors. This is a significant step toward the fundamental understanding and control of the emerging correlated phases from the kagome lattice through the orbital interactions and provides promising approaches to novel regimes in unconventional orders and topology.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Owing to its inherent non-trivial geometry, the unique structural motif of the recently discovered kagome topological superconductor AV(3)Sb(5) (A = K, Rb, Cs) is an ideal host of diverse topologically non-trivial phenomena, including giant anomalous Hall conductivity, topological charge order, charge density wave (CDW), and unconventional superconductivity. Despite possessing a normal-state CDW order in the form of topological chiral charge order and diverse superconducting gaps structures, it remains unclear how fundamental atomic-level properties and many-body effects including Fermi surface nesting, electron-phonon coupling, and orbital hybridization contribute to these symmetry-breaking phenomena. Here, the direct participation of the V3d-Sb5p orbital hybridization in mediating the CDW phase transition in CsV3Sb5 is reported. The combination of temperature-dependent X-ray absorption and first-principles studies clearly indicates the inverse Star-of-David structure as the preferred reconstruction in the low-temperature CDW phase. The results highlight the critical role that Sb orbitals play and establish orbital hybridization as the direct mediator of the CDW states and structural transition dynamics in kagome unconventional superconductors. This is a significant step toward the fundamental understanding and control of the emerging correlated phases from the kagome lattice through the orbital interactions and provides promising approaches to novel regimes in unconventional orders and topology. |
Mahyuddin, Muhammad Haris; Arramel, ; Diguna, Lina Jaya; Agusta, Mohammad Kemal; Mulyani, Irma; Onggo, Djulia; Shiddiq, Muhandis; Tang, Chi Sin; Yin, Xinmao; Diao, Caozheng; Birowosuto, Muhammad Danang; Wee, Andrew Thye Shen; Rusydi, Andrivo Tailoring the Optical and Electronic Properties of 2D Hybrid Dion-Jacobson Copper Chloride Perovskites Journal Article JOURNAL OF PHYSICAL CHEMISTRY C, 126 (50), pp. 21297-21307, 2022, ISSN: 1932-7447. @article{ISI:000895662800001, title = {Tailoring the Optical and Electronic Properties of 2D Hybrid Dion-Jacobson Copper Chloride Perovskites}, author = {Muhammad Haris Mahyuddin and Arramel and Lina Jaya Diguna and Mohammad Kemal Agusta and Irma Mulyani and Djulia Onggo and Muhandis Shiddiq and Chi Sin Tang and Xinmao Yin and Caozheng Diao and Muhammad Danang Birowosuto and Andrew Thye Shen Wee and Andrivo Rusydi}, doi = {10.1021/acs.jpcc.2c06050}, times_cited = {2}, issn = {1932-7447}, year = {2022}, date = {2022-12-09}, journal = {JOURNAL OF PHYSICAL CHEMISTRY C}, volume = {126}, number = {50}, pages = {21297-21307}, publisher = {AMER CHEMICAL SOC}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {The upsurge of low-dimensional Dion-Jacobson (DJ) phase perovskites has brought significant interest in view of their appealing stability against harsh environmental conditions as well as their promising performance in optoelectronic applications. Few reports to date have concentrated on the fundamental relationship of fine-tuning the control of diamine-based perovskite single crystals toward their electronic properties and optical behaviors. Here, we demonstrate that cationic control is proposed to regulate the role of hydrogen bonding of organic ligands with the edge-sharing [CuCl6](4-) octahedral layers, leading to strong differences in the material excitonic profile and tunability of their electronic properties. Interestingly, we observe a significant reduction of photoluminescence intensity upon controlling the Cu2+/Cu+ proportion in this hybrid system. According to the photoemission measurements, variation in the oxidation states of Cu cations plays a crucial role in stabilizing the diammonium-based perovskite geometric structure. Interestingly, we find that the electronic signatures of the singlet spin-state and high-energy region transition are not influenced by the thermal effect, as probed by temperature-dependent X-ray absorption spectroscopy (XAS) at elevated temperature. Density functional calculations suggest that such an electronic difference originates from the hydrogen bonding reduction that altered the magnitude of the octahedral distortion within the DJ layered structure. As a result, the +3NHC4H9NH3+ conformation produces a non-negligible interaction toward tuning the optical and electronic properties of DJ copper-based perovskites.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The upsurge of low-dimensional Dion-Jacobson (DJ) phase perovskites has brought significant interest in view of their appealing stability against harsh environmental conditions as well as their promising performance in optoelectronic applications. Few reports to date have concentrated on the fundamental relationship of fine-tuning the control of diamine-based perovskite single crystals toward their electronic properties and optical behaviors. Here, we demonstrate that cationic control is proposed to regulate the role of hydrogen bonding of organic ligands with the edge-sharing [CuCl6](4-) octahedral layers, leading to strong differences in the material excitonic profile and tunability of their electronic properties. Interestingly, we observe a significant reduction of photoluminescence intensity upon controlling the Cu2+/Cu+ proportion in this hybrid system. According to the photoemission measurements, variation in the oxidation states of Cu cations plays a crucial role in stabilizing the diammonium-based perovskite geometric structure. Interestingly, we find that the electronic signatures of the singlet spin-state and high-energy region transition are not influenced by the thermal effect, as probed by temperature-dependent X-ray absorption spectroscopy (XAS) at elevated temperature. Density functional calculations suggest that such an electronic difference originates from the hydrogen bonding reduction that altered the magnitude of the octahedral distortion within the DJ layered structure. As a result, the +3NHC4H9NH3+ conformation produces a non-negligible interaction toward tuning the optical and electronic properties of DJ copper-based perovskites. |