Ville Vähänissi

Scopus Publications

Nanostructuring SiC by sequential plasma oxidation and reactive ion etching
Joonas Isometsä, Auguste Bieleviciute, Xiaolong Liu, Ville Vähänissi, Hele Savin
Applied Surface Science, 2026
Publisher Copyright: © 2026 The Authors
Challenges in Simultaneous Microstructuring and Hyperdoping of Germanium with Ultrafast Laser
Dmytro Gnatyuk, Sara Hamed, Masoud Ebrahimzadeh, Hanchen Liu, Ville Vähänissi, Pekka Laukkanen, Hele Savin, Xiaolong Liu
Physica Status Solidi A Applications and Materials Science, 2026
Germanium's compatibility with Complementary Metal‐Oxide‐Semiconductor (CMOS) and strong near‐infrared response make it an attractive platform for infrared photonics, but its intrinsic material properties hinder straightforward extension of absorption beyond the band edge. In this perspective, we synthesize recent and new experiments and analyses on femtosecond‐laser approaches that attempt to combine surface microstructuring and hyperdoping of Ge in a single step. We argue that, unlike silicon, Ge's high optical absorption at visible/green wavelengths, shallow energy deposition, lower melting point, and reduced thermal conductivity favor intense localized heating, evaporation, and redeposition—conditions that both produce high baseline sub‐bandgap absorption from damage and prevent effective incorporation of thin‐film dopant precursors. In a case example, Ti shows only trace incorporation from qualitative measurements. We discuss why laser‐induced structural disorder, rather than stable deep dopant incorporation, dominates the optical response, and we outline practical pathways forward: exploring longer wavelengths or gas‐phase chemistries, applying separate in situ heating, or decoupling texturing from heavy doping.
Carrier mobility in crystalline germanium at high injection: experimental characterization of carrier-carrier scattering
Moisés Garín, Mansur Gamel, Marko Yli-Koski, Ville Vähänissi, Gerard Rivera, Hele Savin, Isidro Martín
Solar Energy Materials and Solar Cells, 2026
The decay of the sum of electron and hole mobilities, μ s = μ n + μ p , due to carrier-carrier scattering was experimentally investigated in crystalline germanium (Ge) at high-injection conditions. Contactless measurements of the mobility sum as a function of the excess carrier density (Δ n ) in Ge were obtained using photoconductance decay methods. First, the measurement method was revised and improvements were introduced to ensure that μ s (Δ n ) could be obtained for independent samples with improved accuracy. This method is successfully validated with crystalline silicon and, then, applied to Ge samples of different doping types and resistivity. The analysis of the data suggests that the mobility decay at high injection levels cannot be properly explained with the usual assumption of equal cross section for carrier-carrier and carrier-ion scattering events. Instead, we find the mobility sum due to carrier-carrier scattering to be inversely proportional to Δ n according to the expression 8 × 10 20 ·Δ n −1 cm 2 V −1 s −1 . The limitations and potential error sources of the measurement method are discussed and, finally, the mobility model is used to improve lifetime analysis at high injection, allowing to estimate the ambipolar Auger recombination coefficient at C amb = 7 × 10 −31 cm 6 s −1 .
Bipolar and unipolar charge transfer during the formation of silicon/iodine solution interfaces
Shengyang Li, Mahdi Alizadeh, Ville Vähänissi, Hele Savin, Guangwei She, Wensheng Shi, Jani Oksanen
Surfaces and Interfaces, 2026
Transforming Schottky to Ohmic Contacts via Ultrahigh-Vacuum Engineered Interfacial Alloying
Masoud Ebrahimzadeh, Perttu Piispanen, Sari Granroth, Mikko Miettinen, Ilari Angervo, Hanchen Liu, Markus Otsus, Risto Punkkinen, Marko Punkkinen, Ville Vähänissi, Kalevi Kokko, Petriina Paturi, Kaupo Kukli, Hele Savin, Pekka Laukkanen
ACS Applied Materials and Interfaces, 2025
Low-resistive Ohmic contacts are needed in most microelectronics and photonics devices to connect a device to the electric circuit. Manufacturing of Ohmic contacts typically requires the doping of a semiconductor surface region as n-type or p-type (i.e., electron- or hole-doped, respectively). This task has, however, become challenging when the doping needs to be controlled with nanometer or even atomic level precision at lowered processing temperatures. In this work, we demonstrate a low-temperature method to tackle this contact manufacturing challenge using ultrathin antimony (Sb) doped germanium (Ge) nanolayers. We have integrated the method with the common lift-off processing to make Ohmic nickel (Ni) contacts on low-doped n-type Ge and Si substrates and on semi-insulating GaAs, which initially show the Schottky contacts. A proper combination of wet chemical cleaning plus depositing Sb and Ge atomic layers on the substrates, kept at room temperature, in a very clean environment of ultrahigh vacuum before the Ni-film deposition and postmetallization heating changes the Schottky contacts to Ohmic ones. Complementary methods are used to probe the physicochemical properties of interfaces during the manufacturing process to clarify the mechanisms behind the Ohmic-contact formation.
Impact of Er-Based Atomic Layer Deposited Upconverting Oxides on Si Solar Cell Surface Passivation
Behrad Radfar, Amr Ghazy, Joona Pekkanen, Xiaolong Liu, Ville Vähänissi, Maarit Karppinen, Hele Savin
Physica Status Solidi A Applications and Materials Science, 2025
Crystalline silicon solar cells face fundamental limitations in infrared (IR) absorption leading to significant solar energy losses. Using upconverting (UC) rare‐earth oxide layers is a potential solution to convert sub‐bandgap photons into higher‐energy photons that Si can absorb. However, integrating UC layers into solar cells can potentially affect surface passivation properties, which may result in recombination of photogenerated charge carriers at Si/UC interface. This study investigates the impact of atomic‐layer‐deposited mixed rare‐earth oxide (Y,Er,Ho)2O3 and Er2O3 UC layers on the passivation quality of Si interface, deposited directly on Si substrate or on the conventional passivation layers, i.e., SiO2 and Al2O3. Findings reveal that direct deposition provides very weak passivation (τeff ≈ 4.1 μs) which does not improve with post‐deposition annealing. Similarly, when deposited on top of SiO2 with optically relevant thickness, the resulting passivation is poor. However, UC layer on top of Al2O3 does not compromise the passivation performance, resulting in low surface recombination velocity of 1.5 cm s−1 for Er2O3 and 1.4 cm s−1 for (Y,Er,Ho)2O3. Consequently, the results indicate that it should be viable to integrate UC layer like Er2O3 into a state‐of‐the‐art solar cell to improve sub‐bandgap absorption without compromising the passivation properties.
Near-infrared germanium PIN-photodiodes with >1A/W responsivity
Hanchen Liu, Toni P. Pasanen, Tsun Hang Fung, Joonas Isometsä, Antti Haarahiltunen, Steven Hesse, Lutz Werner, Ville Vähänissi, Hele Savin
Light Science and Applications, 2025
Even though efficient near-infrared (NIR) detection is critical for numerous applications, state-of-the-art NIR detectors either suffer from limited capability of detecting incoming photons, i.e., have poor spectral responsivity, or are made of expensive group III-V non-CMOS compatible materials. Here we present a nanoengineered PIN-photodiode made of CMOS-compatible germanium (Ge) that achieves a verified external quantum efficiency (EQE) above 90% over a wide wavelength range (1.2–1.6 µm) at zero bias voltage at room temperature. For instance, at 1.55 µm, this corresponds to a responsivity of 1.15 A/W. In addition to the excellent spectral responsivity at NIR, the performance at visible and ultraviolet wavelengths remains high (EQE exceeds even 100% below 300 nm) resulting in an exceptionally wide spectral response range. The high performance is achieved by minimizing optical losses using surface nanostructures and electrical losses using both conformal atomic-layer-deposited aluminum oxide surface passivation and dielectric induced electric field -based carrier collection instead of conventional pn-junction. The dark current density of 76 µA/cm2 measured at a reverse bias of 5 V is lower than previously reported for Ge photodiodes. The presented results should have an immediate impact on the design and manufacturing of Ge photodiodes and NIR detection in general.
Charged thin film enables dopant free ohmic metal–semiconductor contact formation
Lassi Lahtiluoma, Olli E. Setälä, Ville Vähänissi, Hele Savin
Applied Surface Science, 2025
• Externally doping a semiconductor damages the lattice and increases recombination. • Surface carrier concentration can be increased by depositing a charged thin film. • Thin film induced carriers can be used to realize a dopant free ohmic contact. • Opening a charged thin film causes carriers to drift under the opening. • Contact resistivity of 0.24 mΩcm 2 was achieved with thin film induced contacts. Ohmic contacts are conventionally achieved by externally doping the surface of a semiconductor substrate underneath a metal contact. To avoid the inconveniences that come with heavy doping, we propose an alternative way of achieving an ohmic Al-Si contact utilizing a highly charged atomic layer deposited (ALD) Al 2 O 3 thin film. The idea is to utilize the negative charge of ALD Al 2 O 3 to attract holes towards the surface of the Si substrate and thereby induce a p+ region and consequently an Al/p+ Si contact. The results show that the Al 2 O 3 induced contacts are not only ohmic, but also have a low contact resistivity of 0.24 mΩ⋅cm 2 . This matches the requirements of various electron devices such as photodiodes indicating potential for the proposed contact formation method.
Effects of ultra-high vacuum treatments on n-type Si contact resistivity
Mikko Miettinen, Esa Vuorinen, Juha-Pekka Lehtiö, Zahra Jahanshah Rad, Risto Punkkinen, Mikhail Kuzmin, Jarno Järvinen, Ville Vähänissi, Pekka Laukkanen, Hele Savin, Kalevi Kokko
Applied Surface Science, 2025
Most electronic and photonic devices include ohmic metal–semiconductor junction(s), of which contact resistivity needs to be minimized for best efficiency of the devices. Interface defects in the junction usually degrade the junction’s performance, thus cleaning and passivation of semiconductor surface is crucial during contact fabrication. For silicon devices the RCA (Radio Corporation of America) cleaning has been the most known method. Here we have addressed the question whether it is still possible to develop Si surface treatments to decrease the contact resistivity. We have combined wet chemistry and ultra-high vacuum (UHV) heating for two cases: low and highly phosphorus-doped n-type Si. As compared to silicon surfaces treated only with wet chemistry, the contact resistivity is lowered when (i) lowly doped n-Si is rapidly heated at temperature around 1200 ° C in UHV followed by hydrofluoric (HF) acid dip before Ni sputtering; (ii) p-Si substrate with highly n-type surface is first immersed in HF, then UHV heated at 400 ° C followed by immersion to HF. Our results show that the final HF dip decreases surface oxide formation in air during sample transfer to the metal deposition, and that surface phosphorus concentration decreases at highly doped n-Si surfaces during elevated temperature UHV heating. • Effects of ultra-high vacuum (UHV) treatments on n-Si contact resistivity were studied. • Low-temperature UHV heating combined with HF-based wet chemistry decreases the Ni/n + -Si resistivity. • Significant silicide formation occurs at low temperatures, hindering standard lithography approach.
Femtosecond-laser-surface-nanostructured glass for building-integrated photovoltaics
Lingju Meng, Mohammad Awashra, Sara Hamed, Dmytro Gnatyuk, Ville Vähänissi, Ville Jokinen, Hele Savin, Xiaolong Liu
Materials and Design, 2025
Femtosecond-laser-surface-nanostructured glass for building-integrated photovoltaics. • Femtosecond-laser-nanostructured glass enhances solar concentrator efficiency. • Optimized nanostructures are achieved with optimized laser parameters. • A 55-fold increase in photocurrent compared to unprocessed glass is demonstrated. • Superhydrophobicity with 170° contact angles enables self-cleaning surfaces. • The scalable, one-step fabrication process is suitable for large-area applications. The emerging luminescent solar concentrators (LSC) for building-integrated photovoltaics (BIPV) face challenges such as narrow conversion spectrum, material degradation, high costs, and safety concerns, while their reliance on complex fabrication processes further hinders their practical application in large-area systems. In this paper, we present a novel application of femtosecond-laser-nanostructured borosilicate glass for BIPV, offering a promising alternative to traditional LSC windows. Utilizing a scalable, one-step femtosecond laser direct writing process, we fabricate nanostructured borosilicate glass specifically designed to effectively scatter incident light toward solar cells positioned at the edges of the glass. To optimize the laser processing, we perform comprehensive characterizations using scanning electron microscopy, X-ray diffraction, Raman spectroscopy, photoluminescence spectroscopy, and spectrophotometry. The proof-of-concept system demonstrates that the glass processed at an optimized scan speed exhibits a 55-fold increase in photocurrent generation compared to unprocessed glass, highlighting its enhanced optical efficiency. Additionally, a hydrophobic coating is applied on the nanostructured glass to confer self-cleaning properties, achieving superhydrophobicity with advancing and receding contact angles of approximately 170°. This novel approach to utilizing nanostructured glass for solar concentration shows considerable promise for improving both the efficiency and practicality of building-integrated photovoltaics.
Passivation of Germanium Surfaces by HF:H2O2 Aqueous Solution
Mariia Terletskaia, Joonas Isometsä, Mikko Miettinen, Pekka Laukkanen, Ville Vähänissi, Hele Savin
Physica Status Solidi Rapid Research Letters, 2025
Atomic-layer-deposited CuxCryOz thin films: Optoelectronic properties and potential application as hole-selective contacts for c-Si solar cells
Gabriel Bartholazzi, Topias Jussila, Jorit Obenlüneschloß, Ville Vähänissi, Anjana Devi, Hele Savin, Maarit Karppinen, Daniel H. Macdonald, Lachlan E. Black
Applied Surface Science, 2025
Fs-laser significantly enhances both above- and below-bandgap absorption in germanium
Xiaolong Liu, Dmytro V. Gnatyuk, Julius Halmela, Ville Vähänissi, Hele Savin
Optical Materials Express, 2025
Elimination of dead layer in silicon particle detectors via induced electric field based charge collection
Olli E. Setälä, Toni P. Pasanen, Jennifer Ott, Igors Krainukovs, Juha Heinonen, Ville Vähänissi, Hele Savin
Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment, 2025
Effective Carrier Lifetime in Ultrashort Pulse Laser Hyperdoped Silicon: Sulfur Concentration Dependence and Practical Limitations
Sören Schäfer, Xiaolong Liu, Patrick Mc Kearney, Simon Paulus, Behrad Radfar, Ville Vähänissi, Hele Savin, Stefan Kontermann
Physica Status Solidi A Applications and Materials Science, 2024
Extended Infrared Absorption in Nanostructured Si Through Se Implantation and Flash Lamp Annealing
Behrad Radfar, Xiaolong Liu, Yonder Berencén, Mohd Saif Shaikh, Slawomir Prucnal, Ulrich Kentsch, Ville Vähänissi, Shengqiang Zhou, Hele Savin
Physica Status Solidi A Applications and Materials Science, 2024
Status report on emerging photovoltaics
Annick Anctil, Meghan N. Beattie, Christopher Case, Aditya Chaudhary, Benjamin D. Chrysler, Michael G. Debije, Stephanie Essig, David K. Ferry, Vivian E. Ferry, Marina Freitag, Isaac Gould, Karin Hinzer, Harald Hoppe, Olle Inganäs, Lethy Krishnan Jagadamma, Min Hun Jee, Raymond K. Kostuk, Daniel Kirk, Stephan Kube, Minyoung Lim, Joseph M. Luther, Lorelle Mansfield, Michael D. McGehee, Duong Nguyen Minh, Preeti Nain, Matthew O. Reese, Angèle Reinders, Ifor D. W. Samuel, Wilfried van Sark, Hele Savin, Ian R. Sellers, Sean E. Shaheen, Zheng Tang, Fatima Toor, Ville Vähänissi, Ella Wassweiler, Emily L. Warren, Vincent R. Whiteside, Han Young Woo, Gang Xiong, Xitong Zhu
SPIE Selections 50 Years of Solar Energy Research, 2024
Impact of post-ion implantation annealing on Se-hyperdoped Ge
Xiaolong Liu, Patrick McKearney, Sören Schäfer, Behrad Radfar, Yonder Berencén, Ulrich Kentsch, Ville Vähänissi, Shengqiang Zhou, Stefan Kontermann, Hele Savin
Applied Physics Letters, 2024
Adsorption induced bipolar excitation at semiconductor surface
Shengyang Li, Kexun Chen, Mahdi Alizadeh, Ville Vähänissi, Hele Savin, Jani Oksanen
Surfaces and Interfaces, 2024
Contactless analysis of surface passivation and charge transfer at the TiO2-Si interface
Ramsha Khan, Xiaolong Liu, Ville Vähänissi, Harri Ali-Löytty, Hannu P. Pasanen, Hele Savin, Nikolai V. Tkachenko
Physical Chemistry Chemical Physics, 2024
Bridging the gap between surface physics and photonics
Pekka Laukkanen, Marko Punkkinen, Mikhail Kuzmin, Kalevi Kokko, Xiaolong Liu, Behrad Radfar, Ville Vähänissi, Hele Savin, Antti Tukiainen, Teemu Hakkarainen, Jukka Viheriälä, Mircea Guina
Reports on Progress in Physics, 2024
CMOS Image Sensor for Broad Spectral Range with >90% Quantum Efficiency
Olli E. Setälä, Martin J. Prest, Konstantin D. Stefanov, Douglas Jordan, Matthew R. Soman, Ville Vähänissi, Hele Savin
Small, 2023
Quantifying the Impact of Al Deposition Method on Underlying Al2O3/Si Interface Quality
Iris Mack, Kawa Rosta, Ulviyya Quliyeva, Jennifer Ott, Toni P. Pasanen, Ville Vähänissi, Zahra Sadat Jahanshah Rad, Juha-Pekka Lehtiö, Pekka Laukkanen, Caterina Soldano, Hele Savin
Physica Status Solidi A Applications and Materials Science, 2023
Status report on emerging photovoltaics
Annick Anctil, Meghan N. Beattie, Christopher Case, Aditya Chaudhary, Benjamin D. Chrysler, Michael G. Debije, Stephanie Essig, David K. Ferry, Vivian E. Ferry, Marina Freitag, Isaac Gould, Karin Hinzer, Harald Hoppe, Olle Inganäs, Lethy Krishnan Jagadamma, Min Hun Jee, Raymond K. Kostuk, Daniel Kirk, Stephan Kube, Minyoung Lim, Joseph M. Luther, Lorelle Mansfield, Michael D. McGehee, Duong Nguyen Minh, Preeti Nain, Matthew O. Reese, Angèle Reinders, Ifor D. W. Samuel, Wilfried van Sark, Hele Savin, Ian R. Sellers, Sean E. Shaheen, Zheng Tang, Fatima Toor, Ville Vähänissi, Ella Wassweiler, Emily L. Warren, Vincent R. Whiteside, Han Young Woo, Gang Xiong, Xitong Zhu
Journal of Photonics for Energy, 2023
Black Ultra-Thin Crystalline Silicon Wafers Reach the 4n2 Absorption Limit–Application to IBC Solar Cells
M. Garín, T. P. Pasanen, G. López, V. Vähänissi, K. Chen, I. Martín, H. Savin
Small, 2023
Efficient surface passivation of germanium nanostructures with 1% reflectance
Tsun Hang Fung, Joonas Isometsä, Juha-Pekka Lehtiö, Toni P Pasanen, Hanchen Liu, Oskari Leiviskä, Pekka Laukkanen, Hele Savin, Ville Vähänissi
Nanotechnology, 2023
Atomic Layer Deposition of Titanium Oxide-Based Films for Semiconductor Applications—Effects of Precursor and Operating Conditions
Vladyslav Matkivskyi, Oskari Leiviskä, Sigurd Wenner, Hanchen Liu, Ville Vähänissi, Hele Savin, Marisa Di Sabatino, Gabriella Tranell
Materials, 2023
Boron-Implanted Black Silicon Photodiode with Close-to-Ideal Responsivity from 200 to 1000 nm
Olli E. Setälä, Kexun Chen, Toni P. Pasanen, Xiaolong Liu, Behrad Radfar, Ville Vähänissi, Hele Savin
ACS Photonics, 2023
Is carrier mobility a limiting factor for charge transfer in TiO2/Si devices? A study by transient reflectance spectroscopy
Ramsha Khan, Hannu P. Pasanen, Harri Ali-Löytty, Hussein M. Ayedh, Jesse Saari, Ville Vähänissi, Mika Valden, Hele Savin, Nikolai V. Tkachenko
Surfaces and Interfaces, 2023
Plasma-enhanced atomic layer deposited SiO2 enables positive thin film charge and surface recombination velocity of 1.3 cm/s on germanium
Hanchen Liu, Toni P. Pasanen, Oskari Leiviskä, Joonas Isometsä, Tsun Hang Fung, Marko Yli-Koski, Mikko Miettinen, Pekka Laukkanen, Ville Vähänissi, Hele Savin
Applied Physics Letters, 2023
Excellent Responsivity and Low Dark Current Obtained With Metal-Assisted Chemical Etched Si Photodiode
Kexun Chen, Olli E. Setala, Xiaolong Liu, Behrad Radfar, Toni P. Pasanen, Michael D. Serue, Juha Heinonen, Hele Savin, Ville Vahanissi
IEEE Sensors Journal, 2023
Surface Passivation of Germanium with ALD Al2O3: Impact of Composition and Crystallinity of GeOx Interlayer
Joonas Isometsä, Zahra Jahanshah Rad, Tsun H. Fung, Hanchen Liu, Juha-Pekka Lehtiö, Toni P. Pasanen, Oskari Leiviskä, Mikko Miettinen, Pekka Laukkanen, Kalevi Kokko, Hele Savin, Ville Vähänissi
Crystals, 2023
Chemical Excitation of Silicon Photoconductors by Metal-Assisted Chemical Etching
Shengyang Li, Hussein M. Ayedh, Marko Yli-Koski, Ville Vähänissi, Hele Savin, Jani Oksanen
Journal of Physical Chemistry C, 2023
Optoelectronic properties of black silicon fabricated by femtosecond laser in ambient air: exploring a large parameter space
Behrad Radfar, Kexun Chen, Olli E. Setälä, Ville Vähänissi, Hele Savin, Xiaolong Liu
Optics Letters, 2023
Role of CsMnCl3Nanocrystal Structure on Its Luminescence Properties
Anastasia Matuhina, G. Krishnamurthy Grandhi, Fang Pan, Maning Liu, Harri Ali-Löytty, Hussein M. Ayedh, Antti Tukiainen, Jan-Henrik Smått, Ville Vähänissi, Hele Savin, Jingrui Li, Patrick Rinke, Paola Vivo
ACS Applied Nano Materials, 2023
Effects of Ultrahigh Vacuum Treatments on Wet Chemically Cleaned Si Surfaces
Zahra Jahanshah Rad, Mikko Miettinen, Marko Punkkinen, Pekka Laukkanen, Kalevi Kokko, Ville Vähänissi, Hele Savin
Solid State Phenomena, 2023
SPATIAL UNIFORMITY OF BLACK SILICON INDUCED JUNCTION PHOTODIODE RESPONSIVITY
Juha Heinonen, Antti Haarahiltunen, Ville Vähänissi, Toni Pasanen, Hele Savin, Juha Toivanen, Mikko Juntunen
Proceedings of SPIE the International Society for Optical Engineering, 2023
Comparison of SiNx-Based Surface Passivation Between Germanium and Silicon
Hanchen Liu, Toni P. Pasanen, Tsun Hang Fung, Joonas Isometsä, Oskari Leiviskä, Ville Vähänissi, Hele Savin
Physica Status Solidi A Applications and Materials Science, 2023
Millisecond-Level Minority Carrier Lifetime in Femtosecond Laser-Textured Black Silicon
Xiaolong Liu, Behrad Radfar, Kexun Chen, Elmeri Palikko, Toni P. Pasanen, Ville Vahanissi, Hele Savin
IEEE Photonics Technology Letters, 2022
Perspectives on Black Silicon in Semiconductor Manufacturing: Experimental Comparison of Plasma Etching, MACE, and Fs-Laser Etching
Xiaolong Liu, Behrad Radfar, Kexun Chen, Olli E. Setala, Toni P. Pasanen, Marko Yli-Koski, Hele Savin, Ville Vahanissi
IEEE Transactions on Semiconductor Manufacturing, 2022
Effects of post oxidation of SiO2/Si interfaces in ultrahigh vacuum below 450 °C
Zahra Jahanshah Rad, Juha-Pekka Lehtiö, Kexun Chen, Iris Mack, Ville Vähänissi, Mikko Miettinen, Marko Punkkinen, Risto Punkkinen, Petri Suomalainen, Hannu-Pekka Hedman, Mikhail Kuzmin, Jekaterina Kozlova, Mihkel Rähn, Aile Tamm, Hele Savin, Pekka Laukkanen, Kalevi Kokko
Vacuum, 2022
Electron Injection in Metal Assisted Chemical Etching as a Fundamental Mechanism for Electroless Electricity Generation
Shengyang Li, Kexun Chen, Ville Vähänissi, Ivan Radevici, Hele Savin, Jani Oksanen
Journal of Physical Chemistry Letters, 2022
Fast Wafer-Level Characterization of Silicon Photodetectors by Photoluminescence Imaging
Hussein M. Ayedh, Christopher W. Forbom, Juha Heinonen, Ismo T. S. Rauha, Marko Yli-Koski, Ville Vahanissi, Hele Savin
IEEE Transactions on Electron Devices, 2022
Effect of anode sheet resistance on rise time of black silicon induced junction photodiodes
Juha Heinonen, Antti Haarahiltunen, Ville Vähänissi, Toni P. Pasanen, Hele I. Savin, Mikko A. Juntunen
Proceedings of SPIE the International Society for Optical Engineering, 2022
Harnessing carrier multiplication in silicon solar cells using UV photons
Kexun Chen, Olli E. Setala, Behrad Radfar, Udo Kroth, Ville Vahanissi, Hele Savin
IEEE Photonics Technology Letters, 2021
Al-neal Degrades Al2O3 Passivation of Silicon Surface
Olli E. Setälä, Toni P. Pasanen, Jennifer Ott, Ville Vähänissi, Hele Savin
Physica Status Solidi A Applications and Materials Science, 2021
Grass-like alumina coated window harnesses the full omnidirectional potential of black silicon photodiodes
Christoffer Kauppinen, Toni P. Pasanen, Kirill Isakov, Michael Serué, Juha Heinonen, Ville Vähänissi, Harri Lipsanen, Hele Savin
Applied Optics, 2021
Achieving surface recombination velocity below 10 cm/s in n-type germanium using ALD Al2O3
Joonas Isometsä, Tsun Hang Fung, Toni P. Pasanen, Hanchen Liu, Marko Yli-koski, Ville Vähänissi, Hele Savin
APL Materials, 2021
Increased surface recombination in crystalline silicon under light soaking due to Cu contamination
Ismo T.S. Rauha, Anastasia H. Soeriyadi, Moonyong Kim, Marko Yli-Koski, Brendan Wright, Ville Vähänissi, Brett J. Hallam, Hele Savin
Solar Energy Materials and Solar Cells, 2021
Efficient photon capture on germanium surfaces using industrially feasible nanostructure formation
Kexun Chen, Joonas Isometsä, Toni P Pasanen, Ville Vähänissi, Hele Savin
Nanotechnology, 2021
Temperature dependency of responsivity and dark current of nearly ideal black silicon photodiodes
Juha Heinonen, Antti Haarahiltunen, Michael Serue, Daria Kriukova, Ville Vähänissi, Toni P. Pasanen, Hele Savin, Mikko A. Juntunen
Proceedings of SPIE the International Society for Optical Engineering, 2021
How Much Physics is in a Current-Voltage Curve? Inferring Defect Properties from Photovoltaic Device Measurements
Rachel C. Kurchin, Jeremy R. Poindexter, Ville Vahanissi, Hele Savin, Carlos del Canizo, Tonio Buonassisi
IEEE Journal of Photovoltaics, 2020
Decreasing Interface Defect Densities via Silicon Oxide Passivation at Temperatures Below 450 °C
Zahra Jahanshah Rad, Juha-Pekka Lehtiö, Iris Mack, Kawa Rosta, Kexun Chen, Ville Vähänissi, Marko Punkkinen, Risto Punkkinen, Hannu-Pekka Hedman, Andrei Pavlov, Mikhail Kuzmin, Hele Savin, Pekka Laukkanen, Kalevi Kokko
ACS Applied Materials Interfaces, 2020
Black-Silicon Ultraviolet Photodiodes Achieve External Quantum Efficiency above 130%
M. Garin, J. Heinonen, L. Werner, T. P. Pasanen, V. Vähänissi, A. Haarahiltunen, M. A. Juntunen, H. Savin
Physical Review Letters, 2020
Impact of doping and silicon substrate resistivity on the blistering of atomic-layer-deposited aluminium oxide
Jennifer Ott, Toni P. Pasanen, Akiko Gädda, Moisés Garín, Kawa Rosta, Ville Vähänissi, Hele Savin
Applied Surface Science, 2020
Improved emitter performance of RIE black silicon through the application of in-situ oxidation during POCl3 diffusion
Tsun Hang Fung, Toni P. Pasanen, Yu Zhang, Anastasia Soeriyadi, Ville Vähänissi, Giuseppe Scardera, David Payne, Hele Savin, Malcolm Abbott
Solar Energy Materials and Solar Cells, 2020
Black silicon boron emitter solar cells with EQE above 95% in UV
Kexun Chen, Ville Vahanissi, Zahra Jahanshah Rad, Juha-Pekka Lehtio, Pekka Laukkanen, Marko Yli-Koski, Hele Savin
Conference Record of the IEEE Photovoltaic Specialists Conference, 2020
Can hydrogenation mitigate Cu-induced bulk degradation in silicon?
Ismo T. S. Heikkinen, Brendan Wright, Anastasia H. Soeriyadi, Marko Yli-Koski, Moonyong Kim, Ville Vahanissi, Brett J. Hallam, Hele Savin
Conference Record of the IEEE Photovoltaic Specialists Conference, 2020
Nanostructured Germanium with >99% Absorption at 300–1600 nm Wavelengths
Toni P. Pasanen, Joonas Isometsä, Moises Garin, Kexun Chen, Ville Vähänissi, Hele Savin
Advanced Optical Materials, 2020
Modeling Field Effect in Black Silicon and Its Impact on Device Performance
Juha Heinonen, Toni P. Pasanen, Ville Vahanissi, Mikko A. Juntunen, Hele Savin
IEEE Transactions on Electron Devices, 2020
AlOx surface passivation of black silicon by spatial ALD: Stability under light soaking and damp heat exposure
Ismo T. S. Heikkinen, George Koutsourakis, Sauli Virtanen, Marko Yli-Koski, Sebastian Wood, Ville Vähänissi, Emma Salmi, Fernando A. Castro, Hele Savin
Journal of Vacuum Science and Technology A Vacuum Surfaces and Films, 2020
Black silicon back-contact module with wide light acceptance angle
Pablo Ortega, Moises Garín, Guillaume Gastrow, Tuukka Savisalo, Antti Tolvanen, Henri Vahlman, Ville Vähänissi, Toni P. Pasanen, David Carrió, Hele Savin, Ramón Alcubilla
Progress in Photovoltaics Research and Applications, 2020
High-sensitivity NIR photodiodes using black silicon
Juha Heinonen, Antti Haarahiltunen, Michael Dov Serue, Ville Vähänissi, Toni P. Pasanen, Hele I. Savin, Lutz Werner, Mikko A. Juntunen
Proceedings of SPIE the International Society for Optical Engineering, 2020
Impact of black silicon on light- and elevated temperature-induced degradation in industrial passivated emitter and rear cells
Toni P. Pasanen, Chiara Modanese, Ville Vähänissi, Hannu S. Laine, Franziska Wolny, Alexander Oehlke, Christian Kusterer, Ismo T.S. Heikkinen, Matthias Wagner, Hele Savin
Progress in Photovoltaics Research and Applications, 2019
Dissociation and Formation Kinetics of Iron–Boron Pairs in Silicon after Phosphorus Implantation Gettering
Nabil Khelifati, Hannu S. Laine, Ville Vähänissi, Hele Savin, Fatima Zohra Bouamama, Djoudi Bouhafs
Physica Status Solidi A Applications and Materials Science, 2019
Passivation of Detector-Grade Float Zone Silicon with Atomic Layer Deposited Aluminum Oxide
Jennifer Ott, Toni P. Pasanen, Päivikki Repo, Heli Seppänen, Ville Vähänissi, Hele Savin
Physica Status Solidi A Applications and Materials Science, 2019
Stability of the surface passivation properties of atomic layer deposited aluminum oxide in damp heat conditions
Ismo T. S. Heikkinen, George Koutsourakis, Sebastian Wood, Ville Vähänissi, Fernando A. Castro, Hele Savin
Aip Conference Proceedings, 2019
Cast Monocrystalline Silicon: New Alternative for Micro-and Nano-Electromechanical Systems?
Zhengjun Liu, Ville Vahanissi, Nikolai Chekurov, Ilkka Tittonen, Hele Savin
Journal of Microelectromechanical Systems, 2019
Effect of MACE Parameters on Electrical and Optical Properties of ALD Passivated Black Silicon
Kexun Chen, Toni P. Pasanen, Ville Vahanissi, Hele Savin
IEEE Journal of Photovoltaics, 2019
MACE nano-texture process applicable for both single- and multi-crystalline diamond-wire sawn Si solar cells
Kexun Chen, Jiawei Zha, Fenqin Hu, Xiaoya Ye, Shuai Zou, Ville Vähänissi, Joshua M. Pearce, Hele Savin, Xiaodong Su
Solar Energy Materials and Solar Cells, 2019
Compatibility of 3-D printed devices in cleanroom environments for semiconductor processing
T.P. Pasanen, G. von Gastrow, I.T.S. Heikkinen, V. Vähänissi, H. Savin, J.M. Pearce
Materials Science in Semiconductor Processing, 2019
Black silicon significantly enhances phosphorus diffusion gettering
Toni P. Pasanen, Hannu S. Laine, Ville Vähänissi, Jonas Schön, Hele Savin
Scientific Reports, 2018
Semiconductor parameter extraction via current-voltage characterization and Bayesian inference methods
Rachel C. Kurchin, Jeremy R. Poindexter, Daniil Kitchaev, Ville Vahanissi, Carlos del Canizo, Liu Zhe, Hannu S. Laine, Chris Roat, Sergiu Levcenco, Gerbrand Ceder, Tonio Buonassisi
2018 IEEE 7th World Conference on Photovoltaic Energy Conversion Wcpec 2018 A Joint Conference of 45th IEEE Pvsc 28th Pvsec and 34th Eu Pvsec, 2018
Rapid thermal anneal activates light induced degradation due to copper redistribution
N. Nampalli, H. S. Laine, J. Colwell, V. Vähänissi, A. Inglese, C. Modanese, H. Vahlman, M. Yli-Koski, H. Savin
Applied Physics Letters, 2018
Impact of Standard Cleaning on Electrical and Optical Properties of Phosphorus-Doped Black Silicon
Toni P. Pasanen, Hannu S. Laine, Ville Vahanissi, Kristian Salo, Sebastian Husein, Hele Savin
IEEE Journal of Photovoltaics, 2018
Cu gettering by phosphorus-doped emitters in p -type silicon: Effect on light-induced degradation
Alessandro Inglese, Hannu S. Laine, Ville Vähänissi, Hele Savin
Aip Advances, 2018
Elucidation of iron gettering mechanisms in boron-implanted silicon solar cells
Hannu S. Laine, Ville Vahanissi, Zhengjun Liu, Ernesto Magana, Jan Krugener, Ashley E. Morishige, Kristian Salo, Barry Lai, Hele Savin, David P. Fenning
IEEE Journal of Photovoltaics, 2018
Full recovery of red zone in p-type high-performance multicrystalline silicon
Ville Vähänissi, Hannu S. Laine, Zhengjun Liu, Marko Yli-Koski, Antti Haarahiltunen, Hele Savin
Solar Energy Materials and Solar Cells, 2017
Electronic Quality Improvement of Highly Defective Quasi-Mono Silicon Material by Phosphorus Diffusion Gettering
Zhengjun Liu, Ville Vähänissi, Hannu S. Laine, Morten Lindeberg, Marko Yli‐Koski, Hele Savin
Advanced Electronic Materials, 2017
Surface passivation of black silicon phosphorus emitters with atomic layer deposited SiO2/Al2O3 stacks
Toni Pasanen, Ville Vähänissi, Nicholas Theut, Hele Savin
Energy Procedia, 2017
Efficient surface passivation of black silicon using spatial atomic layer deposition
Ismo T.S. Heikkinen, Päivikki Repo, Ville Vähänissi, Toni Pasanen, Ville Malinen, Hele Savin
Energy Procedia, 2017
N-Type induced junction black silicon photodiode for UV detection
Mikko A. Juntunen, Juha Heinonen, Hannu S. Laine, Ville Vähänissi, Päivikki Repo, Anna Vaskuri, Hele Savin
Proceedings of SPIE the International Society for Optical Engineering, 2017
Black silicon n-Type photodiodes with high response over wide spectral range
Juha Heinonen, Mikko A. Juntunen, Hannu S. Laine, Ville Vähänissi, Päivikki Repo, Timo Dönsberg, Hele Savin
Proceedings of SPIE the International Society for Optical Engineering, 2017
Finite-vs. infinite-source emitters in silicon photovoltaics: Effect on transition metal gettering
Kirby Simon, Kyle Cepeda, Nishit Shetty, Elijah Thimsen
2017 IEEE 44th Photovoltaic Specialist Conference Pvsc 2017, 2017
Near-unity quantum efficiency of broadband black silicon photodiodes with an induced junction
Mikko A. Juntunen, Juha Heinonen, Ville Vähänissi, Päivikki Repo, Dileep Valluru, Hele Savin
Nature Photonics, 2016
Finite- vs. infinite-source emitters in silicon photovoltaics: Effect on transition metal gettering
Hannu S. Laine, Ville Vahanissi, Zhengjun Liu, Haibing Huang, Ernesto Magana, Ashley E. Morishige, Nabil Khelifati, Sebastian Husein, Barry Lai, Mariana Bertoni, Djoudi Bouhafs, Tonio Buonassisi, David P. Fenning, Hele Savin
Conference Record of the IEEE Photovoltaic Specialists Conference, 2016
Impact of Iron Precipitation on Phosphorus-Implanted Silicon Solar Cells
Hannu S. Laine, Ville Vahanissi, Ashley E. Morishige, Jasmin Hofstetter, Antti Haarahiltunen, Barry Lai, Hele Savin, David P. Fenning
IEEE Journal of Photovoltaics, 2016
Main defect reactions behind phosphorus diffusion gettering of iron
Jonas Schön, Ville Vähänissi, Antti Haarahiltunen, Martin C. Schubert, Wilhelm Warta, Hele Savin
Journal of Applied Physics, 2014
Iron precipitation upon gettering in phosphorus-implanted Czochralski silicon and its impact on solar cell performance
D. P. Fenning, V. Vahanissi, J. Hofstetter, A. E. Morishige, H. Laine, A. Haarahiltunen, S. Castellanos, M. Ann Jensen, B. Lai, H. Savin
2014 IEEE 40th Photovoltaic Specialist Conference Pvsc 2014, 2014
Gettering of iron in silicon solar cells with implanted emitters
Ville Vahanissi, Antti Haarahiltunen, Marko Yli-Koski, Hele Savin
IEEE Journal of Photovoltaics, 2014
Passivation of black silicon boron emitters with atomic layer deposited aluminum oxide
Päivikki Repo, Jan Benick, Guillaume von Gastrow, Ville Vähänissi, Friedemann D. Heinz, Jonas Schön, Martin C. Schubert, Hele Savin
Physica Status Solidi Rapid Research Letters, 2013
Impact of phosphorus gettering parameters and initial iron level on silicon solar cell properties
Ville Vähänissi, Antti Haarahiltunen, Heli Talvitie, Marko Yli‐Koski, Hele Savin
Progress in Photovoltaics Research and Applications, 2013
Significant minority carrier lifetime improvement in red edge zone in n-type multicrystalline silicon
Ville Vähänissi, Marko Yli-Koski, Antti Haarahiltunen, Heli Talvitie, Yameng Bao, Hele Savin
Solar Energy Materials and Solar Cells, 2013
N-type black silicon solar cells
Päivikki Repo, Jan Benick, Ville Vähänissi, Jonas Schön, Guillaume von Gastrow, Bernd Steinhauser, Martin C. Schubert, Martin Hermle, Hele Savin
Energy Procedia, 2013
Diffusion gettering of metal impurities in crystalline silicon
Hele Savin, Ville Vahanissi, Marko Yli-Koski, Heli Talvitie, Antti Haarahiltunen
Conference Record of the IEEE Photovoltaic Specialists Conference, 2012
Experimental study of iron redistribution between bulk defects and boron doped layer in silicon wafers
Heli Talvitie, Marko Yli‐Koski, Antti Haarahiltunen, Ville Vähänissi, Muhammad Imran Asghar, Hele Savin
Physica Status Solidi A Applications and Materials Science, 2011
Phosphorus and boron diffusion gettering of iron in monocrystalline silicon
H. Talvitie, V. Vähänissi, A. Haarahiltunen, M. Yli-Koski, H. Savin
Journal of Applied Physics, 2011
Gettering of iron in CZ-silicon by polysilicon layer
A. Haarahiltunen, M. Yli‐Koski, H. Talvitie, V. Vähänissi, J. Lindroos, H. Savin
Physica Status Solidi C Current Topics in Solid State Physics, 2011
Physical mechanisms of boron diffusion gettering of iron in silicon
V. Vähänissi, A. Haarahiltunen, H. Talvitie, M. Yli‐Koski, J. Lindroos, H. Savin
Physica Status Solidi Rapid Research Letters, 2010
Analysis of heterogeneous iron precipitation in multicrystalline silicon
Antti Haarahiltunen, Ville Vähänissi, Marko Yli-Koski, H. Talvitie, Hele Savin
Solid State Phenomena, 2009
Effect of oxygen in low temperature boron and phosphorus diffusion gettering of iron in Czochralski-grown silicon
Ville Vähänissi, Antti Haarahiltunen, H. Talvitie, M.I. Asghar, Marko Yli-Koski, Hele Savin
Solid State Phenomena, 2009