Atomic force microscopy nanomanipulation of silicon nanocrystals for nanodevicefabrication

Abstract

An atomic force microscopy (AFM) tip has been used to manipulate silicon nanocrystalsdeposited by low-pressure chemical vapour deposition on thermally oxidized p-type Siwafer. Three nanomanipulation methods are presented. The first one catches ananocrystal with the AFM tip and deposits it elsewhere: the tip is used as anelectrostatic ‘nano-crane’. The second one simultaneously manipulates a set ofnanocrystals in order to draw well-defined unidimensional lines: the tip is used as a‘nano-broom’. The third one manipulates individual nanocrystals with a precisionof about 10 nm using both oscillating and contact AFM modes. Switching fromstrong interaction forces (chemical) to weak ones (van der Waals, electrostatic orcapillarity) is the basis of these manipulation methods. We have applied the secondmethod to connect two electrodes drawn by e-beam and lift-off with a 70 nmlong silicon nanocrystal chain. Current versus voltage characterization of thenanofabricated device shows that the increase in nanocrystal density gives rise toconduction between the connected electrodes. Resonant tunnelling effects resulting fromSi nanocrystal (nc-Si) multiple tunnel junctions have been observed at 300 K.We also show that offset charges directly influence the position of the resonanttunnelling peaks. Finally, the possibility of manipulating nc-Si with a diameter ofaround 5 nm is shown to be a promising way to fabricate single electron devicesoperating at room temperature and fully compatible with silicon technology.