Prof. Atwater received his Ph. D. from Massachusetts Institute of Technology in 1987. He was an IBM Postdoctoral Fellow in Applied Physics at Harvard. In 1989 he received the NSF Presidential Young Investigator Award, and the IBM Faculty Development Award.
Our research group is engaged in fundamental and applied research in synthesis, properties and processing of electronic materials for use in the electronic and optoelectronic devices and circuits of the 21st century. Electronic materials research is interdisciplinary, involving issues spanning applied physics, physics, materials science, electrical and chemical engineering. Our group includes graduate students, research fellows and undergraduates from each of these departments. We also maintain comprehensive experimental facilities for growth and analysis. The group's research efforts cross several areas. As silicon integrated circuit technology is the dominant large-scale electronics technology, a significant effort in our group is aimed at exploring new silicon-compatible materials and structures which may enable new functions and performance to be readily combined in the future with the powerful integrated circuit technology of today. These include study of the growth and optical/electronic properties of new epitaxial group IV compound semiconductors and nanocrystalline group IV structures for potential heterojunction and optoelectronic device applications. Advanced epitaxial growth processes are enabled by new in situ diagnostics using reflection electron energy loss spectroscopy. Polycrystalline semiconductors thin films, having enormous potential applications in thin film solar cells and display devices, are another important research area. Research on polycrystalline GaAs/Ge and Si thin film growth and microstructure is aimed at developing low-cost high-efficiency thin film solar cells. The interconnects in large-scale circuits, which consist of intricate arrays of polycrystalline metal films sandwiched between dielectrics, are of increasingly critical importance in overall circuit performance. We are studying new approaches to fabrication of high aspect ratio submicron polycrystalline metal structures for applications in high-density integrated circuit interconnects.
We are investigating synthesis, electronic and optical properties new lattice-matched and strained group IV compound semiconductor structures, including C_xSi_{1-x}, Sn_xGe_{1-x}, (C_xGe_{1-x})_ySi_{1-y}, (C_xSn_{1-x})_ySi_{1-y}. For example, the Sn_xGe_{1-x} system offers the possibility of group IV alloy with a tunable, direct energy bandgap in the infrared, with the potential for making low-cost infrared detector arrays directly integrated onto silicon substrates.
In Situ Diagnostic Techniques for Advanced Growth: Our research group recently pioneered the technique of reflection electron energy loss spectroscopy (REELS) for in situ surface analysis during semiconductor epitaxial growth. This electron spectroscopy technique involves spectral analysis of reflection high energy electron diffraction (RHEED) electrons, and allows real-time measurement of the surface composition in epitaxial film growth, enabling control of alloy composition and thickness with monolayer precision.
We are investigating the optical properties of group IV semiconductor (Si, Ge, Sn) nanocrystalline materials fabricated by high energy ion implantation into silicon dioxide thin films. These materials exhibit interesting properties, such as visible luminescence at room temperature, but the luminescence mechanisms have been unclear to date, and we have focussed on distinguishing various optical features in these materials related to defects and quantum confinement of excitons in nanocrystals.
The most important challenge facing photovoltaic solar cell technology is reduction of the cost-per-watt of solar power generating capacity. Polycrystalline semiconductor cells, fabricated from semiconductor materials deposited onto inexpensive substrates have the greatest potential for low-cost solar cell technology. However, achievement of high cell efficiency in Si or GaAs requires growth of very large grain semiconductor films. We are investigating low-temperature growth processes, which involve precise control of crystallization and growth of amorphous thin films, to achieve very large (i.e. 10-100 micron) grains of Si and GaAs on glass.
Integrated circuit speed and complexity is increasingly limited, not by the transistors, but by the arrays of wires that interconnect devices. Advances in circuit integration density have placed severe constraints on the ability to fabricate these interconnects in the deep submicron regime. We are investigating approaches to fabrication of high-aspect ratio submicron interconnect structures.
We maintain state-of-the-art research facilities for electronic materials synthesis and analysis. These include: molecular beam epitaxy system, ultrahigh vacuum pulsed laser deposition system, ultrahigh vacuum sputtering system , 4-crystal X-ray diffractometer, 2 MeV Pelletron accelerator for Rutherford backscattering spectrometry and elastic recoil spectrometry, surface analysis system with scanning Auger microscopy(SAM) and X-ray photoelectron spectroscopy(XPS), Fourier transform infrared (FTIR) spectrometer, photoluminescence system, and transmission electron microscopy.
Atwater, H. A.; Wong, S. S.; Ahn, C. C.; Nikzad, S.; Frase, H. N. Analysis of Monolayer Films During Molecular-beam Epitaxy By Reflection Electron-Energy-Loss Spectroscopy. Surface Science. 1993;
Hashim, I.; Atwater, H. A.; Kung, K. T. Y.; Valletta, R. M. Evolution of Structural and Magnetic-properties In Ta/Ni81Fe19 Multilayer Thin-films. Journal of Applied Physics. 1993;
Hashim, I.; Atwater, H. A. In-situ Magnetic and Structural-analysis of Epitaxial Ni80fe20 Thin-films for Spin-Valve Heterostructures. Journal of Applied Physics. 1994;
Hashim, I.; Park, B.; Atwater, H. A. Epitaxial-growth of Cu(001) On Si(001) - Mechanisms of Orientation Development and Defect Morphology. Applied Physics Letters. 1993;
He, G.; Savellano, M. D.; Atwater, H. A. Synthesis of Dislocation-free Siy(SnxC1-X)1-Y Alloys by Molecular-beam Deposition and Solid-phase Epitaxy. Applied Physics Letters. 1994;
Murty, M. V. R.; Atwater, H. A. Crystal-state Amorphous-state Transition in Low-temperature Silicon Homoepitaxy. Physical Review B-Condensed Matter. 1994;
Murty, M. V. R.; Atwater, H. A. Empirical Interatomic Potential for Si-h Interactions. Physical Review B Condensed Matter. 1995;
Murty, M. V. R.; Atwater, H. A.; Kellock, A. J.; Baglin, J. E. E. Very Low-temperature (Less-than-400-Degrees-c) Silicon Molecular-beam Epitaxy - The Role of Low-energy Ion Irradiation. Applied Physics Letters. 1993;
Nikzad, S.; Wong, S. S.; Ahn, C. C.; Smith, A. L.; Atwater, H. A. In-situ Reflection Electron-Energy-Loss Spectroscopy Measurements of Low-temperature Surface Cleaning for Si Molecular-beam Epitaxy. Applied Physics Letters. 1993;
Saunders, W. A.; Sercel, P. C.; Flagan, R. C.; Atwater, H. A.; Vahala, K. J. The Role of Ga-Droplet Formation in Nanometer-scale GaAs Cluster Synthesis from Organometallic Precursors. Zeitschrift Fur Physik D Atoms Molecules and Clusters. 1993;
Saunders, W. A.; Sercel, P. C.; Lee, R. B.; Atwater, H. A.; Vahala, K. J.; Flagan, R. C.; Escorciaaparcio, E. J. Synthesis of Luminescent Silicon Clusters by Spark Ablation. Applied Physics Letters. 1993;
Shcheglov, K. V.; Yang, C. M.; Vahala, K. J.; Atwater, H. A. Electroluminescence and Photoluminescence of Ge-implanted Si/SiO2/Si Structures. Applied Physics Letters. 1995;
Shin, J. H.; Atwater, H. A. Activation-energy Spectrum And Structural Relaxation Dynamics of Amorphous-silicon. Physical Review B Condensed Matter. 1993;
Shin, J. H.; Atwater, H. A. In-situ Analysis of Irradiation-induced Crystal Nucleation in Amorphous-silicon - a Microscope for Thermodynamic Processes in Nucleation. Nuclear Instruments & Methods in Physics Research Section B Beam Interactions with Materials and Atoms. 1993;
Tsai, C. J.; Vreeland, T.; Atwater, H. A. Application of X-ray Interference Method for Residual Strain-measurement in Low-energy Ar Ion-bombarded Si (001). Applied Physics Letters. 1994;
Vahala, K. J.; Saunders, W. A.; Tsai, C. S.; Sercel, P. C.; Kuech, T.; Atwater, H. A.; Flagan, R. C. Lower-dimensional Quantum Structures by Selective Growth and Gas-phase Nucleation. Journal of Vacuum Science & Technology B. 1993;
Wong, S. S.; He, G.; Nikzad, S.; Ahn, C. C.; Atwater, H. A. Local Order Measurement in SnGe Alloys and Monolayer Sn Films on Si With Reflection Electron-Energy-Loss Spectrometry. Journal of Vacuum Science & Technology A Vacuum Surfaces and Films. 1995;