Electron emission from MIM systems and discontinuous metal films

This program has been organized by the EMSA to commensurate the 50th anniversary of the experimental verification of the wave nature of the electron. Davisson and Germer in the U.S. and Thomson and Reid in Britian accomplished this at about the same time. Their findings were published in Nature in 1927 by mutual agreement since their independent efforts had led to the same conclusion at about the same time. In 1937 Davisson and Thomson shared the Nobel Prize in physics for demonstrating the wave nature of the electron deduced in 1924 by Louis de Broglie.The Davisson experiments (1921-1927) were concerned with the angular distribution of secondary electron emission from nickel surfaces produced by 150 volt primary electrons. The motivation was the effect of secondary emission on the characteristics of vacuum tubes but significant deviations from the results expected for a corpuscular electron led to a diffraction interpretation suggested by Elasser in 1925.

Download Full-text

Macromolecular structures of biological specimens are not obscured by controlled osmium impregnation

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100076639 ◽

1983 ◽

Vol 41 ◽

pp. 606-607

Author(s):

Klaus-Ruediger Peters ◽

Samuel A. Green

Keyword(s):

Thin Films ◽

Electrical Conductivity ◽

Critical Point ◽

Metal Films ◽

High Magnification ◽

Osmium Impregnation ◽

Instrumental Resolution ◽

20 Nm ◽

Continuous Metal

High magnification imaging of macromolecules on metal coated biological specimens is limited only by wet preparation procedures since recently obtained instrumental resolution allows visualization of topographic structures as smal l as 1-2 nm. Details of such dimensions may be visualized if continuous metal films with a thickness of 2 nm or less are applied. Such thin films give sufficient contrast in TEM as well as in SEM (SE-I image mode). The requisite increase in electrical conductivity for SEM of biological specimens is achieved through the use of ligand mediated wet osmiuum impregnation of the specimen before critical point (CP) drying. A commonly used ligand is thiocarbohvdrazide (TCH), first introduced to TEM for en block staining of lipids and glvcomacromolecules with osmium black. Now TCH is also used for SEM. However, after ligand mediated osinification nonspecific osmium black precipitates were often found obscuring surface details with large diffuse aggregates or with dense particular deposits, 2-20 nm in size. Thus, only low magnification work was considered possible after TCH appl ication.

Download Full-text

SEM and Auger microanalysis studies of Cu-Be dynode surfaces at each activation condition

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100109768 ◽

1978 ◽

Vol 36 (1) ◽

pp. 524-525

Author(s):

T. Koshikawa ◽

Y. Fujii ◽

E. Sugata ◽

F. Kanematsu

Keyword(s):

Electron Emission ◽

Secondary Electron ◽

Secondary Electron Emission ◽

Life Time ◽

Activation Process ◽

Beam Diameter ◽

Activation Temperature ◽

Electron Multiplier ◽

Activation Condition ◽

Activation Conditions

The Cu-Be alloys are widely used as the electron multiplier dynodes after the adequate activation process. But the structures and compositions of the elements on the activated surfaces were not studied clearly. The Cu-Be alloys are heated in the oxygen atmosphere in the usual activation techniques. The activation conditions, e.g. temperature and O2 pressure, affect strongly the secondary electron yield and life time of dynodes.In the present paper, the activated Cu-Be dynode surfaces at each condition are investigated with Scanning Auger Microanalyzer (SAM) (primary beam diameter: 3μmϕ) and SEM. The commercial Cu-Be(2%) alloys were polished with Cr2O3 powder, rinsed in the distilled water and set in the vacuum furnance.Two typical activation condition, i.e. activation temperature 730°C and 810°C in 5x10-3 Torr O2 pressure were chosen since the formation mechanism of the BeO film on the Cu-Be alloys was guessed to be very different at each temperature from the results of the secondary electron emission measurements.

Download Full-text

SEM analysis of DC magnetron sputtered beryllium films

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100106867 ◽

1988 ◽

Vol 46 ◽

pp. 960-961

Author(s):

E. F. Lindsey ◽

C. W. Price ◽

E. L. Pierce ◽

E. J. Hsieh

Keyword(s):

Fine Structure ◽

Electron Emission ◽

Secondary Electron ◽

Low Voltage ◽

Ion Beam ◽

Secondary Electron Emission ◽

Sem Analysis ◽

Fused Silica ◽

Grain Structure ◽

Silica Substrate

Columnar structures produced by DC magnetron sputtering can be altered by using RF biased sputtering or by exposing the film to nitrogen pulses during sputtering, and these techniques are being evaluated to refine the grain structure in sputtered beryllium films deposited on fused silica substrates. Beryllium is brittle, and fractures in sputtered beryllium films tend to be intergranular; therefore, a convenient technique to analyze grain structure in these films is to fracture the coated specimens and examine them in an SEM. However, fine structure in sputtered deposits is difficult to image in an SEM, and both the low density and the low secondary electron emission coefficient of beryllium seriously compound this problem. Secondary electron emission can be improved by coating beryllium with Au or Au-Pd, and coating also was required to overcome severe charging of the fused silica substrate even at low voltage. The coating structure can obliterate much of the fine structure in beryllium films, but reasonable results were obtained by using the high-resolution capability of an Hitachi S-800 SEM and either ion-beam coating with Au-Pd or carbon coating by thermal evaporation.

Download Full-text