Materials and Processing Innovations

Synthesis and Engineer of Nano-Materials


Novel Properties

Exploration of New Functionalities of Nano-Structures


Heterogeneous Integration

Controllable Assembly of Nano-Materials


Technological Applications

Energy Harvesting, Nano-Electronics, Nano-Photonics, Sensors, etc


-   Our research focus is highly interdisciplinary involving chemistry, physics, materials science and various engineering disciplines to explore novel nano-materials and nano-engineering techniques for various technological applications. They can be categorized into three major directions:


-     1. Monolayer Assisted Nanoscale Processing


- Device scaling has been the driving force for technology advancements in the semiconductor industry over the last few decades. This scaling presents a tremendous challenge to fabricate nano-scale devices controllably and cost-effectively. In this regard, we aim to explore the manipulation of the surface properties of semiconductor nanostructures to enable alternative and novel nano-scale device fabrication schemes. For example, we have developed surface doping of Si and III-V semiconductor nanostructures with self-limiting formation of molecular monolayers yielding ultrashallow junctions (USJs) with low defect density which is in distinct contrast to the number of defects induced by conventional ion-implantation techniques.


Related Publications:


Ho J.C.*, Yerushalmi R.*, Jacobson Z.A., Fan Z., Alley R.L., Javey A. “Controlled nanoscale doping of semiconductors via molecular monolayers”, Nature Materials, 7(1), 62-67, 2008.


Ho J.C., Yerushalmi R., Smith G., Majhi P., Bennett J., Halim J., Faifer V.N., Javey A. “Wafer-Scale, Sub-5 nm Junction Formation by Monolayer Doping and Conventional Spike Annealing”, Nano Letters, 9 (2), 725–730, 2009. 


Ho J.C., Ford A.C., Leu P.W., Chueh Y.L., Javey A. “Formation of Ultra-Shallow Junctions in Indium Arsenide with Monolayer Doping”, Applied Physics Letter, 95, 072108, 2009.


-   - 2. Synthesis and Characterization of Fundamental Properties of Nano-Materials


- Recently, nano-materials have attracted a large amount of research attention due to the unique physical properties of materials at the nano-scale. We are interested in developing new synthesis techniques to enable new functionalities of nano-materials. At the same time, it is essential to study and understand the fundamental properties of the materials in order to tailor them for various technological applications. For instance, we synthesized, fabricated and characterized individual InAs NW FETs to study intrinsic electronic transport properties using temperature-dependent current-voltage (I-V) and capacitance-voltage (C-V) spectroscopy. The field-effect peak mobility was found to be ~ 7000 cm2/Vs for a NW diameter of ~ 40 nm and the mobility monotonically decreased with the NW diameter down to ~ 10 nm, with the low temperature transport data suggesting the drastic effect of the surface roughness scattering on the mobility degradation for miniaturized NWs.


Related Publications:


Ford L., Ho J.C., Fan Z., Ergen O., Altoe V., Razavi H., Javey A. “Synthesis, Contact Printing, and Device Characterization of Ni-Catalyzed, Crystalline InAs Nanowires”, Nano Research, 1, 32-39, 2008.


Chueh Y.L., Ford A. C., Ho J.C., Jacobson Z. A., Fan Z., Chen C.Y., Chou L.J., Javey A. “Formation and Characterization of NixInAs/InAs Nanowire Heterostructures by Solid Source Reaction”, Nano Letters, 8, 4528-4533, 2008.


Ford A.C.*, Ho J.C.*, Chueh Y.L.*, Tseng Y.C., Fan Z., Guo J., Bokor J., Javey A. “Diameter-Dependent Electron Mobility of InAs Nanowires”, Nano Letters, 9, 360-365, 2009.


Ford A.C., Chuang S., Ho J.C., Chueh Y.L., Javey A. “Patterned p-Doping of InAs Nanowires by Gas-Phase Surface Diffusion of Zn”, Nano Letters, 10, 509–513, 2010.  


- - 3. Large-Scale and Heterogeneous Integration of Nano-Materials for Flexible and High Performance Technological Applications including Electronics, Energy-Harvesting Modules, Photonics and Sensors.


- Although numerous amazing properties of nano-materials such as nanowires (NW) have been reported, the controlled and uniform assembly of “bottom-up” NW materials with high scalability is still one of the significant bottleneck challenges to integrate NWs for practical technological applications. In this regard, we have achieved a high throughput and generic printing approach to assemble NWs on any substrate including Si, plastics, paper, and glass. With this approach, we can obtain a monolayer of NW film with high print density, good directional alignment, and wafer-scale uniformity on substrates. To demonstrate the viability of this approach, we developed the first all NW-based heterogeneous integrated image sensor arrays. Moreover, nano-materials based energy-harvesting and photonic applications are currently being explored.


Related Publications:


Fan Z., Ho J.C., Jacobson Z.A., Yerushalmi R., Alley R.L., Razavi H., Javey A. “Wafer-Scale Assembly of Highly Ordered Semiconductor Nanowire Arrays by Contact Printing”, Nano Letters, 8, 20-25, 2008.


Fan Z.*, Ho J.C.*, Jacobson Z., Razavi H., Javey A. “Large Scale, Heterogeneous Integration of Nanowire Arrays for Image Sensor Circuitry”, Proceedings of the National Academy of Sciences (PNAS), 105, 11066-11070, 2008.


Fan Z., Ho J.C., Takahashi T., Yerushalmi R., Takei K., Chueh Y.L., Javey A. “Towards the Development of Printable Nanowire Electronics and Sensors”, Advanced Materials, 21, 3730-3743, 2009.


Takei K., Takahashi T., Ho J.C., Ko H., Gillies A.G., Leu P.W., Fearing R.S., Javey A. "Nanowire active matrix circuitry for low-voltage macro-scale artificial skin", Nature Materials, 9, 821–826, 2010.



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