Synthesis of metal―semiconductor heterojunctions inside carbon nanotubes

• Published in: Journal of materials chemistry 2009-01, Vol.19 (25), p.4414-4420
• Main Authors: GAUTAM, Ujjal K, BANDO, Yoshio, BOURGEOIS, Laure, XIAOSHENG FANG, COSTA, Pedro M. F. J, JINHUA ZHAN, GOLBERG, Dmitri
• Format: Article
• Language: English
• Subjects: Applied sciences; Cross-disciplinary physics: materials science; rheology; Electronics; Exact sciences and technology; Materials science; Methods of crystal growth; physics of crystal growth; Molecular electronics, nanoelectronics; Nanoscale materials and structures: fabrication and characterization; Other topics in nanoscale materials and structures; Physics; Quantum wires; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; Theory and models of crystal growth; physics of crystal growth, crystal morphology and orientation
• ISSN: 0959-9428; 1364-5501
• DOI: 10.1039/b903791h

Heterojunctions between a metal and a semiconductor are at the core of all modern electronic devices. Recently, fabrication of such structures at the nanoscale has emerged as a hot topic due to their immense potential for the next generation of nanoscale devices and electronics. Here we report a high-temperature route for the synthesis of metal (In)-semiconductor (ZnS) nano-heterojunctions inside a carbon nanotube (CNT). As In is a superconductor at low temperatures, these 'nanocables' are also potential superconductor-semiconductor heterojunctions, synthesized for the first time inside a CNT. A noteworthy feature is that the majority of the heterostructure surface area is involved in forming interfaces such as In-ZnS, In-CNT, and ZnS-CNT. Mastering hese structural relations is critical to controlling its overall properties. Several interesting facts emerged from detailed structural characterization of the heterojunctions with high-resolution transmission electron microscopy. The growth direction of the wurtzite-type ZnS encapsulated segments is along [1010], while [0001] is the commonly preferred growth direction in free-standing ZnS nanowires. Following the observation of smooth In-ZnS interfaces, the orientation relationship of these two segments was analysed. Another interesting finding is the presence of a few layers of cubic ZnS near its interface with the CNT. This peculiarity is suggested to be a key contributor to the unusual encapsulated nanowire growth axis. These complex In/ZnS/CNT materials should provide opportunities for fundamental studies of heterojunctions at the nanoscale, as well as providing the basis for the development of chemical and radiation-shielded electronic nanodevices.