Max Chung - Academia.edu (original) (raw)

Papers by Max Chung

Nanoimprint lithography (NIL) is an emerging low cost technique for reproducing sub-45 nm pattern... more Nanoimprint lithography (NIL) is an emerging low cost technique for reproducing sub-45 nm pattern in various applications; however, manufacturing the mold for nanoimprint has been a key challenge in expense and resolution. Focused Ion Beams (FIB) has been known for high resolution but low throughput work in TEM sample preparation, and its extremely well defined 7 nm diameter Ga + beam make it also a suitable tool for mold manufacturing for nanoimprint, which enable mass reproduction of the FIB work. We find features down to 30 nm can be made with FIB, the actual line width to beam diameter ratio is around 5-6 for an aspect ratio less than 2. A higher than 2 aspect ratio may result in re-deposition of the milled out substrate. Re-deposition can be reduced by a shorter dwell time or gas-assisted etching. There is a trade off between dwell time and feature integrity. Best results can be achieved with high hardness materials; the lack of conductivity for some materials can be remedied with s thin layer of Pt coating on the surface before FIB jobs.

2008 IEEE International Power Modulators and High-Voltage Conference, 2008

Atmospheric pressure plasma (APP) is gaining many grounds in surface modification, photo resist c... more Atmospheric pressure plasma (APP) is gaining many grounds in surface modification, photo resist cleaning, medical instrument decontamination, and air pollution control. Previous simulation results were performed mostly with fluid simulations, in which potential profile, electron temperature, and plasma chemistry are available, but lack the details in field emission, secondary electrons, and space charge effect which is important in high pressure plasma. On the other hand, Particle-In-Cell simulation is time consuming. We try to perform a simulation on APP source with MAGIC code, and direct the plasma towards a surface that is to be modified and observe the effect of applied voltage, flow speed, field emission, secondary electrons, Electron Energy Distribution Function (EEDF) and ion temperature. We separate these effects into different simulations, and plasma chemistry is ignored. Simulation results indicate just these particle simulation can reveal many useful insight into operations of an APP source on surface.

2005 IEEE Pulsed Power Conference, 2005

Previously we reported a novel gas discharge closing switch termed Electrostatic Plasma Injection... more Previously we reported a novel gas discharge closing switch termed Electrostatic Plasma Injection Switch (EPIS) with which uses transmission line reflections of incoming trigger pulse to generate voltage gradients on a vertical multi-sections trigger structure that extends from a hollow cathode into a symmetrical hollow anode. Low current pre-ionization glow discharge exterior to the hollow cathode provides seed electrons for fast turn-on. The trigger structure attracts plasma into the hollow cathode, and then accelerates plasma vertically upward into the gap between anode and cathode. A Pseudospark like super-dense glow discharge plasma initiates the high current. This prototype EPIS has one disadvantage: there are two modes of operation, normal and abnormal modes. Now we propose a further improvement termed Insulated EPIS (IEPIS), which has an insulated trigger structure that can ensure EPIS operates in the normal mode, which means breakdown occurs only between anode and cathode, and not between anode and pre-ionization area or anode and the trigger. This operational principle of IEPIS is very similar to MOSFET in electronics. IEPIS is expected to have higher repetition rates with enhanced reliability, and consume less power to trigger. We present a MAGIC simulation of its space charge evolution, electron density distributions evolution, and electron velocity distribution in various stages of IEPIS.

Nanotechnology, 2009

Nanoparticles added into nanofibers produced by electrospinning can expand the functions of such ... more Nanoparticles added into nanofibers produced by electrospinning can expand the functions of such fibers, and these nanoparticles can serve as vehicle for drugs in active drug delivery (ADR) concept. Depending on the toxicity of these nanoparticles, sometime it is desirable to cover toxic ones inside a polymer while benign ones exposed, and release them at programmed time and locations. We achieve this control of nanoparticle position on electrospun nanofiber with magnetism assisted electrospinning. Two horizontal magnet is placed at the receptor position, and nonmagnetic, superparamagnetic, and paramagnetic nanoparticles of Ag, Fe 3 O 4 (<20 nm), Fe 3 O 4 (>30 nm) were added inside PVP solutions in electrospinning process. We found the nonmagnetic Ag and superparamagnetic Fe 3 O 4 nanoparticles exist inside the nanofiber, while paramagnetic Fe 3 O 4 nanoparticles exist mainly on the surface of nanofibers. The interaction of the magnetic field and the paramagnetic Fe 3 O 4 nanoparticles at the final stage of nanofiber formation makes this possible.

Summary form only given. Spark gap is used extensively in all kinds of pulse generators, traditio... more Summary form only given. Spark gap is used extensively in all kinds of pulse generators, traditional Trigatron type spark gap relies on a pulsed high voltage (usually around 30 % of hold off voltage) to trigger the main gap breakdown. The statistical delay is inversely proportional to pressure and related to streamer propagation time. On the other hand, laser triggered spark gap require high cost YAG laser to provide very strong intensity (~109 W/cm2, tens of mJ energy) to ionize SF6 or air to initiate breakdown. UV flash lamp has also been used to trigger Thyratron in Back Light Thyratron (BLT). The emergence of high power (1-3 W) U V LED presents a new opportunity in triggering a spark gap. LED is compact, low cost, low voltage, and with very low jitter. One or several UV LEDs are positioned in the center of a Trigatron type spark gap to initiate the main discharge. Preliminary results of breakdown waveform and delay are discussed.

TENCON, IEEE Region 10 International Conference, 2007

Plasma antenna has unique properties like low RCS and variable impedance; however, previous plasm... more Plasma antenna has unique properties like low RCS and variable impedance; however, previous plasma antenna uses 500 MHz RF power to generate a plasma column, which is limited in energy efficiency and bandwidth. Here we introduce a new type of plasma antenna that generates plasma column with pre-ionization from a DC high voltage, and signal is coupled to the plasma

Magnetic nanoparticles (MNPs) are a class of nanoparticles, which can be manipulated using magnet... more Magnetic nanoparticles (MNPs) are a class of nanoparticles, which can be manipulated using magnetic fields. Currently, MNPs are recognized as one of the most important mode as a drug carrier while they can also be potentially used as carriers for gene delivery. In this article, magnetic nanostructured lipid carriers (mNLCs) are prepared through co-precipitation method. The particle size and zeta potential, structure and thermal properties of the MNPS have been studied. The produced MNPs were also hydrophobically modified with a long chain of fatty acid namely lauric acid. These modified MNPs were mixed with nanostructured lipid carriers (NLCs) to form mNLCs. The heat capacity and flow of mNLCs was profligate in the presence of a magnetic field which is a worthy attribute for targeted drug delivery applications.

Carbon nanotube (CNT) is the primary field emission source in many new applications, but there ha... more Carbon nanotube (CNT) is the primary field emission source in many new applications, but there have been limited reports on direct growth of CNT on metal surface with CVD method with good electrical contact and surface adhesion [1]. We propose the use of BGA balls to bond CNTs grown with CVD method on Si wafer onto a metal substrate and form a grid array of emission source. Because of the low melting point (185oC) of the BGA ball and its highly matured low cost production technique and physical properties compatible with the IC packing industry, this method can manufacture very large area of metal-CNT cathode with excellent field emission characteristics. Multiple samples of such cathode show turn on field (definedat 1μA/cm current density) from 1.051.48 V/μm, and field enhancement factor β ranging from 2500-3200. Optimum bonding time for this CNT growth condition at 63 MPa pressure is around 90 seconds.

Nanoimprint lithography (NIL) is an emerging low cost technique for reproducing sub-45 nm pattern... more Nanoimprint lithography (NIL) is an emerging low cost technique for reproducing sub-45 nm pattern in various applications; however, manufacturing the mold for nanoimprint has been a key challenge in expense and resolution. Focused Ion Beams (FIB) has been known for high resolution but low throughput work in TEM sample preparation, and its extremely well defined 7 nm diameter Ga beam make it also a suitable tool for mold manufacturing for nanoimprint, which enable mass reproduction of the FIB work. We find features down to 30 nm can be made with FIB, the actual line width to beam diameter ratio is around 5-6 for an aspect ratio less than 2. A higher than 2 aspect ratio may result in re-deposition of the milled out substrate. Re-deposition can be reduced by a shorter dwell time or gas-assisted etching. There is a trade off between dwell time and feature integrity. Best results can be achieved with high hardness materials; the lack of conductivity for some materials can be remedied wit...

Electrospinning produces nanofibers with diameters ranging from 200-500 nm under 10-20 KV at 10-2... more Electrospinning produces nanofibers with diameters ranging from 200-500 nm under 10-20 KV at 10-20 cm distances, and if these nanofibers were composed of polymers like PVA or PVP, they are usually nonconductive with resistances too larger to measure on ordinary meter. One way to change the conductivity of nanofibers is to add nanoparticles. We produce Fe3O4 nanoparticles with polyols method, and mix these diameters ranging from 2050 nm nanoparticles with PVP into electrospinning process on a double knife edge receptor set up. We found the current between the two knife edges of 0.005 g of nanofibers and nanoparticles is around 20 nA at 50 V bias, and based on estimations of nanofiber diameter and number, the resistance of each individual nanoparticles containing nanofibers can be estimated.

2017 IEEE International Conference on Plasma Science (ICOPS), 2017

Photonic crystal produces bandgaps with its periodic structure, where electromagnetic waves under... more Photonic crystal produces bandgaps with its periodic structure, where electromagnetic waves undergo multiple reflections and constructive or destructive combinations, but their properties are usually not adjustable. Plasma photonic crystal on the other hand can provide some degree of transmission characteristic adjustment. Radar cross section (RCS) is a strong function of shape, and plasma can also affect RCS via absorption or scattering. For these reasons, we constructed a wedge shape plasma photonic crystal which is composed of 27 glass tubes with 12 mm diameter, and inside is filled with plasma. In this article we show the FDTD simulation results of the near fields of this device, and its RCS. We found only minor changes in the RCS of the plasma photonic crystal device with or without plasma, but substantial changes in the near field distribution behind this device. The transmission is very sensitive to plane wave incidence angle. The influence of plasma density is also presented.

Nanoimprint lithography (NIL) is an emerging low cost technique for reproducing sub-45 nm pattern... more Nanoimprint lithography (NIL) is an emerging low cost technique for reproducing sub-45 nm pattern in various applications; however, manufacturing the mold for nanoimprint has been a key challenge in expense and resolution. Focused Ion Beams (FIB) has been known for high resolution but low throughput work in TEM sample preparation, and its extremely well defined 7 nm diameter Ga + beam make it also a suitable tool for mold manufacturing for nanoimprint, which enable mass reproduction of the FIB work. We find features down to 30 nm can be made with FIB, the actual line width to beam diameter ratio is around 5-6 for an aspect ratio less than 2. A higher than 2 aspect ratio may result in re-deposition of the milled out substrate. Re-deposition can be reduced by a shorter dwell time or gas-assisted etching. There is a trade off between dwell time and feature integrity. Best results can be achieved with high hardness materials; the lack of conductivity for some materials can be remedied with s thin layer of Pt coating on the surface before FIB jobs.

2008 IEEE International Power Modulators and High-Voltage Conference, 2008

Atmospheric pressure plasma (APP) is gaining many grounds in surface modification, photo resist c... more Atmospheric pressure plasma (APP) is gaining many grounds in surface modification, photo resist cleaning, medical instrument decontamination, and air pollution control. Previous simulation results were performed mostly with fluid simulations, in which potential profile, electron temperature, and plasma chemistry are available, but lack the details in field emission, secondary electrons, and space charge effect which is important in high pressure plasma. On the other hand, Particle-In-Cell simulation is time consuming. We try to perform a simulation on APP source with MAGIC code, and direct the plasma towards a surface that is to be modified and observe the effect of applied voltage, flow speed, field emission, secondary electrons, Electron Energy Distribution Function (EEDF) and ion temperature. We separate these effects into different simulations, and plasma chemistry is ignored. Simulation results indicate just these particle simulation can reveal many useful insight into operations of an APP source on surface.

2005 IEEE Pulsed Power Conference, 2005

Previously we reported a novel gas discharge closing switch termed Electrostatic Plasma Injection... more Previously we reported a novel gas discharge closing switch termed Electrostatic Plasma Injection Switch (EPIS) with which uses transmission line reflections of incoming trigger pulse to generate voltage gradients on a vertical multi-sections trigger structure that extends from a hollow cathode into a symmetrical hollow anode. Low current pre-ionization glow discharge exterior to the hollow cathode provides seed electrons for fast turn-on. The trigger structure attracts plasma into the hollow cathode, and then accelerates plasma vertically upward into the gap between anode and cathode. A Pseudospark like super-dense glow discharge plasma initiates the high current. This prototype EPIS has one disadvantage: there are two modes of operation, normal and abnormal modes. Now we propose a further improvement termed Insulated EPIS (IEPIS), which has an insulated trigger structure that can ensure EPIS operates in the normal mode, which means breakdown occurs only between anode and cathode, and not between anode and pre-ionization area or anode and the trigger. This operational principle of IEPIS is very similar to MOSFET in electronics. IEPIS is expected to have higher repetition rates with enhanced reliability, and consume less power to trigger. We present a MAGIC simulation of its space charge evolution, electron density distributions evolution, and electron velocity distribution in various stages of IEPIS.

Nanotechnology, 2009

Nanoparticles added into nanofibers produced by electrospinning can expand the functions of such ... more Nanoparticles added into nanofibers produced by electrospinning can expand the functions of such fibers, and these nanoparticles can serve as vehicle for drugs in active drug delivery (ADR) concept. Depending on the toxicity of these nanoparticles, sometime it is desirable to cover toxic ones inside a polymer while benign ones exposed, and release them at programmed time and locations. We achieve this control of nanoparticle position on electrospun nanofiber with magnetism assisted electrospinning. Two horizontal magnet is placed at the receptor position, and nonmagnetic, superparamagnetic, and paramagnetic nanoparticles of Ag, Fe 3 O 4 (<20 nm), Fe 3 O 4 (>30 nm) were added inside PVP solutions in electrospinning process. We found the nonmagnetic Ag and superparamagnetic Fe 3 O 4 nanoparticles exist inside the nanofiber, while paramagnetic Fe 3 O 4 nanoparticles exist mainly on the surface of nanofibers. The interaction of the magnetic field and the paramagnetic Fe 3 O 4 nanoparticles at the final stage of nanofiber formation makes this possible.

Summary form only given. Spark gap is used extensively in all kinds of pulse generators, traditio... more Summary form only given. Spark gap is used extensively in all kinds of pulse generators, traditional Trigatron type spark gap relies on a pulsed high voltage (usually around 30 % of hold off voltage) to trigger the main gap breakdown. The statistical delay is inversely proportional to pressure and related to streamer propagation time. On the other hand, laser triggered spark gap require high cost YAG laser to provide very strong intensity (~109 W/cm2, tens of mJ energy) to ionize SF6 or air to initiate breakdown. UV flash lamp has also been used to trigger Thyratron in Back Light Thyratron (BLT). The emergence of high power (1-3 W) U V LED presents a new opportunity in triggering a spark gap. LED is compact, low cost, low voltage, and with very low jitter. One or several UV LEDs are positioned in the center of a Trigatron type spark gap to initiate the main discharge. Preliminary results of breakdown waveform and delay are discussed.

TENCON, IEEE Region 10 International Conference, 2007

Plasma antenna has unique properties like low RCS and variable impedance; however, previous plasm... more Plasma antenna has unique properties like low RCS and variable impedance; however, previous plasma antenna uses 500 MHz RF power to generate a plasma column, which is limited in energy efficiency and bandwidth. Here we introduce a new type of plasma antenna that generates plasma column with pre-ionization from a DC high voltage, and signal is coupled to the plasma

Magnetic nanoparticles (MNPs) are a class of nanoparticles, which can be manipulated using magnet... more Magnetic nanoparticles (MNPs) are a class of nanoparticles, which can be manipulated using magnetic fields. Currently, MNPs are recognized as one of the most important mode as a drug carrier while they can also be potentially used as carriers for gene delivery. In this article, magnetic nanostructured lipid carriers (mNLCs) are prepared through co-precipitation method. The particle size and zeta potential, structure and thermal properties of the MNPS have been studied. The produced MNPs were also hydrophobically modified with a long chain of fatty acid namely lauric acid. These modified MNPs were mixed with nanostructured lipid carriers (NLCs) to form mNLCs. The heat capacity and flow of mNLCs was profligate in the presence of a magnetic field which is a worthy attribute for targeted drug delivery applications.

Carbon nanotube (CNT) is the primary field emission source in many new applications, but there ha... more Carbon nanotube (CNT) is the primary field emission source in many new applications, but there have been limited reports on direct growth of CNT on metal surface with CVD method with good electrical contact and surface adhesion [1]. We propose the use of BGA balls to bond CNTs grown with CVD method on Si wafer onto a metal substrate and form a grid array of emission source. Because of the low melting point (185oC) of the BGA ball and its highly matured low cost production technique and physical properties compatible with the IC packing industry, this method can manufacture very large area of metal-CNT cathode with excellent field emission characteristics. Multiple samples of such cathode show turn on field (definedat 1μA/cm current density) from 1.051.48 V/μm, and field enhancement factor β ranging from 2500-3200. Optimum bonding time for this CNT growth condition at 63 MPa pressure is around 90 seconds.

Nanoimprint lithography (NIL) is an emerging low cost technique for reproducing sub-45 nm pattern... more Nanoimprint lithography (NIL) is an emerging low cost technique for reproducing sub-45 nm pattern in various applications; however, manufacturing the mold for nanoimprint has been a key challenge in expense and resolution. Focused Ion Beams (FIB) has been known for high resolution but low throughput work in TEM sample preparation, and its extremely well defined 7 nm diameter Ga beam make it also a suitable tool for mold manufacturing for nanoimprint, which enable mass reproduction of the FIB work. We find features down to 30 nm can be made with FIB, the actual line width to beam diameter ratio is around 5-6 for an aspect ratio less than 2. A higher than 2 aspect ratio may result in re-deposition of the milled out substrate. Re-deposition can be reduced by a shorter dwell time or gas-assisted etching. There is a trade off between dwell time and feature integrity. Best results can be achieved with high hardness materials; the lack of conductivity for some materials can be remedied wit...

Electrospinning produces nanofibers with diameters ranging from 200-500 nm under 10-20 KV at 10-2... more Electrospinning produces nanofibers with diameters ranging from 200-500 nm under 10-20 KV at 10-20 cm distances, and if these nanofibers were composed of polymers like PVA or PVP, they are usually nonconductive with resistances too larger to measure on ordinary meter. One way to change the conductivity of nanofibers is to add nanoparticles. We produce Fe3O4 nanoparticles with polyols method, and mix these diameters ranging from 2050 nm nanoparticles with PVP into electrospinning process on a double knife edge receptor set up. We found the current between the two knife edges of 0.005 g of nanofibers and nanoparticles is around 20 nA at 50 V bias, and based on estimations of nanofiber diameter and number, the resistance of each individual nanoparticles containing nanofibers can be estimated.

2017 IEEE International Conference on Plasma Science (ICOPS), 2017

Photonic crystal produces bandgaps with its periodic structure, where electromagnetic waves under... more Photonic crystal produces bandgaps with its periodic structure, where electromagnetic waves undergo multiple reflections and constructive or destructive combinations, but their properties are usually not adjustable. Plasma photonic crystal on the other hand can provide some degree of transmission characteristic adjustment. Radar cross section (RCS) is a strong function of shape, and plasma can also affect RCS via absorption or scattering. For these reasons, we constructed a wedge shape plasma photonic crystal which is composed of 27 glass tubes with 12 mm diameter, and inside is filled with plasma. In this article we show the FDTD simulation results of the near fields of this device, and its RCS. We found only minor changes in the RCS of the plasma photonic crystal device with or without plasma, but substantial changes in the near field distribution behind this device. The transmission is very sensitive to plane wave incidence angle. The influence of plasma density is also presented.