Ambipolar field effect in Sb-doped Bi2Se3 nanoplates by solvothermal ...
Supporting Information
Ambipolar field effect in Sb-doped Bi2Se3 nanoplates by solvothermal synthesis †
†
Desheng Kong,1, Kristie J. Koski,1, Judy J. Cha,1 Seung Sae Hong,2 and Yi Cui1,3* 1
Department of Materials Science & Engineering, Stanford University, Stanford, California 94305, USA
2
Department of Applied Physics, Stanford University, Stanford, California 94305, USA
3
Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, CA 94025, USA
Figure S1. TEM characterization of pure Bi2Se3 nanoplates. High-resolution TEM image resolves crystalline lattice fringes. Top right inset: low-magnification TEM image of the corresponding nanoplate. Bottom left inset: Selected area electron diffraction yields sharp diffraction spots that further confirm the crystalline nature of the nanoplate.
Figure S2. Optical image of few-layer Bi2Se3 nanoribbons grown by the vapor-liquid-solid method with varying thicknesses. We use Ar/metal plasma etching on vapor-phase synthesized Bi2Se3 nanoribbons to prepare these surfactant-free, ultrathin nanoribbons24. The thicknesses of the terraces are determined by AFM measurements, and the corresponding number of quintuple layers is marked with the black numbers. The optical contrast provides a facile gauge of sample thickness. Notice that Ar/metal plasma also gently etches SiO2/Si substrate, which may increase the apparent thickness up to ~1nm with a few minutes of etching.
Figure S3. Thickness of two typical nanoplates measured by atomic force microscopy (AFM). Optical microscopy images (top row) of Hall bar devices patterned on solvothermally synthesized Bi2Se3 nanoplates. AFM height profiles corresponding to the dashed line in the optical images are shown in the bottom row. The optical contrast of these two nanoplates suggests the thickness of ~8 nm, according the previous calibration. Due to the presence of PVP surfactant, the apparent AFM height profiles may deviate from the actual sample thickness, as shown in (B). Our measurements suggest the thickness of the PVP layer is in the range of a few angstroms to ~3nm.
Figure S4. Nanoplate thicknesses determined by AFM height profiles and optical contrast. The AFM thickness is consistently thicker than optical thickness by a few angstrom to ~ 6 nm.
Figure S5. The volume carrier density, n3D, vesus the nanoplate thickness, t. The green trace is the empirical relation of n3D versus t by Kim et al.44 Notice that the volume carrier density is simply defined as n3D = n2D / t. It is not the actual bulk carrier density in these nanoplates.
Ambipolar field effect in Sb-doped Bi2Se3 nanoplates by solvothermal synthesis †
†
Desheng Kong,1, Kristie J. Koski,1, Judy J. Cha,1 Seung Sae Hong,2 and Yi Cui1,3* 1
Department of Materials Science & Engineering, Stanford University, Stanford, California 94305, USA
2
Department of Applied Physics, Stanford University, Stanford, California 94305, USA
3
Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, CA 94025, USA
Figure S1. TEM characterization of pure Bi2Se3 nanoplates. High-resolution TEM image resolves crystalline lattice fringes. Top right inset: low-magnification TEM image of the corresponding nanoplate. Bottom left inset: Selected area electron diffraction yields sharp diffraction spots that further confirm the crystalline nature of the nanoplate.
Figure S2. Optical image of few-layer Bi2Se3 nanoribbons grown by the vapor-liquid-solid method with varying thicknesses. We use Ar/metal plasma etching on vapor-phase synthesized Bi2Se3 nanoribbons to prepare these surfactant-free, ultrathin nanoribbons24. The thicknesses of the terraces are determined by AFM measurements, and the corresponding number of quintuple layers is marked with the black numbers. The optical contrast provides a facile gauge of sample thickness. Notice that Ar/metal plasma also gently etches SiO2/Si substrate, which may increase the apparent thickness up to ~1nm with a few minutes of etching.
Figure S3. Thickness of two typical nanoplates measured by atomic force microscopy (AFM). Optical microscopy images (top row) of Hall bar devices patterned on solvothermally synthesized Bi2Se3 nanoplates. AFM height profiles corresponding to the dashed line in the optical images are shown in the bottom row. The optical contrast of these two nanoplates suggests the thickness of ~8 nm, according the previous calibration. Due to the presence of PVP surfactant, the apparent AFM height profiles may deviate from the actual sample thickness, as shown in (B). Our measurements suggest the thickness of the PVP layer is in the range of a few angstroms to ~3nm.
Figure S4. Nanoplate thicknesses determined by AFM height profiles and optical contrast. The AFM thickness is consistently thicker than optical thickness by a few angstrom to ~ 6 nm.
Figure S5. The volume carrier density, n3D, vesus the nanoplate thickness, t. The green trace is the empirical relation of n3D versus t by Kim et al.44 Notice that the volume carrier density is simply defined as n3D = n2D / t. It is not the actual bulk carrier density in these nanoplates.
