Investigation of the growth and in situ heating transmission electron microscopy analysis of Ag2S-catalyzed ZnS nanowires

Publication date: 1 April 2018
Source:Applied Surface Science, Volume 436
Author(s): Jung Han Kim, Jong Gu Kim, Junghyun Song, Tae-Sung Bae, Kyou-Hyun Kim, Young-Seak Lee, Yoonsoo Pang, Kyu Hwan Oh, Hee-Suk Chung
We investigated the semiconductor-catalyzed formation of semiconductor nanowires (NWs) – silver sulfide (Ag2S)-catalyzed zinc sulfide (ZnS) NWs – based on a vapor-liquid-solid (VLS) growth mechanism through metal-organic chemical vapor deposition (MOCVD) with a Ag thin film. The Ag2S-catalyzed ZnS NWs were confirmed to have a wurtzite structure with a width and length in the range of ∼30 nm to ∼80 nm and ∼1 μm, respectively. Using extensive transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDS) analyses from plane and cross-sectional viewpoints, the ZnS NWs were determined to have a c-axis, [0001] growth direction. In addition, the catalyst at the top of the ZnS NWs was determined to consist of a Ag2S phase. To support the Ag2S-catalyzed growth of the ZnS NWs by a VLS reaction, an in situ heating TEM experiment was conducted from room temperature to 840 °C. During the experiment, the melting of the Ag2S catalyst in the direction of the ZnS NWs was first observed at approximately 480 °C along with the formation of a carbon (C) shell. Subsequently, the Ag2S catalyst melted completely into the ZnS NWs at approximately 825 °C. As the temperature further increased, the Ag2S and ZnS NWs continuously melted and vaporized up to 840 °C, leaving only the C shell behind. Finally, a possible growth mechanism was proposed based on the structural and chemical investigations.

Graphical abstract

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