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We demonstrate selective area epitaxy of GaAs films using patterned graphene masks on a Ge (001) substrate. GaAs selectively grows on exposed regions of the Ge substrate for graphene stripe widths of 10 μm. The selectivity is highly dependent on the growth temperature and annealing time, which we explain in terms of temperature dependent sticking coefficients and surface diffusion. The high nucleation selectivity over several micrometers sets constraints on experimental realizations of remote epitaxy. [ABSTRACT FROM AUTHOR]

Pure Se glass and ternary AxBySe1−x−y glasses where A = Ge and B = P or As, in the low mean coordination number, ⟨r⟩, range of 2.00 < ⟨r⟩ < 2.12 display a 3‐ to 5‐fold reduction in the width of the glass transition when aged at room temperature over 4–8 months. Group IV (Ge) and group V (P, As) additives serve to crosslink the base Se glass polymeric chains, Sen, with n > 250 atoms and to reduce the length "n" between cross‐link points as x and y are increased. Herein, it is shown that in such weakly crosslinked glasses, the continued narrowing of the glass transition width Tg by a factor of 3–5, as in pure Se, stems from the fact that polymeric Sen chain segments between the crosslink points continue to have a length n of at least eight atoms or more. Such polymeric Sen chains are super‐flexible and reconstruct with each, as in pure Se, promoting structural ordering responsible for Tg narrowing. When n < 8, super flexibility is steadily lost. Along with the flexible, intermediate, and stressed‐rigid phases, a new super‐flexible phase of Se and Se‐rich glasses is obtained. [ABSTRACT FROM AUTHOR]

Polycrystalline Ge thin films are promising candidates for next‐generation thin‐film transistors. However, the difficulty in Fermi‐level control due to the high density of defect‐induced acceptors has been one of the main problems for device applications. Herein, GeO2 preparation and Sn addition are combined in the advanced low‐temperature (375 °C) solid‐phase crystallization of Ge layers that have been recently developed. The GeO2 underlayer works effectively at a low Sn composition (< 4%), enlarging the grain size by a magnification of ≈5. An appropriate amount of unsubstituted Sn reduces acceptor defects and achieves a minimum hole concentration of 3 × 1016 cm−3 by combining post‐annealing (500 °C). This hole concentration is the lowest level for undoped polycrystalline Ge‐based thin films, which allows control over their Fermi level widely by impurity doping. Although the lower hole concentration provides a higher energy barrier height of the grain boundary, the hole mobility is maintained at 190 cm2 V−1 s−1 owing to the large grains (15 μm diameter). This achievement paves the way for the implementation of poly‐Ge‐based thin films in various semiconductor devices, including advanced thin‐film transistors. [ABSTRACT FROM AUTHOR]

The structure of amorphous Ge (a-Ge) films prepared by sputter-deposition and the effects of aging at ambient temperature and pressure were studied by pair-distribution-function (PDF) analysis from electron scattering and molecular dynamics simulations. The PDFs of the as-deposited and aged samples for 3-13 months showed that the major peaks for Ge-Ge bonds decrease in intensity and broaden with aging for up to 7 months. In the PDFs of a-Ge of molecular dynamics simulation obtained by quenching liquid at different rates, the major peak intensities of a slowly cooled model are higher than those of a rapidly cooled model. Analyses on short- and medium-range configurations show that the slowly cooled model includes a certain amount of medium-range ordered (MRO) clusters, while the rapidly cooled model includes liquid-like configurations rather than MRO clusters. The similarity between experimental and computational PDFs implies that as-deposited films are similar in structure to the slowly cooled model, whereas the fully aged films are similar to the rapidly cooled model. It is assumed that as they undergo room-temperature aging, the MRO clusters disintegrate and transform into liquid-like regions in the same matrix. This transition in local configurations is discussed in terms of instability and the non-equilibrium of nanoclusters produced by a vapor-deposition process. [ABSTRACT FROM AUTHOR]

The making of BaZrS3 thin films by molecular beam epitaxy (MBE) is demonstrated. BaZrS3 forms in the orthorhombic distorted‐perovskite structure with corner‐sharing ZrS6 octahedra. The single‐step MBE process results in films smooth on the atomic scale, with near‐perfect BaZrS3 stoichiometry and an atomically sharp interface with the LaAlO3 substrate. The films grow epitaxially via two competing growth modes: buffered epitaxy, with a self‐assembled interface layer that relieves the epitaxial strain, and direct epitaxy, with rotated‐cube‐on‐cube growth that accommodates the large lattice constant mismatch between the oxide and the sulfide perovskites. This work sets the stage for developing chalcogenide perovskites as a family of semiconductor alloys with properties that can be tuned with strain and composition in high‐quality epitaxial thin films, as has been long‐established for other systems including Si‐Ge, III‐Vs, and II‐VIs. The methods demonstrated here also represent a revival of gas‐source chalcogenide MBE. [ABSTRACT FROM AUTHOR]

The Mn3X (where X = Ga, Ge, Sn, etc.) compounds have appealing prospects for spintronic applications due to their various crystal structures and magnetic properties for the design of reliable high-density memories. However, controlled growth of high-quality Mn3X thin films remains challenging in material science. Here, we reported the controlled film growth of Heusler alloy Mn3Ge, which could crystallize in respective tetragonal and hexagonal structures. The tetragonal D022-type Mn3Ge film exhibits strong perpendicular ferromagnetic anisotropy, while the hexagonal D019-type Mn3Ge film indicates non-collinear triangular antiferromagnetic order. From our experimental observations of structure characterizations, magnetic properties, anomalous Hall effect, and magnetoresistance measurements, we realized the manipulation of spin orientations and topological features. Majority/minority spin polarized Fermi surface and density of states of both tetragonal and hexagonal Mn3Ge structures were investigated by density functional theory calculations. Our work not only opens up technology routes toward the development of Mn3X-based devices for applications in topological spintronics and spin-torque memories but also leads to engineer the physical properties for fundamental study. [ABSTRACT FROM AUTHOR]

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Relaxed GeSn films with a high Sn content (>13%) were grown on Ge (100) substrates via magnetron sputtering epitaxy through a component-grade GeSn buffer layer structure. Raman spectroscopy, high-resolution x-ray diffraction, and cross-sectional transmission electron microscopy revealed that Ge0.861Sn0.139 alloys, with a degree of strain relaxation of up to 96.1%, can be achieved through a component-grade buffer layer structure. The threading dislocation density was estimated to be around 2×108 cm−2. The atomic surface flatness of the GeSn alloys was confirmed by atomic force microscopy, and the surface roughness was observed to be below 1 nm. Moreover, the thermal stability of GeSn samples was investigated. The results indicated that the component-grade structure is effective for realizing a high Sn composition and high relaxation of the GeSn alloy. [ABSTRACT FROM AUTHOR]

Monatomic zero-valent silicon and germanium complexes (silylones and germylones), stabilised by neutral donating ligands, emerged only recently as a new class of low-valent group 14 element compounds. Featuring four valence electrons in the form of two lone pairs at a single site, silylones and germylones represent a molecular resting state of single Si and Ge atoms, which are typically only observed at high temperature in the gas phase or in interstellar matter. These species are capable of transferring single Si and Ge atoms to unsaturated substrates and acting as building blocks for novel group 14 species. After introducing this type of compound and the examples known to date, this feature article highlights some chelating bis N-heterocyclic carbene (bis(NHC)) and bis N-heterocyclic silylene (bis(NHSi)) supported Si0 and Ge0 complexes, for which a range of unprecedented reactivity has been discovered. The characteristic behaviour of these silylones and germylones discussed here consists of (i) coordination to Lewis acids, (ii) oxidation with elemental chalcogens, (iii) bond activation of common organic substrates and inert small molecules; and (iv) homocoupling of the Si0 and Ge0 centres. This wealth of reactivity has opened the door to a series of Si and Ge compounds, which would be otherwise difficult to realise. [ABSTRACT FROM AUTHOR]

We have investigated the structural and local atomic properties of Ge nanocrystals (Ge-ncs) embedded ZnO (ZnO: Ge) thin films. The films were deposited by sequential sputtering of ZnO and Ge thin film layers on z-cut quartz substrates followed by an ex-situ rapid thermal annealing (RTA) at 600 °C for 30, 60, and 90 s under forming gas atmosphere. Effects of RTA time on the evolution of Ge-ncs were investigated by x-ray diffraction (XRD), scanning electron microscopy (SEM), hard x-ray photoelectron spectroscopy (HAXPES), and extended x-ray absorption fine structure (EXAFS). XRD patterns have clearly shown that fcc diamond phase Ge-ncs of sizes ranging between 18 and 27 nm are formed upon RTA and no Ge-oxide peak has been detected. However, cross-section SEM images have clearly revealed that after RTA process, Ge layers form varying size nanoclusters composed of Ge-ncs regions. EXAFS performed at the Ge K-edge to probe the local atomic structure of the Ge-ncs has revealed that as prepared ZnO:Ge possesses Geoxide but subsequent RTA leads to crystalline Ge structure without the oxide layer. In order to study the occupied electronic structure, HAXPES has been utilized. The peak separation between the Zn 2p and Ge 3d shows no significant change due to RTA. This implies little change in the valence band offset due to RTA. [ABSTRACT FROM AUTHOR]

The high potential of polycrystalline Ge as a thin-film thermoelectric material was demonstrated. We synthesize a polycrystalline Ge layer on an insulating substrate at 450 °C via advanced solid-phase crystallization and control its carrier concentration through the solid-phase diffusion of various p- and n-type dopants. The heating deposition (150 °C) of the amorphous precursor considerably improves the crystal quality of the polycrystalline Ge layer as well as the doping properties. The solid-phase diffusion of Ga and P dopants onto the Ge layers allows for control of the carrier concentration in the ranges of 1017–1020 cm−3 for p-type and 1018–1019 cm−3 for n-type, respectively, by modulating the diffusion annealing temperature and time. Because of the high electrical conductivities reflecting the carrier mobilities and carrier concentrations, the maximum power factors reach a value of 1080 μW m−1 K−2 for p-type and 2300 μW m−1 K−2 for n-type at room temperature. These power factors are higher than those of most polycrystalline semiconductor thin films formed at temperatures below 1000 °C. Therefore, this study serves as a milestone toward high-performance and reliable thin-film thermoelectric generators based on an environmentally friendly semiconductor. [ABSTRACT FROM AUTHOR]

The development of three-dimensional architectures in semiconductor technology is paving the way to new device concepts for various applications, from quantum computing to single photon avalanche detectors. In most cases, such structures are achievable only under far-from-equilibrium growth conditions. Controlling the shape and morphology of the growing structures, to meet the strict requirements for an application, is far more complex than in close-to-equilibrium cases. The development of predictive simulation tools can be essential to guide the experiments. A versatile phase-field model for kinetic crystal growth is presented and applied to the prototypical case of Ge/Si vertical microcrystals grown on deeply patterned Si substrates. These structures, under development for innovative optoelectronic applications, are characterized by a complex three-dimensional set of facets essentially driven by facet competition. First, the parameters describing the kinetics on the surface of Si and Ge are fitted on a small set of experimental results. To this goal, Si vertical microcrystals have been grown, while for Ge the fitting parameters have been obtained from data from the literature. Once calibrated, the predictive capabilities of the model are demonstrated and exploited for investigating new pattern geometries and crystal morphologies, offering a guideline for the design of new 3D heterostructures. The reported methodology is intended to be a general approach for investigating faceted growth under far-from-equilibrium conditions. [ABSTRACT FROM AUTHOR]

In this paper, we report the amorphous Ge NPs film which is fabricated at room-temperature by PECVD method. The uniform, compact and smooth film is formed by orderly packing of the Ge NPs in the longitudinal direction, resulting in the formation of columnar structures in the Ge NPs film. The electrical, optical properties and energy levels of the Ge NPs film meet the requirements of the OSCs for ETL, and the PTB7:PC 70 BM OSCs with the Ge NPs ETL shows the PCE of 7.38%. [Display omitted] • The amorphous Ge NPs film is fabricated by using the PECVD method at room temperature. • The compact and orderly packing of the NPs in the longitudinal direction leads to the formation of columnar structures in the Ge NPs film. • The electrical, optical properties and energy levels of the Ge NPs film meet the requirements of the OSCs for ETL. • The PTB7:PC 70 BM OSCs with the Ge NPs ETL shows the PCE of 7.38%. The performances of the organic solar cells (OSCs) largely depends on the selection and preparation of the electron transport layer (ETL). In this paper, the uniform and compact Ge nanoparticles (NPs) film was fabricated by using the plasma enhanced chemical vapor deposition (PECVD) method at room temperature. The Ge NPs film is formed by close packing of amorphous Ge particles with an average diameter of 6.05 nm, and the film shows a fairly smooth surface with a root-mean-square (RMS) roughness of 0.6419 nm. The results shows that Ge NPs film exhibits n-type characteristics, and the longitudinal conductivity of the film is 1.90 × 10−5 S/cm, which is better than that of the ZnO NPs film. The excellent longitudinal charge transport characteristics is attributed to the existence of the columnar structures in the Ge NPs. In addition, the Ge NPs film shows a visible light transmittance comparable to that of the ZnO NPs film. More importantly, the energy levels of the Ge NPs film meets the requirements of the PTB7:PC 70 BM OSCs for the ETL, and the devices with the Ge NPs ETL shows the power conversion efficiency (PCE) of 7.38%. The characteristic of room temperature preparation make the Ge NPs ETL may become a reliable choice for the flexible devices in the near future. [ABSTRACT FROM AUTHOR]

Se85.26Ge12.92Cd1.81 thin films were prepared using glass and fluorine tin oxide FTO substrates by the technique of thermal evaporation. Structure was performed using X-ray diffraction pattern and the energy dispersive X-ray analysis EDX. The optical properties of Se85.26Ge12.92Cd1.81 thin films are investigated by spectrophotometric measure of transmission, reflectance and absorbance at normal incidence of light in the wavelength range 300–2500 nm. There are two types of optical transition direct and indirect allowed for both films deposited on to glass and FTO substrates. Values of both absorption index (k) and the refractive index (n) are calculated. The energy gap value Egopt for Se85.26Ge12.92Cd1.81 films deposited on FTO substrates found to be smaller than its value for films deposited on to glass substrates. The optical dispersion parameters, E0, Ed, n(0), λ0, S0 and n∞2 were also determined and discussed. [ABSTRACT FROM AUTHOR]

We investigate the glass transition and crystallization of Ge2Sb2Te5 by nanocalorimetry on 32–57 nm layers at temperature scanning rates ranging from 23 to 184 kK/s. Crystallization follows the Arrhenius behavior observed at low heating rates, with an activation energy of 2.7 ± 0.1 eV. The crystal-growth velocity (>500 µm/s at 500 K) confirms fast values found in earlier work and by ab initio molecular dynamics simulations. These experiments also outline the importance of carrying out ultra-fast scanning calorimetry studies with samples in excellent thermal contact with the heating device. [ABSTRACT FROM AUTHOR]

The Er-doped Ge 1 − x Sn x thin films with different Sn contents were prepared on Ge buffered Si substrates by thermal evaporation. The effect of Er doping on the crystallization of Ge 1 − x Sn x films at different annealing temperatures was studied. It is demonstrated that Er doping can increase the critical crystallization temperature and greatly reduce the surface roughness of high temperature annealed Ge 1 − x Sn x thin films. [ABSTRACT FROM AUTHOR]

The deformation of the interatomic bonds in the upper atomic layers of the Ge(111) surface with c(2 × 8), 7 × 7, and 5 × 5 structures is studied using ab initio calculations. The calculations are performed in terms of the density functional theory for both the relaxed and elastically compressed Ge(111) surfaces. Bond tension deformation is shown to occur in the upper layer of the Ge(111) surface with the 7 × 7 and 5 × 5 structures up to 4% lattice compression. The bond deformation on the 5 × 5 surface is higher than that on the 7 × 7 surface, which is caused by higher average deformation of dimers in the 5 × 5 structure. Our results can be used to correctly interpret the experimental data obtained during the wetting layer formation in the course of Ge/Si(111) growth. [ABSTRACT FROM AUTHOR]

Polycarbonate (PC) substrates were exposed to plasma environments consisting of a 50:50 mixture of oxygen and argon, and were subsequently coated with germanium (Ge) films grown via sputtering. The hydrophilicity of the PC surfaces was tailored by ion bombardment with energy levels ranging from 50 to 300 eV, which led to a reduction in water contact angles from a native 80° to a superhydrophilic state. Analyses of chemical composition and structure of the PC were performed using X-ray Spectroscopy (XPS) and Fourier Transform Infrared Spectroscopy in Attenuated Total Reflectance geometry (FTIR-ATR), and then correlated to the adhesion of the Ge thin films. Optimal adhesion of the Ge films was achieved by bombarding the PC with ions at energies between 100 and 200 eV, activating the polymer surface while avoiding photodegradation as confirmed by chemical analysis. We report an efficient method for achieving superhydrophilicity of PC within a short treatment time of 60 s that can be effectively integrated in diverse vacuum applications. • Rapid method to achieve superhydrophilic polycarbonate via controlled ion bombardment in an oxygen/argon plasma environment. • Enhanced adhesion of sputtered Ge films on PC confirmed via ion bombardment control in oxygen/argon plasma environments. • Superhydrophilicity as a potential marker to anticipate the interplay between functionalization and photodegradation of plasma-treated PC substrates, prior to Ge film deposition. [ABSTRACT FROM AUTHOR]

We advance a theory for the nanoscale patterns that emerge spontaneously when the (001) surface of a crystal is bombarded with a broad ion beam and the crystal structure remains intact. Both normal incidence bombardment and oblique incidence bombardment with concurrent sample rotation are studied. For suitable parameter choices, our equation of motion produces patterns that are remarkably similar to recently-discovered transitional patterns on the (001) surface of germanium, to the patterns of inverted square pyramids that form on the (001) surface of silicon, and to the various patterns produced by oblique incidence bombardment of a rotating Ge (001) surface. A novel term that comes from curvature dependent sputtering is responsible for the isolated peaks present in the transitional patterns. [ABSTRACT FROM AUTHOR]

Structural and magnetic properties of Mn 5 (Si x Ge 1-x) 3 thin films were investigated. Ferromagnetic Mn 5 Ge 3 and anti-ferromagnetic Mn 5 Si 3 thin films have been synthesized and characterized as these compounds exhibit interesting features for the development of spintronics. Here, Mn 5 (Si x Ge 1-x) 3 thin films were grown on Ge(111) substrates by co-deposition using molecular beam epitaxy. Crystalline thin films can be produced with controlled Si concentrations ranging from 0 to 1. The thin films were relaxed by dislocations at the interface with the substrate. A lattice parameter variation was observed as the Si content increased, which is comparable to previous works done in bulk. Reflection high-energy electron diffraction diagrams and X-ray diffraction profiles showed that lattice parameters a and c are shrinking and that the surface roughness and crystallinity degrade as the Si amount increases. Magnetometric measurements revealed a ferromagnetic behavior for all Si concentrations. The measured average ferromagnetic moment per manganese atom decreased from 2.33 to 0.05 μ B /Mn atom. No ferro to anti-ferromagnetic transition was observed contrary to the bulk Mn 5 (Si x Ge 1-x) 3 compound. • Mn 5 (Si x Ge 1-x) 3 thin films are epitaxially grown on Ge(111) by molecular beam epitaxy. • Mn 5 (Si x Ge 1-x) 3 films with a Si concentration up to x = 0.6 are synthesized. • Si concentration and the structural and magnetic properties are correlated. [ABSTRACT FROM AUTHOR]

• A novel PSC is proposed by stacking Ge and perovskite films and embedded Ge NPs. • The maximum Jsc is predicted to 45.72 mA/cm2, 2.55 times higher than flat reference. • The improvements attribute to complementary absorption and LSPR associated effects. By taking advantage of the complementary absorption effect of germanium (Ge) and perovskite, a novel perovskite solar cell (PSC) was proposed by stacking Ge and perovskite thin films to serve as the dual absorption layer. Its absorption spectra and photocurrent were calculated and optimized as a function of the thickness of Ge film by finite element method (FEM). Then, the optical efficiency was further boosted by embedding an array of Ge semi-ellipsoidal nanoparticles within the perovskite film. The predicted maximum photocurrent is revealed to reach 45.72 mA/cm2, which is 2.55 times larger than that of planar referenced PSC. Besides the complementary absorption effect, the localized surface plasmon resonance (LSPR) of Ge nanoparticles and the grating effects of Ge nanoparticle array are revealed to contribute to the obtained Jsc improvement. The present work is insightful for future design and applications of PSCs by introducing Ge thin film and Ge nanoparticles. [ABSTRACT FROM AUTHOR]

• New sterically bulky aryl and aliphatic substituted diamide ligands have been reported. • A series of novel germylenes were prepared and their steric profile assessed using computational models. • The extremely bulky 2,4,6-tricyclohexylphenyl substituent provides greater steric protection to the germanium centre, compared to previously reported germylenes incorporating smaller aryl groups, utilising the same ligand back-bone architectures. In this contribution, three novel diamine pro-ligands, incorporating sterically bulky aryl and aliphatic N-substituents, have been developed; viz. (NCNTCHP)H 2 (NCNTCHP = {(TCHP)NCH 2 } 2 CH 2 , TCHP = 2,4,6-tricyclohexylphenyl), (NONTCHP)H 2 (NONTCHP = {(TCHP)NSiMe 2 } 2 O), and (NONAd)H 2 (NONAd = {(Ad)NSiMe 2 } 2 O; Ad = 1-adamantyl). Through salt metathesis or transamination synthetic approaches, the N-heterocyclic germylenes, [:Ge(NCNTCHP)], [:Ge(NONTCHP)], and [:Ge(NONAd)], have been prepared and crystallographically characterized. The electronic structure of each germylene was studied by DFT calculations. The steric profile of the germanium-bound ligands was also assessed using computational models, and the results compared to those for structurally similar compounds. Significant steric crowding of the germanium centre (>70 % ligand coverage) was observed for [:Ge(NCNTCHP)] and [:Ge(NONTCHP)], while [:Ge(NONAd)] exhibited substantially less steric saturation at the metal centre (∼62 % ligand coverage). Through these studies, we have shown the potential suitably of the developed ligands to stabilise other low-valent main-group species. Synopsis: A range of very bulky 6-membered heterocyclic diamido germylenes were synthesised and their structures investigated using X-ray crystallography and computational methods. [Display omitted] [ABSTRACT FROM AUTHOR]

Highly chemoselective hydroelementation of diverse terminal alkenes catalyzed by readily available platinum complexes bearing P,N-donor ligands is reported. The developed approach enables comprehensive incorporation of silyl-, germyl-, and boryl-moieties at remarkably low catalyst concentrations. Consequently, 47 products were efficiently synthesized, showcasing exclusive modification of terminal C=C moieties in the presence of various sensitive groups, e.g. internal C C, C O, or O H. [Display omitted] • Novel Pt(II) complexes with easily accessible bidentate P,N-donor ligands. • High catalytic activity in diverse hydroelementations. • Exclusive modification of terminal C C bonds in multifunctional compounds. • Reusable catalyst maintains activity and chemoselectivity over multiple cycles. • Applicability to various synthetic domains, including natural products and POSS. In this report, we present the synthesis of six novel neutral platinum complexes employing readily available P,N-donor ligands through a straightforward two-step procedure. Subsequently, we investigated their catalytic activity in the hydroelementation of terminal olefins, highlighting their versatile utility in material and natural product chemistry. The efficient addition of silicon, germanium, and boron hydrides to the C C bond at low catalyst loading occurred exclusively in an anti-Markovnikov manner. Furthermore, our substrate scope encompasses a wide range of aliphatic and aromatic alkenes, featuring substituents with varying electronic properties. In contrast to many previous Pt-complexes, our catalytic system displayed exceptional chemoselectivity towards other unsaturated functional groups, such as carbonyl and internal C C bonds. Notably, it also exhibited remarkable tolerance to hydroxyl, alkoxyl, silyl, and thioether moieties. Additionally, we accentuated the prowess of our catalyst, showcasing its capability to sustain consistent activity and selectivity throughout numerous catalytic cycles. [ABSTRACT FROM AUTHOR]

In the current study, the density functional theory is utilized to investigate the elastic, plastic and electronic properties of the 2 × 2 and 3 × 3 pristine and transition metal (TM) doped germanene. Different atoms, including V, Co, Fe, Mn, Cr, Ti, Ni and Sc are selected for this purpose. It is shown that doping of the transition metal atoms would result in the reduction of the Young's and bulk moduli of the germanene. In addition, the isotropic behavior of these nanosheets were shown by comparing the Young's moduli of both pristine and doped structures in armchair and zigzag directions. Furthermore, the plastic behavior of these structures were investigated by increasing the applied loading. It was seen that except for the 2 × 2 Co-doped monolayer, the yield strain of both 2 × 2 and 3 × 3 nanosheets were reduced under uniaxial and biaxial loading. In 2 × 2 doped nanosheets under uniaxial loading, the highest reduction occurs for Ti-doped germanene, and in 3 × 3 cases, the highest reduction happens for Co, Ni, Fe and Sc-doped germanene. Electron localization function revealed the ionic nature of the boding between TM atoms and germanium while the density of state indicated that doping of transition metals would change the semi-metallic behavior of germanene to metallic except for Ti-doped structure. The findings provide valuable information for potential applications in nanotechnology, guiding the development of new materials with specific characteristics based on the identified impacts of different transition metals. [ABSTRACT FROM AUTHOR]

In this work, the dewetting process of an amorphous-Ge-based thin film (a-Ge) upon annealing has been studied, highlighting the morphological and structural properties of the dewetted islands. By a combination of in-situ reflection high-energy electron diffraction (RHEED) during low and high-temperature annealing and by electron back scatter diffraction (EBSD), the initial crystallization dynamics of the Ge film has been clarified, and the structural characterization of the dewetted islands has been disclosed by high-resolution transmission electron microscopy (HR-TEM), atomic force microscopy (AFM) and scanning electron microscopy (SEM). Chemical composition has been assessed by electron energy loss spectroscopy (EELS). Different initial a-Ge film thickness (range: 10 nm–200 nm) and annealing treatments, i.e. annealing temperature in the range between 600 °C–820 °C, and annealing time in a 5–120 min range, have been investigated to control the dewetting process. Finally, we extended the solid state dewetting process up to 20 cm wafers showing the possibility to tune particles size varying the initial a-Ge thickness of the deposited film, highlighting the scalability of the process. Beyond fundamental understanding of the a-Ge dewetting process, these results are relevant for the fabrication of large-scale hard masters for nanoimprinting lithography and novel photonic platforms fabricated via a scalable, lithography-free, CMOS-compatible process. [ABSTRACT FROM AUTHOR]

[Display omitted] Density functional theory (DFT) calculations were employed to investigate the adsorption of a single CO molecule on C 21 Ge (named due to the presence of 21 carbon atoms and 1 germanium atom in its structure). The study involved the determination of the most stable geometric structures, adsorption energies, adsorption heights, and density of states for the system, exploring the interactions between the adsorbed CO molecule and the substrate. The results revealed a high degree of CO adsorption on C 21 Ge, with adsorption energies of −1.34 eV and −1.33 eV for C atoms near the adsorption site and O atoms near the adsorption site, respectively. The adsorption distances were determined to be 2.89 Å and 3.04 Å, with the most stable adsorption sites identified as H3 and B3. The adsorption strength was slightly higher when C atoms were in proximity compared to O atoms. The high degree of hybridization between the density of states orbitals indicated strong interactions between the CO molecule and C 21 Ge, emphasizing the pronounced adsorption capability of C 21 Ge for CO. [ABSTRACT FROM AUTHOR]

Ga 2 O 3 is an ultra-wide bandgap semiconductor with various advantages but limited by its low carrier mobility. Utilizing charge separation in heterostructures to improve carrier mobility can be a solution. The narrow bandgap semiconductor Ge with high carrier mobility, potential for the construction of high-quality Ga 2 O 3 /Ge devices. Accordingly, Ga 2 O 3 films were deposited on Ge substrates by atomic layer deposition (ALD) in this study and its performance is characterized. The atomic force microscopy (AFM) of the resulting surface topographies showed atomically smooth appearances with excellent uniformity. The thickness, refractive index, and extinction coefficients of Ga 2 O 3 films measured by ellipsometry revealed unique adsorption properties in the solar-blind wavelength range. The band offset measured by X-ray photoelectron spectroscopy displayed a valence band offset (VBO) of 3.26 ± 0.04 eV and a conduction band offset (CBO) of 0.87 ± 0.03 eV. To calculate the band alignment, a precise and visual XPS depth profile was presented, revealing the microstructures of Ga 2 O 3 /Ge heterojunctions through the etching process. The interfacial charge transfer characteristic was analyzed by Electronic density difference and the Work function calculated by density functional theory (DFT) allowed building carrier immigration mode at the interface of Ga 2 O 3 /Ge heterojunction when combined with the band alignment, providing a high-quality material basis and reference value for high performance optoelectronic and power electronic device design. [Display omitted] ● Abundant experimental and theoretical methods were investigated to study the performance of Ga 2 O 3 /Ge heterojunction about morphology, optical properties, microstructure, band alignment, and charge transfer characteristics. ● The deep etching profile accurately and intuitively shows the composition change from Ga 2 O 3 film to the Ge substrate. ● The interfacial charge transfer characteristics were analyzed by work function and electronic density difference based on DFT. ● The band configurations were depicted to explain the potential of Ga 2 O 3 /Ge heterojunction in optoelectronic applications. [ABSTRACT FROM AUTHOR]

We analyzed the highly siderophile element (HSE) contents and bulk Ge isotopic compositions of large metal grains in the CB chondrites Bencubbin (CBa), Gujba (CBa), and HaH 237 (CBb). Our results suggest that the large grains were formed by the aggregation of smaller condensed grains, and the two Benccubinite groups are distinguishable based on their bulk metal δ74/70Ge mass‐dependent isotopic values of 0.99 ± 0.30‰ (CBa) and −0.65 ± 0.10‰ (CBb). Based on our observations of these three samples, the isotopic compositions of metal in CBa chondrites are best explained by condensation at slow cooling rates in the center of an impact plume, whereas the metal in CBb chondrites formed under fast cooling rates along the plume edges. We also analyzed the Ge contents and isotopic compositions of the core, intermediate, and rim fractions of two Gujba metal grains, which were separated by sequential digestion. These results show a gradual decrease in δ74/70Ge and [Ge] from core to rim. We suggest that these δ74Ge zonations result from near‐equilibrium condensation and evaporation processes in a heterogeneous plume. We propose a model for their formation in which (1) small grains (to become grain cores) condensed at equilibrium; (2) these grains were transported to a warmer region of the plume where they reached temperatures lower than that of Fe‐Ni condensation, but high enough for the rapid evaporation of Ge; (3) Ge evaporation followed by slow cooling enriched the grains in heavy Ge isotopes and the surrounding gas in light Ge isotopes; and (4) equilibrium recondensation of metal from the gas and around the small grains formed the light Ge isotopic zonations observed in grain rims. [ABSTRACT FROM AUTHOR]

We systematically investigate the compositional uniformity, degree of strain relaxation (DSR), defect structure and surface morphology of GeSn epitaxial layers with 16% Sn, grown by low temperature molecular beam epitaxy (MBE) on Ge-buffered Si(001) substrates. Combining atom probe tomography, reciprocal space mapping, cross-sectional transmission electron microscopy, and atomic force microscopy analyses, we demonstrate that for a layer thickness of , a high DSR (∼70%) can be achieved, while maintaining compositional uniformity at the atomic scale. We find no evidence of Sn clustering in the bulk, or Sn segregation to the surface, for at least this value of. The observed compositional uniformity contrasts the well-established phenomenon of strain-relaxation enhancement of Sn content in chemical vapour deposition (CVD) growth of GeSn. The defect structure leading to strain relaxation in these MBE-grown GeSn epitaxial layers is also distinctly different from that observed in CVD growth of the alloy. We observe the co-existence of highly strain-relaxed and pseudomorphically strained regions in the grown epilayers, tentatively explained by bunching of threading dislocations. Considering that MBE growth of GeSn epitaxial layers, with such high-Sn content and layer thickness, has not been reported before, our results are encouraging for future improvements in design and fabrication of group-IV-based mid-infrared photonic devices. [ABSTRACT FROM AUTHOR]

By executing the Generalised Gradient Approximation (GGA) based on the Pethew Burke Emzerhof (PBE), the structural geometry, electronic band structures, total density of states (DOS), partial density of states (PDOS) and optical properties for both of undoped and doped ZnAg2GeTe4 were investigated. The calculated band gap of ZnAg2GeTe is 1.06 eV, indicating strong photocatalyst for organic pollutants. To explain the photocatalytic effect owing to hybridisation of orbitals, the DOS were simulated to assess the characteristics of 4s, 3d for Zn, 5s, 4d for Ag, 4s, 3d, 4p for Ge and 4s, 5s 4d 5p for Te orbitals travelling from the highest occupied valance bands to the lowest occupied conduction bands. The optical properties, for instance absorption, reflectivity, dielectric function and loss function may be indicated the increased absorption of visible light, as well as corresponds to electronic structure. For better photocatalytic activity, Fe metal was doped by replacing Ge at 7%. After doping, the band gap was decreased from 1.06 eV to 0.09 eV, and DOS was also increased. Nevertheless, optical properties, especially absorption, were also increased which indicates higher photocatalytic activity. It can be concluded that ZnAg2Ge0.93Fe0.07Te4 shows more photocatalytic activity than ZnAg2GeTe4 with the evidences from the band gap and optical properties. [ABSTRACT FROM AUTHOR]

An isotropic etching, etch rate and surface roughness of Si, Ge and Si0.8Ge0.2 subjected to CF4/Ar/O2 plasma has been studied using inductively coupled plasma (ICP) system. First, we applied the etching parameters on the silicon substrate to observe the etching rate using carbon tetrafluoride (CF4) under different flow rates and choose the parameters of high etch rate. The chosen parameters for silicon was CF4 (60 sccm) and etching in different ratios of argon (Ar) and oxygen (O2) were also discussed. Second, it also reports on selective isotropic etching for germanium (Ge) and Si0.8Ge0.2 by ultrahigh vacuum chemical vapor deposition (UHVCVD) and was etched under selected conditions used for silicon under different atmospheres in an inductively coupled plasma system. Starting from a pure CF4 gas that etches Ge and Si0.8Ge0.2 with a good selectivity to silicon, the modification of gas mixture was also investigated. A possible mechanism based on the favored action of CF4 is investigated. Relative etch rate between Si, Ge and Si0.8Ge0.2 are explained with etch rate reductions achieved by selective CF4 plasma chemistries with Ar/O2. Etched profile, surface roughness was examined and measured by using SEM and AFM technique. [ABSTRACT FROM AUTHOR]

We report on the growth and characterization of Ge-doped β-Ga2O3 thin films using a solid germanium source. β-Ga2O3 thin films were grown using a low-pressure chemical vapor deposition reactor with either an oxygen or a gallium delivery tube. Films were grown on 6° offcut sapphire and (010) β-Ga2O3 substrates with growth rates between 0.5 and 22 μm/h. By controlling the germanium vapor pressure, a wide range of Hall carrier concentrations between 1017 and 1019 cm−3 were achieved. Low-temperature Hall data revealed a difference in donor incorporation depending on the reactor configuration. At low growth rates, germanium occupied a single donor energy level between 8 and 10 meV. At higher growth rates, germanium doping predominantly results in a deeper donor energy level at 85 meV. This work shows the effect of reactor design and growth regime on the kinetics of impurity incorporation. Studying donor incorporation in β-Ga2O3 is important for the design of high-power electronic devices. [ABSTRACT FROM AUTHOR]

Polycrystalline Ge thin films have attracted increasing attention because their hole mobilities exceed those of single-crystal Si wafers, while the process temperature is low. In this study, we investigate the strain effects on the crystal and electrical properties of polycrystalline Ge layers formed by solid-phase crystallization at 375 °C by modulating the substrate material. The strain of the Ge layers is in the range of approximately 0.5% (tensile) to -0.5% (compressive), which reflects both thermal expansion difference between Ge and substrate and phase transition of Ge from amorphous to crystalline. For both tensile and compressive strains, a large strain provides large crystal grains with sizes of approximately 10 μm owing to growth promotion. The potential barrier height of the grain boundary strongly depends on the strain and its direction. It is increased by tensile strain and decreased by compressive strain. These findings will be useful for the design of Ge-based thin-film devices on various materials for Internet-of-things technologies. [ABSTRACT FROM AUTHOR]

In recent years, Germanium (Ge) photodiodes have established a widespread utilization in photonic-integrated circuits (PICs). However, the devices commonly exhibit a prominent dark current due to the substantial defects at the Ge/Si heteroepitaxial interface. Herein, we demonstrate normal-incidence, buffer-less Ge vertical p-i-n photodiodes with remarkably low dark current density (Jdark, 0.78 mA/cm2 at −1 V), on a high-quality 200-mm Ge-on-insulator (GOI) substrate. The high-quality GOI was achieved by the removal of the highly dislocated Ge/Si interfacial region, sequentially via wafer bonding, layer transfer, and oxygen (O2) furnace annealing. Compared to un-annealed GOI, the threading dislocation density (TDD) in Ge was reduced by more than two orders of magnitude to 1.2 × 106 cm−2. Correspondingly, the device Jdark and bulk leakage (Jbulk) were reduced by ~ 70 × and ~ 145 ×. On the other hand, the photodiodes present a reasonable responsivity of 0.29 A/W at 1,550 nm and a nearly 100% internal quantum efficiency without external bias. The specific detectivity D*, 2.17 × 1010 cm ⋅ Hz1/2 ⋅ W−1 at 1,550 nm and −0.1 V) is comparable with that of commercial bulk Ge photodiodes. In addition, the low temperature bonding and layer transfer can enable a compact integration at the back-end-of-line for PIC applications. This work paves the way for GOI photodiodes toward advanced high-resolution imaging and sensing applications on PICs at the near-infrared and short-wave infrared wavelength. [ABSTRACT FROM AUTHOR]

Group-IV based light sources are one of the missing links towards fully CMOS compatible photonic circuits. Combining both silicon process compatibility and a pseudo-direct band gap, germanium is one of the most viable candidates. To overcome the limitation of the indirect band gap and turning germanium in an efficient light emitting material, the application of strain has been proven as a promising approach. So far the experimental verification of strain induced bandgap modifications were based on optical measurements and restricted to moderate strain levels. In this work, we demonstrate a methodology enabling to apply tunable tensile strain to intrinsic germanium nanowires and simultaneously perform in situ optical as well as electrical characterization. Combining I/V measurements and μ-Raman spectroscopy at various strain levels, we determined a decrease of the resistivity by almost three orders of magnitude for strain levels of ∼5%. Thereof, we calculated the strain induced band gap narrowing in remarkable accordance to recently published simulation results for moderate strain levels up to 3.6%. Deviations for ultrahigh strain values are discussed with respect to surface reconfiguration and reduced charge carrier scattering time. [ABSTRACT FROM AUTHOR]

We explore the radiation induced effects in thin films from the Ge-Se to Ge-Te systems accompanied with silver radiation induced diffusion within these films, emphasizing two distinctive compositional representatives from both systems containing a high concentration of chalcogen or high concentration of Ge. The studies are conducted on blanket chalcogenide films or on device structures containing also a silver source. Data about the electrical conductivity as a function of the radiation dose were collected and discussed based on material characterization analysis. Raman Spectroscopy, X-ray Diffraction Spectroscopy, and Energy Dispersive X-ray Spectroscopy provided us with data about the structure, structural changes occurring as a result of radiation, molecular formations after Ag diffusion into the chalcogenide films, Ag lateral diffusion as a function of radiation and the level of oxidation of the studied films. Analysis of the electrical testing suggests application possibilities of the studied devices for radiation sensing for various conditions. [ABSTRACT FROM AUTHOR]

This report demonstrates nontoxic colloidal nitrate route CZTS (Cu2ZnSnS4) synthesis at room temperature, along with their band grading due to incorporation of Ge as cost of Sn (3%). The parent CZTS, CZGTS (Cu2ZnGeSnS4), and their polyvinyl alcohol (PVA), dimethyl sulfoxide (DMSO) solvent containing solutions doctor blade-coated thin film structural and optical properties are discussed. Their sulfurized thin films thickness have been achieved ±2 μ. It has noticed that addition of Ge in CZTS alloy affects the grain sizes, crystallographic structure, Raman spectral peak shift toward the higher wave number side. The addition of PVA and DMSO is also substantially contributed in their physical property modification by demonstrating the gradual improvement in grain sizes and compactness. Moreover, the gradual changes have also appeared in their X-ray diffractometer (XRD) and Raman spectroscopic results. The optical energy band gaps of the CZTS, CZGTS, and their PVA, DMSO mixed alloyed thin films are obtained in between 1.27 eV to 1.57 eV and 1.58 eV to 1.83 eV. [ABSTRACT FROM AUTHOR]

The germanium auto‐diffusion effects on the inter‐atomic distance between the nearest neighbors of the Ga atom in GaP epilayers are investigated using high‐resolution X‐ray diffraction (HRXRD) and X‐ray absorption spectroscopy. The GaP layers grown on Ge (111) are structurally coherent and relaxed but they show the presence of residual strain which is attributed to the auto‐diffusion of Ge from the results of secondary ion mass spectrometry and electrochemical capacitance voltage measurements. Subsequently, the inter‐atomic distances between the nearest neighbors of Ga atom in GaP are determined from X‐ray absorption fine‐structure spectra performed at the Ga K‐edge. The estimated local bond lengths of Ga with its first and second nearest neighbors show asymmetric variation for the in‐plane and out‐of‐plane direction of GaP/Ge(111). The magnitude and direction of in‐plane and out‐of‐plane microscopic residual strain present in the GaP/Ge are calculated from the difference in bond lengths which explains the presence of macroscopic residual tensile strain estimated from HRXRD. Modified nearest neighbor configurations of Ga in the auto‐diffused GaP epilayer are proposed for new possibilities within the GaP/Ge hetero‐structure, such as the conversion from indirect to direct band structures and engineering the tensile strain quantum dot structures on (111) surfaces. [ABSTRACT FROM AUTHOR]

The properties of six kinds of intrinsic point defects in monolayer GeS are systematically investigated using the "transfer to real state" model, based on density functional theory. We find that Ge vacancy is the dominant intrinsic acceptor defect, due to its shallow acceptor transition energy level and lowest formation energy, which is primarily responsible for the intrinsic p-type conductivity of monolayer GeS, and effectively explains the native p-type conductivity of GeS observed in experiment. The shallow acceptor transition level derives from the local structural distortion induced by Coulomb repulsion between the charged vacancy center and its surrounding anions. Furthermore, with respect to growth conditions, Ge vacancies will be compensated by fewer n-type intrinsic defects under Ge-poor growth conditions. Our results have established the physical origin of the intrinsic p-type conductivity in monolayer GeS, as well as expanding the understanding of defect properties in low-dimensional semiconductor materials. [ABSTRACT FROM AUTHOR]

The stabilization of silicon(II) and germanium(II) dihydrides by an intramolecular Frustrated Lewis Pair (FLP) ligand, PB, iPr2P(C6H4)BCy2 (Cy=cyclohexyl) is reported. The resulting hydride complexes [PB{SiH2}] and [PB{GeH2}] are indefinitely stable at room temperature, yet can deposit films of silicon and germanium, respectively, upon mild thermolysis in solution. Hallmarks of this work include: 1) the ability to recycle the FLP phosphine‐borane ligand (PB) after element deposition, and 2) the single‐source precursor [PB{SiH2}] deposits Si films at a record low temperature from solution (110 °C). The dialkylsilicon(II) adduct [PB{SiMe2}] was also prepared, and shown to release poly(dimethylsilane) [SiMe2]n upon heating. Overall, this study introduces a "closed loop" deposition strategy for semiconductors that steers materials science away from the use of harsh reagents or high temperatures. [ABSTRACT FROM AUTHOR]

The absorption Mössbauer spectroscopy on 119Sn impurity centers shows that germanium atoms in the structure of amorphous and polycrystalline Ge2Sb2Te5 films have different local symmetries (tetrahedral in the amorphous phase and octahedral in the crystalline). By emission Mössbauer spectroscopy on 119mSn impurity centers formed after the radioactive decay of 119Sb or 119mTe parent atoms, tin antisite defects at antimony and tellurium sites of crystalline Ge2Sb2Te5 films are identified. [ABSTRACT FROM AUTHOR]

In situ electrochemical cells were assembled with an amorphous germanium (a-Ge) film as working electrode and sodium foil as reference and counter electrode. The stresses generated in a-Ge electrodes due to electrochemical reaction with sodium were measured in real-time during the galvanostatic cycling. A specially designed patterned a-Ge electrode was cycled against sodium and the corresponding volume changes were measured using an AFM; it was observed that sodiation/desodiation of a-Ge results in more than 300% volume change, consistent with literature. The potential and stress response showed that the a-Ge film undergoes irreversible changes during the first sodiation process, but the subsequent desodiation/sodiation cycles are reversible. The stress response of the film reached steady-state after the initial sodiation and is qualitatively similar to the response of Ge during lithiation, i.e., initial linear elastic response followed by extensive plastic deformation of the film to accommodate large volume changes. However, despite being bigger ion, sodiation of Ge generated lower stress levels compared to lithiation. Consequently, the mechanical dissipation losses associated with plastic deformation are lower during sodiation process than it is for lithiation. [ABSTRACT FROM AUTHOR]

Abstract—Extensive studies of Ge2Sb2Te5 material are associated with the possibility of producing multilevel nonvolatile elements for high-speed integrated optical functional circuits. The principle of multilevel recording in such devices is based on the formation of partially crystallized regions with substantially different optical properties in Ge2Sb2Te5 thin films. To predict the parameters of the effect initiating phase transformations and to reliably provide a reversible transition between many logic states, it is necessary to have reliable data on the optical characteristics of Ge2Sb2Te5 thin films in states with different degrees of crystallinity and on the conditions of attainment of such states. In the study, the influence of the phase state of Ge2Sb2Te5 films on the extinction coefficient and refractive index and variations in the optical band gap in relation to the temperature of heat treatment are investigated. Ge2Sb2Te5 thin-film samples are examined by means of atomic-force microscopy, X-ray phase analysis, and energy-dispersive microanalysis to determine the film thickness, morphology, phase state, and composition. By spectroscopic ellipsometry, the spectra of the ellipsometric angles ψ and Δ (the amplitude and phase components of the light wave) are obtained, and the extinction coefficient and refractive index are determined. The influence of the layer models and mathematical models on calculation of the dispersions of the optical parameters of Ge2Sb2Te5 films is considered. A substantial increase in the extinction coefficient and refractive index at the wavelength 1550 nm on heat treatment at temperatures higher than 200°С is established. It is shown that the optical band gaps of Ge2Sb2Te5 thin films in the amorphous and crystalline states are 0.71 and 0.47 eV, respectively. It is found that the dependences of the extinction coefficient, refractive index, and band gap on the degree of crystallinity of Ge2Sb2Te5 thin films are close to linear. [ABSTRACT FROM AUTHOR]

A model for calculation of thermal conductivity of thin films of silicon and germanium is presented on the basis of solving the Boltzmann equation in the time relaxation approximation. The unique feature of this model is the application of recent achievements in determination of the time of phonon–phonon interactions obtained from "first principles" and also the use of real dispersion curves and the propagation velocities of phonons with different polarization. The proposed approach contains no averaging and fitting parameters, which already for more than half a century and until now have been common in calculations of thermal conductivity of macroscopic bodies and nanostructures. A detailed qualitative and quantitative comparison of results of calculations by the "classical" and "updated" models is carried out. Problems in the methods for calculating thermal conductivity for simulation of new structures in advanced semiconductor devices and ways of their further development are set forth. [ABSTRACT FROM AUTHOR]

Although numerous chalcogenide glass systems including GeTe6 and GexSe100−x have been explored for Ovonic Threshold Switch (OTS) selectors in vertically stackable cross‐point memory applications, yet an improved thermal and structural stability at elevated temperatures remains a key challenge. Herein, a systematic temperature‐dependent experimental investigation on the thermal stability and local structural changes of as‐deposited amorphous thin Ge20Te80 film is conducted for a wide range of temperatures from 25 to 260 °C. The coherent experimental studies reveal that the amorphous phase is stable up to 180 °C, and the crystallization process is initiated above 180 °C, by simultaneous crystallization of Te and GeTe until ≈238 °C as substantiated by temperature‐dependent sheet resistance, X‐ray diffraction, and Raman spectroscopic measurements. Furthermore, the local structural changes over the crystallization process of Ge20Te80 thin film are elucidated by Raman spectroscopy. These experimental findings provide a decisive understanding of the thermal stability and structural evolution of Ge20Te80 thin films toward designing stable OTS selector materials. [ABSTRACT FROM AUTHOR]

By optical methods (Raman spectroscopy, infrared spectroscopy, X-ray photoelectron spectroscopy) and electron-microscopy techniques, it was found that the atomic structure of germanium monoxide films of stoichiometric composition corresponds to the random bonding model and does not contain germanium nanoclusters. This structure is metastable and transforms into a random mixture structure at a temperature of 260°C and higher. The metastability of solid GeO can be caused by internal strains in the atomic network. [ABSTRACT FROM AUTHOR]

In this work, Cu 2 ZnSn 1- x Ge x S 4 (CZTGS) precursor thin films with varied Ge composition (x = 0, 0.2, 0.4, 0.6, 0.8, and 1) were prepared by using a water-based solution approach. After selenizing at 550 °C for 10 min in a graphite box containing selenium powder, the as-fabricated kesterite Cu 2 ZnSn 1- x Ge x (S,Se) 4 (CZTGSSe) thin films were systematically investigated for phase structure, morphology, valence states of elements, optical properties, and electrical properties. The results showed that the Ge element was successfully incorporated into the host lattice of Cu 2 ZnSn(S,Se) 4 (CZTSSe), and kesterite CZTGSSe films were formed. As the Ge content increased, the crystal grains in the films grew larger and showed uniform morphology on the sample surfaces. The band gap in the CZTGS(Se) thin films could be engineered in the range of 1.21 eV–2.00 eV by tuning the relative compositions of the Ge elements. Furthermore, it was confirmed that the doping of Ge improved the mobility, resistivity, and photoelectric performance of the films. Finally, the Cu 2 ZnSn 0.8 Ge 0.2 (S,Se) 4 solar cell device with an efficiency of 5.39% was prepared. The results indicate that non-toxic water solution-based CZTGSSe films showed potential for application in solar cells. [ABSTRACT FROM AUTHOR]

Layer-exchange crystallization of Ge using a group-V element has been investigated to develop a low-temperature (<500 °C) formation technique of n-type tensile-strained crystalline Ge on insulator. Here, the Sb of a group-V element is employed as a catalyst. Annealing (450 °C) of a-Ge (100 nm)/Sb (100 nm) bi-layer stacked structures generates layer-exchange crystallization. Namely, Ge and Sb layers exchange their positions, and Ge layers are crystallized on insulator substrates. However, Ge evaporation occurs during annealing, and a high concentration of Sb (∼20%) remains at the Ge/insulator interface. To solve these problems, the thickness reduction of Sb films and introduction of a-Ge thin under-layers are examined. By annealing (450 °C) a-Ge (100 nm)/Sb (50 nm)/a-Ge (5 nm) tri-layer structures, layer-exchange crystallization of Ge layers on insulator without Ge evaporation or Sb residue has been achieved. This enables formation of n-type tensile-strained (∼0.3%) Ge layers (free electron concentration: ∼5 × 1017 cm−3). Moreover, crystal orientation control of grown Ge films through the introduction of the diffusion barrier is examined. These results demonstrate the possibility of layer-exchange crystallization induced by a group-V element to realize functional thin-film devices for advanced electronics and photonics. [ABSTRACT FROM AUTHOR]