TY - JOUR

T1 - Sintering and reorganization of electrochemically etched mesoporous germanium layers in various atmospheres

AU - Garralaga Rojas, E.

AU - Hensen, J.

AU - Baur, C.

AU - Brendel, R.

N1 - Funding Information: The authors would like to thank Bianca Gehring for the technical assistance. The financial support of this work by the German Ministry for Economy and Technology under Contract no. 50JR0641 is gratefully acknowledged. E. Garralaga Rojas specially thanks the European Space Agency for the financial support of his work in the framework of the Networking Partnering Initiative (Co. no. 20250/06/NL/GLC).

PY - 2011/1

Y1 - 2011/1

N2 - We investigate sintering and reorganization of electrochemically etched mesoporous Ge layers. Sintering in nitrogen, forming gas, or argon atmospheres always yields a reorganized and oxidized porous layer. Water-insoluble Ge native oxides produced during etching do not hinder thermal reorganization, but evolve to water soluble oxides during annealing. Reorganized porous layers hence dissolve in subsequent water or HF dips. Sintering in hydrogen atmospheres removes native Ge oxides and prevents oxidation of porous layers. Porous layers with porosities less than 30% exhibit a compact closed surface after sintering, whereas porous layers with porosities exceeding 50% collapse. The porosity decreases linearly in a range of 57%45% for electrolyte concentrations and in a range of 3550 wt% for a specific resistivity of 0.013 Ω cm and an etching current density of 5 mA cm-2. We obtain porosities below 30% by using substrate resistivities in the 0.0150.030 Ω cm range, etching current densities below 2.5 mA cm-2 and an electrolyte concentration of HF 50 wt%.

AB - We investigate sintering and reorganization of electrochemically etched mesoporous Ge layers. Sintering in nitrogen, forming gas, or argon atmospheres always yields a reorganized and oxidized porous layer. Water-insoluble Ge native oxides produced during etching do not hinder thermal reorganization, but evolve to water soluble oxides during annealing. Reorganized porous layers hence dissolve in subsequent water or HF dips. Sintering in hydrogen atmospheres removes native Ge oxides and prevents oxidation of porous layers. Porous layers with porosities less than 30% exhibit a compact closed surface after sintering, whereas porous layers with porosities exceeding 50% collapse. The porosity decreases linearly in a range of 57%45% for electrolyte concentrations and in a range of 3550 wt% for a specific resistivity of 0.013 Ω cm and an etching current density of 5 mA cm-2. We obtain porosities below 30% by using substrate resistivities in the 0.0150.030 Ω cm range, etching current densities below 2.5 mA cm-2 and an electrolyte concentration of HF 50 wt%.

KW - Lift-off

KW - Porous germanium

KW - Sintering

UR - http://www.scopus.com/inward/record.url?scp=78149361324&partnerID=8YFLogxK

U2 - 10.1016/j.solmat.2010.04.042

DO - 10.1016/j.solmat.2010.04.042

M3 - Article

AN - SCOPUS:78149361324

VL - 95

SP - 292

EP - 295

JO - Solar Energy Materials and Solar Cells

JF - Solar Energy Materials and Solar Cells

SN - 0927-0248

IS - 1

ER -