| 1. |
- Anderson, Henrik, et al.
(författare)
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Systematic investigation of biomolecular interactions using combined frequency and motional resistance measurements
- 2011
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Ingår i: Sensors and actuators. B, Chemical. - : Elsevier BV. - 0925-4005 .- 1873-3077. ; 153:1, s. 135-144
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Tidskriftsartikel (refereegranskat)abstract
- The resonance frequency of acoustic biosensors is today used as a label-free technique for detecting mass changes on sensor surfaces. In combination with an appropriate continuous flow system it has earlier been used for affinity and kinetic rate determination. Here, we assess the potential of a modified acoustic biosensor, monitoring also the real-time dissipation through the resistance of the sensor, to obtain additional kinetic information related to the structure and conformation of the molecules on the surface. Actual interaction studies, including an attempt to determine avidity, are presented along with thorough verification of the experimental setup utilizing true viscous load exposure together with protein and DNA immobilizations. True viscous loads show a linear relationship between resistance and frequency as expected. However, in the interaction studies between antibodies and proteins, as well as in the immobilization of DNA and proteins, higher surface concentrations of interacting molecules led to a decrease (i.e. deviation from the linear trend) in the differential resistance to frequency ratio. This is interpreted as increased surface rigidity at higher surface concentrations of immobilized molecules. Consequently, studies that aim at obtaining biological binding information, such as avidity, from real-time resistance and dissipation data should be conducted at low surface concentrations. In addition, the differential resistance to frequency relationship was found to be highly dependent on the rigidity of the preceding layer(s) of immobilized molecules. This dependence can be utilized to obtain a higher signal-to-noise ratio for resistance measurement by using low surface densities of immobilized interaction partners.
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| 2. |
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| 3. |
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| 4. |
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| 5. |
- Bjurström, Johan, et al.
(författare)
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Synthesis of textured thin piezoelectric AlN films with a nonzero C-axis mean tilt for the fabrication of shear mode resonators
- 2006
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Ingår i: IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control. - 0885-3010 .- 1525-8955. ; 53:11, s. 2095-2100
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Tidskriftsartikel (refereegranskat)abstract
- A method for the deposition of thin piezoelectric aluminum nitride (AlN) films with a nonzero c-axis mean tilt has been developed. The deposition is done in a standard reactive magnetron sputter deposition system without any hardware modifications. In essence, the method consists of a two-stage deposition process. The resulting film has a distinct tilted texture with the mean tilt of the c-axis varying roughly in the interval 28 to 32 degrees over the radius of the wafer excluding a small exclusion zone at the center of the latter. The mean tilt angle distribution over the wafer has a circular symmetry. A membrane-type shear mode thickness-excited thin film bulk acoustic resonator together with a micro-fluidic transport system has been subsequently fabricated using the two stage AIN deposition as well as standard bulk micro machining of Si. The resonator consisted of a 2-mu m-thick AlN film with 200-nm-thick A1 top and bottom electrodes. The resonator was characterized with a network analyzer when operating in both air and water. The shear mode resonance frequency was about 1.6 GHz, the extracted device Q around 350, and the electromechanical coupling k(t)(2) 2% when the resonator was operated in air, whereas the latter two dropped down to 150 and 1.8%, respectively, when the resonator was operated in pure water.
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| 6. |
- Bjurström, Johan, et al.
(författare)
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Temperature compensation of liquid FBAR sensors
- 2007
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Ingår i: Journal of Micromechanics and Microengineering. - : IOP Publishing. - 0960-1317 .- 1361-6439. ; 17:3, s. 651-658
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Tidskriftsartikel (refereegranskat)abstract
- In this work we demonstrate a practically complete temperature compensation of the second harmonic shear mode in a composite Al/AlN/Al/SiO2 thin film bulk acoustic resonator (FBAR) in the temperature range 25 °C–95 °C. The main advantages of this mode are its higher Q value in liquids as well as its higher frequency and hence higher resolution for sensor applications. For comparative reasons the non-compensated fundamental shear mode is also included in these studies. Both modes have been characterized when operated both in air and in pure water. Properties such as Q value, electromechanical coupling, dissipation and sensitivity are studied. An almost complete temperature compensation of the second harmonic shear mode was observed for an oxide thickness of 1.22 µm for an FBAR consisting of 2 µm thick AlN and 200 nm thick Al electrodes. Thus, the measured temperature coefficient of frequency (TCF) in air for the non-compensated fundamental shear mode (1.25 GHz) varied between −31 and −36 ppm °C−1 over the above temperature range while that of the compensated second harmonic shear mode (1.32 GHz) varied between +2 ppm °C−1 and −2 ppm °C−1 over the same temperature interval. When operated in pure water the former type shows a Q value and coupling coefficient, k2t, around 180 and 2%, respectively, whereas for the second harmonic these are 230 and 1.4%, respectively.
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| 7. |
- Höglund, Carina, et al.
(författare)
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Wurtzite-structure Sc1-xAlxN solid solution films grown by reactive magnetron sputter epitaxy : structural characterization and first-principles calculations
- 2010
-
Ingår i: Journal of Applied Physics. - : American Institute of Physics. - 0021-8979 .- 1089-7550. ; 107:12, s. 123515-
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Tidskriftsartikel (refereegranskat)abstract
- AlN(0001) was alloyed with ScN with molar fractions up to ~22%, while retaining a singlecrystal wurtzite (w-) structure and with lattice parameters matching calculated values. Material synthesis was realized by magnetron sputter epitaxy of thin films starting from optimal conditions for the formation of w-AlN onto lattice-matched w-AlN seed layers on Al2O3(0001) and MgO(111) substrates. Films with ScN contents between 23% and ~50% exhibit phase separation into nanocrystalline ScN and AlN, while ScN-rich growth conditions yield a transformation to rocksalt-structure Sc1-xAlxN(111) films. The experimental results are analyzed with ion beam analysis, X-ray diffraction, and transmission electron microscopy, together with ab-initio calculations of mixing enthalpies and lattice parameters of solid solutions in wurtzite, rocksalt, and layered hexagonal phases.
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| 8. |
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| 9. |
- Kerdsongpanya, Sit, et al.
(författare)
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Anomalously high thermoelectric power factor in epitaxial ScN thin films
- 2011
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Ingår i: Applied Physics Letters. - : American Institute of Physics (AIP). - 0003-6951 .- 1077-3118. ; 99:23, s. 232113-
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Tidskriftsartikel (refereegranskat)abstract
- Thermoelectric properties of ScN thin films grown by reactive magnetron sputtering on Al2O3(0001) wafers are reported. X-ray diffraction and elastic recoil detection analyses show that the composition of the films is close to stoichiometry with trace amounts (similar to 1 at. % in total) of C, O, and F. We found that the ScN thin-film exhibits a rather low electrical resistivity of similar to 2.94 mu Omega m, while its Seebeck coefficient is approximately similar to-86 mu V/K at 800 K, yielding a power factor of similar to 2.5 x 10(-3) W/mK(2). This value is anomalously high for common transition-metal nitrides.
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| 10. |
- Kerdsongpanya, Sit, 1985-
(författare)
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Design of Transition-Metal Nitride Thin Films for Thermoelectrics
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Thermoelectric devices are one of the promising energy harvesting technologies, because of their ability to convert heat (temperature gradient) to electricity by the Seebeck effect. Furthermore, thermoelectric devices can be used for cooling or heating by the inverse effect (Peltier effect). Since this conversion process is clean, with no emission of greenhouse gases during the process, this technology is attractive for recovering waste heat in automobiles or industries into usable electricity. However, the conversion efficiency of such devices is rather low due to fundamental materials limitations manifested through the thermoelectric figure of merit (ZT). Thus, there is high demand on finding materials with high ZT or strategies to improve ZT of materials.In this thesis, I discuss the basics of thermoelectrics and how to improve ZT of materials, including present-day strategies. Based on these ideas, I propose a new class of materials for thermoelectric applications: transition-metal nitrides, mainly ScN, CrN and their solid solutions. Here, I employed both experimental and theoretical methods to synthesize and study their thermoelectric properties. My study envisages ways for improving the thermoelectric figure of merit of ScN and possible new materials for thermoelectric applications.The results of my studies show that ScN is a promising thermoelectric material since it exhibits high thermoelectric power factor 2.5x10-3 Wm-1K-2 at 800 K, due to low metallic-like electrical resistivity while retained relatively large Seebeck coefficient. My studies on thermal conductivity of ScN also suggest a possibility to control thermal conductivity by tailoring the microstructure of ScN thin films. Furthermore, my theoretical studies on effects of impurities and stoichiometry on the electronic structure of ScN suggest the possibly to improve ScN ZT by stoichiometry tuning and doping. For CrN and Cr1-xScxN solid solution thin films, the results show that the power factor of CrN (8x10-4 Wm-1K-2 at 770 K) can be retained for the solid solution Cr0.92Sc0.08N. Finally, density functional theory was used to enable a systematic predictionbased strategy for optimizing ScN thermoelectric properties via phase stability of solid solutions. Sc1-xGdxN and Sc1-xLuxN are stabilized as disordered solid solutions, while in the Sc-Nb-N and Sc-Ta-N systems, the inherently layered ternary structures ScNbN2 and ScTaN2 are stable.
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| 11. |
- Kerdsongpanya, Sit
(författare)
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Scandium Nitride Thin Films for Thermoelectrics
- 2012
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Thermoelectric devices are one of the promising energy harvesting technologies, since they can convert heat (i.e. a temperature gradient) to electricity. This result leads us to use them to harvest waste heat from heat engines or in power plants to generate usable electricity. Moreover, thermoelectric devices can also perform cooling. The conversion process is clean, with no emission of greenhouse gases during the process. However, the converting efficiency of thermoelectrics is very low because of the materials limitations of the thermoelectric figure of merit (ZTm). Thus, there is high demand to maximize the ZTm.I have discovered that ScN has high power factor 2.5 mW/(mK2) at 800 K, due to low metalliclike electrical resistivity (∼3.0 μΩm) with retained relatively large Seebeck coefficient of -86 μV/K. The ScN thin films were grown by reactive dc magnetron sputtering from Sc targets. For ScN, X-ray diffraction, supported by transmission electron microscopy, show that we can obtain epitaxial ScN(111) on Al2O3(0001). We also reported effects on thermoelectric properties of ScN with small changes in the composition with the power factor changing one order of magnitude depending on e.g. oxygen, carbon and fluorine content which were determined by elastic recoil detection analysis. The presence of impurities may influence the electronic density of states or Fermi level (EF) which could yield enhancement of power factor.Therefore, the effects of defects and impurities on the electronic density of states of scandium nitride were investigated using first-principles calculations with general gradient approximation and hybrid functionals for the exchange correlation energy. Our results show that for Sc and N vacancies can introduce asymmetric peaks in the density of states close to the Fermi level. We also find that the N vacancy states are sensitive to total electron concentration of the system due to their possibility for spin polarization. Substitutional point defects shift the Fermi level in the electronic band according to their valence but do not introduce sharp features. The energetics and electronic structure of defect pairs are also studied. By using hybrid functionals, a correct description of the open band gap of scandium nitride is obtained, in contrast to regular general gradient approximation. Our results envisage ways for improving the thermoelectric figure of merit of ScN by electronic structure engineering through stoichiometry tuning and doping.
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| 12. |
- Kubart, Tomas, et al.
(författare)
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A model of DC reactive magnetron sputtering for graded solar thermal absorbers
- 2008
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Ingår i: Journal of Physics, Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 100:8, s. 082024-
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Tidskriftsartikel (refereegranskat)abstract
- In this work we present process modelling of reactive in-line sputtering. Although modelling of reactive sputtering is often used, most models are based on assumptions which make them insufficient for use in this case. The presented model takes into account a realistic deposition rate profile and distribution of reactive gas pressure. The model has been applied to reactive sputter deposition of graded solar thermal absorbers. It has been shown that the presented model represents a simple alternative to complex Monte Carlo simulations while still representing all important features of the process.
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| 13. |
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| 14. |
- Nakagomi, Shinji, et al.
(författare)
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Hydrogen sensing by NKN thin film with high dielectric constant and ferroelectric property
- 2005
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Ingår i: Sensors and actuators. B, Chemical. - : Elsevier BV. - 0925-4005 .- 1873-3077. ; 108:1-2, s. 490-495
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Tidskriftsartikel (refereegranskat)abstract
- Hydrogen sensing properties of sodium potassium niobate NaxKyNbOz (NKN) thin films were studied. The NKN thin films were prepared by reactive rf magnetron sputtering. NKN is a ferroelectric material with high dielectric constant. The polarization increases in hydrogen ambient and decreases in oxygen ambient. The conductivity of the NKN film in hydrogen ambient is higher than in oxygen ambient, and these changes are reversible. The threshold voltage of the current–voltage (I–V) characteristics depends on the hydrogen concentration, and a large response of 3.3 V was obtained.
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| 15. |
- Tasnadi, Ferenc, et al.
(författare)
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Origin of the Anomalous Piezoelectric Response in Wurtzite ScxAl1-xN Alloys
- 2010
-
Ingår i: Physical Review Letters. - : American Physical Society. - 0031-9007 .- 1079-7114. ; 104:13, s. 137601-
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Tidskriftsartikel (refereegranskat)abstract
- The origin of the anomalous, 400% increase of the piezoelectric coefficient in ScxAl1-xN alloys is revealed. Quantum mechanical calculations show that the effect is intrinsic. It comes from a strong change in the response of the internal atomic coordinates to strain and pronounced softening of C-33 elastic constant. The underlying mechanism is the flattening of the energy landscape due to a competition between the parent wurtzite and the so far experimentally unknown hexagonal phases of the alloy. Our observation provides a route for the design of materials with high piezoelectric response.
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| 16. |
- Wingbrandt, H, et al.
(författare)
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New Materials for chemical and biosensors
- 2004
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Ingår i: International Symposium on Advanced Materials and Processing, ISAMAP2K4, 6-8 December, I.I. T., Kharagpur, India.
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)
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| 17. |
- Wingqvist, Gunilla
(författare)
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AlN-based sputter-deposited shear mode thin film bulk acoustic resonator (FBAR) for biosensor applications - A review
- 2010
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Ingår i: SURFACE and COATINGS TECHNOLOGY. - : Elsevier Science B.V., Amsterdam.. - 0257-8972. ; 205:5, s. 1279-1286
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Tidskriftsartikel (refereegranskat)abstract
- A new type of biosensor device is here presented which is fabricated using the same processes used for the fabrication of integrated electrical circuits to enable tighter integration and further sensor/biosensor miniaturization. The device is a so-called thin film bulk acoustic resonator (FBAR) operating in shear mode. Here specifically AlN-based shear mode FBAR is addressed but also an overview of the shear mode FBAR development in general is presented. Developments are reported of a low temperature reactive sputtering process for growing wurtzite-AlN thin films with a close to homogenous c-axis inclination over a 4 substrate wafer. This process enabled fabrication of shear mode FBAR sensors. The sensor operation is described along with how the design parameters influence its performance. Specifically, sensitivity amplification utilizing low acoustic impedance layers in the FBAR structure is demonstrated and explained. The resolution of the AlN shear mode FBAR sensor is demonstrated to already be comparable with the conventional quartz crystal microbalance (QCM) sensor, suggesting that shear mode FBAR may be a competitive and low cost alternative to QCM.
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| 18. |
- Wingqvist, Gunilla, et al.
(författare)
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Immunosensor utilizing a shear mode thin film bulk acoustic sensor
- 2007
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Ingår i: Sensors and actuators. B, Chemical. - : Elsevier BV. - 0925-4005 .- 1873-3077. ; 127:1, s. 248-252
-
Tidskriftsartikel (refereegranskat)abstract
- An AlN thin film electro-acoustic resonator has been fabricated employing a reactive sputtering process for the deposition of an AlN thin film with inclined c-axis for excitation of the shear mode for operation in liquid media. The main objective is to investigate the efficiency of the micro-fluidic channel system integrated in the silicon wafer underneath the AlN resonator. A comparative study between the shear mode thin film bulk acoustic resonator (FBAR) and a quartz crystal microbalance (QCM) using a competitive antibody–antigen association process for detection of drug molecules is presented.
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| 19. |
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| 20. |
- Wingqvist, Gunilla, et al.
(författare)
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Increased electromechanical coupling in w-ScxAl1-xN
- 2010
-
Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 97:11, s. 112902-
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Tidskriftsartikel (refereegranskat)abstract
- AlN is challenged as the material choice in important thin film electroacoustic devices for modern wireless communication applications. We present the promise of superior electromechanical coupling (kt2), in w−ScxAl1−xN by studying its dielectric properties. w−ScxAl1−xN (0≤x≤0.3) thin films grown by dual reactive magnetron sputtering exhibited low dielectric losses along with minor increased dielectric constant (ε). Ellipsometry measurements of the high frequency ε showed good agreement with density function perturbation calculations. Our data show that kt2 will improve from 7% to 10% by alloying AlN with up to 20 mol % ScN.
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| 21. |
- Wingqvist, Gunilla, et al.
(författare)
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Mass sensitivity of multilayer thin film resonant BAW sensors
- 2008
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Ingår i: Sensors and Actuators A-Physical. - : Elsevier BV. - 0924-4247 .- 1873-3069. ; 148:1, s. 88-95
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Tidskriftsartikel (refereegranskat)abstract
- Abstract: A systematic study of the mass sensitivity and its dependence on the material's properties and thicknesses in composite multilayer Thin Film Bulk Acoustic Resonators (FBAR) is presented. The Mason transmission line model has been employed in combination with the acoustic energy balance principle for the determination of the FBAR mass sensitivity. The results have been experimentally verified. Further, the mass sensitivity dependence on various parameters has been studied and correlated with wave reflection and interference within the composite structure in addition to the well-known dependence on resonator acoustic impedance and operation frequency. The mass sensitivity for both the fundamental and the second harmonic mode of operation has been studied in view of their practical relevance. In particular, sensitivity amplification induced by the presence of an on-top deposited low acoustic impedance layer has been identified for the first harmonic and its potential applicability discussed in terms of gas and in-liquid sensing. Optimized structures for both sensing applications are suggested by considering the overall sensor resolution defined by both the mass sensitivity and the FBAR performance.
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| 22. |
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| 23. |
- Wingqvist, Gunilla, et al.
(författare)
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Micromachined thermally compensated thin film Lamb wave resonator for frequency control and sensing applications
- 2009
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Ingår i: Journal of Micromechanics and Microengineering. - : IOP Publishing. - 0960-1317 .- 1361-6439. ; 19:3, s. 035018-
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Tidskriftsartikel (refereegranskat)abstract
- Micromachined thin film plate acoustic wave resonators (FPAR) utilizing the lowest order symmetric Lamb wave (S0) propagating in highly textured 2μm thick Aluminum Nitride (AlN) membranes have been successfully demonstrated [1]. The proposed devices have a SAW-based design and exhibit Q factors of up to 3000 at a frequency around 900MHz as well as design flexibility with respect to the required motional resistance. However, a notable drawback of the proposed devices is non-zero temperature coefficient of frequency (TCF) which lies in the range -20 ppm/K to –25 ppm/K. Thus, despite the promising features demonstrated, further device optimization is required. In this work temperature compensation of thin AlN film Lamb wave resonators is studied and experimentally demonstrated. Temperature compensation while retaining at the same time the device electromechanical coupling is experimentally demonstrated. The zero TCF Lamb wave resonators are fabricated onto composite AlN/SiO2 membranes. Q factors of around 1400 have been measured at a frequency of around 755 MHz. Finally, the impact of technological issues on the device performance is discussed in view of improving the device performance.
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| 24. |
- Wingqvist, Gunilla, et al.
(författare)
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On the applicability of high frequency acoustic shear mode biosensing in view of thickness limitations set by the film resonance
- 2009
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Ingår i: Biosensors & bioelectronics. - : Elsevier BV. - 0956-5663 .- 1873-4235. ; 24:11, s. 3387-3390
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Tidskriftsartikel (refereegranskat)abstract
- The IC-compatible thin film bulk acoustic resonator (FBAR) technology has made it possible to move the thickness excited shear mode sensing of biological layers into a new sensing regime using substantially higher operation frequencies than the conventionally used Quartz Crystal Microbalance (QCM). The limitations of the linear range set by the film resonance using viscoelastic protein films are here for the first time addressed specifically for FBARs operating at 700MHz up to 1.5GHz. Two types of protein multilayer sensing were employed; one utilizing alternating layers of Streptavidin and Biotinated BSA and the other using stepwise cross-linking of fibrinogen with EDC/NHS activation of its carboxyl groups. In both cases the number of protein layers within the linear regime is well above the number of protein layers usually used in biosensor applications, further verifying the applicability of the FBAR as a biosensor. Theoretical calculations are also presented using well established physical models to illustrate the expected behavior of the FBAR sensor, in view of both the frequency and the dissipation shifts.
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| 25. |
- Wingqvist, Gunilla, et al.
(författare)
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Shear mode AlN thin film electro-acoustic resonant sensor operation in viscous media
- 2007
-
Ingår i: Sensors and actuators. B, Chemical. - : Elsevier BV. - 0925-4005 .- 1873-3077. ; 123:1, s. 466-473
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Tidskriftsartikel (refereegranskat)abstract
- A shear mode thin film bulk acoustic resonator (FBAR) operating in liquid media together with a microfluidic transport system is presented. The resonator has been fabricated utilizing a recently developed reactive sputter-deposition process for AlN thin films with inclined c-axis relative to the surface normal with a mean tilt of around 30°. The resonator has a resonance frequency of around 1.2 GHz and a Q value in water of around 150. Sensor operation in water and glycerol solutions is characterized. Theoretical analysis of the sensor operation under viscous load as well as of the sensitivity and stability in general is presented. The theoretical predictions are compared with experimental measurements. The results demonstrate clearly the potential of FBAR biosensors for the fabrication of highly sensitive low cost biosensors, bioanalytical tools as well as for liquid sensing in general.
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| 26. |
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| 27. |
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| 28. |
- Wingqvist,, Gunilla, et al.
(författare)
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Temperature Compensation of Thin Film Resonators utilizing the Lowest order Symmetric Lamb mode
- 2008
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Micromachined Thin film plate acoustic wave resonators (FPAR) utilizing the lowest order symmetric Lamb wave (S0) propagating in highly textured 2μm thick Aluminum Nitride (AlN) membranes have been successfully demonstrated[1]. However, a notable drawback of the proposed devices is their non-zero temperature coefficient of frequency (TCF) which lies in the range -20 ppm/K to –25 ppm/K. In this work temperature compensation of thin AlN film Lamb wave resonators is studied and demonstrated. Temperature compensation, while retaining at the same time the device electromechanical coupling, isexperimentally demonstrated. The zero TCF Lamb wave resonators are fabricated onto composite AlN/SiO2 membranes. Q factors of around 1400 have been measured at a frequency of around 755 MHz.
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| 29. |
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| 30. |
- Wingqvist, Gunilla
(författare)
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Thin-film electro-acoustic sensors based on AlN and its alloys: possibilities and limitations
- 2012
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Ingår i: Microsystem Technologies. - : Springer Verlag (Germany). - 0946-7076 .- 1432-1858. ; 18:7-8, s. 1213-1223
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Tidskriftsartikel (refereegranskat)abstract
- Sputter deposited aluminum nitride (AlN) thin films have played a central role for the successful development of the thin film electro-acoustic technology. The development has been primarily driven by one device-the thin film bulk acoustic resonator, with its primary use for high frequency filter applications for the telecom industry. Recently, increased piezoelectric properties in AlN through the alloying with scandium nitride have been identified both experimentally and theoretically. This opens up new possibilities for the thin film electro-acoustic technology. Here expectations and discussions are presented on acoustic FBAR sensor performance when based on AlN as well as on such AlN alloys to identify possible benefits and limitations. Inhere, the distinction is made between direct and in-direct (acoustic) use of the piezoelectric effect for sensor applications. These two approaches are described and compared in view of their advantages and possibilities. Especially, the indirect (or acoustic) use is identified as interesting for its versatility and good exploitation of the thin film technology to obtain highly sensitive sensor transducers. It is pointed out that the indirect approach can well be obtained internally in the piezoelectric material structure. Original calculations are presented to support the discussion.
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| 31. |
- Wingqvist, Gunilla
(författare)
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Thin Film Electroacoustic Devices for Biosensor Applications
- 2009
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Biosensors are today important devices within various application areas. In this thesis a new type of label-free biosensor device is studied, which is fabricated using the same processes used for the fabrication of integrated circuits. This enables tighter integration and further sensors/biosensor miniaturization. The device is a so-called Thin Film Bulk Acoustic Resonator (FBAR). Within this thesis a low temperature reactive sputtering process for growing AlN thin films with a c-axis inclination of 20-30o has been developed. This enables shear mode FBAR fabrication suitable for in-liquid operation, essential for biosensor applications. Shear mode FBARs were fabricated operating at frequencies above 1GHz exhibiting Q values of 100-200 in water and electromechanical coupling factors kt2 of about 1.8%. This made it possible to move the thickness excited shear mode sensing of biological layers into a new sensing regime using substantially higher operation frequencies than the conventionally used quartz crystal microbalance (QCM) operating at 5-20MHz. Measured noise levels of shear mode FBARs in contact with water showed the resolution to be in the range 0.3ng/cm2 to 7.5ng/cm2. This demonstrated the FBAR resolution without any averaging or additional stabilization measures already to be in the same range as the conventional QCM (5ng/cm2), suggesting that FBARs may be a competitive and low cost alternative to QCM. The linear thickness limit for sensing of biomolecular layers was concluded to be larger than the thickness of the majority of the molecular systems envisaged for FBAR biosensor applications. A temperature compensated shear mode FBAR composite structure was demonstrated with retained coupling factor and Q-value by utilizing the second mode of operation. Understanding has been gained on the sensor operation as well as on how the design parameters influence its performance. Specifically, sensitivity amplification utilizing low acoustic impedance layers in the FBAR structure has been demonstrated and explained. Further, temperature compensated Lamb mode (FPAR) devices were also studied and demonstrated with optimized electromechanical couplings.
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| 32. |
- Wingqvist, Gunilla Ölund, 1966, et al.
(författare)
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Governance Bottlenecks and Policy Options for Sustainable Materials Management - A Discussion paper
- 2013
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Growing volumes and complexities of material flows pose serious risks to human health and ecosystems during different stages of the materials’ life-cycle. The gradual shift of base for manufacturing and chemical industries to developing countries has contributed to growth and employment but also lead to serious pollution of water, air and soil. Poor people tend to be most adversely affected by pollution and the health impacts from water and air pollution or dumping of hazardous waste is often dramatic. Managing mounting waste streams is currently one of the biggest challenges for rapidly growing urban centers in developing countries. Poor waste collection and dumping of waste in water bodies and uncontrolled dump sites is a major sanitation problem. Waste management is also an issue of global concern since the decay of organic material in post consumer solid waste contributes to about 5 percent of global greenhouse gas emissions. The growing flow of materials also includes a growing flow of chemicals in different products making waste streams more complex. It is increasingly recognized that a technical focus on end-of-pipe solutions is not sufficient to address these problems. A shift towards more upstream approaches that can assure cleaner and more resource efficient materials flows is necessary. The traditional focus on technical solutions needs to be combined with strengthening institutions and governance systems since the way national and local authorities govern, regulate and control material flows have profound impacts on human health, environmental sustainability and economic growth. Policy design for sustainable materials management is embedded in a political context with multiple actors and interests. In many cases, measures that strengthen important human rights principles such as the rule of law, transparency and public participation may be equally or more important than specific environmental policies or projects in order to improve materials management. The purpose of this paper is to describe how and in what way governance matters to achieve a sustainable materials management that contributes positively to development. The paper introduces key concepts, and discusses key governance mechanisms to achieve a more sustainable materials management in a developing country context.
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| 33. |
- Wingqvist, Gunilla Ölund, 1966, et al.
(författare)
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The Role of Governance for Improved Environmental Outcomes
- 2012
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Climate change and escalating environmental degradation is becoming key constraints to a sustainable development. Managing the environmental challenges is important for the well-being of all citizens, particularly for the least well-off. There has been some progress in terms of policies and creation of environmental authorities and international environmental commitments. There is however, a growing gap between the commitments made and the actual implementation to improve environmental outcomes. It is increasingly recognised that technical solutions to environmental problems are not sufficient to obtain sustainable development. Measures that strengthen important human rights principles such as the rule of law, transparency and public participation may be equally or more important than specific environmental policies or projects in order to improve environmental outcomes. The purpose of the report is to explore the linkages between governance and the implementation of environmental legislation (including multilateral environmental agreements) and other environmental measures. The report is intended as a source of information and inspiration to individuals and organisations working with environment and development.
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| 34. |
- Žukauskaitė, Agnė, et al.
(författare)
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Microstructure and Dielectric Properties of Piezoelectric Magnetron Sputtered w-ScxAl1-xN thin films
- 2012
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Ingår i: Journal of Applied Physics. - : American Institute of Physics (AIP). - 0021-8979 .- 1089-7550. ; 111:9, s. 093527-
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Tidskriftsartikel (refereegranskat)abstract
- Piezoelectric wurtzite ScxAl1-xN (x=0, 0.1, 0.2, 0.3) thin films were epitaxially grown by reactive magnetron co-sputtering from elemental Sc and Al targets. Al2O3(0001) wafers with TiN(111) seed and electrode layers were used as substrates. X-ray diffraction shows that an increase in the Sc content results in the degradation of the crystalline quality. Samples grown at 400 °C possess true dielectric behavior with quite low dielectric losses and the leakage current is negligible. For ScAlN samples grown at 800 °C, the crystal structure is poor and leakage current is high. Transmission electron microscopy with energy dispersive x-ray spectroscopy mapping shows a mass separation into ScN-rich and AlN-rich domains for x≥0.2 when substrate temperature is increased from 400 to 800 °C. The piezoelectric response of epitaxial ScxAl1-xN films measured by piezoresponse force microscopy and double beam interferometry shows up to 180% increase by the addition of Sc up to x=0.2 independent of substrate temperature, in good agreement with previous theoretical predictions based on density-functional theory.
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