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| 2. |
- Moreira, Milena De Albuquerque, et al.
(författare)
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Synthesis and characterization of highly c-textured Al(1-x)Sc(x)N thin films in view of telecom applications
- 2012
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Ingår i: More than moore. ; , s. 012014-
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Konferensbidrag (refereegranskat)abstract
- Wurtzite AlN is a piezoelectric material with excellent electro-acoustic properties and is used for the fabrication of high frequency thin film micro-acoustic components, most notably filters, duplexers, resonators, etc. Its moderate electromechanical coupling coefficient (k(t)(2)) of 6%-7% is insufficient for applications requiring larger bandwidths. Recent theoretical and experimental studies indicate that AlN alloyed with Sc exhibits a substantially higher piezoelectric constant than pure AlN. This study aims at determining the main electro-acoustic parameters of Al(1-x)Sc-(x) N in view of large bandwidth applications. To this end, highly c-textured Al(1-x)Sc(x) N thin films have been synthesized with relative Sc concentrations of up to 0,15. Subsequently, FBAR resonators were fabricated and characterized as a function of the Sc content. It is seen that k(t)(2) increases linearly with the latter to a value of 12% for a Sc concentration of x=0,15, while the Q value decreases from 739 to about 348 in the same concentration range. Likewise, the TCF varies from -35,9ppm/degrees C to -39,8ppm/degrees C, while the dielectric constant increases from epsilon=10 to a value of 14,1 for x=0,15. Finally, the relative dielectric losses are seen to increase by approximately a factor of two.
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| 3. |
- Moreira, Milena De Albuquerque, 1977-
(författare)
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Synthesis of Thin Piezoelectric AlN Films in View of Sensors and Telecom Applications
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The requirements of the consumer market on high frequency devices have been more and more demanding over the last decades. Thus, a continuing enhancement of the devices’ performance is required in order to meet these demands. In a macro view, changing the design of the device can result in an improvement of its performance. In a micro view, the physical properties of the device materials have a strong influence on its final performance. In the case of high frequency devices based on piezoelectric materials, a natural way to improve their performance is through the improvement of the properties of the piezoelectric layer. The piezoelectric material studied in this work is AlN, which is an outstanding material among other piezoelectric materials due to its unique combination of material properties.This thesis presents results from experimental studies on the synthesis of AlN thin films in view of telecom, microelectronic and sensor applications. The main objective of the thesis is to custom design the functional properties of AlN to best suit these for the specific application in mind. This is achieved through careful control of the crystallographic structure and texture as well as film composition.The piezoelectric properties of AlN films were enhanced by doping with Sc. Films with different Sc concentrations were fabricated and analyzed, and the coupling coefficient (kt2) was enhanced a factor of two by adding 15% of Sc to the AlN films. The enhancement of kt2 is of interest since it can contribute to a more relaxed design of high frequency devices. Further, in order to obtain better deposition control of c-axis tilted AlN films, a new experimental setup were proposed. When this novel setup was used, films with well-defined thicknesses and tilt uniformity were achieved. Films with such characteristics are very favorable to use in sensors based on electroacoustic devices operating in viscous media. Studies were also performed in order to obtain c-axis oriented AlN films deposited directly on Si substrates at reduced temperatures. The deposition technique used was HiPIMS, and the results indicated significant improvements in the film texture when comparing to the conventional Pulsed DC deposition process.
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| 4. |
- Raj, Pushparani, et al.
(författare)
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Fabrication and characterisation of a silicon-borosilicate glass microfluidic device for synchrotron-based hard X-ray spectroscopy studies
- 2021
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Ingår i: RSC Advances. - Cambridge : RSC Publishing. - 2046-2069. ; 11:47, s. 29859-29869
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Tidskriftsartikel (refereegranskat)abstract
- Some of the most fundamental chemical building blocks of life on Earth are the metal elements. X-ray absorption spectroscopy (XAS) is an element-specific technique that can analyse the local atomic and electronic structure of, for example, the active sites in catalysts and energy materials and allow the metal sites in biological samples to be identified and understood. A microfluidic device capable of withstanding the intense hard X-ray beams of a 4th generation synchrotron and harsh chemical sample conditions is presented in this work. The device is evaluated at the K-edges of iron and bromine and the L3-edge of lead, in both transmission and fluorescence mode detection and in a wide range of sample concentrations, as low as 0.001 M. The device is fabricated in silicon and glass with plasma etched microchannels defined in the silicon wafer before anodic bonding of the glass wafer into a complete device. The device is supported with a well-designed printed chip holder that made the microfluidic device portable and easy to handle. The chip holder plays a pivotal role in mounting the delicate microfluidic device on the beamline stage. Testing validated that the device was sufficiently robust to contain and flow through harsh acids and toxic samples. There was also no significant radiation damage to the device observed, despite focusing with intense X-ray beams for multiple hours. The quality of X-ray spectra collected is comparable to that from standard methods; hence we present a robust microfluidic device to analyse liquid samples using synchrotron XAS.
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