Markku Leskelä

Markku Leskelä
University of Helsinki | HY · Department of Chemistry

About

927
Publications
173,553
Reads
How we measure 'reads'
A 'read' is counted each time someone views a publication summary (such as the title, abstract, and list of authors), clicks on a figure, or views or downloads the full-text. Learn more
38,072
Citations

Publications

Publications (927)
Article
In this paper, we present an ALD process for ScF3 using Sc(thd)3 and NH4F as precursors. This is the first material made by ALD that has a negative thermal expansion over a wide-temperature range. Crystalline films were obtained at the deposition temperatures of 250–375 °C, with a growth per cycle (GPC) increasing along the deposition temperature f...
Article
Full-text available
Molecular layer deposition (MLD) offers molecular level control in deposition of organic and hybrid thin films. This article describes a new type of inorganic–organic silicon-based MLD process where Aluminium chloride (AlCl3) and 1,4-bis(triethoxysilyl)benzene (BTEB) were used as precursors. Hybrid films were deposited at a temperature range of 300...
Article
Full-text available
The present study describes atomic layer deposition (ALD) processes and characterization of CoF2, NiF2, and HoF3 thin films. For CoF2 deposition CoCl2(TMEDA) (TMEDA = N,N,N',N'-tetramethylethylenediamine) and NH4F were used as precursors. CoF2 deposition was studied at 180-275 °C, resulting in a growth per cycle (GPC) of 0.7 to 1.2 Å. All the films...
Article
Full-text available
Atomic layer deposition processes with inherent substrate selectivity are more straightforward for area-selective atomic layer deposition (AS-ALD) than approaches using surface passivation or activation with self-assembled monolayers (SAMs), small molecule inhibitors (SMIs) or seed layers. Here, ALD of ZnS using elemental zinc and sulfur as precurs...
Article
Full-text available
Abstract This paper presents preparation of boron‐doped Al2O3 thin films by atomic layer deposition (ALD) using phenylboronic acid (PBA) and trimethylaluminum (TMA) as precursors. Deposition temperatures of 160–300 °C are studied, giving a maximum growth per cycle (GPC) of 0.77 Å at 200 °C. Field emission scanning electron microscopy (FESEM) and at...
Article
Full-text available
In this paper, the deposition of pyrrone thin film materials by molecular layer deposition (MLD) is reported for the first time using pyromellitic dianhydride (PMDA) and 3,3'‐diaminobenzidine (DAB) as monomers, and ozone as a promoting precursor. Besides ozone, the effect of water, hydrogen peroxide, and oxygen is also tested to promote the growth...
Article
Full-text available
Copper iodide (CuI) is a high‐performance p‐type transparent semiconductor that can be used in numerous applications, such as transistors, diodes, and solar cells. However, the lack of conformal and scalable methods to deposit CuI thin films limits its establishment in applications that involve complex‐shaped and/or large substrate areas. In this w...
Article
Full-text available
Atomic layer deposition offers outstanding film uniformity and conformality on substrates with high aspect ratio features. These qualities are essential for mixed-halide perovskite films applied in tandem solar cells, transistors and light-emitting diodes. The optical and electronic properties of mixed-halide perovskites can be adjusted by adjustin...
Article
Full-text available
Selective deposition of hybrid and inorganic materials inside nanostructures could enable major nanotechnological advances. However, inserting ready-made composites inside nanocavities may be difficult, and therefore, stepwise approaches are needed. In this paper, a poly(ethyl acrylate) template is grown selectively inside cavities via condensation...
Article
First isolated from the tropical plant Oschrosia elliptica, indole alkaloid ellipticine provoked huge interest since it demonstrated antitumor activity was demonstrated along with limited toxic side effects and a complete lack of hematological toxicity. In this work, a five-step Cranwell and Saxton synthesis was used for obtaining ellipticine (Ell)...
Article
Full-text available
The deposition of polybenzimidazole (PBI)‐like thin films by molecular layer deposition is reported here for the first time using isophthalic acid (IPA) and 3,3′‐diaminobenzidine (DAB) as monomers and trimethylaluminum (TMA) as a linker precursor. Two precursor pulsing sequences are tested, the ABCB (TMA + IPA + DAB + IPA) and ABC (TMA + IPA + DAB)...
Article
Gadolinium fluoride is an attractive optical material with applications in, e.g., deep-UV lithography, solar cells, and medical imaging. Despite the interest toward this material, no atomic layer deposition (ALD) process has been published. In this article, an ALD process for GdF3 using Gd(thd)3 and NH4F as precursors is presented. The deposition w...
Article
Full-text available
Co9S8 is an interesting sulfide material with metallic conductivity that has shown promise for various energy applications. Herein, we report a new atomic layer deposition process producing crystalline, pure, and highly conductive Co9S8 thin films using CoCl2(TMEDA) (TMEDA = N,N,N',N'-tetramethylethylenediamine) and H2S as precursors at 180-300 °C....
Article
Full-text available
Patterning of thin films with lithography techniques for making semiconductor devices has been facing increasing difficulties with feature sizes shrinking to the sub-10 nm range, and alternatives have been actively sought from area-selective thin film deposition processes. Here, an entirely new method is introduced to self-aligned thin-film pattern...
Article
Full-text available
Because of its high conductivity and intrinsic stability, poly(3,4-ethylenedioxythiophene (PEDOT) has gained great attention both in academic research and industry over the years. In this study, we used the oxidative molecular layer deposition (oMLD) technique to deposit PEDOT from 3,4-ethylenedioxythiophene (EDOT) and a new inorganic oxidizing age...
Article
Since two decades ago, research on resistive memories has continuosly grown, gathering relevance through the variety of different technologies that fit into the non-volatile memories’ area. In this study, we discuss the performance and electrical characteristics of RRAM cells constituted by MIM stacks with dielectric formed by Nb2O5-doped SiO2. We...
Article
Full-text available
This article describes the deposition of AlF3/polyimide nanolaminate film by inorganic-organic atomic layer deposition (ALD) at 170 °C. AlCl3 and TiF4 were used as precursors for AlF3. Polyimide layers were deposited from PMDA (pyromellitic dianhydride, 1,2,3,5-benzenetetracarboxylic anhydride) and DAH (1,6-diaminohexane). With field-emission scann...
Article
Lanthanide fluoride thin films have gained interest as materials for various optical applications, including electroluminescent displays and mid-IR lasers. However, the number of atomic layer deposition (ALD) processes for lanthanide fluorides has remained low. In this work, we present an ALD process for TbF3 using tris(2,2,6,6-tetramethyl-3,5-hept...
Article
Full-text available
2D transition metal dichalcogenides (TMDCs) are among the most exciting materials of today. Their layered crystal structures result in unique and useful electronic, optical, catalytic, and quantum properties. To realize the technological potential of TMDCs, methods depositing uniform films of controlled thickness at low temperatures in a highly con...
Article
High-performance p-type oxide thin film transistors (TFTs) have great potential for many semiconductor applications. However, these devices typically suffer from low hole mobility and high off-state currents. We fabricated p-type TFTs with a phase-pure polycrystalline Cu2O semiconductor channel grown by atomic layer deposition (ALD). The TFT switch...
Article
Full-text available
Atomic layer deposition (ALD) is a viable method for depositing functional, passivating, and encapsulating layers on top of halide perovskites. Studies in that area have only focused on metal oxides, despite a great number of materials that can be made with ALD. This work demonstrates that, in addition to oxides, other ALD processes can be compatib...
Article
Full-text available
Semiconducting 2D materials, such as SnS2, hold great promise in a variety of applications including electronics, optoelectronics, and catalysis. However, their use is hindered by the scarcity of deposition methods offering necessary levels of thickness control and large‐area uniformity. Herein, a low‐temperature atomic layer deposition (ALD) proce...
Article
SiO2-Fe2O3 mixture films and nanolaminates were grown by atomic layer deposition from iron trichloride, hexakis(ethylamino)disilane, and ozone at 300 °C. Orthorhombic ɛ-Fe2O3 was identified in Fe2O3 reference films and in Fe2O3 layers grown to certain thicknesses between amorphous SiO2 layers. SiO2-Fe2O3 films could be magnetized in external fields...
Article
Full-text available
Novel area-selective molecular layer deposition (AS-MLD) of polyimide (PI) on Cu versus native SiO2 was studied. By using 1,6-diaminohexane (DAH) and pyromellitic dianhydride (PMDA) as precursors, PI films can be selectively deposited on Cu surface at 200-210 oC with a rate around 7.8 Å/cycle while negligible growth takes place on SiO2. The selecti...
Article
A new method to characterize the properties of leaky ferroelectric films is proposed. Double swing quiescent-current technique allows to obtain coercive field and remanent polarization in those cases in which high leakage, trap generation current and displacement current mask the ferroelectric terms themselves. Double swing quiescent-current techni...
Conference Paper
Ferroelectric materials are very attractive for many technological applications. In the scenario of conventional CMOS technology, they are very suitable to fabricate nonvolatile memories (FeRAM) or as the gate stack of a transistor to realize a FeFET. Conventional ferroelectric materials, like PZT or SBT, exhibit very high permittivity and low coer...
Article
Full-text available
IrO2 is an important material in numerous applications ranging from catalysis to the microelectronics industry, but despite this its behaviour upon annealing under different conditions has not yet been thoroughly studied. This work provides a detailed investigation of the annealing of IrO2 thin films using in situ high-temperature X-ray diffraction...
Article
Full-text available
Amorphous SiO2-Nb2O5 nanolaminates and mixture films were grown by atomic layer deposition. The films were grown at 300 oC from Nb(OC2H5)5, Si2(NHC2H5)6, and O3 to thicknesses ranging from 13 to 130 nm. The niobium to silicon atomic ratio was varied in the range of 0.11-7.20. After optimizing the composition, resistive switching properties could be...
Article
Full-text available
Anopheles darlingi is the main vector of malaria in Brazil, characterized by a high level of anthropophilia and endophagy. Imidacloprid, thiacloprid, and acetamiprid are the most widespread insecticides of the neonicotinoid group. However, they produce adverse effects on the non-target insects. Flupyradifurone has been marketed as an alternative to...
Article
Full-text available
TiO2 and ZnO single and multilayers were deposited on hydroxyl functionalized multi-walled carbon nanotubes using atomic layer deposition. The bare carbon nanotubes and the resulting heterostructures were characterized by TG/DTA, Raman, XRD, SEM-EDX, XPS, TEM-EELS-SAED and low temperature nitrogen adsorption techniques, and their photocatalytic and...
Article
In this study, the authors investigated third-order optical nonlinearity in polyimide/Ta2O5 nanolaminates deposited by atomic layer deposition. Third harmonic signal measurements were done with a multiphoton microscope at an excitation wavelength of 1.55 μm, laser pulse duration of 150 fs, and estimated pulse energy of 1.2 nJ. Third-order optical n...
Article
Full-text available
Van der Waals epitaxy holds great promise in producing high-quality films of 2D materials. However, scalable van der Waals epitaxy processes operating at low temperatures and low vacuum conditions are lacking. Herein, atomic layer deposition is used for van der Waals epitaxy of continuous multilayer films of 2D materials HfS2, MoS2, SnS2, and ZrS2...
Article
Synthetic procedures, including doping, sintering and surface coating, can noticeably affect the physicochemical properties of semiconductors. Introduced changes very often translate into photocatalytic and photoelectrochemical activity alterations. However, in this work we have focused on more subtle treatments, which result in lack of changes obs...
Article
Full-text available
Semiconducting two-dimensional (2D) materials are studied intensively because of their promising performance in diverse applications from electronics to energy storage and catalysis. Recently, HfS2 and ZrS2 have emerged as potential rivals for the commonly studied 2D semiconductors such as MoS2 and WSe2, but their use is hindered by the difficulty...
Article
Full-text available
Herein, we report an atomic layer deposition (ALD) process for Cu2O thin films using copper(II) acetate [Cu(OAc)2] and water vapor as precursors. This precursor combination enables the deposition of phase-pure, polycrystalline, and impurity-free Cu2O thin films at temperatures of 180–220 °C. The deposition of Cu(I) oxide films from a Cu(II) precurs...
Article
Full-text available
This work presents preparation of nickel germanide (Ni2Ge) thin films by atomic layer deposition (ALD). The films were grown using NiCl2(tmpda) (tmpda = N,N,N’,N’,-tetramethyl-1,3-propanediamine) and tributylgermanium hydride (TBGH) serving as a new, efficient reducing agent. This is the first time ALD NixGey films are prepared directly upon the co...
Poster
Full-text available
This poster presents capillary condensation assisted vapor deposition method. It is a flexible and efficient way to form selectively superconformal coatings, i.e. to fill nanopores and other cavities without coating open and flat surfaces.
Article
Full-text available
Optoelectronic materials can source, detect, and control light wavelengths ranging from gamma and x rays to ultraviolet, visible, and infrared regions. Optoelectronic devices are usually systems that transduce electricity to optical signal or vice versa. Optoelectronic devices include many modern necessities such as lamps, displays, lasers, solar c...
Article
This article describes the atomic layer deposition (ALD) of nickel nitride and nickel thin films using a diamine adduct of Ni(II) chloride, NiCl2(TMPDA) (TMPDA = N,N,N′,N′,‐tetramethyl‐1,3‐propanediamine), as the metal precursor. Owing to the high reducing power of tert‐butylhydrazine (TBH), the films are grown at low temperatures of 190–250 °C. Th...
Data
Full article is open access and available at https://pubs.rsc.org/en/Content/ArticleLanding/2019/MH/c8mh01523f#!divAbstract . This is Electronic Supplementary Information for the article
Article
Full-text available
Modern technology is heavily dependent on a family of vapor deposition methods where thin coatings are formed by introducing gaseous reagents on solid substrates. However, a major drawback in the methods is the difficulty in miniaturizing them to complex nanoscaled structures. Based on capillary condensation, the Curvature/Capillary Selective Vapor...
Article
The authors demonstrate multilayer epitaxial films by atomic layer deposition and postdeposition annealing. Their example features two ABO3 type perovskite oxide films with different materials properties - a conductor (LaNiO3) and an insulator (SrTiO3) - that can be integrated epitaxially once the geometric interaction between the two oxides' latti...
Article
Three heteroleptic Zr precursors were studied for atomic layer deposition (ALD) of ZrO2. Films were deposited from Zr(Cp)(tBuDAD)(OⁱPr), Zr(MeCp)(TMEA), and Zr(Me5Cp)(TEA) with either water or ozone as the oxygen source {tBuDAD = N,N-bis(tertbutyl)ethene-1,2-diaminato, TMEA = tris[2-(methylamino)ethyl]aminate, TEA = triethoanolaminate}. Self-limiti...
Article
Tungsten disulfide (WS 2 ) is a semiconducting 2D material, which is gaining increasing attention in the wake of graphene and MoS 2 owing to its exciting properties and promising performance in a multitude of applications. Herein, the authors deposited WS x thin films by atomic layer deposition using W 2 (NMe 2 ) 6 and H 2 S as precursors. The film...
Article
In this paper, results on the solid state reactions of atomic layer deposited Li 2 CO 3 with HfO 2 and ZrO 2 are reported. An Li 2 CO 3 film was deposited on top of hafnia and zirconia, and the stacks were annealed at various temperatures in air to remove the carbonate and facilitate lithium diffusion into the oxides. It was found that Li ⁺ ions ar...
Article
Full-text available
Titanium dioxide nanotubes/hydroxyapatite nanocomposites were produced on a titanium alloy (Ti6Al4V/TNT/HA) and studied as a biocompatible coating for an implant surface modification. As a novel approach for this type of nanocomposite fabrication, the atomic layer deposition (ALD) method with an extremely low number of cycles was used to enrich tit...
Article
Atomic layer deposition (ALD) enables deposition of numerous materials in thin film form, yet there are no ALD processes for metal iodides. Herein, we demonstrate an ALD process for PbI2, a metal iodide with 2D structure that has applications in areas such as photodetection and photovoltaics. The process uses a lead silylamide Pb(btsa)2 and SnI4 as...
Article
Full-text available
We employ atomic layer deposition to prepare 50 nm thick hematite photoanodes followed by passivating them with a 0.5 nm thick Ta2O5-overlayer and compare them with samples uniformly doped with the same amount of tantalum. We observe a three-fold improvement in photocurrent with the same onset voltage using Ta-overlayer hematite photoanodes, while...
Article
In this work, we have studied the applicability of Co(BTSA)2(THF) [BTSA = bis(trimethylsilyl)amido] (THF = tetrahydrofuran) in atomic layer deposition (ALD) of cobalt oxide thin films. When adducted with THF, the resulting Co(BTSA)2(THF) showed good volatility and could be evaporated at 55 °C, which enabled film deposition in the temperature range...
Article
Heteroleptic bis(tert-butylimido)bis(N,N’-diisopropylacetamidinato) compounds of molybdenum and tungsten are introduced as precursors for atomic layer deposition (ALD) of tungsten and molybdenum oxide thin films using ozone as the oxygen source. Both precursors have similar thermal properties, but exhibit different growth behavior. With the molybde...
Article
Full-text available
Intermetallics form a versatile group of materials that possess unique properties ranging from superconductivity to giant magnetoresistance. The intermetallic Co–Sn and Ni–Sn compounds are promising materials for magnetic applications as well as for anodes in lithium‐ and sodium‐ion batteries. Herein, a method is presented for the preparation of Co...
Article
Full-text available
Nanocrystalline HfO2:Al2O3 mixture films and nanolaminates were grown by atomic layer deposition at 350◦C from metal chloride precursors and water. Formation of metastable HfO2 polymorphs versus monoclinic phase was affected by the relative amount and thickness of constituent oxide layers. The films exhibited saturative magnetization and charge pol...
Article
Full-text available
Molybdenum forms a range of oxides with different stoichiometries and crystal structures, which lead to different properties and performance in diverse applications. Herein, crystalline molybdenum oxide thin films with controlled phase composition are deposited by atomic layer deposition. The MoO2(thd)2 and O3 as precursors enable well-controlled g...
Article
Full-text available
Lithium-ion batteries are the enabling technology for a variety of modern day devices, including cell phones, laptops and electric vehicles. To answer the energy and voltage demands of future applications, further materials engineering of the battery components is necessary. To that end, metal fluorides could provide interesting new conversion cath...
Article
Iron and titanium oxides have attracted substantial attention in photoelectrochemical water splitting applications. However, both materials suffer from intrinsic limitations that constrain the final device performance. In order to overcome the limitations of the two materials alone, their combination has been proposed as a solution to the problems....
Article
Rhenium is both a refractory metal and a noble metal that has attractive properties for various applications. Still, synthesis and applications of rhenium thin films have been limited. We introduce here the growth of both rhenium metal and rhenium nitride thin films by the technologically important atomic layer deposition (ALD) method over a wide d...
Article
Rhenium is both a refractory metal and a noble metal that has attractive properties for various applications. Still, synthesis and applications of rhenium thin films have been limited. We introduce here the growth of both rhenium metal and rhenium nitride thin films by the technologically important atomic layer deposition (ALD) method over a wide d...
Article
La2O3 thin films were deposited by atomic layer deposition from a liquid heteroleptic La precursor, La(ⁱPrCp)2(ⁱPr-amd), with either water, ozone, ethanol, or both water and ozone (separated by a purge) as the oxygen source. The effect of the oxygen source on the film growth rate and properties such as crystallinity and impurities was studied. Satu...
Article
Full-text available
Thin mixed and nanolaminate films of ZrO2 and Al2O3 were grown by atomic layer deposition from the corresponding metal chlorides and water. The films were grown at 350◦C in order to ensure ZrO2 crystallization in the as-deposited state. The relative thicknesses of layers in the structure of the nanolaminates were controlled in order to maximize the...
Article
In this paper, we introduce a new Co precursor for the atomic layer deposition (ALD) of Co metal and other Co containing materials. CoCl2(TMEDA) (TMEDA = N,N,N',N'-tetramethylethylenediamine) is a diamine adduct of cobalt(II) chloride that is inexpensive and easy to synthesize making it an industrially viable precursor. Furthermore, CoCl2(TMEDA) sh...
Article
Semiconducting 2D materials, such as SnS2, hold immense potential for many applications ranging from electronics to catalysis. However, deposition of few‐layer SnS2 films has remained a great challenge. Herein, continuous wafer‐scale 2D SnS2 films with accurately controlled thickness (2 to 10 monolayers) are realized by combining a new atomic layer...
Article
Nowadays both the volatile and non-volatile memories are under a high development pressure in the current industrial context. Besides the dominant solid-state memory technologies, such as DRAM and FLASH, non-volatile resistive memories (RRAM) are considered adequate candidates to complement the memory landscape [1, 2]. In spite of the interest, no...
Article
Space technology has been an early adopter of additive manufacturing (AM) as a way of quickly producing relatively complex systems and components that would otherwise require expensive and custom design and production. Space as an environment and long-term survivability pose challenges to materials used in AM and these challenges need to be address...
Article
Full-text available
We demonstrate the preparation and exploitation of multilayer metal oxide hard masks for lithography and 3D nanofabrication. Atomic layer deposition (ALD) and focused ion beam (FIB) technologies are applied for mask deposition and mask patterning, respectively. A combination of ALD and FIB was used and a patterning procedure was developed to avoid...
Article
2D materials research is advancing rapidly as various new “beyond graphene” materials are fabricated, their properties studied, and materials tested in various applications. Rhenium disulfide is one of the 2D transition metal dichalcogenides that has recently shown to possess extraordinary properties such as that it is not limited by the strict mon...
Article
Full-text available
ZrO2 thin films were grown by atomic layer deposition using alternate surface reactions of ZrI4 and O3 precursors in the temperature range of 250–400°C to the thickness in the range of 5–100 nm. The films were dense, continuous, and consisted of mixed monoclinic and metastable polymorphs with significant contribution from cubic ZrO2. The ZrO2 films...