Step-flow growth of Bi2Te3 nanobelts

Understanding the growth mechanism of nanostructures is key to tailoring their properties. Many compounds form nanowires following the vapor-liquid-solid (VLS) growth mechanism, and the growth of Bi2Te3 nanobelts was also explained following the VLS route. Here, we present another growth mechanism of Bi2Te3 nano- and sub-micron belts and ribbons. The samples were grown by physical vapor transport from Bi2Te3 precursor using TiO2 nanoparticles as catalyst, and analyzed by scanning electron microscopy and scanning transmission electron microscopy. The growth starts from a Te-rich cluster, and proceeds via a thin, tip-catalyzed primary layer growing in the [110] direction. The primary layer serves as a support for subsequent step-flow growth. The precursor predominantly absorbs on the substrate and reaches the belt by migration from the base to the tip. Terrace edges pose energy barriers that enhance the growth rate of secondary layers compared to the primary layer. Broadening of the sidewalls is commonly observed and leads to triangular voids that can even result in a branching of the growing belts. Step-flow growth of Bi2Te3 sub-micron belts is different from the spiral-like growth mode of Bi2Te3 thin films, and an important step towards the growth of layered topological insulator nanostructures