2016年7月27日星期三

Simple synthesis of ultra-high quality In2S3 thin films on InAs substrates

Highlights

Extremely high-quality tetragonal β-In2S3 thin films firmly remained on the InAs substrate for the first time.
New growth technique for high quality In2S3 crystals by adopting simple thermal sulfurization of InAs substrates.
In2S3 crystals are of remarkable crystal quality.

Abstract

We report a simple and reliable technique to synthesize high-quality In2S3 films on InAs substrates by using thermal sulfurization in a hot-wall tube furnace. X-ray diffraction and energy dispersive X-ray spectroscopy data confirmed that the synthesized films were cubic β-In2S3 or tetragonal β-In2S3, depending on growth conditions. Field emission scanning electron microscopy analysis and Raman spectroscopy showed that the In2S3 films are of remarkable crystal quality. Especially, by optimizing the growth conditions, we have grown an extremely high-quality tetragonal β-In2S3 thin film firmly remained on the InAs substrate, for the first time.

Keywords

  • Indium-sulfide
  • Thin films
  • X-ray diffraction (XRD)
  • Scanning electron microscopy (SEM);
  • Raman spectroscopy

2016年7月26日星期二

Structure, interface abruptness and strain relaxation in self-assisted grown InAs/GaAs nanowires

Highlights

We study 2 critical issues (interface abruptness and strain release) in InAs/GaAs NWs.
Structural and chemical interface sharpness ≤1.5 nm, better than in previous reports.
Simultaneous elastic and plastic relaxation is shown that agrees with FEM simulations.
Structural, chemical and strain release investigations were performed by STEM.
New MBE self-seeded method whereby InAs is grown by splitting In and As depositions.

Abstract

The structure, interface abruptness and strain relaxation in InAs/GaAs nanowires grown by molecular beam epitaxy in the Ga self-catalysed mode on (111) Si have been investigated by transmission electron microscopy. The nanowires had the zincblende phase. The InAs/GaAs interface was atomically and chemically sharp with a width around 1.5 nm, i.e. significantly smaller than previously reported values. This was achieved by the consumption of the Ga droplet and formation of a flat top facet of the GaAs followed by the growth of InAs by splitting the depositions of In and As. Both elastic and plastic strain relaxation took place simultaneously. Experimental TEM results about strain relaxation very well agree with linear elasticity theory calculations by the finite element methods.

Graphical abstract

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Keywords