Research Areas

Semiconductor Nanocrystal Materials
and Devices

Caltech People: Prof. Harry Atwater (APh), Julie Biteen, Gerald Miller, Robb Walters
Collaborators: Dr. Douglas Bell (JPL), Dr. George Bourianoff (Intel), Prof. Albert Polman (FOM Institute)


Nanocrystal Physics and Devices:

In the mesoscopic size regime, semiconductor materials have size-tunable properties that are intermediate between those of single atoms and their corresponding bulk solids. We are studying optical and transport properties of group IV semiconductor (Si and Ge) nanocrystals that behave electronically as 'quantum dots'.

Nanocrystals can be made by two methods: ion implantation and aerosol synthesis. These studies teach us a great deal about nanoscale synthesis in the sublithographic size regime, about interface passivation, excited state decay and localized state carrier transport in silicon. These materials may also be interesting in solid state devices such as high density ULSI CMOS-compatible nonvolatile memories and optical amplifiers.

Emerging Research Areas:

1. Nanocrystal Memory Devices
Floating gate field effect devices are the basis of today's nonvolatile memory technology, such as the "flash" memory chips that are the 'film' in electronic cameras and the data storage media for other portable electronic devices. Current floating gate memory designs suffer from clear performance limits. Our research effort in nanocrystal memories is aimed at overcoming these present performance hurdles by use of floating gate comprised of a dense array of silicon nanocrystals. Recently we have fabricated state-of-the-art nanocrystal floating gate nonvolatile memory devices, using a novel aerosol synthesis process for floating gate formation.


2. Layered Tunneling Barriers
Layered heterostructure tunneling barriers using novel high k-dielectric materials may hold the key to realization of Si-compatible tunneling dielectrics for floating gate nonvolatile memories that have both nano-second regime program/erase times and truly archival charge retention characteristics. The trade off between program and erase time and charge retention is currenly the largest performance obstacle in floating gate memory devices.


3. Charge Injection and Storage in Nanocrystals
We are investigating fundamental issues in the charging mechanisms for ion-implanted and deposited Si nanocrystals. We are also interested in the relationship between nanocrystal charge state and photoluminescence characteristics.


Available Presentations:

Engineered Nanoparticle Electronic and Photonic Materials
Charge Injection in Si Nanocrystals
Synthesis and Properties of Alpha-Sn Nanocrystals
Layered Tunneling Barriers
Nanocrystal Nonvolatile Memory Devices


Available Publications:

Achieving optical gain in waveguide-confined nanocluster-sensitized erbium by pulsed excitation
Gerald M. Miller, Ryan M. Briggs, and Harry A. Atwater
Journal of Applied Physics (2010)


Tunable Visible and Near-IR Emission from Sub-10 nm Etched Single-Crystal Si Nanopillars
Sameer S. Walavalkar, Carrie E. Hofmann, Andrew P. Homyk, M. David Henry, Harry A. Atwater, and Axel Scherer
Nano Letters (2010)


Broadband enhancement of light emission in silicon slot waveguides
Young Chul Jun, Ryan M. Briggs, Harry A. Atwater, and Mark L. Brongersma
Optics Express (2009)


Modifying the Radiative Quantum Efficiency of Erbium-Doped Glass in Silicon Slot Waveguides
Ryan M. Briggs, Gerald M. Miller, and Harry A. Atwater
Proceedings of the 6th IEEE Conf. on Group IV Photonics (2009)


Wafer-bonded single-crystal silicon slot waveguides and ring resonators
Ryan M. Briggs, Michael Shearn, Axel Scherer, and Harry A. Atwater
Applied Physics Letters (2009)


Plasmon-enhanced photoluminescence of Si quantum dots: Simulation and experiment
Julie S. Biteen, Luke A. Sweatlock, Hans Mertens, Nathan S. Lewis, Harry A. Atwater and Albert Polman
Journal of Physical Chemistry C (2007)


Photoluminescence quantum efficiency of dense silicon nanocrystal ensembles in SiO2
Robert J. Walters, J. Kalkman, Albert Polman, Harry A. Atwater, Michiel J.A. de Dood
Physical Review B (2006)


Polarization-Selective Plasmon-Enhanced Silicon Quantum Dot Luminescence
Hans Mertens, Julie S. Biteen, Harry A. Atwater, and Albert Polman
Nano Letters (2006)


Spectral tuning of plasmon-enhanced silicon quantum dot luminescence
Julie S. Biteen, Nathan S. Lewis, Harry A. Atwater, Hans Mertens, and Albert Polman
Applied Physics Letters (2006)


A Scalable Turbulent Mixing Aerosol Reactor for Oxide-Coated Silicon Nanoparticles
Dean M. Holunga, Richard C. Flagan, and Harry A. Atwater
Industrial & Engineering Chemistry Research (2005)


Enhanced Radiative Emission Rate and Quantum Efficiency in Coupled Silicon Nanocrystal-Nanostructured Gold Emitters
Julie S. Biteen, Domenico Pacifici, Nathan S. Lewis, Harry A. Atwater
Nano Letters (2005)


Field-effect electroluminescence in silicon nanocrystals
Robert J. Walters, George I. Bourianoff, and Harry A. Atwater
Nature Materials (2005)


Probing the size and density of silicon nanocrystals in nanocrystal memory device applications
Tao Feng, Hongbin Yu, Matthew Dicken, James R. Heath, Harry A. Atwater
Applied Physics Letters (2005)


Quenching of Si nanocrystal photoluminescence by doping with gold or phosphorous
Anna L. Tchebotareva, Michiel J.A. de Dood, Julie S. Biteen, Harry A. Atwater, and Albert Polman
Journal of Luminescence (2005)


Determination of energy barrier profiles for high-k dielectric materials utilizing bias-dependent internal photoemission
Julie C. Brewer, Robert J. Walters, L. Douglas Bell, Damon B. Farmer, Roy G. Gordon, and Harry A. Atwater
Applied Physics Letters (2004)


High Total Dose Tolerance of Prototype Silicon Nanocrystal Non-Volatile Memory Cells
Mihail P. Petkov, L. Douglas Bell, and Harry A. Atwater
IEEE Transactions on Nuclear Science (2004)


Size-dependent oxygen-related electronic states in silicon nanocrystals
Julie S. Biteen, Nathan S. Lewis, Harry A. Atwater, and Albert Polman
Applied Physics Letters (2004)


Materials issues for layered tunnel barrier structures
Julie D. Casperson, L. Douglas Bell, Harry A. Atwater
Journal of Applied Physics (2002)


Charging of Single Si Nanocrystals by Atomic Force Microscopy
Elizabeth A. Boer, L. D. Bell, Mark L. Brongersma, Harry A. Atwater, Michele L. Ostraat, and R. C. Flagan
Applied Physics Letters (2001)


Localized charge injection in SiO2 films containing silicon nanocrystals
Elizabeth A. Boer, Mark L. Brongersma, Harry A. Atwater, Richard C. Flagan, and L. Douglas Bell
Applied Physics Letters (2001)


Models for quantitative charge imaging by atomic force microscopy
Elizabeth A. Boer, L. Douglas Bell, Mark L. Brongersma, and Harry A. Atwater
Journal of Applied Physics (2001)


Space-charge effects in nanoparticle processing using the differential mobility analyzer
Renato P. Camata, Harry A. Atwater, and Richard C. Flagan
Journal of Aerosol Science (2001)


Synthesis and characterization of aerosol silicon nanocrystal nonvolatile floating-gate memory devices
Michele L. Ostraat, Jan W. De Blauwe, Martin L. Green, L. Douglas Bell, Mark L. Brongersma, Julie D. Casperson, Richard C. Flagan, Harry A. Atwater
Applied Physics Letters (2001)


Size-dependent electron-hole exchange interaction in Si nanocrystals
Mark L. Brongersma, Pieter G. Kik, Albert Polman, Kyu S. Min, and Harry A. Atwater
Applied Physics Letters (2000)


A near-infrared photoluminescence study of GaAs nanocrystals in SiO2 films formed by sequential ion implantation
Yoshihiko Kanemitsu, Hiroshi Tanaka, Takashi Kushida, Kyu Sung Min, and Harry A. Atwater
Journal of Applied Physics (1999)


Depth distribution of luminescent Si nanocrystals in Si implanted SiO2 films on Si
Mark L. Brongersma, Albert Polman, Kyu S. Min, and Harry A. Atwater
Journal of Applied Physics (1999)


Tuning the emission wavelength of Si nanocrystals in SiO2 by oxidation
Mark L. Brongersma, Albert Polman, Kyu S. Min, Elizabeth Boer, T. Tambo, and Harry A. Atwater
Applied Physics Letters (1998)


Defect-related versus excitonic visible light emission from ion beam synthesized Si nanocrystals in SiO2
Kyu S. Min, Kirill V. Shcheglov, C. M. Yang, Harry A. Atwater, Mark L. Brongersma, and Albert Polman
Applied Physics Letters (1996)


Size classification of silicon nanocrystals
Renato P. Camata, Harry A. Atwater, Kerry J. Vahala, and Richard C. Flagan
Applied Physics Letters (1996)