Article
Chemistry, Physical
Henry Yu, Sunny Gupta, Alex Kutana, Boris Yakobson
Summary: The electronic transport through a metal|semiconductor heterojunction is mainly determined by the Schottky barrier, with the pinning strength in 3D structures depending on the ratio between interface quantum capacitance and metal surface capacitance. In 2D structures, the interface dipole does not affect band alignment but influences the Schottky barrier and transport. The turn-on voltage and pinning strength in 2D contacts are affected by the physical parameter l/lambda(D), the ratio between interface width and thermal de Broglie wavelength.
JOURNAL OF PHYSICAL CHEMISTRY LETTERS
(2021)
Article
Chemistry, Physical
Qin Zhou, Chunsheng Cai, Qin Xiong, Zilong Zhang, Jianbin Xu, Lusheng Liang, Shibo Wang, Weihai Sun, Zhongyi Yuan, Peng Gao
Summary: By using a novel semiconductive material and a newly proposed photon-relaxation mechanism, the trap states at the surface of perovskite solar cells can be reduced, leading to improved performance and stability.
ADVANCED ENERGY MATERIALS
(2022)
Article
Chemistry, Multidisciplinary
Jun Wang, Ganghai Ni, Wanru Liao, Kang Liu, Jiawei Chen, Fangyang Liu, Zongliang Zhang, Ming Jia, Jie Li, Junwei Fu, Evangelina Pensa, Liangxing Jiang, Zhenfeng Bian, Emiliano Cortes, Min Liu
Summary: Photoelectrochemical (PEC) water splitting is a promising approach for renewable solar light conversion, but surface Fermi level pinning severely restricts the PEC activities. Theoretical calculations suggest that subsurface oxygen vacancies could release the Fermi level pinning and maintain the active structure. A series of metal oxide semiconductors with subsurface oxygen vacancies were prepared and demonstrated to eliminate surface trap states and de-pin the Fermi level. Superior PEC performances were achieved on BiVO4, Bi2O3, and TiO2, surpassing most reported works under the same conditions.
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
(2023)
Article
Chemistry, Multidisciplinary
Andrei Stefancu, Seunghoon Lee, Li Zhu, Min Liu, Raluca Ciceo Lucacel, Emiliano Cortes, Nicolae Leopold
Summary: This study highlights a new metal-molecule charge transfer process by tuning the Fermi energy of plasmonic silver nanoparticles (AgNPs) in situ. The strong adsorption of halide ions upshifts the Fermi level of AgNPs, promoting spontaneous charge transfer to molecular acceptor orbitals. The catalytic role of halide ions in plasmonic nanostructures depends on their surface affinity compared to the target molecule, providing new insights into the interaction mechanisms.
Article
Chemistry, Physical
Yuxuan Sun, Zhen Jiao, Harold J. W. Zandvliet, Pantelis Bampoulis
Summary: In this study, conductive atomic force microscopy was used to investigate charge carrier injection in metal-GeS nanocontacts. Three dominant injection mechanisms were identified: thermionic emission, direct tunneling, and Fowler-Nordheim tunneling. The Schottky barrier was found to be independent of the metallic tip's work function, indicating strong Fermi-level pinning.
JOURNAL OF PHYSICAL CHEMISTRY C
(2022)
Article
Nanoscience & Nanotechnology
Jae Eun Seo, Tanmoy Das, Eunpyo Park, Dongwook Seo, Joon Young Kwak, Jiwon Chang
Summary: Two-dimensional materials are considered key materials for future logic devices due to their excellent electrostatic integrity, but carrier polarity control in 2D material field-effect transistors remains a challenging issue. The carrier polarity in PdSe2 FETs can be modulated simply by changing the metal contact, allowing for the realization of complementary logic functions in PdSe2-based CMOS circuits. Ultimately, this study suggests the potential for PdSe2-based CMOS logic circuits with different metal contacts for n- and p-MOSFETs.
ACS APPLIED MATERIALS & INTERFACES
(2021)
Article
Chemistry, Multidisciplinary
Lutz Baumgarten, Thomas Szyjka, Terence Mittmann, Andrei Gloskovskii, Christoph Schlueter, Thomas Mikolajick, Uwe Schroeder, Martina Mueller
Summary: The reliability of ferroelectric HfO2- and HZO-based memory devices is strongly influenced by the choice of electrode materials. Interface conditions, such as band alignment, defect formation, and doping, are recognized as decisive factors for device performance. Hard X-ray photoelectron spectroscopy reveals two opposite scenarios of band alignment in TiN/HZO/TiN and IrO2/HZO/IrO2, explaining the conditions for stable device performance and degradation. A key condition for the stability of ferroelectric devices is identified as the alignment of the charge neutrality level with the metallic Fermi level. Oxygen-deficient HfO2-based interfaces, where the Fermi level of the metal electrode is close to the conduction band of the ferroelectric insulator, can achieve stable device performance.
ADVANCED FUNCTIONAL MATERIALS
(2023)
Article
Nanoscience & Nanotechnology
Dominik Christian Moritz, Isaac Azahel Ruiz Alvarado, Mohammad Amin Zare Pour, Agnieszka Paszuk, Tilo Friess, Erich Runge, Jan P. Hofmann, Thomas Hannappel, Wolf Gero Schmidt, Wolfram Jaegermann
Summary: Stable InP (001) surfaces have occupied valence bands and empty conduction bands, but experimental results show that the surface Fermi level is slightly below the midgap energy, causing surface band bending. Surface defects on P-rich InP (001) surfaces formed from hydrogen desorption are responsible for this discrepancy. These hydrogen-related defects are stable when water is adsorbed, as long as water does not dissociate. Therefore, water exposure does not affect the surface band bending on a flat InP (001) surface.
ACS APPLIED MATERIALS & INTERFACES
(2022)
Article
Physics, Applied
Youjung Kim, Hyeongmin Cho, Kookrin Char
Summary: Delta-doped BaSnO3 systems were studied in terms of band bending and surface boundary conditions, with measurements of 2D carrier density and investigation into the effect of capping layer thickness. The system was well described by band bending through Poisson-Schrodinger simulation, and the evolution of surface boundary conditions on La-doped BaSnO3 was revealed with changes in capping layer thickness.
APPLIED PHYSICS LETTERS
(2021)
Article
Multidisciplinary Sciences
Jiawei Wang, Jiebin Niu, Bin Shao, Guanhua Yang, Congyan Lu, Mengmeng Li, Zheng Zhou, Xichen Chuai, Jiezhi Chen, Nianduan Lu, Bing Huang, Yeliang Wang, Ling Li, Ming Liu
Summary: In this study, the nonlinear charge transport in conducting polymers was investigated by varying the crystalline degrees of samples. A heterogeneous-resistive-network model based on the link between Fermi liquids and Luttinger liquids was proposed to explain the nonlinear transport behaviors. The model was supported by precise electrical and microstructural characterizations, providing new insights into microstructure-correlated charge transport in organic solids.
NATURE COMMUNICATIONS
(2021)
Article
Physics, Applied
William M. Strickland, Mehdi Hatefipour, Dylan Langone, S. M. Farzaneh, Javad Shabani
Summary: The surface morphology of near-surface InAs quantum wells is closely connected to low-temperature transport, where electron mobility is highly sensitive to the growth temperature of the underlying graded buffer layer. By introducing an In0.81Al0.19As capping layer, the Fermi level in the InAs layer can be tuned.
APPLIED PHYSICS LETTERS
(2022)
Article
Chemistry, Multidisciplinary
Ruo-Si Chen, Guanglong Ding, Zihao Feng, Shi-Rui Zhang, Wen-Ai Mo, Su-Ting Han, Ye Zhou
Summary: This study investigates the suppressing effect of MXene on Fermi level pinning in MoS2 transistors and proposes a new strategy to eliminate the negative effects of FLP in 2D materials-based electronic devices by using Ti3C2Tx as an electrode to build a Ti3C2Tx-MoS2 heterostructure.
ADVANCED FUNCTIONAL MATERIALS
(2022)
Article
Chemistry, Physical
Sotirios Tsatsos, John Vakros, Spyridon Ladas, Xenophon E. Verykios, Georgios Kyriakou
Summary: A series of WO3/TiO2 catalysts were synthesized and characterized for the NO selective catalytic reduction (SCR) with NH3. The interfacial electron transfer between WO3 and TiO2 was studied, and its relationship with the acid-base properties of the catalytic surface and electronic structure modification was defined. The results showed that altering the dispersion and size of the WO3 nanostructures led to changes in titania's surface electron distribution, which affected the catalytic activity. It was found that higher WO3 loading on TiO2 resulted in stronger electronic interaction and higher catalytic activity due to increased surface electron density and enhanced surface basicity.
JOURNAL OF COLLOID AND INTERFACE SCIENCE
(2022)
Review
Chemistry, Multidisciplinary
Xiaochi Liu, Min Sup Choi, Euyheon Hwang, Won Jong Yoo, Jian Sun
Summary: This article discusses the impact of Fermi level pinning (FLP) in 2D semiconductor devices and its causes. The authors indicate that FLP is mainly due to inefficient doping into 2D materials, vdW gap at the metal interface, and hybridized compounds formed under contacting metals. The article further explores the effects of FLP on 2D device performance and methods for improving metallic contact to 2D materials.
ADVANCED MATERIALS
(2022)
Article
Chemistry, Physical
Xiaohui Ju, Bretislav Smid, Viktor Johanek, Ivan Khalakhan, Yurii Yakovlev, Iva Matolinova, Vladimir Matolin
Summary: This study investigated the interaction between dextran and polycrystalline cerium oxide surfaces, revealing mutual charge transfer and surface accumulation of Ce3+ during dextran adsorption. It was found that hydroxyl groups from dextran competitively adsorb on the surface, and thermal annealing results in desorption and decomposition of dextran.
APPLIED SURFACE SCIENCE
(2021)
Article
Materials Science, Multidisciplinary
Pawel Strak, Ashfaq Ahmad, Pawel Kempisty, Jacek Piechota, Konrad Sakowski, Grzegorz Nowak, Yoshihiro Kangawa, Jan Lazewski, Stanislaw Krukowski
Summary: Ab initio calculations were used to investigate the physical properties of AlN(0001) surface under Al coverage, revealing the adsorption behavior and energy dependence on coverage for Al adatoms. The adlayer undergoes structural changes from disordered and corrugated to ordered and atomically flat with increasing Al coverage, affecting the Al bonding energy. Thermodynamic analysis identified equilibrium regions with Al vapor, crucial for physical vapor transport AlN growth.
COMPUTATIONAL MATERIALS SCIENCE
(2022)
Article
Chemistry, Physical
Kamil Koronski, Krzysztof P. Korona, Serhii Kryvyi, Aleksandra Wierzbicka, Kamil Sobczak, Stanislaw Krukowski, Pawel Strak, Eva Monroy, Agata Kaminska
Summary: This paper presents a comparative analysis of the optical properties of non-polar and polar GaN/AlGaN multi-quantum well (MQW) structures using time-resolved photoluminescence (TRPL) and pressure-dependent studies. The results show that the lack of internal electric fields in non-polar structures leads to an improved electron and hole wavefunction overlap, resulting in shorter decay times. On the other hand, polar structures with electric fields exhibit reduced emission energy and wavefunction overlap, leading to a decrease in recombination rate with increasing well width. The study also explores the energy dependence of radiative and non-radiative recombination processes and the influence of electric fields on pressure behavior.
Article
Infectious Diseases
Monika J. Piotrowska, Konrad Sakowski, Johannes Horn, Rafael Mikolajczyk, Andre Karch
Summary: The introduction of multi-drug-resistant Enterobacteriaceae (MDR-E) by colonized patients transferred from high-prevalence countries has led to several large outbreaks of MDR-E in low-prevalence countries, with the risk of propagated spread to the community. This study aimed to derive a strategy to counteract the spread of MDR-E at the regional health-care network level. The results showed that targeted hospital-based infection control measures were effective in reducing the system-wide prevalence of MDR-E.
CLINICAL MICROBIOLOGY AND INFECTION
(2023)
Article
Physics, Applied
Ashfaq Ahmad, Pawel Strak, Konrad Sakowski, Jacek Piechota, Pawel Kempisty, Agata Kaminska, Stanislaw Krukowski
Summary: Ab initio simulations were used to study the properties of GaN/AlN superlattices with different widths for the first time. The results revealed significant differences between polar and nonpolar systems in terms of band diagrams, bandgaps, and oscillator strengths.
JOURNAL OF APPLIED PHYSICS
(2022)
Article
Physics, Multidisciplinary
Roman Hrytsak, Pawel Kempisty, Michal Leszczynski, Malgorzata Sznajder
Summary: This paper investigates the mechanism behind the 'green gap' problem and demonstrates that the Kirkendall effect may contribute to the thermal decomposition of InGaN/GaN MQWs structures.
NEW JOURNAL OF PHYSICS
(2022)
Article
Chemistry, Physical
Ashfaq Ahmad, Pawel Strak, Pawel Kempisty, Konrad Sakowski, Jacek Piechota, Yoshihiro Kangawa, Izabella Grzegory, Michal Leszczynski, Zbigniew R. R. Zytkiewicz, Grzegorz Muziol, Eva Monroy, Agata Kaminska, Stanislaw Krukowski
Summary: Polarization doping in a GaN-InN system with a graded composition layer was studied using ab initio simulations. The electric charge volume density in the graded concentration part was determined by spatial potential dependence. The polarization difference in the GaN-InN system was changed by piezoelectric effects and showed potential applications in blue and green laser and light-emitting diode design.
Article
Mathematics, Applied
Monika J. Piotrowska, Aleksandra Puchalska, Konrad Sakowski
Summary: In this paper, the transfer of patients in the healthcare system is described using SIS-type equations coupled by impulses at fixed times. The mathematical analysis of a general theoretical model incorporating the structure of patients' transfers is provided. The results disprove intuitions from decoupled systems and demonstrate the damping effect on infection when the transmission rate is locally higher than the recovery rate. Observations on network suppression of pathogen spread allow for identification of high-prevalence units and propose interventions to reduce infection spread in the entire system. The core results combine system dynamics and structural properties. A model of hospital-acquired multidrug-resistant bacteria infections is considered to illustrate the theoretical considerations.
APPLIED MATHEMATICS AND COMPUTATION
(2023)
Article
Chemistry, Physical
Jacek Piechota, Stanislaw Krukowski, Bohdan Sadovyi, Petro Sadovyi, Sylwester Porowski, Izabella Grzegory
Summary: This study investigates the behavior of GaN crystal at high temperatures and pressures, revealing that it undergoes thermal decomposition and congruent melting. Simulation results are in excellent agreement with experimental data, providing valuable insights into the physical properties of GaN.
CHEMISTRY OF MATERIALS
(2023)
Article
Materials Science, Multidisciplinary
Pawel Kempisty, Ashfaq Ahmad, Pawel Strak, Konrad Sakowski, Anna Kafar, Jacek Piechota, Stanislaw Krukowski
Summary: Indium incorporation on the GaN surface was analyzed in the context of InGaN growth by MOVPE. The results showed that the adsorption energy strongly depends on the electronic properties of the surface, and the increase in hydrogen pressure leads to an increase in the equilibrium pressures of indium, resulting in reduced indium incorporation.
COMPUTATIONAL MATERIALS SCIENCE
(2023)
Article
Physics, Applied
S. Zoino, L. Borowik, B. Mohamad, E. Nowak, P. Kempisty
Summary: The formation of a two-dimensional electron gas (2DEG) at the GaN (0001)/AlN interface holds significant implications for GaN-based high-voltage and high-frequency (RF) devices. Recent ab initio simulations shed light on the role of polarizations in driving the formation of the 2DEG, and the study also investigates the impact of fixed charges and additional layers on the carrier concentration.
JOURNAL OF APPLIED PHYSICS
(2023)
Article
Chemistry, Physical
Pawel Kempisty, Karol Kawka, Akira Kusaba, Yoshihiro Kangawa
Summary: This paper presents an improved theoretical view of ab initio thermodynamics for polar GaN surfaces under gallium-rich conditions. The study uses density functional theory (DFT) calculations to systematically investigate the adsorption of gallium atoms on GaN polar surfaces, starting from the clean surface and progressing to the metallic multilayer. The analysis confirms that a monolayer of Ga adatoms on the GaN(000-1) surface is highly stable over a wide range of temperatures and provides a better thermodynamic description of the surface state under conditions typical for molecular beam epitaxy.
