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Christopher Roper
Alumnus - Ph.D. Student

Ph.D. in Chemical Engineering, University of California, Berkeley (2007)
B.S. in Chemical Engineering, Case Western Reserve University, Cleveland, Ohio (2002)

Email:

csroper (at) hrl.com

Current Position:

Senior Research Staff Engineer
Bio and Nano Materials Technologies
Sensors and Materials Laboratory
HRL Laboratories, LLC
3011 Malibu Canyon Road
Malibu, CA 90265

Research:
Development of SiC for MEMS and NEMS Devices
Silicon Carbide (SiC) is a material well-suited for a variety of Microelectromechanical Systems (MEMS) and Nanoelectromechanical Systems (NEMS) applications. The ability of SiC to tolerate high temperatures, high radiation dosages, high temperature oxidizing environments, and corrosive environments makes SiC based MEMS/NEMS well-suited for harsh environment applications. In addition, its high Young's Modulus to density ratio in comparison to materials such as Silicon and Silicon Germanium makes it an ideal candidate for ultra high frequency MEMS/NEMS resonators. 

In order to make SiC a standard MEMS/NEMS material, a large-scale deposition method with which residual stress, strain gradient, and electrical resistivity can be controlled is necessary. SiC can now be uniformly deposited via Low Pressure Chemical Vapor Deposition (LPCVD) from the precursor 1,3-disilabutane  in a 100 mm and 150 mm wafer capable reactor. My research has lead to the ability to control residual stress over two orders of magnitude, strain gradient over two orders of magnitude, and resistivity over seven orders of magnitude. Current efforts are focused on understanding the methods of stress control through Transmission Electron Microscopy (TEM).

Top-Down Silicon Nanowire Resonators
Nanowire or nanotube based devices promise many novel capabilities, including devices with ballistic conduction, higher device density, and ultra-sensitive mass and chemical sensors. However, current difficulties with control of nanowire placement (relative to electrodes and other nanowires), electrical contact to nanowires, and large-scale integration of devices prevent these devices from being fabricated in quantities larger than individual devices or in small lots.

By using inherently scalable, top-down microfabrication techniques, which are traditionally used to produce MEMS and microelectronics, these difficulties can be overcome. My research focuses on developing massively scalable methods to integrate silicon nanowires into NEMS. Top down methods can now be used to create arrays of precisely positioned and electrically contacted nanowires of chosen dimensions. In addition, top-down techniques can be used to fabricate multiple electrodes with nanoscale gaps to individual nanowires for capacitive electrostatic actuation and detection. Current efforts focus on the chemical modification and electrical testing of such devices.

Ph.D. Thesis: Silicon Carbide Thin Films via Low Pressure Chemical Vapor Deposition for Micro- and Nano-electromechanical Systems (2007)

Advisors: Prof.'s Roya Maboudian and Roger T. Howe.