Previous Research
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Diagnostics of Laser Interactions
- Time-Of-Flight and Emission Spectroscopy - Emission and LIF Probing of Laser Ablation - Ultrafast Pump and Probe Imaging Annealing and Crystallization - Phase transformations in Thin Si films - Laser Annealing of Silicon Nanowires - Explosive crystallization of Ge - Laser crystallization of Thin Si films Nanoparticle-based Processing - Laser Fabricated Solar Cells on Plastic - Organic Transistor Fabrication Nanofabrication - Nanomachining - High-throughput Nanoprocessing - In-situ SEM Imaging and Lasers - Nanoablation Microfabrication - Ultrafast Laser Drilling in Glass - Laser Fabricated Optofluidics |
Video Gallery
| Self-grown fiber fabrication by two photon polymerization |
| Fibroplast cells on self-standing fiber scaffolds |
| Directed assembly of cells on a chemically patterned by ultrafast laser radiation substrate |
| Nanomachining by a pulsed laser coupled into a near flield scanning optical microscope (NSOM) fiber tip |
| Laser sintering of a silver nanoparticle film |
| Liquid assisted fs laser drilling in glass |
| In-situ imaging of pulsed laser conversion of an a-Si precursor into a single nano crystal inside a TEM |
| A flat acoustic pulse produced in water by a homogenized ns laser beam is focused to a few microns |
Past Archieve
Nanofabrication by Tips Coupled with Lasers
Sponsor: DARPA
A selectively grown nanowire from multiple catalytic nanoparticles This work is focused on the development of nanofabrication processes and tools based on tips in combination with laser irradiation, delivered through near–field optics. The basic process in near–field optics entails the short–range electromagnetic interaction between the tip and the sample surface that is concentrated in domains significantly smaller than the light wavelength. Accordingly, near–field scanning optical microscopy (NSOM) instruments in both apertureless and apertured configurations have been developed by incorporating precise motion and sensing technologies. Other than imaging at the nanometer scale, confinement of radiation fields of enhanced intensity underneath the tip enables a wide range of materials modification processes that are both subtractive (nanoscale etching and ablation) and additive (nanoscale chemical vapor deposition), as well as inducing changes in the material structure via phase transformations (nanoscale crystallization). Such nanoprocessing tools can also be configured to realize directed growth of nanostructures, not only in a single direction but in 3–D space as well. These unique capabilities to open up an entirely new avenue for the definition and processing of nanostructures, while at the same time they enable integration of nanoscale devices with electronics microfabrication processes. The nanoscale confinement of highly intense light sources is utilized to drive direct chemical vapor deposition processes enabling location and size control of multispectral semiconductor nanostructures with unprecedented nanometric precision.
Cost–Effective Fabrication and Patterning of Transparent Metal Oxide Nanostructures with a Wide Range of Properties by Solution–based Laser Processing Technologies
Sponsor: NSF SBIR with Appliflex LLC
This project demonstrates the commercial feasibility of metal oxide nanostructures, especially ZnO and TiO2, which offer properties suitable for a wide range of applications from thin film battery and LED to gas sensors. In particular, they have a potential to replace indium tin oxide (ITO) as a transparent electrode and as an electron–acceptor material in bulk heterojunction solar cells. Furthermore, with proper design of nanostructures, it is possible to "tune" into controllable and multi–functional properties, for example, either continuous film for transparent electrode or mesoscopic porous structure for bulk heterojunction solar cells. While these materials are prepared by expensive vacuum processes today, there is a tremendous need to develop a cost–effective, roll–to–roll processing. Solution–based processing, enhanced by laser processing is developed to meet this target. The advantages of this hybrid approach are; (1) laser sintering, curing and/or annealing improve the morphology, structure and chemistry of printed precursor materials, to fine–tune the property of nanostructures, (2) patterning is achieved by laser selective sintering and/or direct–write process, (3) local energy deposition of laser allows selective modification of desired material with minimum thermal influence, thus compatible with low–cost plastic substrates.
Fabrication of Flexible Electronics by Laser–Aided Processing of Nanoparticles
Sponsor: NSF
Inkjet direct writing of functional materials provides a promising pathway towards realization of ultra–low cost, large area printed electronics, albeit at the expense of lowered resolution (~20-50 μm). Experimental results at the Laser Thermal Laboratory demonstrate that laser sintering and ablation of inkjet printed metal nanoparticles enables low temperature metal deposition as well as high–resolution patterning thus overcoming the limitation of inkjet direct writing without any lithography processes. Combined with an air stable carboxylate–functionalized polythiophene, all–inkjet printed and laser processed organic field effect transistors (OFETs) with micron to submicron critical feature resolution were fabricated in a fully maskless sequence, eliminating the need for any lithographic processes. All processing and characterization steps were carried out at plastic–compatible low temperatures and in air under ambient pressure.
To fully realize this exceptional promising manufacturing methodology, several basic issues have to be addressed. The OFETs fabricated by laser sintering and ablation of nanoparticle ink must be characterized in order to optimize the performance in terms of the channel size, the air stable semiconductor material, the short channel effect and the channel roughness. To increase reliability, the thickness uniformity of the printed dielectric layer must be improved. Thorough understanding must be gained on the physical mechanisms of the laser light interaction with the nanoparticle material. While enhanced light coupling should be expected, very little is known about the phase transition, sintering (bonding) and vaporization of nanoparticles upon intense laser excitation. On–line, temporally resolved monitoring techniques are needed in order to unveil the detailed mechanisms of the laser light interaction, including the sintering and ablation processes. For better fundamental understanding and ultimately for process optimization, numerical simulation is needed. To facilitate the numerical simulations, basic thermal, optical and electrical properties of the nanomaterial must be measured.
The novel concept of reduced temperature, laser–based processing of metal nanoparticles eliminates the need for lithographic processes and opens the way to the fabrication of high–resolution, all–printed electronic devices on flexible substrates. Beyond the advancement of important technologies, the scientific research outcome is expected to shed light on complex phenomena involved in the laser interactions with nanoparticle materials. Specifically, it will elucidate the energy transfer, melting, sintering and ablation processes under intense laser excitation. Prime candidates for the utilization of the technology developed in this project include the manufacture of flat panel displays and large area electronics, interconnections, crossover conductors, capacitors, antennae, chemical sensors and active electrical components on flexible substrates. Beyond these, a much wider spectrum of potential applications can be envisioned in rapid prototyping and microfabrication processes utilizing magnetic, ceramic and semiconductor nanoparticles.
Off–Equilibrium Doping of Semiconductor Nanowires
Sponsor: NSF, PI: Junqiao Wu of UCB MSE
The objectives of this program are aimed at controlling the doping of nanowires to the level exceeding the thermodynamical equilibrium limit. The research undertaken targets fundamental questions in nanoscience and nanotechnology. Can nanowires be doped to or above the solubility limit of dopants? How to dope nanowires to a uniform dopant distribution? Is it possible to heavily dope nanomaterials to the type opposite to their natural propensity? Doping of semiconductor nanowires is one of the bottlenecks that hinder their wide range of potential applications. Doping mechanisms well–established in the bulk have to be revisited in nanowires due to their small dimension and large surface–to–volume ratio. For example, even the best studied Si nanowires have not been doped at concentrations and uniformity that are nearly comparable to the bulk. This project is aimed at discovering a strategy to promote the theory and practice of nanowire doping to the maturity level at or exceeding the bulk. This research program may lead to doping of nanowires at unprecedentedly high concentrations and uniform distribution. The natural doping propensity and disparity of many technologically important semiconductors will be broken through, which would lay the foundation for a new generation of microelectronic and optoelectronic technologies. The achievement would produce significant advancements in the understanding of defect physics and kinetics in nanomaterials. Demonstration of such doping strategy will promote innovations in semiconductor nanostructure synthesis and device processing. New knowledge will be gained concerning the materials science and processing at the nanoscale.
Carbon Nanotube Membranes for Energy–Efficient Carbon Sequestration
Sponsor: ARPA–E – Subcontract from Porifera Inc – Pls: Drs Alex Noy and Olgica Bakajin of Porifera Inc.
This work aims at developing high flux/selectivity carbon nanotube (CNT) membranes for efficient separation of CO2from the industrial emission streams. Current commercial operations manage CO2 from the power station emissions using chemical absorption, which is inherently expensive, energy–intensive, and produces negative environmental impact of its own. Membrane–based CO2 separations could potentially deliver better efficiency, cheaper sequestration, and low energy consumption, but the development of this technology has been hampered by the lack of membranes that combine sufficiently high CO2 selectivity with high flux. Unique structure of sub–2–nm carbon nanotube based membranes pores results in gas permeation fluxes that are two orders of magnitude higher than any other membrane of comparable pore size. In this work we will develop and demonstrate a comprehensive set of chemical and physical modifications of CNT membranes that enhance their CO2 selectivity to a level that enables a new membrane based paradigm for industrial CO2 management.
Nanobioelectronics with 1–D Lipid Bilayers on Si Nanowires
Sponsor: UC Lab Research Program
Collaborators: Dr. Alex Noy (LLNL), Prof. Pieter Stroeve (UC Davis), Dr. Caroline–Ajo Franklin (LBNL)
A schematic representation of a 1D bilayer assembled on a nanotube This project aims at developing a new type of functional bio–nanostructures that combine the unique electronic properties and sensitivity of silicon nanowire transistors with the biocompatibility, specificity, and non–fouling properties of lipid bilayer membranes. Such coupling allows nanowire electronics to take advantage of an astonishingly diverse and efficient spectrum of functions performed by membrane channels in living systems that encompass highly specific water and ion transport, signal transduction, molecular recognition, and environmental sensing. The research program will investigate fundamental issues associated with integrating biological components into synthetic nanoscale devices and structures, as well as device architectures that realize such integration. This project focuses on two major goals: (1) to utilize this architecture to build functional bioelectronic devices that detect transport through biological channels using a nanowire transistor platform; and (2) using these devices to investigate fundamental scientific questions about the properties of biological membranes at extreme curvatures.
Direct Nanoimprinting–based Nanopatterning of Functional Nanomaterials for Electronics & Sensing Applications
Sponsor: NSF – PI: Albert P. Pisano
Nanoimprinting lithography (NIL) is emerging as an alternative nanopatterning technology to traditional photolithography. Its major advantages are low cost, high–throughput production, and operational ease. Metal nanoimprinting is typically an indirect process where a polymer (e.g. PMMA) pattern is first created by nanoimprinting, which is then used as mask for etching or a lift off process. This involves multiple steps and expensive processes, thereby increasing the cost of manufacturing. A novel method of direct nanoimprinting of metal has been developed by the PIs, based upon the utilization of a metallic nanoparticle ink as the nanoimprinting solution. This process eliminates the need of intermediate polymer nanoimprinting step for dry etching or vacuum deposition. It also offers the considerable advantage of utilizing low temperatures and pressures, which can be applied to flexible substrate electronics.
To fully understand and improve this exceptionally promising nanomanufacturing methodology, several basic issues have to be addressed. (1) Fluidic and thermal characteristics of nanoparticle solution are critical in the direct nanoimprinting process of nanoparticle solution since this process strongly relies on the filling and drying phenomena within the nanoimprinting stamps. (2) Mechanical properties of nanoimprinting stamps should be better understood and improved for high fidelity nanopatterning with no distortion of nanoimprinted features. (3) Experimental and theoretical analysis of thermal sintering process of nanoparticles should be carried out. (4) Quantitative analysis on the adhesion between nanoimprinted features and substrates has to be conducted. Furthermore, the study on adhesion promoting agent for improving adhesion strength is very valuable. (5) More in–depth analysis of influence of mechanical deformation on nanoimprinted features and nanoparticle–based thin films must be conducted to ensure good performance of nanoimprinted features on flexible polymer substrate in long–term usage. (6) New technologies such as multi–layer / multi–component nanoimprinting or large area nanoimprinting should be developed for practical applications in the electronics industry. The goal of this project is to address these issues that are of both fundamental and applied importance.
Sponsor: DARPA
A selectively grown nanowire from multiple catalytic nanoparticles This work is focused on the development of nanofabrication processes and tools based on tips in combination with laser irradiation, delivered through near–field optics. The basic process in near–field optics entails the short–range electromagnetic interaction between the tip and the sample surface that is concentrated in domains significantly smaller than the light wavelength. Accordingly, near–field scanning optical microscopy (NSOM) instruments in both apertureless and apertured configurations have been developed by incorporating precise motion and sensing technologies. Other than imaging at the nanometer scale, confinement of radiation fields of enhanced intensity underneath the tip enables a wide range of materials modification processes that are both subtractive (nanoscale etching and ablation) and additive (nanoscale chemical vapor deposition), as well as inducing changes in the material structure via phase transformations (nanoscale crystallization). Such nanoprocessing tools can also be configured to realize directed growth of nanostructures, not only in a single direction but in 3–D space as well. These unique capabilities to open up an entirely new avenue for the definition and processing of nanostructures, while at the same time they enable integration of nanoscale devices with electronics microfabrication processes. The nanoscale confinement of highly intense light sources is utilized to drive direct chemical vapor deposition processes enabling location and size control of multispectral semiconductor nanostructures with unprecedented nanometric precision.
Cost–Effective Fabrication and Patterning of Transparent Metal Oxide Nanostructures with a Wide Range of Properties by Solution–based Laser Processing Technologies
Sponsor: NSF SBIR with Appliflex LLC
This project demonstrates the commercial feasibility of metal oxide nanostructures, especially ZnO and TiO2, which offer properties suitable for a wide range of applications from thin film battery and LED to gas sensors. In particular, they have a potential to replace indium tin oxide (ITO) as a transparent electrode and as an electron–acceptor material in bulk heterojunction solar cells. Furthermore, with proper design of nanostructures, it is possible to "tune" into controllable and multi–functional properties, for example, either continuous film for transparent electrode or mesoscopic porous structure for bulk heterojunction solar cells. While these materials are prepared by expensive vacuum processes today, there is a tremendous need to develop a cost–effective, roll–to–roll processing. Solution–based processing, enhanced by laser processing is developed to meet this target. The advantages of this hybrid approach are; (1) laser sintering, curing and/or annealing improve the morphology, structure and chemistry of printed precursor materials, to fine–tune the property of nanostructures, (2) patterning is achieved by laser selective sintering and/or direct–write process, (3) local energy deposition of laser allows selective modification of desired material with minimum thermal influence, thus compatible with low–cost plastic substrates.
Fabrication of Flexible Electronics by Laser–Aided Processing of Nanoparticles
Sponsor: NSF
Inkjet direct writing of functional materials provides a promising pathway towards realization of ultra–low cost, large area printed electronics, albeit at the expense of lowered resolution (~20-50 μm). Experimental results at the Laser Thermal Laboratory demonstrate that laser sintering and ablation of inkjet printed metal nanoparticles enables low temperature metal deposition as well as high–resolution patterning thus overcoming the limitation of inkjet direct writing without any lithography processes. Combined with an air stable carboxylate–functionalized polythiophene, all–inkjet printed and laser processed organic field effect transistors (OFETs) with micron to submicron critical feature resolution were fabricated in a fully maskless sequence, eliminating the need for any lithographic processes. All processing and characterization steps were carried out at plastic–compatible low temperatures and in air under ambient pressure.
To fully realize this exceptional promising manufacturing methodology, several basic issues have to be addressed. The OFETs fabricated by laser sintering and ablation of nanoparticle ink must be characterized in order to optimize the performance in terms of the channel size, the air stable semiconductor material, the short channel effect and the channel roughness. To increase reliability, the thickness uniformity of the printed dielectric layer must be improved. Thorough understanding must be gained on the physical mechanisms of the laser light interaction with the nanoparticle material. While enhanced light coupling should be expected, very little is known about the phase transition, sintering (bonding) and vaporization of nanoparticles upon intense laser excitation. On–line, temporally resolved monitoring techniques are needed in order to unveil the detailed mechanisms of the laser light interaction, including the sintering and ablation processes. For better fundamental understanding and ultimately for process optimization, numerical simulation is needed. To facilitate the numerical simulations, basic thermal, optical and electrical properties of the nanomaterial must be measured.
The novel concept of reduced temperature, laser–based processing of metal nanoparticles eliminates the need for lithographic processes and opens the way to the fabrication of high–resolution, all–printed electronic devices on flexible substrates. Beyond the advancement of important technologies, the scientific research outcome is expected to shed light on complex phenomena involved in the laser interactions with nanoparticle materials. Specifically, it will elucidate the energy transfer, melting, sintering and ablation processes under intense laser excitation. Prime candidates for the utilization of the technology developed in this project include the manufacture of flat panel displays and large area electronics, interconnections, crossover conductors, capacitors, antennae, chemical sensors and active electrical components on flexible substrates. Beyond these, a much wider spectrum of potential applications can be envisioned in rapid prototyping and microfabrication processes utilizing magnetic, ceramic and semiconductor nanoparticles.
Off–Equilibrium Doping of Semiconductor Nanowires
Sponsor: NSF, PI: Junqiao Wu of UCB MSE
The objectives of this program are aimed at controlling the doping of nanowires to the level exceeding the thermodynamical equilibrium limit. The research undertaken targets fundamental questions in nanoscience and nanotechnology. Can nanowires be doped to or above the solubility limit of dopants? How to dope nanowires to a uniform dopant distribution? Is it possible to heavily dope nanomaterials to the type opposite to their natural propensity? Doping of semiconductor nanowires is one of the bottlenecks that hinder their wide range of potential applications. Doping mechanisms well–established in the bulk have to be revisited in nanowires due to their small dimension and large surface–to–volume ratio. For example, even the best studied Si nanowires have not been doped at concentrations and uniformity that are nearly comparable to the bulk. This project is aimed at discovering a strategy to promote the theory and practice of nanowire doping to the maturity level at or exceeding the bulk. This research program may lead to doping of nanowires at unprecedentedly high concentrations and uniform distribution. The natural doping propensity and disparity of many technologically important semiconductors will be broken through, which would lay the foundation for a new generation of microelectronic and optoelectronic technologies. The achievement would produce significant advancements in the understanding of defect physics and kinetics in nanomaterials. Demonstration of such doping strategy will promote innovations in semiconductor nanostructure synthesis and device processing. New knowledge will be gained concerning the materials science and processing at the nanoscale.
Carbon Nanotube Membranes for Energy–Efficient Carbon Sequestration
Sponsor: ARPA–E – Subcontract from Porifera Inc – Pls: Drs Alex Noy and Olgica Bakajin of Porifera Inc.
This work aims at developing high flux/selectivity carbon nanotube (CNT) membranes for efficient separation of CO2from the industrial emission streams. Current commercial operations manage CO2 from the power station emissions using chemical absorption, which is inherently expensive, energy–intensive, and produces negative environmental impact of its own. Membrane–based CO2 separations could potentially deliver better efficiency, cheaper sequestration, and low energy consumption, but the development of this technology has been hampered by the lack of membranes that combine sufficiently high CO2 selectivity with high flux. Unique structure of sub–2–nm carbon nanotube based membranes pores results in gas permeation fluxes that are two orders of magnitude higher than any other membrane of comparable pore size. In this work we will develop and demonstrate a comprehensive set of chemical and physical modifications of CNT membranes that enhance their CO2 selectivity to a level that enables a new membrane based paradigm for industrial CO2 management.
Nanobioelectronics with 1–D Lipid Bilayers on Si Nanowires
Sponsor: UC Lab Research Program
Collaborators: Dr. Alex Noy (LLNL), Prof. Pieter Stroeve (UC Davis), Dr. Caroline–Ajo Franklin (LBNL)
A schematic representation of a 1D bilayer assembled on a nanotube This project aims at developing a new type of functional bio–nanostructures that combine the unique electronic properties and sensitivity of silicon nanowire transistors with the biocompatibility, specificity, and non–fouling properties of lipid bilayer membranes. Such coupling allows nanowire electronics to take advantage of an astonishingly diverse and efficient spectrum of functions performed by membrane channels in living systems that encompass highly specific water and ion transport, signal transduction, molecular recognition, and environmental sensing. The research program will investigate fundamental issues associated with integrating biological components into synthetic nanoscale devices and structures, as well as device architectures that realize such integration. This project focuses on two major goals: (1) to utilize this architecture to build functional bioelectronic devices that detect transport through biological channels using a nanowire transistor platform; and (2) using these devices to investigate fundamental scientific questions about the properties of biological membranes at extreme curvatures.
Direct Nanoimprinting–based Nanopatterning of Functional Nanomaterials for Electronics & Sensing Applications
Sponsor: NSF – PI: Albert P. Pisano
Nanoimprinting lithography (NIL) is emerging as an alternative nanopatterning technology to traditional photolithography. Its major advantages are low cost, high–throughput production, and operational ease. Metal nanoimprinting is typically an indirect process where a polymer (e.g. PMMA) pattern is first created by nanoimprinting, which is then used as mask for etching or a lift off process. This involves multiple steps and expensive processes, thereby increasing the cost of manufacturing. A novel method of direct nanoimprinting of metal has been developed by the PIs, based upon the utilization of a metallic nanoparticle ink as the nanoimprinting solution. This process eliminates the need of intermediate polymer nanoimprinting step for dry etching or vacuum deposition. It also offers the considerable advantage of utilizing low temperatures and pressures, which can be applied to flexible substrate electronics.
To fully understand and improve this exceptionally promising nanomanufacturing methodology, several basic issues have to be addressed. (1) Fluidic and thermal characteristics of nanoparticle solution are critical in the direct nanoimprinting process of nanoparticle solution since this process strongly relies on the filling and drying phenomena within the nanoimprinting stamps. (2) Mechanical properties of nanoimprinting stamps should be better understood and improved for high fidelity nanopatterning with no distortion of nanoimprinted features. (3) Experimental and theoretical analysis of thermal sintering process of nanoparticles should be carried out. (4) Quantitative analysis on the adhesion between nanoimprinted features and substrates has to be conducted. Furthermore, the study on adhesion promoting agent for improving adhesion strength is very valuable. (5) More in–depth analysis of influence of mechanical deformation on nanoimprinted features and nanoparticle–based thin films must be conducted to ensure good performance of nanoimprinted features on flexible polymer substrate in long–term usage. (6) New technologies such as multi–layer / multi–component nanoimprinting or large area nanoimprinting should be developed for practical applications in the electronics industry. The goal of this project is to address these issues that are of both fundamental and applied importance.