Article
Materials Science, Coatings & Films
Femi Mathew, Nithin Poonkottil, Eduardo Solano, Dirk Poelman, Zeger Hens, Christophe Detavernier, Jolien Dendooven
Summary: This study presents a new plasma-enhanced atomic layer deposition (PE-ALD) process for depositing high-quality Ga2S3 sulfide thin films. Compared to thermal ALD, the PE-ALD process allows for deposition of crystalline films at lower temperatures and without detectable carbon and oxygen contamination.
JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A
(2023)
Article
Biochemistry & Molecular Biology
Shicong Jiang, Wan-Yu Wu, Fangbin Ren, Chia-Hsun Hsu, Xiaoying Zhang, Peng Gao, Dong-Sing Wuu, Chien-Jung Huang, Shui-Yang Lien, Wenzhang Zhu
Summary: The application of (In, Al, Ga)N materials in photovoltaic devices has attracted much attention. However, to deposit high-quality GaN material as a foundation is essential. Plasma-enhanced atomic layer deposition (PEALD) combines the advantages of ALD process with plasma utilization and has been used to deposit thin films with various requirements. In this study, NH3-containing plasma was used to eliminate the residual oxygen during the growth of GaN films, which significantly improved the quality of the films. The plasma power controlled NH2, NH, and H radicals showed strong influence on the oxygen content, growth rate, crystallinity, and surface roughness of the GaN films.
INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES
(2022)
Article
Materials Science, Multidisciplinary
Ramasis Goswami, Syed Qadri, Neeraj Nepal, Charles Eddy
Summary: In this study, ultra-thin AlN films were grown on different substrates using atomic layer epitaxy, showing that the substrate, particularly the strain, plays a crucial role in determining the crystal structure of AlN films. The strain level varied significantly depending on the substrate, impacting the orientation relation and crystal quality of AlN films.
Article
Chemistry, Multidisciplinary
Hao Li, Yali Yang, Shiqing Deng, Hui Liu, Tianyu Li, Yuzhu Song, He Bai, Tao Zhu, Jiaou Wang, Huanhua Wang, Er-Jia Guo, Xianran Xing, Hongjun Xiang, Jun Chen
Summary: Regulating the magnetic properties of multiferroics enables their potential application in spintronic devices. By utilizing oxygen defect engineering, we significantly enhanced the room temperature ferromagnetism of a representative ferrite, EuFeO3. Our findings suggest that the decrease in Fe-O-Fe bond angles caused by oxygen vacancies strengthens magnetic interactions and tilts Fe spins, leading to an approximately five-fold increase in saturation magnetization. Furthermore, we established the internal relationship between magnetism and oxygen vacancies by illustrating how magnetic structure and magnitude change with varying vacancy configuration and concentration. This strategy for regulating magnetic properties has broad applicability to various functional oxide materials.
Article
Materials Science, Multidisciplinary
Aaron J. McLeod, Ping C. Lee, Scott T. Ueda, Zachary J. Devereaux, Charles H. Winter, Jeff Spiegelman, Ravindra Kanjolia, Mansour Moinpour, Andrew C. Kummel
Summary: This study demonstrates a method of atomic layer annealing (ALA) with radio-frequency (RF) substrate bias for GaN deposition at a low temperature of 275 degrees C on insulating and amorphous substrates. GaN is typically deposited at high temperatures, resulting in strain upon cooling, thus the need for low-temperature alternatives. Tris(dimethylamido) gallium (III) and hydrazine were used as precursors, with Ar and Kr serving as ion bombardment. The optimization of substrate bias potential was evaluated using GI-XRD and XRR. The application of RF bias reduced the oxygen and carbon content in the film and broadened the crystallites. This research highlights the effectiveness of ALA with RF substrate bias for depositing GaN thin films at low temperatures on insulating substrates.
Article
Chemistry, Physical
Seok Choi, Abu Saad Ansari, Hee Ju Yun, Hogyoung Kim, Bonggeun Shong, Byung Joon Choi
Summary: High Al content AlGaN films were successfully grown via thermal atomic layer deposition at low temperature, where the electrical properties of the films could be modulated by controlling the pulse ratio of AlN and GaN subcycles. Layer-by-layer growth with close to theoretical dielectric constant could be achieved by introducing sufficient number of AlN subcycles.
JOURNAL OF ALLOYS AND COMPOUNDS
(2021)
Article
Biochemistry & Molecular Biology
Xiao Wang, Zhihua Shen, Jie Li, Shengli Wu
Summary: This study prepared a c-axis crystallized IGZO thin film by RF sputtering and found that it exhibited better acid corrosion resistance compared to amorphous IGZO films, with a 74% increase in anticorrosion performance. This suggests that crystalline IGZO thin films can provide more stable performance in applications.
Article
Chemistry, Physical
Zishu Zhu, Zhanpeng Ou, Yanpu Chen, JiaXin Zhao, Wei Zhu, Pingping Ma, Liren Lou, Bicai Pan
Summary: High uniformity AlN thin films with varying Sc doping concentration levels were deposited on Ti (120 nm)/Si substrates. The impact of Sc doping ratio and annealing temperature on the magnetic properties of Al1-xScxN were investigated. It was found that the ferromagnetism of Al1-xScxN originates from the Al vacancies introduced by Sc ions. The concentration of Al vacancies increases with higher Sc doping ratio, resulting in a magnetic phase change according to the results of spin-polarized density of states (DOS). (c) 2023 Elsevier B.V. All rights reserved.
JOURNAL OF ALLOYS AND COMPOUNDS
(2023)
Article
Chemistry, Multidisciplinary
Long Xu, Yuehan Cao, Tianwei Song, Caixia Xu
Summary: This work investigates the low-threshold resonant lasing emission in undoped and Mg-doped GaN thin films on sapphire substrates with interfacial design. The scattering cross-section of the periodic resonant structure is found to reduce the threshold and enhance the resonant lasing emission. Mg-doped GaN thin films show better lasing emission performance compared to undoped and Si-doped GaN thin films. The lasing energy level system and defect densities play a vital role in the lasing emission.
Article
Chemistry, Multidisciplinary
Yimeng Song, Yingfeng He, Yangfeng Li, Huiyun Wei, Peng Qiu, Qianming Huang, Zhiquan He, Junhui Die, Mingzeng Peng, Xinhe Zheng
Summary: In this study, GaN thin films were grown directly on monolayer MoS2 for the first time using plasma-enhanced atomic layer deposition. Various characterization methods revealed the crystalline structure of GaN and the interface properties with mono-MoS2. The growth of GaN on MoS2 was found to follow the Stranski-Krastanov mode, with different growth phases observed depending on the ALD cycles.
CRYSTAL GROWTH & DESIGN
(2021)
Article
Materials Science, Coatings & Films
Lakshman Srinivasan, Cyril Jadaud, Francois Silva, Jean-Charles Vanel, Jean-Luc Maurice, Erik Johnson, Pere Roca i Cabarrocas, Karim Ouaras
Summary: We successfully grew polycrystalline GaN thin films on Si (100) substrates at room temperature using radiofrequency reactive magnetron sputtering, with Ar and N-2 as the main sputtering and N-atom precursor gas sources, respectively. The effect of working pressure on the thin film's crystalline quality was studied, and it was found that pressures below 50 mTorr result in amorphous films, while pressures above 50 mTorr result in polycrystalline films. The films grown at 50 mTorr exhibited the best crystallinity with a dominant wurtzite hexagonal structure, and a uniform elemental distribution of Ga and N throughout the growth profile.
JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A
(2023)
Article
Chemistry, Multidisciplinary
Xiaoyan Wu, Wei Li, Qingrong Chen, Caixia Xu, Jiamian Wang, Lingyuan Wu, Guodong Liu, Weiping Wang, Ting Li, Ping Chen, Long Xu
Summary: Light-induced degradation (LID) phenomenon is commonly found in optoelectronics devices. This study investigates the self-healing effect in halide lead perovskite solar cells and the role of deep defect and vacancy traps in the LID and healing process of photocurrent in p-type Mg-doped gallium nitride thin films.
Article
Chemistry, Physical
Libin Liang, Katrina Czar, Madalina Furis
Summary: This research investigates the potential of strain engineering in promoting the formation of delocalized excitonic states in organic semiconductors. The results demonstrate that tensile strain leads to the formation of delocalized excitons, accompanied by enhanced photoluminescence intensity and red shift in peak wavelength. These findings offer promising prospects for achieving delocalization at room temperature through strain engineering.
JOURNAL OF PHYSICAL CHEMISTRY C
(2022)
Article
Chemistry, Physical
Patrick Fiorenza, Emanuela Schiliro, Giuseppe Greco, Marilena Vivona, Marco Cannas, Filippo Giannazzo, Raffaella Lo Nigro, Fabrizio Roccaforte
Summary: The study investigates charge trapping phenomena in Al2O3 thin films grown on AlGaN/GaN heterostructures by ALD, using time-dependent C-V measurements. Results show competitive mechanisms for electron capture and emission in the Al2O3 film, as well as the presence of oxygen-related point defects with only a fraction being electrically active. These findings are valuable for understanding the thermal stability of trapping phenomena and potential applications in real devices.
APPLIED SURFACE SCIENCE
(2022)
Article
Materials Science, Multidisciplinary
M. A. Borysiewicz, M. Juchniewicz, P. Prystawko, A. Zagojski, M. Wzorek, M. Ekielski, K. Pagowska, W. Zaleszczyk
Summary: This study proposes a method to fabricate porous gallium nitride films by ion implantation without the need for wet chemical etching or high donor concentrations. The properties of the created nanostructures were analyzed through structural, optical, and electrical studies. The study also compared the effects of single and double ion implantation.
Article
Chemistry, Physical
Austin M. Cano, Ann Lii-Rosales, Steven M. George
Summary: Thermal atomic layer etching (ALE) of amorphous and crystalline aluminum nitride was investigated using different reactants. The etching mechanism and etch rates were analyzed using Fourier transform infrared spectroscopy and in situ spectroscopic ellipsometry. X-ray photoelectron spectroscopy and quadrupole mass spectrometry studies provided further insights into the chemical reactions observed in the experiments.
JOURNAL OF PHYSICAL CHEMISTRY C
(2022)
Article
Chemistry, Physical
Ann Lii-Rosales, Virginia L. Johnson, Sandeep Sharma, Andreas Fischer, Thorsten Lill, Steven M. George
Summary: NiCl2, PdCl2, and PtCl2 can form stable and volatile complexes by adding the ligand P(Me)3. In these ligand-addition reactions, MCl2(P(Me)3)2 is the most common product. In situ QMS studies confirmed the formation of volatile metal complexes after exposing the metal chlorides to P(Me)3. Thermochemical calculations also showed that adding P(Me)3 to MCl2 and MCl2(P(Me)3) is favorable. These findings suggest that thermal atomic layer etching of Ni, Pd, and Pt may be possible based on sequential chlorination and ligand-exchange reactions.
JOURNAL OF PHYSICAL CHEMISTRY C
(2022)
Article
Materials Science, Coatings & Films
Austin M. Cano, Suresh Kondati Natarajan, Jonathan L. Partridge, Simon D. Elliott, Steven M. George
Summary: This study investigated the chemical vapor etching (CVE) of boron oxide (B2O3) by hydrogen fluoride (HF) gas. The etching process was monitored using Fourier transform infrared spectroscopy (FTIR) and quadrupole mass spectrometry (QMS). The experimental results and predictions from density functional theory (DFT) were consistent, indicating the spontaneous etching of B2O3 by HF gas under certain conditions.
JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A
(2022)
Article
Chemistry, Physical
Austin M. Cano, Jonathan L. Partridge, Steven M. George
Summary: The study demonstrates the atomic layer etching of Al2O3 using sequential HF and BCl3 exposures, revealing that BCl3 can provide pathways for both ligand-exchange and conversion mechanisms. The results show that thermal Al2O3 ALE primarily involves HF fluorination of Al2O3 followed by BCl3 removal of surface fluoride layer through ligand-exchange reaction. However, evidence suggests that some Al2O3 conversion to B2O3 still occurs during subsequent BCl3 exposures.
CHEMISTRY OF MATERIALS
(2022)
Article
Polymer Science
Olivia M. McIntee, Brian C. Welch, Alan R. Greenberg, Steven M. George, Victor M. Bright
Summary: Molecular layer deposition (MLD) is a gas-phase deposition technique that can create ultra-thin films with controlled composition and thickness. In this study, MLD was used to fabricate crosslinked polyamide films, and their elastic modulus was determined using atomic force microscopy. The results showed that the modulus was independent of film thickness, comparable to thicker polyamide films.
Article
Chemistry, Physical
Ann Lii-Rosales, Virginia L. Johnson, Andrew S. Cavanagh, Andreas Fischer, Thorsten Lill, Sandeep Sharma, Steven M. George
Summary: The spontaneous etching of metal fluorides by different ligands was investigated, and it was found that F/Cl ligand exchange was the most effective, yielding metal chlorides. F/H exchange was also observed under certain conditions. These results provide guidelines for designing precursors for thermal ALE processes.
CHEMISTRY OF MATERIALS
(2022)
Article
Chemistry, Physical
Zachary C. Sobell, Steven M. George
Summary: TiN films were grown using electron-enhanced atomic layer deposition (EE-ALD) with the help of a hollow cathode plasma electron source and continuous NH3 reactive background gas. This technique allowed for high quality film growth on different substrates and the ability to tune the composition and properties of the films.
CHEMISTRY OF MATERIALS
(2022)
Article
Materials Science, Coatings & Films
Jonas C. Gertsch, Jonathan L. Partridge, Austin M. Cano, Joel W. Clancey, Victor M. Bright, Steven M. George
Summary: The thermal atomic layer etching (ALE) of VO2 was demonstrated using sequential exposures of BCl3 and SF4. The VO2 etch rate varied from 0.05 angstrom/cycle at 150℃ to 2.3 angstrom/cycle at 250℃. Fourier transform infrared (FTIR) spectroscopy studies showed the conversion of VO2 to B2O3 during BCl3 exposures and the fluorination of VO2 to form VOF3 by SF4. The etching reactions involved multiple pathways including conversion, ligand-exchange, and oxidation state changes.
JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A
(2023)
Article
Chemistry, Physical
Jessica A. Murdzek, Virginia L. Johnson, Andrew S. Cavanagh, Andreas Fischer, Thorsten Lill, Sandeep Sharma, Jonathan L. Partridge, Steven M. George
Summary: Thermal atomic layer etching (ALE) of CoO, ZnO, Fe2O3, and NiO was achieved at 250 degrees C using chlorination and ligand-addition reactions. Metal oxide powders formed stable and volatile MCl2(TMEDA) compounds as etch products. A new reactor design with two nested inlet lines allowed for in situ quadrupole mass spectrometry (QMS) studies of the sequential reactions. The etching of other metal oxides was also investigated, with V2O5 and CuO showing spontaneous etching using SO2Cl2 at 250 degrees C.
CHEMISTRY OF MATERIALS
(2023)
Article
Materials Science, Coatings & Films
Jessica A. Murdzek, Ann Lii-Rosales, Steven M. George
Summary: Researchers developed a thermal atomic layer etching method for cobalt using sulfuryl chloride (SO2Cl2) for chlorination and either tetramethylethylenediamine (TMEDA) or trimethylphosphine (PMe3) for ligand addition. In situ quartz crystal microbalance (QCM) measurements were used to monitor the etching process. The results showed that there was a net removal of cobalt during each chlorination/ligand-addition reaction cycle. The etch rates were determined at different temperatures and verified using x-ray reflectivity (XRR) studies. The chlorination and ligand-addition mechanism can be applied to metal etching for metals that form stable chlorides.
JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A
(2023)
Article
Chemistry, Physical
Jonathan L. Partridge, Aziz I. Abdulagatov, Varun Sharma, Jessica A. Murdzek, Andrew Cavanagh, Steven M. George
Summary: Thermal atomic layer etching (ALE) of CoO was demonstrated using sequential exposures of acetylacetone (Hacac) and ozone (O3). The surface reactions involved the removal of CoO by Hacac and the elimination of carbon residue by ozone. In situ spectroscopic ellipsometry showed a linear decrease in CoO film thickness with etch rate of 0.43 & ANGS;/cycle at 250 degrees C. The CoO film underwent changes in oxidation state and crystal structure during each reactant exposure. Ex situ grazing incidence X-ray diffraction (GIXRD) and X-ray photoelectron spectroscopy (XPS) confirmed the oxidation state of different cobalt oxides. Quadrupole mass spectrometry and atomic force microscopy measurements also provided insights into the etching process and surface roughness reduction during CoO ALE.
APPLIED SURFACE SCIENCE
(2023)
Article
Chemistry, Physical
Taewook Nam, Jonathan L. Partridge, Steven M. George
Summary: Thermal atomic layer etching (ALE) of zinc sulfide (ZnS) was successfully performed using sequential exposures of Al(CH3)(3) and HF. The etch rate of ZnS increased with temperature and the possible mechanisms for etching were fluorination and ligand exchange. QMS results provided direct evidence for the conversion of ZnS to Al2S3 during ZnS ALE. The etching reactions were found to be self-limiting.
CHEMISTRY OF MATERIALS
(2023)
Article
Materials Science, Coatings & Films
Michael A. Collings, Marcel Junige, Andrew S. Cavanagh, Victor Wang, Andrew C. Kummel, Steven M. George
Summary: In this study, ruthenium thin films were successfully deposited using electron-enhanced atomic layer deposition technique, which allowed for rapid growth of the films through electron-stimulated desorption. Forming gas anneal effectively removed carbon impurities from the deposited films and resulted in high purity films with low resistivity.
JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A
(2023)