Ana Santa - Academia.edu (original) (raw)
Papers by Ana Santa
Nanomaterials, Jan 3, 2023
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
Flexible and transparent microelectrodes can provide large-scale neural recordings with temporal ... more Flexible and transparent microelectrodes can provide large-scale neural recordings with temporal and spatial resolution when used alongside functional calcium imaging. Patterned metal grids defined by direct laser writing (DWL) are a promising approach for these electrodes, as they resort to standard microfabrication processes and materials, allowing the possibility of mass production. For these reasons, a study exploring transparent grid-based electrodes using DWL for measuring electrocorticography signal was performed. Patterned metal grids with 1 μm of linewidth and 22 μm of spacing between lines showed a sheet resistance of 6 Ω/sq and a transmittance of 81% at 550 nm. The grids were transferred to a 5 μm Parylene-C membrane using an optimized procedure that involves an oxygen plasma pre-treatment. This procedure ensures mechanical robustness and stability of the grids. Finally, a flexible and transparent prototype was fabricated with a microelectrode array composed by 16 electro...
The simultaneous transparency, large area uniformity and good electrical performance of indium-ga... more The simultaneous transparency, large area uniformity and good electrical performance of indium-gallium-zinc oxide (IGZO) thin-film transistors (TFTs) enables a wide range of applications. Furthermore, the possibility of fabricating them at low-temperature allows to use inexpensive flexible substrates for lightweight and conformal applications. A good example of such applications are medical systems, namely low-cost, robust, lightweight and flexible x-ray panels making use of a TFT-based active matrix array. Given the low thermal budget imposed by flexible substrates and/or other materials of the panel, namely p-type organic semiconductors for integration of CMOS circuitry into the backplane, it is expected that the chosen oxide TFT architecture dictates to a large extent the achievable level of electrical performance and stability.
2018 International Flexible Electronics Technology Conference (IFETC), 2018
This paper presents a high speed digitally programmable Ring Oscillator (RO) using Indium-gallium... more This paper presents a high speed digitally programmable Ring Oscillator (RO) using Indium-galliumzinc oxide thin-film transistors (IGZO TFTs). Proposed circuit ensures high speed compared to the conventional ROs using negative skewed scheme, in which each inverter delay is reduced by prematurely switching on/off the transistors. In addition, by controlling the load capacitance of each inverter through digital control bits, a programmable frequency of oscillation was attained. Proposed RO performance is compared with two conventional designs under same conditions. From simulation, it has been observed that the proposed circuit has shown a higher frequency of oscillations (283 KHz) compared to the conventional designs (76.52 KHz and 144.9 KHz) under same conditions. Due to the programmable feature, the circuit is able to generate 8 different linearly spaced frequencies ranging from 241.2 KHz to 283 KHz depending upon three digital control bits with almost rail-to-rail voltage swing. The circuit is a potential on-chip clock generator in many realworld flexible systems, such as, smart packaging, wearable devices, RFIDs and displays that need multi frequencies.
Developments in Combustion Technology, 2016
Oxide-based electronics have been well established as an alternative to silicon technology; howev... more Oxide-based electronics have been well established as an alternative to silicon technology; however, typical processing requires complex, high-vacuum equipment, which is a major drawback, particularly when targeting low-cost applications. The possibility to deposit the materials by low-cost techniques such as inkjet printing has drawn tremendous interest in solution processible materials for electronic applications; however, high processing temperatures still required. To overcome this issue, solution combustion synthesis has been recently pursued. Taking advantage of the exothermic nature of the reaction as a source of energy for localized heating, the precursor solutions can be converted into oxides at lower process temperatures. Theoretically, this can be applied to any metal ions to produce the desired oxide, opening unlimited possibilities to materials' composition and combinations. Solution combustion synthesis has been applied for the production of semiconductor thin films based on ZnO, In 2 O 3 , SnO 2 and combinations of these oxides, and also for high κ dielectrics (Al 2 O 3). All of which are required for numerous electronic devices and applications such as fully oxide-based thin-film transistors (TFTs). The properties of produced thin films are highly dependent on the precursor solution characteristics; hence, the influence of several processing parameters; organic fuel, solvent and annealing temperature was studied. Although precursor solution degradation/oxide formation mechanisms are not yet fully understood, particularly for thin films, we demonstrate that high-performance devices are obtained with combustion solution-based metal oxide thin films. The results clearly show that solution combustion synthesis is becoming one of the most promising methods for low-temperature flexible electronics.
2018 International Flexible Electronics Technology Conference (IFETC), 2018
This paper presents design and implementation of 8-bit shift register with low-voltage amorphous ... more This paper presents design and implementation of 8-bit shift register with low-voltage amorphous Indium Gallium Zinc Oxide (a-IGZO) thin-film transistors (TFTs) for row/column selection of pixel matrix in flexible displays. This circuit is capable of ensuring complete rail-to-rail operation by employing novel NAND gates that were developed based on capacitive bootstrapping load. As a first step, a positive edge triggered D-flip flop (D-FF) is designed using these logic gates, then a complete 8-bit shift register is designed and simulated using in-house low-voltage IGZO TFT models in Cadence Virtuoso. During these circuit simulations a power supply voltage of 2V and a channel length of 2 μm were used. Simulation outcome of 8-bit shift register has shown a power consumption of 72.15 μW with output voltage swing of 95% of Vdd at 20 kHz operating frequency, going well beyond the state of the art for oxide TFT technology at very low supply voltage. The proposed circuit can be used as a r...
IEEE Journal of the Electron Devices Society
This paper presents a high-speed ring oscillator (RO) with amorphous Indium-Gallium-Zinc-Oxide Th... more This paper presents a high-speed ring oscillator (RO) with amorphous Indium-Gallium-Zinc-Oxide Thin-film transistors (a-IGZO TFTs). The proposed RO reduces the delay of a single stage inverter using intermediate signals generated within the RO, hence, improving the speed. To validate the proposed idea, two conventional ROs (with diode-load load inverter and bootstrapped pseudo-CMOS inverter) and the proposed RO were fabricated at a temperature ≤ 180 • C. Measured results of the proposed RO have shown a frequency and power-delayproduct (PDP) of 173.2 kHz and 0.7 nJ at a supply voltage of 6 V. Further, it shows approximately 155% (44%) increase in frequency and 14% (24.5%) decrease in PDP compared to diodeload inverter (bootstrapped pseudo-CMOS inverter) based ROs. Therefore, the proposed RO finds applications in low-voltage and high speed designs for timing signal generation.
IEEE Journal of the Electron Devices Society
This paper reports on-chip rail-to-rail timing signals generation thin-film circuits for the firs... more This paper reports on-chip rail-to-rail timing signals generation thin-film circuits for the first time. These circuits, based on a-IGZO thin-film transistors (TFTs) with a simple staggered bottom gate structure, allow row and column selection of a sensor matrix embedded in a flexible radiation sensing system. They include on-chip clock generator (ring oscillator), column selector (shift register) and row-selector (a frequency divider and a shift register). They are realised with rail-to-rail logic gates with level-shifting ability that can perform inversion and NAND logic operations. These logic gates are capable of providing full output swing between supply rails, VDD and VSS, by introducing a single additional switch for each input in bootstrapping logic gates. The circuits were characterised under normal ambient atmosphere and show an improved performance compared to the conventional logic gates with diode connected load and pseudo CMOS counterparts. By using these highperformance logic gates, a complete rail-to-rail frequency divider is presented from measurements using D-Flip Flop. In order to realize a complete compact system, an on-chip ring oscillator (output clock frequency around 1 kHz) and a shift register are also presented from simulations, where these circuits show a power consumption of 1.5 mW and 0.82 mW at a supply voltage of 8 V, respectively. While the circuit concepts described here were designed for an X-ray sensing system, they can be readily expanded to other domains where flexible on-chip timing signal generation is required, such as, smart packaging, biomedical wearable devices and RFIDs.
IEEE Journal of the Electron Devices Society
This paper presents a novel high-gain transimpedance amplifier for flexible radiation sensing sys... more This paper presents a novel high-gain transimpedance amplifier for flexible radiation sensing systems that can be used as large-area dosimeters. The circuit is implemented with indium-galliumzinc-oxide thin-film-transistors and uses two stages for the amplification of the sensor signal (current). The first stage consists of cascode current mirrors with a diode connected load that performs current amplification and voltage conversion. Then, the first stage is followed by a voltage amplifier based on a positive feedback topology for gain enhancement. The proposed circuit converts nano-ampere (10 nA) currents into hundreds of millivolts (280 mV), showing a gain around 149 dB and a power consumption of 0.45 mW. The sensed radiation dose level, in voltage terms, can drive the next stages in the radiation sensing system, such as analog to digital converters. These radiation sensing devices can find potential applications in real-time, large area, flexible health, and security systems. INDEX TERMS Amplifier, a-IGZO TFT, positive feedback.
IEEE Journal of the Electron Devices Society
This paper presents the experimental characterisation of different rectifier circuits using IGZO ... more This paper presents the experimental characterisation of different rectifier circuits using IGZO TFTs either at NFC or high frequency range (13.56 MHz) of RFID. These circuits include single ended rectifier, its differential counterpart, bridge rectifier and a cross-coupled full wave rectifier. Diodes were implemented with transistors using conventional processing steps, without requiring short channel devices (L=15 µm). Hence there is no need of either extra masks or processing steps unlike Schottky diode based implementation. These circuits were fabricated on PEN substrate with an annealing temperature not exceeding 180 • C. This work finds direct application in flexible low-cost RFID tags since it enables integration of required electronics to implement tags with the same fabrication steps.
Semiconductor Science and Technology
Advanced Electronic Materials
Science advances, 2018
Distributed x-ray radiation dosimetry is crucial in diverse security areas with significant envir... more Distributed x-ray radiation dosimetry is crucial in diverse security areas with significant environmental and human impacts such as nuclear waste management, radiotherapy, or radioprotection devices. We present a fast, real-time dosimetry detection system based on flexible oxide thin-film transistors that show a quantitative shift in threshold voltage of up to 3.4 V/gray upon exposure to ionizing radiation. The transistors use indium-gallium-zinc-oxide as a semiconductor and a multilayer dielectric based on silicon oxide and tantalum oxide. Our measurements demonstrate that the threshold voltage shift is caused by the accumulation of positive ionization charge in the dielectric layer due to high-energy photon absorption in the high- dielectric. The high mobility combined with a steep subthreshold slope of the transistor allows for fast, reliable, and ultralow-power readout of the deposited radiation dose. The order-of-magnitude variation in transistor channel impedance upon exposure...
Printed electronics is a research area in full expansion due to potential technological applicati... more Printed electronics is a research area in full expansion due to potential technological applications and the impact on society. Consequently, the development of materials with applications in electronics and which can be processed by solution is of extreme importance as it allows a reduction of the processing temperature of the devices to make these compatible with the use of low cost substrates. In this context, solution combustion synthesis has been recently considered as a viable alternative to low-cost production of oxides. Solution processed metal oxide semiconductors for use in TFTs are currently being developed, however, there is also a need to develop dielectric oxides that can be solution processed. In this work was explored solution combustion synthesis of thin films of aluminum oxide using environment-friendly materials such as water and etanol. As a comparison, alumina was also produced with 2-methoxyethanol as solvent. The decomposition of AlOx precursor solutions was investigated. Electrical characteristics were evaluated for TFTs produced with a semiconductor layer deposited by sputtering; GIZO, and solution-processed; ZTO. Dielectric films obtained from water based precursor solution that demonstrated high capacitance, were integrated into TFTs (AlOx / GIZO) yielding good electrical performance, with a maximum saturation mobility of 33 cm 2 /Vs at low operation voltages, with AlOx prepared with a process temperature as low as 250 ᵒC. Solution processed (ZTO/AlOx) TFTs demonstrated low hysteresis, low threshold voltage and a saturation mobility of 0.8 cm 2 /Vs at low operation voltages.
ABSTRACT Solution based deposition has been recently considered as a viable option for low-cost f... more ABSTRACT Solution based deposition has been recently considered as a viable option for low-cost flexible electronics. In this context research efforts have been increasingly centred on the development of suitable solution-processed materials for oxide based transistors. Nevertheless, the majority of synthetic routes reported require the use of toxic organic solvents. In this work we report on a new environmental friendly solution combustion synthesis route, using ethanol as solvent, for the preparation of indium/gallium free amorphous zinc-tin oxide (ZTO) thin film transistors (TFTs) including AlOx gate dielectric. The decomposition of ZTO and AlOx precursor solutions, electrical characterization and stability of solution processed ZTO/AlOx TFTs under gate-bias stress, in both air and vacuum atmosphere, were investigated. The devices demonstrated low hysteresis (Delta V = 0.23 V), close to zero turn on voltage, low threshold voltage (VT = 0.36 V) and a saturation mobility of 0.8 cm(2) V-1 s(-1) at low operation voltages. Ethanol based ZTO/AlOx TFTs are a promising alternative for applications in disposable, low cost and environmental friendly electronics.
Developments in Combustion Technology, 2016
Nanomaterials, Jan 3, 2023
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
Flexible and transparent microelectrodes can provide large-scale neural recordings with temporal ... more Flexible and transparent microelectrodes can provide large-scale neural recordings with temporal and spatial resolution when used alongside functional calcium imaging. Patterned metal grids defined by direct laser writing (DWL) are a promising approach for these electrodes, as they resort to standard microfabrication processes and materials, allowing the possibility of mass production. For these reasons, a study exploring transparent grid-based electrodes using DWL for measuring electrocorticography signal was performed. Patterned metal grids with 1 μm of linewidth and 22 μm of spacing between lines showed a sheet resistance of 6 Ω/sq and a transmittance of 81% at 550 nm. The grids were transferred to a 5 μm Parylene-C membrane using an optimized procedure that involves an oxygen plasma pre-treatment. This procedure ensures mechanical robustness and stability of the grids. Finally, a flexible and transparent prototype was fabricated with a microelectrode array composed by 16 electro...
The simultaneous transparency, large area uniformity and good electrical performance of indium-ga... more The simultaneous transparency, large area uniformity and good electrical performance of indium-gallium-zinc oxide (IGZO) thin-film transistors (TFTs) enables a wide range of applications. Furthermore, the possibility of fabricating them at low-temperature allows to use inexpensive flexible substrates for lightweight and conformal applications. A good example of such applications are medical systems, namely low-cost, robust, lightweight and flexible x-ray panels making use of a TFT-based active matrix array. Given the low thermal budget imposed by flexible substrates and/or other materials of the panel, namely p-type organic semiconductors for integration of CMOS circuitry into the backplane, it is expected that the chosen oxide TFT architecture dictates to a large extent the achievable level of electrical performance and stability.
2018 International Flexible Electronics Technology Conference (IFETC), 2018
This paper presents a high speed digitally programmable Ring Oscillator (RO) using Indium-gallium... more This paper presents a high speed digitally programmable Ring Oscillator (RO) using Indium-galliumzinc oxide thin-film transistors (IGZO TFTs). Proposed circuit ensures high speed compared to the conventional ROs using negative skewed scheme, in which each inverter delay is reduced by prematurely switching on/off the transistors. In addition, by controlling the load capacitance of each inverter through digital control bits, a programmable frequency of oscillation was attained. Proposed RO performance is compared with two conventional designs under same conditions. From simulation, it has been observed that the proposed circuit has shown a higher frequency of oscillations (283 KHz) compared to the conventional designs (76.52 KHz and 144.9 KHz) under same conditions. Due to the programmable feature, the circuit is able to generate 8 different linearly spaced frequencies ranging from 241.2 KHz to 283 KHz depending upon three digital control bits with almost rail-to-rail voltage swing. The circuit is a potential on-chip clock generator in many realworld flexible systems, such as, smart packaging, wearable devices, RFIDs and displays that need multi frequencies.
Developments in Combustion Technology, 2016
Oxide-based electronics have been well established as an alternative to silicon technology; howev... more Oxide-based electronics have been well established as an alternative to silicon technology; however, typical processing requires complex, high-vacuum equipment, which is a major drawback, particularly when targeting low-cost applications. The possibility to deposit the materials by low-cost techniques such as inkjet printing has drawn tremendous interest in solution processible materials for electronic applications; however, high processing temperatures still required. To overcome this issue, solution combustion synthesis has been recently pursued. Taking advantage of the exothermic nature of the reaction as a source of energy for localized heating, the precursor solutions can be converted into oxides at lower process temperatures. Theoretically, this can be applied to any metal ions to produce the desired oxide, opening unlimited possibilities to materials' composition and combinations. Solution combustion synthesis has been applied for the production of semiconductor thin films based on ZnO, In 2 O 3 , SnO 2 and combinations of these oxides, and also for high κ dielectrics (Al 2 O 3). All of which are required for numerous electronic devices and applications such as fully oxide-based thin-film transistors (TFTs). The properties of produced thin films are highly dependent on the precursor solution characteristics; hence, the influence of several processing parameters; organic fuel, solvent and annealing temperature was studied. Although precursor solution degradation/oxide formation mechanisms are not yet fully understood, particularly for thin films, we demonstrate that high-performance devices are obtained with combustion solution-based metal oxide thin films. The results clearly show that solution combustion synthesis is becoming one of the most promising methods for low-temperature flexible electronics.
2018 International Flexible Electronics Technology Conference (IFETC), 2018
This paper presents design and implementation of 8-bit shift register with low-voltage amorphous ... more This paper presents design and implementation of 8-bit shift register with low-voltage amorphous Indium Gallium Zinc Oxide (a-IGZO) thin-film transistors (TFTs) for row/column selection of pixel matrix in flexible displays. This circuit is capable of ensuring complete rail-to-rail operation by employing novel NAND gates that were developed based on capacitive bootstrapping load. As a first step, a positive edge triggered D-flip flop (D-FF) is designed using these logic gates, then a complete 8-bit shift register is designed and simulated using in-house low-voltage IGZO TFT models in Cadence Virtuoso. During these circuit simulations a power supply voltage of 2V and a channel length of 2 μm were used. Simulation outcome of 8-bit shift register has shown a power consumption of 72.15 μW with output voltage swing of 95% of Vdd at 20 kHz operating frequency, going well beyond the state of the art for oxide TFT technology at very low supply voltage. The proposed circuit can be used as a r...
IEEE Journal of the Electron Devices Society
This paper presents a high-speed ring oscillator (RO) with amorphous Indium-Gallium-Zinc-Oxide Th... more This paper presents a high-speed ring oscillator (RO) with amorphous Indium-Gallium-Zinc-Oxide Thin-film transistors (a-IGZO TFTs). The proposed RO reduces the delay of a single stage inverter using intermediate signals generated within the RO, hence, improving the speed. To validate the proposed idea, two conventional ROs (with diode-load load inverter and bootstrapped pseudo-CMOS inverter) and the proposed RO were fabricated at a temperature ≤ 180 • C. Measured results of the proposed RO have shown a frequency and power-delayproduct (PDP) of 173.2 kHz and 0.7 nJ at a supply voltage of 6 V. Further, it shows approximately 155% (44%) increase in frequency and 14% (24.5%) decrease in PDP compared to diodeload inverter (bootstrapped pseudo-CMOS inverter) based ROs. Therefore, the proposed RO finds applications in low-voltage and high speed designs for timing signal generation.
IEEE Journal of the Electron Devices Society
This paper reports on-chip rail-to-rail timing signals generation thin-film circuits for the firs... more This paper reports on-chip rail-to-rail timing signals generation thin-film circuits for the first time. These circuits, based on a-IGZO thin-film transistors (TFTs) with a simple staggered bottom gate structure, allow row and column selection of a sensor matrix embedded in a flexible radiation sensing system. They include on-chip clock generator (ring oscillator), column selector (shift register) and row-selector (a frequency divider and a shift register). They are realised with rail-to-rail logic gates with level-shifting ability that can perform inversion and NAND logic operations. These logic gates are capable of providing full output swing between supply rails, VDD and VSS, by introducing a single additional switch for each input in bootstrapping logic gates. The circuits were characterised under normal ambient atmosphere and show an improved performance compared to the conventional logic gates with diode connected load and pseudo CMOS counterparts. By using these highperformance logic gates, a complete rail-to-rail frequency divider is presented from measurements using D-Flip Flop. In order to realize a complete compact system, an on-chip ring oscillator (output clock frequency around 1 kHz) and a shift register are also presented from simulations, where these circuits show a power consumption of 1.5 mW and 0.82 mW at a supply voltage of 8 V, respectively. While the circuit concepts described here were designed for an X-ray sensing system, they can be readily expanded to other domains where flexible on-chip timing signal generation is required, such as, smart packaging, biomedical wearable devices and RFIDs.
IEEE Journal of the Electron Devices Society
This paper presents a novel high-gain transimpedance amplifier for flexible radiation sensing sys... more This paper presents a novel high-gain transimpedance amplifier for flexible radiation sensing systems that can be used as large-area dosimeters. The circuit is implemented with indium-galliumzinc-oxide thin-film-transistors and uses two stages for the amplification of the sensor signal (current). The first stage consists of cascode current mirrors with a diode connected load that performs current amplification and voltage conversion. Then, the first stage is followed by a voltage amplifier based on a positive feedback topology for gain enhancement. The proposed circuit converts nano-ampere (10 nA) currents into hundreds of millivolts (280 mV), showing a gain around 149 dB and a power consumption of 0.45 mW. The sensed radiation dose level, in voltage terms, can drive the next stages in the radiation sensing system, such as analog to digital converters. These radiation sensing devices can find potential applications in real-time, large area, flexible health, and security systems. INDEX TERMS Amplifier, a-IGZO TFT, positive feedback.
IEEE Journal of the Electron Devices Society
This paper presents the experimental characterisation of different rectifier circuits using IGZO ... more This paper presents the experimental characterisation of different rectifier circuits using IGZO TFTs either at NFC or high frequency range (13.56 MHz) of RFID. These circuits include single ended rectifier, its differential counterpart, bridge rectifier and a cross-coupled full wave rectifier. Diodes were implemented with transistors using conventional processing steps, without requiring short channel devices (L=15 µm). Hence there is no need of either extra masks or processing steps unlike Schottky diode based implementation. These circuits were fabricated on PEN substrate with an annealing temperature not exceeding 180 • C. This work finds direct application in flexible low-cost RFID tags since it enables integration of required electronics to implement tags with the same fabrication steps.
Semiconductor Science and Technology
Advanced Electronic Materials
Science advances, 2018
Distributed x-ray radiation dosimetry is crucial in diverse security areas with significant envir... more Distributed x-ray radiation dosimetry is crucial in diverse security areas with significant environmental and human impacts such as nuclear waste management, radiotherapy, or radioprotection devices. We present a fast, real-time dosimetry detection system based on flexible oxide thin-film transistors that show a quantitative shift in threshold voltage of up to 3.4 V/gray upon exposure to ionizing radiation. The transistors use indium-gallium-zinc-oxide as a semiconductor and a multilayer dielectric based on silicon oxide and tantalum oxide. Our measurements demonstrate that the threshold voltage shift is caused by the accumulation of positive ionization charge in the dielectric layer due to high-energy photon absorption in the high- dielectric. The high mobility combined with a steep subthreshold slope of the transistor allows for fast, reliable, and ultralow-power readout of the deposited radiation dose. The order-of-magnitude variation in transistor channel impedance upon exposure...
Printed electronics is a research area in full expansion due to potential technological applicati... more Printed electronics is a research area in full expansion due to potential technological applications and the impact on society. Consequently, the development of materials with applications in electronics and which can be processed by solution is of extreme importance as it allows a reduction of the processing temperature of the devices to make these compatible with the use of low cost substrates. In this context, solution combustion synthesis has been recently considered as a viable alternative to low-cost production of oxides. Solution processed metal oxide semiconductors for use in TFTs are currently being developed, however, there is also a need to develop dielectric oxides that can be solution processed. In this work was explored solution combustion synthesis of thin films of aluminum oxide using environment-friendly materials such as water and etanol. As a comparison, alumina was also produced with 2-methoxyethanol as solvent. The decomposition of AlOx precursor solutions was investigated. Electrical characteristics were evaluated for TFTs produced with a semiconductor layer deposited by sputtering; GIZO, and solution-processed; ZTO. Dielectric films obtained from water based precursor solution that demonstrated high capacitance, were integrated into TFTs (AlOx / GIZO) yielding good electrical performance, with a maximum saturation mobility of 33 cm 2 /Vs at low operation voltages, with AlOx prepared with a process temperature as low as 250 ᵒC. Solution processed (ZTO/AlOx) TFTs demonstrated low hysteresis, low threshold voltage and a saturation mobility of 0.8 cm 2 /Vs at low operation voltages.
ABSTRACT Solution based deposition has been recently considered as a viable option for low-cost f... more ABSTRACT Solution based deposition has been recently considered as a viable option for low-cost flexible electronics. In this context research efforts have been increasingly centred on the development of suitable solution-processed materials for oxide based transistors. Nevertheless, the majority of synthetic routes reported require the use of toxic organic solvents. In this work we report on a new environmental friendly solution combustion synthesis route, using ethanol as solvent, for the preparation of indium/gallium free amorphous zinc-tin oxide (ZTO) thin film transistors (TFTs) including AlOx gate dielectric. The decomposition of ZTO and AlOx precursor solutions, electrical characterization and stability of solution processed ZTO/AlOx TFTs under gate-bias stress, in both air and vacuum atmosphere, were investigated. The devices demonstrated low hysteresis (Delta V = 0.23 V), close to zero turn on voltage, low threshold voltage (VT = 0.36 V) and a saturation mobility of 0.8 cm(2) V-1 s(-1) at low operation voltages. Ethanol based ZTO/AlOx TFTs are a promising alternative for applications in disposable, low cost and environmental friendly electronics.
Developments in Combustion Technology, 2016