Lateral epitaxial heterojunctions in single nanowires fabricated by masked cation exchange

Recently in our group it has been demonstrated that the cation exchange reaction can be exploited for fabrication of luminescent patterns and electrical circuits in chalcogenide NC films [1]. This approach, called masked... [ view full abstract ]

Recently in our group it has been demonstrated that the cation exchange reaction can be exploited for fabrication of luminescent patterns and electrical circuits in chalcogenide NC films [1]. This approach, called masked cation exchange, combines the direct electron-beam exposure and the cation exchange reaction  to create functional micro patterns. In this work we apply the masked cation exchange to fabricate heterojunction CdSe/Cu2Se nanowires using the cation exchange reaction from CdSe to Cu2Se. The formation of the heterojunction within a single nanowire is confirmed via high resolution  TEM and energy-dispersive x-ray images (Fig.1). Interestingly, the CdSe and Cu2Seregions exhibit epitaxial relationships at the interface (Fig.1)..Our experiments, supported by computational modeling, indicate that the cation exchange at the CdSe/Cu2Se interface is only possible if the displaced Cd2+ ions can radially out-diffuse to the solution phase.For the irradiated section of the wire, this exit pathway is blocked and, therefore, the cation exchange cannot occur.Further electrical measurements are performed that probe the conductivity in such heterojunction CdSe/Cu2Se nanowires.