Control of 3-dimensional atomic arrangement by AFM and ALE, and preparation of artificial inorganic materials

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Using AFM with a conductive cantilever, we attempt to control the adsorption and desorption of oxygen on TiO2 surface. In an area of 1000 x 1000 nm, stripe patterns with a height of 5 nm were formed after a cantilever was scanned at bias voltage of -3.0V in O2 atmosphere. The spatial resolution of the stripe patterns was not satisfactory, e.g., the line width of 50 nm. The broadening of the lines can be mainly ascribed to the drift of a x-y scanner of the AFM apparatus. Thus, we tried to draw letters of "SY" and "KK" in a narrow scan area of 20 x 20 nm. In AFM topographies, the letters with height of 5 nm and line-width of 5 nm were drawn on the TiO2 surface. The letters of "SY" and "KK" were also confirmed from conductive maps. The patterns were maintained in either O2 or Ar atmosphere, and even under uv illumination. It should be noted that a part of the patterns was removed by applying a positive voltage of 10V under uv illumination. This result is consistent with the theoretical pr … More ediction that oxygen molecules adsorbed on the TiO2 surface are removed when holes are effectively generated in the valence band of TiO2 under the depletion condition. >From these results, we can control the spatial arrangement of adsorbed molecules at a nanoscale resolution.The deposition of metal is important for the fabrication of nanoscale electronic devices. The metal deposition has been attempted by electrochemical deposition of metal by STM or AFM. However, nanoscale patterning of metal electrodes was not realized by electrochemical systems because of the presence of the electrolytic solution. In the present work, the deposition of Cu electrode was performed by employing the cantilever coated with CuI which was solid electrolyte of Cu ions. The Cu electrode with line-width of 50 nm was formed on the TiO2 surface by applying a negative voltage of -10V. The deposited Cu electrode was removed by applying a positive voltage of 10V. We can establish a fundamental technique of the fabrication of nanoscale electrodes. Less