| Budget Amount *help |
¥2,200,000 (Direct Cost: ¥2,200,000)
Fiscal Year 1994: ¥1,000,000 (Direct Cost: ¥1,000,000)
Fiscal Year 1993: ¥1,200,000 (Direct Cost: ¥1,200,000)
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| Research Abstract |
MgO films of 200 nm thick were prepared by magnetron sputtering of MgO target in an Aratmosphere of about 2 Pa.X-ray excited photoelectron emission spectrum (XPS) of the films was measured with ESCA PHI 1600 by an excitation of x-rays of 1253.6 eV.It was found that the MgO film yielded exoelectrons, whose energy was higher than that of the incident photons, when it was subjected to the ion bombardment.
The MgO film was set in an XPS apparatus, and the surface was cleaned by the bombardment of 3 keV Ar ions at a rate of 15 mA/cm^2 for about 20 seconds until the contamination was completely removed, followed by an annealing at room temperature for 48 hours under the vacuum of 10^<-8> Pa.
Exoelectrons could be observed in the following procedure : First, Ar ions of 3 keV were irradiated on the sample surface at a rate of 15 mA/cm^2. Then the x-ray photons were irradiated to the surface and the photon excited electrons of the energy range from 1154 to 1554 eV were measured repeatedly at a rate of 15 seconds per a scan. As soon as the irradiation started, exoelectrons of uniform energy spectrum appeared but the intensity decreases monotonically with time. Any exoelectrons were not observed beyond 100 seconds, but they appeared again after quiescence (about 10 minutes) of the photon irradiation. This phenomenon of appearance, decay and recovery was observed for a few repetition of the irradiation and quiescence after the ion beam irradiation. When we increased the ion irradiation period from 30 seconds to 2 minutes, the intensity of exoelectrons increased. It is considered that atoms on the ion-bombarded film surface, which are get fixed at quasi-stable sites, are activated to relax to more stable positions with an irradiation of high energy photons. It has not been understood clearly, however, that the energy of some exoelectrons is too high and that all samples did not necessarily show the exoelectron emission characteristics.
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