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 microscop e (STM). The monohydride surface, prepared in UHV by exposure of a hea ted sample (650 K) to an atomic hydrogen flux, serves as an effective resist for STM patterning and exposure to O2 and NH3. Operating the ST M in field emission causes hydrogen to be desorbed from the surface, e xposing atomically clean silicon. There is no evidence for repassivati on of the surface after patterning, suggesting that hydrogen may desor b as H-2. Hydrogen desorption can also be achieved at tunneling biases (approximately 3-4 V) by using larger currents. Nanometer-scale linew idths can be achieved with this technique; single dimer rows have in f act been depassivated. The patterned areas display the same chemical r eactivity as clean Si, suggesting the possibility of selective chemica l modification of the surface at nanometer scales. This STM-depassivat ion technique shows considerable potential as a means for nanostructur e fabrication.