A nanostructured three-dimensional (3D) microbattery has been produced and cycled in a Li-ion battery. It consists of a current collector of aluminum nanorods, a uniform layer of 17 nm TiO(2) covering the nanorods made using ALD, an electrolyte and metallic lithium counter electrode. The battery is electrochemically cycled more than 50 times. The increase in total capacity is 10 times when using a 3D architecture compared to a 2D system for the same footprint area.

Double- and triple-walled TiO2/iron oxide nanotubes with well defined interfaces have been produced in nanoporous alumina templates using atomic layer deposition method. The structural properties of each individual layer are found to be dependent on the deposition temperatures. The outer layers of TiO2 are polycrystalline and consist of a phase mixture of anatase and rutile, while the inner TiO2 layers grown at lower temperature are amorphous. The iron oxide layers consist of pure hematite when deposited at 500 °C, while a phase mixture of hematite and magnetite was obtained at 400 °C. The magnetization measurements reveal that the studied nanotubes exhibit weak ferromagnetic behavior and magnetic anisotropy with an easy axis perpendicular to the tube axis.

Thin films of cobalt oxide, iron oxide and niobium oxide, and nanostructured thin films of iron oxide, titanium oxide and multilayered iron oxide/titanium oxide have been deposited by Atomic Layer Deposition (ALD). The metal oxides were grown using the precursor combinations CoI2/O2, Fe(Cp)2/O2, NbI5/O2 and TiI4/H2O. The samples were analysed primarily with respect to phase content, morphology and growth characteristics.Thin films deposited on Si (100) were found to be amorphous or polycrystalline, depending on deposition temperature and the oxide deposited; cobalt oxide was also deposited on MgO (100), where it was found to grow epitaxially with orientation (001)[100]Co3O4||(001)[100]MgO. As expected, the polycrystalline films were rougher than the amorphous or the epitaxial films. The deposition processes showed properties characteristic of self-limiting ALD growth; all processes were found to have a deposition temperature independent growth region. The deposited films contained zero or only small amounts of precursor residues.The nanostructured films were grown using anodic aluminium oxide (AAO) or carbon nanosheets as templates. Nanotubes could be manufactured by depositing a thin film which covers the pore walls of the AAO template uniformly; free-standing nanotubes retaining the structure of the template could be fabricated by removing the template. Multilayered nanotubes could be obtained by depositing multiple layers of titanium dioxide and iron oxide in the pores of the AAO template. Carbon nanosheets were used to make titanium dioxide nanosheets with a conducting graphite backbone. The nucleation of the deposited titanium dioxide could be controlled by acid treatment of the carbon nanosheets.

Thin films and nanotubes of iron oxide are deposited using atomic layer deposition (ALD) on Si(100) and anodic aluminum oxide (AAO), respectively. Ferrocene, Fe(Cp)(2), and oxygen are used as precursors. Successful depositions are carried out in the temperature range 350-500 degrees C on Si(100), while all depositions on AAO are made at 400 degrees C. The growth per cycle values are around 0.14 nm on Si(100) in the temperature range 350-500 degrees C and 0.06 nm on AAO. Below 500 degrees C, the iron oxide crystallizes as a phase mixture on both types of substrates. One of the phases is identified as the rhombohedral Fe2O3 phase (hematite), but the second phase cannot be unambiguously identified. Above 500 degrees C, only phase pure hematite is detected. For deposition of nanotubes, in-house made AAO membranes are used, having an aspect ratio of 30. By etching of the AAO membranes after deposition, free-standing nanotubes retaining the order of the AAO template can be fabricated.

Nanostructured films of anatase TiO2 is deposited on carbon nanosheet (CNS) templates using atomic layer deposition (ALD). The high-surface area of the CNS together with the unique step coverage of the ALD process makes it possible to obtain sheet-like TiO2 nanostructures, for use in potential applications, e.g. photocatalysis and photovoltaics. A problem with ALD on CNS was the low nucleation rate giving TiO2 films with pinholes. It is shown that introduction of defects by an acid-treatment process can be used to control initial nucleation and growth of the films. The TiO2 on the defect-rich CNS nucleates faster and results in a film with no observable pinholes consisting of crystalline grains in an amorphous matrix.

The vast development of surface micromachining technology has brought the proliferation of MEMS devices. However, the issue of powering the MEMS devices still remains as a great challenge. Although the conventional thin film 2D batteries seems promising for achieving high power density, however, relatively large area is required for having sufficient capacity. The drawbacks of 2D batteries can be overcome by using 3D architecture of Li-ion microbatteries.The 3D architecture of Li-ion microbatteries will have the advantages of short diffusion path as the electrode active materials are just tenth of nanometer deposited on the current collectors. The short diffusion path guarantees the high power performance. Besides that, the capacity of the microbatteries can be enhanced by just increasing the length of the electrode while keeping the areal footprint. This is what makes the 3D microbatteries a more promising power supply for MEMS.Our approach to synthesize a 3D Li-ion microbattery is starting with the synthesis of a nanostructure current collector using a template method. An anodized aluminium oxide (AAO) membrane is used as template for the electrodeposition of an aluminium current collector. AAO with defined pore sizes and inter-pores spacing are synthesized with a suitable diameter and interspacing where an aluminium current collector can grow within the template. The following step is the deposition of electrode active materials on the current collector. In this example Atomic Layer Deposition (ALD) is employed in order to achieve a well deposited layer of, in this case, a TiO2 cathode material. By controlling the deposition parameters, the crystal structure and the thickness of TiO2 layer can be altered to give a better electrochemical performance. Our results will be discussed in the light of the complexity of the deposition mechanisms of both the aluminium current collector nano-rods and the TiO2 layer.

An electrical characterization of Al2O3 based metal-insulator-semiconductor structures has been carried out by using capacitance-voltage, deep level transient spectroscopy, and conductance-transient (G-t) techniques. Dielectric films were atomic layer deposited (ALD) at temperatures ranging from 300 to 800 °C directly on silicon substrates and on an Al2O3 buffer layer that was grown in the same process by using 15 ALD cycles at 300 °C. As for single growth temperatures, 300 °C leads to the lowest density of states distributed away from the interface to the insulator [disorder-induced gap states (DIGS)], but to the highest interfacial state density (Dit). However, by using 300∕500°C double growth temperatures it is possible to maintain low DIGS values and to improve the interface quality in terms of Dit. The very first ALD cycles define the dielectric properties very near to the dielectric-semiconductor interface, and growing an upper layer at higher ALD temperature produces some annealing of interfacial states, thus improving the interface quality. Also, samples in which the only layer or the upper one was grown at the highest temperature (800 °C) show the poorest results both in terms of Dit and DIGS, so using very high temperatures yield defective dielectric films.

Thin films of the tetragonal rutile-type SnO2 phase have been deposited by both atomic layer deposition (ALD) and chemical vapour deposition (CVD) using the SnI4–O2 precursor combination. Depositions were carried out in the temperature region of 350–750°C on α-Al2O3(0 1 2) substrates. In both cases the films were found to grow epitaxially with the in-plane orientation relationships [0 1 0]SnO2 || [1 0 0]α-Al2O3 and [1 0 1¯]SnO2 || [1¯ 2¯ 1]α-Al2O3. Films grown by ALD were found to be close to perfectly single crystalline, contained a low density of defects and were almost atomically smooth. The CVD films were found to have a much rougher film morphology, and exhibited both grain boundaries and twin formation.

Thin films Of Co3O4 have been successfully deposited on SiO2/Si(100) and MgO(001) substrates by atomic layer deposition (ALD) using the precursor combination CoI2/O-2. The deposition temperature was found to have a strong influence on the growth rate. On SiO2/Si(100) substrates, growth rates of about 0.2 nm per cycle were recorded at 500 degrees C, decreasing to 0.004 nm per cycle at 700 degrees C. Oil MgO(001) substrates the growth rates were lower, reaching about 0.12 nm per cycle at 475 degrees C, while no growth could be detected at 700 degrees C. The films were found to grow as the cubic Co3O4 phase throughout the temperature range 475-700 degrees C, polycrystalline on SiO2/Si(100), and epitaxial on MgO(001). On MgO(001) the epitaxial relationship was established to the in-plane orientation (001)[100](Co3O4)parallel to(001)[100](MgO). No iodine could be detected by Rutherford backscattering spectroscopy (RBS) or by X-ray fluorescence (XRF) spectroscopy in any of the deposited films.

This work examines the structural and electrical properties of HfSixOy film based metal-insulator-semiconductor capacitors by means of x-ray diffraction, x-ray photoelectron spectroscopy, capacitance-voltage (C-V), deep level transient spectroscopy, and conductance transient (G-t) techniques. Hafnium-rich silicate films were atomic layer deposited onto HF-etched or SiO2 covered silicon. Although as-deposited samples exhibit high interfacial state and disorder-induced gap state densities, a postdeposition thermal annealing in vacuum under N2 flow for 1min at temperatures between 600 and 730°C clearly improves the interface quality. Marked crystallization and phase separation occurred at 800°C, increasing the structural heterogeneity and defect density in the dielectric oxide layers.

HfO2 films were atomic layer deposited from HfCl4 and H2O on Si(100) in the temperature range of 300–600 °C. At low temperatures, films grow faster and are structurally more disordered, compared to films grown at high temperatures. At high temperatures, the films are better crystallized, but grow slower and contain grain boundaries extending from substrate to gate electrode. Film growth rate and capacitance of HfO2 dielectric layers was improved by depositing stacked structures with polycrystalline films of higher purity at 600 °C on thin HfO2 sublayer grown on Si at 300 °C.

Amorphous niobium oxide (Nb 2 O 5 ) nano-tubes were fabricated inside anodic alumina templates using atomic layer deposition (ALD). The nanoporous templates were in-house fabricated anodic alumina membranes having an inter-pore distance of about 100 nm with pores lengths of 2 µm. The pores were parallel and well ordered in a hexagonal pattern. Atomic layer deposition was performed using gas pulses of niobium iodide (NbI 5 ) and oxygen separated by purging pulses of argon. By employing long gas pulses (30 s) it was possible to get coherent and amorphous Nb 2 O 5 films conformally covering the pore-walls of the alumina template. The outer diameter of the nano-tubes was tailored between 40 and 80 nm by using alumina templates with different pore sizes. By using template membranes with pores not opened in the bottom, nano-tubes with one side closed could be fabricated. Free-standing, and still parallel, nano-tubes could be obtained by selectively etching away the alumina template using phosphoric acid. Using the above mentioned procedure it was possible to fabricate unsurpassed parallel niobium oxide nano-tubes of equal length, diameter and wall-thickness, ordered in a perfect hexagonal pattern. The samples were analysed using high resolution scanning electron microscopy (HR-SEM), transmission electron microscopy (TEM), electron diffraction and x-ray fluorescence spectroscopy (XRFS).

HfO2 films were grown by atomic layer deposition from HfCl4 and H2O on atomic layer deposited 40-70 nm thick platinum, iridium, and ruthenium films in the temperature range 200-600 degrees C. The phase formed in the 30-50 nm thick HfO2 films was monoclinic HfO2 dominating over amorphous material without noticeable contribution from metastable crystallographic polymorphs. The metal-dielectric-metal capacitor structures formed after evaporating Al gate electrodes demonstrated effective permittivity values in the range 11-16 and breakdown fields reaching 5 MV/cm. Iridium electrode films showed the highest stability in terms of reliability and reproducibility of dielectric characteristics. (c) 2005 The Electrochemical Society. All rights reserved.

High-resolution transmission electron microscopy and electron energy loss spectrometry were used to characterize the interfacial layer formed between the silicon substrate and the HfO2 thin film grown by atomic layer deposition (ALD) from HfI4 and O2. The interfacial layer was amorphous and contained SiO2 mixed with a small amount of elemental Si on the atomic level. The interfacial silicon oxide layer was mainly deposited at the beginning of the ALD process since its thickness was insensitive to the number of applied ALD cycles when increased from 50 to 1000.

Hf O 2 films were atomic layer deposited from HfCl4 and H2O on Si(100) in the temperature range of 226–750°C. The films consisted of dominantly the monoclinic polymorph. Elastic recoil detection analysis revealed high residual chlorine and hydrogen contents (2–5at.%) in the films grown below 300–350°C. The content of residual hydrogen and chlorine monotonously decreased with increasing growth temperature. The effective permittivity insignificantly depended on the growth temperature and water partial pressure. Capacitance-voltage curves exhibited marked hysteresis especially in the films grown at 400–450°C, and demonstrated enhanced distortions likely due to the increased trap densities in the films grown at 700–750°C. Changes in water pressure led to some changes in the extent of crystallization, but did not induce any clear changes in the capacitance of the dielectric layer.

Thin films of SnO2 have been successfully deposited by atomic layer deposition (ALD) using the SnI4/O-2 precursor combination. Depositions were carried out in the temperature range 400-750degreesC on SiO2/Si(100) and single-crystal line alpha-Al2O3(012) substrates. The films were found to grow as the tetragonal SnO2 phase (cassiterite), polycrystalline on SiO2/Si(100), and epitaxial on the alpha-Al2O3(012) substrates with the in-plane orientation relationships [010](SnO2) parallel to [100](alpha-Al2O3) and [10 (1) over bar](SnO2) parallel to [(1) over bar(2) over bar1](alpha-Al2O3). In general the growth rate was high, changing from 0.10 nm cycle(-1) at 500degreesC to 0.12 nm cycle(-1) at 750degreesC for the alpha-Al2O3(012) substrates, and from 0.04 nm cycle(-1) at 400 degreesC to 0.24 nm cycle(-1) at 750degreesC for the SiO2/Si(100) substrates.