FIG 2 - uploaded by Elhadj Marwane Diallo
Content may be subject to copyright.
Source publication
In the recent past, with the advent of transient electronics for mostly implantable and secured electronic applications, the whole field effect transistor structure has been dissolved in a variety of chemicals. Here, we show simple water soluble nano-scale (sub-10 nm) germanium oxide (GeO2) as the dissolvable component to remove the functional stru...
Citations
... In high-resolution XPS spectra, both the Ge 2p and Sn 3d signals were each split into two peaks corresponding to Ge 2p 1/2 , Ge 2p 3/2 , Sn 3d 5/2 , and Sn 3d 3/2 , respectively. 26,27 Peaks which represent Ge 2+ and Sn 2+ were be observed, indicating that the incorporation of Ge and Sn do not alter the oxygen vacancy concentration. Fig. 4(c) shows the Pr 3d 5/ 2 and Pr 3d 3/2 XPS spectra, where four peaks representing Pr 4+ and Pr 3+ were clearly discernible. ...
Perovskite-type solid electrolytes exhibit a diverse range of conductive properties due to the competition and coupling of multiple degrees of freedom. In perovskite structures, B-site and X-site ions form topological octahedral sublattices, which are instrumental in regulating transport properties for various charge carriers. However, research focused on the relationship between octahedral distortion and conductive properties in perovskite-type proton conductors remains limited. In this study, dopants such as Ge, Sn, Pr, and Ce were selected to modify the degree of BO6 octahedral distortion in CaHf0.9Sc0.1O3−δ. The relationships between conductivity, transport number, mobility, and the distortion degree were systematically investigated. The data indicate that both proton and oxygen ion mobilities initially increase with the octahedral distortion angle and then decrease, and CaHf0.8Sn0.1Sc0.1O3−δ with an octahedral distortion angle of 15.6°, exhibited the highest ionic mobilities and conductivities. The BO6 octahedral distortion appears to limit oxide ion conduction while enhancing the proton transport number. However, excessive doping generates additional oxygen vacancies, which adversely affect proton conduction. Under the combined influence of these factors, CaHf0.8Ce0.1Sc0.1O3−δ achieved the highest proton transport number of 0.503 at 800 °C. Overall, this work provides insights into the relationship between octahedral distortion and conductive properties, suggesting that co-doping is a feasible approach for further regulating carrier mobility properties.
... [40,41] Higher oxidation states than Ge(I) are not present, as the Ge 3d peak for Ge(II) was not detected at more positive binding energies, i. e. the Ge 3d peak for Ge(II) has been reported at 32.6 and 32.8 eV. [40,42] For all the measured samples, the presence of the Ge(0) is also confirmed by the position of the Ge 2p 3/2 peaks in Figure 2b. [42] A lowintensity shoulder on the high binding energy side of the Ge 2p 3/2 peaks originates from Ge(I). ...
... [40,42] For all the measured samples, the presence of the Ge(0) is also confirmed by the position of the Ge 2p 3/2 peaks in Figure 2b. [42] A lowintensity shoulder on the high binding energy side of the Ge 2p 3/2 peaks originates from Ge(I). ...
Germanium is a promising basis for nanomaterials due to its low toxicity and valuable optical and electronic properties. However, germanium nanomaterials have seen little research compared to other group 14 elements due to unpredictable chemical behavior and high costs. Here, we report the dehydrocoupling of o‐tolylgermanium trihydride to amorphous nanoparticles. The reaction is facilitated through reflux at 162 °C and can be accelerated with an amine base catalyst. Through cleavage of both H2 and toluene, new Ge−Ge bonds form. This results in nanoparticles consisting of crosslinked germanium with o‐tolyl termination. The particles are 2–6 nm in size and have masses above approximately 3500 Da. The organic substituents are promising for further functionalization. Combined with strong absorption up to 600 nm and moderate solubility and air stability, there are numerous possibilities for future applications.
... Additionally, hexagonal GeO 2 and amorphous GeO 2 possess water solubility, prompting research into their potential utilization in emerging applications such as secure elements and eco-friendly processes. 8,36,37 Consequently, the development of germanium oxides with tuned defects, vacancies, and high stoichiometries is necessary to increase their potential for various applications. Widely used thin-film processes include sputtering, thermal processing, and chemical vapor deposition (CVD). ...
This study describes the synthesis of 12 new germanium complexes containing β-diketonate and/or N-alkoxy carboxamidate-type ligands as precursors for GeO2 through atomic layer deposition (ALD). A series of Ge(β-diketonate)Cl complexes such as Ge(acac)Cl (1) and Ge(tmhd)Cl (2) were synthesized by using acetylacetone (acacH) and 2,2,6,6-tetramethyl-3,5-heptanedione (tmhdH). N-Alkoxy carboxamidate-type ligands such as N-methoxypropanamide (mpaH), N-methoxy-2,2-dimethylpropanamide (mdpaH), N-ethoxy-2-methylpropanamide (empaH), N-ethoxy-2,2-dimethylpropanamide (edpaH), and N-methoxybenzamide (mbaH) were used to afford further substituted complexes Ge(acac)(mpa) (3), Ge(acac)(mdpa) (4), Ge(acac)(empa) (5), Ge(acac)(edpa) (6), Ge(acac)(mba) (7), Ge(tmhd)(mpa) (8), Ge(tmhd)(mdpa) (9), Ge(tmhd)(empa) (10), Ge(tmhd)(edpa) (11), and Ge(tmhd)(mba) (12), respectively. Thermogravimetric analysis curves, which mostly exhibited single-step weight losses, were used to determine the evaporation properties of complexes 1–12. Interestingly, liquid complex 2 has no residue at 198 °C and therefore exhibits excellent vaporization properties and high volatility. Single-crystal X-ray diffraction studies of 1 and 7 demonstrated that the complexes had monomeric molecular structures with germanium chelated by the oxygen atoms of one or two bidentate ligands, respectively. An ALD process was developed for the growth of GeO2 using Ge(tmhd)Cl (2) as a new precursor and H2O2 as an oxidant. This study demonstrates the achievement of self-limiting growth of GeO2 films by varying the duration of injection/purge, with an observed ALD window at deposition temperatures ranging from 300 to 350 °C. The saturated growth per cycle of the GeO2 film was determined as 0.27 Å/cycle at a deposition temperature of 300 °C. The deposited films were observed to be amorphous consisting of GeO2.
... According to Table 2, the process of surface modification of catalysts is often linked to the investigation of adsorption and reaction phenomena, and it can be linked to the binding energy range for Ge and C state. This involves subjecting the catalysts to specific gases or liquids and analyzing the surface chemical 52,53 Through this approach, it is possible to detect the formation of reaction intermediates or by-products during the photocatalytic process. ...
Activated carbon/GeO2 composites were synthesized using the sol-gel method and then used as catalysts for the photodegradation of organic pollutants methylene blue (MB) and congo red (CR). The composites were characterized using an X-ray diffractometer and Fourier transform infrared spectroscopy to analyze the structure and chemical bonds of the composite materials, respectively. The ultraviolet-visible (UV-vis) absorption wavelength ranges of the composites toward the pollutants were 550-700 nm for MB and 450-550 for CR. The band gap energies of the composites were calculated, with the values found to be <4.5 eV. It was shown that the adsorption ability of the composites increased with the irradiation time of the pollutants. Furthermore, the adsorption kinetics data were found to be a good fit to a pseudo-first-order kinetics model.
... The etch is performed in two steps: Ge is etched with a 50 sccm CF 4 plasma, and the organic polymer is etched using the same O 2 /CF 4 mixture as the PI passivation layer. The Ge sacrificial layer is etched by soaking the wafer in deionized H 2 O for a few hours, thanks to the solubility of GeO 2 in H 2 O [27]. This process has been shown to be compatible with other polymer mixed ionic and electronic conductors [28,29]. ...
We describe a photolithographic process to fabricate organic microdevices on flexible substrates that relies on photolithography and dry etching and is entirely compatible with standard cleanroom wafer processing equipment. A conductive polymer is used as active material to fabricate organic electrochemical transistors on a flexible polyimide substrate. The transistors are operated both with a solid-state ion gel electrolyte and an aqueous electrolyte, thus demonstrating their applicability as building blocks as both flexible integrated circuits and biosensors. Miniaturized transistors with 2 μm-long channels are also demonstrated to showcase the ability of the microfabrication process to define small features. We believe the proposed process flow offers a high resolution alternative to printing techniques by taking full advantage of the superior reliability of established semiconductor device manufacturing techniques and facilities.
... Furthermore, Fig. 3c shows the XPS is full of sunflower-like GeO 2 /C sample consisting of Ge, O, C, and N elements, which is consistent with the TEM mapping characterization. Moreover, the enlarged Ge 3d profile (in Fig. 3d) corresponds to Ge 4+ (germanium dioxide) of this sample [47]. Figure 3e shows the fine spectrum of O 1 s; from the fitted results, one can see this spectrum consists of high percentage of O-Ge peak and small amount of carbon O-C peak. ...
The novel nanoscale fall sunflower-like GeO2/C composite was engineered by electrospinning and annealing approach. In this structure, plenty of ultrafine GeO2 particles were uniformly anchored in the carbon nanofiber, which provides rich buffer space and convenient electron/ion transport channel. Therefore, the corresponding fall sunflower-like GeO2/C composite electrode exhibits high reversible capacities of 1055, 702, 428, and 311 mAh g⁻¹ at current densities of 0.2, 0.4, 2.0, and 3.0 A g⁻¹, respectively. Moreover, the CV measurement analysis demonstrates that the electrochemical reaction process of this fall sunflower-like GeO2/C composite electrode is mainly lithium diffusion behavior. This excellent lithium storage performance promotes the practical application of fall sunflower-like GeO2/C composite.
Graphical abstract
... However, unlike silicon dioxide, germanium oxide is unstable in air. Although GeO 2 has several crystal polymorphs, amorphous and alpha-quartztype GeO 2 are soluble in water [12][13][14]. Therefore, GeO 2 can be transferred to the substrate surface in the form of a solution. ...
A printable-formation method for Ge films using a GeO2 solution was developed in this study. The GeO2 film was prepared by applying GeO2 ink on a glass substrate and reducing it using high-pressure H2-based plasma. The crystallinity, electrical conductivity, and photosensitivity of the films were examined before and after the plasma treatment. The film transformed from amorphous GeO2 to crystalline Ge after treatment with the H2-based plasma. The Ge film obtained after H2 plasma reduction exhibited an electrical resistivity of 4000 Ω cm and a photosensitivity of 1.9 under AM 1.5G illumination of 100 mW cm⁻². In addition, the dependence of the reduction behavior of the GeO2 film on the process parameters, such as the input power, substrate temperature, treatment time, and hydrogen concentration, were investigated systematically. The reduction of GeO2 by H2 plasma proceeded with an increase in the input power. The thickness of the reduced Ge film depended strongly on the substrate temperature, and the plasma reduction process required a low reduction temperature and short reaction time as compared to those of the thermal reduction process. The presence of only 4% H2 gas in the process atmosphere played an important role in the reduction and crystallization of the Ge film, although pure He plasma could also reduce the GeO2 film. Thus, we demonstrated the position-controlled preparation of Ge films using a commercial inkjet printer loaded with a GeO2 ink solution.
... Germanium (Ge) has long been a desirable material in the semiconductor industry because of its high mobility and small bandgap. [35] However, it oxidizes if exposed to the atmosphere and forms Germanium Oxide (GeO 2 ) which can be removed by dissolving with water. This effect was used to demonstrate forward transfer of electronics by Sameshima et al. [33] GeO 2 was formed in situ by sputtering Ge in the presence of oxygen and argon gas. ...
... Other GeO 2 deposition approaches include using e-Beam to deposit germanium films followed by oxidizing in a furnace, [34] or oxidizing a Ge wafer in a furnace,. [35] However, we found that these methods are not as scalable as sputtering since all three steps (Ge deposition, oxidation, and annealing) can be done in one tool, minimizing the possibility of imperfections. In general, thicker sputtered GeO 2 layers (<1000 nm) were observed to dissolve faster, confirming the results of Sameshima et al., [33] which can lead to premature failure in the more layered process needed for collagen, as shown in Figure S1B in the Supporting Information. ...
Collagen has emerged as an attractive bioelectronics substrate candidate, given its biological origins as a structural protein found in organisms. Substrates for implantable electronics should be biocompatible and have similar mechanical properties to implant target tissues. Furthermore, the characteristic amino acid sequences in collagen promote cell adhesion, migration, and proliferation, all of which are advantageous when compared to commonly explored cellulose and silk. However, denaturation temperature and swelling in water/vacuum have been fundamental barriers to device fabrication on collagen. It is here described how these problems can be avoided for the fabrication of semiconductor devices on collagen. Transfer printing using a sacrificial layer of germanium oxide is used to fabricate capacitors, transistors, and an integrated inverter transistor circuits on the collagen substrate. The mobility and threshold voltage of the transistors on collagen show only ≈41% and ≈22% drop compared to the ones on rigid silicon substrate. The enzymatic digestion and swelling ratio of collagen can be decreased by 80% and 175%, respectively, via glutaraldehyde cross‐linking, while mechanical stiffness increases by more than 270%. This work demonstrates how collagen can be used as a bioelectronics substrate with tunable properties, thereby expanding its application range from transient to more permanent implantable electronics.
... The Ge 4+ is known to be well soluble in aqueous solution. 57 However, Ge 4+ together with Ge 3+ and Ge 2+ exhibited an apparent greater bonding on the surface of Si 0.49 Ge 0.51 . In addition, the existence of Ge-Cl could be assigned to the 0.6 eV chemical shift 32-34 as supported by the Cl 2p spectra presented earlier. ...
In this atomic-scale study on wet etching, the importance of surface chemistry, in particular the nature of the surface oxides, is demonstrated for technologically relevant group IV semiconductors, Ge and SiGe. Elemental quantification of Ge in hydrochloric acid solution containing hydrogen peroxide showed a striking impact of the Si bulk concentration on the kinetics of etching. Post operando surface analysis provided insight into the oxide product formed after etching: a non-homogeneous porous layer with a depletion of Ge components at the outer surface due to pull out effects. Oxide formation was verified by microscopic imaging. We provide basic reaction schemes that help to elucidate the results.
... Since oxidation is often seen as detrimental to the properties of materials and devices (e.g., it could introduce scattering sources that reduce the carrier mobility), the exfoliated GeAs flakes were immersed in deionized (DI) water to remove the "native" oxide. This is a procedure commonly used for Ge structures [25][26][27] and takes advantage of the water solubility of GeO 2 . 28 As shown in Figure 1c, after immersion in deionized water for 3 h, the Ge 3d peak corresponding to GeO 2 is significantly reduced to about 10% of the intensity of Ge coordinated to As. ...
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 (GeS2). 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.
