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Papers by Elisabete Galeazzo
2019 34th Symposium on Microelectronics Technology and Devices (SBMicro)
Gas sensors are usually made of metallic oxides and need to operate at relatively high temperatur... more Gas sensors are usually made of metallic oxides and need to operate at relatively high temperatures (about hundreds of Celsius degrees). Besides, they generally present drawbacks: low selectivity, elevated response time, and degradation. Novel nanostructured materials such as carbon nanotubes and graphene, among others, have been proposed to overcome these problems due to their unique electronic properties. However, these materials also present low selectivity for many gas species. In order to take advantage of the benefits of using carbon materials for gas sensing at room temperature, this work presents a proposal of humidity and volatile organic compounds (VOCs) sensing based on a miniaturized platform composed of four sensors. The lack of selectivity of individual materials is compensated by crossing the responses of each sensor. Results showed very fast response and recovery times (just few seconds), as well as good sensitivity (response variation up to four orders of magnitude). With this approach, the selectivity to discriminate the vapors can be improved, since each substance has an individual response pattern in the gas sensor array.
Recent works (1, 2) show the possibility of silicon (Si) micromachining using processes combinati... more Recent works (1, 2) show the possibility of silicon (Si) micromachining using processes combination that applies porous silicon (PS) as sacrificial layers previously masked by hydrogen ion implantation (H + I.I.) and rapid thermal annealing (RTA). With this new technology, it is possible to fabricate Si membranes with thickness of less than one micron. This work presents the result obtained by means of conventional thermal annealing (CTA) processes included after RTA, to control the thickness of Si with H + .I.I., as desired. As a result of CTA processes implementation, Si membranes with H + .I.I. layers from I to 4 microns of thickness were obtained, using adequate implantation dose.
Journal of Integrated Circuits and Systems, 2015
Intensive research has been focused on investigating new sensing materials, such as carbon nanotu... more Intensive research has been focused on investigating new sensing materials, such as carbon nanotubes (CNT) because of their promising characteristics. However, there are challenges related to their application in commercial devices such as sensitivity, compatibility, and complexity of miniaturization, among others. We report the study of the electrical behavior of devices composed by multi-walled carbon nanotubes (MWCNT) deposited between aluminum electrodes on glass substrates by means of dielectrophoresis (DEP), which is a simple and cost-effective method. The devices were fabricated by varying the DEP process time. Remarkable changes in their electric resistance were noticed depending on the MWCNT quantities deposited. Other electrical properties of devices such as high sensitivity, fast response time and stability are also characterized in humid environment. A humidity sensing mechanism is proposed on the basis of charge transfer between adsorbed water molecules and the MWNTC su...
Journal of Integrated Circuits and Systems, 2020
Nanostructured zinc oxide (ZnO) has attracted considerable interest for a wide range of applicati... more Nanostructured zinc oxide (ZnO) has attracted considerable interest for a wide range of applications, including its use as an active layer in gas sensor devices and as promising emitters for field emission devices. Although it is interesting for FE purposes, the synthesis of this material can be complex and non-compatible with microelectronic processes. To overcome this issue, this paper explores ZnO nanowires growth through thermal oxidation of zinc thin films. We applied this IC-compatible procedure to fabricate field emission cathodes. Analyses of Raman spectroscopy, X‑ray photoelectron spectrometry, X‑ray diffractometry and scanning electron microscopy confirmed that the processes applied were well succeeded in obtaining nanoscale structures of ZnO with dimensions up to 4 micrometers in length and 30‑100 nanometers in diameter. Electrical characterization showed an intense electron field emission on the active area of the device, with a low turn-on electric field (2.4 volts/micr...
Measurement, 2016
Field Emission devices (FE) have been proposed as efficient electron sources for several applicat... more Field Emission devices (FE) have been proposed as efficient electron sources for several applications such as electron microscopy and vacuum sensors, among others. Evidently, characterization methods applied during development phase of FE devices are crucial to evaluate aspects related with their working stability, homogeneity, and efficiency. However, the traditional methods provide only overall information about such characteristics, which difficult to improve the performance of these devices and their integration with electronics. To overcome this problem, this work presents an alternative system to characterize FE devices through electron emission imaging in real-time. The proposed system acquires I-V features of FE devices, while a video camera captures the emission image from a phosphor screen. Virtual instrumentation based on LabVIEW manages the whole system including measurement instruments, image capture, and data processing. As a result, histograms, 3D maps, and other FE analyses provide information about emitting characteristics of selected regions of interest. The main contribution of this work is to offer an important tool for the analyses of electron emission, by the association of captured images with the localized emission current. The extracted information from our system can efficiently support the characterization and the development of FE devices.
SPIE Proceedings, 1999
The aim of this work is to investigate the use of microchannels to concentrate pollutants present... more The aim of this work is to investigate the use of microchannels to concentrate pollutants present in the air. Devices with a length of 30 cm, a width of 100 micrometers and a depth of 30 micrometers , sealed by anodically bonded glass, were manufactured. Tests of adsorption characteristics were made using n-hexane. To reliably insert N2 contaminated with 1000
Sensors and Actuators B: Chemical, 2003
Hexamethyldissilazane (HMDS) plasma polymerized films can be used in a wide variety of applicatio... more Hexamethyldissilazane (HMDS) plasma polymerized films can be used in a wide variety of applications due to the facility on plasma polymerization of HMDS molecule and the high resistance to acid or basic corrosion of the formed film. Nonetheless, the hydrophobic character, as well as ...
Sensors and Actuators B: Chemical, 2003
This work made use of cleaner technologies and environmental friendly reagents to produce polar o... more This work made use of cleaner technologies and environmental friendly reagents to produce polar organic films with adsorption properties to be used as sensors in the environmental field. The films were obtained by plasma deposition of 2-propanol. The films were characterized by infrared and Raman spectroscopies, contact angle measurements with different aqueous solutions, optical and Atomic Force Microscopies (AFMs). The
In this work the results obtained to develop gas sensor built with porous silicon (PS) are presen... more In this work the results obtained to develop gas sensor built with porous silicon (PS) are presented, showing the influence of organic vapors such as acetone and ethanol on electrical characteristics of devices made of Al/PS/Si/Al. The sensitivity of the PS was characterized observing changes in capacitance as a function of frequency by means of devices geometrically scaled according to perimeter/area ratio. The relationship between each organic substance and the variation of impedance with frequency was obtained, verifying that the performance of devices is not shifted by the test conditions. The behavior of complex impedance is typical of a disordered material. Also, through FTIR measurements, there is no evidence of change of PS structure due to a direct adsorption of gases, showing that the passivation of PS devices is effective to block the action of chemical substances in interface states.
This work presents the results obtained for silicon microtips fabrication of pyramidal and conica... more This work presents the results obtained for silicon microtips fabrication of pyramidal and conical shape. The tips are prepared using processes combination that applies porous silicon (PS) as sacrificial layer previously masked by hydrogen ion implantation (H + I.I.) and adequate thermal annealing. The shape of the tips is dependent on the mask geometry used by blocking anodization current where PS is not desired. After selective dissolution of PS with potassium hydroxide (KOH) at room temperature, tips are formed with height of 45 μm and 2-5 μm top diameter in square geometry or less than 0. 1 micron with circular geometry.
2019 4th International Symposium on Instrumentation Systems, Circuits and Transducers (INSCIT), 2019
Real time in-situ characterization of electron emitters is fundamental to evaluate the efficiency... more Real time in-situ characterization of electron emitters is fundamental to evaluate the efficiency of field emission devices. We here present the potentialities of a new system for this purpose, since conventional electronic systems provide only an average of the total emission current of the device under test. Through the developed system, images generated in a phosphorescent anode are captured, processed and correlated with the emission current from the effective emitting centers of the cathode surface in real time. We discuss the advantages of applying the innovative features of the new system based on virtual instrumentation concept in contrast with the traditional methods of characterization. Finally, a case study demonstrates the functionalities of the new system. The results prove that our system is an innovative tool for extracting relevant parameters in field emission devices characterization.
Proceedings IMCS 2012, 2012
Field Emission (FE) devices were successfully improved by the association of silicon (Si) microti... more Field Emission (FE) devices were successfully improved by the association of silicon (Si) microtips and Multi-Walled Carbon Nanotubes (MWCNTs). MWCNTs were deposited over Si microtips by Electrophoretic Deposition (EPD), and improvements up to 80% in electron emission characteristics were reported, being suitable for the development of gas ionization sensors based on FE devices.
2019 34th Symposium on Microelectronics Technology and Devices (SBMicro)
Gas sensors are usually made of metallic oxides and need to operate at relatively high temperatur... more Gas sensors are usually made of metallic oxides and need to operate at relatively high temperatures (about hundreds of Celsius degrees). Besides, they generally present drawbacks: low selectivity, elevated response time, and degradation. Novel nanostructured materials such as carbon nanotubes and graphene, among others, have been proposed to overcome these problems due to their unique electronic properties. However, these materials also present low selectivity for many gas species. In order to take advantage of the benefits of using carbon materials for gas sensing at room temperature, this work presents a proposal of humidity and volatile organic compounds (VOCs) sensing based on a miniaturized platform composed of four sensors. The lack of selectivity of individual materials is compensated by crossing the responses of each sensor. Results showed very fast response and recovery times (just few seconds), as well as good sensitivity (response variation up to four orders of magnitude). With this approach, the selectivity to discriminate the vapors can be improved, since each substance has an individual response pattern in the gas sensor array.
Recent works (1, 2) show the possibility of silicon (Si) micromachining using processes combinati... more Recent works (1, 2) show the possibility of silicon (Si) micromachining using processes combination that applies porous silicon (PS) as sacrificial layers previously masked by hydrogen ion implantation (H + I.I.) and rapid thermal annealing (RTA). With this new technology, it is possible to fabricate Si membranes with thickness of less than one micron. This work presents the result obtained by means of conventional thermal annealing (CTA) processes included after RTA, to control the thickness of Si with H + .I.I., as desired. As a result of CTA processes implementation, Si membranes with H + .I.I. layers from I to 4 microns of thickness were obtained, using adequate implantation dose.
Journal of Integrated Circuits and Systems, 2015
Intensive research has been focused on investigating new sensing materials, such as carbon nanotu... more Intensive research has been focused on investigating new sensing materials, such as carbon nanotubes (CNT) because of their promising characteristics. However, there are challenges related to their application in commercial devices such as sensitivity, compatibility, and complexity of miniaturization, among others. We report the study of the electrical behavior of devices composed by multi-walled carbon nanotubes (MWCNT) deposited between aluminum electrodes on glass substrates by means of dielectrophoresis (DEP), which is a simple and cost-effective method. The devices were fabricated by varying the DEP process time. Remarkable changes in their electric resistance were noticed depending on the MWCNT quantities deposited. Other electrical properties of devices such as high sensitivity, fast response time and stability are also characterized in humid environment. A humidity sensing mechanism is proposed on the basis of charge transfer between adsorbed water molecules and the MWNTC su...
Journal of Integrated Circuits and Systems, 2020
Nanostructured zinc oxide (ZnO) has attracted considerable interest for a wide range of applicati... more Nanostructured zinc oxide (ZnO) has attracted considerable interest for a wide range of applications, including its use as an active layer in gas sensor devices and as promising emitters for field emission devices. Although it is interesting for FE purposes, the synthesis of this material can be complex and non-compatible with microelectronic processes. To overcome this issue, this paper explores ZnO nanowires growth through thermal oxidation of zinc thin films. We applied this IC-compatible procedure to fabricate field emission cathodes. Analyses of Raman spectroscopy, X‑ray photoelectron spectrometry, X‑ray diffractometry and scanning electron microscopy confirmed that the processes applied were well succeeded in obtaining nanoscale structures of ZnO with dimensions up to 4 micrometers in length and 30‑100 nanometers in diameter. Electrical characterization showed an intense electron field emission on the active area of the device, with a low turn-on electric field (2.4 volts/micr...
Measurement, 2016
Field Emission devices (FE) have been proposed as efficient electron sources for several applicat... more Field Emission devices (FE) have been proposed as efficient electron sources for several applications such as electron microscopy and vacuum sensors, among others. Evidently, characterization methods applied during development phase of FE devices are crucial to evaluate aspects related with their working stability, homogeneity, and efficiency. However, the traditional methods provide only overall information about such characteristics, which difficult to improve the performance of these devices and their integration with electronics. To overcome this problem, this work presents an alternative system to characterize FE devices through electron emission imaging in real-time. The proposed system acquires I-V features of FE devices, while a video camera captures the emission image from a phosphor screen. Virtual instrumentation based on LabVIEW manages the whole system including measurement instruments, image capture, and data processing. As a result, histograms, 3D maps, and other FE analyses provide information about emitting characteristics of selected regions of interest. The main contribution of this work is to offer an important tool for the analyses of electron emission, by the association of captured images with the localized emission current. The extracted information from our system can efficiently support the characterization and the development of FE devices.
SPIE Proceedings, 1999
The aim of this work is to investigate the use of microchannels to concentrate pollutants present... more The aim of this work is to investigate the use of microchannels to concentrate pollutants present in the air. Devices with a length of 30 cm, a width of 100 micrometers and a depth of 30 micrometers , sealed by anodically bonded glass, were manufactured. Tests of adsorption characteristics were made using n-hexane. To reliably insert N2 contaminated with 1000
Sensors and Actuators B: Chemical, 2003
Hexamethyldissilazane (HMDS) plasma polymerized films can be used in a wide variety of applicatio... more Hexamethyldissilazane (HMDS) plasma polymerized films can be used in a wide variety of applications due to the facility on plasma polymerization of HMDS molecule and the high resistance to acid or basic corrosion of the formed film. Nonetheless, the hydrophobic character, as well as ...
Sensors and Actuators B: Chemical, 2003
This work made use of cleaner technologies and environmental friendly reagents to produce polar o... more This work made use of cleaner technologies and environmental friendly reagents to produce polar organic films with adsorption properties to be used as sensors in the environmental field. The films were obtained by plasma deposition of 2-propanol. The films were characterized by infrared and Raman spectroscopies, contact angle measurements with different aqueous solutions, optical and Atomic Force Microscopies (AFMs). The
In this work the results obtained to develop gas sensor built with porous silicon (PS) are presen... more In this work the results obtained to develop gas sensor built with porous silicon (PS) are presented, showing the influence of organic vapors such as acetone and ethanol on electrical characteristics of devices made of Al/PS/Si/Al. The sensitivity of the PS was characterized observing changes in capacitance as a function of frequency by means of devices geometrically scaled according to perimeter/area ratio. The relationship between each organic substance and the variation of impedance with frequency was obtained, verifying that the performance of devices is not shifted by the test conditions. The behavior of complex impedance is typical of a disordered material. Also, through FTIR measurements, there is no evidence of change of PS structure due to a direct adsorption of gases, showing that the passivation of PS devices is effective to block the action of chemical substances in interface states.
This work presents the results obtained for silicon microtips fabrication of pyramidal and conica... more This work presents the results obtained for silicon microtips fabrication of pyramidal and conical shape. The tips are prepared using processes combination that applies porous silicon (PS) as sacrificial layer previously masked by hydrogen ion implantation (H + I.I.) and adequate thermal annealing. The shape of the tips is dependent on the mask geometry used by blocking anodization current where PS is not desired. After selective dissolution of PS with potassium hydroxide (KOH) at room temperature, tips are formed with height of 45 μm and 2-5 μm top diameter in square geometry or less than 0. 1 micron with circular geometry.
2019 4th International Symposium on Instrumentation Systems, Circuits and Transducers (INSCIT), 2019
Real time in-situ characterization of electron emitters is fundamental to evaluate the efficiency... more Real time in-situ characterization of electron emitters is fundamental to evaluate the efficiency of field emission devices. We here present the potentialities of a new system for this purpose, since conventional electronic systems provide only an average of the total emission current of the device under test. Through the developed system, images generated in a phosphorescent anode are captured, processed and correlated with the emission current from the effective emitting centers of the cathode surface in real time. We discuss the advantages of applying the innovative features of the new system based on virtual instrumentation concept in contrast with the traditional methods of characterization. Finally, a case study demonstrates the functionalities of the new system. The results prove that our system is an innovative tool for extracting relevant parameters in field emission devices characterization.
Proceedings IMCS 2012, 2012
Field Emission (FE) devices were successfully improved by the association of silicon (Si) microti... more Field Emission (FE) devices were successfully improved by the association of silicon (Si) microtips and Multi-Walled Carbon Nanotubes (MWCNTs). MWCNTs were deposited over Si microtips by Electrophoretic Deposition (EPD), and improvements up to 80% in electron emission characteristics were reported, being suitable for the development of gas ionization sensors based on FE devices.