| 1. |
- Enoksson, Peter, 1957, et al.
(author)
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Wafer bonding for MEMS
- 2005
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In: Proceeding of the 9th International Symposium on Semiconductor Wafer Bonding: Science, Technology and Applic, Canadaations, Quebec City.
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Conference paper (peer-reviewed)
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| 2. |
- Hatami, Sepehr, 1981, et al.
(author)
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Galling related surface properties of powder metallurgical tool steels alloyed with and without nitrogen
- 2010
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In: Wear. - : Elsevier BV. - 0043-1648. ; 269:2-4, s. 229-240
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Journal article (peer-reviewed)abstract
- Two types of powder metallurgical tool steels (i.e. with and without nitrogen) are investigated with respect to their galling related surface properties. Despite similar macrohardness values, Vancron 40 (nitrogen alloyed) exhibits superior wear behaviour as compared to Vanadis 10 (without nitrogen); demonstrating approximately 20 times longer life span when used as die material in powder compaction. The main failure mechanism is mild abrasive wear for Vancron 40 and early severe galling for Vanadis 10. One important difference causing the tribological discrepancy is supposed to be associated with the preferred formation of solid lubricant oxides of the Magnéli type on the Vancron 40 surface as compared to Vanadis 10. The VN precipitates in Vancron 40 have half the thermal conductivity compared to that of the VC precipitates existing in Vanadis 10. Hence, as a result of the local accumulation of frictional heat generated during powder compaction (or any other type of forming process), Magnéli phases of V2O5 and/or VO2 are more easily formed and maintained on the Vancron 40 surface. With regard to surface oxides, the tool steels were studied by means of X-ray photoelectron spectroscopy (XPS). The tool steel surfaces were examined by means in situ SEM/AFM and electron backscatter diffraction (EBSD) for local adhesion force measurements and understanding the orientation of the phases, respectively. In addition, pin-on-disc wear tests were performed on the tool steels and the worn surfaces were analysed using scanning election microscopy (SEM) combined with energy dispersive X-ray spectroscopy (EDS).
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| 3. |
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| 4. |
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| 5. |
- Jansson, Anna, 1985, et al.
(author)
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Monitoring the osmotic response of single yeast cells through force measurement in the environmental scanning electron microscope
- 2014
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In: Measurement science and technology. - : IOP Publishing. - 0957-0233 .- 1361-6501. ; 25:2
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Journal article (peer-reviewed)abstract
- We present a measurement system that combines an environmental scanning electron microscope (ESEM) and an atomic force microscope (AFM). This combination enables studies of static and dynamic mechanical properties of hydrated specimens, such as individual living cells. The integrated AFM sensor provides direct and continuous force measurement based on piezoresistive force transduction, allowing the recording of events in the millisecond range. The in situ ESEM-AFM setup was used to study Pichia pastoris wild-type yeast cells. For the first time, a quantified measure of the osmotic response of an individual yeast cell inside an ESEM is presented. With this technique, cell size changes due to humidity variations can be monitored with nanometre accuracy. In addition, mechanical properties were extracted from load-displacement curves. A Young's modulus of 13-15 MPa was obtained for the P. pastoris yeast cells. The developed method is highly interesting as a complementary tool for the screening of drugs directed towards cellular water transport activity and provides new possibilities of studying mechanosensitive regulation of aquaporins.
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| 6. |
- Jansson, Anna, 1985, et al.
(author)
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Novel Method for Controlled Wetting of Materials in the Environmental Scanning Electron Microscope
- 2013
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In: Microscopy and Microanalysis. - 1435-8115 .- 1431-9276. ; 19:1, s. 30-37
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Journal article (peer-reviewed)abstract
- Environmental scanning electron microscopy has been extensively used for studying the wetting properties of different materials. For some types of investigation, however, the traditional ways of conducting in situ dynamic wetting experiments do not offer sufficient control over the wetting process. Here, we present a novel method for controlled wetting of materials in the environmental scanning electron microscope (ESEM). It offers improved control of the point of interaction between the water and the specimen and renders it more accessible for imaging. It also enables the study of water transport through a material by direct imaging. The method is based on the use of a piezo-driven nanomanipulator to bring a specimen in contact with a water reservoir in the ESEM chamber. The water reservoir is established by local condensation on a Peltier-cooled surface. A fixture was designed to make the experimental setup compatible with the standard Peltier cooling stage of the microscope. The developed technique was successfully applied to individual cellulose fibers, and the absorption and transport of water by individual cellulose fibers were imaged.
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| 7. |
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| 8. |
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| 9. |
- Nafari, Alexandra, 1980, et al.
(author)
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Boron at Si/SiO2 interface in SOI wafers and consequences for piezoresistive MEMS devices
- 2008
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In: MicroMechanics Europe 2008.
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Conference paper (peer-reviewed)abstract
- BESOI wafers are commonly used for MEMS fabrication and their quality is thus of great importance for the functionality and reliability of the device. It is therefore important to be aware that there is a manufacturing problem with boron impurity at the Si/SiO2 layer in the SOI wafer This impurity is not specified when purchasing the wafer and can alter the background doping up to several μm:s from the BOX, resulting in non-functional piezoresistive devices and unwanted limitation in membrane thickness. In this work we present guidelines on how to detect and counteract this impurity.
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| 10. |
- Nafari, Alexandra, 1980, et al.
(author)
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Boron impurity at the Si/SiO2 interface in SOI wafers and consequences for piezoresistive MEMS devices
- 2009
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In: Journal of Micromechanics and Microengineering. - : IOP Publishing. - 1361-6439 .- 0960-1317. ; 19:1, s. 6-
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Journal article (peer-reviewed)abstract
- In this work, the electrical performance of piezoresistive devices fabricated on thinned SOI wafers has been investigated. Specifically, SOI wafers manufactured with the standard bond-and-etch back method (BESOI), commonly used for MEMS fabrication, have been studied. Results from electrical measurements and SIMS characterization show the presence of a boron impurity close to the buried oxide, even on unprocessed wafers. If the boron impurity overlaps with the piezoresistors on the device, it can create non-defined pn-junctions and thus allow conduction through the substrate, leading to stray connections and excessive noise. The thickness of the boron impurity can extend up to several μm, thus setting a thickness limit for the thinnest parts of a MEMS device. This work shows how this impurity can fundamentally affect the functionality of piezoresistive devices. Design rules of how to avoid this are presented
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| 11. |
- Nafari, Alexandra, 1980, et al.
(author)
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Calibration methods of force sensors in the micro-Newton range
- 2007
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In: Journal of Micromechanics and Microengineering. - : IOP Publishing. - 1361-6439 .- 0960-1317. ; 17:10, s. 2102-7
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Journal article (peer-reviewed)abstract
- A micromachined capacitive force sensor operating in the micro-Newton range has been calibrated using both dynamic and static methods. Both calibrations are non-destructive, accurate and traceable to Systeme International (SI) fundamental units. The dynamic calibration is a differential mass loading resonant method where the resonance frequency with and without an added mass is measured. This gives enough information to compute the spring constant. In this paper, we evaluate the resonant mass loading method for more complex MEMS devices. Analytical calculations and finite element analysis have been performed to investigate the dynamic properties of the sensor, e.g. modal interference. The frequency response was measured with the third harmonic method where the third harmonic of the current through the sensor was measured. To detect and analyse the resonance mode of the structure during excitation, a scanning laser Doppler vibrometer was used. Two designs of a capacitive nanoindenter force sensor with flexure-type springs have been evaluated using these methods. The quality of the resonant calibration method has been tested using static mass loading in combination with transmission electron microscopy imaging of the sensor displacement. This shows that the resonant method can be extended to calibrate more complex structures than plain cantilevers. Both calibration methods used are traceable to SI fundamental units as they are based on masses weighed on a calibrated scale. The masses used do not need to be fixed or glued in any way, making the calibration non-destructive. (10 refs.)
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| 12. |
- Nafari, Alexandra, 1980, et al.
(author)
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Combining Scanning Probe Microscopy and Transmission Electron Microscopy
- 2011
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In: Scanning Probe Microscopy in Nanoscience and Nanotechnology. - 9783642104961 ; , s. 59-134
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Book chapter (other academic/artistic)abstract
- This chapter is a review of an in situ method where a scanning electron microscope (SPM) has been combined with a transmission electron microscope (TEM). By inserting a miniaturized SPM inside a TEM, a large set of open problems can be addressed and, perhaps more importantly, one may start to think about experiments in a new kind of laboratory, an in situ TEM probing laboratory, where the TEM is transformed from a microscope for still images to a real-time local probing tool. In this method, called TEMSPM, the TEM is used for imaging and analysis of a sample and SPM tip, while the SPM is used for probing of electrical and mechanical properties or for local manipulation of the sample. This chapter covers both instrumental and application aspects of TEMSPM.
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| 13. |
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| 14. |
- Nafari, Alexandra, 1980, et al.
(author)
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Electrostatic feedback for MEMS sensor for in situ TEM instrumentation
- 2008
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In: Eurosensors 2008.
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Conference paper (peer-reviewed)abstract
- A capacitive force sensor for in situ TEM instrumentation is investigated. In order to prevent movement of the suspended plate in the capacitive sensor force feedback has been investigated, primarily using CV measurements. A manual feedback has successfully been implemented and an analytical model using a serial and a parallel capacitor is presented.
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| 15. |
- Nafari, Alexandra, 1980, et al.
(author)
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Expanding in situ TEM instrumentation with MEMS technology
- 2009
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In: Commersialization of micro and nano systems (COMS) 2009. ; , s. 2-
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Conference paper (peer-reviewed)abstract
- Nanofactory Instruments is a spin off company from Chalmers University of Technology which offers instrumentation for nano-scale electrical and mechanical characterization correlated with real time imaging in situ in transmission electron microscopes (TEM).As a core component in the company’s product portfolio, proprietary MEMS sensors for quantitative force measurements on the nano-Newton and micro-Newton scales were developed. As a result of the introduction of MEMS technology into the products, added value was created and the company has now established a leading position in the market.
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| 16. |
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| 17. |
- Nafari, Alexandra, 1980, et al.
(author)
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MEMS Sensor for in Situ TEM Atomic Force Microscopy
- 2008
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In: Journal of microelectromechanical systems. - : IEEE Press. - 1057-7157 .- 1941-0158. ; 17:2, s. 328-333
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Journal article (peer-reviewed)abstract
- Here, we present a MEMS atomic force microscope sensor for use inside a transmission electron microscope (TEM). This enables direct in situ TEM force measurements in the nanonewton range and thus mechanical characterization of nanosized structures. The main design challenges of the system and sensor are to reach a high sensitivity and to make a compact design that allows the sensor to be fitted in the narrow dimensions of the pole gap inside the TEM. In order to miniaturize the sensing device, an integrated detection with piezoresistive elements arranged in a full Wheatstone bridge was used. Fabrication of the sensor was done using standard micromachining techniques, such as ion implantation, oxide growth and deep reactive ion etch. We also present in situ TEM force measurements on nanotubes, which demonstrate the ability to measure spring constants of nanoscale systems.
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| 18. |
- Nafari, Alexandra, 1980, et al.
(author)
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MEMS sensor for in situ TEM Atomic Force Microscopy
- 2007
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In: IEEE 20th International Conference on Micro Electro Mechanical Systems, 2007. MEMS. - 1084-6999. ; , s. 103-106
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Conference paper (peer-reviewed)abstract
- AbstractHere we present a MEMS atomic force microscope (AFM) sensor for use inside a transmission electron microscope (TEM). This enables direct in situ TEM force measurements in the nN range. The main design challenges of the sensor are a high sensitivity and the narrow dimensions of the pole gap inside the TEM. Fabrication of the sensor was done using standard micromachining techniques, such as ion implantation, oxide growth and deep reactive ion etch. We present in situ TEM force measurements on nanotubes, which demonstrates the ability to measure spring constants of nanoscale systems.
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| 19. |
- Nafari, Alexandra, 1980, et al.
(author)
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MEMS sensor for in situ TEM-nanoindentation with simultaneous force and current measurements
- 2009
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In: MicroMechanics Europe 2009. ; , s. 4-
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Conference paper (peer-reviewed)abstract
- Nanoindentation is a material testing method frequently used for studies of mechanical properties on the nano scale. Today, nanoindentation is also performed in situ a Transmission Electron Microscope (TEM), in order to simultaneously monitor the substrate with high resolution imaging. Here we present an extension of TEM-Nanoindention, utilizing custom designed MEMS sensor for in situ TEM use that enables simultaneous force and current measurements. The sensor is intended to be operated in electrostatic feedback mode and enable ultra high resolution TEM imaging. The design and fabrication of the sensor is presented here. Preliminary measurements show that the fabrication has been successful.
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| 20. |
- Nafari, Alexandra, 1980
(author)
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Microsensors for in situ electron microscopy applications
- 2010
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Doctoral thesis (other academic/artistic)abstract
- With the ongoing miniaturisation of devices, the interest in characterising nanoscale physical properties has strongly increased. To further advance the field of nanotechnology new scientific tools are required. High resolution imaging is one of the key components and when combined with existing characterisation tools such as Atomic Force Microscopy (AFM), Scanning Tunnelling Microscopy (STM) and nanoindentation, this enables direct imaging of real time responses and the possibility to locally probe for instance an individual nanotube. For nanoscale studies, electron microscopy and in particular Transmission Electron Microscopy (TEM) is one of the few tools with sufficiently high imaging resolution. The main challenge of such in situ instruments is the restricted space available in the millimetre sized pole piece gap of a TEM. In this work the design, fabrication and integration of two types of in situ TEM sensors is presented. The sensors are used in an in situ TEM-Nanoindentation and an in situ TEM-AFM system, providing direct and continuous force measurements. The nanoindenter force sensor utilises capacitive read out and the AFM sensor read out is based on piezoresistive detection. Both sensors were fabricated using silicon micromachining. Silicon micromachined devices have the advantage of inherently small footprint, which makes them suitable for the millimetre sized pole piece gap of the TEM. The nanoindenter force sensor operates in force ranges up to 4.5 mN and a resolution of 0.3 µN has been measured in the TEM. The AFM sensor has a force range up to 3 µN with a resolution of 15 nN at 5 kHz bandwidth. Both sensor geometries are designed such that they fit in most TEM models. The force sensors have been integrated into TEM-Nanoindenter and TEM-AFM specimen holders. The systems have been evaluated with measurements on aluminium film and nanowires. Furthermore, the AFM sensor has also been used inside a Scanning Electron Microscope (SEM) and an Environmental SEM. Studies of tool steel and living yeast cells have been performed. These measurements verify proper operation and demonstrate possible application areas of the TEM-Nanoindenter and the TEM-AFM.
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