Amrita Masurkar - Academia.edu (original) (raw)

Conference Presentations by Amrita Masurkar

Research paper thumbnail of The effect of thermal reduction and film thickness on fast response transparent graphene oxide humidity sensors

Resistive chemical sensors were developed having as sensitive film graphene oxide (GO) spin-coate... more Resistive chemical sensors were developed having as sensitive film graphene oxide (GO) spin-coated on glass. Sensor electrical behaviour to room temperature relative humidity was evaluated. High sensitivity characterizes GO sensor. However, it lacks repeatability and long term stability. To this end, we developed spin-coated GO sensors with different active layer thickness, which were subjected to subsequent thermal annealing steps. It was found that the resulting reduced GO (rGO) sensors demonstrate excellent stability compromising, though, the sensitivity which mainly depends on the number of annealing steps and film thickness. Finally, we propose a rapid, transparent, low-power consumption rGO sensor, enabling its use in relevant applications.

Papers by Amrita Masurkar

Research paper thumbnail of CCDC 1557907: Experimental Crystal Structure Determination

An entry from the Cambridge Structural Database, the world's repository for small molecule cr... more An entry from the Cambridge Structural Database, the world's repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

Research paper thumbnail of CCDC 1557899: Experimental Crystal Structure Determination

An entry from the Cambridge Structural Database, the world's repository for small molecule cr... more An entry from the Cambridge Structural Database, the world's repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

Research paper thumbnail of CCDC 1558128: Experimental Crystal Structure Determination

An entry from the Cambridge Structural Database, the world's repository for small molecule cr... more An entry from the Cambridge Structural Database, the world's repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

Research paper thumbnail of Single-Polarization, Optically Pre-Amplified Receiver With Gated, Burst-Mode Clock Recovery

IEEE Photonics Technology Letters, 2018

We report a receiver using a single-polarization optical low-noise pre-amplifier and a burst-mode... more We report a receiver using a single-polarization optical low-noise pre-amplifier and a burst-mode, time-gated clock recovery unit (CRU). Timing jitter and bit-errorratio (BER) measurements are presented for data rates from 72 Mb/s to 2.880 Gb/s, both with and without atmospheric fading. At the lowest burst-mode data rate of 72 Mb/s, temporal gating improves the recovered clock's timing jitter below receive power levels of −65 dBm, enabling comm-limited performance as opposed to CRU-limited performance. Gating extends the CRU and receiver range down to −88 dBm, a 3-dB sensitivity improvement over the non-gated case. For all data rates and channels measured, jitter values remain below 9 ps (3% of the clock period) with gating enabled. The BER performance is <2.5 dB from the theoretical limit across all data rates, both with and without atmospheric fading.

Research paper thumbnail of Charge Injection and Transport in Pentacene Field-Effect Transistors

Charge Injection and Transport in Pentacene Field-Effect Transistors

Research paper thumbnail of Permanent water swelling effect in low temperature thermally reduced graphene oxide

Applied Physics Letters, 2017

We demonstrate permanent water trapping in reduced graphene oxide (rGO) after high relative humid... more We demonstrate permanent water trapping in reduced graphene oxide (rGO) after high relative humidity (RH) exposure. For this purpose, we grew graphene oxide films via spin-coating on glass substrates followed by thermal reduction. The electrical resistance of the planar device was then measured. We observed that resistance is significantly increased after water vapor exposure and remains stable even after 250 days in ambient conditions. Various techniques were applied to desorb the water and decrease (recover) the material's resistance, but it was achieved only with low temperature thermal annealing (180 0 C) under forming gas (H 2 /N 2 mixture). The permanent effect of water absorption was also detected by x-ray photoelectron spectroscopy. Reduced graphene oxide (rGO) has attracted a strong research interest for gas sensing applications in recent years due to its unique electrical and chemical characteristics 1,2,3. Its main advantages among others are good chemical stability over time and ease of functionalization contributing to satisfying selectivity between various analytes 4. The gas sensing mechanism _____________________________

Research paper thumbnail of Unexpected length dependence of excited-state charge transfer dynamics for surface-confined perylenediimide ensembles

Mater. Horiz., 2017

I. General Information and Procedures. A. Materials. All general chemical reagents were purchased... more I. General Information and Procedures. A. Materials. All general chemical reagents were purchased from Acros Organics, Sigma-Aldrich, or Combi-Blocks. The solvents were obtained from Fisher Scientific and used as received, unless otherwise noted. Flash chromatography was performed using SiliCycle Silica Flash F60 silica gel. The specific chemical reagents and commercial phosphoramidites required for the automated synthesis steps were purchased from either Glen Research, Inc. or FIVEphoton Biochemicals, Inc. and used as received. B. General Procedures for Characterization of the Small Molecule Precursors. All intermediates and products for the phosphoramidite synthesis were characterized with nuclear magnetic resonance (NMR) spectroscopy and mass spectrometry. The electrospray mass spectrometry (ESI MS) data were obtained at the University of California, Irvine Mass Spectrometry Facility on a Waters LCT Premier electrospray time-of-flight instrument. The 1 H NMR spectra were obtained on either a Bruker DRX500 or an AVANCE600 instrument. The 13 C NMR spectra were obtained on a Bruker DRX500 outfitted with a CryoProbe (Bruker TCI 500 MHz, 5 mm diameter tubes). The 31 P NMR spectra were acquired on a Bruker AVANCE600 instrument. Chemical shifts were reported in ppm for 1 H, 13 C, 19 F, and 31 P NMR. The chemical shifts for the NMR data were referenced as follows: for samples in CDCl 3 , the 1 H NMR was referenced to tetramethylsilane (TMS) at 0.00, and the 13 C NMR was referenced to CDCl 3 at 77.23; for samples in CD 3 OD, the 13 C NMR was referenced to the solvent peak at 49.00; for samples in CD 2 Cl 2 , the 1 H NMR was referenced to the solvent peak at 5.32, and the 13 C NMR was referenced to the solvent peak at 54.00. The chemical shifts for the 31 P NMR spectra were corrected and referenced by using 1 H NMR according to the 2008 IUPAC recommendations. [S1] The data are labeled as follows: chemical shift, multiplicity (s = singlet, d = doublet, t = triplet, q

Research paper thumbnail of Single-crystal-to-single-crystal intercalation of a low-bandgap superatomic crystal

Nature Chemistry, 2017

The controlled introduction of impurities into the crystal lattice of solid-state compounds is a ... more The controlled introduction of impurities into the crystal lattice of solid-state compounds is a cornerstone of materials science. Intercalation, the insertion of guest atoms, ions or molecules between the atomic layers of a host structure, can produce novel electronic, magnetic and optical properties in many materials. Here we describe an intercalation compound in which the host [Co 6 Te 8 (P n Pr 3) 6 ][C 60 ] 3 , formed from the binary assembly of atomically precise molecular clusters, is a superatomic analogue of traditional layered atomic compounds. We find that tetracyanoethylene (TCNE) can be inserted into the superstructure through a single-crystal-to-single-crystal transformation. Using electronic absorption spectroscopy, electrical transport measurements and electronic structure calculations, we demonstrate that the intercalation is driven by the exchange of charge between the host [Co 6 Te 8 (P n Pr 3) 6 ][C 60 ] 3 and the intercalant TCNE. These results show that intercalation is a powerful approach to manipulate the material properties of superatomic crystals.

Research paper thumbnail of The Effect of Thermal Reduction and Film Thickness on fast Response Transparent Graphene Oxide Humidity Sensors

Procedia Engineering, 2016

Resistive chemical sensors were developed having as sensitive film graphene oxide (GO) spin-coate... more Resistive chemical sensors were developed having as sensitive film graphene oxide (GO) spin-coated on glass. Sensor electrical behaviour to room temperature relative humidity was evaluated. High sensitivity characterizes GO sensor. However, it lacks repeatability and long term stability. To this end, we developed spin-coated GO sensors with different active layer thickness, which were subjected to subsequent thermal annealing steps. It was found that the resulting reduced GO (rGO) sensors demonstrate excellent stability compromising, though, the sensitivity which mainly depends on the number of annealing steps and film thickness. Finally, we propose a rapid, transparent, low-power consumption rGO sensor, enabling its use in relevant applications.

Research paper thumbnail of Improving the radiation hardness of graphene field effect transistors

Applied Physics Letters, 2016

Ionizing radiation poses a significant challenge to the operation and reliability of conventional... more Ionizing radiation poses a significant challenge to the operation and reliability of conventional silicon-based devices. Here, we report the effects of gamma radiation on graphene field-effect transistors (GFETs), along with a method to mitigate those effects by developing a radiationhardened version of our back-gated GFETs. We demonstrate that activated atmospheric oxygen from the gamma ray interaction with air damages the semiconductor device, and damage to the substrate contributes additional threshold voltage instability. Our radiation-hardened devices, which have protection against these two effects, exhibit minimal performance degradation, improved stability, and significantly reduced hysteresis after prolonged gamma radiation exposure. We believe this work provides an insight on graphene's interactions with ionizing radiation that could enable future graphene-based electronic devices to be used for space, military, and other radiation-sensitive applications.

Research paper thumbnail of Radiation hardened graphene field effect transistors

2016 74th Annual Device Research Conference (DRC), 2016

Our work demonstrates that both encapsulation and an insulated gate are needed to effectively pro... more Our work demonstrates that both encapsulation and an insulated gate are needed to effectively produce radiation hard GFETs. Our devices successfully mitigate detrimental radiation effects which consists a significant step towards enabling graphene-based electronic devices to be used for space, military, and other radiation sensitive applications.

Research paper thumbnail of Comparison of top- and bottom-contact pentacene field-effect transistors using photocurrent microscopy

2016 74th Annual Device Research Conference (DRC), 2016

Overview Bottom-contact (BC) organic field-effect transistors (OFETs), though more industry-relev... more Overview Bottom-contact (BC) organic field-effect transistors (OFETs), though more industry-relevant than top-contact (TC) OFETs, are prone to low source-drain currents. The underlying mechanisms behind this remain debated. Thus, our work uses photocurrent microscopy (PCM) to examine charge injection in BC and TC geometries. PCM maps were generated first for OFETs with no electrode or gate dielectric treatments. Potential plots were quantitatively derived from the results using a method from previous work. [1] PCM maps were then collected for devices treated with 1. pentafluorobenzenethiol (PFBT), known to improve semiconductor morphology [2], and 2. UV-ozone, which is thought to enhance trap-assisted carrier transport. [3] These treatments were chosen, because they significantly increase source-drain current in BC devices, but in vastly different ways. In addition, unlike other photocurrent studies, we used a range of illumination wavelengths so as to probe various exciton states.

Research paper thumbnail of Photocurrent measurements of pentacene-based devices

Applied Physics Reviews, 2015

Photocurrent spectroscopy (PCS) and photocurrent microscopy (PCM) are powerful tools that can pro... more Photocurrent spectroscopy (PCS) and photocurrent microscopy (PCM) are powerful tools that can probe the underlying mechanisms of charge generation and transport in organic semiconductor devices. There has been significant progress in the use of these techniques, which has yielded a number of insights into the underlying materials and operation of the devices. Despite the potential for PCS and PCM to become standard tools, however, a consensus has not been reached on (1) its uses and (2) the underlying mechanisms which produce the photoresponse. This is particularly true for measurements of pentacene devices, as the energy dynamics of pentacene are complex. Accordingly, here we report the current body of PCS and PCM of pentacene devices, offer interpretations of the data, and discuss which questions remain unanswered. We have divided the reviewed work into four categories based on the goals of the study and the technique used: photocurrent spectroscopy, scanning photocurrent microscopy, mobility, and trap density-of-states.

Research paper thumbnail of Single-polarization, optical low-noise pre-amplified receiver for heavily-coded optical communications links

Free-Space Laser Communication and Atmospheric Propagation XXVII, 2015

We report a single-polarization, optical low-noise pre-amplfier (SP-OLNA) that enhances the recei... more We report a single-polarization, optical low-noise pre-amplfier (SP-OLNA) that enhances the receiver sensitivity of heavily-coded 1.55-μm optical communication links. At channel bit-error ratios of approximately 10%, the erbium-doped SP-OLNA provides an approximately 1.0-dB receiver sensitivity enhancement over a conventional two-polarization pre-amplfier. The SP-OLNA includes three gain stages, each followed by narrow-band athermal fiber Bragg gratings. This cascaded fiter is matched to a return-to-zero, 2.88-Gb/s, variable burst-mode, differential phase shift keying (DPSK) waveform. The SP-OLNA enhancement of approximately 1.0 dB is demonstrated over a range of data rates, from the full 2.88-Gb/s (non-burst) data rate, down to a 1/40th burst rate (72 Mb/s). The SP-OLNA'sfirst stage of ampli_cation is a single-polarization gain block constructed from polarization-maintaining (PM) fiber components, PM erbium gain fiber, and a PM integrated pump coupler and polarizer. This first stage sets the SP-OLNA's noise figure, measured at 3.4 dB. Two subsequent non-PM gain stages allow the SP-OLNA to provide an overall gain of 78 dB to drive a DPSK demodulator receiver. This receiver is comprised of a delay-line interferometer and balanced photo-receiver. The SP-OLNA is packaged into a compact, 5"x7"x1.6" volume, which includes an electronic digital interface to control and monitor pump lasers, optical switches, and power monitors.

Research paper thumbnail of Extensions of quartz-enhanced photoacoustic spectroscopy

The goal of this thesis was to perform quartz-enhanced photoacoustic spectroscopy (QEPAS) on trac... more The goal of this thesis was to perform quartz-enhanced photoacoustic spectroscopy (QEPAS) on trace concentrations of NH 3 in the 1.53 pm region with a DFB laser without the use of a resonating cavity. I analyzed the process of QEPAS both analytically and experimentally. First, absorption spectroscopy was performed with a 1.55 pm DFB laser on the 1558.033 nm absorption line of H 13 C 12 N. The wavelength of the laser radiation was then modulated, and the spectral components of the absorbance were analyzed. In addition, low concentrations of NH 3 were generated through the use of a vaccuum system, and absorption spectoscopy was performed on these samples. A tuning fork was also characterized. Photoacoustic signals were ultimately not realized, however, plans for future work are mentioned.

Research paper thumbnail of An ultra thin implantable system for cerebral blood volume monitoring using flexible OLED and OPD

2015 IEEE International Electron Devices Meeting (IEDM), 2015

An ultra thin implantable system using flexible organic light emitting diodes (OLEDs) and organic... more An ultra thin implantable system using flexible organic light emitting diodes (OLEDs) and organic photodetectors (OPDs) on parylene substrate shows biocompatibility and high conformability on any surface. This system was used to monitor variations in cerebral blood volume (CBV) corresponding to an epileptic seizure, along with baseline signals such as heartbeat, respiration and slow sinusoidal hemodynamic oscillations (SSHOs). As such, this system shows strong potential for implantable and/or wearable biosensors for continuous health monitoring.

Research paper thumbnail of The effect of thermal reduction and film thickness on fast response transparent graphene oxide humidity sensors

Resistive chemical sensors were developed having as sensitive film graphene oxide (GO) spin-coate... more Resistive chemical sensors were developed having as sensitive film graphene oxide (GO) spin-coated on glass. Sensor electrical behaviour to room temperature relative humidity was evaluated. High sensitivity characterizes GO sensor. However, it lacks repeatability and long term stability. To this end, we developed spin-coated GO sensors with different active layer thickness, which were subjected to subsequent thermal annealing steps. It was found that the resulting reduced GO (rGO) sensors demonstrate excellent stability compromising, though, the sensitivity which mainly depends on the number of annealing steps and film thickness. Finally, we propose a rapid, transparent, low-power consumption rGO sensor, enabling its use in relevant applications.

Research paper thumbnail of CCDC 1557907: Experimental Crystal Structure Determination

An entry from the Cambridge Structural Database, the world's repository for small molecule cr... more An entry from the Cambridge Structural Database, the world's repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

Research paper thumbnail of CCDC 1557899: Experimental Crystal Structure Determination

An entry from the Cambridge Structural Database, the world's repository for small molecule cr... more An entry from the Cambridge Structural Database, the world's repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

Research paper thumbnail of CCDC 1558128: Experimental Crystal Structure Determination

An entry from the Cambridge Structural Database, the world's repository for small molecule cr... more An entry from the Cambridge Structural Database, the world's repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

Research paper thumbnail of Single-Polarization, Optically Pre-Amplified Receiver With Gated, Burst-Mode Clock Recovery

IEEE Photonics Technology Letters, 2018

We report a receiver using a single-polarization optical low-noise pre-amplifier and a burst-mode... more We report a receiver using a single-polarization optical low-noise pre-amplifier and a burst-mode, time-gated clock recovery unit (CRU). Timing jitter and bit-errorratio (BER) measurements are presented for data rates from 72 Mb/s to 2.880 Gb/s, both with and without atmospheric fading. At the lowest burst-mode data rate of 72 Mb/s, temporal gating improves the recovered clock's timing jitter below receive power levels of −65 dBm, enabling comm-limited performance as opposed to CRU-limited performance. Gating extends the CRU and receiver range down to −88 dBm, a 3-dB sensitivity improvement over the non-gated case. For all data rates and channels measured, jitter values remain below 9 ps (3% of the clock period) with gating enabled. The BER performance is <2.5 dB from the theoretical limit across all data rates, both with and without atmospheric fading.

Research paper thumbnail of Charge Injection and Transport in Pentacene Field-Effect Transistors

Charge Injection and Transport in Pentacene Field-Effect Transistors

Research paper thumbnail of Permanent water swelling effect in low temperature thermally reduced graphene oxide

Applied Physics Letters, 2017

We demonstrate permanent water trapping in reduced graphene oxide (rGO) after high relative humid... more We demonstrate permanent water trapping in reduced graphene oxide (rGO) after high relative humidity (RH) exposure. For this purpose, we grew graphene oxide films via spin-coating on glass substrates followed by thermal reduction. The electrical resistance of the planar device was then measured. We observed that resistance is significantly increased after water vapor exposure and remains stable even after 250 days in ambient conditions. Various techniques were applied to desorb the water and decrease (recover) the material's resistance, but it was achieved only with low temperature thermal annealing (180 0 C) under forming gas (H 2 /N 2 mixture). The permanent effect of water absorption was also detected by x-ray photoelectron spectroscopy. Reduced graphene oxide (rGO) has attracted a strong research interest for gas sensing applications in recent years due to its unique electrical and chemical characteristics 1,2,3. Its main advantages among others are good chemical stability over time and ease of functionalization contributing to satisfying selectivity between various analytes 4. The gas sensing mechanism _____________________________

Research paper thumbnail of Unexpected length dependence of excited-state charge transfer dynamics for surface-confined perylenediimide ensembles

Mater. Horiz., 2017

I. General Information and Procedures. A. Materials. All general chemical reagents were purchased... more I. General Information and Procedures. A. Materials. All general chemical reagents were purchased from Acros Organics, Sigma-Aldrich, or Combi-Blocks. The solvents were obtained from Fisher Scientific and used as received, unless otherwise noted. Flash chromatography was performed using SiliCycle Silica Flash F60 silica gel. The specific chemical reagents and commercial phosphoramidites required for the automated synthesis steps were purchased from either Glen Research, Inc. or FIVEphoton Biochemicals, Inc. and used as received. B. General Procedures for Characterization of the Small Molecule Precursors. All intermediates and products for the phosphoramidite synthesis were characterized with nuclear magnetic resonance (NMR) spectroscopy and mass spectrometry. The electrospray mass spectrometry (ESI MS) data were obtained at the University of California, Irvine Mass Spectrometry Facility on a Waters LCT Premier electrospray time-of-flight instrument. The 1 H NMR spectra were obtained on either a Bruker DRX500 or an AVANCE600 instrument. The 13 C NMR spectra were obtained on a Bruker DRX500 outfitted with a CryoProbe (Bruker TCI 500 MHz, 5 mm diameter tubes). The 31 P NMR spectra were acquired on a Bruker AVANCE600 instrument. Chemical shifts were reported in ppm for 1 H, 13 C, 19 F, and 31 P NMR. The chemical shifts for the NMR data were referenced as follows: for samples in CDCl 3 , the 1 H NMR was referenced to tetramethylsilane (TMS) at 0.00, and the 13 C NMR was referenced to CDCl 3 at 77.23; for samples in CD 3 OD, the 13 C NMR was referenced to the solvent peak at 49.00; for samples in CD 2 Cl 2 , the 1 H NMR was referenced to the solvent peak at 5.32, and the 13 C NMR was referenced to the solvent peak at 54.00. The chemical shifts for the 31 P NMR spectra were corrected and referenced by using 1 H NMR according to the 2008 IUPAC recommendations. [S1] The data are labeled as follows: chemical shift, multiplicity (s = singlet, d = doublet, t = triplet, q

Research paper thumbnail of Single-crystal-to-single-crystal intercalation of a low-bandgap superatomic crystal

Nature Chemistry, 2017

The controlled introduction of impurities into the crystal lattice of solid-state compounds is a ... more The controlled introduction of impurities into the crystal lattice of solid-state compounds is a cornerstone of materials science. Intercalation, the insertion of guest atoms, ions or molecules between the atomic layers of a host structure, can produce novel electronic, magnetic and optical properties in many materials. Here we describe an intercalation compound in which the host [Co 6 Te 8 (P n Pr 3) 6 ][C 60 ] 3 , formed from the binary assembly of atomically precise molecular clusters, is a superatomic analogue of traditional layered atomic compounds. We find that tetracyanoethylene (TCNE) can be inserted into the superstructure through a single-crystal-to-single-crystal transformation. Using electronic absorption spectroscopy, electrical transport measurements and electronic structure calculations, we demonstrate that the intercalation is driven by the exchange of charge between the host [Co 6 Te 8 (P n Pr 3) 6 ][C 60 ] 3 and the intercalant TCNE. These results show that intercalation is a powerful approach to manipulate the material properties of superatomic crystals.

Research paper thumbnail of The Effect of Thermal Reduction and Film Thickness on fast Response Transparent Graphene Oxide Humidity Sensors

Procedia Engineering, 2016

Resistive chemical sensors were developed having as sensitive film graphene oxide (GO) spin-coate... more Resistive chemical sensors were developed having as sensitive film graphene oxide (GO) spin-coated on glass. Sensor electrical behaviour to room temperature relative humidity was evaluated. High sensitivity characterizes GO sensor. However, it lacks repeatability and long term stability. To this end, we developed spin-coated GO sensors with different active layer thickness, which were subjected to subsequent thermal annealing steps. It was found that the resulting reduced GO (rGO) sensors demonstrate excellent stability compromising, though, the sensitivity which mainly depends on the number of annealing steps and film thickness. Finally, we propose a rapid, transparent, low-power consumption rGO sensor, enabling its use in relevant applications.

Research paper thumbnail of Improving the radiation hardness of graphene field effect transistors

Applied Physics Letters, 2016

Ionizing radiation poses a significant challenge to the operation and reliability of conventional... more Ionizing radiation poses a significant challenge to the operation and reliability of conventional silicon-based devices. Here, we report the effects of gamma radiation on graphene field-effect transistors (GFETs), along with a method to mitigate those effects by developing a radiationhardened version of our back-gated GFETs. We demonstrate that activated atmospheric oxygen from the gamma ray interaction with air damages the semiconductor device, and damage to the substrate contributes additional threshold voltage instability. Our radiation-hardened devices, which have protection against these two effects, exhibit minimal performance degradation, improved stability, and significantly reduced hysteresis after prolonged gamma radiation exposure. We believe this work provides an insight on graphene's interactions with ionizing radiation that could enable future graphene-based electronic devices to be used for space, military, and other radiation-sensitive applications.

Research paper thumbnail of Radiation hardened graphene field effect transistors

2016 74th Annual Device Research Conference (DRC), 2016

Our work demonstrates that both encapsulation and an insulated gate are needed to effectively pro... more Our work demonstrates that both encapsulation and an insulated gate are needed to effectively produce radiation hard GFETs. Our devices successfully mitigate detrimental radiation effects which consists a significant step towards enabling graphene-based electronic devices to be used for space, military, and other radiation sensitive applications.

Research paper thumbnail of Comparison of top- and bottom-contact pentacene field-effect transistors using photocurrent microscopy

2016 74th Annual Device Research Conference (DRC), 2016

Overview Bottom-contact (BC) organic field-effect transistors (OFETs), though more industry-relev... more Overview Bottom-contact (BC) organic field-effect transistors (OFETs), though more industry-relevant than top-contact (TC) OFETs, are prone to low source-drain currents. The underlying mechanisms behind this remain debated. Thus, our work uses photocurrent microscopy (PCM) to examine charge injection in BC and TC geometries. PCM maps were generated first for OFETs with no electrode or gate dielectric treatments. Potential plots were quantitatively derived from the results using a method from previous work. [1] PCM maps were then collected for devices treated with 1. pentafluorobenzenethiol (PFBT), known to improve semiconductor morphology [2], and 2. UV-ozone, which is thought to enhance trap-assisted carrier transport. [3] These treatments were chosen, because they significantly increase source-drain current in BC devices, but in vastly different ways. In addition, unlike other photocurrent studies, we used a range of illumination wavelengths so as to probe various exciton states.

Research paper thumbnail of Photocurrent measurements of pentacene-based devices

Applied Physics Reviews, 2015

Photocurrent spectroscopy (PCS) and photocurrent microscopy (PCM) are powerful tools that can pro... more Photocurrent spectroscopy (PCS) and photocurrent microscopy (PCM) are powerful tools that can probe the underlying mechanisms of charge generation and transport in organic semiconductor devices. There has been significant progress in the use of these techniques, which has yielded a number of insights into the underlying materials and operation of the devices. Despite the potential for PCS and PCM to become standard tools, however, a consensus has not been reached on (1) its uses and (2) the underlying mechanisms which produce the photoresponse. This is particularly true for measurements of pentacene devices, as the energy dynamics of pentacene are complex. Accordingly, here we report the current body of PCS and PCM of pentacene devices, offer interpretations of the data, and discuss which questions remain unanswered. We have divided the reviewed work into four categories based on the goals of the study and the technique used: photocurrent spectroscopy, scanning photocurrent microscopy, mobility, and trap density-of-states.

Research paper thumbnail of Single-polarization, optical low-noise pre-amplified receiver for heavily-coded optical communications links

Free-Space Laser Communication and Atmospheric Propagation XXVII, 2015

We report a single-polarization, optical low-noise pre-amplfier (SP-OLNA) that enhances the recei... more We report a single-polarization, optical low-noise pre-amplfier (SP-OLNA) that enhances the receiver sensitivity of heavily-coded 1.55-μm optical communication links. At channel bit-error ratios of approximately 10%, the erbium-doped SP-OLNA provides an approximately 1.0-dB receiver sensitivity enhancement over a conventional two-polarization pre-amplfier. The SP-OLNA includes three gain stages, each followed by narrow-band athermal fiber Bragg gratings. This cascaded fiter is matched to a return-to-zero, 2.88-Gb/s, variable burst-mode, differential phase shift keying (DPSK) waveform. The SP-OLNA enhancement of approximately 1.0 dB is demonstrated over a range of data rates, from the full 2.88-Gb/s (non-burst) data rate, down to a 1/40th burst rate (72 Mb/s). The SP-OLNA'sfirst stage of ampli_cation is a single-polarization gain block constructed from polarization-maintaining (PM) fiber components, PM erbium gain fiber, and a PM integrated pump coupler and polarizer. This first stage sets the SP-OLNA's noise figure, measured at 3.4 dB. Two subsequent non-PM gain stages allow the SP-OLNA to provide an overall gain of 78 dB to drive a DPSK demodulator receiver. This receiver is comprised of a delay-line interferometer and balanced photo-receiver. The SP-OLNA is packaged into a compact, 5"x7"x1.6" volume, which includes an electronic digital interface to control and monitor pump lasers, optical switches, and power monitors.

Research paper thumbnail of Extensions of quartz-enhanced photoacoustic spectroscopy

The goal of this thesis was to perform quartz-enhanced photoacoustic spectroscopy (QEPAS) on trac... more The goal of this thesis was to perform quartz-enhanced photoacoustic spectroscopy (QEPAS) on trace concentrations of NH 3 in the 1.53 pm region with a DFB laser without the use of a resonating cavity. I analyzed the process of QEPAS both analytically and experimentally. First, absorption spectroscopy was performed with a 1.55 pm DFB laser on the 1558.033 nm absorption line of H 13 C 12 N. The wavelength of the laser radiation was then modulated, and the spectral components of the absorbance were analyzed. In addition, low concentrations of NH 3 were generated through the use of a vaccuum system, and absorption spectoscopy was performed on these samples. A tuning fork was also characterized. Photoacoustic signals were ultimately not realized, however, plans for future work are mentioned.

Research paper thumbnail of An ultra thin implantable system for cerebral blood volume monitoring using flexible OLED and OPD

2015 IEEE International Electron Devices Meeting (IEDM), 2015

An ultra thin implantable system using flexible organic light emitting diodes (OLEDs) and organic... more An ultra thin implantable system using flexible organic light emitting diodes (OLEDs) and organic photodetectors (OPDs) on parylene substrate shows biocompatibility and high conformability on any surface. This system was used to monitor variations in cerebral blood volume (CBV) corresponding to an epileptic seizure, along with baseline signals such as heartbeat, respiration and slow sinusoidal hemodynamic oscillations (SSHOs). As such, this system shows strong potential for implantable and/or wearable biosensors for continuous health monitoring.