Nonuniform nanowire doping profiles revealed by quantitative scanning photocurrent microscopy

The quantitative scanning photocurrent microscopy have revealed the nonuniform nanowire doping profiles by using Kelvin probe force microscopy (KPFM) as a technique to determine surface potentials with high spatial resolution. The surface doping during growth should produce an axially varying doping density and by extension an axially varying carrier concentration, where the study has investigated transport characteristics of nanowires. The SPCM measurements were performed using a confocal microscope to focus illumination onto a sample mounted on a piezoelectric scanning stage. The surface doping of VLS grown nanowires can occur even in the absence of measurable taper, where PLAP analysis of P-doped Si nanowires indicates an increase in P concentration at the surface and SPCM analysis reveals a sensitivity gradient along the wire length. The study resulted that the nanowire device implies that SPCM can be used in devices based on other materials.