Experiments towards size and dopant control of germanium quantum dots for solar applications

Brittany L. Oliva-Chatelain; Andrew R. Barron; Brittany L. Oliva-Chatelain; Andrew R. Barron

doi:10.3934/matersci.2016.1.1

AIMS Materials Science

2016, Volume 3, Issue 1: 1-21. doi: 10.3934/matersci.2016.1.1

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Experiments towards size and dopant control of germanium quantum dots for solar applications

Brittany L. Oliva-Chatelain ¹,
Andrew R. Barron ^{1,2,3
,
,}

1.
Department of Chemistry, Rice University, Houston, Texas 77005, USA
2.
Department of Mechanical Engineering and Materials Science, Rice University, Houston, Texas 77005, USA
3.
Energy Safety Research Institute (ESRI), Swansea University Bay Campus, Swansea, SA1 8EN, Wales, UK

Received: 23 November 2015 Accepted: 16 December 2015 Published: 18 December 2015

While the literature for the doping of silicon quantum dots (QDs) and nanocrystals (NCs) is extensive, reports of doping their germanium analogs are sparse. We report a range of attempts to dope Ge QDs both during and post-synthesis. The QDs have been characterized by TEM, XPS, and I/V measurements of SiO₂ coated QD thin films in test cells using doped Si substrates. The solution synthesis of Ge QDs by the reduction of GeCl₄ with LiAlH₄ results in Ge QDs with a low level of chlorine atoms on the surface; however, during the H₂PtCl₆ catalyzed alkylation of the surface with allylamine, to enable water solubility of the Ge QDs, chlorine functionalization of the surface occurs resulting in p-type doping of the QD. A similar location of the dopant is proposed for phosphorus when incorporated by the addition of PCl₃ during QD synthesis; however, the electronic doping effect is greater. The detected dopants are all present on the surface of the QD (s-type), suggesting a self-purification process is operative. Attempts to incorporate boron or gallium during synthesis were unsuccessful.
- dopant,
- quantum dot,
- germanium,
- silica,
- phosphorous
Citation: Brittany L. Oliva-Chatelain, Andrew R. Barron. Experiments towards size and dopant control of germanium quantum dots for solar applications[J]. AIMS Materials Science, 2016, 3(1): 1-21. doi: 10.3934/matersci.2016.1.1

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Abstract

While the literature for the doping of silicon quantum dots (QDs) and nanocrystals (NCs) is extensive, reports of doping their germanium analogs are sparse. We report a range of attempts to dope Ge QDs both during and post-synthesis. The QDs have been characterized by TEM, XPS, and I/V measurements of SiO₂ coated QD thin films in test cells using doped Si substrates. The solution synthesis of Ge QDs by the reduction of GeCl₄ with LiAlH₄ results in Ge QDs with a low level of chlorine atoms on the surface; however, during the H₂PtCl₆ catalyzed alkylation of the surface with allylamine, to enable water solubility of the Ge QDs, chlorine functionalization of the surface occurs resulting in p-type doping of the QD. A similar location of the dopant is proposed for phosphorus when incorporated by the addition of PCl₃ during QD synthesis; however, the electronic doping effect is greater. The detected dopants are all present on the surface of the QD (s-type), suggesting a self-purification process is operative. Attempts to incorporate boron or gallium during synthesis were unsuccessful.

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