NANOSCALE STM-PATTERNING AND CHEMICAL MODIFICATION OF THE SI(100) SURFACE

Nanoscale patterning of the Si(100)-2x1:H monohydride surface has been achieved using an ultrahigh vacuum (UHV) scanning tunneling microscope (STM). The monohydride surface, prepared in UHV by exposure of a heated sample (650 K) to an atomic hydrogen flux, serves as an effective resist for STM patterning and exposure to O2 and NH3. Operating the STM in field emission causes hydrogen to be desorbed from the surface, exposing atomically clean silicon. There is no evidence for repassivation of the surface after patterning, suggesting that hydrogen may desorb as H-2. Hydrogen desorption can also be achieved at tunneling biases (approximately 3-4 V) by using larger currents. Nanometer-scale linewidths can be achieved with this technique; single dimer rows have in fact been depassivated. The patterned areas display the same chemical reactivity as clean Si, suggesting the possibility of selective chemical modification of the surface at nanometer scales. This STM-depassivation technique shows considerable potential as a means for nanostructure fabrication.