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Pattern Shape Control for Heat Treatment Purification of Electron-Beam-Induced Deposition of Gold from the Me2Au(acac) Precursor
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Engineering Material Physics.
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Engineering Material Physics.ORCID iD: 0000-0003-4889-4210
2012 (English)In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 28, no 14, 6185-6191 p.Article in journal (Refereed) Published
Abstract [en]

Gold structures can be created in a scanning electron microscope (SEM) from the Me2Au(acac) precursor by direct writing with the electron beam. The as-deposited purity is usually poor, and a common purification approach is a post-annealing step that indeed is effective but also induces a volume reduction because of carbon loss and an undesirable reconfiguration of the gold structure, resulting in the loss of the original shape. We studied the shape change as a result of such purification, and to minimize this effect, the application of a tantalum and chromium buffer layer was investigated. These buffer materials are well-known for their good adhesion properties. We confirm by dedicated SEM, atomic force microscopy (AFM), and transmission electron microscopy (TEM) analysis that, for the creation of a uniform Au structure, tantalum is a better buffer layer material than chromium. Post-annealing of the Au electron-beam-induced deposition (EBID) patterns for 1 h at 600 degrees C in air resulted in a dramatic purity increase (from 8-12 atomic % Au to above 92 atomic % Au). The uncovered part of the tantalum layer can be easily etched away, resulting in a well-defined, high-purity, gold structure.

Place, publisher, year, edition, pages
2012. Vol. 28, no 14, 6185-6191 p.
National Category
Chemical Sciences
URN: urn:nbn:se:kth:diva-94045DOI: 10.1021/la203599cISI: 000302514800036ScopusID: 2-s2.0-84859575425OAI: diva2:525414
QC 20120508Available from: 2012-05-08 Created: 2012-05-07 Last updated: 2013-10-28Bibliographically approved
In thesis
1. Direct Nanoprototyping of Functional Materials via Focused Electron Beam
Open this publication in new window or tab >>Direct Nanoprototyping of Functional Materials via Focused Electron Beam
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

During recent years the demand for nanoscale materials with tailor-made functional properties as bulk species, is continuously and progressively rising for such fields as e.g. micro- and nano-electronics, plasmonics, spintronics, bio-technology, bio-sensing and life sciences. Preserving and / or improving properties of functional materials with their simultaneous size reduction and high-resolution site-specific positioning is indeed very challenging, for both conductors and insulators.

One of the advanced nanoprototyping methods that can be utilized for this purpose is the Electron-Beam-Induced Deposition, or shortly EBID. This process is based on a local decomposition by a focused electron beam of a precursor gas molecules adsorbed on the sample’s surface. The beauty of this method is that it gives a unique possibility of rapid creation of site-specific nanoscale 3D structures of precise shape in a single operation. It’s an additive process that can be easily combined with other patterns.

However, besides all the benefits, EBID has some constraints, in particular low purity of the deposited materials, due to the organometallic nature of the used precursors. Chemical composition of EBID patterns is strongly dependent on the chosen gas chemistry, the substrate, many deposition parameters and post-treatment processes applied to the deposited structures.

In our research we focused on deposition of Co, Au, SiO2, C, W and Pt, their purification and shape control. And this thesis presents an overview of our accomplishments in this field.

Depending on the gas chemistry of interest, three major purification approaches of EBID-grown materials were tested out:

- Post-deposition annealing: in air and in the controlled atmosphere,

- Deposition onto a preheated substrate,

- Deposition in the presence of reactive gases.

As a result, a dramatic purity improvement was observed and a significant advancement was achieved in creation of high-purity gold, cobalt and silicon dioxide nanoscale structures. In particular:

1)   For the Me2Au(acac) precursor, we developed a nanofabrication routine combining application of wetting buffer layers, fine tuning of EBID parameters and subsequent post-annealing step, which led to formation of high-purity planar and high aspect ratio periodic Au nanopatterns. We also describe the adopted and gently adjusted wet etching method of undesirable buffer layer removal, required in some cases for the further device application.

2)   For the Co2(CO)8 precursor, in-situ seeded growth in conjunction with EBID at the elevated substrate temperature resulted in a deposition of pure nanocrystalline Co with magnetic and transport properties close to the bulk material.

3)   For the tetraethyl orthosilicate precursor, or shortly TEOS, assisting of the deposition process with the additional oxygen supply led to the EBID of carbon-free amorphous insulating Si-oxide, with the absorption and refraction properties comparable to those for fused silica.

Several applications of EBID nanopatterns are also discussed.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2013. x, 85 p.
EBID, nanoprototyping, nanopatterning, nanoscale, nanostructure, purification, Au, Co, SiO2, dimethyl gold acetylacetonate, dicobalt octacarbonyl, TEOS, Dual Beam
National Category
Other Materials Engineering
urn:nbn:se:kth:diva-132365 (URN)978-91-7501-907-9 (ISBN)
Public defence
2013-11-15, F3, Lindstedtsvägen 26, Kungl Tekniska Högskolan, Stockholm, 10:00 (English)

QC 20131028

Available from: 2013-10-28 Created: 2013-10-25 Last updated: 2013-10-28Bibliographically approved

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