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Hagmann, Mark J.,Mousa, Marwan S.,Yarotski, Dmitry A. Korean Society of Microscopy 2017 Applied microscopy Vol.47 No.3
High resolution measurements of the carrier profile in semiconductor devices is required as the semiconductor industry progresses from the 10-nm lithography node to 7-nm and beyond. We examine the factors which determine the resolution of the present method of scanning spreading resistance microscopy as well as such factors for the newer method of scanning frequency comb microscopy that is now under development. Also, for the first time, we consider the sensitivity of both methods to the location of heterogeneities in the semiconductor. In addition, mesoscopic effects on these measurements are considered for the first time. Two simple analytical models are extended to study the sensitivity to heterogeneities as well as mesoscopic effects.
Enhanced Field Electron Emission from Dielectric Coated Highly Emissive Carbon Fibers
Almarsi, Ayman M.,Hagmann, Mark J.,Mousa, Marwan S. Korean Society of Microscopy 2017 Applied microscopy Vol.47 No.1
This paper describes experiments aimed at characterizing the behavior of field electron emitters fabricated by coating carbon fibers with epoxylite resin. Polyacrylonitrile carbon fibers of type VPR-19, thermally treated at $2,800^{\circ}C$, were used. Each was initially prepared in a "uncoated" state, by standard electro polishing and cleaning techniques, and was then examined in a scanning electron microscope. The fiber was then baked overnight in a field electron microscope (FEM) vacuum chamber. Current-voltage characteristics and FEM images were recorded on the following day or later. The fiber was then removed from the FEM, coated with resin, "cured" by baking, and replaced in the FEM. After another overnight bake, the FEM characterization measurements were repeated. The coated fibers had significantly better performance than uncoated fibers. This confirms the results of earlier experiments, and is thought to be due in part to the formation of a conducting channel in the resin over layer. For the coated fiber, lower voltages were needed to obtain the same emission current. The coated fibers have current-voltage characteristics that show smoother trends, with greater stability and repeatability. No switch-on phenomena were observed. In addition, the emission images on the phosphor-coated FEM screen were more concentrated, and hence brighter.
SQUID-Based Microwave Cavity Search for Dark-Matter Axions
Asztalos, S. J.,Carosi, G.,Hagmann, C.,Kinion, D.,van Bibber, K.,Hotz, M.,Rosenberg, L. J,Rybka, G.,Hoskins, J.,Hwang, J.,Sikivie, P.,Tanner, D. B.,Bradley, R.,Clarke, J. American Physical Society 2010 Physical Review Letters Vol.104 No.4
<P>Axions in the microeV mass range are a plausible cold dark-matter candidate and may be detected by their conversion into microwave photons in a resonant cavity immersed in a static magnetic field. We report the first result from such an axion search using a superconducting first-stage amplifier (SQUID) replacing a conventional GaAs field-effect transistor amplifier. This experiment excludes KSVZ dark-matter axions with masses between 3.3 microeV and 3.53 microeV and sets the stage for a definitive axion search utilizing near quantum-limited SQUID amplifiers.</P>
The Effects of Dielectric Coatings on Electron Emission from Tungsten
Al-Qudah, Ala'a M.,Alnawasreh, Shady S.,Madanat, Mazen A.,Trzaska, Oliwia,Matykiewicz, Danuta,Alrawshdeh, Saad S.,Hagmann, Mark J.,Mousa, Marwan S. Korean Society of Microscopy 2017 Applied microscopy Vol.47 No.1
Field electron emission measurements were performed on dielectric-coated tungsten emitters, with apex radii in the nanometer and micrometer range, which were prepared by electrochemical etching in NaOH solution. Measurements were performed in a field electron microscopy (FEM) with a base pressure <$10^{-6}$ Pascal ($10^{-8}$ mbar). Four different types of dielectric were used, namely: (1) Clark Electromedical Instruments epoxylite resin, (2) Epidian 6 produced by Ciech Sarzyna S. A., (3) a Radionox solution of colloidal graphite; and (4) Molyslip 2001 E compound ($MoS_2$ and MoS). Current-voltage measurements and FEM images were used to investigate the characteristics of these composite emitters, and to assess how the different types of dielectric coating affect the suitability of the composite emitter as a potential electron source.