Ms. Paula P. Provencio Profile

Paula P. Provencio

Member of Technical Staff at Sandia National Labs

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Publications (4)

Proceedings Article | 14 September 2005 Paper

μ-PIXE and X-PIXE for radiological forensics

Paula Provencio, Barney Doyle, Arlyn Antolak, Daniel Morse, Charles Richardson

Proceedings Volume 5923, 592304 (2005) https://doi.org/10.1117/12.625265

KEYWORDS: Statistical analysis, Cobalt, Forensic science, X-rays, Sensors, Particles, Chemical elements, Ion beams, Beam analyzers, X-ray detectors

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Proceedings Article | 1 September 2005 Paper

Active interrogation using low-energy nuclear reactions

Arlyn Antolak, Barney Doyle, Ka-Ngo Leung, Daniel Morse, Paula Provencio

Proceedings Volume 5923, 592303 (2005) https://doi.org/10.1117/12.624973

KEYWORDS: Gamma radiation, Ions, Signal detection, Sensors, Inspection, Photons, Lithium, Laser induced fluorescence, Target detection, Plasma

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Proceedings Article | 5 November 2002 Paper

Optical properties of II-VI semiconductor nanoclusters for use as phosphors

Jess Wilcoxon, Paula Newcomer

Proceedings Volume 4808, (2002) https://doi.org/10.1117/12.451976

KEYWORDS: Absorbance, Cadmium sulfide, Optical properties, Semiconductors, Interfaces, Group II-VI semiconductors, Particles, Metals, Cadmium, Light emitting diodes

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The optical properties of both II-VI (direct gap) and type IV (indirect gap) nanosize semiconductors are significantly affected not only by their size, but by the nature of the chemical interface of the cluster with the embedding medium. This affects the light conversion efficiency and can alter the shape and position (i.e. the color) of the photoluminescence (PL). As the goal of our work is to embed nanoclusters into either organic or inorganic matrices for use as near UV, LED-excited phosphor thin films, understanding and controlling this interface is very important for preserving the high Q.E. of nanoclusters known for dilute solution conditions. We describe a room temperature synthesis of semiconductor nanoclusters which employs inexpensive, less toxic ionic precursors (metal salts), and simple coordinating solvents (e.g. tetrahydrofuran). This allows us to add passivating agents, ions, metal or semiconductor coatings to identical, highly dispersed bare clusters, post-synthesis. We can also increase the cluster size by heterogeneous growth on the seed nanoclusters. One of the most interesting observations for our II-VI nanomaterials is that both the absorbance excitonic features and the photoluminescence (PL) energy and intensity depend on the nature of the surface as well as the average size. In CdS, for example, the presence of electron traps (i.e Cd(II) sites) decreases the exciton absorbance peak amplitude but increases the PL nearly two-fold. Hole traps (i.e. S(II)) have the opposite effect. In the coordinating solvents used for the synthesis, the PL yield for d~2 nm, blue emitting CdSe clusters increases dramatically with sample age as the multiple absorbance features sharpen. Liquid chromatographic (LC) separation of the nanoclusters from other chemicals and different sized clusters is used to investigate the intrinsic optical properties of the purified clusters and identify which clusters are contributing most strongly to the PL. Both LC and dynamic light scattering, show that as the nanocluster concentration approaches 1 x 10^-4M and above, a large loss in light emission occurs due to association or "clumping" of clusters. Overcoming this natural tendency toward aggregation may be the most significant technical obstacle to the use of nanoclusters in thin film phosphors.

Proceedings Article | 14 September 1998 Paper

Characterization of amorphous carbon films grown by pulsed laser deposition

Michael Siegal, Luz Martinez-Miranda, N. DiNardo, David Tallant, John Barbour, Paula Newcomer Provencio

Proceedings Volume 3343, (1998) https://doi.org/10.1117/12.321617

KEYWORDS: Carbon, Chemical species, Raman spectroscopy, Scanning tunneling microscopy, Atomic force microscopy, Spectroscopy, Reflectivity, Diamond, Crystals, Interfaces

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