Xiaolin Wang

Universität Kassel, Cassel, Hesse, Germany

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Publications (7)1.2 Total impact

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    ABSTRACT: We report a novel 3D NanoImprint methodology with very high vertical resolution well below 1 nm and a minimum surface roughness down to 0.2 nm in root mean square (rms) which is attractive for several applications. We introduce our 3D NanoImprint methodology in fabricating 3D filter cavities of Fabry–Pérot filter arrays for optical nanospectrometers. A large number of different cavity heights can be fabricated in one single imprint step using this high resolution, low-cost 3D NanoImprint technology. The key issue of developing 3D NanoImprint technology is the fabrication of high resolution templates. The novel 3D templates contain arrays of negative or positive checkerboard-like mesa structures with currently up to 64 different heights. Different types of 3D templates were developed and adapted to cutting edge NanoImprint methods and imprint resists. The performance of different 3D NanoImprint recipes was investigated. Based on the novel 3D NanoImprint technology developed in this work, static Fabry–Pérot filter arrays with NanoImprinted cavities indicated rather high filter transmission (best single filter >90%), small line widths (about 2 nm in full width at half maximum) and broad stop bands.
    Full-text · Article · Oct 2013 · Microelectronic Engineering
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    ABSTRACT: Photonic components, including functionalized nanostructured surfaces, obtain increasing importance. With decreasing size, the physical limits of conventional fabrication techniques such as photolithography and etching are encountered. Conventional Nanolmprint templates are mainly focused on only high lateral resolution down to 5 nm [1 ]. Thus, three dimensional (3D) photonic nanostructures, requiring also precise vertical height-control, cannot be addressed on the basis of the conventional technology. In this paper, we present high vertical resolution 3D Nanolmprint technologies and its applications concerning strongly miniaturized spectrometers (nanospectrometers) with optical resolution (λ⁄Δλ) up to 500. Our nanospectrometer consists of a 2D array of Fabry-Pérot (FP) filters, designed to match exactly to a 2D CCD detector array in lateral direction with a resulting system size of 2 x 2 x 4 mm³. The 3D filter cavities were imprinted using both 3D UV-Nanolmprint (UV-NI) technology and Substrate Conformal Imprint Lithography (SCIL). For the deposition of Distributed Bragg Reflectors (DBRs), Plasma Enhanced Chemical Vapour Deposition (PECVD) as well as fen Beam Sputtering Deposition (IBSD) were applied. The filter arrays required for the spectrometer have been demonstrated to have an ultra-high transmittance > 80 % and a Full Width at Half Maximum (FWHM) of down to 1 nm.
    Full-text · Article · Oct 2012 · Nonlinear Optics Quantum Optics
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    ABSTRACT: Microspectrometers are very important and reveal a high potential for networked sensing systems. They are widely implemented in both industrial and scientific applications. A novel Fabry-Pérot-based nanospectrometer with nanoimprinted cavities has been designed. The key parts of the nanospectrometer are Fabry-Pérot filter arrays with different cavity heights which have been fabricated and characterized in detail. All different filter cavities were fabricated in a single step using novel 3D nanoimprint technology with our high vertical resolution 3D nanoimprint templates. Potential combinations of nanoimprint methods and imprint resists were used and characterized. Plasma enhanced chemical vapour deposition (PECVD) and ion beam deposition (IBD) were processed in parallel for depositing distributed Bragg reflectors (DBRs). The filter arrays have been demonstrated to have an ultra-high filter transmittance up to 97%, small line width (FWHM) of less than 2.5 nm and a rather broad stop band over 200 nm.
    Full-text · Conference Paper · Jul 2010
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    ABSTRACT: The Fabry-Pérot filters are based on SiO2/Si3N4 mirrors and air gap cavities, suitable for selecting a very narrow filter line. The air gap cavity is produced by underetching the sacrificial layer mr-UVCur06 polymer to enable electrostatic actuation of the membranes. 75 nm spectral tuning is presented for an electrostatic voltage variation of 0-30 Volts in the visible range.
    No preview · Conference Paper · Jan 2010
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    ABSTRACT: Optical microsensors and photonic devices obtain increasing importance in various applications including industry process control, medicine, biology, space technology, food and agriculture. 3D microstructures are preferred by many types of micro-optical devices, such as micro-optical spectrometers, which are difficult or expensive to be fabricated using conventional fabrication technology such as photolithography and etchingprocesses. Commercially available NanoImprint templates provide only high lateral resolution [1]. It limits the applications of 3D nanostructures which require also precise vertical height-control. We present our 3D NanoImprint technology with sub-nm vertical resolution and its application in nanospectrometers with optical resolutions (λ/∆λ) up to 600. Our nanospectrometer consists of a 2D array of Fabry-Pérot (FP) filters matching to a 2D CCD sensor array that have a size of 2x2x4 mm3. As shown in Fig.1 due to thin film interference, only the light within the designed narrow transmission band of each single filter can pass through the same filter and then be detected by the corresponding sensor pixel. Conventional grating spectrometers, which were miniaturized down to several centimeters, are limited by their resolution (~10-140) and by this reason not applicable for many applications. Fabry-Pérot filter array based microspectrometers were developed by some groups [2,3] and show great potential. However, to fabricate the 3D cavities with different heights, they implemented subsequent lithography, etching or deposition processes, which leads to high cost in fabrication and limits the potential in commercial application. In contrary, we implemented a novel methodology of fabricating Fabry-Pérot filter array based microspectrometers and fabricated all the Fabry-Pérot filter cavities with different heights in a single process step using vertical high-resolution 3D NanoImprint technology (Fig.2), which considerably reduces costs. Figure 3 shows the microscope image of a Fabry-Pérot filter array. White light interferometer (WLI) images of different imprinted mesa-structures (filter cavities) are depicted in Fig 4. The vertical resolution is controlled within 1 nm because of our high vertical resolution templates [4]. Experimental spectra are displayed in Fig. 5, showing the transmission spectra of a filter array which was fabricated by UV-NanoImprint technology using imprint resist mr-UVcur21 and ion beam deposition of 5.5 pairs SiO2/TiO2 DBRs. The obtained line width (FWHM) of about 3 nm for all filters and the transmittance up to 70% ensure a remarkable resolution of the developed nanospectrometer. The best single filter line width (FWHM) is down to 1 nm, while the best single filter transmission is up to 97%.
    Full-text · Conference Paper · Jan 2010
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    ABSTRACT: Nanoimprint is an emerging technology which is considered to have great influence in the near future [1]. It combines the potential of high through-put and low cost production. Corresponding methods using different methodologies and technologies, e.g., nanoimprint lithography (NIL), UV-nanoimprint lithography (UV-NIL) and soft lithography, have been developed [2-4] since the invention of nanoimprint in 1996 [5]. Highly precise lateral structures down to 6nm were recently reported to be patterned using nanoimprint [6]. While research mainly focuses on the improvement of the lateral resolution, for some applications it is important to improve and to control the vertical resolution. However, it is still extremely challenging to precisely apply arbitrary heights of 3D template structures in a flexible way. We developed new methods to fabricate 3D nanoimprint templates with ultra-high vertical resolution. The presented templates contain arrays of negative or positive mesa structures up to 64 different heights for test purposes. The differences of height levels were set from several nm to around 200 nm, while lateral features were designed in the µm range. Opaque templates for NIL and transparent templates for UV-NIL with negative patterns were produced, as well as master templates for soft lithography with positive patterns. Those 3D patterns of our templates were characterized using white light interferometry [7] to implement fast and accurate measurements. The best results of the opaque and master templates show surface roughness below 0.2 nm and vertical precision below 1 nm, while the transparent templates obtain surface roughnesses of about 0.5 nm and vertical precision below 2 nm. Filter arrays with dielectric DBRs and organic cavities were fabricated using 3D nanoimprint templates. Transparent templates and UV-NIL were implemented to structure the cavities with designed heights. DBRs were deposited by PECVD. Preliminary results show a filter transmittance of up to 90% and a linewidth (FWHM) of less than 3nm. The presented high vertical resolution 3D nanoimprint templates provide a valuable base for further research on the area of nanoimprint. Besides, they reveal great potential for nanophotonic applications, such as nanospectrometers, organic lasers and optical waveguides, as well as nanofluidics.
    No preview · Conference Paper · Jan 2009
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    ABSTRACT: english: Surfaces whose functionality is due to fine-structured surfaces, are of increasing importance. Their wider use, however, calls for a means of production better than conventional photolithography. Such a method is offered by nano-imprint lithography, an impression technique allowing the most finely-detailed structures to be formed. Areas of application include optics, electronics, meeical technology and photovoltaics. german: Oberflächen mit funktionellen Eigenschaften feinere Strukturen haben in zunehmendem Maße an Bedeutung gewonnen. Allerdings müssen zu deren Herstellung über die konventionelle photolithografischen Techniken neue Verfahren entwickelt werden. Eine solche Technologie ist die Nanoimprint-Lithografie, die auf einem Abdruckverfahren mit kleinsten Strukturabmessungen beruht. Deren Anwendungsmöglichkeiten wird an Beispielen aus der Optik, Elektronik, Medizintechnik und Photovoltaik vorgestellt.
    No preview · Article · Jan 2009 · Galvanotechnik