arXiv subjects

Jinwoo Hwang

Publications and source records attributed to Jinwoo Hwang.

At least 19 recordsLinked to original sources

arXiv2026

Coordination-Sensitive Nanoscale Analysis of Defect-Driven Phase Transformation in Si-Doped (AlXGa1-X)2O3

Defect-driven phase instability critically influences the structural reliability of ultrawide bandgap oxides, yet direct nanoscale metrics linking local chemistry to structural transformation remain limited. Here, we introduce a coordination-sensitive atom probe tomography framework that quantitatively resolves reductions in local cation coordination and links them directly to defect-driven phase transformation. Using Si-doped beta-(AlxGa1-x)2O3 heterostructures with controlled Al composition (6-17%) and doping levels (10^17-10^20 cm^-3), we show that gamma-phase inclusions emerge exclusively under the combined conditions of elevated Al content and heavy Si doping. Two-dimensional compositional mapping reveals pronounced lateral Al/Ga inhomogeneity in these regions, while nearest-neighbor and radial distribution analyses quantitatively resolve a significant reduction in first-shell Ga coordination, consistent with local cation deficiency. Correlative scanning transmission electron microscopy confirms that these coordination-depleted regions coincide spatially with gamma-phase inclusions. Density functional theory further supports this mechanism, demonstrating that Al incorporation reduces monoclinic lattice stability and, in conjunction with donor-induced vacancy formation, facilitates vacancy-mediated cation rearrangement and coordination collapse. Together, these results establish coordination loss as a measurable nanoscale signature directly linked to defect-driven phase instability. This framework provides a generalizable approach for probing defect-driven phase instability in doped and alloyed ultrawide bandgap semiconductors.

cond-mat.mtrl-sci↗

arXiv2026

From pore collapse to crystal growth: ultrafast laser-induced stishovite formation in nanoporous silica

The crystallization of amorphous solids under ultrafast laser irradiation represents a paradigm of non-equilibrium phase transitions, where the interplay between electromagnetic energy localization and atomic-scale dynamics remains largely uncharted. By using a multiscale framework that couples finite-difference time-domain simulations of nonlinear femtosecond laser pulse propagation with molecular dynamics of the atomic response, we demonstrate that field enhancement around the pores of nanoporous amorphous silica confines laser energy and drives rapid pore collapse. In nanoporous silica, the enhanced local electromagnetic field leads to stronger energy absorption compared with smaller-pore and homogeneous systems. This heterogeneous energy localization provides preferential nucleation sites within the dense glass network, leading to ultrafast formation of stishovite on a sub-nanosecond timescale, faster than in homogeneous silica. This accelerated crystallization can outpace pressure relaxation making the transition to a high-pressure phase possible. These results are confirmed by experimental observations of femtosecond-laser-induced crystallization in confined geometries, and show that electromagnetic hotspots in nanoporous glass structures can be tailored to control solid-state transformations.

cond-mat.mtrl-sci↗

arXiv2026

Microwave Performance of all MOCVD-grown AlScN/GaN MIS-HEMTs on Semi-Insulating GaN Substrates

We report on the design, fabrication, and characterization of all MOCVD-grown long-gate AlScN/GaN metal-insulator-semiconductor high electron mobility transistors (MIS-HEMTs) on semi-insulating GaN substrates. Devices with a gate length of $1~μ$m and gate-drain spacing of $0.9~μ$ m exhibit a maximum drain current density of 1 A/mm, an on/off current ratio of $2\times 10^5$, and a three-terminal breakdown voltage of 63 V. The device has near-ideal subthreshold characteristics with a subthreshold swing of 63 mV/dec and a current dispersion as low as 7.8$\%$ at 10 V due to the excellent interfacial quality with a trap density ($D_\mathrm{it}$) of $2.11\times{10}^{11}~\mathrm{cm}^{-2}eV^{-1}$ and the semi-insulating GaN substrate with a low threading dislocation density. Small-signal RF measurements reveal an $f_\mathrm{T}/f_\mathrm{max}$ of 25.8/51.1 GHz, while large-signal load-pull characterization at 10 GHz demonstrates an output power density of 4.04 W/mm with a power-added efficiency of 22.7$\%$. In addition, a minimum noise figure below 2.5 dB was measured over a wide drain current range from 100 mA/mm to 700 mA/mm below 6 GHz. These results extend previous demonstrations of short-gate MOCVD-grown AlScN/GaN HEMTs to the long-gate, high-voltage regime, confirming the robustness of this material system for both high-frequency and high-power device applications with favorable microwave noise performance.

physics.app-ph↗

arXiv2026

Stabilizing Magnetic Bubble Domains in Epitaxial 2D Magnet/Topological Insulator Heterostructures through Interfacial Interactions

Epitaxial heterostructures of two-dimensional van der Waals magnets and topological insulators offer a powerful platform for probing interfacial spin interactions that govern magnetic textures in low-dimensional quantum systems, while simultaneously enabling highly efficient, atomically thin spin-orbit-torque memory and computing architectures. Despite this promise, the fundamental role of these interfacial interactions in determining magnetic domain-phase stability remain largely uncharted. Here, we perform scanning transmission X-ray microscopy to image nanoscale magnetic textures in epitaxial Fe3GeTe2 Bi2Te3 heterostructures, enabled by a thermal-release-tape dry transfer process onto X-ray transparent silicon-rich nitride membranes. Under zero-field-cooled conditions, we observe robust bubble domain phases from 75 to 165 K, and across different number of folds of the multilayer Fe3GeTe2 Bi2Te3 heterostructures. This is in stark contrast with exfoliated single-crystal Fe3GeTe2 flakes, where ZFC stripe domains are observed for flakes thicker than 20 nm and no domains have been reported for thin flakes less than 15 nm. First-principles calculations and micromagnetic simulations reveal that interfacial coupling to Bi2Te3 modifies the magnetic anisotropy and introduces interfacial Dzyaloshinskii-Moriya interaction, shifting the magnetic phase space towards bubble-domain stabilization without field-cooling. Together, our results offer a new strategy for phase-selective control of magnetic domains through interfacial engineering.

cond-mat.mtrl-sci↗

arXiv2026

Mimicking the earth core conditions with ultrafast laser materials interaction

Ultrafast lasers create extreme, non-equilibrium thermodynamic conditions that can transiently reach pressures and temperatures comparable to interior core of the earth. Here we show that femtosecond excitation of amorphous silica-hafnia multilayer dielectrics drives the formation of high-pressure crystalline phases of silica including stishovite, seifertite, and the pyrite-type high density structure, within confined subsurface regions.Using TEM, SAED, and 4D-STEM, we directly map nanoscale phase evolution and identify crystalline motifs embedded inside laser generated blisters.Complementary molecular dynamics simualtions reveal the thermodynamic pathway underlying these transformations, where rapid electronic pressure initiates densification and octahedral coordination, followed by temperature driven crystallization and displacive transitions during ultrafast quenching. The resulting polymorphs reflects a dual-stage pathway inaccessible under equilibrium processing. Our results establish femtosecond laser excitation as a viable route to synthesize and stabilize ultrahigh-density high pressure silica phases under ambient conditions, without a diamond anvil cell, with implications for laser-damage mechanisms, high-energy-density materials, and planetary physics.

cond-mat.mtrl-sci↗

arXiv2026

Understanding the Performance Behaviors of End-to-End Protein Design Pipelines on GPUs

Recent computational advances enable protein design pipelines to run end-to-end on GPUs, yet their heterogeneous computational behaviors remain undercharacterized at the system level. We implement and profile a representative pipeline at both component and full-pipeline granularities across varying inputs and hyperparameters. Our characterization identifies generally low GPU utilization and high sensitivity to sequence length and sampling strategies. We outline future research directions based on these insights and release an open-source pipeline and profiling scripts to facilitate further studies.

cs.ET↗

arXiv2025

Neo: Real-Time On-Device 3D Gaussian Splatting with Reuse-and-Update Sorting Acceleration

3D Gaussian Splatting (3DGS) rendering in real-time on resource-constrained devices is essential for delivering immersive augmented and virtual reality (AR/VR) experiences. However, existing solutions struggle to achieve high frame rates, especially for high-resolution rendering. Our analysis identifies the sorting stage in the 3DGS rendering pipeline as the major bottleneck due to its high memory bandwidth demand. This paper presents Neo, which introduces a reuse-and-update sorting algorithm that exploits temporal redundancy in Gaussian ordering across consecutive frames, and devises a hardware accelerator optimized for this algorithm. By efficiently tracking and updating Gaussian depth ordering instead of re-sorting from scratch, Neo significantly reduces redundant computations and memory bandwidth pressure. Experimental results show that Neo achieves up to 10.0x and 5.6x higher throughput than state-of-the-art edge GPU and ASIC solution, respectively, while reducing DRAM traffic by 94.5% and 81.3%. These improvements make high-quality and low-latency on-device 3D rendering more practical.

cs.AR↗

arXiv2025

Band Alignment Tuning from Charge Transfer in Epitaxial SrIrO$_3$/SrCoO$_3$ Superlattices

Understanding charge transfer at oxide interfaces is crucial for designing materials with emergent electronic and magnetic properties, especially in systems where strong electron correlations and spin-orbit coupling coexist. SrIrO$_3$/SrCoO$_3$ (SIO/SCO) superlattices offer a unique platform to explore these effects due to their contrasting electronic structures and magnetic behaviors. Building on past theory based on continuity of O 2p band alignment, we employ density functional theory (DFT) to model electron transfer from Ir to Co across the SIO/SCO interface. To characterize these effects, we synthesized epitaxial SIO/SCO superlattices via molecular beam epitaxy. Structural and transport measurements confirmed high crystallinity, metallic behavior, and suppression of Kondo scattering that has been reported in uniform SIO films. Further characterization via X-ray absorption spectroscopy (XAS) revealed orbital anisotropy and valence changes consistent with interfacial charge transfer. Co K- and L$_{2,3}$-edge and Ir L$_2$-edge spectra verified electron donation from Ir to Co, stabilizing the perovskite SCO phase and tuning the electronic structure of SIO via hole-doping. O K-edge XAS showed band alignment shifts in the SIO layer consistent with DFT predictions. Our work here provides a pathway for engineering oxide heterostructures with tailored magnetic and electronic properties.

cond-mat.mtrl-sci↗

arXiv2025

Broad-Range Tuning of Ferroelectric Switching of LaxBi1-xFeO3 Epitaxial Films via Digital Doping using Off-Axis Co-Sputtering

To investigate the scope of ferroelectric behavior in La-substituted BiFeO3 films, LaxBi1-xFeO3 epitaxial films were synthesized using off-axis co-sputtering on SrTiO3(001) and DyScO3(110) substrates with a SrRuO3 bottom electrode layer. A digital-doping deposition method was used to enable precise control and continuous tuning of La concentration in high-quality LaxBi1-xFeO3 films across a wide range of x = 0.05-0.60, which was systematically investigated using piezoresponse force microscopy. Robust and reversible out-of-plane ferroelectric switching has been observed up to x = 0.35, while films with x $\geq$ 0.37 exhibit no measurable ferroelectric behavior, indicating a sharp ferroelectric-to-paraelectric phase transition between x = 0.35 and 0.37. This represents the highest reported La concentration in LaxBi1-xFeO3 films that retains ferroelectric ordering, highlighting opportunities to engineer ferroelectric and multiferroic properties in complex oxide heterostructures.

cond-mat.mtrl-sci↗

arXiv2025

Pimba: A Processing-in-Memory Acceleration for Post-Transformer Large Language Model Serving

Transformers are the driving force behind today's Large Language Models (LLMs), serving as the foundation for their performance and versatility. Yet, their compute and memory costs grow with sequence length, posing scalability challenges for long-context inferencing. In response, the algorithm community is exploring alternative architectures, such as state space models (SSMs), linear attention, and recurrent neural networks (RNNs), which we refer to as post-transformers. This shift presents a key challenge: building a serving system that efficiently supports both transformer and post-transformer LLMs within a unified framework. To address this challenge, we analyze the performance characteristics of transformer and post-transformer LLMs. Despite their algorithmic differences, both are fundamentally limited by memory bandwidth under batched inference due to attention in transformers and state updates in post-transformers. Further analyses suggest two additional insights: (1) state update operations, unlike attention, incur high hardware cost, making per-bank PIM acceleration inefficient, and (2) different low-precision arithmetic methods offer varying accuracy-area tradeoffs, while we identify Microsoft's MX as the Pareto-optimal choice. Building on these insights, we design Pimba as an array of State-update Processing Units (SPUs), each shared between two banks to enable interleaved access to PIM. Each SPU includes a State-update Processing Engine (SPE) that comprises element-wise multipliers and adders using MX-based quantized arithmetic, enabling efficient execution of state update and attention operations. Our evaluation shows that, compared to LLM-optimized GPU and GPU+PIM systems, Pimba achieves up to 4.1x and 2.1x higher token generation throughput, respectively.

cs.AR↗

arXiv2025

Déjà Vu: Efficient Video-Language Query Engine with Learning-based Inter-Frame Computation Reuse

Recently, Video-Language Models (VideoLMs) have demonstrated remarkable capabilities, offering significant potential for flexible and powerful video query systems. These models typically rely on Vision Transformers (ViTs), which process video frames individually to extract visual embeddings. However, generating embeddings for large-scale videos requires ViT inferencing across numerous frames, posing a major hurdle to real-world deployment and necessitating solutions for integration into scalable video data management systems. This paper introduces Déjà Vu, a video-language query engine that accelerates ViT-based VideoLMs by reusing computations across consecutive frames. At its core is ReuseViT, a modified ViT model specifically designed for VideoLM tasks, which learns to detect inter-frame reuse opportunities, striking an effective balance between accuracy and reuse. Although ReuseViT significantly reduces computation, these savings do not directly translate into performance gains on GPUs. To overcome this, Déjà Vu integrates memory-compute joint compaction techniques that convert the FLOP savings into tangible performance gains. Evaluations on three VideoLM tasks show that Déjà Vu accelerates embedding generation by up to a 2.64x within a 2% error bound, dramatically enhancing the practicality of VideoLMs for large-scale video analytics.

cs.DC↗

arXiv2025

Thermal Annealing and Radiation Effects on Structural and Electrical Properties of NbN/GaN Superconductor/Semiconductor Junction

In the rapidly evolving field of quantum computing, niobium nitride (NbN) superconductors have emerged as integral components due to their unique structural properties, including a high superconducting transition temperature (Tc), exceptional electrical conductivity, and compatibility with advanced device architectures. This study investigates the impact of high-temperature annealing and high-dose gamma irradiation on the structural and superconducting properties of NbN films grown on GaN via reactive DC magnetron sputtering. The as-deposited cubic δ-NbN (111) films exhibited a high-intensity XRD peak, high Tc of 12.82K, and an atomically flat surface. Annealing at 500 and 950 °C for varying durations revealed notable structural and surface changes. High-resolution STEM indicated improved local ordering, while AFM showed reduced surface roughness after annealing. XPS revealed a gradual increase in the Nb/N ratio with higher annealing temperatures and durations. High-resolution XRD and STEM analyses showed lattice constant modifications in δ-NbN films, attributed to residual stress changes following annealing. Additionally, XRD phi-scans revealed sixfold symmetry in NbN films due to rotational domains relative to GaN. While Tc remained stable after annealing at 500 °C, increasing the annealing temperature to 950 °C degraded Tc to ~8K and reduced the residual resistivity ratio from 0.85 in as-deposited films to 0.29 after 30 minutes. The effects of gamma radiation (5 Mrad (Si)) were also studied, demonstrating minimal changes to crystallinity and superconducting performance, indicating excellent radiation resilience. These findings highlight the potential of NbN superconductors for integration into advanced quantum devices and their suitability for applications in radiation-intensive environments such as space, satellites, and nuclear power plants.

cond-mat.supr-con↗

arXiv2025

Electrical and Structural Properties of In-Situ MOCVD Grown Al$_2$O$_3$/$β$-Ga$_2$O$_3$ and Al$_2$O$_3$/$β$-(Al$_x$Ga$_{1-x}$)$_2$O$_3$ MOSCAPs

This study investigates the electrical and structural properties of MOSCAPs with in-situ MOCVD-grown Al$_2$O$_3$ dielectrics on (010) $β$-Ga$_2$O$_3$ and $β$-(Al$_x$Ga$_{1-x}$)$_2$O$_3$ films. The Al$_2$O$_3$/$β$-Ga$_2$O$_3$ MOSCAPs showed a strong dependence on Al$_2$O$_3$ deposition temperature. At 900$^\circ$C, reduced voltage hysteresis ($\sim$0.3 V) and improved reverse breakdown voltage (74.5 V) were observed, with breakdown fields of 5.01 MV/cm in Al$_2$O$_3$ and 4.11 MV/cm in $β$-Ga$_2$O$_3$. At 650$^\circ$C, higher hysteresis ($\sim$3.44 V) and lower reverse breakdown voltage (38.8 V) were observed, with breakdown fields of 3.69 MV/cm in Al$_2$O$_3$ and 2.87 MV/cm in $β$-Ga$_2$O$_3$. However, forward breakdown fields improved from 5.62 MV/cm (900$^\circ$C) to 7.25 MV/cm (650$^\circ$C). STEM revealed improved crystallinity and sharper interfaces at 900$^\circ$C, enhancing reverse breakdown performance. For Al$_2$O$_3$/$β$-(Al$_x$Ga$_{1-x}$)$_2$O$_3$ MOSCAPs, increasing Al composition ($x$ = 5.5\% to 9.2\%) reduced carrier concentration and improved reverse breakdown fields from 2.55 to 2.90 MV/cm in $β$-(Al$_x$Ga$_{1-x}$)$_2$O$_3$ and 2.41 to 3.13 MV/cm in Al$_2$O$_3$. Forward breakdown fields in Al$_2$O$_3$ improved from 5.0 to 5.4 MV/cm as Al composition increased. STEM confirmed compositional homogeneity and excellent stoichiometry of Al$_2$O$_3$ and $β$-(Al$_x$Ga$_{1-x}$)$_2$O$_3$ layers. These findings highlight the robust electrical performance, high breakdown fields, and structural quality of Al$_2$O$_3$/$β$-Ga$_2$O$_3$ and Al$_2$O$_3$/$β$-(Al$_x$Ga$_{1-x}$)$_2$O$_3$ MOSCAPs for high-power applications.

physics.app-ph↗

arXiv2025

MixDiT: Accelerating Image Diffusion Transformer Inference with Mixed-Precision MX Quantization

Diffusion Transformer (DiT) has driven significant progress in image generation tasks. However, DiT inferencing is notoriously compute-intensive and incurs long latency even on datacenter-scale GPUs, primarily due to its iterative nature and heavy reliance on GEMM operations inherent to its encoder-based structure. To address the challenge, prior work has explored quantization, but achieving low-precision quantization for DiT inferencing with both high accuracy and substantial speedup remains an open problem. To this end, this paper proposes MixDiT, an algorithm-hardware co-designed acceleration solution that exploits mixed Microscaling (MX) formats to quantize DiT activation values. MixDiT quantizes the DiT activation tensors by selectively applying higher precision to magnitude-based outliers, which produce mixed-precision GEMM operations. To achieve tangible speedup from the mixed-precision arithmetic, we design a MixDiT accelerator that enables precision-flexible multiplications and efficient MX precision conversions. Our experimental results show that MixDiT delivers a speedup of 2.10-5.32 times over RTX 3090, with no loss in FID.

cs.AR↗

arXiv2025

Optimizing Metal-Organic Chemical Vapor Deposition for Ultrawide Band-Gap MgSiN2 Thin Films

Orthorhombic II-IV nitride semiconductors offer an expanded and more tunable material set with unique properties, while maintaining close compatibility with the wurtzite crystal structure of the III-nitrides. In particular, MgSiN2, a II-IV nitride closely lattice matched to GaN and AlN has a band gap suitable for photonic applications in the UV-C wavelength region. MgSiN2 is also a promising candidate to exhibit ferroelectricity, which has only been observed in very few nitride materials. This study builds on our previous work on the metal-organic chemical vapor deposition (MOCVD) of MgSiN2 thin films grown on GaN-on-sapphire and c-plane sapphire substrates by exploring higher growth temperature windows, resulting in higher crystalline quality and improved interfaces. Correlations between the growth conditions (Mg:Si precursor molar flow rate ratio, reactor pressure, and growth temperatures from 900C to 960C) and the resultant film quality are investigated for films grown on GaN-on-sapphire. High-resolution transmission electron microscopy (HR-TEM) reveals high-quality orthorhombic single-crystal MgSiN2, confirming successful epitaxial growth on GaN. Optical transmittance measurements indicate the direct band gap is 6.34-6.36 eV and indirect band gap is 5.77-5.81 eV, affirming the realization of an ultrawide-band gap II-IV nitride semiconductor that is structurally compatible with existing III-nitride device platforms.

cond-mat.mtrl-sci↗

arXiv2025

Metal-organic chemical vapor deposition of MgGeN2 films on GaN and sapphire

MgGeN2 films were synthesized using metal-organic chemical vapor deposition on GaN/c-sapphire templates and c-plane sapphire substrates. Energy-dispersive X-ray spectroscopy was used to estimate the cation composition ratios. To mitigate magnesium evaporation, the films were grown at pyrometer temperature 745 °C with a wafer rotation speed of 1000 rpm. Growth rates were determined by fitting energy-dispersive X-ray spectroscopy spectra to film thicknesses using NIST DTSA-II software. The thickness estimates determined by this method were consistent with scanning transmission electron microscopy measurements done for selected samples. Scanning electron microscopy images revealed faceted surfaces indicative of a tendency toward three-dimensional growth. X-ray diffraction spectra confirmed that the films were highly crystalline and exhibited preferential orientation in alignment with the substrate. Atomic force microscopy measurements show that film thicknesses are consistent across samples grown on both GaN templates and sapphire substrates, with typical roughnesses around 10 nm. Transmittance spectra of films grown on double-side-polished sapphire substrates yielded band gaps of 4.28 +- 0.06 eV for samples exhibiting close-to-ideal stoichiometry. Comparison of the measured spectra with ab initio calculations are in good agreement both near the band gap and at higher energies where excitation is into higher-lying bands. These findings provide insight into the growth and characterization of MgGeN2, contributing to the development of this material for potential applications in optoelectronics and power electronics.

cond-mat.mtrl-sci↗

arXiv2025

Metal-organic chemical vapor deposition of MgSiN$_{2}$ thin films

Orthorhombic-structured II-IV nitrides provide a promising opportunity to expand the material platform while maintaining compatibility with the wurtzite crystal structure of the traditional III-nitride material system. Among them, MgSiN$_{2}$ stands out due to its close compatibility with GaN and AlN and its theoretically predicted ultrawide direct band gap of 6.28 eV. In this work, the growth of MgSiN$_{2}$ thin films on GaN-on-sapphire and c-plane sapphire substrates was investigated using metal-organic chemical vapor deposition (MOCVD). MOCVD growth conditions were correlated with film quality and crystallinity for samples grown on GaN-on-sapphire substrates. The effects of Mg:Si precursor molar flow rate ratios and growth pressure at two different temperatures, 745$^{\circ}$C and 850$^{\circ}$C, were studied comprehensively. High-resolution scanning transmission electron microscopy (STEM) imaging confirmed the formation of high-quality, single-crystal MgSiN$_{2}$ films. Optical band gap extraction from transmittance measurements yielded direct band gap values ranging from 6.13 eV to 6.27 eV for samples grown under various conditions, confirming the realization of an ultrawide-band gap, III-nitride-compatible, II-IV-nitride material.

cond-mat.mtrl-sci↗

arXiv2025

MOCVD growth and band offsets of \k{appa}-phase Ga2O3 on sapphire, GaN, AlN and YSZ substrates

Epitaxial growth of \k{appa}-phase Ga2O3 thin films are investigated on c-plane sapphire, GaN- and AlNon-sapphire, and (100) oriented yttria stabilized zirconia (YSZ) substrates via metalorganic chemical vapor deposition (MOCVD). The structural and surface morphological properties are investigated by comprehensive material characterization. Phase pure \k{appa}-Ga2O3 films are successfully grown on GaN-, AlN-on sapphire, and YSZ substrates through a systematical tuning of the growth parameters including the precursor molar flow rates, chamber pressure and growth temperature, whereas the growth on c-sapphire substrates leads to a mixture of \b{eta}- and \k{appa}polymorphs of Ga2O3 under the investigated growth conditions. The influence of the crystalline structure, surface morphology and roughness of \k{appa}-Ga2O3 films grown on different substrates are investigated as a function of precursor flow rate. High resolution scanning transmission electron microscopy (HR-STEM) imaging of \k{appa}-Ga2O3 films reveals abrupt interfaces between the epitaxial film and the sapphire, GaN and YSZ substrates. The growth of single crystal orthorhombic \k{appa}Ga2O3 films is confirmed by analyzing the STEM nano-diffraction pattern. The chemical composition, surface stoichiometry, and the bandgap energies of \k{appa}-Ga2O3 thin films grown on different substrates are studied by high resolution x-ray photoelectron spectroscopy (XPS) measurements. The type-II (staggered) band alignments at three interfaces between \k{appa}-Ga2O3 and c-sapphire, AlN, and YSZ substrates are determined by XPS, with the exception of \k{appa}-Ga2O3/GaN interface, which shows type I (straddling) band alignment.

cond-mat.mtrl-sci↗