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Laser-driven phase segregation and tailoring of compositionally graded microstructures in Si-Ge nanoscale thin films

Laser-driven phase segregation and tailoring of compositionally graded microstructures in Si-Ge nanoscale thin films
Laser-driven phase segregation and tailoring of compositionally graded microstructures in Si-Ge nanoscale thin films
The ability to manipulate the composition of semiconductor alloys on-demand and at nanometer scale resolutions is a powerful tool that could be exploited to tune key properties such as the electronic bandgap, mobility, and refractive index. However, existing methods to modify the composition involve altering the stoichiometry by temporal or spatial modulation of the process parameters during material growth, limiting the scalability and flexibility for device fabrication. Here, we report a laser processing method for localized tailoring of the composition in amorphous silicon-germanium (a-SiGe) nanoscale thin films on silicon substrates, post-deposition, by controlling phase segregation through the scan speed of the laser-induced molten zone. Laser driven phase segregation at speeds adjustable from 0.1 to 100 mm s-1 allows access to previously unexplored solidification dynamics. The steady-state spatial distribution of the alloy constituents can be tuned directly by setting the constant laser scan speed to achieve indefinitely long Si1-xGex microstructures exhibiting the full range of compositions (0<x<1). To illustrate the potential, we demonstrate a photodetection application by exploiting the laser-written polycrystalline SiGe microstripes, showing tunability of the optical absorption edge over a wavelength range of 200nm. Our method can be applied to pseudo-binary alloys of ternary semiconductors, metals,ceramics and organic crystals, which have phase diagrams similar to that of SiGe alloys. This study opens a route for direct laser writing of novel devices made of alloy microstructures with tunable composition profiles, including graded-index waveguides and meta-surfaces, multi-spectral photodetectors, full-spectrum solar cells, and lateral heterostructures.
laser materials processing, semiconductor alloys, nanoscale thin films, compositionally graded microstructures, phase segregation, silicon-germanium
1944-8244
9457–9467
Aktaş, Ozan
2e90db41-f409-431f-9827-2e2577a52457
Oo, Swe
6495f6da-8f17-4484-98fb-6151b4efbd9a
MacFarquhar, Stuart, James
cff30fb5-a4b6-44ab-b1b3-138e7020fba3
Mittal, Vinita
fd5ee9dd-7770-416f-8f47-50ca158b39b0
Chong, Harold
795aa67f-29e5-480f-b1bc-9bd5c0d558e1
Peacock, Anna
685d924c-ef6b-401b-a0bd-acf1f8e758fc
Aktaş, Ozan
2e90db41-f409-431f-9827-2e2577a52457
Oo, Swe
6495f6da-8f17-4484-98fb-6151b4efbd9a
MacFarquhar, Stuart, James
cff30fb5-a4b6-44ab-b1b3-138e7020fba3
Mittal, Vinita
fd5ee9dd-7770-416f-8f47-50ca158b39b0
Chong, Harold
795aa67f-29e5-480f-b1bc-9bd5c0d558e1
Peacock, Anna
685d924c-ef6b-401b-a0bd-acf1f8e758fc

Aktaş, Ozan, Oo, Swe, MacFarquhar, Stuart, James, Mittal, Vinita, Chong, Harold and Peacock, Anna (2020) Laser-driven phase segregation and tailoring of compositionally graded microstructures in Si-Ge nanoscale thin films. ACS Applied Materials & Interfaces, 12 (8), 9457–9467. (doi:10.1021/acsami.9b22135).

Record type: Article

Abstract

The ability to manipulate the composition of semiconductor alloys on-demand and at nanometer scale resolutions is a powerful tool that could be exploited to tune key properties such as the electronic bandgap, mobility, and refractive index. However, existing methods to modify the composition involve altering the stoichiometry by temporal or spatial modulation of the process parameters during material growth, limiting the scalability and flexibility for device fabrication. Here, we report a laser processing method for localized tailoring of the composition in amorphous silicon-germanium (a-SiGe) nanoscale thin films on silicon substrates, post-deposition, by controlling phase segregation through the scan speed of the laser-induced molten zone. Laser driven phase segregation at speeds adjustable from 0.1 to 100 mm s-1 allows access to previously unexplored solidification dynamics. The steady-state spatial distribution of the alloy constituents can be tuned directly by setting the constant laser scan speed to achieve indefinitely long Si1-xGex microstructures exhibiting the full range of compositions (0<x<1). To illustrate the potential, we demonstrate a photodetection application by exploiting the laser-written polycrystalline SiGe microstripes, showing tunability of the optical absorption edge over a wavelength range of 200nm. Our method can be applied to pseudo-binary alloys of ternary semiconductors, metals,ceramics and organic crystals, which have phase diagrams similar to that of SiGe alloys. This study opens a route for direct laser writing of novel devices made of alloy microstructures with tunable composition profiles, including graded-index waveguides and meta-surfaces, multi-spectral photodetectors, full-spectrum solar cells, and lateral heterostructures.

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Submitted date: 6 December 2019
Accepted/In Press date: 3 February 2020
e-pub ahead of print date: 3 February 2020
Published date: 2020
Keywords: laser materials processing, semiconductor alloys, nanoscale thin films, compositionally graded microstructures, phase segregation, silicon-germanium

Identifiers

Local EPrints ID: 437603
URI: http://eprints.soton.ac.uk/id/eprint/437603
ISSN: 1944-8244
PURE UUID: 2ef67957-7702-444f-90f7-a288c6f53bf2
ORCID for Ozan Aktaş: ORCID iD orcid.org/0000-0002-2255-7761
ORCID for Stuart, James MacFarquhar: ORCID iD orcid.org/0000-0002-4378-7670
ORCID for Vinita Mittal: ORCID iD orcid.org/0000-0003-4836-5327
ORCID for Harold Chong: ORCID iD orcid.org/0000-0002-7110-5761
ORCID for Anna Peacock: ORCID iD orcid.org/0000-0002-1940-7172

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Date deposited: 06 Feb 2020 17:32
Last modified: 03 Jul 2020 04:01

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