Dissolution of Germanium in Sulfuric Acid Based Solutions

Gan, Nobuko; Ogawa, Yuichi; Nagai, Takaya; Masaoka, Toru; Sebaai, Farid; Holsteyns, Frank; Mertens, Paul

doi:10.1149/06908.0277ecst

Cited by 4 publications

(5 citation statements)

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“…Ge wet etching with acidic H 2 O 2 has been adopted for a very long time, and the related mechanisms both on the nanoscale and the atomic scale have been extensively studied for the research associated with Ge surface passivation, Ge surface cleaning, and Ge wet etching processes , There are two different natural oxides, GeO and GeO 2 , on the surface of Ge . When H 2 O 2 was applied, the oxide which is primarily water-soluble GeO 2 will regrow.…”

Section: Results and Discussionmentioning

confidence: 99%

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Sub-10 μm-Thick Ge Thin Film Fabrication from Bulk-Ge Substrates via a Wet Etching Method

Wang,

Zhu,

Wen

et al. 2023

ACS Omega

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Low-defect density Ge thin films are crucial for studying the impact of defect density on the performance limits of Ge-based optical devices (optical detectors, LEDs, and lasers). Ge thinning is also important for Ge-based multijunction solar cells. In this work, Ge wet etching using three acidic H 2 O 2 solutions (HF, HCl, and H 2 SO 4 ) was studied in terms of etching rate, surface morphology, and surface roughness. HCl–H 2 O 2 –H 2 O (1:1:5) was demonstrated to wet-etch 535 μm-thick bulk-Ge substrates to 4.1 μm with a corresponding RMS surface roughness of 10 nm, which was the thinnest Ge film from bulk-Ge via a wet etching method to the best of our knowledge. The good quality of pre-etched bulk-Ge was preserved, and the low threading dislocation density of 6000–7000 cm –2 was maintained after the etching process. This approach provides an inexpensive and convenient way for accurate Ge substrate thinning in applications such as multijunction solar cells and sub-10 μm-thick Ge thin film preparation, which enables future studies of low-defect density Ge-based devices such as photodetectors, LEDs, and lasers.

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Section: Results and Discussionmentioning

confidence: 99%

“… 38 32 , 39 There are two different natural oxides, GeO and GeO 2 , on the surface of Ge. 40 When H 2 O 2 was applied, the oxide which is primarily water-soluble GeO 2 will regrow. This oxide dissolves slowly in H 2 O and can be removed more rapidly by acids.…”

Section: Results and Discussionmentioning

confidence: 99%

Sub-10 μm-Thick Ge Thin Film Fabrication from Bulk-Ge Substrates via a Wet Etching Method

Wang,

Zhu,

Wen

et al. 2023

ACS Omega

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“…This appears noteworthy given that the H300 thin film was fabricated from an A900 thin film via additional heat treatment at a lower temperature. However, the incorporation of H 2 O and the creation of hydrates may lead to the growth of the microstructure according to the chemical reactions given in Equation () and () [ 35,49,51,52 ]

\left(\text{GeO}\right)_{2} \left(\text{+ H}\right)_{2} \text{O} \leftrightarrow \left(\text{GeH}\right)_{2} \left(\text{O}\right)_{3} \left(\right. \text{aq} \left.\right)

$$\left(\text{GeO}\right)_{2} \left(\text{+ 2H}\right)_{2} \text{O } \leftrightarrow \text{ Ge} \left(\left(\right.

…”

Section: Resultsmentioning

confidence: 99%

Section: Solubilitymentioning

confidence: 99%

Effects of Heat Treatment on the Microstructure and Optical Properties of Sputtered GeO₂ Thin Films

Nam

Bae

et al. 2023

Adv Eng Mater

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Microstructure and composition significantly influence the physical properties of thin films. Therefore, these can be adapted to enhance the functionality of thin films for practical applications. Herein, the anomalous microstructural evolution of sputtered GeO2 thin films based on postdepositional heat treatments is reported. Temperature‐dependent microstructural variations are investigated systematically via a combinatorial postdepositional heat treatment employing a natural thermal gradient in a tube furnace. Heat treatment under an oxidizing atmosphere results in a transition from the amorphous phase to the quartz phase, and subsequent heat treatments under a reducing atmosphere cause H2O‐incorporated chemical reactions. Hence, these conditions create unique microstructural features and yield optical transmittance variations in the GeO2 thin films. The phase transition induces the formation of spherulitic hexagonal GeO2 crystallites, and further increase in the temperature promotes the agglomeration of crystallites in the amorphous matrix. The incorporation of H2O results in the growth of the microstructure, and the chemical reduction to Ge metal begins to generate small granules from the boundary of the microstructures. The experimental results and proposed mechanisms presented herein for the microstructural and compositional changes serve as references for designing the physical properties of thin films.

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“…Further, the Ge 2 p 3/2 core‐level spectra from the KCN‐etched CZGTS (Ge/(Ge + Sn) = 0.2) reference sample is also included and the results indicate that a KCN etch treatment applied to the CZGTS absorber surface removes the Ge‐oxide species and leaves a clean surface with metal‐sulfide components only. It is not excluded that another treatment or water could actually remove the Ge‐oxide species at the surface of the absorber, since it was reported that GeO 2 is soluble in aqueous solutions, [ 25 ] but has not been studied in this work.…”

Section: Resultsmentioning

confidence: 99%

Properties of the Interface Between the Atomic Layer Grown Zinc–Tin–Oxide and Cu₂ZnGeS₄ Relevant for Kesterite Thin‐Film Solar Cells

Martin,

Saini,

Babucci

et al. 2023

Physica Status Solidi (a)

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Recently, a record open‐circuit voltage (1.1 V) is obtained for wide‐bandgap Cu2ZnGeS4 (CZGS) thin‐film solar cells with a Zn1−xSnxOy (ZTO) buffer grown by atomic layer deposition (ALD) (N. Saini et al. Sol. RRL 2021, 2100837). However, a low short‐circuit current and a small variation in device performance with ZTO properties are observed, suggesting similar interface properties. Since the CZGS absorber cannot be etched due to peeling, it is suggested that the presence of an oxide interlayer can influence the device performance. Here, the chemical and electronic properties of the near‐surface region of CZGS absorber and its interface with ZTO buffers with varying properties (bandgap and thickness) are studied nondestructively by employing excitation‐dependent X‐ray photoelectron spectroscopy. The formation of Ge oxide species is indicated at the absorber surface during device fabrication, which is preserved during ALD. Further, it is shown that the ZTO/CZGS interface properties are similar and not influenced by variations in ZTO properties, which can explain the small variation in device performance. Thus, attention shall be given to possible absorber surface cleaning treatment typically applied before the buffer deposition for Ge‐containing CZGS, and an optimization of the ALD ZTO buffer layer growth shall be considered for a non‐etched absorber.

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Dissolution of Germanium in Sulfuric Acid Based Solutions

Cited by 4 publications

References 1 publication

Sub-10 μm-Thick Ge Thin Film Fabrication from Bulk-Ge Substrates via a Wet Etching Method

Sub-10 μm-Thick Ge Thin Film Fabrication from Bulk-Ge Substrates via a Wet Etching Method

Effects of Heat Treatment on the Microstructure and Optical Properties of Sputtered GeO₂ Thin Films

Properties of the Interface Between the Atomic Layer Grown Zinc–Tin–Oxide and Cu₂ZnGeS₄ Relevant for Kesterite Thin‐Film Solar Cells

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Dissolution of Germanium in Sulfuric Acid Based Solutions

Cited by 4 publications

References 1 publication

Sub-10 μm-Thick Ge Thin Film Fabrication from Bulk-Ge Substrates via a Wet Etching Method

Sub-10 μm-Thick Ge Thin Film Fabrication from Bulk-Ge Substrates via a Wet Etching Method

Effects of Heat Treatment on the Microstructure and Optical Properties of Sputtered GeO2 Thin Films

Properties of the Interface Between the Atomic Layer Grown Zinc–Tin–Oxide and Cu2ZnGeS4 Relevant for Kesterite Thin‐Film Solar Cells

Contact Info

Product

Resources

About

Effects of Heat Treatment on the Microstructure and Optical Properties of Sputtered GeO₂ Thin Films

Properties of the Interface Between the Atomic Layer Grown Zinc–Tin–Oxide and Cu₂ZnGeS₄ Relevant for Kesterite Thin‐Film Solar Cells