FY 1990 Applied Sciences Branch annual report

Abstract

V l l l (AES); scanning Auger microscopy (SAM); X-ray photoelectron spectroscopy (XPS); electron energy loss spectroscopy (EELS); electron-stimulated desorption spectroscopy (ESD); electron-beam-induced current and voltage (EBIC and EBIV) ; Auger voltage contrast (AVC) : high-resolution elemental and ionic mapping, including volume-indexing; cooperative soft x-ray synchrotron-source analysis; scanning tunneling microscopy (STM) ; and molecular beam epitaxy (MBE). Materials CharacterizationThis group employs advanced microscopy and microanalytical techniques in the determination of crystallographic, defect topographic, compositional, and microelectrical properties of photovoltaic materials and devices. These include electron probe microanalysis (EPMA) with energy dispersive and wavelength dispersive spectroscopy (EDS and WDS) : scanning electron microscopy (SEM) to liquid helium temperatures; scanning transmission electron microscopy (TEM and STEM); voltage contrast; electron-beaminduced current and voltage characterization: electron diffraction: electron channeling; image analysis; X-ray diffraction; X-ray fluorescence; microcathodoluminescence; cooperative high-resolution interface analysis using high-voltage electron microscopy: and complete sample preparation facilities, including ion etching with integral SIMS analysis. Device DevelopmentThis group provides modeling and fabrication support for the development of cell structures, including; diagnostic device preparation, optical conducting film fabrication and studies, thin-film and space cells, and computer analysis and design. Capabilities include; precision sputtering equipment for deposition of optical films, antireflection coatings, metallizations, transparent conductors, etc. ; research clean room facilities; III-V cell processing capabilities; photolithography and mask design and fabrication; InP-alloy metal-organic chemical vapor deposition (MOCVD) ; optical and electrical characterization for films and coatings: plasma deposition; photoconductivity, and ellipsometry; contact resistance determinations: and computer modeling programs for optical coatings and solar cell design. 1.2.4Electro-Optical Characterization The work of this group involves determination of the electrical and optical properties of materials and solar cells; and laser spectroscopies, including photoluminescence and specialized determinations of minority-carrier properties. Capabilities and techniques include capacitance-voltage, conductance-voltage, and temperature dependences; Hall effect/van der Pauw measurements; laser scanning: deep-level transient spectroscopy I 4 I 2.8 SURFACE AND INTERFACE ANALYSIS 2.1 RESEARCH STAFF