Research in the Heterogeneous Integration Laboratory (HIL) is multidisciplinary and exploratory in character and lies at the interfaces of Material Science, Electrical Engineering, and Applied Physics. We focus on multidisciplinary, exploratory research that deals with heterogeneous integration of nanomaterials and devices across length scale and material boundaries. The projects can be divided into two trust areas:
Heterogeneous Integration Across Length Scales Through Self-Assembly and Transfer (Trust 1) The firstresearch trust is geared at developing engineered self-assembly and nanotransfer methods to enable the integration of functional (electronic and photonic) materials and devices into heterogeneous systems. The goal is to overcome the scaling limitations of robotic assembly lines and serial manufacturing. The team pioneered techniques of self-assembly and transfer demonstrating a number of different applications. The methods find a variety of applications:
- Metamorphic Electronics which are electronic products which undergo morphological changes and take a new shapes and form factors
- Stretchable Electronics Distributing Inorganic Semiconductor Devices on Stretchable Substrates
- Fabrication of Microscopic Chips (containing LEDs, Transistors, Solar Cells) to be used in our own and collaborative projects
Expertise: The research requires that we learn how to fabricate devices using inorganic semiconductors. We can process Si based devices including transistors, and photovoltaic cells. In addition we have experience to process GaAs and GaN based devices ranging from transistors to LEDs with microscopic chip dimensions. The core focus is to learn to distribute these devices and integrate them in new applications. As an example we have pioneered a self-assembly process. The engineered self-assembly processes use surface tension, shape recognition, hierarchies, receptors, and binding site that can be programmed to direct the assembly (no pick and place) as well as to form electrical interconnect between the disparate elements (no wirebonder needed). The process has been used in the following applications:
- The assembly of LEDs using Reel to Reel Fluidic Self-Assembly for Solid State Lighting Applications
- Realization of Flexible Cylindrical Display Segments using Liquid Solder Directed Self-Assembly and Bonding
- Parallel Self-Packaging of Semiconductor Dies Replacing Serial Pick and Place and Wirebonding
- Flip-Chip Self-assembly of Semiconductor Dies with Unique Angular Orientation and Contact Pad Registration
- Sequential Self-Assembly of a Miniaturized Transponder/Sensor System that can be Activated and Interrogated Remotely
Integration and Characterization of Functional Nanomaterials and Devices (Trust 2)
The second research trust follows a similar theme but exclusively deals with nanomaterials that are formed by bottom-up synthesis in our lab. Again a goal is to integrate these building blocks at precise locations on a surface or in 3D. Doing so the trust addresses a well known nanomanufacturing challenge. The nanomanufacturing challenge is as follows: Low dimensional nanomaterials are the building blocks of future nanotechnological products and are known to provide a variety of size dependent functions. The discovery of these functions is complete and was the driver for the first phase of nanoscience. The second phase, now, anticipates an industrial use, which has been hampered by a lack of scalable "Nanomanufacturing" methods. The discovery and development of scaleable nanomanufacturing processes is the goal of the second trust.
- Production of Functional Nanoparticles (Reactive Nanoparticles, Nanoparticle Transistors, Nanoparticle Sensors, Metallic and Semiconducting Nanoparticles)
- Nanoxerographic Printers - The team has pioneered a set of nanoxerographic printers that enables the parallel integration of functional nanoparticles onto precise locations on a substrate from the gas or liquid phase with a resolution that is 5000 times higher than conventional xerographic printers. The technique can print organic, inorganic, metallic, semi-conduction, or insulating nanoparticles in the 0.1 nm - 40 mm size window and finds applications in the integration of Nanoparticle based devices.Integration of Nanowires - Another approach is geared at the integration of nanowires to form nanowire based devices and systems. We have demonstrated the growth of nanowires at predefined locations on a surface and the fabrication of heterojunction Nanowire LEDs studying the device physics, transport, and electroluminescence in collaboration.
- Self-aligned Growth of Nanoscopic Bondwires - The team has discovered a process that enable the self-aligned growth of nanoscopic bondwires. The process enables the realisation of freeform point to point electrical connections. The wires are composed of metallic nanoparticles.
- Gas phase nanoparticle electrodeposition - This is another process that we are presently investigating. The process enables the deposition of functional materials at predetermined locations on a surface. It is similar to electrodeposition in the liquid phase. However, it is a gas phase process, and it is based on the interplay of high mobility gas ions, with a patterned substrate, and airborne nanoparticles. It eliminates material loss and has unique properties to investigate.
- Directed Airborne Transport - Fundamentals and Applications. This is a fundmental science project. The project investigates a new transport mechanism that we discovered, which supports the localized collection of airborne particles at a higher rate than previously possible. Strongly simplified the process is a directed electrodynamic transport process. The process leads to localized collection and concentration of airborne particles at predetermined sensing points on a patterned substrate. The discovered process is applicable to a wide range of particle sizes (15 orders of magnitude so far in terms of particle weight) and types (organic and inorganic).