Thin Film Electronics

Integrated circuits are based on a semiconductor wafer — but they function because a complex, 3-dimensional architecture of dielectrics, insulators, conductive ceramics and metals is fabricated on top of the wafer. Many of these layers are only 5-10 atoms thick and must be smooth and free of pinholes over the contour of the microdevice.

Thin Film Electronics is focused on innovative science associated with synthesizing such extraordinary combinations of materials. Our work also encompasses thin films for energy applications such as solar cells, non-volatile data storage, and fundamental measurements of optical, thermal and electrical properties.

• Chemical Vapor Deposition of Electronic Materials: To fabricate advanced micro-electronic devices, ultra-thin films must be deposited conformally onto the walls of high aspect ratio features, such as the growth of <5 nm thick diffusion barriers for copper metallization. We use novel precursor molecules in the chemical vapor deposition (CVD) process to afford high performance films such as HfB2 at temperatures below 300°C. Systems under study include refractory conductors, elemental metals and oxides.

• Semiconductor Crystal Growth and Defects: Cu(In,Ga)Se2 (CIGS) is a promising material for thin film photovoltaic applications. We deposit CIGS by hybrid sputtering, including the formation of hetero-epitaxial layers on GaAs substrates, and analyze the microchemical, microstructural and electronic properties. We also model  semiconductor materials using Monte Carlo, density functional theory and continuum methods.

• Materials for Nonvolatile Memory Devices: We analyze the optical, electronic and transformation kinetics of phase-change chalcogenide glasses, such as Ag/In and Ge2Sb2Te5 alloyed Sb2Te, which are under development for non-volatile memory devices. We have shown that fluctuation transmission electron microscopy can unravel the kinetics of the crystallizationprocess by detecting the formation of subcritical nuclei in the glassy phase as a function of annealing conditions.

John Abelson: Chemical vapor deposition of electronic materials
Leslie Allen: Nanoscale properties of thin films
Steve Bishop: Materials for nonvolatile memory devices
Ivan Petrov: Sputter deposition of electronic materials
Angus Rockett: Semiconductor crystal growth and defects