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Diamond Microfabrication for Applications in Optics and Chemical Sensing
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Diamond is a material with many exceptional properties. In this thesis methods for fabrication of microstructures as well as several applications of such structures in optics, microfluidics and electrochemistry are presented.

A method for etching deep and highly precise gratings is described. This method was used to fabricate circularly symmetric half wave plates for use in vector vortex coronagraphs. Such coronagraphs are a very promising approach to the direct imaging of extrasolar planets.

By varying the lateral etch rate of the aluminum mask during diamond etching in an inductively coupled plasma, the sidewall angle of the etched structures could be controlled. This method was used to make smooth sloped sides on a waveguide for coupling light into it. Antireflective structures that drastically reduced the surface reflection in a wavelength band between 10 and 50 µm were also fabricated.

An array of boron doped diamond microelectrodes for electrochemical measurements in a microchannel was fabricated and tested, showing very good stability and reusability. Several hundred hours of use did not adversely affect their performance and no damage to them could be detected by atomic force microscopy or scanning electron microscopy.

Superhydrophobic surfaces in diamond were demonstrated, using both hydrogen and fluorine termination. Hydrogen termination on a flat surface gives contact angles below 90°. To achieve a superhydrophobic surface with this low intrinsic hydrophobicity, structures looking like microscopic nail heads were fabricated. The effect of water pressure on immersed superhydrophobic surfaces was also studied and it was found that the collapse of the superhydrophobic state due to pressure was sometimes reversible as the pressure was lowered.

Finally, a method was tested for functionalizing diamond surfaces using block copolymers of polyethylene oxide and polypropylene oxide to both passivate the surface and to attach synthetic binder molecules. This method was found to give very high signal to noise ratios when detecting C-reactive protein.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2013. , 65 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1015
Keyword [en]
diamond, microfabrication, microoptics, coronagraph, waveguide, microelectrodes, superhydrophobic
National Category
Manufacturing, Surface and Joining Technology Astronomy, Astrophysics and Cosmology
Research subject
Engineering Science with specialization in Microsystems Technology
Identifiers
URN: urn:nbn:se:uu:diva-192567ISBN: 978-91-554-8587-0 (print)OAI: oai:DiVA.org:uu-192567DiVA: diva2:600078
Public defence
2013-03-08, Polacksbacken 2347, Lägerhyddsvägen 2, Uppsala, 10:00 (English)
Opponent
Supervisors
Available from: 2013-02-14 Created: 2013-01-22 Last updated: 2013-04-02
List of papers
1. High aspect ratio optical gratings in diamond
Open this publication in new window or tab >>High aspect ratio optical gratings in diamond
2013 (English)In: Diamond and related materials, ISSN 0925-9635, E-ISSN 1879-0062, Vol. 34, 19-24 p.Article in journal (Refereed) Published
Abstract [en]

In this paper we describe a process for fabricating high aspect ratio gratings in single- or polycrystalline diamond with the high precision required by micro-optics. Nanoimprint lithography with a soft stamp and several layers of hard masks allowed for rapid and accurate replication of patterns written by e-beam or laser into thick Al masks on diamond substrates as large as 2 cm in diameter. Vertical sidewalls in the mask were crucial for avoiding microvilli formation during diamond plasma etching and were achieved by etching and oxidizing the Al mask in cycles. Circularly symmetric half-wave plates for wavelength bands around 4 and 11 mu m were fabricated with deep circular gratings on one side and antireflective gratings on the other.

Keyword
Reactive ion etching, synthetic diamond, plasma etching, grating, optics, interface structure
National Category
Manufacturing, Surface and Joining Technology Astronomy, Astrophysics and Cosmology
Research subject
Engineering Science with specialization in Microsystems Technology
Identifiers
urn:nbn:se:uu:diva-192561 (URN)10.1016/j.diamond.2013.01.009 (DOI)000317795400004 ()
Available from: 2013-01-22 Created: 2013-01-22 Last updated: 2017-12-06Bibliographically approved
2. Design, manufacturing, and performance analysis of mid-infrared achromatic half-wave plates with diamond subwavelength gratings
Open this publication in new window or tab >>Design, manufacturing, and performance analysis of mid-infrared achromatic half-wave plates with diamond subwavelength gratings
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2012 (English)In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 51, no 24, 5897-5902 p.Article in journal (Refereed) Published
Abstract [en]

In this paper, we present a solution for creating robust monolithic achromatic half-wave plates (HWPs) for the infrared, based on the form birefringence of subwavelength gratings (SWGs) made out of diamond. We use the rigorous coupled wave analysis to design the gratings. Our analysis shows that diamond, besides its outstanding physical and mechanical properties, is a suitable substrate to manufacture mid-infrared HWPs, thanks to its high refractive index, which allows etching SWGs with lower aspect ratio. Based on our optimized design, we manufactured a diamond HWP for the 11-13.2 mu m region, with an estimated mean retardance similar to 3.143 +/- 0.061 rad ( 180.08 +/- 3.51 degrees). In addition, an antireflective grating was etched on the backside of the wave plate, allowing a total transmittance between 89% and 95% over the band.

National Category
Physical Sciences Engineering and Technology
Research subject
Engineering Science with specialization in Microsystems Technology
Identifiers
urn:nbn:se:uu:diva-182532 (URN)10.1364/AO.51.005897 (DOI)000308076600020 ()
Available from: 2012-10-12 Created: 2012-10-11 Last updated: 2017-12-07Bibliographically approved
3. Laboratory demonstration of a mid-infrared AGPM vector vortex coronagraph
Open this publication in new window or tab >>Laboratory demonstration of a mid-infrared AGPM vector vortex coronagraph
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2013 (English)In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 553, A98- p.Article in journal (Refereed) Published
Abstract [en]

Context. Coronagraphy is a powerful technique to achieve high contrast imaging, hence to image faint companions around bright targets. Various concepts have been used in the visible and near-infrared regimes, while coronagraphic applications in the mid-infrared nowadays remain largely unexplored. Vector vortex phase masks based on concentric subwavelength gratings show great promise for such applications.

Aims. We aim at producing and validating the first high-performance broadband focal plane phase mask coronagraphs for applications in the mid-infrared regime, and in particular the L band with a fractional bandwidth of  ~16% (3.5–4.1 μm).

Methods. Based on rigorous coupled wave analysis, we designed an annular groove phase mask (AGPM) producing a vortex effect in the L band, and etched it onto a series of diamond substrates. The grating parameters were measured by means of scanning electron microscopy. The resulting components were then tested on a mid-infrared coronagraphic test bench.

Results. A broadband raw null depth of 2 × 10-3 was obtained for our best L-band AGPM after only a few iterations between design and manufacturing. This corresponds to a raw contrast of about 6 × 10-5 (10.5 mag) at 2λ/D. This result is fully in line with our projections based on rigorous coupled wave analysis modelling, using the measured grating parameters. The sensitivity to tilt and focus has also been evaluated.

Conclusions. After years of technological developments, mid-infrared vector vortex coronagraphs have finally become a reality and live up to our expectations. Based on their measured performance, our L-band AGPMs are now ready to open a new parameter space in exoplanet imaging at major ground-based observatories.

Keyword
coronagraph diamond
National Category
Astronomy, Astrophysics and Cosmology Engineering and Technology
Research subject
Engineering Science with specialization in Microsystems Technology
Identifiers
urn:nbn:se:uu:diva-192563 (URN)10.1051/0004-6361/201321126 (DOI)000319858700098 ()
Available from: 2013-01-22 Created: 2013-01-22 Last updated: 2017-12-06Bibliographically approved
4. Inclined surfaces in diamond: broadband antireflective structures and coupling light through waveguides
Open this publication in new window or tab >>Inclined surfaces in diamond: broadband antireflective structures and coupling light through waveguides
2013 (English)In: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 21, no 3, 2693-2700 p.Article in journal (Refereed) Published
Abstract [en]

 Control of the sidewall angle of diamond microstructures was achieved by varying the gas mixture, bias power and mask shape during inductively coupled plasma etching. Different etch mechanisms were responsible for the angle of the lower and upper part of the sidewall formed during diamond etching. These angles could to some extent be controlled separately. The developed etch process was used to fabricate wideband antireflective structures with an average transmission of 96.4% for wavelengths between 10 and 50 mu m. Smooth facetted edges for coupling light through waveguides from above were also demonstrated. 

Keyword
diamond, etching, waveguide, antireflection
National Category
Manufacturing, Surface and Joining Technology Other Physics Topics
Research subject
Engineering Science with specialization in Microsystems Technology
Identifiers
urn:nbn:se:uu:diva-192566 (URN)10.1364/OE.21.002693 (DOI)000315991400015 ()
Available from: 2013-01-22 Created: 2013-01-22 Last updated: 2017-12-06
5. Designed protein binders in combination with nanocrystalline diamond for use in high-sensitivity biosensors
Open this publication in new window or tab >>Designed protein binders in combination with nanocrystalline diamond for use in high-sensitivity biosensors
Show others...
2012 (English)In: Analytical and Bioanalytical Chemistry, ISSN 1618-2642, E-ISSN 1618-2650, Vol. 404, no 6-7, 1643-1651 p.Article in journal (Refereed) Published
Abstract [en]

A platform for diagnostic applications showing signal-to-noise ratios that by far surpass those of traditional bioanalytical test formats has been developed. It combines the properties of modified nanocrystalline diamond (NCD) surfaces and those of polyethylene oxide and polypropylene oxide based block copolymers for surface passivation and binder conjugation with a new class of synthetic binders for proteins. The NCD surfaces were fluorine-, hydrogen-, or oxygen-terminated prior to further biofunctionalization and the surface composition was characterized by X-ray photoelectron spectroscopy. In a proof of principle demonstration targeting the C-reactive protein, an ELISA carried out using an F-terminated diamond surface showed a signal-to-noise ratio of 3,900 which compares well to the signal-to-noise of 89 obtained in an antibody-based ELISA on a polystyrene microtiter plate, a standard test format used in most life science laboratories today. The increase in signal-to-noise ratio is to a large extent the result of extremely efficient passivation of the diamond surface. The results suggest that significant improvements can be obtained in standardized test formats using new materials in combination with new types of chemical coatings and receptor molecules.

Keyword
Protein binders, Nanocrystalline diamond, CRP, Biosensor, Surface characterization
National Category
Natural Sciences Engineering and Technology
Research subject
Engineering Science with specialization in Microsystems Technology
Identifiers
urn:nbn:se:uu:diva-184455 (URN)10.1007/s00216-012-6245-7 (DOI)000309348400004 ()
Available from: 2012-11-09 Created: 2012-11-07 Last updated: 2017-12-07Bibliographically approved
6. From Hydrophilic to Superhydrophobic: Fabrication of Micrometer-Sized Nail-Head-Shaped Pillars in Diamond
Open this publication in new window or tab >>From Hydrophilic to Superhydrophobic: Fabrication of Micrometer-Sized Nail-Head-Shaped Pillars in Diamond
2010 (English)In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 26, no 2, 889-893 p.Article in journal (Refereed) Published
Abstract [en]

The hydrophobicity of microtextured diamond surfaces was investigated. Pillarlike structures were fabricated in both nanocrystalline diamond and microcrystalline diamond. By changing the surface termination of the textured diamond surface, we could switch between superhydrophobic surfaces and hydrophilic surfaces. Examined terminations were hydrogen, fluorine, and oxygen. To evaluate the wetting properties, advancing and receding contact angles were measured. By designing pillars with a wide diamond top on a narrower silicon stem, superhydrophobicity was achieved even when the advancing contact angle on the unstructured diamond surface was below 70°. The possibility to manipulate the hydrophobicity and the Fresnel reflection simultaneously at an infrared wavelength is also demonstrated.

Keyword
superhydrophobic diamond nanocrystalline polycrystalline cassie wenzel
National Category
Condensed Matter Physics Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-135623 (URN)10.1021/la902361c (DOI)000273403400038 ()
Note

PMID: 19775135

Available from: 2010-12-07 Created: 2010-12-07 Last updated: 2017-12-11
7. Cassie-Wenzel and Wenzel-Cassie transitions on immersed superhydrophobic surfaces under hydrostatic pressure
Open this publication in new window or tab >>Cassie-Wenzel and Wenzel-Cassie transitions on immersed superhydrophobic surfaces under hydrostatic pressure
2011 (English)In: Soft Matter, ISSN 1744-683X, E-ISSN 1744-6848, Vol. 7, no 1, 104-109 p.Article in journal (Refereed) Published
Abstract [en]

For incorporating superhydrophobic surfaces in microfluidic systems, it is important to understand the ability of the superhydrophobic state to withstand hydraulic pressure. In this paper we describe experiments to probe the collapse transition on superhydrophobic surfaces completely covered by water, where the air film formed on the surface is closed. Polyethylene foils nanoimprinted with micrometre sized pillars in different geometries and densities are used as the model superhydrophobic surfaces. The pressure required for the transition from Cassie to Wenzel state is measured for all surfaces and also compared to analytical and numerical models. We find that the closed film of trapped air helps stabilise the Cassie state at low pillar densities and that the effect of a small change in pillar sidewall angle can drastically change the collapse behaviour. Finally, the reverse transition, from Wenzel to Cassie state, is observed on densely pillared surfaces at low water pressure.

National Category
Physical Chemistry Engineering and Technology
Research subject
Engineering Science with specialization in Microsystems Technology
Identifiers
urn:nbn:se:uu:diva-134448 (URN)10.1039/C0SM00595A (DOI)000285360200015 ()
Available from: 2010-11-26 Created: 2010-11-26 Last updated: 2017-12-12
8. Fabrication of boron doped diamond microband electrodes for electrochemical detection in a microfluidic channel
Open this publication in new window or tab >>Fabrication of boron doped diamond microband electrodes for electrochemical detection in a microfluidic channel
Show others...
2011 (English)In: Diamond and related materials, ISSN 0925-9635, E-ISSN 1879-0062, Vol. 20, no 8, 1121-1124 p.Article in journal (Refereed) Published
Abstract [en]

The manufacturing and electrochemical characterisation of an array of 20 boron doped nanocrystalline diamond (BNCD) microband electrodes for use in a poly(dimethylsiloxane) (PDMS) based microfluidic system are described. The electrodes were fabricated by plasma etching of a silicon oxide- and BNCD thin film coated silicon wafer and the resulting surface structured silicon wafer was subsequently bonded to the PDMS so that the BNCD microband electrodes were located within the PDMS microchannel. The electrochemical performance of the BNCD electrodes was studied and the electrodes were found to exhibit significantly better stability than previously employed gold microband arrays.

Keyword
Nanocrystalline, Diamond film, Electrodes, Electrochemical applications, Micro electromechanical systems, Sensors
National Category
Engineering and Technology Inorganic Chemistry
Research subject
Engineering Science with specialization in Microsystems Technology; Inorganic Chemistry
Identifiers
urn:nbn:se:uu:diva-160514 (URN)10.1016/j.diamond.2011.06.024 (DOI)000295300800004 ()
Available from: 2011-10-25 Created: 2011-10-25 Last updated: 2017-12-08

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