Ultra-long bismuth telluride nanoribbons synthesis by lithographically patterned galvanic displacement

Abstract

We demonstrated the wafer level batch synthesis and fabrication of single semiconducting thermoelectric nanoribbon based devices by Lithographically Patterned Galvanic Displacement (LPGD). The shape, composition, and dimension of nanoribbons were tailored by adjusting deposition conditions. High resolution TEM images with fast Fourier transform (FFT)-converted selected area electron diffraction (SAED) patterns confirmed the formation of polycrystalline Bi2Te3 intermetallic compound with a rhombohedral structure without elemental Te and Bi. The thickness dependent electrical resistivity of BixTey nanoribbons shows a classic size effect due to the increase in surface boundary scattering. The as-synthesized nanoribbons were n-type semiconductors with no clear trend between field effect carrier mobility and composition, which might be attributed to the trapped charges at the interface between the channel and dielectric layer. The preliminary results on thermoelectric properties (i.e. Seebeck coefficient and power factor) show that the Seebeck coefficient of as-synthesized 0.1 mu m thick Bi30Te70 nanoribbon is comparable with bulk counterparts, however, the power factor was lower because of poor crystallinity which leads to higher resistivity.