Cheng Lin Quan Nicholas
Group: Prof Quek Su Ying
CA2DM Publications:
2021 |
Cheng, Nicholas Lin Quan; Xuan, Fengyuan; Spataru, Catalin D; Quek, Su Ying Charge Transfer Screening and Energy Level Alignment at Complex Organic-Inorganic Interfaces: A Tractable Ab Initio GW Approach Journal Article JOURNAL OF PHYSICAL CHEMISTRY LETTERS, 12 (36), pp. 8841-8846, 2021, ISSN: 1948-7185. @article{ISI:000697334300019, title = {Charge Transfer Screening and Energy Level Alignment at Complex Organic-Inorganic Interfaces: A Tractable \textit{Ab Initio} GW Approach}, author = {Nicholas Lin Quan Cheng and Fengyuan Xuan and Catalin D Spataru and Su Ying Quek}, doi = {10.1021/acs.jpclett.1c02302}, times_cited = {1}, issn = {1948-7185}, year = {2021}, date = {2021-09-07}, journal = {JOURNAL OF PHYSICAL CHEMISTRY LETTERS}, volume = {12}, number = {36}, pages = {8841-8846}, publisher = {AMER CHEMICAL SOC}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {Complex organic-inorganic interfaces are important for device and sensing applications. Charge transfer doping is prevalent in such applications and can affect the interfacial energy level alignments (ELA), which are determined by many-body interactions. We develop an approximate ab initio many-body GW approach that can capture many-body interactions due to interfacial charge transfer. The approach uses significantly less resources than a regular GW calculation but gives excellent agreement with benchmark GW calculations on an F4TCNQ/graphene interface. We find that many-body interactions due to charge transfer screening result in gate-tunable F4TCNQ HOMO-LUMO gaps. We further predict the ELA of a large system of experimental interest-4,4'-bis(dimethylamino)-bipyridine (DMAP-OED) on monolayer MoS2, where charge transfer screening results in an similar to 1 eV reduction of the molecular HOMO-LUMO gap. Comparison with a two-dimensional electron gas model reveals the importance of explicitly considering the intraband transitions in determining the charge transfer screening in organic-inorganic interface systems.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Complex organic-inorganic interfaces are important for device and sensing applications. Charge transfer doping is prevalent in such applications and can affect the interfacial energy level alignments (ELA), which are determined by many-body interactions. We develop an approximate ab initio many-body GW approach that can capture many-body interactions due to interfacial charge transfer. The approach uses significantly less resources than a regular GW calculation but gives excellent agreement with benchmark GW calculations on an F4TCNQ/graphene interface. We find that many-body interactions due to charge transfer screening result in gate-tunable F4TCNQ HOMO-LUMO gaps. We further predict the ELA of a large system of experimental interest-4,4'-bis(dimethylamino)-bipyridine (DMAP-OED) on monolayer MoS2, where charge transfer screening results in an similar to 1 eV reduction of the molecular HOMO-LUMO gap. Comparison with a two-dimensional electron gas model reveals the importance of explicitly considering the intraband transitions in determining the charge transfer screening in organic-inorganic interface systems. |
2019 |
Noori, Keian; Cheng, Nicholas Lin Quan; Xuan, Fengyuan; Quek, Su Ying Dielectric screening by 2D substrates Journal Article 2D MATERIALS, 6 (3), 2019, ISSN: 2053-1583. @article{ISI:000470869000001, title = {Dielectric screening by 2D substrates}, author = {Keian Noori and Nicholas Lin Quan Cheng and Fengyuan Xuan and Su Ying Quek}, doi = {10.1088/2053-1583/ab1e06}, times_cited = {0}, issn = {2053-1583}, year = {2019}, date = {2019-07-01}, journal = {2D MATERIALS}, volume = {6}, number = {3}, publisher = {IOP PUBLISHING LTD}, address = {TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND}, abstract = {Two-dimensional (2D) materials are increasingly being used as active components in nanoscale devices. Many interesting properties of 2D materials stem from the reduced and highly non-local electronic screening in two dimensions. While electronic screening within 2D materials has been studied extensively, the question still remains of how 2D substrates screen charge perturbations or electronic excitations adjacent to them. Thickness-dependent dielectric screening properties have recently been studied using electrostatic force microscopy (EFM) experiments. However, it was suggested that some of the thickness-dependent trends were due to extrinsic effects. Similarly, Kelvin probe measurements (KPM) indicate that charge fluctuations are reduced when BN slabs are placed on SiO2, but it is unclear if this effect is due to intrinsic screening from BN. In this work, we use first principles calculations to study the fully non-local dielectric screening properties of 2D material substrates. Our simulations give results in good qualitative agreement with those from EFM experiments, for hexagonal boron nitride (BN), graphene and MoS2, indicating that the experimentally observed thickness-dependent screening effects are intrinsic to the 2D materials. We further investigate explicitly the role of BN in lowering charge potential fluctuations arising from charge impurities on an underlying SiO2 substrate, as observed in the KPM experiments. 2D material substrates can also dramatically change the HOMO-LUMO gaps of adsorbates, especially for small molecules, such as benzene. We propose a reliable and very quick method to predict the HOMOLUMO gaps of small physisorbed molecules on 2D and 3D substrates, using only the band gap of the substrate and the gas phase gap of the molecule.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Two-dimensional (2D) materials are increasingly being used as active components in nanoscale devices. Many interesting properties of 2D materials stem from the reduced and highly non-local electronic screening in two dimensions. While electronic screening within 2D materials has been studied extensively, the question still remains of how 2D substrates screen charge perturbations or electronic excitations adjacent to them. Thickness-dependent dielectric screening properties have recently been studied using electrostatic force microscopy (EFM) experiments. However, it was suggested that some of the thickness-dependent trends were due to extrinsic effects. Similarly, Kelvin probe measurements (KPM) indicate that charge fluctuations are reduced when BN slabs are placed on SiO2, but it is unclear if this effect is due to intrinsic screening from BN. In this work, we use first principles calculations to study the fully non-local dielectric screening properties of 2D material substrates. Our simulations give results in good qualitative agreement with those from EFM experiments, for hexagonal boron nitride (BN), graphene and MoS2, indicating that the experimentally observed thickness-dependent screening effects are intrinsic to the 2D materials. We further investigate explicitly the role of BN in lowering charge potential fluctuations arising from charge impurities on an underlying SiO2 substrate, as observed in the KPM experiments. 2D material substrates can also dramatically change the HOMO-LUMO gaps of adsorbates, especially for small molecules, such as benzene. We propose a reliable and very quick method to predict the HOMOLUMO gaps of small physisorbed molecules on 2D and 3D substrates, using only the band gap of the substrate and the gas phase gap of the molecule. |