Yongmin Kim

Optical and magnetic properties of Mn+-implanted GaAs

Neutron-transmutation-doped GaAs samples were prepared by irradiating the middle-level neutrons into the semi-insulating GaAs grown by a liquid encapsulated Czochralski method and subsequently implanted with Mn+. The characteristics of the Mn+-implanted neutron-transmutation-doped GaAs (namely, the implantation of Mn+ subsequent to neutron-transmutation-doping) were investigated by various measurements. The result of the energy dispersive x-ray peak displayed an injected Mn concentration of 9.65%. The photoluminescence peaks related to carbon and germanium acceptors were resolved, and the peaks related to Mn due to a neutral Mn acceptor were evidently observed. It is found that the proper activation for the neutral Mn acceptor starts from a relatively low annealing temperature of 600°C for 15min. The atomic force microscopy and magnetic forcemicroscopy images showed that magnetic clusters were well formed. The ferromagnetic hysteresis loop measured at 10K was observed, and the temperature-dependent magnet...

Degradation Mechanism Of Electron Emission Characteristics In Silicon Field Emitters

Abstiract Degradation of electron emission characteristics in silicon field emitters and i ts mechanism have been studied. The silicon field emitters with a triode type were fabricated by using a chemical-mechanical-polishing process. There exists a critical biasing time, t,, at which the anode current starts to be degraded predominantly. The t, i s shortened as the anode current increases. Also, the emission current repeatedly measured within t, with a complete relaxation after each measurement would not be degraded even though the total biasing time exceeded the critical time. The expeirimental results indicate that the degradation in silicon field emitters mainly originates from thermal instability of the Si tip due to Nottingham heating.