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[20a-B303-2] Characteristics of nc-Si ballistic electron emitter with a monolayer graphene surface electrode -Enhanced emission efficiency and output electron energy regularity-
Keywords:nanocrystalline silicon, ballistic electron, graphene
It is demonstrated that both the efficiency and the output electron energy dispersion of the ballistic hot electron emission from nanocrystalline silicon (nc-Si) diode can be drastically improved by using a monolayer-graphene film as the surface electrode.
The nc-Si diode is composed of a monolayer graphene surface electrode, an nc-Si layer, and a single-crystalline Si substrate. Monolayer graphene, prepared by a conventional CVD process, was transferred onto the nc-Si layer. Under a positive bias voltage, ballistic hot electrons generated in the nc-Si layer via multiple-tunneling cascade through quantum-sized nc-Si dots interconnected with tunnel oxides are emitted outside through monolayer graphene electrode. The characteristics were measured in terms of the emission efficiency and the output electron energy distribution.
The experimental results are summarized as follows: (1) the electron emission efficiency at room temperature is increased up to 6.3% that is considerably higher than that in the case of conventional thin metal films. (2) The peak energy of emitted electrons can be tuned by the applied voltage while keeping a relatively low energy dispersion. (3) At low temperatures of around 150 K, the energy distribution becomes more monochromatic, and then the peak energy is close to the energy value corresponding to the complete ballistic electron emission.
These results can be interpreted as a result of combined effects of muliple-tunneling transport in the nc-Si layer and high transparency of monolayer graphene for ballistic hot electrons.
The nc-Si diode is composed of a monolayer graphene surface electrode, an nc-Si layer, and a single-crystalline Si substrate. Monolayer graphene, prepared by a conventional CVD process, was transferred onto the nc-Si layer. Under a positive bias voltage, ballistic hot electrons generated in the nc-Si layer via multiple-tunneling cascade through quantum-sized nc-Si dots interconnected with tunnel oxides are emitted outside through monolayer graphene electrode. The characteristics were measured in terms of the emission efficiency and the output electron energy distribution.
The experimental results are summarized as follows: (1) the electron emission efficiency at room temperature is increased up to 6.3% that is considerably higher than that in the case of conventional thin metal films. (2) The peak energy of emitted electrons can be tuned by the applied voltage while keeping a relatively low energy dispersion. (3) At low temperatures of around 150 K, the energy distribution becomes more monochromatic, and then the peak energy is close to the energy value corresponding to the complete ballistic electron emission.
These results can be interpreted as a result of combined effects of muliple-tunneling transport in the nc-Si layer and high transparency of monolayer graphene for ballistic hot electrons.