Direct Electron Beam Processing Of Semiconductor Nanostructures
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Direct Electron Beam Processing Of Semiconductor Nanostructures Yeonjoon Park, Rian Zhao, Petra Specht and Eicke R. Weber Department of Materials Science Engineering, U.C.Berkeley Berkeley, CA 94720, U.S.A. Abstract We used a high current density focused electron beam to modify a GaAs substrate. To avoid any oxidation or carbon contamination problem, an in-situ electron gun, combined with III-V molecular beam epitaxy (MBE) machine, was used. By changing the substrate temperature and the electron beam dwell time on each spot, different sizes of thermal irradiation marks were created. Fabricated spot-diameters in the sub-micrometer range suggest the possible utilization of this process for novel applications with the MBE growth technique. Introduction A local heating and defect generation by a finely focused electron beam is one of the very interesting and challenging topics regarding its capability for controlled nano-fabrication. For example, Y. Ito et al. used this process with AlF3 layer to make an electrondiffraction grating.1 G.S. Chen et al. used the electron beam irradiation to make conductive silicon nano-crystals from the parent SiO2.2 M. Libera observed the formation of Ge48Te52 nano-crystals with 10-100nm sizes in amorphous layers with focused electron beam heating.3 H.Y. Sheng et al. fabricated Ni-silicide by a localized chemical reaction with the direct electron beam patterning, and made a single electron transistor with the same method.4 More recently, T. Ishkawa et al. fabricated periodic nano-craters on GaAs, which can accommodate multiples of single InAs quantum dots by in-situ direct e-beam lithography with a very low pressure chlorine gas.5 Thermal modeling and a mild temperature experiment of the focused electron beam heating on the solid target were given by A.A. Iranmanesch and R.F.W. Pease for the case where the radius of the electron beam is greater than the Gruen range (rb>Rg).6 They also predicted an electron beam of 20kV, 16µA in 1.35µm radius can raise the local temperature of GaAs above 1238°C. However, the temperature rise in the ultimate resolution limit, where the radius of electron beam is much smaller than the Gruen range of GaAs (rb
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