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Large area Germanium Tin nanometer optical film coatings on highly flexible aluminum substrates

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ABSTRACT

Germanium Tin (GeSn) films have drawn great interest for their visible and near-infrared optoelectronics properties. Here, we demonstrate large area Germanium Tin nanometer thin films grown on highly flexible aluminum foil substrates using low-temperature molecular beam epitaxy (MBE). Ultra-thin (10–180 nm) GeSn film-coated aluminum foils display a wide color spectra with an absorption wavelength ranging from 400–1800 nm due to its strong optical interference effect. The light absorption ratio for nanometer GeSn/Al foil heterostructures can be enhanced up to 85%. Moreover, the structure exhibits excellent mechanical flexibility and can be cut or bent into many shapes, which facilitates a wide range of flexible photonics. Micro-Raman studies reveal a large tensile strain change with GeSn thickness, which arises from lattice deformations. In particular, nano-sized Sn-enriched GeSn dots appeared in the GeSn coatings that had a thickness greater than 50 nm, which induced an additional light absorption depression around 13.89 μm wavelength. These findings are promising for practical flexible photovoltaic and photodetector applications ranging from the visible to near-infrared wavelengths.

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High resolution SEM images of GeSn thin film coating on Al foils (a) t = 20 nm (b) t = 50 nm (c) t = 100 nm (d) t = 180 nm.
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f4: High resolution SEM images of GeSn thin film coating on Al foils (a) t = 20 nm (b) t = 50 nm (c) t = 100 nm (d) t = 180 nm.

Mentions: To better understand the nanoscale structure of GeSn thin film coated Al foils, high-resolution SEM images were measured. Figure 4(a–d) show the SEM images of GeSn thin films grown on Al foil with t = 20, 50, 100 and 180 nm, respectively. The GeSn thin film coatings present a smooth surface even grown upon normal Al foil substrate that were largely untreated from their commercial state. However, it is clear that nano-sized islands gradually atop the GeSn coatings that are thicker than 50 nm, as shown in Fig. 4(b–d). The XRD results suggest there probably exists Sn-rich islands. Here, we indeed observe these nano islands from the SEM images. To identify the elemental makeup of these nano-sized islands, we performed elemental mapping of GeSn films with a thickness of 180 nm grown on Al foil. As shown in Fig. 5(b), the Al element distributes uniformly with several light areas (in circled dash lines). Comparing this with the Sn element mapping as illustrated in Fig. 5(d), the nano islands appear Sn-rich as GeSn blotches. The results indicate an epitaxial breakdown exists in MBE grown GeSn thin films on Al foil substrate for thicknesses greater than 50 nm, which changes the surface morphology from a 2D growth mode to a 3D growth mode with relatively larger nm islands.


Large area Germanium Tin nanometer optical film coatings on highly flexible aluminum substrates
High resolution SEM images of GeSn thin film coating on Al foils (a) t = 20 nm (b) t = 50 nm (c) t = 100 nm (d) t = 180 nm.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
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getmorefigures.php?uid=PMC5036029&req=5

f4: High resolution SEM images of GeSn thin film coating on Al foils (a) t = 20 nm (b) t = 50 nm (c) t = 100 nm (d) t = 180 nm.
Mentions: To better understand the nanoscale structure of GeSn thin film coated Al foils, high-resolution SEM images were measured. Figure 4(a–d) show the SEM images of GeSn thin films grown on Al foil with t = 20, 50, 100 and 180 nm, respectively. The GeSn thin film coatings present a smooth surface even grown upon normal Al foil substrate that were largely untreated from their commercial state. However, it is clear that nano-sized islands gradually atop the GeSn coatings that are thicker than 50 nm, as shown in Fig. 4(b–d). The XRD results suggest there probably exists Sn-rich islands. Here, we indeed observe these nano islands from the SEM images. To identify the elemental makeup of these nano-sized islands, we performed elemental mapping of GeSn films with a thickness of 180 nm grown on Al foil. As shown in Fig. 5(b), the Al element distributes uniformly with several light areas (in circled dash lines). Comparing this with the Sn element mapping as illustrated in Fig. 5(d), the nano islands appear Sn-rich as GeSn blotches. The results indicate an epitaxial breakdown exists in MBE grown GeSn thin films on Al foil substrate for thicknesses greater than 50 nm, which changes the surface morphology from a 2D growth mode to a 3D growth mode with relatively larger nm islands.

View Article: PubMed Central - PubMed

ABSTRACT

Germanium Tin (GeSn) films have drawn great interest for their visible and near-infrared optoelectronics properties. Here, we demonstrate large area Germanium Tin nanometer thin films grown on highly flexible aluminum foil substrates using low-temperature molecular beam epitaxy (MBE). Ultra-thin (10–180 nm) GeSn film-coated aluminum foils display a wide color spectra with an absorption wavelength ranging from 400–1800 nm due to its strong optical interference effect. The light absorption ratio for nanometer GeSn/Al foil heterostructures can be enhanced up to 85%. Moreover, the structure exhibits excellent mechanical flexibility and can be cut or bent into many shapes, which facilitates a wide range of flexible photonics. Micro-Raman studies reveal a large tensile strain change with GeSn thickness, which arises from lattice deformations. In particular, nano-sized Sn-enriched GeSn dots appeared in the GeSn coatings that had a thickness greater than 50 nm, which induced an additional light absorption depression around 13.89 μm wavelength. These findings are promising for practical flexible photovoltaic and photodetector applications ranging from the visible to near-infrared wavelengths.

No MeSH data available.


Related in: MedlinePlus