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The adsorption attributes of methyl naphthalene and naphthalene molecules on P-Germanane sheets are explored based on the density functional theory method. The novel P-Germanane stability is established based on formation energy and phonon band spectrum. The stable P-Germanane exhibits a band gap of 3.944 eV. The calculated adsorption energy infers that methyl naphthalene and naphthalene are physisorbed on P-Germanane sheets. The charge transfer reveals that P-Germanane sheets behave as donors of electrons and target molecules behave as acceptors. The electronic attributes of P-Germanane sheets get altered owing to methyl naphthalene and naphthalene adsorption inferred from the band structure, PDOS spectrum, and electron density difference diagrams. We identified global minima position upon adsorption of 1-methylnaphthalene, and naphthalene on P-Germanane, which are named as bridge, octal, and tetra sites and adsorption attributes are explored in these sites. The adsorption energy and relative energy gap variation are noticed to be maximum for tetra site orientation of naphthalene on P-Germanane. The outcome exposes that P-Germanane sheets can be used as adsorption substrates for the detection of methyl naphthalene and naphthalene molecules. [ABSTRACT FROM AUTHOR]

2D materials are being widely investigated for their potential application in light‐detecting devices. Very recently, a spin‐coated flexible 2D germanium‐based photodetector with great photocurrent density and responsivity as well as short rise and decay time is presented by Liu et. al. In this paper, the solid‐state single flake photodetector base on either pure germanane or (3‐hydroxypropyl)germanane is reported. Both prepared photodetectors while irradiated with different wavelengths of light exhibit outstanding responsivity of 1157 mA W−1 for GeH and 362 mA W−1 for (3‐hydroxypropyl)germanane, which exceeds Liu's flexible reported GeH photodetector (22 µA W−1) by more than five orders of magnitude. These constructed photodetectors also exhibit rise and fall times lower than 20 ms, which is also significantly faster than the GeH photodetector reported by Liu with rise and decay times 240 and 740 ms, respectively. [ABSTRACT FROM AUTHOR]

To confirm the feasibility of a theoretically proposed method of forming free-standing germanene [Araidai et al., J. Appl. Phys. 128, 125301 (2020).], we experimentally investigated the hydrogen desorption properties of hydrogen-terminated germanane (GeH) flakes. Thermal desorption spectroscopy analysis revealed that hydrogen desorption occurred during heating under an ultrahigh vacuum environment corresponding to a mass loss of 1.0 wt%. Moreover, we have found that using an ultrahigh vacuum, ambient and short-time annealing for hydrogen desorption is a key to sustain the crystal structures. [ABSTRACT FROM AUTHOR]

Germanane, a hydrogen-terminated graphane analogue of germanium has generated interest as a potential 2D electronic material. However, the incorporation and retention of extrinsic dopant atoms in the lattice, to tune the electronic properties, remains a significant challenge. Here, we show that the group-13 element Ga and the group-15 element As, can be successfully doped into a precursor CaGe2 phase, and remain intact in the lattice after the topotactic deintercalation, using HCl, to form GeH. After deintercalation, a maximum of 1.1% As and 2.3% Ga can be substituted into the germanium lattice. Electronic transport properties of single flakes show that incorporation of dopants leads to a reduction of resistance of more than three orders of magnitude in H2O-containing atmosphere after As doping. After doping with Ga, the reduction is more than six orders of magnitude, but with significant hysteretic behavior, indicative of water-activation of dopants on the surface. Only Ga-doped germanane remains activated under vacuum, and also exhibits minimal hysteretic behavior while the sheet resistance is reduced by more than four orders of magnitude. These Ga- and As-doped germanane materials start to oxidize after one to four days in ambient atmosphere. Overall, this work demonstrates that extrinsic doping with Ga is a viable pathway towards accessing stable electronic behavior in graphane analogues of germanium.

The current study highlights the ability of cubic germanane nanosheets to adsorb the glycol ethers, namely 2-methoxyethanol and 2-ethoxyethanol, which are used as major solvents in the semiconductor industry. Cubic germanane nanosheets were found to be structurally stable. Cubic germanane nanosheets exhibits a band gap of 2.247 eV, which has a semiconductor nature. We used cubic germanane nanosheets to adsorb 2-methoxyethanol and 2-ethoxyethanol. The change in the electronic properties of cubic germanane nanosheets is inferred from the band structure, electron density difference, and projected density of states spectrum. Moreover, both glycol ether molecules are physisorbed on cubic germanane nanosheets. The charge transfer results show that cubic germanane acts as a donor of electrons to 2-methoxyethanol and 2-ethoxyethanol molecules. From the results, it is evident that cubic germanane can be used to adsorb 2-methoxyethanol and 2-ethoxyethanol molecules. Thus, cubic germanane nanosheets can be used as a detecting element for glycol ethers. [Display omitted] • The energy gap of cubic germanane nanosheet is 2.247 eV. • The semicouducting cubic germanane is used to adsorb two glycol ethers, 2-methoxyethanol, and 2-ethoxyethanol. • The electronic properties of cubic germanane sheets changes due to 2-methoxyethanol, and 2-ethoxyethanol adsorption. • 2-methoxyethanol, and 2-ethoxyethanol are physisorbed on cubic germanane nanosheets. [ABSTRACT FROM AUTHOR]

Germanane is a two-dimensional material consisting of stacks of atomically thin germanium sheets. It's easy and low-cost synthesis holds promise for the development of atomic-scale devices. However, to become an electronic-grade material, high-quality layered crystals with good chemical purity and stability are needed. To this end, we studied the electrical transport of annealed methyl-terminated germanane microcrystallites in both high vacuum and ultrahigh vacuum. Scanning electron microscopy of crystallites revealed two types of behavior which arise from the difference in the crystallite chemistry. While some crystallites are hydrated and oxidized, preventing the formation of good electrical contact, the four-point resistance of oxygen-free crystallites was measured with multiple tips scanning tunneling microscopy, yielding a bulk transport with resistivity smaller than 1 Ω·cm. When normalized by the crystallite thickness, the resistance compares well with the resistance of hydrogen-passivated germanane flakes found in the literature. Along with the high purity of the crystallites, a thermal stability of the resistance at 280 °C makes methyl-terminated germanane suitable for complementary metal oxide semiconductor back-end-of-line processes. [ABSTRACT FROM AUTHOR]

Chemical functionalization represents a critical tool for van der Waals (vdW) layered nanomaterials in many aspects, ranging from the monolayer preparation by the solution exfoliation to the modulation of properties. Apart from attaching different chemical groups to one given nanomaterial, much less noticeable but fundamentally attractive is the isotope effect on the functional group, which can in principle tune the physical properties with unconverted chemical behaviors. Here, we report the isotope effect of hydrogen terminations in the layered Ge on lattice vibrations and electronic and atomic structures. We show that the Ge–Ge in-plane vibration responds to the mass variation of hydrogen terminations sensitively in frequencies, providing an indirect path to tune planar phonons through chemical bonds. A significant optical band gap modulation of 40 meV by −H and −D decorations is revealed, and the vdW gap increases by ∼0.3 Å, indicating the modification of layer–layer vdW interactions with isotope effect. The results not only unveil the fundamental isotope effect of hydrogen functionalization but also open up the effective band gap engineering toward germanane-based optoelectronic applications such as photodetectors and photocatalysts. [ABSTRACT FROM AUTHOR]

Group-14 Xenes beyond graphene such as silicene, germanene, and stanene have recently gained a lot of attention for their peculiar electronic properties, which can be tuned by covalent functionalization. Up until now, reported methods for the top-down synthesis of covalently functionalized silicene and germanene typically yield multilayered flakes with a minimum thickness of 100 nm. Herein, the ex situ covalent functionalization of germanene (fGe) is reported via 1,3-dipolar cycloaddition of the azomethine ylide generated by the decarboxylative condensation of 3,4-dihydroxybenzaldehyde and sarcosine. Amorphous few-layered sheets (average thickness of ≈6 nm) of dipolarophile germanene (GeX) are produced by thermal dehydrogenation of its fully saturated parent precursor, germanane (GeH). Spectroscopic evidence confirmed the emergence of the dipolarophilic sp 2 domains due to the dehydrogenation of germanane, and their sp 3 hybridization due to the covalent functionalization of germanene. Elemental mapping of the functionalized germanene revealed flakes with a very high abundance of carbon uniformly covering the germanium backbone. The 500 meV increase of the optical bandgap of germanene observed upon functionalization paves the way toward bandgap engineering of other group-14 Xenes, which could potentially be a major turning point in the fields of electronics, electrocatalysis, and photocatalysis., (© 2024 The Author(s). Small published by Wiley‐VCH GmbH.)

In recent years, 2D Group 14 graphane analogs, such as germanane, methyl germanane, and siloxene, have taken materials scientists by storm due to their facile synthesis procedures and the numerous attractive properties proffered. Due to their fascinating properties, these emerging Group 14 graphane analogs are studied for varied applications including supercapacitors, photocatalysts, and sensors. Although several groups have reported the viability of using Group 14 graphane analogs for the construction of biosensors, they are mainly based upon computational studies, and few experimental studies are conducted. This paper aims to experimentally investigate the feasibility of using germanane and siloxene‐based materials as 2D functional support for enzymatic systems. The heterogeneous electron transfer kinetics and the glucose sensing response of the as‐synthesized germanane, methyl germanane, and siloxene are examined, and the most outstanding material, germanane, is employed for further construction of electrochemical glucose biosensor. The fabricated biosensing platform delivers excellent analytical performances, displaying good linearity over various magnitudes of glucose concentrations, and possesses a low detection limit. The findings reported herein showcase the potential of applying these 2D Group 14 graphane analogs for future developments of highly selective and sensitive biosensors for biomedical, environmental monitoring, and food sampling applications. [ABSTRACT FROM AUTHOR]

Germanane (GeH), a graphane analogue, has attracted significant interest because of its optoelectronic properties; however, the environmental and biological effects of GeH have scarcely been investigated so far. Here we report a facile approach based on the Langmuir–Schaefer deposition to produce homogeneous and dense GeH monolayer films on various substrates. In view of possible applications and to extend the use of GeH to unexplored fields, we investigated its antibacterial activity for the first time and found that this promising 2D structure exhibits remarkable antibacterial activity against both Gram-negative and Gram-positive bacterial strains. [ABSTRACT FROM AUTHOR]

Germanane is a two-dimensional material consisting of stacks of atomically thin germanium sheets. It’s easy and low-cost synthesis holds promise for the development of atomic-scale devices. However, to become an electronic-grade material, high-quality layered crystals with good chemical purity and stability are needed. To this end, we studied the electrical transport of annealed methyl-terminated germanane microcrystallites in both high vacuum and ultrahigh vacuum. Scanning electron microscopy of crystallites revealed two types of behavior which arise from the difference in the crystallite chemistry. While some crystallites are hydrated and oxidized, preventing the formation of good electrical contact, the four-point resistance of oxygen-free crystallites was measured with multiple tips scanning tunneling microscopy, yielding a bulk transport with resistivity smaller than 1 Ω·cm. When normalized by the crystallite thickness, the resistance compares well with the resistance of hydrogen-passivated germanane flakes found in the literature. Along with the high purity of the crystallites, a thermal stability of the resistance at 280 °C makes methyl-terminated germanane suitable for complementary metal oxide semiconductor back-end-of-line processes.

Germanane (GeH), a germanium analogue of graphane, has recently attracted considerable interest because its remarkable combination of properties makes it an extremely suitable candidate to be used as 2D material for field effect devices, photovoltaics, and photocatalysis. Up to now, the synthesis of GeH has been conducted by substituting Ca by H in a β‐CaGe2 layered Zintl phase through topochemical deintercalation in aqueous HCl. This reaction is generally slow and takes place over 6 to 14 days. The new and facile protocol presented here allows to synthesize GeH at room temperature in a significantly shorter time (a few minutes), which renders this method highly attractive for technological applications. The GeH produced with this method is highly pure and has a band gap (Eg) close to 1.4 eV, a lower value than that reported for germanane synthesized using HCl, which is promising for incorporation of GeH in solar cells. [ABSTRACT FROM AUTHOR]

Energy harvesting and storing by dual-functional photoenhanced (photo-E) energy storage devices are being developed to battle the current energy hassles. In this research work, our investigations on the photoinduced efficiency of germanane (Ge-H) and its functionalized analogue cyanoethyl (Ge-C 2 -CN) are assessed as photocathodes in photo-E hybrid zinc-ion capacitors (ZICs). The evaluated self-powered photodetector devices made by these germanene-based samples revealed effective performances in photogenerated electrons and holes. The photo-E ZICs findings provided a photoinduced capacitance enhancement of ∼52% (for Ge-H) and ∼26% (for Ge-C 2 -CN) at a scan rate of 10 mV s -1 under 100 mW cm -2 illumination with 435 nm wavelength. Further characterizations demonstrated that the photo-E ZIC with Ge-C 2 -CN supply higher specific capacitance (∼6000 mF g -1 ), energy density (∼550 mWh kg -1 ), and power density (∼31,000 mW kg -1 ), compared to the Ge-H. In addition, capacitance retention of photo-E ZIC with Ge-C 2 -CN is ∼91% after 3000 cycles which is almost 6% greater than Ge-H. Interestingly, the photocharging voltage response in photo-E ZIC made by Ge-C 2 -CN is 1000 mV, while the photocharging voltage response with Ge-H is approximately 970 mV. The observed performances in Ge-H-based photoactive cathodes highlight the pivotal role of such two-dimensional materials to be applied as single architecture in new unconventional energy storage systems. They are particularly noteworthy when compared to the other advanced photo-E supercapacitors and could even be enhanced greatly with other suitable inorganic and organic functional precursors.

The germanium high theoretical capacity renders it as a promising anode material with 1384 mAh/g for Li (Li15Ge4) and 369 mAh/g for Na (NaGe) and K (KGe). Nevertheless, Ge suffers from volume variations due to alkali insertion, to mitigate this issue several strategies have been proposed. Among them the use of layered Ge‐based phases, obtained from the CaGe2 Zintl phase by topotactic deintercalation of Ca2+ to form the germanane (GeH)n. This last one has a particular morphology of Ge6 rings interconnected to form planes that buffers the volume changes and shortens the diffusion pathways. Here, we have studied the germanane alkali storage properties and 2150, 495 and 205 mAh/g of reversible capacity were obtained for Li, Na and K, respectively. These results indicate that germanane can store more alkali ions than the predicted phases, perform well at high rates and maintain a good capacity retention. [ABSTRACT FROM AUTHOR]

The rediscovery of graphene in 2004 has started an enormous chase in the research of 2D materials. A new family of layered 2D materials consisting of the 14th group elements beyond carbon has already been reported. Here, a new methodology in germanene chemistry is presented using germanane (Ge6H6) as a stable and easily accessible starting material for effective synthesis of novel germanene derivatives. The modification procedure utilizing strong bases—alkali metal arenides—for deprotonation of germanane and its subsequent functionalization with p‐nitrobenzyl bromide is described. Functionalization of germanene is confirmed by FT‐IR, Raman, and XPS spectroscopy as well as by X‐ray diffraction analysis. [ABSTRACT FROM AUTHOR]

Germanane, a hydrogen-terminated graphane analogue of germanium has generated interest as a potential 2D electronic material. However, the incorporation and retention of extrinsic dopant atoms in the lattice, to tune the electronic properties, remains a significant challenge. Here, we show that the group-13 element Ga and the group-15 element As, can be successfully doped into a precursor CaGe2 phase, and remain intact in the lattice after the topotactic deintercalation, using HCl, to form GeH. After deintercalation, a maximum of 1.1% As and 2.3% Ga can be substituted into the germanium lattice. Electronic transport properties of single flakes show that incorporation of dopants leads to a reduction of resistance of more than three orders of magnitude in H2O-containing atmosphere after As doping. After doping with Ga, the reduction is more than six orders of magnitude, but with significant hysteretic behavior, indicative of water-activation of dopants on the surface. Only Ga-doped germanane remains activated under vacuum, and also exhibits minimal hysteretic behavior while the sheet resistance is reduced by more than four orders of magnitude. These Ga- and As-doped germanane materials start to oxidize after one to four days in ambient atmosphere. Overall, this work demonstrates that extrinsic doping with Ga is a viable pathway towards accessing stable electronic behavior in graphane analogues of germanium.

Covalently functionalized germanane is a novel type of fluorescent probe that can be employed in material science and analytical sensing. Here, a fluorometric sensing platform based on methyl-functionalized germanane (CH 3 Ge) is developed for gas (humidity and ammonia) sensing, pH (1-9) sensing, and anti-counterfeiting. Luminescence (red-orange) is seen when a gas molecule intercalates into the interlayer space of CH 3 Ge and the luminescence disappears upon deintercalation. This allows for direct detection of gas absorption via fluorometric measurements of the CH 3 Ge. Structural and optical properties of CH 3 Ge with intercalated gas molecules are investigated by density functional theory (DFT). To demonstrate real-time and on-the-spot testing, absorbed gas molecules are first precisely quantified by CH 3 Ge using a smartphone camera with an installed color intensity processing application (APP). Further, CH 3 Ge-paper-based sensor is integrated into real food packets (e.g., fish and milk) to monitor the shelf life of perishable foods. Finally, CH 3 Ge-based rewritable paper is applied in water jet printing to illustrate the potential for secret communication with quick coloration and good reversibility by water evaporation., (© 2023 The Authors. Advanced Materials published by Wiley-VCH GmbH.)

First-principles calculations are performed to study the dual effect of spin-orbital coupling (SOC) and electric fields on the structure and electronic properties of germanane (Ge 2 H 2) and lithiated germanene (Ge 2 Li 2) nanosheets. Considering SOC effect, our results show that both Ge 2 H 2 and Ge 2 Li 2 nanosheets are stable under electric fields. It is found that the SOC effect can weaken the contribution of external electric fields, which leads to the decreasing of band gap in Ge 2 H 2 configuration under electric fields. Under electric fields, the transition from semiconductor to metal is found in both Ge 2 H 2 and Ge 2 Li 2 nanosheet. • SOC effect leads to the decreasing of band gap in germanane under electric fields. • Semiconductor to metal transition is found in both Ge 2 H 2 and Ge 2 Li 2 nanosheet under electric fields. • The transferred electrons in Ge 2 Li 2 nanosheet are localized around the germanene atoms under electric fields. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Investigation on adsorption of liver cirrhosis biomarkers volatiles on germanane nanosheet is carried out. • Liver cirrhosis biomarkers such as methanol, 2-pentanone and limonene are studied. • Liver cirrhosis biomarkers exhibits physisorption type of adsorption on germanane nanosheet. • Findings shows that germanane nanosheet can be used as nano biosensor for liver cirrhosis biomarkers. Abstract The present report investigates the geometric stability and electronic properties of germanane nanosheet, which shows a semiconductor nature. The germanane nanosheet is used as the base material for adsorption of liver cirrhosis biomarker namely methanol, 2-pentanone and limonene. The structural configuration, binding sites, charge transfer, variation in the energy gap along with adsorption energy are systematically explored. In addition, we investigated the energy band structure and density of states spectrum upon adsorption of liver cirrhosis biomarkers on germanane nanosheet. The present report lays the road for the possible application of monolayer material, namely germanane sheet, which shows excellent response towards liver cirrhosis biomarker volatiles. We suggest that the next generation nanosensors for detection of liver cirrhosis biomarker with high sensitivity material like germanane nanosheet. [ABSTRACT FROM AUTHOR]

Abstract Covalently-terminated germanane GeH and GeCH 3 for hydrogen generation from catalytic hydrolysis of ammonia borane (NH 3 BH 3) complex under visible light (λ ≥ 420 nm) has been achieved. Compared with H-terminated germanane GeH, the methyl-terminated germanane GeCH 3 exhibits superior catalytic activity and hydrogen selectivity towards hydrolysis of NH 3 BH 3 , with the turnover frequency (TOF) value of 18.16 mol H2 •min−1•mol cat −1, which is nearly 2.4 times higher than that of GeH. In addition, we have demonstrated their good reusability and high stability through cyclic experiments. A proposed mechanism for the H 2 evolution from hydrolysis of NH 3 BH 3 over GeCH 3 sample is proposed. Graphical abstract Unlabelled Image Highlights • GeH and GeCH 3 were obtained by the topotactic deintercalation. • GeCH 3 shows superior catalytic activity towards hydrolysis of NH 3 BH 3. • The H 2 evolution from GeCH 3 is most likely driven by photogenerated holes. [ABSTRACT FROM AUTHOR]

Recent studies have shown that two-dimensional (2D) materials, such as siloxene and germanane, as electrode in alkali metal ion batteries can lead to excellent performance. The improved electrochemical behavior of these 2D active materials could be due to the limited volume change during charge and discharge, based on an intercalation rather than an alloying mechanism. In addition, if Si is effective in reducing costs due to its low price and abundant resource reserves, its conductivity is low, while Ge can provide higher electronic conductivity than Si, but is more expensive. In this respect, in order to integrate their cheapness and excellent conductivity, we propose a series of layered materials (named siliganes, i.e. , Si 1-x Ge x , 0.1 ⩽ x ⩽ 0.9), which consist of 2D Si-Ge composites. Through a simple method, the Ca2+ cations were completely removed from the precursor Ca(Si 1-x Ge x) 2 , and the lamellar siliganes were obtained. The layered materials were tested in Na- and K- ion batteries. Based on the better electrochemical performance, we identified siligane_Si 0.1 Ge 0.9 as the best candidate. At a current density of 0.05 A g−1, its reversible capacities of the Na ion and K ion cells were 276 mAh g−1 and 132 mAh g−1 after 50 cycles, respectively. [ABSTRACT FROM AUTHOR]

The electronic properties and geometric stability of germanane nanosheet is explored using first-principle studies. The germanane nanosheet exhibits semiconducting properties and stability of germanane sheet is ensured with formation energy. The adsorption behavior of deoxyribo nucleic acid (DNA)/ribo nucleic acid (RNA) nucleobases on monolayer germanane nanosheet have been investigated using density functional theory with van der Waals dispersion correction. The adsorption of nucleobases is found to be physisorbed on germanane nanosheet with the van der Waals type of interaction. The order of adsorption of nucleobases with germanane nanosheet is known to be C > G > A > T > U. We observed the changes in the energy band structure and the density of states variation due to the adsorption of nucleobases on germanane nanosheet. Our results confirm that apart from graphene, germanane monolayer can be used to detect nucleotides in the field of biotechnology and medical science. [ABSTRACT FROM AUTHOR]

Ballistic transport in monolayer Germanane MOSFETs is investigated for high-performance (HP) applications. Characteristics of both n- and p-type transistors having channel lengths of 7, 5, and 3 nm are studied and compared against the International Technology Roadmap for Semiconductor (ITRS) target of 2028. Our simulation approach is based on a self-consistent quantum ballistic transport model within the framework of the nonequilibrium Green's function formalism and relies on a single-band and a two-band k · p Hamiltonian for n- and p-type channels, respectively. We found that, even for a gate length scaled down to 3 nm, the ON current (ION) in n- and p-MOSFETs for a fixed OFF current IOFF = 100 nA/µm is as high as ~890 and 700 µA/µm, respectively. For longer channel lengths, the p-MOSFET can outperform the n-MOSFET in terms of ION requirements, as the direct source-to-drain tunneling gets suppressed. Other performance metrics, including gate capacitance, intrinsic switching delay, and switching energy, have also been calculated and found to be comparable to the ITRS 2028 HP technology requirements. [ABSTRACT FROM AUTHOR]

The structural stability and electronic properties of pristine and Ga substituted germanane nanosheet were investigated using the density functional theory technique. The stability of bare and Ga substituted germanane nanosheet is substantiated with formation energy. The energy band gap opens upon hydrogenation on germanene sheet, which is utilized as a sensor material for the detection of NH 3 and H 2 O molecules. The interaction of ammonia and humidity on germanane nanosheet is explored using the projected density of states, Bader charge transfer, adsorption energy, average energy gap variation, energy gap and electron density. The interaction of H 2 O and NH 3 gas molecules on germanane material is studied in atomistic level. The interaction of humidity on pristine germanane nanosheet and NH 3 on Ga substituted germanane nanosheet is found to be more favorable. The findings recommend that germanane nanosheet can be utilized as a chemi-resistor for the detection of humidity and trace levels of ammonia gas in the environment. [ABSTRACT FROM AUTHOR]

Using self-consistent atomistic quantum transport simulations, the device characteristics of n-type and p-type germanane (GeH) field-effect transistors (FETs) are evaluated. While both devices exhibit near-identical off-state characteristics, n-type GeH FET shows ~40% larger on current than the p-type counterpart, resulting in faster switching speed and lower power-delay product. Our benchmark of GeH FETs against similar devices based on 2D materials reveals that GeH outperforms MoS2 and black phosphorus in terms of energy-delay product (EDP). In addition, the performance of GeH-based CMOS circuit is analyzed using an inverter chain. By engineering power supply voltage and threshold voltage simultaneously, we find the optimal operating condition of GeH FETs, minimizing EDP in the CMOS circuit. Our comprehensive study, including material parameterization, device simulation, and circuit analyses, demonstrates significant potential of GeH FETs for 2D-material CMOS circuit applications. [ABSTRACT FROM AUTHOR]

Realizing a germanane (GeH) film on insulating substrates is strongly required to understand its intrinsic electric properties in discussing the potential applications for the next-generation field-effect transistor channels. This study investigates the heteroepitaxial growth of CaGe 2 —the precursor of the GeH—films on a high resistive substrate of FZ-Si(111) using a molecular beam epitaxy with the deposition temperature (T depo) as a variable. X-ray diffraction and Raman spectroscopy analyses indicated that a metastable polytype of 2H was dominated in the epitaxial CaGe 2 films; the T depo must be less than 700 °C to prevent Si diffusion from the substrates. We also synthesize GeH films by immersing some CaGe 2 films in HCl acid solutions at a low temperature of −40 °C. Although the obtained grain size of GeH was still as small as several hundred nanometers, we believe that the present study is the first step in obtaining the GeH continuous films directly on insulators necessary for electrical characterizations. [ABSTRACT FROM AUTHOR]

Germanane, a two-dimensional Ge lattice in which each atom is hydrogen-terminated in the z-direction, possesses a remarkable combination of electronic and optical properties that are attractive for applications ranging from chemical sensing to electrocatalysis and photocatalysis. In this work, we studied germanane (GeH) and the novel butyl-functionalized germanane (GeBu x H (1−x)) as photocatalysts for water purification under visible light irradiation and utilizing challenging conditions in terms of photocatalyst loading (1 mg per g of aqueous solution containing 200 ppm of pollutant). The synthesized GeH and GeBu x H (1−x) have significantly higher specific surface area (121 m2 g−1 and 76 m2 g−1, respectively) than other germanane derivatives reported to date and display optical band gaps suitable for visible light absorption (1.40 eV and 1.55 eV, respectively). In terms of photocatalytic performance, GeH displayed the best activity in the degradation of rhodamine B (61% removal after 3 h under visible radiation), while GeBu x H (1−x) proved to be the best photocatalyst for the degradation of phenol (33% removal after 3 h under visible radiation). In both cases, the activity under visible radiation surpassed that of P25 TiO 2 and could be enhanced significantly by sonication in water before interaction with the pollutants. Recycling tests showed that GeH could be reused with no or negligible loss of photocatalytic activity, whereas GeBu x H (1−x) showed a minor decrease in activity upon reuse. [Display omitted] • Germanane (GeH) and its novel butylated derivative (GeBu x H (1−x)) were prepared by means of facile synthetic approaches. • GeH (121 m2 g-1) and GeBu x H (1‑x) (76 m2 g-1) showed enhanced specific surface areas compared with previously reported germananes. • GeH and GeBu x H (1−x) exhibited high photocatalytic activity in the degradation of rhodamine B and phenol under visible light. • Sonication pretreatment improved dramatically the photocatalytic activity of the germananes. • The GeH photocatalyst was recycled with negligible loss of activity. [ABSTRACT FROM AUTHOR]

The electronic properties and structural stability of germanane nanosheet is studied using density functional theory method. The stability of germanane sheet is confirmed with formation energy. The band gap opens upon hydrogenation of germanene sheet, which is used as a base material for the detection of alcohol/aldehyde molecules. The adsorption of alcohol/aldehyde molecules on germanane nanosheet is studied using charge transfer, density of states spectrum, energy gap, adsorption energy, electron density and average energy gap variation. The adsorption of alcohol/aldehyde molecules on germanane nanosheet is explored in atomistic level. The adsorption of alcohol is found to be more favorable than aldehyde molecules on germanane nanosheet. The findings suggest that germanane nanosheet can be used as chemiresistor for detection of alcohol/aldehyde vapors in the atmosphere. [ABSTRACT FROM AUTHOR]

Here we explore the performance limit of monolayer germanane (GeH) field-effect transistors (FETs). We first plotted an electronic band structure of GeH using density functional theory and then tight-binding parameters were extracted. Device characteristics of GeH FETs are investigated using rigorous self-consistent atomistic quantum transport simulations within tight-binding approximations. Our simulation results indicate that GeH FETs can exhibit exceptional on-state device characteristics, such as high \textI\textit {on} (>2 mA/ \mu \textm ) and large \textgm (~7 mS/ \mu \textm ) with \textV\textit {DD} = 0.5 V due to the very light effective mass of GeH (0.07m0), while maintaining excellent switching characteristics (SS ~64 mV/dec). We have also performed a scaling study by varying the channel length, and it turned out that GeH FET can be scaled down to ~14-nm channel without facing significant short channel effects but it may suffer from large leakage current at the channel length shorter than 10 nm. Finally, we have benchmarked GeH FET against MoS2 counterpart, exhibiting better suitability of GeH device for high-performance applications compared with MoS2 transistors. [ABSTRACT FROM AUTHOR]

In the present work, we deployed a novel orthorhombic germanane nanosheet (ortho-GeNS) as a sensing material to detect camphene and eucalyptol molecules, the indoor air pollutants in the ambient environment. In the beginning, the structural and dynamical permanency of ortho-GeNS is confirmed with cohesive energy (− 4.164 e V / a t o m) and phonon-band maps. Successively, the electronic features of ortho-GeNS are conferred using band structure along with the projected density of states maps. The energy gap of ortho-GeNS at the hybrid GGA/B3LYP level of theory is computed to be 3.948 eV. Mainly, the adsorption properties of terpinene molecules, namely camphene and eucalyptol on ortho-GeNS are investigated via ascertaining adsorption energy, Mulliken population analysis, and relative band gap variations. Besides, the scope of adsorption energy values (− 0.405 e V t o − 0.669 e V) exemplifies that the target molecules are physisorbed on ortho-GeNS. Overall results suggested that the ortho-GeNS can be deployed as a worthy chemiresistive sensor to sense indoor air pollutants for monitoring indoor air quality. [Display omitted] • The orthorhombic germanane nanosheet (ortho-GeNS) exhibits band gap of 3.948 eV. • The terpinene molecules, namely camphene and eucalyptol are physisorbed on ortho-GeNS. • The electronic properties of ortho-GeNS changes owing to adsorption of camphene and eucalyptol. • The ortho-GeNS can be used for detection of camphene and eucalyptol molecules. [ABSTRACT FROM AUTHOR]

Using density functional theory in conjunction with many-body perturbation theory, we theoretically investigated the electronic structures of monolayers germanane and silicane in an applied out-of-plane uniform electric field. Our results show that although the band structures of both monolayers are affected by the electric field, the band gap width cannot be reduced to zero even for high field-strengths. Moreover, excitons are shown to be robust under electric fields, so that Stark shifts for the fundamental exciton peak is only of the order of a few meV for fields of 1 V Å -1 . The electric field has also no significant effect on electron probability distribution, as the exciton dissociation into free electron-hole pairs is not observed even at high electric field strengths. Franz-Keldysh effect is also studied in monolayers germanane and silicane. We found that, due to the shielding effect, the external field is prevented to induce absorption in the spectral region below the gap and only above-gap oscillatory spectral features are allowed. One can benefit from such a characteristic where the absorption near the band edge is not altered by the presence of an electric field, especially since these materials have excitonic peaks in the visible range., (© 2023 IOP Publishing Ltd.)

We report the ultimate performance of a double-gate ultrathin body (DG-UTB) FET employing materials from group IV, III-V, and 2-D materials based on International Technology Roadmap for Semiconductors (ITRS) projected specifications for high-performance (HP) and low-power (LP) technologies. The band structures of the channel materials were obtained using the sp ^3\textd^5\texts^\ast tight binding model and the first-principles density functional theory. The ballistic performance of FETs designed based on the ITRS specifications for 2018 and beyond was evaluated via the semiclassical ballistic transport model. The leakage current due to direct source-to-drain tunneling was calculated based on Wentzel–Kramers–Brillouin approximation. For nFET used in the HP technology, GaSb nFET has the best voltage scalability followed by Ge nFET in 2026. It was found that I\mathrm{\scriptscriptstyle ON} of InAs and In0.3 Ga0.7Sb nFETs is among the lowest, and they require larger power supply voltage ( V\mathrm{DD} ) among III-V semiconductors considered to achieve I\mathrm{\scriptscriptstyle ON} of silicon nFET. However, they show lower power delay product (PDP) due to their smaller electron effective mass, resulting in higher carrier velocity. Ge pFET offers the best voltage scalability for pFET used in the HP technology. For the voltage scalability assessment based on the requirements for the LP technology, MOSFETs based on Si offer better performance in terms of I\mathrm{\scriptscriptstyle ON} and PDP than MOSFETs based on 2-D materials. Among the 2-D materials studied, black phosphorus and silicane MOSFETs exhibit higher I\mathrm{\scriptscriptstyle ON} and better voltage scalability and PDP. [ABSTRACT FROM AUTHOR]