Colloidal Synthesis and Electrical Properties of GeSe Nanobelts

GeSe is a narrow band gap IV-VI semiconductor that has been attracting increasing attention as a potential alternative material for photovoltaics, along with other optical and electrical applications. However, unlike several other narrow band gap chalcogenide semiconductors, very few examples of GeSe nanostructures have been reported. One-dimensional nanostructures are particularly attractive, because they can serve as building blocks for nanostructured electronic devices. As a step toward both increasing the morphological diversity of GeSe nanomaterials and expanding the library of electronic materials that are accessible as one-dimensional nanostructures, we report here the colloidal synthesis and electrical properties of GeSe nanobelts. The GeSe nanobelts were synthesized by first heating a one-pot reaction mixture of GeI4, TOP-Se, oleylamine, oleic acid, and hexamethyldisilazane to 320 degrees C, then adding additional TOP-Se and heating for several additional hours. Aliquot studies revealed that an amorphous GeSex precursor forms first, and then dissolves with continued heating prior to rapid nucleation of the GeSe nanobelts. The resulting nanobelts, which were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), atomic force microscopy (AFM), selected area electron diffraction (SAED), energy dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD), had an average diameter of 77 +/- 18 nm and lengths that ranged from 1-25 mu m. Visible-NIR diffuse reflectance spectroscopy revealed an absorption edge near 1100 nm and an indirect band gap of approximately 1.1 eV. Individual GeSe nanobelts were aligned between Ti/Au electrodes using an electric field-assisted assembly process, and 2- and 4-point current voltage measurements were conducted, indicating ohmic (linear) behavior with resistivity values of approximately 360 Omega-cm.