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This research investigates the controlled growth of borophene, a two-dimensional (2D) material composed of boron atoms arranged in atomically thin layers, using chemical vapor deposition (CVD) and explores its potential in supercapacitors. Borophene, similar to graphene, offers high electrical conductivity and tensile strength, making it a promising candidate for energy storage applications. However, synthesizing and stabilizing borophene structures in large areas remains a significant challenge, limiting its widespread adoption. Our study employs CVD to address these challenges, particularly in terms of controlling the thickness, crystallinity and uniformity. Key parameters in the growth process, such as reaction duration, temperature, precursor materials and ratios, carrier gases, and pressure, were optimized using copper substrates as catalysts. Thickness control ranging from approximately 0.9 nm to 9 nm with nearly full substrate coverage was achieved, demonstrating significantly improved uniformity compared to previous reports. These CVD grown borophene structures are employed as electrode materials for supercapacitors, achieving a specific areal capacitance of 44.5 mF cm−2 at a scan rate of 5 mV s−1 and a specific gravimetric capacitance of 4238 F g−1 at a scan rate of 5 mV s−1. This study reveals that borophene-based supercapacitors hold considerable potential due to their electrical and structural properties, characterized by high crystallinity and layered 2D structures that facilitate ion intercalation, indicating exceptional performance in future devices and applications. [ABSTRACT FROM AUTHOR]

One of the main problems faced by 2D materials used in supercapacitor applications when scaling up is restacking, such that their gravimetric capacitances become dramatically inferior to that of their monolayer forms. This study analyzes the Raman spectra of transferred layers of CVD-graphene revealing decoupling and rotational stacking of layers, with the potential of retention of intrinsic monolayer properties. Rotationally stacked layers have the potential to mitigate restacking and, thus, are capable of easing ion intercalation and boosting their performance in supercapacitor applications. In this pursuit, binder-free supercapacitors are fabricated out of chemical vapor deposited bilayer graphene, successively transferred to form rotationally stacked multilayers. Supercapacitors constructed with rotationally stacked four-layer graphene have an incredible specific gravimetric capacitance of 316.1 F g−1 at 1 mV s−1, with a corresponding energy density of 28.1 Wh kg−1 and ∼100% capacitance retention at 10 000 cycles. [ABSTRACT FROM AUTHOR]

MXenes combine distinctive properties, including high electrical conductivity, high thermal conductivity, and efficient absorption of electromagnetic waves, which allow them to be utilized in various applications such as electrical energy storage, sensors, and functional composites. This study aims to grow thin and large area M o 2 C flakes in a controlled manner by using chemical vapor deposition, avoiding surface functionalization, and limited lateral dimensions. Herein, we investigate the effects of C H 4 flow, the precursor/catalyst (Mo/Cu) ratio, and flow rates of carrier gas on the growth of two-dimensional M o 2 C structures. This study examines the effects of the precursor/catalyst (Mo/Cu) ratio and flow rates of carrier gas on the growth of M o 2 C structures. Our results show that when the flow rates of C H 4 , catalyst/precursor (Cu/Mo) ratio, and carrier gas ( N 2 / H 2 ) ratio are varied, we can control both thickness (from 7 to 145 nm) and coverage of the substrate surface (from 11% to 68%) of the M o 2 C flakes. Therefore, this study reveals that it is possible to realize centimeter-scale surface coverage and controllable thicknesses by adjusting the process parameters. The deposited films and flakes are analyzed by optical microscopy, atomic force microscopy, and Raman scattering spectroscopy techniques. The Raman spectra are also compared with the theoretical calculations using density functional theory. Overall, the present work is expected to provide a significant impact for utilization of MXenes in various applications. [ABSTRACT FROM AUTHOR]

Molybdenum disulfide (MoS2) and molybdenum carbide (Mo2C) are 2D materials with unique properties that make them suitable for electronic and optoelectronic applications. MoS2 is known for its high optical quantum yield and strong light–matter interaction, while Mo2C has metallic properties and is a member of the relatively new class of 2D materials called MXenes. In this research, a new heterostructure is obtained by growing MoS2 directly on Mo2C for the first time using chemical vapor deposition method. This novel hybrid structure changes the interlayer interaction and excited‐state dynamics, thereby increasing material diversity. The structure is characterized using Raman spectroscopy and atomic force microscopy, while photoluminescence (PL) and fluorescence lifetime imaging microscopy measurements are used to examine exciton motions. This study shows that the thickness of the hybrid structure is directly proportional to the frequency difference between the E2g and A1g modes, and inversely proportional to the PL intensities. The hybrid structure displays distinct exciton transitions due to the metallic effect and a longer fluorescence lifetime when compared to the bare monolayer of MoS2. The introduction of this novel hybrid structure with its optical properties holds great potential in opening up new avenues for optoelectronic device applications. [ABSTRACT FROM AUTHOR]

[Al.sub.2][O.sub.3] and [Al.sub.2][O.sub.3]:[Er.sup.3+] waveguides are prepared by a reliable, low-cost and reproducible reactive cosputtering process and their optical and spectroscopic properties are examined. The gain measurements over 6.4-cm propagation length in a 700-nm-thick [Al.sub.2][O.sub.3]:[Er.sup.3+] channel waveguide has resulted in net optical gain over a 41-nm wide wavelength range with a maximum of 5.4 dB at 1533 nm.

A phototransistor built by the assembly of 2D colloidal semiconductor quantum wells (CQWs) on a single layer of 2D transition metal dichalcogenide (TMD) is displayed. This hybrid device architecture exhibits high efficiency in Förster resonance energy transfer (FRET) enabling superior performance in terms of photoresponsivity and detectivity. Here, a thin film of CdSe/CdS CQWs acts as a sensitizer layer on top of the MoS2 monolayer based field‐effect transistor, where this CQWs–MoS2 structure allows for strong light absorption in CQWs in the operating spectral region and strong dipole‐to‐dipole coupling between MoS2 and CQWs resulting in enhanced photoresponsivity of one order of magnitude (11‐fold) at maximum gate voltage (VBG = 2 V) and two orders of magnitude (≈ 5 × 102) at VBG = −1.5 V, and tenfold enhanced specific detectivity. The illumination power‐dependent characterization of this hybrid device reveals that the thin layer of CQWs dominates the photogating mechanism compared to the photoconductivity effect on detection performance. Such hybrid designs hold great promise for 2D‐material based photodetectors to reach high performance and find use in optoelectronic applications. [ABSTRACT FROM AUTHOR]

The use of thin polymer films in optical planar integrated optical circuits is rapidly increasing. Much interest, therefore, has been devoted to characterizing the optical and mechanical properties of thin polymer films. This study focuses on measuring the elasto-optical properties of three different polymers; polystyrene, polymethyl-methacrylate, and benzocyclobutane. The out-of-plane elastic modulus, refractive index, film thickness, and birefringence of thin polymer films were determined by means of the prism coupling technique. The effect of the applied stress on the refractive index and birefringence of the films was investigated. Three-dimensional finite element method analysis was used so as to obtain the principal stresses for each polymer system, and combining them with the stress dependent refractive index measurements, the elasto-optic coefficients of the polymer films were determined. It was found that the applied stress in the out-of-plane direction of the thin films investigated leads to negative elasto-optic coefficients, as observed for all the three thin polymer films. [ABSTRACT FROM AUTHOR]

Use of focused ion beam (FIB) as a nanostructuring platform for fast prototype device development in the area of photonics has been attracting a considerable interest. In this study, we report a systematic investigation of focused ion beam (FIB) induced Ga+ ion implantation in silicon on insulator (SOI) structures. The local implantation of Ga+ ions during milling is studied for a wide range of ion doses, ranging from about 1014 to 1017 ions/cm2, using X-ray photoelectron spectroscopy (XPS). Ion implantation is realized on identically sized areas for each dose by varying the FIB parameters such as dwell time and loop number. It is found that the most of the Ga+ is within the first 50 nm of Si. This suggests that it can be possible to potentially reduce optical losses caused by the ion implantation in any optical application. Methods such as thermal annealing and wet or dry chemical etching can result in removal of the 50 nm implanted layer of SOI, as a result removing the layer causing potentially high optical losses. [ABSTRACT FROM AUTHOR]

In this study, optical and electronic transport properties of chemical vapor deposition (CVD) grown 2D WS2 and MoS2 based transistors and photodetectors are investigated and compared in ambient air by using 2D flakes grown with the same CVD system. To assess the performance variations between these two materials and understand the underlying mechanisms, it is essential to utilize identical growth methods (i.e. using the same CVD system), identical substrate and dielectric materials with the identical device fabrication methods and geometries. Transistor devices fabricated out of these flakes are examined in terms of their field effective mobility, current ON/OFF ratio, and photoresponsivity. Our results show that the MoS2 based devices have higher mobility and photoresponsivity than the WS2 based devices. However, the hysteresis curve of WS2 based transistors is smaller when compared to that of MoS2 based transistors. The mobilities of MoS2 and WS2 are estimated from measurements as 1.45 and 0.98 cm2 V−1 s−1, respectively. The electronic transport performance of MoS2 based devices (FETs and photodetectors) are found to be unexpectedly better than the WS2 based devices in terms of effective carrier mobility and photoresponsivity at ambient atmosphere and temperature. Our results suggest that WS2 is more sensitive to ambient conditions in comparison to MoS2, in spite of its theoretically estimated superior performance. [ABSTRACT FROM AUTHOR]