Micro Chemical Vapor Deposition for the Synthesis of Nanomaterials


MEMS (Microelectromechanical Systems) technologies have enabled the construction of a micro chemical vapor deposition (μCVD) system for the synthesis of nanomaterials. By means of localized resistive heating via microheaters, unique capabilities of the μCVD systems have been utilized to synthesize carbon nanotubes and graphene in this work, including fast stabilization of temperature; rapid exchange of gas species; laminar gas flow due to small Reynolds number; small diffusion length; and enhanced mass transport.

In the prototype designs, the μCVD system is composed of a suspended microheater and two contact pads constructed from the device layer ofa SOI (silicononinsulator) substrateBoth heat transfer and fluidic analyses have been conducted to validate and optimize the key features of the system. Experimental results in the synthesis of singlewalled carbon nanotubes (SWNTs) have shown that amorphous carbon formation can be deterred and ultralong SWNTs can be grown using ethylene as the source gas using μCVD system while similar experimental conditions failed to produce SWNTs in a conventional CVD system.

Further applications of the μCVD system have been successfully demonstrated, including direct placement of highquality, wellaligned SWNTs on temperature sensitive substrates such as thin paper or polymer sheets, and the synthesis of twodimensional crystalline graphene structure with good uniformity. Specifically, the construction of highperformance CNTbased devices requires highquality CNTs while conventional transfer and assembly processes often alter and degrade their properties. The localized heating of μCVD allows the directsynthesis ofselfaligned SWNTs onto flexible substrates without causing thermal damages. Both Raman spectral and transmission electron microscopy have been used to validate the quality of these SWNTs. This methodology of direct synthesis of nanomaterials could be applicable to other onedimensional nanostructures for various applications including flexible electronics. In the application to graphene growth, large area graphene with consistent number of layers has been realizedon top of a nickelcoated micro platform using the μCVD system. The capability of ultrafast heating and cooling provided by the MEMS platform is crucial for the successful growth of graphene. In the prototype graphene synthesis experiments, methane is flowed at 1.5% volume ratio with hydrogen to the platform heated to 1000ºC and the heating power is cut off after a 5min growth process. It has been demonstrated that 1~2 layers of graphene structures can be consistently grown throughout the whole 300×300 m^2platform

Publication date: 
December 31, 2011
Publication type: 
Ph.D. Dissertation
Zhou, Q. (2011). Micro Chemical Vapor Deposition for the Synthesis of Nanomaterials. United States: University of California, Berkeley.

*Only registered BSAC Industrial Members may view project materials & publications. Click here to request member-only access.