10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
Abstract View
Gas-phase Synthesis of Gallium Arsenide Quantum Dots through Hydrogen-assisted Spark Discharge and Its Application
KIWOONG LEE, Dongjoon Lee, Mansoo Choi, Seoul National University, Seoul, Korea
Abstract Number: 631 Working Group: Materials Synthesis
Abstract Gallium Arsenide (GaAs) has been considered as one of the most prominent III-V semiconductors because of its extraordinary electronic and photonic properties, such as high electron mobility and direct band gap. Furthermore, because of its large Bohr radius and strong quantum confinement effect, there have been intense effort to synthesize GaAs nanocrystals (NCs) with diameter of under 20 nm. However, despite these advantages of GaAs NCs, there has been inherent difficulties of synthesizing GaAs NCs restricting its applications toward practical devices as well as overall exploration.
Recently, our group introduced hydrogen gas toward spark discharge between silicon (Si) electrodes and demonstrated that hydrogen gas enabled silicon (Si) nanocrystals to be highly pure and crystalline. (D. Lee et al, 2016) In this research, crystallization of Si nanoparticles was based on the scheme in which amorphous Si matrix become crystalline by hydrogen atom’s insertion into and relaxation from Si bonds. (S. Srirman, 2002) However, unlike Si, GaAs NCs are hardly obtained by hydrogen-assisted spark discharge since spark discharge energy is not sufficient for the relaxation of hydrogen atoms from GaAs matrix. We identify the amorphous GaAs nanoparticles embedding hydrogen atoms in GaAs matrix via transmission electron microscopy (TEM) and Fourier transform infrared spectroscopy (FTIR). In order to extract these embedded hydrogen atoms and thus to crystallize GaAs nanoparticles, we add heating procedure. After generation of hydrogen-inserted GaAs nanoparticles via hydrogen-assisted spark discharge, these amorphous GaAs aerosols pass through tube furnace with temperature of 950ºC for the desorption of inserted hydrogen atoms. It is demonstrated that fabricated GaAs NCs exhibit high crystallinity through TEM and X-ray diffraction (XRD) measurements.
Additionally, we demonstrate that these GaAs NCs exhibit quantum confinement effects from photoluminescence measurement. We generate GaAs NCs with various size by varying the capacitance of spark discharge circuit from 0.5nF to 6nF, and observe that these GaAs NCs exhibit different photoluminescence peaks according to its size.
Even though there are several other methods of fabricating GaAs quantum dots (QDs) such as chemical synthesis, chemical vapor deposition (CVD), and molecular beam epitaxy (MBE), these methods possess inherent drawbacks, such as expensive installation, undesirable by-products, toxic materials and poor controllability. Since our aerosol-based technique is free from these obstacles, we look forward to our GaAs QDs to be utilized in various applications, such as solar cell, LED, and transistor. In addition, our fabricating GaAs QDs technique is expected to provide an additional degree of freedom in synthesizing various semiconductor quantum dots with high crystallinity.
This work was supported by Global Frontier R&D Program on Center for Multiscale Energy System by National Research Foundation (NRF) under the Ministry of Science, ICT and Future Planning, Korea (Grant no.2012M3A6A7054855).
1. Lee, D., Lee, K., Kim, D.S., Lee, J-.K., Park, S.J., and Choi, M. (2016) Journal of Aerosol Science114, 139-145. 2. Sriraman, S., Agarwal, S., Aydil, E.S., and Maroudas, M. (2002) Nature418, 62-65.