Large Anisotropy of Electrical Properties in Layer-Structured In₂Se₃ Nanowires

Abstract

Layer-structured indium selenide (In 2Se 3) nanowires (NWs) have large anisotropy in both shape and bonding. In 2Se 3 NWs show two types of growth directions: [11-20] along the layers and [0001] perpendicular to the layers. We have developed a powerful technique combining high-resolution transmission electron microscopy (HRTEM) investigation with single NW electrical transport measurement, which allows us to correlate directly the electrical properties and structure of the same individual NWs. The NW devices were made directly on a 50 nm thick SiN x membrane TEM window for electrical measurements and HRTEM study. NWs with the [11-20] growth direction exhibit metallic behavior while the NWs grown along the [0001] direction show n-type semiconductive behavior. Excitingly, the conductivity anisotropy reaches 10 (3)-10 (6) at room temperature, which is 1-3 orders magnitude higher than the bulk ratio.

Topological Insulator Nanowires and Nanoribbons

“…As a result, nanoribbons have a rectangular cross section. TEM studies on a wide nanoribbon ( Figure 2B) reveal similar crystalline characteristics to the narrow nanoribbon ( Figure 2A); it grows along [11][12][13][14][15][16][17][18][19][20] direction as well. The TEM data of a nanowire with rough surface are shown in Figure 2C.…”

“…Nanowires, which exhibit rough surfaces, are formed by stacking nanoplatelets along the axial direction of the wires. Nanoribbons are grown along [11][12][13][14][15][16][17][18][19][20] direction with a rectangular crosssection and have diverse morphologies, including quasi-one-dimensional, sheetlike, zigzag and sawtooth shapes. Scanning tunneling microscopy (STM) studies on nanoribbons show atomically smooth surfaces with 1 nm step edges, indicating single Se-Bi-Se-Bi-Se quintuple layers.…”

“…The corresponding selected-area electron diffraction (SAED) pattern (inset of Figure 2A) exhibits a clear hexagonally symmetric spots pattern, confirming the single crystalline nature. A high resolution TEM (HRTEM) image (inset in Figure 2A) shows hexagonal lattice fringes with a correct lattice spacing of 2.1 Å between (11)(12)(13)(14)(15)(16)(17)(18)(19)(20) planes. SAED patterns and HRTEM images demonstrate that the nanoribbons grow along [11][12][13][14][15][16][17][18][19][20] direction, with (0001) facets as top and bottom surfaces and (1-100) facets as side surfaces.…”

Thickness-Dependent Dielectric Constant of Few-Layer In2Se3 Nanoflakes

“…[8][9][10][11] By controlling the synthesis parameters or thermal/electrical pretreatment processes, several phases (superlattice, simple hexagonal -phase, simple hexagonal -phase, and amorphous state) with vastly different electrical conductivity can coexist at the ambient condition, [12][13][14] which explains the research interest of In2Se3 as a prototypical phasechange material. 7,[12][13][14][15][16][17][18] In addition, the lattice constant of In2Se3 matches well with Bi2Se3, which is heavily investigated for its high thermoelectric figure-of-merit and topological insulator nature. 19,20 The chemical and structural compatibility between the two chalcogenides enables the growth of In2Se3/Bi2Se3 heterostructures.…”

Nanoscale Electronic Inhomogeneity in In2Se3 Nanoribbons Revealed by Microwave Impedance Microscopy

“…It has been previously reported that pristine VLS-grown [11][12][13][14][15][16][17][18][19][20] In 2 Se 3 nanoribbons with superlattice structures (Fig. 3a, left) exhibit metallic behavior and room temperature R 2T as low as kilo-ohms 10 . Further studies show that after applying a low voltage (<1V) pulse, R 2T can increase up to mega-ohms and the ribbons behave semiconducting.…”