Professor, Chemical Physics
S531B, Science Building
The spectroscopic identification and physico-chemical characterization of atomic-scale defects and impurity elements in semiconductor materials is important for the development of electronic devices such as diodes and transistors. Electrically active defects in these materials can trap electric charge carriers leading to poor device performance or failure.Electron paramagnetic resonance (EPR) spectroscopy detects the presence of unpaired electrons in materials. It is is one of the principal spectroscopic techniques used to detect and characterize electrically active defects in semiconductor materials. In many cases a definitive structural identification is possible from an EPR study. This is more likely when the unpaired electron of the defect center interacts with nearby nuclei that have a magnetic moment giving rise to hyperfine structure in the EPR spectrum. At the important Si/SiO2 interface, for example, Si dangling bond defects are readily formed and must be passivated with hydrogen to achieve the electrical characteristics required for metal-oxide-semiconductor transistors. The work I've done with associates at the US Army Research Laboratory involved the study of the nature of silicon dangling bond defects at the Si/SiO2 interface (referred to as Pb centers). Specifically, we were able to determine the energy levels of Pb centers in the silicon bandgap on the (100) surface. We also identified the critical role of water in the oxidation ambient as the most liklely cause of the negative-bias-temperature instability of metal-oxide-semiconductor transistors. We also studied the effects of Pb centers in the luminescence of porous silicon. Other work involved spin-dependent recombination in silicon diodes, gallium arsenide surface passivation, and impurity-band conduction in aluminum-doped silicon carbide. Present work concerns the study of aluminum-ion implantation of silicon carbide and dopant activation by thermal annealing.
- "Electrical, CL, EPR and RBS study of annealed SiC implanted with Al or Al and C," K.A. Jones, M.A. Derenge, M.H. Ervin, P.B. Shah, J.A. Freitas, R. D. Vispute, and G. J. Gerardi, Phys. Stat. Sol.(a) 201, No 3 486-496 (2004)
- "Paramagnetic Centers in Al-Doped 6H-SiC: Temperature and Concentration Effects," G. J. Gerardi, E . H. Poindexter, and D. J. Keeble, Journal of Applied Physics 87, No.4,1914-1920 (2000).
- "Contribution of Pb Centers to Midgap Interface Trap Density in Oxidized (100) Wafers," E. H. Poindexter, G. J. Gerardi, and D. J. Keeble, Electrochemical Society Proceedings Volume 99-6, 120-127 (1999).
- "Hydrogenous Species and Charge Defects in the Si-SiO2 System," E. H. Poindexter, C. F. Young, G. J. Gerardi, Fundamental Aspects of Ultra-Thin Dielectrics on Si-Based Devices, Ed. by E. Garfunkel, E. Gusev, and A. VulÕKluwer, Academic Press, Dordrecht, NL, 397- 410 (1998)
- "Electron Paramagnetic Resonance of Porous Silicon:Observation and identification of conduction-band electrons," C. F. Young, E. H. Poindexter, G. J. Gerardi, Journal of Applied Physics 81, No.11, 7468-7470 (June 1997).
- "Electron Paramagnetic Resonance Investication of Acceptor Centers in Pb(Zr,Ti)O3 Ceramics ," William L. Warren, Bruce A. Tuttle, E. Christopher Rong, Gary J. Gerardi, and Edward H. Poindexter, Journal of the American Ceramic Society 80 (3), page 680 (1997).
- "Electron Paramagnetic Resonance of Nitrogen Pairs and Triads in 6H-SiC:Analysis and Identification," C. F. Young, K. Xie, E. H. Poindexter, G. J. Gerardi, D. J. Keeble. Applied Physics Letters 70, No.14,1858-1860 (1997).
- "Paramagnetic Centers and Dopant Excitation in Crystalline Silicon Carbide," G. J. Gerardi, E. H. Poindexter, D. J. Keeble, Applied Spectroscopy, (Nov.1996).
- "Electron Paramagnetic Resonance Studies of Impurity Defects in PbTiO3", D. J. Keeble, E. H. Poindexter, G. J. Gerardi, Applied Spectroscopy 51, No.1, 117-122 (Jan.1996).
- "Hydrogen Speciation in Electronic Silica," E. H. Poindexter, G. J. Gerardi, D. J. Keeble, The Physics and Chemistry of SiO2 and the Si-SiO2 Interface - 3 ,Vol. 96-1, p172-183, The Electrochemical Society, Pennington, NJ, 1996
- "Nature of Pb-like dangling orbital centers in luminescent porous silicon," F. C. Rong, G. J. Gerardi, J. F. Harvey, E. H. Poindexter, Appl. Phys. Lett. 63, 920 (1993).
- "GaAs Surface Stabilization By Vacuum Anneal with SiO,"AMORPHOUS INSULATING THIN FILMS , G. J. Gerardi, F. C. Rong, E. H. Poindexter, M. Harmatz, H. Shen, W.L. Warren, Materials Research Society 284, 601 (1993).
- "Study of a paramagnetic center on an SiO-treated GaAs surface," G.J. Gerardi, F.C. Rong, E. H. Poindexter, M.Harmatz, H. Shen, W.L. Warren, Colloids and Surfaces A 72, 161 (1993).
- "Observation of Paramagnetic Silicon Dangling Orbitals in Luminescent Porous Silicon," F. C. Rong, G. J. Gerardi, E.H.Poindexter, J.F.Harvey, D.C.Morton, R.A.Lux, MICROCRYSTALLINE SEMICONDUCTORS , Materials Research Society 283, 167 (1993).
- "Paramagnetic Defects at the Si/SiO2 Interface of Oxidized Si Wafers in Luminescent Porous Si," E. H. Poindexter, F. C. Rong, J. F. Harvey, and G. J. Gerardi, Light Emission and Electronic Properties of Nanoscale Silicon, editors: R. Tsu, J. Harvey, J. Zavada, J. Prater, H. Leamy, UNC Charlotte Pub. (1993).
- "Electrically-detected magnetic resonance near the p-doped/n-doped interface of Si junction diodes," E.H. Poindexter F. C. Rong, W.R. Buchwald, G. J. Gerardi, D. J. Keeble, W. L. Warren, Colloids and Surfaces A 72,119 (1993).
- "Identification and Properties of Pb-like Centers in Photoluminescent Porous Silicon," F.C. Rong, J. F. Harvey, E. H. Poindexter, G. J. Gerardi, Microelectronic Engineering 22, 147 (1993).
- "Electrically detected magnetic resonance of a transition metal related recombination center in Si p-n diodes," F.C. Rong, G.J. Gerardi,W.R. Buchwald, E. H. Poindexter, Appl. Phys. Lett. 60, 610 (1992).
- "Depassivation of Damp-Oxide Pb Centers by Thermal and Electric Field Stress," G. J. Gerardi, E.H. Poindexter, M. Harmatz,W.L. Warren, E.H. Nicollian, A.H. Edwards.J. Electrochem. Soc. 138, No. 12, 3766 (1991).
- "Structural Identification of the Silicon and Nitrogen Dangling-bond Centers in Amorphous Silicon Nitride," F. C. Rong, G. J. Gerardi, E. H. Poindexter, M. Harmatz,W. R. Buchwald, J. Appl. Phys. 70, 346 (1991).
- "Low-Temperature Electron Spin Resonance Investigations of Silicon Paramagnetic Defects in Silicon Nitride," W.L. Warren, G.J. Gerardi, F.C. Rong, E. H. Poindexter, J. Kanicki, Appl. Phys. Lett. 58, 2417 (1991).
- "Depassivation of Pb Sites by Heat and Electric Field," E. H. Poindexter, G. J. Gerardi, W. R. Buchwald, D. J. Keeble, Insulating Films on Semiconductors, IOP Publishing Ltd. (1991).
- "Structural Identification of the Silicon and Nitrogen Dangling-Bond Centers in Amorphous Silicon Nitride," W. L. Warren, F.C. Rong, E. H.Poindexter, G. J. Gerardi, J. Kanicki, IBM Research Reports, Solid State Physics, RC16708 (1991).
- "Electrically Detected Magnetic Resonance In p-n JunctionDiodes," F. C. Rong, G. J. Gerardi, E. H. Poindexter, M. Harmatz, W. R. Buchwald, Solid State Commun. 76, No.8,1083 (1990).
- "Low-Temperature PECVD Si3N4 Films for GaAs Encapsulation and Passivation," R. L. Pfeffer, G. J. Gerardi, R. A. Lux, K. A. Jones, E. H. Poindexter, W. H. Chang, R. A. Devine, Characterization of Plasma-Enhanced CVD Processess, Materials Research Society 165, p.277 (1990).
- " Electric Field-Induced Proton Transfer in Oxidized Silicon: An EPR Study," E. H. Poindexter, G.J. Gerardi, Colloids and Surfaces 45 , 213 (1990).
- "Electron Paramagnetic Study of a Superconducting Crystal of the Tl-Ca-Ba-CuO System," D. J. Keeble, D. S. Ginley, E. H. Poindexter, G. J. Gerardi, W.R. Buchwald, J. Physics: Condensed Matter 1, No. 41,7741 (1990).
- "EPR and Microwave absorption measurements on T12Ca2Ba2Cu3010," D. J. Keeble, D. S. Ginley, E. H. Poindexter, G. J. Gerardi, Physics and Materials Science of High Temperature Superconductors, pp 439-444. Kluwer Academic Publishers (1990).
- "Generation of Pb Centers by High Electric Fields: Thermochemical Effects,"G. J. Gerardi, E. H. Poindexter, P. J. Caplan , M. Harmatz, R. Buchwald, J. Electrochem. Soc. 136, No. 9, 2609 (1989).
- "Generation of Pb Centers by Negative Corona Stress Across the Si/SiO2 Interface,"G. J. Gerardi, E. H. Poindexter, P.J. Caplan , M. Harmatz, R. Buchwald, J. Electrochem. Soc. 136, No. 2, 588 (1989).
- "Electrical and Optical Characterization of Metastable Deep-Level Defects in GaAs," W. R. Buchwald, G. J. Gerardi, E.H. Poindexter, N.M. Johnson, H.G.Grimmeiss, D. J. Keeble, Physical Review B 40, Aug.(1989).
- "Optical and Electrical Studies of Interface Traps in the Si/SiO2 System by Modified Junction Space Charge Techniques," H. G. Grimmeiss,W. R. Buchwald, E. H. Poindexter, P. J. Caplan, M.Harmatz, G. J. Gerardi, N. M. Johnson, D. J. Keeble, Physical Review B 39, (1989).
- "Chemical and Structural Features of Inherent and Process-Induced Defects in Oxdized Silicon," E.H. Poindexter, P.J. Caplan, G. J. Gerardi, The Physics and Chemistry of SiO2 and the Si/SiO2 Interface, p. 299, Plenum, New York (1988).
- "An Electron Paramagnetic Resonance Study of Electron Injected Oxides in Metal-Oxide-Semiconductor Capacitors," L. P. Trombetta, G. J. Gerardi, D. J. DiMaria, E. Tierney, J. Appl. Phys. 64, 2434 (1988).
- "Interface Traps and Pb Centers in Oxidized Silicon Wafers," G. J. Gerardi, E. H. Poindexter, P. J. Caplan and N. M. Johnson, Appl. Phys. Lett. 49, 348 (1986).
- "Electronic Traps and Pb Centers at the Si/SiO2 Interface: Band-gap Energy Distributuion," E. H. Poindexter, G. J. Gerardi, M. E. Rueckel, P.J. Caplan, N. M. Johnson, D. K. Biegelsen, J. Appl. Phys. 56, 2844 (1984).
- "Weak Intermolecular CH3-O and P-H-O Hydrogen-Bonding Interactions in Liquids," G. J. Gerardi, J.A. Potenza, J. Phys. Chem. 85, 2034 (1981).
- "Hydrogen Bonding in Systems Containing Imidazoline Nitroxide Radicals," G. J. Gerardi, B. E. Wagner, J. Chem. Phys. 69, 4645 (1978).
- "Determining Ionization and Solubility Product Constants Using a Simple Conductivity Apparatus," G. J. Gerardi, Journal of College Science Teaching 6, 166 (1977).
- "Corresponding States of CH4 and CF4 and their Mixtures," E. M. Holleran, G. J. Gerardi, J. Phys. Chem. 72, 528 (1969).
- "The Unit Compressibility Law for Mixtures," E. M. Holleran, G. J. Gerardi, J. Phys. Chem. 73, 525 (1969).
- "Corresponding States of Argon and Methane," E. M. Holleran, G. J. Gerardi, J. Phys. Chem. 72, 3559 (1968).
Professor - William Paterson University (1977-Present). Teaching: Physical Chemistry, General Physics, Electronics.
Visiting Research Scientist- IBM T. J. Watson Research Laboratory- Summer 2001. EPR study of high-K dielectrics.
Research Physicist-US Army Research Laboratory, Ft.Monmouth, NJ (1981-1985). Electron paramagnetic resonance studies of point electrical defects in semiconductors.
Research Associate - Rutgers University, New Brunswick, N.J. (1976 -1980). Study of weak intermolecular interactions in liquidsusing dynamic nuclear polarization (DNP).
Assistant Professor- College of New Jersey (1972-1977). Teaching: Spectroscopy, General Chemistry, Physical Chemistry.
Instructor- York College- City University of NY (1968-1972). Teaching: Physical Chemistry, Physics, Mathematics, Advanced Inorganic Chemistry.
Postdoctoral Research- Louisiana State University (1969-1970). Quantum Chemistry: Electron correlation energy of the 1s-hole state of neon.
Ph.D. Chemical Physics- St. John's University (1969)
M.S. Physical Chemistry- St. John's University (1965)
B.S. Chemistry - Manhattan College (1963)