Oxidation of Pd(553): From ultrahigh vacuum to atmospheric pressure

A high-voltage terminal has been constructed for housing the various power supplies and metering circuits required by the field-emission gun (described elsewhere in these Proceedings) for the high-coherence microscope. The terminal is cylindrical in shape having a diameter of 14 inches and a length of 24 inches. It is completely enclosed by an aluminum housing filled with Freon-12 gas at essentially atmospheric pressure. The potential of the terminal relative to ground is, of course, equal to the accelerating potential of the microscope, which in the present case, is 150 kilovolts maximum.

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Electron microscope characterization of MOCVD-grown gap layers on Si

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100144991 ◽

1986 ◽

Vol 44 ◽

pp. 724-725

Author(s):

K.M. Jones ◽

M.M. Al-Jassim ◽

J.M. Olson

Keyword(s):

Atmospheric Pressure ◽

Vapour Deposition ◽

Chemical Vapour ◽

Organic Chemical ◽

Lattice Match ◽

Si Substrates ◽

Metal Organic ◽

Good Lattice ◽

Antiphase Domains

The epitaxial growth of III-V semiconductors on Si for integrated optoelectronic applications is currently of great interest. GaP, with a lattice constant close to that of Si, is an attractive buffer between Si and, for example, GaAsP. In spite of the good lattice match, the growth of device quality GaP on Si is not without difficulty. The formation of antiphase domains, the difficulty in cleaning the Si substrates prior to growth, and the poor layer morphology are some of the problems encountered. In this work, the structural perfection of GaP layers was investigated as a function of several process variables including growth rate and temperature, and Si substrate orientation. The GaP layers were grown in an atmospheric pressure metal organic chemical vapour deposition (MOCVD) system using trimethylgallium and phosphine in H2. The Si substrates orientations used were (100), 2° off (100) towards (110), (111) and (211).

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Microstructure and reactivity of small metal particles: The role of Ce additives

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100121995 ◽

1992 ◽

Vol 50 (1) ◽

pp. 318-319

Author(s):

L.D. Schmidt ◽

K. R. Krause ◽

J. M. Schwartz ◽

X. Chu

Keyword(s):

Atmospheric Pressure ◽

Noble Metals ◽

Mixed Oxides ◽

Catalytic Properties ◽

Chemical Shifts ◽

Catalytic Converter ◽

Structural Evolution ◽

Single Particles ◽

Small Metal Particles

The evolution of microstructures of 10- to 100-Å diameter particles of Rh and Pt on SiO2 and Al2O3 following treatment in reducing, oxidizing, and reacting conditions have been characterized by TEM. We are able to transfer particles repeatedly between microscope and a reactor furnace so that the structural evolution of single particles can be examined following treatments in gases at atmospheric pressure. We are especially interested in the role of Ce additives on noble metals such as Pt and Rh. These systems are crucial in the automotive catalytic converter, and rare earths can significantly modify catalytic properties in many reactions. In particular, we are concerned with the oxidation state of Ce and its role in formation of mixed oxides with metals or with the support. For this we employ EELS in TEM, a technique uniquely suited to detect chemical shifts with ∼30Å resolution.

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