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Electron emission observations from asgrown and vacuumcoated chemical vapor deposited diamondStable secondary electron emission from chemical vapor deposited diamond films coated with alkalihalides

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Direct dependence of secondary electron emission (SEE) from diamond films due to surface hydrogen has been observed. High secondary yields (14–27) have been achieved in polycrystalline diamond films on molybdenum substrates by varying the hydrogen content on the surface. This was accomplished by driving hydrogen from the bulk by heating the sample, or by adsorption of hydrogen onto the surface from direct hydrogen exposure. However, exposure to an electron beam depleted the surface of hydrogen as a function of current dosage in the energy range 300 eV‐3 keV, thereby reducing the secondary yield to a value as low as 3. Recovery of the secondary yield in the as‐deposited samples was facilitated by saturating the surface with hydrogen, as mentioned, and the recovery time has been characterized. The partial pressure of hydrogen could be adjusted so that the high secondary yield remained stable during beam exposure. The unique properties of these diamond films make them potentially useful as secondary emitters in electronic component designs. A special sample‐holder assembly has been constructed to test the feasibility of using these polycrystalline diamond films as dynodes in an electron amplifier. Actual gain at a hydrogen partial pressure of 1.0 × 10−T Torr was measured to be 2.4 × 104. The maximum gain expected was 2.4 × 105.

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