Scholars@Duke
Charles Parker

Charles Parker

Senior Laboratory Administrator
Electrical and Computer Engineering
charles.parker@duke.edu
Box 90291, Durham, NC
100 Science Drive, 130 Hudson Hall, Box 90291, Durham, NC 27708

Selected Publications

Spectral Reconstruction Improvement in a Cycloidal Coded-Aperture Mass Spectrometer.

Journal Article Journal of the American Society for Mass Spectrometry · May 2024 Spatial aperture coding is a technique used to improve throughput without sacrificing resolution both in optical spectroscopy and sector mass spectrometry (MS). Previous work demonstrated that aperture coding combined with a position-sensitive array detect ... Full text Cite

Proof-of-Concept Vacuum Microelectronic NOR Gate Fabricated Using Microelectromechanical Systems and Carbon Nanotube Field Emitters.

Journal Article Micromachines · April 2023 This paper demonstrates a fully integrated vacuum microelectronic NOR logic gate fabricated using microfabricated polysilicon panels oriented perpendicular to the device substrate with integrated carbon nanotube (CNT) field emission cathodes. The vacuum mi ... Full text Cite

The influence of light incidence on the bipolar switching in the two-terminal devices with n-ZnO and p-SrCu2O2 films

Journal Article Applied Physics A: Materials Science and Processing · January 1, 2023 The interaction of light with the bipolar characteristics of two-terminal devices synthesized with ZnO film is investigated. Three types of devices are built. The first set consisted of devices with n-ZnO film on SiO2/Si or sapphire substrate. The second s ... Full text Cite

A super-resolution proof of concept in a cycloidal coded aperture miniature mass spectrometer.

Journal Article Rapid communications in mass spectrometry : RCM · January 2023 RationaleHigher resolution in fieldable mass spectrometers (MS) is desirable in space flight applications to enable resolving isobaric interferences at m/z < 60 u. Resolution in portable cycloidal MS coupled with array detectors could be improved ... Full text Cite

Design considerations for a cycloidal mass analyzer using a focal plane array detector.

Journal Article Journal of mass spectrometry : JMS · July 2022 With the advent of technologies such as ion array detectors and high energy permanent magnet materials, there is renewed interest in the unique focusing properties of the cycloidal mass analyzer and its ability to enable small, high-resolution, and high-se ... Full text Cite

Virtual-slit focusing in a cycloidal mass spectrometer – A proof of concept

Journal Article International Journal of Mass Spectrometry · December 1, 2021 This work demonstrates a novel approach to mass spectrometry using the “virtual-slit” created by the small, localized volume from which ions are generated by localized ionization techniques such as laser ionization of particles and surfaces, and spark ioni ... Full text Cite

The Long Neglected Cycloidal Mass Analyzer.

Journal Article Analytical chemistry · August 2021 In 1938, Walker Bleakney and John A. Hipple first described the cycloidal mass analyzer as the only mass analyzer configuration capable of "perfect" ion focusing. Why has their geometry been largely neglected for many years and how might it earn a respecta ... Full text Cite

Improving the Performance of a Cycloidal Coded-Aperture Miniature Mass Spectrometer.

Journal Article Journal of the American Society for Mass Spectrometry · February 2021 Cycloidal sector mass analyzers have, in principle, perfect focusing due to perpendicularly oriented uniform electric and magnetic fields, making them ideal candidates for incorporation of spatially coded apertures. We have previously demonstrated a proof- ... Full text Cite

4D Printing of Stretchable Supercapacitors via Hybrid Composite Materials

Journal Article Advanced Materials Technologies · January 1, 2021 Stretchable supercapacitors (SCs) have attracted significant attention in developing power-independent stretchable electronic systems due to their intrinsic energy storage function and unique mechanical properties. Most current SCs are generally limited by ... Full text Cite

Comparison of thermionic filament and carbon nanotube field emitter-based electron ionization sources in cycloidal coded aperture mass analyzers

Journal Article International Journal of Mass Spectrometry · November 1, 2020 This work compares the coded aperture imaging performance of thermionic filament and carbon nanotube (CNT) field emitter-based electron sources in cycloidal-coded aperture mass spectrometers. The use of spatially coded apertures in mass spectrometry enable ... Full text Cite

A novel sector mass spectrograph design for high-order coded aperture Mass Spectrometry with stigmatic aberration correction

Journal Article International Journal of Mass Spectrometry · September 1, 2020 Previous works experimentally demonstrated that the application of spatially-coded apertures to simple sector mass spectrographs can result in increased signal intensity while maintaining spectral resolution comparable to that of a conventional slit apertu ... Full text Cite

High current density electron emission from an electrodeposited metal nanowire array

Journal Article Journal of Vacuum Science and Technology B · July 1, 2020 High-current electron field emitters are of interest for many applications, but state-of-the-art devices suffer from limitations such as high turn-on macroscopic field, low macroscopic current density, poor emission stability, and short lifetime. Field emi ... Full text Cite

Robust and High-Performance Electrodes via Crumpled Au-CNT Forests for Stretchable Supercapacitors

Journal Article Matter · May 6, 2020 Stretchable supercapacitors based on vertically aligned nanotubes or nanowires have attracted considerable attention because of their improved robustness and electrochemical performance under large and repeated deformations. Here, we demonstrate a robust a ... Full text Cite

Ti3C2Tx MXene-Reduced Graphene Oxide Composite Electrodes for Stretchable Supercapacitors.

Journal Article ACS nano · March 2020 The development of stretchable electronics requires the invention of compatible high-performance power sources, such as stretchable supercapacitors and batteries. In this work, two-dimensional (2D) titanium carbide (Ti3C2Tx Full text Cite

Transparent mxene-polymer supercapacitive film deposited using rir-maple

Journal Article Crystals · March 1, 2020 In this work, resonant infrared matrix-assisted pulsed laser evaporation (RIR-MAPLE), a novel deposition technique, was used to produce a transparent composite electrode of polyflourene (PFO) and two-dimensional (2D) Ti3C2Tx nanosheets, which are part of t ... Full text Cite

Deactivation of ascaris suum eggs using electroporation and sequential inactivation with chemical disinfection

Journal Article Journal of Water Sanitation and Hygiene for Development · January 1, 2020 Electroporation has been evaluated as a potential backend wastewater treatment for deactivation of Ascaris suum eggs in buffer solution. Initial results indicate that eggshell permeability is affected by the pulse train electric field strength and duration ... Full text Cite

Highly Stretchable Supercapacitors via Crumpled Vertically Aligned Carbon Nanotube Forests

Journal Article Advanced Energy Materials · June 12, 2019 Stretchable supercapacitors have received increasing attention due to their broad applications in developing self-powered stretchable electronics for wearable electronics, epidermal and implantable electronics, and biomedical devices that are capable of su ... Full text Cite

Reduction in energy for electrochemical disinfection of E. coli in urine simulant.

Journal Article Journal of applied electrochemistry · January 2019 AbstractWe report the development of novel modes of operation for electrochemical disinfection of E. coli in human urine simulant with an aim to minimize the energy required for disinfection. The system employs boron-doped diamond electrode ... Full text Cite

Electropermeabilization of nematode eggs for parasite deactivation.

Journal Article Journal of water, sanitation, and hygiene for development : a journal of the International Water Association · January 2019 The eggs of parasitic helminth worms are incredibly resilient - possessing the ability to survive changing environmental factors and exposure to chemical treatments - which has restricted the efficacy of wastewater sanitation. This research reports on the ... Full text Cite

Prototype coded aperture miniature mass spectrometer for environmental sensing

Conference AQM 2019 - Air Quality Measurement Methods and Technology Conference 2019 · January 1, 2019 © 2019 Air and Waste Management Association. All rights reserved. In summary, this paper shows the design and initial performance characterization of a coded aperture miniature mass spectrometer for environmental sensing (CAMMS-ES). CAMMS-ES incorporates s ... Cite

Prototype coded aperture miniature mass spectrometer for environmental sensing

Conference AQM 2019 - Air Quality Measurement Methods and Technology Conference 2019 · January 1, 2019 In summary, this paper shows the design and initial performance characterization of a coded aperture miniature mass spectrometer for environmental sensing (CAMMS-ES). CAMMS-ES incorporates spatial aperture coding to break the throughput vs. resolution trad ... Cite

Improved blackwater disinfection using potentiodynamic methods with oxidized boron-doped diamond electrodes.

Journal Article Water research · September 2018 Electrochemical disinfection (ECD) has become an important blackwater disinfection technology. ECD is a promising solution for the 2 billion people without access to conventional sanitation practices and in areas deficient in basic utilities (e.g., sewers, ... Full text Cite

Proof of Concept Coded Aperture Miniature Mass Spectrometer Using a Cycloidal Sector Mass Analyzer, a Carbon Nanotube (CNT) Field Emission Electron Ionization Source, and an Array Detector.

Journal Article Journal of the American Society for Mass Spectrometry · February 2018 Despite many potential applications, miniature mass spectrometers have had limited adoption in the field due to the tradeoff between throughput and resolution that limits their performance relative to laboratory instruments. Recently, a solution to this tr ... Full text Cite

Effects of Magnetic and Electric Field Uniformity on Coded Aperture Imaging Quality in a Cycloidal Mass Analyzer.

Journal Article Journal of the American Society for Mass Spectrometry · February 2018 Cycloidal mass analyzers are unique sector mass analyzers as they exhibit perfect double focusing, making them ideal for incorporating spatial aperture coding, which can increase the throughput of a mass analyzer without affecting the resolving power. Howe ... Full text Cite

Efficient and Stable Pt/TiO2/CdS/Cu2BaSn(S,Se)4 Photocathode for Water Electrolysis Applications

Journal Article ACS Energy Letters · January 12, 2018 The Cu2BaSnS4-xSex (CBTSSe) system has attracted remarkable attention as an emerging chalcogenide semiconductor with desirable electronic and optical properties for solar energy conversion applications. The current study combines sputtered band gap-tailore ... Full text Cite

A miniature electron ionization source fabricated using microelectromechanical systems (MEMS) with integrated carbon nanotube (CNT) field emission cathodes and low-temperature co-fired ceramics (LTCC)

Journal Article International Journal of Mass Spectrometry · November 1, 2017 The use of microelectromechanical systems (MEMS) components in miniature mass spectrometers is particularly attractive due to their small size and scalable manufacturing capability. Our group has pioneered the development of miniature electron ionization s ... Full text Cite

Coded Apertures in Mass Spectrometry.

Journal Article Annual review of analytical chemistry (Palo Alto, Calif.) · June 2017 The use of coded apertures in mass spectrometry can break the trade-off between throughput and resolution that has historically plagued conventional instruments. Despite their very early stage of development, coded apertures have been shown to increase thr ... Full text Cite

Enhanced H2O2 Production at Reductive Potentials from Oxidized Boron-Doped Ultrananocrystalline Diamond Electrodes.

Journal Article ACS applied materials & interfaces · May 2017 This work investigates the surface chemistry of H2O2 generation on a boron-doped ultrananocrystalline diamond (BD-UNCD) electrode. It is motivated by the need to efficiently disinfect liquid waste in resource constrained environments ... Full text Cite

Integrating carbon nanotube forests into polysilicon MEMS: Growth kinetics, mechanisms, and adhesion

Journal Article Carbon · March 1, 2017 The growth of carbon nanotubes (CNTs) on polycrystalline silicon substrates was studied to improve the design of CNT field emission sources for microelectromechanical systems (MEMS) applications and vacuum microelectronic devices (VMDs). Microwave plasma-e ... Full text Cite

Improved Performance of Field Emission Vacuum Microelectronic Devices for Integrated Circuits

Journal Article IEEE Transactions on Electron Devices · September 1, 2016 The movement from discrete transistors to integrated silicon circuits led to the rapid evolution of microscale electronics, but there has been no equivalent transition for the vacuum tube transistor. Difficulty integrating devices at microscales has hinder ... Full text Cite

Compatibility of Spatially Coded Apertures with a Miniature Mattauch-Herzog Mass Spectrograph.

Journal Article Journal of the American Society for Mass Spectrometry · April 2016 In order to minimize losses in signal intensity often present in mass spectrometry miniaturization efforts, we recently applied the principles of spatially coded apertures to magnetic sector mass spectrometry, thereby achieving increases in signal intensit ... Full text Cite

Protocol for High-Sensitivity Surface Area Measurements of Nanostructured Films Enabled by Atomic Layer Deposition of TiO2

Journal Article Journal of Physical Chemistry C · November 19, 2015 Due to their nanoscale dimensions, nanomaterials possess a very high specific surface area, which directly informs their properties in energy conversion and storage and catalytic chemical transformation, among other applications. However, common laboratory ... Full text Cite

Chemical ionization mass spectrometry using carbon nanotube field emission electron sources.

Journal Article Journal of the American Society for Mass Spectrometry · November 2015 A novel chemical ionization (CI) source has been developed based on a carbon nanotube (CNT) field emission electron source. The CNT-based electron source was evaluated and compared with a standard filament thermionic electron source in a commercial explosi ... Full text Cite

Achieving Excellence in Graduate Research: A Guide for New Graduate Students.

Journal Article Advanced science (Weinheim, Baden-Wurttemberg, Germany) · October 2015 A mentoring guide for incoming graduate students has been developed to minimize the time spent reiterating general guidance and "norms" that need to be instilled in new graduate students. This allows principal investigators and senior researchers to ... Full text Cite

Order of Magnitude Signal Gain in Magnetic Sector Mass Spectrometry Via Aperture Coding.

Journal Article Journal of the American Society for Mass Spectrometry · September 2015 Miniaturizing instruments for spectroscopic applications requires the designer to confront a tradeoff between instrument resolution and instrument throughput [and associated signal-to-background-ratio (SBR)]. This work demonstrates a solution to this trade ... Full text Cite

Role of nanocrystalline domain size on the electrochemical double-layer capacitance of high edge density carbon nanostructures

Journal Article MRS Communications · June 1, 2015 Nanostructured carbon materials, especially activated carbon, carbon nanotubes, and graphene, have been widely studied for supercapacitor applications. To maximize the efficacy of these materials for electrochemical energy storage, a detailed understanding ... Full text Cite

Optimization of active manganese oxide electrodeposits using graphenated carbon nanotube electrodes for supercapacitors

Journal Article Chemistry of Materials · April 14, 2015 Graphenated carbon nanotubes (g-CNTs) were investigated as the electrode support in MnO2 composite cathodes for aqueous asymmetric supercapacitors. The electrode performance could be tuned by optimizing the density of graphene foliates on the g- ... Full text Cite

Eliminating proximity effects and improving transmission in field emission vacuum microelectronic devices for integrated circuits

Conference Technical Digest - International Electron Devices Meeting, IEDM · February 16, 2015 This work evaluates crosstalk and transmission efficiency in multi-integrated field emission vacuum microelectronic devices (FE-VMDs). Experimental evidence showed that proximity effects cannot be neglected, therefore indicating a need for additional contr ... Full text Cite

Two-dimensional aperture coding for magnetic sector mass spectrometry.

Journal Article Journal of the American Society for Mass Spectrometry · February 2015 In mass spectrometer design, there has been a historic belief that there exists a fundamental trade-off between instrument size, throughput, and resolution. When miniaturizing a traditional system, performance loss in either resolution or throughput would ... Full text Cite

Diamond for biosensing: Electrochemical detection of NOx species with thiol-amine functionalized diamond

Journal Article Journal of the Electrochemical Society · January 1, 2015 Diamond has long been of interest as a biomaterial due to its expected biocompatibility and chemical stability. Progress in surface functionalization of diamond and diamond electrochemistry has extended this interest to use as a biosensor platform. The sen ... Full text Cite

Enhanced electron transfer kinetics through hybrid graphene-carbon nanotube films.

Journal Article Electrochemistry communications · November 2014 We report the first study of the electrochemical reactivity of a graphenated carbon nanotube (g-CNT) film. The electron transfer kinetics of the ferri-ferrocyanide couple were examined for a g-CNT film and compared to the kinetics to standard carbon nanotu ... Full text Cite

Perspectives on the Growth of High Edge Density Carbon Nanostructures: Transitions from Vertically Oriented Graphene Nanosheets to Graphenated Carbon Nanotubes.

Journal Article The journal of physical chemistry. C, Nanomaterials and interfaces · July 2014 Insights into the growth of high edge density carbon nanostructures were achieved by a systematic parametric study of plasma-enhanced chemical vapor deposition (PECVD). Such structures are important for electrode performance in a variety of applications su ... Full text Cite

Diamond surface functionalization with biomimicry - Amine surface tether and thiol moiety for electrochemical sensors

Journal Article Applied Surface Science · May 15, 2014 The surface of conducting diamond was functionalized with a terminal thiol group that is capable of binding and detecting nitrogen-oxygen species. The functionalization process employed multiple steps starting with doped diamond films grown by plasma enhan ... Full text Cite

Platform for integrated vacuum microelectronic circuits

Conference IEEE International Vacuum Electronics Conference, IVEC 2014 · January 1, 2014 Vacuum devices are preferred to solid-state for applications requiring radiation stability, a wide range in operating temperature, or high power at high frequency. However, difficulties associated with integrating these devices on the microscale have limit ... Full text Cite

Disinfection of E. coli contaminated urine using boron-doped diamond electrodes

Journal Article Journal of the Electrochemical Society · January 1, 2014 We report the development of an electrochemical disinfection system for human urine, which does not require the addition of any external water or chemical reagents. It is designed to minimize energy consumption so that it may be powered from point-of-use s ... Full text Cite

Electrochemical disinfection of human urine for water-free and additive-free toilets using boron-doped diamond electrodes

Journal Article ECS Transactions · January 1, 2013 We report the development of an electrochemical disinfection system for human urine, which does not require the addition of any external water or chemical reagents. It is designed to minimize energy consumption so that it may derive its energy from solar p ... Full text Cite

Electrochemical charge storage properties of vertically aligned carbon nanotube films: Effects of thermal oxidation

Journal Article Journal of Physical Chemistry C · September 13, 2012 Vertically aligned carbon nanotube (VACNT) films were synthesized and investigated in vitro for their potential use as a neural stimulation electrode. Materials and electrochemical (EC) characterization (cyclic voltammetry, electrochemical impedance spectr ... Full text Cite

Modeling operational modes of a bipolar vacuum microelectronic device

Journal Article IEEE Electron Device Letters · August 27, 2012 Vacuum microelectronic devices (VMDs) designed for bipolar charge operation hold great promise for applications in radiation-intensive and high-temperature environments. This novel class of devices was first realized in a microelectromechanical platform le ... Full text Cite

Three-dimensional arrays of graphenated carbon nanotubes

Journal Article Journal of Materials Research · April 14, 2012 Graphene and carbon nanotubes (CNTs) are fascinating materials, both scientifically and technologically, due to their exceptional properties and potential use in applications ranging from high-frequency electronics to energy storage devices. This manuscrip ... Full text Cite

Graphenated carbon nanotubes for enhanced electrochemical double layer capacitor performance

Journal Article Applied Physics Letters · October 2011 This letter reports on nucleation and growth of graphene foliates protruding from the sidewalls of aligned carbon nanotubes (CNTs) and their impact on the electrochemical double-layer capacitance. Arrays of CNTs were grown for different time intervals, res ... Open Access Cite

A Bipolar Vacuum Microelectronic Device

Journal Article Ieee Transactions on Electron Devices · September 2011 Cite

Carbon Nanotube Electron Ionization Source for Portable Mass Spectrometry

Journal Article Analytical Chemistry · September 2011 Cite

The effect of gold on platinum oxidation in homogeneous Au-Pt electrocatalysts

Journal Article Applied Surface Science · December 2010 Cite

Analysis of 3-panel and 4-panel microscale ionization sources

Journal Article Journal of Applied Physics · June 2010 Open Access Cite

Influence of Al-doping and oxygen partial pressure on the optical properties of ZnO films

Journal Article Nanotechnology 2009: Fabrication, Particles, Characterization, MEMS, Electronics and Photonics - Technical Proceedings of the 2009 NSTI Nanotechnology Conference and Expo, NSTI-Nanotech 2009 · November 26, 2009 Al-doped ZnO (ZnO:Al) thin films were deposited on glass substrates using the radio frequency reactive magnetron sputtering technique. The effects of Al concentrations and oxygen partial pressures on the microstructurc and the luminescence properties of th ... Cite

Simulation and testing of a lateral, microfabricated electron-impact ion source

Journal Article Applied Physics Letters · January 2009 Cite

High voltage MEMS platform for fully integrated, on-chip, vacuum electronic devices

Journal Article 2008 IEEE International Vacuum Electronics Conference, IVEC with 9th IEEE International Vacuum Electron Sources Conference, IVESC · September 15, 2008 We demonstrate a fully integrated, on-chip, vacuum microtriode capable of handling voltages up to 800 V. The ability to operate at such high voltages is achieved by the addition of a 10 μm-thick silicon dioxide layer to the device. The device is fabricated ... Full text Cite

Measurement of reactive and condensable gas permeation using a mass spectrometer

Journal Article Journal of Vacuum Science \& Technology a · September 2008 Cite

High voltage microelectromechanical systems platform for fully integrated, on-chip, vacuum electronic devices

Journal Article Applied Physics Letters · June 2008 We demonstrate a fully integrated, on-chip, vacuum microtriode capable of handling voltages up to 800 V. The ability to operate at such high voltages is achieved by the addition of a 10 mu m thick silicon dioxide layer to the device. The device is fabricat ... Cite

A novel ion source and detector for a miniature mass spectrometer

Journal Article Proceedings of IEEE Sensors · December 1, 2007 Due to its flexibility and sensitivity, mass spectrometry is a preferred sensing method for applications ranging from explosives detection to air quality monitoring. The key functional elements of a mass spectrometer are ionization, mass separation, and io ... Full text Cite

On-chip electron-impact ion source using carbon nanotube field emitters

Journal Article Applied Physics Letters · March 2007 A lateral on-chip electron-impact ion source utilizing a carbon nanotube field emission electron source was fabricated and characterized. The device consists of a cathode with aligned carbon nanotubes, a control grid, and an ion collector electrode. The el ... Full text Open Access Link to item Cite

High sensitivity permeation measurement system for "ultrabarrier" thin films

Journal Article Journal Of Vacuum Science \& Technology A · 2007 The authors demonstrate a new technique for high sensitivity gas permeation measurements by integrating mass spectrometry with programed accumulation, detection, and evacuation of permeant. After passing through the film of interest, the gas permeant is ca ... Cite

High voltage compatible micromachined vacuum electronic devices with carbon nanotube cold cathodes

Journal Article 2006 IEEE International Vacuum Electronics Conference held jointly with 2006 IEEE International Vacuum Electron Sources, IVEC/IVESC 2006 · December 1, 2006 Previously, Bower et al. [1] demonstrated a microfabricated vacuum microtriode with an integrated carbon nanotube field emission cathode. One of the main limitations of the microtriode was the inadequate device insulation which suffered from leakage curren ... Cite