Article
Nanoscience & Nanotechnology
Tauno Kahro, Aivar Tarre, Tanel Kaambre, Helle-Mai Piirsoo, Jekaterina Kozlova, Peeter Ritslaid, Aarne Kasikov, Taivo Jogiaas, Guillermo Vinuesa, Salvador Duenas, Helena Castan, Aile Tamm, Kaupo Kukli
Summary: Thin HfO2 films were grown on large-area graphene by atomic layer deposition, and the resistive switching characteristics were modified in the graphene-HfO2 stacks. Surface pretreatments of the Si/TiN/HfO2 substrates were studied to improve graphene transfer.
ACS APPLIED NANO MATERIALS
(2021)
Article
Chemistry, Multidisciplinary
Tauno Kahro, Kristina Raudonen, Joonas Merisalu, Aivar Tarre, Peeter Ritslaid, Aarne Kasikov, Taivo Jogiaas, Tanel Kaambre, Markus Otsus, Jekaterina Kozlova, Harry Alles, Aile Tamm, Kaupo Kukli
Summary: In this study, SiO2 films were grown to thicknesses below 15 nm using ozone-assisted atomic layer deposition, and continuous HfO2 or SiO2 films were deposited on graphene layer as conductive layer. Graphene layer was used as resistive switching media and improved endurance characteristics of the devices.
Article
Materials Science, Ceramics
Hee Ju Yun, Sung Yeon Ryu, Ha Young Lee, Woo Young Park, Soo Gil Kim, Byung Joon Choi
Summary: Rare-earth oxide materials show interesting resistive switching properties in resistive switching memory. Post-deposition annealing of GdOx films enhances the tunability of resistance states, which is beneficial for multi-level operation. The effects of crystallization and hygroscopic nature of GdOx film on resistive switching characteristics are investigated.
CERAMICS INTERNATIONAL
(2021)
Article
Chemistry, Physical
Lauri Aarik, Karmo Peetermann, Laurits Puust, Hugo Mandar, Arvo Kikas, Ilmo Sildos, Jaan Aarik
Summary: Atomic layer deposition of praseodymium oxide films allows for uniform doping of HfO2 films with non-uniform thicknesses. The absorption of oxygen in PrOx-rich material enhances ALD growth, leading to thickness gradients in thicker films. Pr-doping stabilizes the tetragonal form and improves photoluminescence efficiencies in HfO2 films.
JOURNAL OF ALLOYS AND COMPOUNDS
(2021)
Article
Chemistry, Multidisciplinary
Ivana Zrinski, Cezarina Cela Mardare, Luiza-Izabela Jinga, Jan Philipp Kollender, Gabriel Socol, Alexey Minenkov, Achim Walter Hassel, Andrei Ionut Mardare
Summary: Anodic HfO2 memristors grown in different electrolytes exhibit varying performance, with citrate showing superior properties while borate performs the weakest. Various tests were conducted on the memristors, including the influence of low temperature heating and the stability of operation at high temperatures.
Article
Computer Science, Information Systems
Markus Otsus, Joonas Merisalu, Aivar Tarre, Anna-Liisa Peikolainen, Jekaterina Kozlova, Kaupo Kukli, Aile Tamm
Summary: This study evaluated the effects of chemically presynthesised nickel nanoparticles embedded in a dielectric layer on the structure and resistive switching properties. The results showed that the addition of nickel nanoparticles improved the resistive switching properties.
Article
Energy & Fuels
Xiao-Ying Zhang, Jing Han, Yao-Tian Wang, Yu-Jiao Ruan, Wan-Yu Wu, Dong-Sing Wuu, Juan Zuo, Feng-Min Lai, Shui-Yang Lien, Wen-Zhang Zhu
Summary: Hafnium oxide (HfO2) thin film is studied as a passivation layer for crystalline silicon (c-Si). The electrical characterization and measurements of HfO2 films on P-type and N-type c-Si were conducted. Post annealing in different gas ambients was performed. The results reveal the potential of HfO2 for field effect and chemical passivation. The impacts of post-annealing gas ambient on passivation qualities on Si by HfO2 thin films are systematically studied.
SOLAR ENERGY MATERIALS AND SOLAR CELLS
(2023)
Article
Chemistry, Physical
Seon Yong Kim, Yong Chan Jung, Sejong Seong, Taehoon Lee, In-Sung Park, Jinho Ahn
Summary: The growth of HfOx films using La(NO3)(3)center dot 6H(2)O solution as an oxidant was investigated in comparison to films grown using conventional oxidant H2O. The films grown with LNS showed smaller crystallites, more suboxides or defects, and different preferred orientations compared to those grown with H2O. These differences were attributed to a variation in surface energy between the two deposition processes. A film growth model based on surface energy difference was proposed to explain the observed trends in growth rate and crystallite size.
Article
Nanoscience & Nanotechnology
Zhihua Yong, Mamidala Saketh Ram, Karl-Magnus Persson, Gomathy Sandhya Subramanian, Lars-Erik Wernersson, Jisheng Pan
Summary: Titanium nitride and hafnium oxide stack, which are compatible with complementary-metal-oxide-semiconductor, have been widely used in resistive memory elements. This study compares HfOx grown using plasma enhanced atomic layer deposition (PEALD) and thermal atomic layer deposition (TALD) in terms of band alignment and electrical performances in the HfOx/PEALD TiN stacks. The findings show the significance of understanding the intricate details of the material stack, such as delta E-C difference and the presence of a thicker TiO2 interfacial layer, in affecting the device performance.
ADVANCED ELECTRONIC MATERIALS
(2022)
Article
Chemistry, Physical
Mirine Leem, Deokjoon Eom, Heesoo Lee, Kwangwuk Park, Kwangsik Jeong, Hyoungsub Kim
Summary: In this study, HZO films were grown directly on single-crystalline MoS2 flakes using ALD with H2O or O3 oxidants. The O3-based ALD process oxidizes the MoS2 surface at the atomic layer level and facilitates the conformal deposition of an HZO film without surface treatment of MoS2. Annealing the O3-based HZO film significantly improves the ferroelectric properties, but also leads to diffusion of S, Hf, Zr, and O towards the Mo layer, reducing the weak HZO bonds.
APPLIED SURFACE SCIENCE
(2023)
Article
Nanoscience & Nanotechnology
Tao Wang, Stefano Brivio, Elena Cianci, Claudia Wiemer, Michele Perego, Sabina Spiga, Mario Lanza
Summary: This study fabricates RS devices based on a TaOx/HfO2 bilayer stack and improves their switching performance and reliability by modifying the structure of the oxide.
ACS APPLIED MATERIALS & INTERFACES
(2022)
Article
Physics, Applied
Punya Mainali, Lyndon D. Bastatas, Elena Echeverria, Phadindra Wagle, Prasanna Sankaran, D. N. Mcilroy
Summary: The resistive switching ZnO n-n homojunction diode fabricated with a stack of two dissimilar ZnO thin films shows promising characteristics for addressing the crosstalk problem in a crossbar memory array. The device exhibits a characteristic I-V-hysteresis loop and the maximum ratio of high resistive state to low resistive state occurs at 1 kHz ac signal at 3 V.
JOURNAL OF APPLIED PHYSICS
(2021)
Article
Materials Science, Ceramics
Jihyun Kim, Sungje Lee, Yiwen Song, Sukwon Choi, Jihwan An, Jungwan Cho
Summary: The thermal conductivity of plasma-enhanced atomic layer deposited (PEALD) HZO thin films was investigated. It was found that the effective thermal conductivity slightly decreases with increasing yttrium doping level due to dopant scattering of phonons. The PEALD HZO films were observed to be nanocrystalline.
JOURNAL OF THE EUROPEAN CERAMIC SOCIETY
(2021)
Article
Materials Science, Multidisciplinary
Clemens Mart, Nico-Dominik Kohlenbach, Kati Kuehnel, Sophia Esslinger, Malte Czernohorsky, Tarek Ali, Wenke Weinreich, Lukas M. Eng
Summary: The HfO2 material system has excellent physical properties for various applications, but long-term stability is a key concern. This study reveals the aging effects of the pyroelectric response in Si-doped HfO2 thin films, showing that aging is accelerated by high temperatures, lower film thicknesses, and higher dopant concentrations. The decay of pyroelectric coefficients and dielectric permittivity follows a logarithmic time dependence, and repeated electric field cycling can restore the full pyroelectric response. The significant internal bias field observed after aging is attributed to the migration of positively charged oxygen vacancies in the films.
PHYSICA STATUS SOLIDI-RAPID RESEARCH LETTERS
(2021)
Article
Chemistry, Multidisciplinary
Kristjan Kalam, Markus Otsus, Jekaterina Kozlova, Aivar Tarre, Aarne Kasikov, Raul Rammula, Joosep Link, Raivo Stern, Guillermo Vinuesa, Jose Miguel Lendinez, Salvador Duenas, Helena Castan, Aile Tamm, Kaupo Kukli
Summary: HfO2 and Fe2O3 thin films and laminated stacks were grown by atomic layer deposition, and nonlinear, saturating, and hysteretic magnetization behavior was observed. Magnetization was mainly influenced by the content of Fe2O3, but the choice of appropriate ratios of HfO2 and Fe2O3 could enhance coercive force.
Article
Chemistry, Multidisciplinary
Kristjan Kalam, Markus Otsus, Jekaterina Kozlova, Aivar Tarre, Aarne Kasikov, Raul Rammula, Joosep Link, Raivo Stern, Guillermo Vinuesa, Jose Miguel Lendinez, Salvador Duenas, Helena Castan, Aile Tamm, Kaupo Kukli
Summary: HfO2 and Fe2O3 thin films and laminated stacks were grown by atomic layer deposition, and nonlinear, saturating, and hysteretic magnetization behavior was observed. Magnetization was mainly influenced by the content of Fe2O3, but the choice of appropriate ratios of HfO2 and Fe2O3 could enhance coercive force.
Article
Chemistry, Multidisciplinary
Lauri Aarik, Tonis Arroval, Peeter Ritslaid, Agnes Vask, Hugo Maendar, Jaan Aarik
Summary: Atomic layer deposition of HfxTi1-xOy films on various substrates was investigated and the crystal structure and impurity concentration were analyzed. Different phases of TiO2 and HfO2 were formed depending on the composition of the films and the substrate used. The crystal structure of the films had an influence on the chlorine impurity concentration and the permittivity of the films increased with decreasing Hf content.
CRYSTAL GROWTH & DESIGN
(2023)
Article
Chemistry, Physical
Jonas Mart Linge, Heiki Erikson, Marek Mooste, Helle-Mai Piirsoo, Tiit Kaljuvee, Arvo Kikas, Jaan Aruvali, Vambola Kisand, Aile Tamm, Arunachala M. Kannan, Kaido Tammeveski
Summary: Two different wet chemical methods were used to deposit silver nanocatalyst (40 wt%) on commercial mesoporous carbon support material (Ag/C) to enhance the electrochemically active surface area. The catalyst materials were characterized using various analytical techniques and evaluated for oxygen reduction reaction (ORR) in alkaline media. The Ag/C catalyst exhibited higher mass activity for ORR compared to Vulcan carbon, showing potential for application in anion exchange membrane fuel cells.
INTERNATIONAL JOURNAL OF HYDROGEN ENERGY
(2023)
Article
Chemistry, Analytical
Gulnara Yusibova, Jurgen-Martin Assafrei, Kefeng Ping, Jaan Aruvali, Paam Paiste, Maike Kaarik, Jaan Leis, Helle-Mai Piirsoo, Aile Tamm, Arvo Kikas, Vambola Kisand, Pavel Starkov, Nadezda Kongi
Summary: This study presents a new ligand-enabled strategy for incorporating dual metals into metal-organic-framework-derived bifunctional oxygen electrocatalysts. The involvement of bimetallic systems reduces the need for critical raw materials and enhances the overall electroactivity of the catalyst. A mixed-metal manganese/cobalt metal-organic framework (TAL-42) is introduced as a versatile single precursor for the facile preparation of highly efficient bifunctional oxygen electrocatalysts. The TAL-42-900 material exhibits superior bifunctional oxygen reduction/evolution reaction performance compared to a commercial Pt/C + RuO2 catalyst.
JOURNAL OF ELECTROANALYTICAL CHEMISTRY
(2023)
Article
Optics
Shivasubramanian Gopinath, Praveen Periysamy Angamuthu, Tauno Kahro, Andrei Bleahu, Francis Gracy Arockiaraj, Daniel Smith, Soon Hock Ng, Saulius Juodkazis, Kaupo Kukli, Aile Tamm, Vijayakumar Anand
Summary: In this study, a large-area diffractive lens with three sub-aperture diffractive lenses was realized using a Golay-like configuration, which relaxes the fabrication constraints and improves the imaging resolution. The computational optical experiments demonstrated enhanced optical and computational imaging resolutions compared to previous studies.
Article
Physics, Applied
H. Garcia, G. Vinuesa, E. Garcia-Ochoa, F. L. Aguirre, M. B. Gonzalez, F. Jimenez-Molinos, F. Campabadal, J. B. Roldan, E. Miranda, S. Duenas, H. Castan
Summary: The effect of applied voltage ramp rate on the electrical properties of metal-insulator-metal resistive switching devices has been studied. It is shown that higher ramp rates allow control over the resistance values, which suggests a new way to program synaptic weights in neuromorphic engineering applications.
JOURNAL OF PHYSICS D-APPLIED PHYSICS
(2023)
Article
Engineering, Electrical & Electronic
G. Vinuesa, H. Garcia, J. M. Lendinez, E. Garcia-Ochoa, M. B. Gonzalez, D. Maldonado, C. Aguilera-Pedregosa, E. Moreno, F. Jimenez-Molinos, J. B. Roldan, F. Campabadal, H. Castan, S. Duenas
Summary: The unipolar resistive switching behavior of Ni/HfO2/Si(n+) devices is investigated. Current and voltage sweeps are used to characterize the structures, and the device resistance and cycle-to-cycle variability are analyzed in each case. Experimental measurements show that using current sweeps improves the stability of resistance states during both set and reset processes. It is also found that using current to induce these transitions is more efficient than using voltage sweeps, as indicated by the device power consumption. Similar results are obtained for devices with a Ni top electrode and a bilayer or pentalayer of HfO2/Al2O3 as the dielectric. Finally, kinetic Monte Carlo and compact modeling simulations are performed to provide insights into the experimental results.
MICROELECTRONIC ENGINEERING
(2023)
Article
Chemistry, Physical
Helle-Mai Piirsoo, Taivo Jogiaas, Kaupo Kukli, Aile Tamm
Summary: The mechanical properties of nanodevices are greatly influenced by the mechanical properties of thin films. Amorphous Al2O3-Ta2O5 double and triple layers were deposited with various single-layer thicknesses. Annealing at different temperatures caused changes in the microstructure, resulting in the formation of different crystalline grains. The hardness and elastic modulus of the annealed laminates depended on the layer sequence, indicating the significant influence of the layered structure on the mechanical behavior.
Article
Chemistry, Physical
Jonas Mart Linge, Heiki Erikson, Peeter Ritslaid, Arvo Kikas, Vambola Kisand, Jaan Aruvali, Jekaterina Kozlova, Aile Tamm, Ave Sarapuu, Kaido Tammeveski
Summary: In this study, MnO2 and multiwalled carbon nanotube (MWCNT) composites decorated with silver were prepared to evaluate their electrocatalytic activity towards the oxygen reduction reaction (ORR). The physicochemical characterisation was done using scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy. The electrochemical studies revealed that the activity and stability of the composite catalysts depend on the substrate material and the thickness of the silver layer.
Article
Chemistry, Multidisciplinary
Tauno Kahro, Kristina Raudonen, Joonas Merisalu, Aivar Tarre, Peeter Ritslaid, Aarne Kasikov, Taivo Jogiaas, Tanel Kaambre, Markus Otsus, Jekaterina Kozlova, Harry Alles, Aile Tamm, Kaupo Kukli
Summary: In this study, SiO2 films were grown to thicknesses below 15 nm using ozone-assisted atomic layer deposition, and continuous HfO2 or SiO2 films were deposited on graphene layer as conductive layer. Graphene layer was used as resistive switching media and improved endurance characteristics of the devices.
Article
Nanoscience & Nanotechnology
Kristjan Kalam, Peeter Ritslaid, Tanel Kaeaembre, Aile Tamm, Kaupo Kukli
Summary: Polycrystalline SnO2 thin films were successfully grown on SiO2/Si(100) substrates using atomic layer deposition. The relationship between growth per cycle and substrate temperature was determined, and crystal growth was observed in the temperature range of 225-600 degrees C. Spectroscopic analyses revealed low residual iodine content and the formation of single-phase oxide in films grown at temperatures above 300 degrees C. The suitability of the precursor system for preparing SnO2 films was confirmed.
BEILSTEIN JOURNAL OF NANOTECHNOLOGY
(2023)
