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Negative ions: the overlooked species in thin film growth by pulsed laser deposition

Applicant Wokaun Alexander
Number 134577
Funding scheme Project funding (Div. I-III)
Research institution Paul Scherrer Institut
Institution of higher education Paul Scherrer Institute - PSI
Main discipline Physical Chemistry
Start/End 01.04.2011 - 31.03.2014
Approved amount 209'932.00
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All Disciplines (2)

Discipline
Physical Chemistry
Inorganic Chemistry

Keywords (5)

pulsed laser deposition; plasma analysis; thin film properties; thin film analysis; negative ions

Lay Summary (English)

Lead
Lay summary

Background:

The growth of thin films is an important field of fundamental and applied research and has many industrial applications. Pulsed laser deposition is on the verge to become an industrial technique for the thin film growth, mainly due to its ability to grow films of complex materials types. A fundamental understanding of the film growth and, in the case of metal oxide films, a control over the oxygen content by tuning the deposition conditions could advance the whole field. Fundamentally, it is important to understand the film growth during pulsed laser deposition (PLD) in greater detail, and the role of different species in the plasma for the growth of thin films. Previous studies have shown that the plume consists of neutral and ionic species (positive and negative) in atomic form but also of molecules, mainly as diatomic species. Our preliminary data show, however, that negative ions may account for up to ~ 40% of the total ion yield. The open question is therefore to study the role of negative ions for film growth, if we consider that positive ions are suggested to be the most important species for PLD? Negative ions have been detected in sputter deposition and the film growth benefits from an increased adatom mobility or larger “oxide formation capability”, whereas resputtering is noted as negative side effect. It is therefore important to investigate whether similar trends should be considered for PLD.

 

Goal:

The main goal is to study the role of diatomic species, mainly metal-oxygen species, on the oxygen content of the films and the general role of negative ions for film growth. In a second step we will investigate under which conditions the “best” films in terms of quality are obtained and whether this can be related to specific plume properties. The final step will be an analysis which conditions must be chosen to obtain these specific plume properties. This will allow us to optimize thin film growth by PLD and therefore to obtain possibly better films which can be utilized in applications.

 

Approach:

The combination of mass spectrometry/emission spectroscopy will be used to obtain complementary information about the plume composition. Plasma mass spectrometry will be used to detect and quantify the positive/negative ions as well as diatomic species and relate their appearance/amount and kinetic energies to the properties of films deposited for selected conditions. Emission imaging will be used additionally to analyze the distribution of species in the plasma plume and to detect conditions or materials where the distribution is non-homogenous. Plume imaging will be used to probe whether excited state species are beneficial for films growth if they reach the growing film.

For conditions where pronounced differences in the plume are detected thin films will be grown and characterized to evaluate the influence of the plume properties on the film quality, i.e. oxygen content, crystallinity, morphology, and properties.

Direct link to Lay Summary Last update: 21.02.2013

Responsible applicant and co-applicants

Employees

Publications

Publication
Influence of an O2 background gas on the composition and kinetic energies of species in laser induced La0.4Ca0.6MnO3 plasmas
Chen Jikun, Stender Dieter, Bator Matthias, Schneider Christof W., Lippert Thomas, Wokaun Alexander (2013), Influence of an O2 background gas on the composition and kinetic energies of species in laser induced La0.4Ca0.6MnO3 plasmas, in Applied Surface Science , 278, 317-320.
Relevance and formation mechanisms of negative ions upon ablation of Al2O3
Peláez Ramon J., Afonso Carmen N., Chen Jikun, Esposito Martin, Lippert Thomas, Stender Dieter, Wokaun Alexander (2012), Relevance and formation mechanisms of negative ions upon ablation of Al2O3, in J. Phys. D.: Appl. Phys. , 45, 285402.

Collaboration

Group / person Country
Types of collaboration
Laser Processing Group, Instituto de Optica, CSIC, Serrano 121, Madrid 28006, Spain Spain (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
- Exchange of personnel
EMPA Solid State Chemistry and Catalysis, Dübendorf Switzerland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
- Research Infrastructure
Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai China (Asia)
- in-depth/constructive exchanges on approaches, methods or results

Scientific events

Active participation

Title Type of contribution Title of article or contribution Date Place Persons involved
Conference on Laser Ablation (COLA 2013) Talk given at a conference Preliminary study on laser induced plasma from ultra low-density sponge-like carbon nanotube block 06.10.2013 Ischia, Italy Lippert Thomas; Chen Jikun; Wokaun Alexander;
TEP-CH 2013 - Thermoelectric Materials and Applications Talk given at a conference Adjusting the laser ablation strategy: fabrication of low-dimensional Ca3Co4O9 using PLD and LIFT 16.09.2013 EMPA Dübendorf, Switzerland Chen Jikun; Lippert Thomas; Wokaun Alexander;
EMRS 2012 Poster Influence of an O2 background gas on the kinetic energy distributions of species in laser induced plasmas 13.05.2012 Strassburg, France Chen Jikun; Wokaun Alexander; Lippert Thomas;


Awards

Title Year
Chinese government award for outstanding self-financed students abroad 2012

Associated projects

Number Title Start Funding scheme
147190 Influence of Strain and Interfaces on the Properties of Ion Conducting Thin Films for micro-Solid-Oxide-Fuel-Cells 01.05.2013 Project funding (Div. I-III)
142176 Small band-gap nanostructured perovskite materials for photovoltaic and photocatalytic hydrogen generation applications 01.01.2013 Romanian-Swiss Research Programme (RSRP)
117642 Thin oxide films by PLD: "Tracing" the oxygen and understanding its role 01.01.2008 Project funding (Div. I-III)
136211 Dynamics of Plasma Species as Generated by Laser Ablation of Al2O3 01.03.2011 International short research visits
152553 Positive or negative? Selecting the charge state of ions during pulsed laser deposition of thin films 01.07.2014 Project funding (Div. I-III)

Abstract

The growth of thin films is an important field of fundamental and applied research and has many industrial applications. Pulsed laser deposition is on the verge to become an industrial technique, mainly due to its ability to grow films of complex materials. A fundamental understanding of film growth and, in the case of metal oxide films, a control over the oxygen content by tuning the deposition conditions could advance the whole field. Fundamentally, it is important to understand the film growth during pulsed laser deposition (PLD) in greater detail, and the role of different species in the plasma for the growth of thin films. The com-bination of mass spectrometry/emission spectroscopy will be used to obtain complementary information about the plume. Plasma mass spectrometry will be used to detect and quantify positive/negative ions as well as diatomic species and relate their appearance, quantity, and kinetic energies to the properties of films. The focus will be put on the role of diatomic species, mainly metal-oxygen species, on the oxygen content of films and the general role of negative ions. Negative ions are almost never discussed or considered contributing to the film growth in PLD. Our preliminary data show, however, that negative ions may account for up to ~ 40% of the total ion yield. The open question is therefore to study the role of negative ions for film growth, if we consider that positive ions are suggested to be the most important species for PLD? Negative ions have been detected in sputter deposition and the film growth benefits from an increased adatom mobility or larger “oxide formation capability”, whereas resputtering is noted as negative side effect. It is therefore important to investigate whether similar trends should be considered for PLD. Emission imaging will be used addi-tionally to analyze the distribution of species in the plasma plume and to detect conditions or materials where the distribution is non-homogeneous. Plume imaging will be used to probe whether excited state species are beneficial for films growth if they reach the growing film. For conditions where pronounced differences in the plume are detected thin films will be grown and char-acterized to evaluate the influence of the plume properties on the film quality, i.e. oxygen content, crystallin-ity, morphology, and properties. SIMS and plasma mass spectrometry with isotopically (18O2) labeled mate-rials can be applied to follow the oxygen from the target or substrate into the growing film.
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