Showing papers by "Ulf Helmersson published in 2005"
TL;DR: In this article, the ion to neutral ratio of the sputtered material have been studied for high power pulsed magnetron sputtering and compared with a continuous direct current discharge using the same experimental setup except for the power source.
Abstract: The ion to neutral ratio of the sputtered material have been studied for high power pulsed magnetron sputtering and compared with a continuous direct current (dc) discharge using the same experimental setup except for the power source. Optical emission spectroscopy (OES) was used to study the optical emission from the plasma through a side window. The emission was shown to be dominated by emission from metal ions. The distribution of metal ionized states clearly differed from the distribution of excited states, and we suggest the presence of a hot dense plasma surrounded by a cooler plasma. Sputtered material was ionized close to the target and transported into a cooler plasma region where the emission was also recorded. Assuming a Maxwell–Boltzmann distribution of excited states the emission from the plasma was quantified. This showed that the ionic contribution to the recorded spectrum was over 90% for high pulse powers. Even at relatively low applied pulse powers, the recorded spectra were dominated by emission from ions. OES analysis of the discharge in a continuous dc magnetron discharge was also made, which demonstrated much lower ionization.
229 citations
TL;DR: In this article, the authors synthesized Ta thin films on Si substrates placed along a wall of a 2 cm-deep and 1 cm-wide trench, using both a mostly neutral Ta flux by conventional dc magnetron sputtering (dcMS) and a mostly ionized Ta flux (HPPMS) by high-power pulsed magnetron stuttering.
Abstract: We have synthesized Ta thin films on Si substrates placed along a wall of a 2-cm-deep and 1-cm-wide trench, using both a mostly neutral Ta flux by conventional dc magnetron sputtering (dcMS) and a mostly ionized Ta flux by high-power pulsed magnetron sputtering (HPPMS). Structure of the grown films was evaluated by scanning electron microscopy, transmission electron microscopy, and atomic force microscopy. The Ta thin film grown by HPPMS has a smooth surface and a dense crystalline structure with grains oriented perpendicular to the substrate surface, whereas the film grown by dcMS exhibits a rough surface, pores between the grains, and an inclined columnar structure. The improved homogeneity achieved by HPPMS is a direct consequence of the high ion fraction of sputtered species.
222 citations
TL;DR: In this article, the spatial electron density distribution was measured as a function of time in a high-power pulsed magnetron discharge and a Langmuir probe was positioned in various positions below the target and the electron density was mapped out.
Abstract: The spatial electron density distribution was measured as function of time in a high-power pulsed magnetron discharge. A Langmuir probe was positioned in various positions below the target and the electron density was mapped out. We recorded peak electron densities exceeding 10/sup 19/ m/sup -3/ in a close vicinity of the target. The dynamics of the discharge showed a dense plasma expanding from the "race-track" axially into the vacuum chamber. We also record electrons trapped in a magnetic bottle where the magnetron magnetic field is zero, formed due to the unbalanced magnetron.
106 citations
TL;DR: In this paper, a high-power pulsed magnetron discharge with high power pulses (peak power of 0.5 MW) and a repetition frequency of 20 ms was studied.
Abstract: We report on electrostatic probe measurements of a high-power pulsed magnetron discharge. Space- and time-dependent characteristics of the plasma parameters are obtained as functions of the process parameters. By applying high-power pulses (peak power of ~0.5 MW), with a pulse-on time of ~100 µs and a repetition frequency of 20 ms, peak electron densities of the order of ~1019 m− 3, i.e. three orders of magnitude higher than for a conventional dc magnetron discharge, are achieved soon after the pulse is switched on. At high sputtering gas pressures (>5 mTorr), a second peak occurs in the electron density curve, hundreds of microseconds after the pulse is switched off. This second peak is mainly due to an ion acoustic wave in the plasma, reflecting off the chamber walls. This is concluded from the time delay between the two peaks in the electron and ion saturation currents, which is shown to be dependent on the chamber dimensions and the sputtering gas composition. Finally, the electron temperature is determined, initially very high but decreasing rapidly as the pulse is turned off. The reduction seen in the electron temperature, close to the etched area of the cathode, is due to cooling by the sputtered metal atoms.
103 citations
TL;DR: In this article, the perovskite structures of the Na0.5K 0.5NbO3 (NKN) have been synthesized with three different sol-gel methods, viz. the alkoxide method, a modified Pechini method and a somewhat novel oxal oxal method.
50 citations
TL;DR: In this article, the authors propose to eliminate the hysteresis effects in the processing curves of reactive sputter processes, which is the cause of the stability problems of these processes.
Abstract: Reactive sputter processes frequently exhibit stability problems. The cause of this is that these processes normally exhibit hysteresis effects in the processing curves. Eliminating the hysteresis ...
47 citations
TL;DR: In this article, the creation and propagation of ion-acoustic solitary waves in a high power pulsed magnetron sputtering discharge is described, where a dense localized plasma is created by applying high energy pulses (4 − 12 J) of length ≈70 µs, at a repetition frequency of 50 pulses per second, to a planar magnetron source.
Abstract: We report on the creation and propagation of ion-acoustic solitary waves in a high power pulsed magnetron sputtering discharge. A dense localized plasma is created by applying high energy pulses (4–12 J) of length ≈70 µs, at a repetition frequency of 50 pulses per second, to a planar magnetron sputtering source. The temporal behaviour of the electron density, measured by a Langmuir probe, shows solitary waves travelling away from the magnetron target. The velocity of the waves depends on the gas pressure but is roughly independent of the pulse energy.
45 citations
TL;DR: In this paper, the effects of substitutional additives on the properties and phase stability of - and -alumina (Al2O3) are investigated by density functional theory total energy calculations.
Abstract: The effects of substitutional additives on the properties and phase stability of - and -alumina (Al2O3), are investigated by density functional theory total energy calculations. The dopants explore ...
26 citations
01 Jan 2005
TL;DR: High power impulse magnetron sputtering (HIPIMS) as discussed by the authors is a promising technique for utilizing ionized PVD in many industrial coating processes, which results in a high degree of ionization of the deposition material.
Abstract: High power impulse magnetron sputtering (HIPIMS) is a promising technique for utilizing ionized PVD in many industrial coating processes. The HIPIMS process results in a high degree of ionization of the deposition material. Reported values of ionization range from 4.5% up to more than 90%. This is of immense interest since ions are controllable with respect to energy and direction, using electric or magnetic fields, as they arrive at the growth surface. This opens up new avenues in magnetron sputtering. Furthermore, guiding the material to and away from surfaces is obtainable to some degree. This makes the HIPIMS process similar to arc-evaporations in many respects, however, without the drawback of macro-particle generation. Here we review the present status of the development of the HIPIMS and discuss areas where further improvements are needed for a successful application of the technique.
18 citations
TL;DR: In this article, the properties of NKN thin films were studied and a large response of 3.3 V was obtained, and the conductivity of the NKN film in hydrogen ambient is higher than in oxygen ambient.
Abstract: Hydrogen sensing properties of sodium potassium niobate NaxKyNbOz (NKN) thin films were studied. The NKN thin films were prepared by reactive rf magnetron sputtering. NKN is a ferroelectric material with high dielectric constant. The polarization increases in hydrogen ambient and decreases in oxygen ambient. The conductivity of the NKN film in hydrogen ambient is higher than in oxygen ambient, and these changes are reversible. The threshold voltage of the current–voltage (I–V) characteristics depends on the hydrogen concentration, and a large response of 3.3 V was obtained.
3 citations