George Research Group
Surface Chemistry, Thin Film Growth & Nanostructure Engineering
Focus on Atomic Layer Deposition & Molecular Layer Deposition
Miniaturization to the nanometer scale has been one of the most important trends in science and technology over the past decade. The chemistry to fabricate nanolayers, the engineering for nanocomposite design and the physics of nanostructure properties have created many exciting opportunities for research. These new interdisciplinary areas in nanoscience and nanotechnology supersede the more traditional disciplines and demand new paradigms for collaboration.
Our research is focusing on the fabrication, design and properties of ultrathin films and nanostructures. We are developing new surface chemistries for thin film growth, measuring thin film growth using in situ techniques and characterizing thin film properties. This research is relevant to many technological areas such as semiconductor processing, flexible displays, MEMS/NEMS, Li ion batteries and fuel cells. Our research bridges many disciplines and we have collaborators in the Departments of Chemistry, Chemical Engineering, Mechanical Engineering and Physics on campus and many others at universities, industries and national laboratories off campus.
Many of our surface chemistry and thin film growth investigations utilize atomic layer deposition (ALD) techniques [1]. ALD is based on sequential, self-limiting surface reactions as illustrated in the accompanying figure. This unique growth technique can provide atomic layer control and allow conformal films to be deposited on very high aspect ratio structures. ALD methods and applications have developed rapidly over the last ten years. ALD is on the semiconductor road map for high-k gate oxides and diffusion barriers for backend interconnects. ALD is also employed in magnetic read-write heads and is employed to fabricate capacitors for DRAM.
ALD is based on sequential, self-limiting surface chemical reactions. One of the classic ALD systems is Al2O3ALD. Al2O3 ALD is based on the binary reaction: 2Al(CH3)3 + 3H2O -> Al2O3 + 6CH4 can can be split into the following two surface half-reactions [2,3]:
A) AlOH* + Al(CH3)3 -> AlOAl(CH3)2* + CH4
B) AlCH3* + H2O -> AlOH* + CH4
where the asterisks denote the surface species. In the (A) reaction, Al(CH3)3 reacts with the hydroxyl (OH*) species and deposits aluminum and methylates the surface. The (A) reactions stops after all the hydroxyl species have reacted with Al(CH3)3. In the (B) reaction, H2O reacts with the AlCH3* species and deposits oxygen and rehydroxlates the surface. The (B) reactions stops after all the methyl species have reacted with H2O. Because each reaction is self-limiting, the Al2O3 deposition occurs with atomic layer control.
More Information can be found on the George Research Group Website.
