Chemical Changes of the Atmosphere on Geological and Recent Time Scales

Global Atmospheric Chemical Change ◽

10.1007/978-94-011-1864-4_1 ◽

1993 ◽

pp. 1-52

Author(s):

Peter Warneck

Keyword(s):

Time Scales ◽

Recent Time ◽

Chemical Changes

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Physical and chemical changes in the ocean over basin-wide zones and decadal or longer time-scales: perspectives on current and future conditions

Ocean Sustainability in the 21st Century ◽

10.1017/cbo9781316164624.006 ◽

2015 ◽

pp. 54-83

Author(s):

Gunnar Kullenberg ◽

Eddy Carmack ◽

Kenneth Denman

Keyword(s):

Time Scales ◽

Chemical Changes ◽

Physical And Chemical

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LVSEM: Past Present and Future

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100180574 ◽

1990 ◽

Vol 48 (1) ◽

pp. 364-365

Author(s):

James B. Pawley

Keyword(s):

Field Emission ◽

Line Width ◽

Time Scales ◽

Silicon Oxide ◽

Beam Current ◽

High Brightness ◽

High Beam ◽

Fixed Charges ◽

Beam Voltage ◽

Deposited Metal

Past: In 1960 Thornley published the first description of SEM studies carried out at low beam voltage (LVSEM, 1-5 kV). The aim was to reduce charging on insulators but increased contrast and difficulties with low beam current and frozen biological specimens were also noted. These disadvantages prevented widespread use of LVSEM except by a few enthusiasts such as Boyde. An exception was its use in connection with studies in which biological specimens were dissected in the SEM as this process destroyed the conducting films and produced charging unless LVSEM was used.In the 1980’s field emission (FE) SEM’s came into more common use. The high brightness and smaller energy spread characteristic of the FE-SEM’s greatly reduced the practical resolution penalty associated with LVSEM and the number of investigators taking advantage of the technique rapidly expanded; led by those studying semiconductors. In semiconductor research, the SEM is used to measure the line-width of the deposited metal conductors and of the features of the photo-resist used to form them. In addition, the SEM is used to measure the surface potentials of operating circuits with sub-micrometer resolution and on pico-second time scales. Because high beam voltages destroy semiconductors by injecting fixed charges into silicon oxide insulators, these studies must be performed using LVSEM where the beam does not penetrate so far.

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