Project 1: Investigation of Fluidic Chip Assembly Methods for the Production of LED Lighting Modules Objective: Development of a cost-effective manufacturing process for novel LED lighting modules Method: Biologically inspired self-organization. |
Background: Solid-state lighting modules (LEDs) have seen strong growth in recent years. Continued growth is projected since policymakers have mandated the replacement of current inefficient incandescent light bulbs worldwide.
A major challenge today from a manufacturing perspective is the high production cost. More than 50% of the production cost is associated with deterministic pick-and-place assembly, wire bonding, and packaging of LED chips.
A potential solution to the production cost issue is a fluidic self-assembly-based manufacturing approach (fluidic self-assembly1, self-assembly2, self-packaging process3), which forms the basis for the research project. FastTrack option: This project can begin as a master’s thesis with a reduced scope. However, outstanding candidates will have the option to expand the scope within the framework of a doctoral thesis, where the previous thesis is not considered “lost time” but can be extended via a “fast-track” path to graduate with a doctoral degree.
Research Aspects: This is a transdisciplinary project. Students from Physics, Electrical Engineering (EE), Mechanical Engineering (ME), and Materials Science and Technology (MWT) are equally well-suited if they are not afraid to learn new concepts where solutions are not taught in class. The student should be familiar with one of the three aspects and open to the other two.
Additional Knowledge Students Learn:
References:
1. JMEMS 21(1), 58–99 (2012).
2. PNAS 101(35), 12814–12817 (2004).
3. Science 296(5566), 323-325 (2002).
Project 2:“Development of a Fluidic Conveyor Belt System with Mechanical Excitation and Optical Observation of Self-Organization Processes”
Broader Research Area: Fluidic chip assembly methods for the fabrication of LED lighting modules
Background: This project is in the field of solder-based self-assembly. The student will work on an international collaborative project together with a researcher in the USA (former laboratory of Professor Jacobs) where a first prototype conveyor belt system has been installed. The goal is to install a similar but improved system in Ilmenau. A simplified drawing of the system is shown. The specific design is confidential and will be discussed with interested candidates.
Tasks: This is a relatively straightforward engineering project in which electrical and mechanical components are assembled to build a machine prototype.
Students from Physics, Electrical Engineering, and Mechanical Engineering are equally well-suited if they possess hands-on skills (practical experience). The system includes mechanical parts, stepper motors, optical components, rollers, and heaters to maintain a specific temperature and agitation within the liquid bath. Funding to purchase the components is available. The student will work with a mechanic at the Nanotechnology Research Group who specializes in rapid prototyping and the machining of custom parts. Prof. Jacobs will assist with the design.
What is the Broader Context of this Project?
The broader context of this project lies in the field of self-assembly-based manufacturing, a biologically inspired and relatively new manufacturing concept that overcomes some of the limitations of deterministic manufacturing, which relies on serial robotic pick-and-place machines. Instead of placing components one at a time at a specific location, the components assemble at that location through self-assembly.
What are the Applications?
Self-assembly can be used to assemble or package semiconducting elements on any surface with high yield and throughput. It has been applied to solid-state lighting (LED lighting modules), the manufacturing of solar cells, and flexible silicon-based electronics. Here are a few recent news articles:
· May 25, 2011, Nature Materials, "Mosaic Masters" highlights R. Knuesel and H.O. Jacobs' Advanced Materials paper on self-tiling.
· January 13–31, 2010, Numerous news outlets (BBC, Ars Technica, Herald, Popular Science, DiscoverMag, TCE Today, TGdaily, Softpedia, Treeh, Golem, Newsintech, Printed Electronics World, Green Diary, Engadget, Your Renewable News, Power & Energy, The Green Optimistic, Solar, Ethiopian Review, Energetika, Newstrack India, Physorg, Elektroniktidningen, Rozhlas, Inovação Tecnológica, Telepolis, and many more) report on a recent PNAS article describing a fluidic self-assembly process forming flexible solar cells.
· January 13, 2010, PNAS, The Proceedings of the National Academy of Sciences flags and highlights R. Knuesel and H.O. Jacobs’ research article on self-assembling electronics and photovoltaics as being of interest to the broader community and media.
Project 3:“Investigation of an unpublished two-step solder system for the self-organization and self-assembly of semiconductor devices”
Background: The basic concept of solder-directed self-assembly is based on the high surface tension of liquid solder. Like mercury, liquid solder tends to form droplets or fuse with other metallic surfaces to reduce interfacial free energy. This mechanism can be used to drive engineered self-assembly processes. For example, in the illustration, the liquid solder is used as a receptor since it wets the metal contacts on the components. Components are captured by the solder-based receptors as they tumble inside the enclosed vial within a heated liquid where the solder is molten. The components attach themselves and align with high precision and yield. Here are a few references where this basic process is used in the field of self-assembly-based manufacturing:
References:
1. JMEMS 21(1), 58–99 (2012).
2. PNAS 101(35), 12814–12817 (2004).
3. Science 296(5566), 323-325 (2002).
Challenge: A challenge in this process relates to the melting point of the solder that can be used, which must be below the boiling point of the solvent or liquid transporting the components. This means that it is currently not possible to use high-melting-point solder unless the self-assembly is performed in extremely hot environments.
Solution: We believe we have a solution to this problem—one that has not yet been published—which could revolutionize this field. The goal of this thesis project is to test this idea. Details will be discussed in person.
Tasks:
Project 4:Fluidic self-assembly with applications in concentrator-based photovoltaic cells
Fabrication strategies that rely on self-assembly mechanisms are widely recognized as essential tools in nanotechnology. Self-assembly, however, is not limited to the nanometer scale. Strategies based on self-assembly are projected to have a major impact on the manufacturing of systems at both the micrometer and nanometer scales. Several directed self-assembly methods have been demonstrated to generate functional electrical microsystems. For example, Smith et al. reported shape-directed fluidic methods for positioning light-emitting diodes (LEDs) onto silicon substrates.
Within this bachelor’s/master’s thesis, a prototype setup for the fluidic self-assembly of micrometer-scale objects onto flexible polymer substrates is to be constructed, assembled, and tested.
JMEMS 15(3), 457–464 (2006).
www.golem.de/1001/72387.html
“Research in the Field of Nanoxerographic Printing Processes”
Brief Overview of the Research Area
3D Nano-Xerographic Printers
Background: Nanoscience has uncovered a “world of functions.” The standard approach began with the synthesis of nanoparticles, nanowires, and other higher-order structures, which were then deposited onto a substrate. The next step (Find and Probe) involved identifying species of interest and subsequently measuring size-dependent physical properties using specialized analytical tools. This approach has led to numerous publications in Science and Nature reporting devices (physical sensors, biosensors, transistors, switches, photovoltaic cells, light-emitting structures) with record performance. However, this method is not a nanomanufacturing approach that will support the mass production of functional devices over large areas.
This requires the development of a directed deposition process, including
enabling the production of nanostructured materials and devices beyond current levels. Specifically, the project targets the selective area growth/deposition of objects:
· made of different materials,
· of different diameters,
· of different lengths,
· different material sequences, and
· 3D shapes
all controlled according to a desired topology on a single substrate within a single deposition process.
The approach that forms the basis for the various BA/MA thesis projects is a tool we have termed “Nanoxerography.”Nanoxerographic printers enable the low-cost printing of known devices (physical sensor arrays, solar cells, electronics, etc.). Nanoxerographic printers are modular systems and contain several different zones, as illustrated.
Thesis Topic: Installation and testing of an improved nanoxerographic printer based on a new design (Zone 1 and Zone 2, as shown in the illustration)
· This is a relatively straightforward engineering project. Students from Physics, Electrical Engineering, and Mechanical Engineering are equally well-suited if they have hands-on skills (practical experience). The student will work on an international collaborative project together with a researcher in the USA (formerly at Professor Jacobs’ laboratory), where several systems have been installed. The goal is to install a similar but improved system in Ilmenau. The specific design is confidential and will be discussed with interested candidates. The system includes a high-temperature region that produces nanoparticles and a deposition zone where programmable electric force fields are used to deposit particles at precise locations on custom-made substrates. The student will work with a mechanic at the Nanotechnology Research Group who specializes in rapid prototyping and the machining of custom parts. Prof. Jacobs will assist with the design. The student will learn all aspects of the process in the initial phase before taking over testing and design modifications with the goal of producing well-defined nanostructures, specifically 3D nanostructured electrodes for photovoltaic applications. The fabrication of the substrates will be carried out in close collaboration with Dr. Stauden.
Thesis Topic: Nanomaterial Generation and Characterization for Nanoxerography and Printable Photonics Applications (Zone 1)
· This project will involve a brief literature review to compare a new approach to nanoparticle generation that we have established with the current state of the art and to extend this method to produce and print optically active quantum dots over increasingly large areas for solid-state lighting applications.
Thesis Topic: Optically Programmable Nanoxerographic Deposition (Zone 2)
· This project will test a concept for optically programming the 3D deposition of nanomaterials. The details are confidential and have not been published. This project is of particular interest to master’s students who wish to publish for various reasons and career plans where a strong publication record is important (Ph.D. candidates)
Thesis Topic: 3D Nanostructure Deposition – Explore unknown operating regimes by altering carrier gas, pressure, and substrate temperature and study the effect (Zone 2).
· This project will utilize an existing printer design to test unknown operating regimes. All approaches are permitted. This is a discovery-driven project for someone seeking to make new discoveries.
Thesis Topic: Molecular Programmable Selected Area Deposition and Growth (Zone 1 & 2).
· This project extends nanoxerographic printers to print various types of molecules. The details are confidential and have not been published. This project is of particular interest to master’s students who wish to publish for various reasons and career plans where a strong publication record is important (Ph.D. candidates) or for someone who simply wants to say, “I was the first and made a real discovery.”
Doctoral Thesis - Fast-track option: The projects begin as a master’s thesis with a reduced scope. However, outstanding candidates will have the option to expand the scope within the framework of a doctoral thesis and in collaboration with an industry partner, where the previous thesis is not considered “wasted time” but can be extended via a “fast-track” path to graduate with a doctoral degree.
The topic involves familiarization with the fundamentals of Auger electron spectroscopy as well as the measurement and evaluation of technologically relevant Group III nitride layers and layer sequences. It requires integration with layer fabrication via MBE and MOCVD and primarily focuses on the analysis and evaluation of layers produced in-house. The semiconductor layers of interest consist of GaN, AlN, InN, and their ternary and quaternary compounds. An important part of the work is a literature review of current measurement results using AES on these semiconductor materials. The measurements include spatially high-resolution Auger measurements with the new Microlab 350 Auger electron spectrometer, Auger depth profiles to measure elemental depth distribution, and peak shape analyses for the electrical characterization of the layers. Complementary measurement techniques (XPS, AFM, and electrical methods such as Hall and CV measurements) should be understood and, in some cases, performed by the student.
Advisor: Gernot Ecke
Group III nitrides are among the semiconductor materials of the 21st century and have found their place in optoelectronics and high-frequency technology. This research is intended to contribute to the development of novel high-frequency devices. The focus of the investigation is the development of process technologies for the fabrication of transistors based on cubic Group III nitrides. The main focus of the work to be carried out is on electron beam lithography and the associated metallization and etching processes. In addition to work in the field of technology development, the electrical characterization of the device and the associated determination of material properties are key focuses of the research. The work is being conducted in cooperation with the Solid-State Electronics Division at the Technical University of Ilmenau and the Department of Physics at the University of Paderborn.
Advisor: Jörg Pezoldt
Graphene consists of a single layer of graphite and possesses exceptional electronic properties, such as extremely high charge carrier mobility. It can be applied to substrate materials through exfoliation and wafer bonding. Alternatively, it is possible to produce this material on SiC. Within the scope of this topic, process technologies for the fabrication of graphene-based transistors are to be developed. The work involves the fabrication of graphene on Si and SiC-based substrates. Another focus is on electron beam lithography and the associated metallization and etching processes, as well as the implementation of gate materials. In addition to technology development, the electrical characterization of the device and the associated process control, as well as the associated determination of material properties, are essential components of the research work.
The work is carried out in cooperation with the Department of Solid-State Electronics and the Department of Engineering Physics I at the Technical University of Ilmenau.
Advisor: Jörg Pezoldt
Heterostructures and their modification through ion implantation and thermal treatment form the basis for many modern devices. Parameters determining their electronic and optical properties include the strain state, chemical composition, and defect density, as well as the surface and interface sharpness and the thicknesses of the individual layers. These parameters can be measured non-destructively using high-resolution X-ray diffraction. The objective of this work is to develop standard analytical methods for the investigation of heterostructures in the material systems AlGaN-SiC, AlGaN-SiC-Si, and SiC-Si, as well as substrates and epitaxial layers modified by ion implantation. Supplementary investigations include UV-Vis and infrared ellipsometry as well as transmission electron microscopy. The latter method is carried out in cooperation with the Materials Engineering Department.
Advisor: Jörg Pezoldt
Heterostructures form the basis for many modern electronic devices. These are produced using the process of heteroepitaxy. Important parameters in these structures include surface and interface sharpness, the thicknesses of the individual layers, the stress state, the chemical composition, and their electronic and optical properties. These parameters can be measured non-destructively using infrared ellipsometry. The objective of this work is to develop analytical and evaluation methods for investigating property anisotropy as well as composition and stress gradients in heterostructures. The focus of the investigations is on Group III nitride heterostructures, SiC on sapphire, SiC, GaAs, and Si substrates. The Department of Experimental Physics I is available as a collaboration partner.
Advisor: Jörg Pezoldt
Wide-bandgap semiconductors such as Group III nitrides and SiC open up new fields of application for electronic and sensor devices. They complement the capabilities of silicon electronics and sensor technology in a meaningful way and expand the application areas of semiconductor devices. Furthermore, these materials possess a structural diversity that enables the design of novel device principles. The research aims to design novel types of heterostructures using freely available simulation software, estimate their properties, and conduct initial experimental work for their verification. To this end, models must be developed that allow for predictive forecasting of the expected properties, as well as guidance on the implementation methods for the structures to be created and their design. Advisor: Jörg Pezoldt 7. Silicon carbide micro- and nanowires for electronic and sensor applicationsThe ever-advancing development of semiconductor technology and its devices allows for the exploration of ever-new application areas. At the same time, however, this requires the development of new device structures and the implementation of new materials to meet the pressure for innovation in this field. This research project addresses this challenge by attempting to combine classical silicon technology techniques with a third-generation semiconductor material to lay the foundation for sensors with improved sensitivity. At a later stage, as the dimensions of the device are scaled down, quantization effects are to be utilized. Silicon carbide is to be used as the base material, which opens the way to chemically more aggressive media, such as those found in biomedical engineering.The device structure consists of cantilevered or freestanding structures located on an insulating material. The silicon carbide is produced using a newly developed process for low-temperature deposition. The mechanical strain in the heteroepitaxial system, which is important for the device’s lifespan and functionality, is controlled through an interface modification in the submonolayer range or through specially fabricated substrates. The focus of this work is to investigate the influence of growth conditions on the electronic and mechanical properties of the fabricated nanostructures, as well as their suitability for use in sensors.
Advisor: Jörg Pezoldt