Pressure Chemical Vapor Deposition Research Articles

Synthesis of manganese oxide thin films deposited on different substrates via atmospheric pressure-CVD

In this study, we report the synthesis of manganese oxide (MnxOy) thin films on stainless steel, silicon, and borosilicate glass substrates via atmospheric pressure chemical vapor deposition (AP-CVD) using Mn(thd)3 and O3 as precursor and reactive gas, respectively. Deposition was achieved at a low temperature of 300 °C under atmospheric pressure, offering a cost-effective and scalable alternative to traditional high-vacuum CVD methods. The films displayed excellent adhesion and reproducibility, with substrate-dependent variations in film coloration, crystal phases, and morphology. X-ray diffraction (XRD) and Raman spectroscopy confirmed the presence of Mn3O4 and Mn2O3 phases, with Mn3O4 predominating on stainless steel and silicon, while Mn2O3 was more prominent on glass. Scanning electron microscopy (SEM) revealed granular structures with uniform grain sizes, particularly on stainless steel substrates. X-ray photoelectron spectroscopy (XPS) confirmed Mn2+ and Mn3+ oxidation states, consistent with the phase distribution observed by XRD and Raman analysis. This work demonstrates the potential of AP-CVD for scalable manganese oxide thin-film synthesis, particularly for energy storage applications, where Mn3O4 and Mn2O3 can serve as precursors to δ-MnO2 in supercapacitors. The method's simplicity, combined with the high-quality films produced, makes it a promising approach for future research and industrial-scale applications.

Benchmarking of HCl-Based Cyclic Deposition / Etch (CDE) and Single Deposition / Etch (DE) Processes for Selective Epitaxial Growth of SiGeC:B Films

In this paper, SiGeC:B growth behaviors at 550 °C, 10 Torr, were studied in a 300 mm industrial Reduced Pressure-Chemical Vapor Deposition reactor using a Si2H6/GeH4/SiH3CH3/B2H6 chemistry. Carbon atoms, for both SiGeC and SiGeC:B layers, were only incorporated into substitutional sites, with concentrations up to ~ 1.4 at%. It appeared that in-situ boron doping at a level of 1x1020 at.cm-3 did not modify the substitutional carbon incorporation. However, carbon and boron atoms were shown to compete for substitutional incorporation sites, as outlined by the increased SiGeC:B films resistivity. Cyclic Deposition / Etch (CDE) and Deposition / Etch (DE) processes were then benchmarked on blanket Si substrates and blanket Si wafers covered with 10 nm of Si3N4, with the aim to achieve selective growth on patterned wafers. The CDE process consisted of 10 cycles with deposition steps at 550 °C, 10 Torr and etch steps at 550 °C, 50 Torr with a very high HCl flow. The simpler DE process consisted in a single deposition step at 550 °C, 10 Torr, followed by a single etch step at 550, 575 or 600 °C, 600 Torr, with a very low HCl flow. CDE and DE processes both resulted in a rather low etch selectivity of 1.8 and produced slightly rough SiGeC:B surfaces. Finally, it was shown that the use of a HCl-based CDE process is not a viable solution to obtain high quality SiGeC:B films on patterned wafers at low growth temperatures. Meanwhile, DE yielded higher quality if slightly rough SiGeC:B layers.

Opto-electronic responses of large area WSe2 layers synthesized by chemical conversion of WO3 thin films

Atomically thin tungsten diselenide (WSe2) has drawn much interest due to its remarkable optical properties and potential applications in next-generation optoelectronics and energy harvesting devices. High-quality, wafer-scale synthesis of such two-dimensional (2D) semiconductors is necessary for their practical applications. Chemical vapor deposition (CVD) is a promising method for synthesizing large-area thin films of 2D materials where the constituent elements are of widely different vapor pressure. Herein, we demonstrate large-area synthesis of the 2H phase of WSe2 with a precise control over the 2D film thickness. The first step of this process is the deposition of tungsten trioxide (WO3) films of a well-defined thickness by thermal evaporation over large areas. The subsequent selenization of these films in an atmospheric pressure CVD reactor, yields high-quality uniform films of WSe2. The quality of these films is ascertained by measuring their characteristic Raman active vibrational modes and layer thickness dependent optical absorption and photoluminescence. The photoconductivity (PC) of these films has been measured with 405, 532 and 915 nm laser excitation. We note an increase in the PC of the films with their thickness. The best photoresponsivity and detectivity obtained are 11.3 mA/W and 1.42 × 108 Jones respectively. These results are promising to create photo-transistor arrays over large areas using such WO3 processed films.

Chemical vapor deposition of large-area ultrathin Cr3Te4 nanosheets with robust ferromagnetism

Abstract Chromium tellurides represent a novel class of two-dimensional ferromagnets with significant potential for advanced electronic applications, including spintronics and magnonics. Despite their promise, the fabrication of large-area samples remains a considerable challenge. In this study, we report a facile modification to the common ambient-pressure chemical vapor deposition setup that enables the synthesis of ultrathin Cr3Te4nanosheets (6.4 nm thick) with lateral dimensions exceeding 100 μm. Our findings reveal that by tuning both the growth temperature and the distance between the precursor and substrate, the vapor pressure of the precursor can be precisely controlled, significantly impacting the size and morphology of the synthesized Cr3Te4 nanosheets. The resulting large-size Cr3Te4exhibits robust ferromagnetism, with a Curie temperature reaching 178 K. This advancement in the preparation of large-area Cr3Te4nanosheets opens new avenues for their integration into next-generation electronic devices.

Electrical properties and evaluation of band tail states in Mg doped p-type multilayer hBN

A series of Mg doped p-type multi-layered hBN films were prepared by atmospheric pressure chemical vapor deposition. Temperature dependent conductivity measurements were performed from 0.1 Hz to 10 MHz to analyze the characteristics of tail states close to the valence band edge. Jonscher's power law (Aωs) is successfully applied to understand charge carrier transport through these states. In this work, exponent S increases from 0.6 → 0.8, 0.8 → 0.995, and 1.4 → 1.6 for samples B (precursor temperature, 750 °C), D (850 °C), and E (900 °C), indicating that non-overlapping small polaron tunneling dominates to 548 K. Polaron binding energies of 0.2–0.40 eV and tunneling distances <4.9 Å are calculated, confirming transport through localized states. The density of states near the Fermi level N(EF) was extracted from a fit to the AC conductivity data, yielding values of 1015 and 1017eV−1cm−3 as the precursor temperature increases. Singular Mg acceptor levels of 74, 30, and 17 meV are identified for each sample. A hole concentration from 6.5 × 1017 to 1 × 1018 cm−3 and carrier mobility from 18 to 25 cm2/V s is measured at 300 K. From RC fitting, carrier recombination lifetimes of 1.2, 0.4, and 0.35 μs are determined. Fermi's golden rule is used to determine an optical joint density of states of 1.1 × 1021 eV−1 cm−3 at a band edge. Overall, we show that AC conductivity is an effective method to evaluate midgap states in 2D (two-dimensional) materials at EF and p-type hBN possesses sufficient electrical properties to be integrated into a wide range of semiconductor applications.

Ultrathin carbon doped hexagonal boron nitride films for electromagnetic interference shielding in the terahertz region

We have investigated the electromagnetic interference (EMI) shielding efficiency of carbon-doped hexagonal boron nitride (hBN) films in 0.3–1.8 THz regions using transmission-based terahertz time-domain spectroscopy (THz TDS). The hBN films were synthesized on Copper foils by atmospheric pressure chemical vapor deposition (APCVD) utilizing ammonia borane (AB) powder as a precursor. Carbon doping of BN films was achieved by using the intrinsic carbon dissolved in the Copper substrate. The EMI shielding efficiencies and the optical, dielectric, and electrical properties of the films were determined using THz TDS. The Absorbance is much greater than the Reflectance indicating that absorption is the dominant mechanism of shielding in these films. These carbon-doped hBN films show a high EMI shielding effectiveness, with 99.99 % EM radiation blocked. A maximum value of 30 dB and 55 dB at 1.72 THz were observed for films with 4.5 nm and 6.5 nm thicknesses. This is equivalent to shielding efficiency per unit thickness of 6667 dB/µm and 8460 dB/µm, which is among the highest reported for 2D materials.

Synthesis and characterization of graphene on copper foil via atmospheric pressure chemical vapor deposition method and its impact on electrical properties

Copper, prized for its exceptional electrical conductivity, thermal conductivity, and mechanical strength, is a staple in electronic applications. The ongoing quest for enhanced performance in miniaturized technologies has led to exploring copper-graphene composites, particularly those integrating bilayer graphene (BLG). This study investigates the enhancement of electrical conductivity in copper through the incorporation of BLG via atmospheric pressure chemical vapor deposition (APCVD). The research highlights the APCVD method's ability to grow high-quality BLG on high-purity oxygen-free copper foil, demonstrating significant improvements in electrical properties. Detailed characterization reveal that the graphene growth process induces structural changes in the copper, promoting ideal crystallographic orientations and larger grain sizes. This process achieves nearly complete graphene coverage and results in a copper/graphene (Cu/GR) composite with minimal defects. The electrical conductivity of the Cu/GR composite significantly increased to 59.32 × 10⁶ S·m⁻1, a 7.83 % improvement over the pristine copper foil. This enhancement is attributed to the increased carrier density and mobility within the composite. These advancements suggest the potential of APCVD-grown graphene for various high-performance electronic applications, providing a promising pathway for further development and optimization of graphene-copper composites.

Improved surface morphology and reduced V-pits density of lattice-matched AlInN films grown by atmospheric pressure metalorganic chemical vapor deposition

AlInN has emerged as a promising material for advanced optoelectronic and electronic devices due to its unique properties. However, achieving AlInN layers with excellent surface morphology remains challenging. Here, Al0.83In0.17N layers lattice-matched to GaN/sapphire were grown by atmospheric-pressure metalorganic chemical vapor deposition at 875 °C. The lowest surface roughness measured by atomic force microscopy was 0.37 nm after optimizing the growth temperature and flux of precursors. The roughness value was constant in the range of 15–72 nm film thickness. Introducing a TMI pre-flow period before AlInN growth, further reduced roughness to 0.28 nm, although a graded inclusion of Ga into the AlInN near the GaN/AlInN interface was observed. This improved surface morphology was interpreted by the In-surfactant effect enriched by the pre-flow in the early stage of AlInN. Additionally, the V-pits density was as low as 2×105 cm−2, primarily due to high growth pressure and also influenced by relatively high growth temperature. Analysis of Al incorporation using second-order reaction model suggests that the severe parasitic reactions between TMA and NH3 at atmospheric pressure can be effectively eliminated by a high total gas flow rate of 72 slm, ensuring in-plane uniformity in surface morphology and relatively good crystalline quality.

Modulation of the morphological and optical properties of CVD grown non-Stochiometric [formula omitted] nanostructures by various substrate angles

Gallium oxide (Ga2O3) nanostructures (NSs) were synthesized via atmospheric pressure chemical vapor deposition (APCVD) technique assisted by hydrogen. The geometrical orientation in terms of the substrate angle was studied to investigate its influence on the morphological, compositional and optical properties of the material. The results revealed that the geometry, stoichiometry and optical parameters of Ga2O3 could be tuned by substrate angle variations during deposition. Tilting the substrate was found to enhance the step coverage of the substrate and the Ga/O atomic ratio above the stoichiometric value. Bandgap of the films was observed to vary inversely (ranged between 4.590 and 4.664eV) to the Ga/O atomic ratio. The refractive index at wavelength of 632.8 nm, dispersion and single oscillator energy of the prepared films were also evaluated, and were found to be in the range of 2.129–3.265, 20.952–56.520eV and 5.309–6.387eV, respectively, with the increase of substrate angle.

Mixed phase iron oxides thin layers by atmospheric-pressure chemical vapor deposition method

This paper provides a simple method for producing a metal oxide thin layer methodology by atmospheric pressure chemical vapor deposition (APCVD) synthesis over stainless steel substrates. This methodology enables the formation of thin iron oxide layers at its performance at various temperatures of 330 °C, 430 °C, and 530 °C. The deposition arises from thermal decomposition of the iron organometallic precursor Fe3(CO)12, forming a thin layer of iron oxide is, by the ozone present in the reaction chamber promoting the deposition of the iron oxide particles over the substrate. The Raman characterization suggest that at 330 °C, a mixture of hematite and magnetite is predominant on the as deposited substrates, also hematite modes show to be more pronounced as the band at 300 cm-1 narrows. Conversely, magnetite is prominent at higher synthesis temperatures, exhibiting a more intense Eg5 mode at 680 cm-1. The particles exhibit a uniform morphology, with both metal oxide phases coexisting. The average diameter of the particles is 50 nanometers as scanning electronic microscopy shows in a transversal sample section.•The formation of particles is attributed to the combination of iron ions +2 and +3 in the deposition process and their interaction with oxygen in the given synthesis parameters at atmospheric pressure chemical vapor deposition (APCVD).

Oxygen-doped FeP on Ti Foil with Ti3O Interlayer for Efficient and Durable Electrolysis.

Thedevelopment of electrocatalysts withlow cost, high efficiency, and long-term durability is crucial for advancing green hydrogen production.Transition metal phosphides (TMPs) have been proved to be efficient electrocatalyst, while the improvement in the performance and durability of the TMPs remains a big challenge.Employing atmospheric pressure chemical vapor deposition (APCVD) and phosphorization, FeP/Ti electrodes are fabricated featuring controllable oxygen ingredients (O-FeP/Ti). This manipulation of oxygen content fine-tunes the electronic structure of the catalyst, resulting in improved surface reaction kinetics and catalytic activity.The optimized O-FeP-400/Ti exhibits outstanding HER activity with overpotentials of 142 and 159 mV at -10 mA cm-2in 0.5 M H2SO4and 1 M KOH, respectively.Notably, the obtained O-FeP/Ti cathode also displays remarkable durability of up to 200 h in acidic electrolyte withsurface topographyremaining intact.For the first time, the low-valence titanium oxide (Ti3O) interlayeris identified in the composite electrode and ascribed for the superior connection between Ti substrate and the surface O-FeP catalyst, as supported by experimental resultsand density functional theory (DFT) analysis.This work has expanded the potential applicationsof transition metal phosphides (TMPs) as a cost-effective, highly efficient and durable catalyst for water splitting.

High-Yield WS2 Synthesis through Sulfurization in Custom-Modified Atmospheric Pressure Chemical Vapor Deposition Reactor, Paving the Way for Selective NH3 Vapor Detection.

Nanostructured transition metal dichalcogenides have garnered significant research interest for physical and chemical sensing applications due to their unique crystal structure and large effective surface area. However, the high-yield synthesis of these materials on different substrates and in nanostructured films remains a challenge that hinders their real-world applications. In this work, we demonstrate the synthesis of two-dimensional (2D) tungsten disulfide (WS2) sheets on a hundred-milligram scale by sulfurization of tungsten trioxide (WO3) powder in an atmospheric pressure chemical vapor deposition reactor. The as-synthesized WS2 powders can be formulated into inks and deposited on a broad range of substrates using techniques like screen or inkjet printing, spin-coating, drop-casting, or airbrushing. Structural, morphological, and chemical composition analysis confirm the successful synthesis of edge-enriched WS2 sheets. The sensing performance of the WS2 films prepared with the synthesized 2D material was evaluated for ammonia (NH3) detection at different operating temperatures. The results reveal exceptional gas sensing responses, with the sensors showing a 100% response toward 5 ppm of NH3 at 150 °C. The sensor detection limit was experimentally verified to be below 1 ppm of NH3 at 150 °C. Selectivity tests demonstrated the high selectivity of the edge-enriched WS2 films toward NH3 in the presence of interfering gases like CO, benzene, H2, and NO2. Furthermore, the sensors displayed remarkable stability against high levels of humidity, with only a slight decrease in response from 100% in dry air to 93% in humid environments. Density functional theory and Bayesian optimization simulations were performed, and the theoretical results agree with the experimental findings, revealing that the interaction between gas molecules and WS2 is primarily based on physisorption.

Water assisted atmospheric CVD super growth of vertically aligned CNT forest for supercapacitor application

We report a high growth rate (37 μm/min) synthesis of vertically aligned carbon nanotube (VACNT) forest, achieving remarkable height exceeding a millimetre with good crystallinity. VACNTs with few numbers of walls have been grown over Fe–Co/Al2O3/SiO2 coated Si wafer using the water assisted atmospheric pressure chemical vapour deposition (WACVD) method. The key to this success lies in the synergistic combination of a bimetallic catalyst (Fe-Co) with buffer Al2O3 layer and the WACVD method. Notably, the VACNT forest, synthesised at optimized conditions can be directly used without the need for additional post-growth purification processes, eliminating the risk of potential damage to the CNTs. Finally, the VACNT forest exhibits excellent areal capacitance of 133.33 mF/cm2 at a current density of 1 mA/cm2 with outstanding cyclic stability of 130 % @ 3000 cycles.

Numerical Analysis of Thickness Uniformity Improvement with Different Inlet Plate Numbers during APCVD Process

As the nanometer line width in the semiconductor industry further shrinks, the surface flatness requirements for atmospheric pressure chemical vapor deposition epitaxial silicon films have further increased. Through a series of numerical simulations, this study analyzes the use of inlet plates to solve the problem of uneven wafer thickness during atmospheric pressure chemical vapor deposition. The results show that without the inlet plate, the deposition rate is lower at the center of the wafer and higher at the edge of the wafer. Wafer epitaxy thickness uniformity can be improved when inlet plates are used. By adjusting the position of the inlet plates, this unevenness can be further improved. As the number of inlet plates increases from 0 to 3, the wafer thickness non-uniformity decreases from 12.5% to 1.8% respectively. When the number of inlet plates continues to increase, the thickness uniformity of the wafer can be further improved. When the number of inlet plates is 5, the thickness unevenness of the wafer reaches 0.7%.

In Situ transmission Electron Microscope Observation of Biased-Induced Dynamic Evolution of Two-Dimensional CrS2

Two-Dimensional transition-metal dichalcogenides (2D-TMDs) have attracted great attention recently owing to their potential to become the important material for next generation semiconductor devices. While using the device, it needs to ensure high density current and biased voltage for a long time. However, the study on TMDs in high-energy environment is insufficient. In this work, the phase evolution of CrS2 are revealed via in-situ biasing experiments and recorded by transmission electron microscope (TEM) at atomic scale. The ultra-thin layered (~1.6nm) CrS2 was synthesized through atmospheric pressure chemical vapor deposition (APCVD), followed by transferring the as-grown samples onto specialized TEM electrical chips. The TEM characterization of CrS2 initial sample provided the basic understanding of this Cr-based TMD, identified as pure 1T phase with single crystal structure as shown in Figure 1. The advanced in situ technique was employed to record the structural evolution and was tested the endurance of CrS2 during biasing. Moreover, the results can make significant contributions to future semiconductor device designs and demonstrate CrS2 has great potential as a semiconductor device with its outstanding characteristic of biased-endurance. Figure1. (a) Low-magnification TEM image of 1T-CrS2. (b) High-resolution TEM image of 1T-CrS2, corresponding with FFT along [001] zone axis. (c) AFM image of the as-grown CrS2 sample, blue bar in the image is X axis of (d). (d) AFM height profile of as-grown 1T-CrS2 with average thickness of~1.6nm. (e) STEM image of 1T-CrS2 and shows d-spacing~0.336 nm. (f) Low-magnification TEM image of the device, showing that the transferred CrS2 layer was suspended on the membrane with Au electrodes on both sides. (g,h) In-situ TEM observation of the biasing experiment after 5V biasing for 5 min of 1T-CrS2. Time-sequencing TEM images showing the structural evolution of biasing. The inset shows the corresponding FFT-DP to reveal the variation of crystallinity of the sample. (g) Initial structure of 1T-CrS2. (h) 1T-CrS2 under in-situ biasing experiment after 10 minutes. Figure 1

Direct Growth Graphene Via Atmospheric Pressure Chemical Vapour Deposition

The integration of graphene in field-effect transistor (FET) has aroused tremendous attention in the field of sensor technology, particularly for electronic biosensors. However, transferring graphene from metal substrates has destructive effects on the electrical characteristics of the graphene film, leading to severe impurities and defects. Here, we investigated a new approach of technique to synthesis direct- growth semiconducting graphene via atmospheric pressure chemical vapour deposition (APCVD) method. In this study we observe the effects of different reaction times, carbon concentrations and temperatures on the carbon arrangement in graphene. The synthesised graphene was characterised by Raman spectroscopy and field emission scanning electron microscopy (FESEM) to observe the quality of graphene formation. From the Raman analysis, the I2D/IG ratio < 1 indicates the formation of graphene in multiple layers. The ID /IG ratio < 1 was also observed, indicating that the graphene has less disorder of defects. Based on the electrical measurement of the material at estimated distance of 250 μm, a higher I2D/IG ratio leads to a higher resistance. Full width at half maximum (FWHM) of 2D band shows graphene with the highest I2D/IG ratio has the lowest value of FWHM. As the conclusion, these directly grown semiconducting graphene layers can be efficiently integrated into biosensors without any complex post-treatment process.

Vanadium pentoxide nanowires preparation via kinetic control of vanadium oxytrichloride catalytic oxidation with APCVD

Vanadium pentoxide nanowires were successfully fabricated using vanadium oxytrichloride oxidation with copper oxide nanoparticles serving as catalysts via atmospheric pressure chemical vapor deposition. Kinetic parameters such as temperature and flow velocity were proved to play important roles in the morphologic control of as-deposited product. Vanadium pentoxide nanowires with an average length of ∼10 μm and a diameter of 50–100 nm, were obtained under the optimum conditions. A root growth mechanism of nanowires was proposed that precursor was readily captured by catalyst nanoparticles at the beginning of deposition, forming nucleation sites. Subsequently, the anisotropic growth of vanadium pentoxide is primarily governed by energy minimization under the reaction rate limited conditions. The presence of oxygen vacancies in the nanowires was confirmed by Raman, XPS and photoluminescence characterization, indicating promising applications in functional materials manufacture. The novel route for preparing vanadium pentoxide nanowires provides an alternative pathway for transitioning traditional vanadium industry towards advanced functional materials development.

Experimental characterization and crystal plasticity finite element simulation of the microstructural evolution in CVD tungsten during multi-step rolling

Atmospheric pressure chemical vapor deposition (CVD) is a promising technique for the preparation of tungsten products with high purity, high density and almost unlimited thickness. The tungsten prepared by using the CVD method (CVD-W) usually has a columnar coarse grain microstructure with strong preferred orientations. Multi-step rolling at gradually decreased operating temperatures is an effective method to lower the ductile-to-brittle transition temperature in pure tungsten. So far, the microstructural evolutions of CVD-W during the multi-step rolling processing is still unclear. In this study, the microstructure evolution and texture development of CVD-W during multi-step rolling are investigated by the coupling of electron backscattering diffraction technique and full-field crystal plasticity finite element simulations. After multi-step rolling, the sample exhibits through-thickness texture gradient. A layered structure with elongated 〈100〉 // ND and 〈111〉 // ND grains is observed in the central region and Goss orientation mainly appears in the surface region. Crystal plasticity finite element simulations show that {001}〈110〉 is a stable orientation under the plane strain compression, which is realized by the rotation of {100} grains around ND. Meanwhile, the shear flow promotes the rotation of {100} grains around TD, leading to the formation of 〈111〉 // ND orientation. 〈110〉 // ND orientation is observed near the shear bands, which is generated through the rotation of {100} grains around <100> // RD axis. The rolled CVD-W exhibits crystallographic orientation dependent recrystallization behavior, which is related to the orientation dependent distortion energy generated in the rolling processing. Our studies provide fundamental insights into the microstructure evolution and texture development of CVD-W under the multi-step rolling processing.

The GeSe/SnSe heterojunction photodetector with self-powered characteristics and high infrared response performance

We present a GeSe/SnSe van der Waals heterojunction fabricated using the wet transfer technique. GeSe and SnSe were synthesized via a low-temperature and atmospheric-pressure chemical vapor deposition method. The GeSe/SnSe heterostructure photodetector demonstrates remarkable rectification characteristics, boasting a rectification ratio of 102, along with an exceptionally low dark current, indicating minimal power consumption. Furthermore, it exhibits a broad optical response, spanning from the visible spectrum (450 nm) to the near-infrared (1064 nm). Under 808 nm laser illumination and reverse bias, the device achieves a responsivity of 19.82 A/W, a detectivity of 4.74 × 109 Jones, and an external quantum efficiency of 3048.32%. Notably, the GeSe/SnSe heterojunction photodetector also exhibits self-powered characteristics, with a responsivity of 0.11 mA/W and a detectivity of 5.44 × 106 Jones at zero bias voltage, accompanied by a fast response time of 23/61 ms (rise/fall). These findings underscore the effectiveness of the GeSe/SnSe heterojunction as a strategy for near-infrared photodetectors to simultaneously achieve low power consumption, high photoresponsivity, and self-powered photodetection, which is promising for optoelectronic device applications.

Two-dimensional GeS synthesized by one-step space-confined APCVD and its self-powered photodetector

Germanium sulfide (GeS) is a notable two-dimensional (2D) layered material that has gained attention across various research domains. However, challenges remain in realizing large areas of high-quality 2D GeS, despite the efforts made. Recently, we have successfully synthesized rectangular 2D single-crystal GeS flakes with a thickness of about 52 nm and a lateral length of 100 μm by one-step space-confined atmospheric pressure chemical vapor deposition (APCVD) using sulfur and germanium powders as raw materials. There is a direct relationship between the area size and the growth time. The further prepared GeS device has good photoresponsivity in the visible range. At 532 nm, it includes a responsivity of 40 mA/W, a detectivity of 8 × 108 Jones and a fast response time of 199 ms. In addition, the GeS device exhibits p-type conductive behavior and a unique self-powered effect. After prolonged storage, the GeS photodetector still exhibits good and stable photoswitching characteristics.