This work presents a novel fully passive monolithic microwave multisensor on Substrate Integrated... more This work presents a novel fully passive monolithic microwave multisensor on Substrate Integrated Waveguide (SIW) technology for simultaneous detection of humidity and temperature. The proposed structure is simple and combines several resonators with well controlled coupling. Each resonator of the multisensor is capable of environmental detection. The detection principle is based on a frequency shift due to a perturbation of the effective permittivity, depending on the sensitivity of the dielectric medium to the surrounding physical variable. The presented multisensor structure operates in the frequency range from 5–9.5 GHz and exhibits a frequency shift for relative humidity in the range of 6.5–93%RH and for temperature between 23–60°C. Based on SIW technology, this new monolithic environmental solution presents the advantage of being easily integrated into planar structure, energetically efficient and low-cost for mass production application.
ABSTRACT This investigation presents the growth of (100), (110) and preferential (111)-oriented P... more ABSTRACT This investigation presents the growth of (100), (110) and preferential (111)-oriented Pb0.6Sr0.4TiO3 thin films prepared on different orientations LaNiO3 buffered silicon substrates via radio-frequency magnetron sputtering method. The effects of the orientation on microstructure and dielectric response were systematically investigated. The capacitance–voltage property versus the crystallographic orientation analysis revealed that preferential (111)-orientation film possesses the largest relative permittivity and tunability of 1180 and 84% (at 400 kV/cm) respectively, which are much higher than those of (100)- and (110)-oriented thin films. These results suggest preferential (111)-orientation films as promising candidates for microwave tunable devices.
Several technological challenges have prevented GaN‐based micro‐LEDs from finding application in ... more Several technological challenges have prevented GaN‐based micro‐LEDs from finding application in mass market displays, despite their unique properties such as very high brightness and the very fast response time of GaN‐based materials. The primary challenges are the cost and complexity of lift‐off and transfer of LEDs from sapphire substrates to suitable supports as well as the lowered performance of tiny micro‐LEDs caused by chemical etching that defines individual LEDs. Herein, this work reports demonstration of a complete process that solves these challenges with epitaxy and cleanroom technologies that are commercially available. The process begins with van der Waals epitaxy of 2D h‐BN on silica masks with square, triangular and hexagonal patterns on sapphire substrates which define the micro‐LED regions. Then selective area growth of MQW LED heterostructures, with ultra smooth crystalline sidewalls, down to ultra tiny size of 1.4 µm is performed. Because of the lack of vertical chemical bonds in the h‐BN layer, simple mechanical lift‐off and transfer is performed on an array of LEDs heterostructures down to size of 8 µm. Finally, transparent ITO p‐contacts are deposited on LEDs with uniform lift‐off, resulting in high brightness LEDs.
This work presents a novel fully passive monolithic microwave multisensor on Substrate Integrated... more This work presents a novel fully passive monolithic microwave multisensor on Substrate Integrated Waveguide (SIW) technology for simultaneous detection of humidity and temperature. The proposed structure is simple and combines several resonators with well controlled coupling. Each resonator of the multisensor is capable of environmental detection. The detection principle is based on a frequency shift due to a perturbation of the effective permittivity, depending on the sensitivity of the dielectric medium to the surrounding physical variable. The presented multisensor structure operates in the frequency range from 5–9.5 GHz and exhibits a frequency shift for relative humidity in the range of 6.5–93%RH and for temperature between 23–60°C. Based on SIW technology, this new monolithic environmental solution presents the advantage of being easily integrated into planar structure, energetically efficient and low-cost for mass production application.
2016 IEEE International Workshop on Electromagnetics: Applications and Student Innovation Competition (iWEM), 2016
This work describes a novel measurement technique for determining the complex permittivity of pow... more This work describes a novel measurement technique for determining the complex permittivity of powdered materials, based on resonant-perturbation of a Substrate Integrated Waveguide (SIW) resonator operating at ~2.5 GHz and calculations from General Dielectric Mixture Model equations. The proposed method is validated with standard powder samples measurement and comparison with the measured data by 3D electromagnetic simulation. The influence of the powder density is also discussed. The technique is then used to investigate the effect of hydrogen gas adsorption and humidity on the dielectric properties of tin oxide and zinc oxide powders, respectively. The SIW-resonator is a low cost and simple structure with good sensitivity. It is adapted for dielectric characterizations of both semi-solid and non-solid materials.
Gas sensors based on AlGaN/GaN high-electron-mobility transistors (HEMTs) with indium tin oxide (... more Gas sensors based on AlGaN/GaN high-electron-mobility transistors (HEMTs) with indium tin oxide (ITO) gates as functional layers were fabricated to detect hydrogen gas. Several sensing metrics such as the changes in current, sensitivity, and response time confirmed the dependence of the sensing response on the gas concentration.
Gas sensors based on AlGaN/GaN high-electron-mobility transistors (HEMTs) with indium tin oxide (... more Gas sensors based on AlGaN/GaN high-electron-mobility transistors (HEMTs) with indium tin oxide (ITO) gates as functional layers were fabricated to detect hydrogen gas. Several sensing metrics such as the changes in current, sensitivity, and response time confirmed the dependence of the sensing response on the gas concentration.
Abstract Using platinum (Pt) and LaNiO 3 (LNO) as both top and bottom electrodes, the investigati... more Abstract Using platinum (Pt) and LaNiO 3 (LNO) as both top and bottom electrodes, the investigation of their effect on structural, dielectric, ferroelectric and piezoelectric properties of PbZr 0.54 Ti 0.46 O 3 thin films with different thicknesses (200, 400, 600 and 800 nm) was made. Four different structures (Pt/PZT/Pt, LNO/PZT/LNO, Pt/PZT/LNO and LNO/PZT/Pt) were processed on silicon substrate for comparison. So a total of 16 structures available. X-ray diffraction (XRD) analyses revealed that the use of Pt or LNO as bottom electrode changes the PZT crystallographic orientation. Dielectric measurements showed that for the films grown on either Pt or LNO electrodes, lower values of ɛ r were always obtained when Pt was used as top electrode in comparison of LNO for which ɛ r reached maximum value. The crystallographic orientation of the bottom electrode also was found to influence the dielectric constant of the film. Concerning the ferroelectric properties it was observed that, for a given bottom electrode, the use of LNO as top electrode systematically reduces both positive and negative coercive fields, when compared with top Pt electrode. On the other hand, for a given top electrode, utilization of LNO as bottom electrode still leads to the lowering of coercive field values when compared to Pt bottom electrode, however in smaller proportions with respect to what was observed when substituting Pt by LNO as top electrode. Moreover it was observed that the thickness dependence of the coercive fields almost vanished each time, and only when, LNO was used as top electrode. The piezoelectric response, measured thanks to laser doppler vibrometer, is increased when LNO is used as the top electrode, in proportions depending to the film thickness.
The problem of thickness dependence of dielectric and ferroelectric properties of Pb(Zr0.54Ti0.46... more The problem of thickness dependence of dielectric and ferroelectric properties of Pb(Zr0.54Ti0.46)O3 (PZT) thin film capacitors is addressed. Experimental data collected on PZT capacitors with different thicknesses and different electrode configurations, using platinum and LaNiO3 conducting oxide, are examined within the prism of existing models. Available literature data, abounding but contradictory, led us to conclude that in the range of thickness investigated, size effect under all its aspects, i.e., increase in coercive field (Ec) as well as decrease in both dielectric permittivity and remnant polarization (Pr), result basically from existence of a depolarization field. It is shown however that the latter arises from interface chemistry, mostly related to the upper surface of the films, instead of finite screening length in the electrodes unlike commonly accepted. Moreover it is established that increase in Ec and decrease in Pr are not concomitant, and significant degradation of one or the other of ...
This work presents a novel fully passive monolithic microwave multisensor on Substrate Integrated... more This work presents a novel fully passive monolithic microwave multisensor on Substrate Integrated Waveguide (SIW) technology for simultaneous detection of humidity and temperature. The proposed structure is simple and combines several resonators with well controlled coupling. Each resonator of the multisensor is capable of environmental detection. The detection principle is based on a frequency shift due to a perturbation of the effective permittivity, depending on the sensitivity of the dielectric medium to the surrounding physical variable. The presented multisensor structure operates in the frequency range from 5–9.5 GHz and exhibits a frequency shift for relative humidity in the range of 6.5–93%RH and for temperature between 23–60°C. Based on SIW technology, this new monolithic environmental solution presents the advantage of being easily integrated into planar structure, energetically efficient and low-cost for mass production application.
ABSTRACT This investigation presents the growth of (100), (110) and preferential (111)-oriented P... more ABSTRACT This investigation presents the growth of (100), (110) and preferential (111)-oriented Pb0.6Sr0.4TiO3 thin films prepared on different orientations LaNiO3 buffered silicon substrates via radio-frequency magnetron sputtering method. The effects of the orientation on microstructure and dielectric response were systematically investigated. The capacitance–voltage property versus the crystallographic orientation analysis revealed that preferential (111)-orientation film possesses the largest relative permittivity and tunability of 1180 and 84% (at 400 kV/cm) respectively, which are much higher than those of (100)- and (110)-oriented thin films. These results suggest preferential (111)-orientation films as promising candidates for microwave tunable devices.
Several technological challenges have prevented GaN‐based micro‐LEDs from finding application in ... more Several technological challenges have prevented GaN‐based micro‐LEDs from finding application in mass market displays, despite their unique properties such as very high brightness and the very fast response time of GaN‐based materials. The primary challenges are the cost and complexity of lift‐off and transfer of LEDs from sapphire substrates to suitable supports as well as the lowered performance of tiny micro‐LEDs caused by chemical etching that defines individual LEDs. Herein, this work reports demonstration of a complete process that solves these challenges with epitaxy and cleanroom technologies that are commercially available. The process begins with van der Waals epitaxy of 2D h‐BN on silica masks with square, triangular and hexagonal patterns on sapphire substrates which define the micro‐LED regions. Then selective area growth of MQW LED heterostructures, with ultra smooth crystalline sidewalls, down to ultra tiny size of 1.4 µm is performed. Because of the lack of vertical chemical bonds in the h‐BN layer, simple mechanical lift‐off and transfer is performed on an array of LEDs heterostructures down to size of 8 µm. Finally, transparent ITO p‐contacts are deposited on LEDs with uniform lift‐off, resulting in high brightness LEDs.
This work presents a novel fully passive monolithic microwave multisensor on Substrate Integrated... more This work presents a novel fully passive monolithic microwave multisensor on Substrate Integrated Waveguide (SIW) technology for simultaneous detection of humidity and temperature. The proposed structure is simple and combines several resonators with well controlled coupling. Each resonator of the multisensor is capable of environmental detection. The detection principle is based on a frequency shift due to a perturbation of the effective permittivity, depending on the sensitivity of the dielectric medium to the surrounding physical variable. The presented multisensor structure operates in the frequency range from 5–9.5 GHz and exhibits a frequency shift for relative humidity in the range of 6.5–93%RH and for temperature between 23–60°C. Based on SIW technology, this new monolithic environmental solution presents the advantage of being easily integrated into planar structure, energetically efficient and low-cost for mass production application.
2016 IEEE International Workshop on Electromagnetics: Applications and Student Innovation Competition (iWEM), 2016
This work describes a novel measurement technique for determining the complex permittivity of pow... more This work describes a novel measurement technique for determining the complex permittivity of powdered materials, based on resonant-perturbation of a Substrate Integrated Waveguide (SIW) resonator operating at ~2.5 GHz and calculations from General Dielectric Mixture Model equations. The proposed method is validated with standard powder samples measurement and comparison with the measured data by 3D electromagnetic simulation. The influence of the powder density is also discussed. The technique is then used to investigate the effect of hydrogen gas adsorption and humidity on the dielectric properties of tin oxide and zinc oxide powders, respectively. The SIW-resonator is a low cost and simple structure with good sensitivity. It is adapted for dielectric characterizations of both semi-solid and non-solid materials.
Gas sensors based on AlGaN/GaN high-electron-mobility transistors (HEMTs) with indium tin oxide (... more Gas sensors based on AlGaN/GaN high-electron-mobility transistors (HEMTs) with indium tin oxide (ITO) gates as functional layers were fabricated to detect hydrogen gas. Several sensing metrics such as the changes in current, sensitivity, and response time confirmed the dependence of the sensing response on the gas concentration.
Gas sensors based on AlGaN/GaN high-electron-mobility transistors (HEMTs) with indium tin oxide (... more Gas sensors based on AlGaN/GaN high-electron-mobility transistors (HEMTs) with indium tin oxide (ITO) gates as functional layers were fabricated to detect hydrogen gas. Several sensing metrics such as the changes in current, sensitivity, and response time confirmed the dependence of the sensing response on the gas concentration.
Abstract Using platinum (Pt) and LaNiO 3 (LNO) as both top and bottom electrodes, the investigati... more Abstract Using platinum (Pt) and LaNiO 3 (LNO) as both top and bottom electrodes, the investigation of their effect on structural, dielectric, ferroelectric and piezoelectric properties of PbZr 0.54 Ti 0.46 O 3 thin films with different thicknesses (200, 400, 600 and 800 nm) was made. Four different structures (Pt/PZT/Pt, LNO/PZT/LNO, Pt/PZT/LNO and LNO/PZT/Pt) were processed on silicon substrate for comparison. So a total of 16 structures available. X-ray diffraction (XRD) analyses revealed that the use of Pt or LNO as bottom electrode changes the PZT crystallographic orientation. Dielectric measurements showed that for the films grown on either Pt or LNO electrodes, lower values of ɛ r were always obtained when Pt was used as top electrode in comparison of LNO for which ɛ r reached maximum value. The crystallographic orientation of the bottom electrode also was found to influence the dielectric constant of the film. Concerning the ferroelectric properties it was observed that, for a given bottom electrode, the use of LNO as top electrode systematically reduces both positive and negative coercive fields, when compared with top Pt electrode. On the other hand, for a given top electrode, utilization of LNO as bottom electrode still leads to the lowering of coercive field values when compared to Pt bottom electrode, however in smaller proportions with respect to what was observed when substituting Pt by LNO as top electrode. Moreover it was observed that the thickness dependence of the coercive fields almost vanished each time, and only when, LNO was used as top electrode. The piezoelectric response, measured thanks to laser doppler vibrometer, is increased when LNO is used as the top electrode, in proportions depending to the film thickness.
The problem of thickness dependence of dielectric and ferroelectric properties of Pb(Zr0.54Ti0.46... more The problem of thickness dependence of dielectric and ferroelectric properties of Pb(Zr0.54Ti0.46)O3 (PZT) thin film capacitors is addressed. Experimental data collected on PZT capacitors with different thicknesses and different electrode configurations, using platinum and LaNiO3 conducting oxide, are examined within the prism of existing models. Available literature data, abounding but contradictory, led us to conclude that in the range of thickness investigated, size effect under all its aspects, i.e., increase in coercive field (Ec) as well as decrease in both dielectric permittivity and remnant polarization (Pr), result basically from existence of a depolarization field. It is shown however that the latter arises from interface chemistry, mostly related to the upper surface of the films, instead of finite screening length in the electrodes unlike commonly accepted. Moreover it is established that increase in Ec and decrease in Pr are not concomitant, and significant degradation of one or the other of ...
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Papers by Yves Sama