Thermal oxidation of amorphous germanium thin films on SiO<sub>2</sub>substrates

Valladares, L. De Los Santos; Domínguez, A.; Ionescu, Adrian M.; Brown, A.; Sepe, Alessandro; Steiner, Ullrich; Quispe, Oswaldo Avalos; Holmes, S. N.; Majima, Yutaka; Langford, R. M.; Barnes, C. H. W.

doi:10.1088/0268-1242/31/12/125017

Cited by 8 publications

(6 citation statements)

References 39 publications

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“…The former is very close in energy to the peak found for GeAs 2 at 29.5 eV and can therefore be attributed to the Ge–As bond. The latter is significantly shifted toward higher binding energies and is due to the formation of germanium oxide (GeO 2 ). − The ratio between these two peaks is 1.2, proving the high degree of oxidation of the material within the probed volume. Interestingly, the As 3d core level shows only one peak at around 41 eV, while other possible features at higher binding energies due to arsenic oxide are absent .…”

Section: Resultsmentioning

confidence: 99%

A Scalable Method for Thickness and Lateral Engineering of 2D Materials

et al. 2020

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The physical properties of two-dimensional (2D) materials depend strongly on the number of layers. Hence, methods for controlling their thickness with atomic layer precision are highly desirable, yet still too rare, and demonstrated for only a limited number of 2D materials. Here, we present a simple and scalable method for the continuous layer-by-layer thinning that works for a large class of 2D materials, notably layered germanium pnictides and chalcogenides. It is based on a simple oxidation/ etching process, which selectively occurs on the topmost layers. Through a combination of atomic force microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, and X-ray diffraction experiments we demonstrate the thinning method on germanium arsenide (GeAs), germanium sulfide (GeS), and germanium disulfide (GeS 2). We use first-principles simulation to provide insights into the oxidation mechanism. Our strategy, which could be applied to other classes of 2D materials upon proper choice of the oxidation/etching reagent, supports 2D material-based device applications, e.g., in electronics or optoelectronics, where a precise control over the number of layers (hence over the material's physical properties) is needed. Finally, we also show that when used in combination with lithography, our method can be used to make precise patterns in the 2D materials.

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Section: Resultsmentioning

confidence: 99%

A Scalable Method for Thickness and Lateral Engineering of 2D Materials

et al. 2020

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“…Also, at high temperature we have to consider the formation of GeO gas that will be lost (in Fig. 3(b) oxygen concentration is very low at the free surface of the film), the mobility of species at 500 °C being increased 41,50 .…”

Section: Methodsmentioning

confidence: 99%

Ge nanoparticles in SiO2 for near infrared photodetectors with high performance

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Teodorescu

Prepelita

et al. 2019

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In this work we prepared films of amorphous germanium nanoparticles embedded in SiO 2 deposited by magnetron sputtering on Si and quartz heated substrates at 300, 400 and 500 °C. Structure, morphology, optical, electrical and photoconduction properties of all films were investigated. The Ge concentration in the depth of the films is strongly dependent on the deposition temperature. In the films deposited at 300 °C, the Ge content is constant in the depth, while films deposited at 500 °C show a significant decrease of Ge content from interface of the film with substrate towards the film free surface. From the absorption curves we obtained the Ge band gap of 1.39 eV for 300 °C deposited films and 1.44 eV for the films deposited at 500 °C. The photocurrents are higher with more than one order of magnitude than the dark ones. The photocurrent spectra present different cutoff wavelengths depending on the deposition temperature, i.e. 1325 nm for 300 °C and 1267 nm for 500 °C. These films present good responsivities of 2.42 AW −1 (52 μ W incident power) at 300 °C and 0.69 AW −1 (57 mW) at 500 °C and high internal quantum efficiency of ∼445% for 300 °C and ∼118% for 500 °C.

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“…A challenging problem to form SiGe NCS in SiO 2 matrix is the oxygen excess that may occur during deposition process or heating treatment. This oxygen excess can create various Ge suboxides with the increase of treatment temperature, some of them being unstable as GeO gas 38,39 .…”

mentioning

confidence: 99%

SiGe nanocrystals in SiO2 with high photosensitivity from visible to short-wave infrared

Stavarache

Logofatu

Sultan

et al. 2020

Sci Rep

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Films of SiGe nanocrystals (NCs) in oxide have the advantage of tuning the energy band gap by adjusting SiGe NCs composition and size. In this study, SiGe-SiO2 amorphous films were deposited by magnetron sputtering on Si substrate followed by rapid thermal annealing at 700, 800 and 1000 °C. We investigated films with Si:Ge:SiO2 compositions of 25:25:50 vol.% and 5:45:50 vol.%. TEM investigations reveal the major changes in films morphology (SiGe NCs with different sizes and densities) produced by Si:Ge ratio and annealing temperature. XPS also show that the film depth profile of SiGe content is dependent on the annealing temperature. These changes strongly influence electrical and photoconduction properties. Depending on annealing temperature and Si:Ge ratio, photocurrents can be 103 times higher than dark currents. The photocurrent cutoff wavelength obtained on samples with 25:25 vol% SiGe ratio decreases with annealing temperature increase from 1260 nm in SWIR for 700 °C annealed films to 1210 nm for those at 1000 °C. By increasing Ge content in SiGe (5:45 vol%) the cutoff wavelength significantly shifts to 1345 nm (800 °C annealing). By performing measurements at 100 K, the cutoff wavelength extends in SWIR to 1630 nm having high photoresponsivity of 9.35 AW−1.

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Thermal oxidation of amorphous germanium thin films on SiO₂substrates

Cited by 8 publications

References 39 publications

A Scalable Method for Thickness and Lateral Engineering of 2D Materials

A Scalable Method for Thickness and Lateral Engineering of 2D Materials

Ge nanoparticles in SiO2 for near infrared photodetectors with high performance

SiGe nanocrystals in SiO2 with high photosensitivity from visible to short-wave infrared

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Thermal oxidation of amorphous germanium thin films on SiO2substrates

Cited by 8 publications

References 39 publications

A Scalable Method for Thickness and Lateral Engineering of 2D Materials

A Scalable Method for Thickness and Lateral Engineering of 2D Materials

Ge nanoparticles in SiO2 for near infrared photodetectors with high performance

SiGe nanocrystals in SiO2 with high photosensitivity from visible to short-wave infrared

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Product

Resources

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Thermal oxidation of amorphous germanium thin films on SiO₂substrates