Onnistunut nanoteos antaa myös tutkijalle

Kirja-arvostelu: Richard A. L. Jones: Pehmeät koneet. Nanoteknologia ja elämä. Suomentanut Kimmo Pietiläinen, Terra Cognita 2008

Kansainvälinen kemian vuosi 2011 Suomessa

UNESCOn nimeämää kansainvälistä kemian vuotta vietettiin viime vuonna. Kansainvälisen kemian vuoden tavoitteena oli lisätä tietämystä kemian merkityksestä eri elämän aloilla ja innostaa erityisesti nuoria kemian ja luonnontieteiden pariin. Marie Curie sai kemian Nobelin palkinnon vuonna 1911, mikä oli yksi syy siihen, että vuosi 2011 valittiin kemian vuodeksi. Tämä antoi syyn juhlia vuoden aikana erityisesti naiskemistejä. Myös International Association of Chemical Societies vietti 100-vuotisjuhlaa vuonna 2011

Yleistajuisesti uusista materiaaleista

Philip Ball: Mittojen mukaan, 2000-luvun materiaalit. Suomentanut Kimmo Pietiläinen Terra Cognita Oy 1998

Self-Aligned Thin-Film Patterning by Area-Selective Etching of Polymers

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 patterning: area-selective gas-phase etching of polymers. The etching reactions are selective to the materials underneath the polymers. Either O2 or H2 can be used as an etchant gas. After diffusing through the polymer film to the catalytic surfaces, the etchant gas molecules are dissociated into their respective atoms, which then readily react with the polymer, etching it away. On noncatalytic surfaces, the polymer film remains. For example, polyimide and poly(methyl methacrylate) (PMMA) were selectively oxidatively removed at 300 °C from Pt and Ru, while on SiO2 they stayed. CeO2 also showed a clear catalytic effect for the oxidative removal of PMMA. In H2, the most active surfaces catalysing the hydrogenolysis of PMMA were Cu and Ti. The area-selective etching of polyimide from Pt was followed by area-selective atomic layer deposition of iridium using the patterned polymer as a growth-inhibiting layer on SiO2, eventually resulting in dual side-by-side self-aligned formation of metal-on-metal and insulator (polymer)-on-insulator. This demonstrates that when innovatively combined with area-selective thin film deposition and, for example, lift-off patterning processes, self-aligned etching processes will open entirely new possibilities for the fabrication of the most advanced and challenging semiconductor devices

Metal Fluorides as Lithium-Ion Battery Materials: An Atomic Layer Deposition Perspective

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 cathode and solid electrolyte materials for future batteries. To be applicable in thin film batteries, metal fluorides should be deposited with a method providing a high level of control over uniformity and conformality on various substrate materials and geometries. Atomic layer deposition (ALD), a method widely used in microelectronics, offers unrivalled film uniformity and conformality, in conjunction with strict control of film composition. In this review, the basics of lithium-ion batteries are shortly introduced, followed by a discussion of metal fluorides as potential lithium-ion battery materials. The basics of ALD are then covered, followed by a review of some conventional lithium-ion battery materials that have been deposited by ALD. Finally, metal fluoride ALD processes reported in the literature are comprehensively reviewed. It is clear that more research on the ALD of fluorides is needed, especially transition metal fluorides, to expand the number of potential battery materials available.Peer reviewe

Area-Selective Molecular Layer Deposition of Polyimide on Cu through Cu-Catalyzed Formation of a Crystalline Interchain Polyimide

Novel area-selective molecular layer deposition (AS-MLD) of polyimide (PI) on Cu versus native SiO2 was studied. By use of 1,6-diaminohexane (DAH) and pyromellitic dianhydride (PMDA) as precursors, PI films can be selectively deposited on the Cu surface at 200-210 degrees C with a rate around 7.8 A/cycle while negligible growth takes place on SiO2. The selectivity was successfully demonstrated also on Cu/SiO2 patterns at 200 degrees C; after 180 MLD cycles, around 140 nm thick PI was deposited on Cu regions whilePeer reviewe

Use of 1,1-Dimethylhydrazine in the Atomic Layer Deposition of Transition Metal Nitride Thin Films

Transition metal nitride thin films are important in many areas of microelectronics. The most important challenge today is the adoption of copper interconnects in the integrated circuits, which requires the use of a diffusion barrier because copper is known to diffuse through silicon dioxide-based dielectrics. The most promising diffusion barrier materials are transition metals, metal nitrides, metal silicides, and metal-silicon-nitrides. Because for a long time the semiconductor industry has used Ta-, Ti-, and W-based materials, these transition metals and their compounds are also the most studied materials for barrier applications. The deposition of nitride thin films has mainly been performed with various physical vapor deposition (PVD) and chemical vapor deposition (CVD) techniques. These, however, suffer from various difficulties. Films can be grown at quite low temperatures using the PVD techniques, but their step coverage is poor and therefore their use in manufacturing the future generation integrated circuits is limited. More conformal films are achieved by using the CVD techniques, but unfortunately the needed growth temperatures are often too high. In addition good conformality and good electric properties are often difficult to achieve at the same time. In the traditional CVD deposition processes, titanium nitride (TiN) films are deposited from TiCl 4 , H 2 , and N 2 at temperatures above 750ЊC. 2 If NH 3 is used instead of H 2 and N 2 , high conductivity films with low chlorine contamination levels can usually be deposited at temperatures exceeding 550ЊC. 3-9 Nowadays alternative precursors, particularly alkyl amides, 10-15 additional energy sources, 16 and post-or intermediate deposition plasma treatments Atomic layer deposition (ALD), also known as atomic layer epitaxy (ALE), TiN, 25-28 TaN, 27,29 NbN, 27,30 MoN, 27 WN, 31 and Ti-Si-N 32 films have already been deposited by the ALD method. Except for Ti-Si-N and one TiN process, where alkyl amines were used, 28 halides have been used as the metal source and ammonia as the nitrogen source. An intermediate zinc pulse between the chloride and ammonia pulses has been proven to be effective in improving the electrical properties of the TiN, The oxidation number of the metal in the conventional precursors is higher than in the desired nitride and therefore reduction is required. At the present time ammonia has been the most often used and studied nitrogen source in ALD. However, NH 3 is quite stable and not a very effective reducing agent and therefore, alternative more reactive nitrogen sources should be sought. One of the possible choices is hydrazine, N 2 H 4 , which is more reactive than NH 3 . The radical formation enthalpie

Controlling Atomic Layer Deposition of 2D Semiconductor SnS(2)by the Choice of Substrate

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) process is used to synthesize up to 5x5 cm(2)continuous, few-layer SnS(2)films on a variety of substrates, including SiO2/Si, Si-H, different ALD-grown films (Al2O3, TiO2, and Ir), sapphire, and muscovite mica. As a part of comprehensive film characterization, the use of low energy ion scattering (LEIS) is showcased to determine film continuity, coverage of monolayer and multilayer areas, and film thickness. It is found that on sapphire substrate, continuous films are achieved at lower thicknesses compared to the other substrates, down to two monolayers or even less. On muscovite mica, van der Waals epitaxial growth is realized after the post-deposition annealing, or even in the as-deposited films when the growth is performed at 175 to 200 degrees C. This work highlights the importance of the substrate choice for 2D materials and presents a practical low-temperature method for the deposition of high-quality SnS(2)films that may be further evaluated for a range of applications.Peer reviewe

Coating and functionalization of high density ion track structures by atomic layer deposition

In this study flexible TiO 2 coated porous Kapton membranes are presented having electron multiplication properties. 800 nm crossing pores were fabricated into 50 m thick Kapton membranes using ion track technology and chemical etching. Consecutively, 50 nm TiO 2 films were deposited i nto the pores of the Kapton membranes by atomic layer deposition using Ti( i OPr) 4 and water as precursors at 250 °C. The TiO 2 films and coated membranes were studied by scanning electro n microscopy (SEM), X - ray diffraction (XRD) and X - ray reflectometry (XRR). Au metal electrod e fabrication onto both sides of the coated foils was achieved by electron beam evaporation. The electron multipliers were obtained by joining 3 two coated membranes separated by a conductive spacer. The results show that electron multiplication can be achie ved using ALD - coated flexible ion track polymer foils