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Abstract Chalcogenide perovskites, particularly BaZrS₃, hold promise for optoelectronic devices owing to their exceptional light absorption and inherent stability. However, thin films obtained at lower processing temperatures typically result in small grain sizes and inferior transport properties. Here we introduce an approach employing co-sputtering elemental Ba and Zr targets followed by CS₂sulfurization, with a judiciously applied NaF capping layer. NaF acts as a flux agent during sulfurization, leading to marked increase in grain size and improved crystallinity. This process results in near-stoichiometric films with enhanced photoresponse. Terahertz spectroscopy further reveals a carrier mobility more than two orders of magnitude higher than those obtained from field-effect transistor measurements, suggesting that bulk transport is limited by grain boundary scattering. Our results demonstrate flux-assisted sulfurization as an effective strategy to improve the crystallinity of chalcogenide perovskite thin films for optoelectronic applications. Graphical abstract 

Abstract In this study, we demonstrate a novel approach for synthesizing free‐standing and transferable polycrystalline diamond membranes (PCDm) to overcome these constraints, thus enabling a much wider spectrum of applications. Two types of PCDm cantilevers —Top‐Surface‐Up (TSU) and Bottom‐Surface‐Up (BSU) are fabricated, each with two different sets of dimensions: 150 µm (width) × 1200 µm (length) and 300 µm (width) × 2000 µm (length). Their mechanical and electrical properties are systematically investigated. Atomic Force Microscopy (AFM) analysis revealed that TSU‐PCDm has a higher elastic modulus than BSU‐PCDm, attributed to differences in grain size and defect distribution. Despite these differences, all PCDms in our work exhibit consistently high modulus values with minimal mechanical degradation across various cantilever geometries. Bandgap measurements using X‐ray Photoelectron Spectroscopy (XPS) and UV–vis absorption spectroscopy indicated a lower bandgap for TSU‐PCDm due to boron incorporation, while BSU‐PCDm exhibited a higher bandgap due to increased hydrogen content. Electrical characterization showed that the sheet resistance of TSU‐PCDm decreases under strain, whereas BSU‐PCDm maintains stable resistance. These findings unveil the material properties of PCDm and their potential usage for myriad diamond‐based electronic applications. 

Abstract In this paper, transient delayed rise and fall times for beta gallium oxide ( β -Ga 2 O 3 ) nanomembrane (NM) Schottky barrier diodes (SBDs) formed on four different substrates (diamond, Si, sapphire, and polyimide) were measured using a sub-micron second resolution time-resolved electrical measurement system under different temperature conditions. The devices exhibited noticeably less-delayed turn on/turn off transient time when β -Ga 2 O 3 NM SBDs were built on a high thermal conductive (high- k ) substrate. Furthermore, a relationship between the β -Ga 2 O 3 NM thicknesses under different temperature conditions and their transient characteristics were systematically investigated and verified it using a multiphysics simulator. Overall, our results revealed the impact of various substrates with different thermal properties and different β -Ga 2 O 3 NM thicknesses on the performance of β -Ga 2 O 3 NM-based devices. Thus, the high- k substrate integration strategy will help design future β -Ga 2 O 3 -based devices by maximizing heat dissipation from the β -Ga 2 O 3 layer. 

Abstract In this work, we report a simplified method to measure thermal conductivity from the typical Raman thermometry method by employing a much simpler dispersion relationship equation and the Debye function, instead of solving the heat equation. Unlike the typical Raman thermometry method, our new method only requires monitoring of the temperature-dependent Raman mode shifting without considering laser power-dependent Raman mode shifting. Thus, this new calculation method offers a simpler way to calculate the thermal conductivity of materials with great precision. As a model system, theβ-Ga₂O₃nanomembrane (NM) on a diamond substrate was prepared to measure thermal conductivity ofβ-Ga₂O₃NMs at different thicknesses (100 nm, 1000 nm, and 4000 nm). Furthermore, the phonon penetration depth was investigated to understand how deep phonons can be dispersed in the sample so as to guide the dimensional design parameter of the device from the thermal management perspective. 

In this paper, we demonstrated large-size free-standing single-crystal β-Ga 2 O 3 NMs fabricated by the hydrogen implantation and lift-off process directly from MOCVD grown β-Ga 2 O 3 epifilms on native substrates. The optimum implantation conditions were simulated with a Monte-Carlo simulation method to obtain a high hydrogen concentration with a narrow ion distribution at the desired depth. Two as grown β-Ga 2 O 3 samples with different orientations ([100] and [001]) were used to successfully create 1.2 μm thick β-Ga 2 O 3 NMs without any physical damage. These β-Ga 2 O 3 NMs were then transfer-printed onto rigid and flexible substrates such as SiC and polyimide substrates. Various material characterization studies were performed to investigate their crystal quality, surface morphologies, optical properties, mechanical properties, and bandgaps before and after the lift-off and revealed that the good material quality was maintained. This result offers several benefits in that the thickness, doping, and size of β-Ga 2 O 3 NMs can be fully controlled. Moreover, more advanced β-Ga 2 O 3 -based NM structures such as (Al x Ga 1−x ) 2 O 3 /Ga 2 O 3 heterostructure NMs can be directly created from their bulk epitaxy substrates; thus this study provides a viable route for the realization of high performance β-Ga 2 O 3 NM-based electronics and optoelectronics that can be built on various substrates and platforms. 

Theβ-Ga₂O₃nanomembrane (NM)/diamond heterostructure is one of the promising ultra-wide bandgap heterostructures that offers numerous complementary advantages from both materials. In this work, we have investigated the thermal properties of theβ-Ga₂O₃NM/diamond heterostructure with three different thicknesses ofβ-Ga₂O₃nanomembranes (NMs), namely 100 nm, 1000 nm, and 4000 nm thickβ-Ga₂O₃NMs using Raman thermometry. The thermal property—temperature relationships of theseβ-Ga₂O₃NM/diamond heterostructures, such as thermal conductivity and interfacial thermal boundary conductance were determined under different temperature conditions (from 100 K to 500 K with a 40 K interval). The result provides benchmark knowledge about the thermal conductivity ofβ-Ga₂O₃NMs over a wide temperature range for the design of novelβ-Ga₂O₃-based power electronics and optoelectronics.