Anders Hårsta

Self-Supported Three-Dimensional Nanoelectrodes for Microbattery Applications

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.

Atomic layer deposition of zirconium oxide from zirconium tetraiodide, water and hydrogen peroxide

Atomic layer deposition of zirconium oxide from zirconium tetraiodide, water and hydrogen peroxide

Properties of hafnium oxide films grown by atomic layer deposition from hafnium tetraiodide and oxygen

Polycrystalline monoclinic HfO2 films were atomic layer deposited on Si(100) substrates by a nonhydrous carbon-free process of HfI4 and O2. The oxygen to hafnium ratio corresponded to the stoichiometric dioxide within the limits of accuracy of ion beam analysis. A 1.5–2.0 nm thick SiO2 interface layer formed between the HfO2 films and Si substrates. Hysteresis of the capacitance–voltage curves was observed in Al/HfO2/p-Si(100) structures with oxide grown in the substrate temperature range of 570–755 °C. The hysteresis ceased with an increase in O2 pressure. The effective permittivity of the dielectric layers varied between 12 and 16. The breakdown voltages were found to be lower in the case of higher oxygen doses and higher HfO2 deposition temperatures.

A frequency response and transient current study of β-Ta2O5: Methods of estimating the dielectric constant, direct current conductivity, and ion mobility

Dielectric ac measurements in the frequency range of ∼1 mHz–1 MHz were performed on β-Ta2O5 samples made by chemical vapor deposition. A method of estimating the dielectric constant and the dc conductivity from the dielectric response was developed. The high-frequency dielectric constant was found to be 25.84 with no detectable temperature dependence and the dc conductivity due to protons had an activation energy of about 0.4 eV in the studied temperature range (from 24 to 90 °C). Evidence for the conduction mechanism being protonic rather then electronic was found from isothermal transient ionic current (ITIC) measurements. The ITIC recordings could also determine conduction parameters, such as proton mobility, number of charge carriers, and dc conductivity.

Atomic Layer Chemical Vapor Deposition of TiO2 Low Temperature Epitaxy of Rutile and Anatase

Atomic layer chemical vapor deposition of TiO2: Low-temperature epitaxy of rutile and anatase

Dielectric Properties of Zirconium Oxide Grown by Atomic Layer Deposition from Iodide Precursor

Dielectric properties of zirconium oxide grown by atomic layer deposition from iodide precursors

Influence of thickness and growth temperature on the properties of zirconium oxide films grown by atomic layer deposition on silicon

Abstract ZrO2 films of thicknesses varied in the range of 3–30 nm were atomic layer deposited from ZrI4 and H2O–H2O2 on p-Si(100) substrates. The effects of film thickness and deposition temperature on the structure and dielectric properties of ZrO2 were investigated. At 272 and 325 °C, the growth of ZrO2 started with the formation of the cubic polymorph and continued with the formation of the tetragonal polymorph. The ratio between the lattice parameters increased with the film thickness and growth temperature. The effective permittivity, determined from the accumulation capacitance of Hg/ZrO2/Si capacitors, increased with the film thickness, reaching 15–17 in 25-nm-thick films. The permittivity decreased with the increasing growth temperature. The hysteresis of the capacitance–voltage curves was the narrowest for the films deposited at 325 °C, and increased towards both lower and higher deposition temperatures.

Atomic Layer Deposition of Titanium Oxide from TiI4 and H2O2

TiO2 thin films have been grown on amorphous soda lime glass and polycrystalline silicon substrates from TiI4 and H2O2 by atomic layer deposition (ALD) in the temperature range 250–490 °C. The film growth rate and refractive index increased linearly with growth temperature up to 300 °C. Between 300 °C and 400 °C, the film growth rate tended to stabilize. Above 400 °C, there was a further rapid increase in the growth rate, together with a corresponding increase in the thickness profile. The refractive index reached 2.70–2.75 in the films grown above 300 °C. The films contained low amounts of residual hydrogen and were virtually iodine-free. When deposited below 300 °C and above 325 °C, the films contained weakly crystallized, but still distinct, anatase and rutile phases, respectively. Reflective high-energy electron diffraction (RHEED) studies revealed that the uppermost layers of the films grown on silicon at 275 °C, 325 °C, and 425 °C contained anatase phase, regardless of deposition temperature. In the temperature range 300–325 °C, a transition region was established where either the films became less ordered, or they contained rather strongly ordered, but unstable, suboxide phases. The suboxide phase, when present, was transformed into a mixture of anatase and rutile when stored in air at room temperature.

Atomic Layer CVD in the Bi–Ti–O System

Thin films in the Bi-Ti-O system have, for the first time, been deposited by atomic layer CVD (ALCVD) using triphenyl bismuth, titanium isopropoxide, and water as precursors. The influence of the Bi:Ti precursor pulsing ratio at the deposition temperature of 260 °C and the influence of deposition temperature in the interval 200-325 °C were investigated. The growth rates of the films were about 0.2 A/metal cycle, and the carbon content was less than 1.5 at.-%. The as-deposited films contained metallic bismuth but became amorphous upon annealing at 500 °C in air, and further annealing resulted in the formation of the dielectric Bi 2 Ti 2 O 7 phase. The films annealed at 500 °C had permittivity values of around 60.

Properties of HfO2 Thin Films Grown by ALD from Hafnium tetrakis(ethylmethylamide) and Water

Hf02 films were grown by atomic layer deposition (ALD) fromHf[N(CH3)(C2H5)]4 and H2O on Si(lOO) substrates. The Thickness of 5-45 nm thick films on HF-etched SI was proportinal to the number of growth cycles. Crystallization was observedin the 30-45 nm thick films, containing the monoclinic Hf02 polymorph. Films with thicknesses lower than 10 nm wereamorphous. The effective permittivity of the dielectric films varied between 6.5 and 17. The leakage and capacitive characteristics did not show any clear dependence on the HfO2 growth temperature.