Article
Chemistry, Analytical
Seoho Jung, Roland Hauert, Miroslav Haluska, Cosmin Roman, Christofer Hierold
Summary: By using Ar-ion etching to remove the top layer of the electrode surface before nanotube placement, the contact resistance at the nanotube-metal interface can be significantly reduced. This results in a tenfold decrease in the median ON-resistance of transistors and a more than two orders of magnitude decrease in the interquartile range of resistance values.
SENSORS AND ACTUATORS B-CHEMICAL
(2021)
Article
Physics, Applied
Damon B. Farmer
Summary: As a one-dimensional structure with atomically thin sidewalls, charge transport in carbon nanotubes is a surface phenomenon and can be affected by perturbations from the surrounding environment. This study investigates the effects of contact metallization on carbon nanotube field-effect transistors (CNTFETs) and finds that using titanium as an adhesion layer enhances the ON current in n-type CNTFETs. Thermal metallization consistently produces devices with higher ON current, while electron-beam processing can cause radiation effects and decrease the transconductance in the devices.
JOURNAL OF APPLIED PHYSICS
(2022)
Article
Biochemistry & Molecular Biology
Jeffrey Plante, Beth A. Caine, Paul L. A. Popelier
Summary: Predicting the aqueous pK(a) of carbon acids is challenging due to insufficient experimental data, but using atom-type feature vectors can help reduce prediction errors. Incorporating knowledge from multiple models into a general model has shown to improve predictions compared to using literature experimental data alone.
Article
Chemistry, Multidisciplinary
Tomas Blecha, Zuzana Vlckova Zivcova, Farjana J. Sonia, Martin Mergl, Oleksandr Volochanskyi, Michal Bodnar, Pavel Rous, Kenichiro Mizohata, Martin Kalbac, Otakar Frank
Summary: Contact resistance between electrically connected parts of electronic elements can negatively affect their resulting properties and parameters. This study investigates the factors influencing the contact resistance between graphene prepared by chemical vapour deposition and pre-patterned electrodes. The results show that electrode surface treatment methods affect the resistance between copper and graphene, while deposition techniques do not influence the resulting contact resistance for gold electrodes, which significantly decreases.
Article
Materials Science, Multidisciplinary
Khai Yi Chin, Eric P. Fahrenthold
Summary: Improvements in carbon-based conductors can impact the development of new electronic and optoelectronic devices, potentially offering significant weight savings compared to copper, which is important in mass sensitive applications such as aircraft design. Chemical doping is seen as the most likely route to high specific conductivity carbon-based wiring, with the testing of potassium tetrabromoaurate showing potential complications due to differences in the nominal dopant molecule and the 'in situ' configuration of the dopant species. Ab initio modeling of KAuBr4 doping suggests that the dopant is most effective in a disassociated form, but overall, KAuBr4 doping is unlikely to produce high specific conductivity CNT wiring.
COMPUTATIONAL MATERIALS SCIENCE
(2021)
Review
Chemistry, Physical
Qing Cao
Summary: This article examines the scaling advantages of carbon nanotubes compared to silicon, reviews the latest progress on addressing the manufacturability issues for scaled carbon-nanotube transistors, and discusses possible pathways for nanotube transistors to transition into commercial applications.
Article
Chemistry, Multidisciplinary
Zhihui Cheng, Jonathan Backman, Huairuo Zhang, Hattan Abuzaid, Guoqing Li, Yifei Yu, Linyou Cao, Albert V. Davydov, Mathieu Luisier, Curt A. Richter, Aaron D. Franklin
Summary: 2D semiconducting materials show great potential in future electronics due to their atomically thin nature. In this study, physically scaled contacts and asymmetrical contact measurements are used to investigate the contact scaling behavior in 2D field-effect transistors. The results show that scaled source contacts can limit the drain current, while scaled drain contacts do not. Quantum transport simulations reveal that the transfer length of Ni-MoS2 contacts can be as short as 5 nm. The study provides further understanding of contact scaling behavior at various interfaces.
ADVANCED MATERIALS
(2023)
Article
Engineering, Electrical & Electronic
Sheng-Kai Su, Alfonso Sanchez-Soares, Edward Chen, Thomas Kelly, Giorgos Fagas, James C. Greer, Gregory Pitner, H-S Philip Wong, Iuliana P. Radu
Summary: Carbon nanotube field effect transistors (CNFETs) have potential applications in future logic technology, but contact resistance and leakage currents could limit their scaling. The coupling between contact metal and CNT is found to impact both contact resistance and leakage current. A compromise for contact and extension lengths suitable for digital logic is proposed.
IEEE ELECTRON DEVICE LETTERS
(2022)
Article
Physics, Multidisciplinary
Xiao Zhang, Boxue Zhang, Haydar Sahin, Zhuo Bin Siu, S. M. Rafi-Ul-Islam, Jian Feng Kong, Bing Shen, Mansoor B. A. Jalil, Ronny Thomale, Ching Hua Lee
Summary: The qualitative nature of physical systems can be predicted from their scaling relationship with system size. In a two-dimensional LC circuit network, there is a profound deviation from logarithmic scaling in impedance, which depends sensitively on the number of nodes N and is robust against perturbations. This anomalous impedance behavior is due to a generalized resonance condition and exhibits a fractal-like structure of impedance peaks for different N. It is not explained by continuum theory or regular waveguide resonant behavior.
COMMUNICATIONS PHYSICS
(2023)
Article
Chemistry, Physical
G. Medrano, E. Bainglass, O. Andreussi
Summary: Continuum solvation models are important in condensed matter simulations to characterize materials interfaces in wet electrified environments at reduced computational cost. However, implementing these models in plane-wave simulation packages for complex and heterogeneous environments is still challenging. This study proposes a double-cell formalism to address these challenges by separating the simulation cell for the continuum environment from the one for the electronic-structure simulation, allowing for larger simulation cell without increasing computational time.
JOURNAL OF CHEMICAL PHYSICS
(2023)
Article
Chemistry, Multidisciplinary
Sobia Younas, Aqdas Riaz, Haq Nawaz, Muhammad Irfan Majeed, Muhammad Adnan Iqbal, Nosheen Rashid, Areeba Altaf, Umar Sohail Shoukat, Faisal Jamil, Aafia Sehar, Sania Munir, Mahrosh Javed, Muhammad Imran
Summary: In this study, Raman spectroscopy along with density functional theory (DFT) calculations were used to characterize and confirm the formation of three different selenium-based N-heterocyclic carbene (NHC) complexes. The analysis of mean RS features and DFT calculations showed that the polarizability of benzimidazolium rings increased after complex formation with selenium, indicating the formation of newly formed bonds. The identification of new peaks in the spectra of the complexes further confirmed their formation. Principal Component Analysis (PCA) was used to analyze the Raman spectral data sets, demonstrating the efficiency of RS analysis. Overall, the results demonstrated the fast and effective use of RS and DFT for confirming the synthesis of selenium-based NHC complexes.
Article
Chemistry, Physical
Wenbin Xu, Mie Andersen, Karsten Reuter
Summary: The study identified descriptors using a compressed sensing approach and algebraic expressions to predict adsorption enthalpies of oxygen evolution reaction on metal oxide catalysts, outperforming single descriptors in accuracy and computational cost. Considering features related to local charge transfer significantly improves refined scaling relations, allowing for the screening of OER electrocatalysts with theoretical overpotential uncertainty similar to the expected DFT error.
Article
Chemistry, Physical
Aziz Habibi-Yangjeh, Hadi Basharnavaz
Summary: DFT computations were used to investigate the adsorption performance of hydrogen molecules over transition metals embedded graphitic carbon nitride, showing that Os-embedded gCN has superior interaction with H-2 molecules. The maximum storage number of adsorbed H-2 molecules was found to be 6. Adsorption of H-2 molecules converted the semi-conductive behavior of the systems to a conductive state.
INTERNATIONAL JOURNAL OF HYDROGEN ENERGY
(2021)
Article
Physics, Multidisciplinary
Hao Yin, Zhiguo Liu, Juekuan Yang
Summary: This paper proposes a model for predicting the thermal conductivity of carbon nanotube networks, considering them as contact thermal resistance networks. The model we proposed shows better agreement with experimental results compared to previous models.
Article
Chemistry, Multidisciplinary
Caio Vinicius Caetano, Silvete Guerini, Augusto Cesar Azevedo Silva, Jaldyr de Jesus Gomes Varela Junior
Summary: Density functional theory calculations were conducted to investigate the interaction between (10,0) GaPNT and FeCl3 and CrO3 compounds, revealing that FeCl3 and CrO3 interact strongly with GaPNT through chemisorption, leading to significant changes in electronic and structural properties. The adsorption of FeCl3 on GaPNT resulted in the appearance of localized states in the gap region, causing a reduction in band gap, while CrO3 adsorption outside GaPNT increased the band gap. FeCl3 adsorption inside GaPNT turned the system metallic, unlike the other systems which remained semiconductors.
NEW JOURNAL OF CHEMISTRY
(2021)
Article
Chemistry, Multidisciplinary
Nikolai Tsvetkov, Muhammad Ejaz Khan, Byeong Cheul Moon, Yong-Hoon Kim, Jeung Ku Kang
Summary: This study successfully created a zipper-like interdigitated interface between a Pb-based halide perovskite light absorber and an oxide ETL, significantly enhancing the charge extraction process. Experimental and computational evidence identified the atomistic origin of the emergent two-dimensional interfacial metallicity. The unconventional defect-passivating nature of the strained interdigitated perovskite/ETL interface was emphasized, leading to improved charge extraction efficiency and higher photovoltaic performance.
Article
Chemistry, Multidisciplinary
Hongyue Jing, Hyeonwoo Yeo, Benzheng Lyu, Junga Ryou, Seunghyuk Choi, Jin-Hong Park, Byoung Hun Lee, Yong-Hoon Kim, Sungjoo Lee
Summary: The paper demonstrates the chemical modification of Ti3C2Tx MXene via diazonium covalent chemistry and the subsequent effects on the electrical properties of MXene. The work function of functionalized MXene can be modulated by adjusting the concentration of the diazonium salt solution, with an adjustable range of around 0.6 eV. The controlled modification of surface groups in Ti3C2Tx may imbue Ti3C2Tx with favorable electronic behaviors, showing prospects for electronic field applications.
Article
Nanoscience & Nanotechnology
Bum-Kyu Kim, Tae-Hyung Kim, Dong-Hwan Choi, Hanul Kim, Kenji Watanabe, Takashi Taniguchi, Heesuk Rho, Ju-Jin Kim, Yong-Hoon Kim, Myung-Ho Bae
Summary: The study reports the fabrication of ultraclean vdW contacts between indium and molybdenum disulfide, elucidating the atomistic origins of its Ohmic-like transport properties. By evaporating low thermal energy indium and cooling the substrate holder with liquid nitrogen, atomically clean In/MoS2 vdW contacts were achieved, exhibiting high-quality Ohmic-like transport behavior over a wide temperature range. The research suggests that generating a strong density of in-gap states while minimizing interfacial charge transfer could be a general strategy to reduce contact resistance for two-dimensional vdW materials.
NPJ 2D MATERIALS AND APPLICATIONS
(2021)
Article
Chemistry, Multidisciplinary
Soungmin Bae, William Espinosa-Garcia, Yoon-Gu Kang, Noriyuki Egawa, Juho Lee, Kazuaki Kuwahata, Mohammad Khazaei, Kaoru Ohno, Yong-Hoon Kim, Myung Joon Han, Hideo Hosono, Gustavo M. Dalpian, Hannes Raebiger
Summary: A new structural phase has been discovered for M2CO2 MXenes with low ionization energy and ability to bind multiple lithium atoms, making them suitable for various applications. These systems can be described as electron-ion systems with anionic electrons and have the potential for charge storage, thermal field emission, and as anode materials in lithium batteries.
ADVANCED FUNCTIONAL MATERIALS
(2021)
Article
Chemistry, Physical
Da-Eun Yoon, Juho Lee, Hyeonwoo Yeo, Junga Ryou, Young Kuk Lee, Yong-Hoon Kim, Doh C. Lee
Summary: Shape anisotropy in colloidal zincblende CdSe nanoplatelets directly affects their optical and electronic properties. The lateral aspect ratio of NPLs provides a way to control their optical characteristics, such as polarized emission, by varying the shape while keeping the thickness constant. Experimental and simulation studies have shown that the growth behavior of CdSe NPLs can be altered by adjusting the Cd(ac)(2)-to-Se precursor ratio, leading to different growth directions. The mechanism for the lateral growth of zincblende NPLs has been explained at the atomic level, shedding light on the transition processes of NPL morphology and growth direction.
CHEMISTRY OF MATERIALS
(2021)
Article
Chemistry, Multidisciplinary
Seunghwan Seo, Je-Jun Lee, Ryong-Gyu Lee, Tae Hyung Kim, Sangyong Park, Sooyoung Jung, Hyun-Kyu Lee, Maksim Andreev, Kyeong-Bae Lee, Kil-Su Jung, Seyong Oh, Ho-Jun Lee, Ki Seok Kim, Geun Young Yeom, Yong-Hoon Kim, Jin-Hong Park
Summary: Optogenetics involves using light to manipulate neuronal activity, which can be applied in the development of intelligent systems. A flexible van der Waals optoelectronic synapse fabricated on ReS2 successfully mimics the dynamics of biological synapses.
ADVANCED MATERIALS
(2021)
Article
Chemistry, Multidisciplinary
Hanbyeol Jang, Yumin Song, Yongwook Seok, Heungsoon Im, Tae Hyung Kim, Joo-Hyoung Lee, Yong-Hoon Kim, Kayoung Lee
Summary: This paper presents state-of-the-art self-powered near-infrared sensors utilizing graphene/In/InSe/Au as a photoactive region, exhibiting outstanding performance. Multiple self-powered InSe photodetectors with different device structures and contacts were systematically investigated, with the asymmetrically assembled graphene/In/InSe/Au vertical heterostructure showing efficient electron-hole pair separation. The study also demonstrates InSe vertical field-effect transistors and estimates built-in field, drift velocity, and corresponding transit time using out-of-plane carrier mobility and structural parameters.
Article
Materials Science, Multidisciplinary
Hyeong-Yong Hwang, Sehyuk Lee, Yong-Hoon Kim, Farman Ullah, Chinh Tam Le, Yong Soo Kim, Ki-Ju Yee, Christopher J. Stanton, Young-Dahl Jho
Summary: In two-dimensional transition metal dichalcogenides, strain modulation can manipulate electronic band structures and photoluminescence. A novel method of external bending is used to control the photoluminescence in monolayer WSe2-MoSe2 lateral heterostructures, where both normal strain and shear strain are involved. The dependence of the photoluminescence on bending direction and the violation of optical selection rules under tensile bending are observed, which indicates the mixing of spin subbands induced by shear strain.
Article
Chemistry, Physical
Yejin Kim, Soungmin Bae, Joohee Park, Trang Thi Thu Nguyen, Hye Ri Jung, William Jo, Yong-Hoon Kim, Hannes Raebiger, Seokhyun Yoon
Summary: Research found a unique alignment of MA ions in CH3NH3PbCl3, indicating the presence of ferroelectricity in hybrid organic-inorganic perovskites.
CHEMISTRY OF MATERIALS
(2022)
Article
Chemistry, Physical
Tae Hyung Kim, Juho Lee, Ryong-Gyu Lee, Yong-Hoon Kim
Summary: In this study, a non-equilibrium first-principles simulation method based on the multi-space constrained-search density functional formalism is introduced for the computer-aided design of vertically stacked 2D van der Waals heterostructure devices. The research shows that the negative differential resistance (NDR) characteristics can be produced through the gating-induced mismatch between two graphene Dirac cones in energy-momentum space and the bias-dependent energetic shift of defect levels. Furthermore, the placement of carbon atoms substituted for nitrogen atoms on different layers of hBN significantly affects the device characteristics, emphasizing the importance of atomic details for 2D vdW devices.
NPJ COMPUTATIONAL MATERIALS
(2022)
Article
Nanoscience & Nanotechnology
Juho Lee, Muhammad Ejaz Khan, Yong-Hoon Kim
Summary: This study explores the material and device characteristics of low-dimensional organometal halide perovskites. It is found that lead triiodide columns can be made semimetallic, and heterojunctions with ultrahigh negative differential resistance can be formed. Additionally, similar characteristics can also be obtained from germanium triiodide, showing potential for flexible electronics applications.
Article
Multidisciplinary Sciences
Soungmin Bae, Kana Matsumoto, Hannes Raebiger, Ken-ichi Shudo, Yong-Hoon Kim, Orjan Sele Handegard, Tadaaki Nagao, Masahiro Kitajima, Yuji Sakai, Xiang Zhang, Robert Vajtai, Pulickel Ajayan, Junichiro Kono, Jun Takeda, Ikufumi Katayama
Summary: In this study, we observed coherent signals of longitudinal acoustic (LA) phonons in monolayer MoSe2 using sub-10-fs-resolution pump-probe spectroscopy. These phonons play a crucial role in the intervalley carrier scattering process. By conducting a phonon symmetry analysis and first-principles calculations, we found that only the LA phonon at the K point, not the M point, could generate odd-order experimental phonon signals.
NATURE COMMUNICATIONS
(2022)
Article
Chemistry, Multidisciplinary
Jihyun Kim, Joonho Park, Yong-Hoon Kim, William Jo
Summary: This paper reports on an approach using ammonium chloride (AC) to enhance passivation effects by controlling chlorine and ammonium ions. The results demonstrate that the multifunctional healing effects of NH4+ and the change of passivation agent from Cl to NH4+ effectively suppress non-radiative recombination.
Article
Chemistry, Physical
Soungmin Bae, Tae Young Jeong, Hannes Raebiger, Ki-Ju Yee, Yong-Hoon Kim
Summary: We present spectroscopic evidence for the ultrafast trapping of band edge excitons at defects and the subsequent generation of defect-localized coherent phonons (CPs) in monolayer MoSe2. Our time-resolved pump-probe spectroscopy on the sub-picosecond time scale detects localized CPs only from the ultrafast exciton trapping at shallow traps. Based on density functional calculations, we identify the origins of deep and shallow traps as Se vacancy and oxygen molecule adsorbed on a Se vacancy, respectively. Our work establishes the correlations between defect-induced ultrafast exciton trapping and the generation of defect-localized CPs, providing new opportunities for engineering photoexcited carriers in two-dimensional materials through lattice defects.
NANOSCALE HORIZONS
(2023)
Article
Materials Science, Multidisciplinary
S. Bae, Y-G Kang, M. Khazaei, K. Ohno, Y-H Kim, M. J. Han, K. J. Chang, H. Raebiger
Summary: Transition metal compounds are challenging for ab initio calculations due to the localized nature of d electrons, leading to errors in electronic and magnetic properties. This study used density functional theory to calculate 22 carbide MXenes with different methods, revealing new ground-state structures and magnetic states. Various methods were compared to improve the reliability of theoretical studies on MXenes.
MATERIALS TODAY ADVANCES
(2021)
