ULTRAFAST TIME RESOLUTION IN SCANNED PROBE MICROSCOPIES

The speed limitations conventionally encountered in scanning tunneling microscopy, scanning capacitance microscopy, and atomic force microscopy result from the external electronics and are not inherent to the techniques themselves. Ultrafast time resolution faster than the bandwidth of the measuring electronics can be achieved by combining these techniques with picosecond optical excitation and utilizing inherent nonlinearities in the physical system. We demonstrate this idea by directly measuring carrier relaxation times at the Si(111)-(7×7) surface on the nanosecond time scale via scanning capacitance microscopy measurements of the surface photovoltage.