Daniel Lundin

High power impulse magnetron sputtering discharge

The high power impulse magnetron sputtering (HiPIMS) discharge is a recent addition to plasma based sputtering technology. In HiPIMS, high power is applied to the magnetron target in unipolar pulse ...

Cross-field ion transport during high power impulse magnetron sputtering

In this study, the effect on thin film growth due to an anomalous electron transport, found in high power impulse magnetron sputtering (HiPIMS), has been investigated for the case of a planar circular magnetron. An important consequence of this type of transport is that it affects the way ions are being transported in the plasma. It was found that a significant fraction of ions are transported radially outwards in the vicinity of the cathode, across the magnetic field lines, leading to increased deposition rates directly at the side of the cathode (perpendicular to the target surface). Furthermore, this mass transport parallel to the target surface leads to that the fraction of sputtered material reaching a substrate placed directly in front of the target is substantially lower in HiPIMS compared with conventional direct current magnetron sputtering (dcMS). This would help to explain the lower deposition rates generally observed for HiPIMS compared with dcMS. Moreover, time-averaged mass spectrometry measurements of the energy distribution of the cross-field transported ions were carried out. The measured distributions show a direction-dependent high-energy tail, in agreement with predictions of the anomalous transport mechanism.

Metagenomic De Novo Assembly of an Aquatic Representative of the Verrucomicrobial Class Spartobacteria

ABSTRACT The verrucomicrobial subdivision 2 class Spartobacteria is one of the most abundant bacterial lineages in soil and has recently also been found to be ubiquitous in aquatic environments. A 16S rRNA gene study from samples spanning the entire salinity range of the Baltic Sea indicated that, in the pelagic brackish water, a phylotype of the Spartobacteria is one of the dominating bacteria during summer. Phylogenetic analyses of related 16S rRNA genes indicate that a purely aquatic lineage within the Spartobacteria exists. Since no aquatic representative from the Spartobacteria has been cultured or sequenced, the metabolic capacity and ecological role of this lineage are yet unknown. In this study, we reconstructed the genome and metabolic potential of the abundant Baltic Sea Spartobacteria phylotype by metagenomics. Binning of genome fragments by nucleotide composition and a self-organizing map recovered the near-complete genome of the organism, the gene content of which suggests an aerobic heterotrophic metabolism. Notably, we found 23 glycoside hydrolases that likely allow the use of a variety of carbohydrates, like cellulose, mannan, xylan, chitin, and starch, as carbon sources. In addition, a complete pathway for sulfate utilization was found, indicating catabolic processing of sulfated polysaccharides, commonly found in aquatic phytoplankton. The high frequency of glycoside hydrolase genes implies an important role of this organism in the aquatic carbon cycle. Spatiotemporal data of the phylotype’s distribution within the Baltic Sea indicate a connection to Cyanobacteria that may be the main source of the polysaccharide substrates. IMPORTANCE The ecosystem roles of many phylogenetic lineages are not yet well understood. One such lineage is the class Spartobacteria within the Verrucomicrobia that, despite being abundant in soil and aquatic systems, is relatively poorly studied. Here we circumvented the difficulties of growing aquatic Verrucomicrobia by applying shotgun metagenomic sequencing on a water sample from the Baltic Sea. By using a method based on sequence signatures, we were able to in silico isolate genome fragments belonging to a phylotype of the Spartobacteria. The genome, which represents the first aquatic representative of this clade, encodes a diversity of glycoside hydrolases that likely allow degradation of various complex carbohydrates. Since the phylotype cooccurs with Cyanobacteria, these may be the primary producers of the carbohydrate substrates. The phylotype, which is highly abundant in the Baltic Sea during summer, may thus play an important role in the carbon cycle of this ecosystem. The ecosystem roles of many phylogenetic lineages are not yet well understood. One such lineage is the class Spartobacteria within the Verrucomicrobia that, despite being abundant in soil and aquatic systems, is relatively poorly studied. Here we circumvented the difficulties of growing aquatic Verrucomicrobia by applying shotgun metagenomic sequencing on a water sample from the Baltic Sea. By using a method based on sequence signatures, we were able to in silico isolate genome fragments belonging to a phylotype of the Spartobacteria. The genome, which represents the first aquatic representative of this clade, encodes a diversity of glycoside hydrolases that likely allow degradation of various complex carbohydrates. Since the phylotype cooccurs with Cyanobacteria, these may be the primary producers of the carbohydrate substrates. The phylotype, which is highly abundant in the Baltic Sea during summer, may thus play an important role in the carbon cycle of this ecosystem.

Transition between the discharge regimes of high power impulse magnetron sputtering and conventional direct current magnetron sputtering

Current and voltage have been measured in a pulsed high power impulse magnetron sputtering (HiPIMS) system for discharge pulses longer than 100 mu s. Two different current regimes could clearly be ...

Understanding the discharge current behavior in reactive high power impulse magnetron sputtering of oxides

Understanding the discharge current behavior in reactive high power impulse magnetron sputtering of oxides

Gas rarefaction and the time evolution of long high-power impulse magnetron sputtering pulses

Model studies of 400 mu s long discharge pulses in high-power impulse magnetron sputtering have been made to study the gas dynamics and plasma chemistry in this type of pulsed processing plasma. Da ...

On the electron energy in the high power impulse magnetron sputtering discharge

The temporal variation of the electron energy distribution function (EEDF) was measured with a Langmuir probe in a high power impulse magnetron sputtering (HiPIMS) discharge at 3 and 20 mTorr pressures. In the HiPIMS discharge a high power pulse is applied to a planar magnetron giving a high electron density and highly ionized sputtered vapor. The measured EEDF is Maxwellian-like during the pulse; it is broader for lower discharge pressure and it becomes narrower as the pulse progresses. This indicates that the plasma cools as the pulse progresses, probably due to high metal content of the discharge.

Argon metastables in HiPIMS: time-resolved tunable diode-laser diagnostics

Time-resolved tunable diode-laser absorption spectroscopy measurements were performed on the argon metastable (Ar-m) level 3s(2)3p(5)(P-2(3/2)degrees)4s excited at 801.478 nm, in the dense plasma r ...

Anomalous electron transport in high power impulse magnetron sputtering

Oscillating electric fields in the megahertz range have been studied in a high power impulse magnetron sputtering (HIPIMS) plasma with the use of electric field probe arrays. One possible reason fo ...

Energy flux measurements in high power impulse magnetron sputtering

The total energy flux in a high power impulse magnetron sputtering (HiPIMS) plasma has been measured using thermal probes. Radial flux (parallel to the magnetron surface) as well as axial flux (perpendicular to the magnetron surface) were measured at different positions, and resulting energy flux profiles for the region between the magnetron and the substrate are presented. It was found that the substrate heating is reduced in the HiPIMS process compared with conventional direct current magnetron sputtering (DCMS) at the same average power. On the other hand, the energy flux per deposited particle is higher for HiPIMS compared with DCMS, when taking into account the lower deposition rate for pulsed sputtering. This is most likely due to the highly energetic species present in the HiPIMS plasma. Furthermore, the heating due to the radial energy flux reached as much as 60% of the axial energy flux, which is likely a result of the anomalous transport of charged species present in the HiPIMS discharge. Finally, the experimental results were compared with theoretical calculations on energy flux of charged species and were found to be in good agreement.