Strain modulation in 2D GaSe epitaxial films by substrate engineering via molecular beam epitaxy (MBE)

Analyzing the impact of Se concentration during the molecular beam epitaxy deposition of 2D SnSe with atomistic-scale simulations and explainable machine learning

The efficacy of metal‐organic chemical vapor deposition (MOCVD)‐based growth for the production of GaAs‐on‐Si virtual substrates following a recently reported process combining low‐temperature growth, thermal cyclic annealing (TCA), and an asymmetric step‐graded filter (ASG) structure is investigated. The impact of multiple process variables—substrate offcut, V/III molecular flux ratio, growth rate, and growth and annealing temperatures—with respect to resultant surface roughness ( R q ) and threading dislocation density (TDD) is examined. Similar trends as those reported for the original molecular beam epitaxy‐based process are observed in R q and TDD for growths on both 2° and 6° offcut substrates. MOCVD process conditions are established for a reduced‐thickness design yielding GaAs virtual substrates on 2° and 6° offcut Si with TDD (≤4.0 × 10 6 cm −2 ) and R q (2.4 and 5.3 nm, respectively), comparable to conventional graded buffers, but with a total III–V thickness of less than 2.0 µm.

First-principles insights into the incorporation of arsenic in BaSi2 thin films grown by molecular beam epitaxy

Growth and oxidation of ultra-thin Pt-Sn layers on Pt(111) by molecular and atomic oxygen.

Quantum state-selective detection of reaction products with vacuum ultraviolet (VUV) and extreme ultraviolet (XUV) light is crucial for understanding gas-phase reaction dynamics. However, existing VUV/XUV generation methods often face challenges with non-selective ionization from third-harmonic generation (THG) and limitations in beam separation. Presented here is a noncollinear four-wave mixing scheme that spatially separates the generated sum-frequency generation laser beam from the THG and fundamental input laser beams. This is achieved through independent and automated control of two focusing lenses, allowing flexible adjustment of each input laser's focal length. This enables precise control over focal positions and crossing angles, facilitating optimal spatial overlap despite significant wavelength differences, and critically, permits broad-range XUV scanning for state-selective ionization of diverse reaction products across multiple quantum states. The efficacy of this design is demonstrated through resonance-enhanced multiphoton ionization spectra of HF and N2, which show agreement with simulations. Furthermore, comparative velocity map images from inelastic scattering experiments unequivocally prove this noncollinear configuration effectively rejects THG, enabling sharply resolved state-selective product detection. This robust method enhances capabilities for detailed molecular beam investigations requiring stringent product quantum state selectivity across a wide range of species and quantum states.

Tin-mediated phase-controlled growth of γ-InSe thin films on Si (100) via molecular beam epitaxy

ABSTRACT Polycyclic aromatic hydrocarbons (PAHs) offer a unique platform for bridging molecular design and nanoscale functionality owing to their tunable structures. Beyond their intrinsic electronic properties, PAHs exhibit significant potential for directed self‐assembly, enabling the formation of ordered nanostructures with tailored functionalities. Here, we report the on‐surface self‐assembly of quantum dot‐like nanostructures and nanoribbons from two closely related PAH molecules, C₉₆H 2 4 (C₁ 2 H 2 5 )₆ (C96‐A) and C₉₆H 3 ₀ (C96), deposited on Au(111) via molecular beam epitaxy. Scanning tunneling microscopy and spectroscopy (STM/STS) reveal a structural evolution from ordered single molecules to extended nanoribbons, with the latter exhibiting a narrow electronic bandgap of 0.8 eV. X‐ray photoelectron spectroscopy (XPS) indicates a single carbon chemical environment, while near‐edge X‐ray absorption fine structure (NEXAFS) spectroscopy confirms a flat‐lying molecular orientation. Density functional theory (DFT) calculations corroborate the experimental findings and provide insight into the self‐assembly mechanisms. These results highlight the potential of engineered PAHs for the bottom‐up fabrication of nanoscale electronic materials.

1. Background and purpose Germanene is two-dimensional (2D) honeycomb crystal of Ge atoms and one of the candidate materials for next-generation electric devices because it has high carrier mobility and topological insulation. Among the various formation methods of germanene proposed [1-3], we focus on the formation of Ge ultra-thin crystals on Al/Ge(111) by segregation and diffusion phenomena [4]. Furthermore, developing a new technique combining this method with a transfer technique was attempted toward the electrical characterization of Ge ultra-thin crystals [5]. In applying the transfer process, the preparation of high-quality heteroepitaxial Ge layer on a Si(111) substrate is important from the viewpoints of reducing costs and large area formation. In this study, we focused on a sputtering method from the above perspective, and there have been no reports on processes for growing high-quality heteroepitaxial Ge on Si(111) substrates. 2.Experiments We performed the Ge heteroepitaxial growth on n-type Si(111) substrates using a sputtering method by a two-step growth method based on a previous report on molecular beam epitaxy growth case [6]. The surface chemical cleaning of Si(111) substrate was performed using 1% diluted hydro fluoride and de-ionized water. Then, Si(111) wafer was annealed at 350°C of the substrate temperature (T sub) for 30 min. After that, we decreased T sub to 320°C and performed the epitaxial growth of Ge(111) layer with a thickness of 10, 40, and 70 nm. We call this first Ge(111) layer grown at T sub = 320°C as LT-Ge(111). Then, T sub was increased to 550°C and Ge(111) was epitaxially grown. This Ge(111) buffer layer grown at T sub = 550°C is called HT-Ge(111). The HT-Ge(111) thickness was designed so that a total Ge thickness of HT- and LT-Ge(111) layers was approximately 1 μm. We also fabricated only HT-Ge(111) layer (without LT-Ge(111) process).We performed Raman spectroscopy and photoluminescence (PL) measurements for the physical evaluation of the Ge(111) layer. A Raman spectrometer with a focal length of 2,000 mm and high-wavenumber resolution was adopted. A visible laser was used as the excitation light source, whose wavelength was 532 nm. The PL measurement setup was equipped with an extended InGaAs diode array detector (wavelength range: from 0.9 to 2.2 μm). The sample stage temperature of the spectrometer can be controlled between 4 and 300 K with a helium compressor and a heater device. A visible laser was used as the excitation light source, whose wavelength was 532 nm. The relatively wide slit of 100 µm enabled obtaining a high PL intensity with a wavelength resolution of approximately 4 nm. 3. Results and discussion Figure 1 shows the LT-Ge(111) thickness dependence of linewidth for Raman spectra of Ge-Ge vibration mode. As a result, we found that the Raman spectra are gradually broadened as the LT-Ge(111) thickness is increased. This is considered to reflect an increase in the defect density or the strain distribution of HT-Ge(111) layer due to the increase in the LT-Ge(111) layer thickness, which is consistent with the results of cross-sectional transmission electron microscope observation and X-ray diffraction. Figure 2 shows the PL spectra of the sputtered Ge layers at 4 K. We could not observe band-to-band emission derived from the HT Ge layer, but another peak at 0.61 eV. In addition, a positive correlation between the PL intensity and the LT Ge layer thickness was observed. We consider that the origin of another PL peak is self-interstitial Ge atoms [7] and it may be related to threading dislocations. In conclusion, we investigated the formation process of the high-quality heteroepitaxial Ge layer on a Si(111) substrate for the realization of Ge ultra-thin crystals on Al/Ge(111) by segregation and diffusion phenomena. Acknowledgements This work was partly supported by JSPS-KAKENHI Grant number 23K17745, The Canon Foundation, JST-PRESTO Grant Number JPMJPR21B6, and JST-CREST Grant Number JPMJCR21C2.

Abstract We report the superconducting properties of tensile-strained infinite-layer cuprate Sr 1− x Eu x CuO 2+ y thin films fabricated on KTaO 3 substrates via molecular beam epitaxy. The doping-dependent superconducting phase diagram shows an optimal doping level of $x\ \sim $ x ∼ 0.184 and a broader dome shifting to higher doping range due to reduced intralayer hopping and enhanced interlayer magnetic coupling. The characteristic of two-dimensional superconductivity is observed by Berezinskii-Kosterlitz-Thouless transition and the angle-resolved magnetoresistance measurements. Moreover, the temperature-dependent upper critical field and thermally-activated vortex motion under the in-plane and out-of-plane magnetic fields exhibit strong anisotropy, which further reveal the anisotropic nature of the superconductivity in infinite-layer cuprates.

With the largest tunable bandgap in the III-N class of semiconductors (6.02eV) and high thermal conductivity, aluminum nitride (AlN) has immense potential for use in high power electronics, heat sinks, and UV detectors. N-type doping of molecular beam epitaxy (MBE) and metal organic chemical vapor deposition (MOCVD) heteroepitaxially grown AlN is typically achieved with Si, a donor in AlN, with a typical ionization energy of approximately 300 meV1.AlN wafers and homoepitaxially grown films consisting of AlN on SiC from different vendors of N- and Al- polarities were measured using Raman spectroscopy and photoluminescence (PL) to better understand the underlying stress and defect bands present. An increasing E2 (high) shift in the Raman data was observed for each of the N-polar samples, though not in the Al-polar samples. This shift was found to be less than one wavenumber across a 2” wafer length from the center to the edge, but was consistent, suggesting existing tensile stress on the central region of the wafer, with decreasing tensile stress towards the edge. PL defect bands of interest include (i) one centered near 2.40eV (516 nm), corresponding to the presence of nitrogen vacancies (VN), (ii) one in the UV region centered around 3.6eV (344 nm) corresponding to oxygen substitution (ON)2 ,(iii) one near 3.0eV (413 nm) representing a secondary defect complex of VAl-ON or VAl-SiAl , potentially significant in helping to measure doping efficiency2, and finally, (iv) a band centered near 2.8eV (443 nm) points to a radiative recombination of highly charged aluminum vacancies (VAl)3-/2- and the valence band, giving rise to a visible orange luminescence3. X-ray diffraction (XRD) was used to look at the crystal quality of the samples tested, atomic force microscopy (AFM) was used to measure surface morphology and Young’s modulus, and optical profilometry was used to investigate the surface topography of the samples on a larger length scale than AFM.To study n-type doping efficiency in AlN, 400nm Si-doped films were grown. Due to the presence of large defect bands in the bulk material and the deep donor level of the Si, many dopants are not ionized and instead become deep acceptors. This leads to a significant reduction in the number of freely ionized carriers in the material, diminishing the potential electrical properties of the material. To solve this issue, the temperature of the sample is increased, which increases the number of ionized carriers, and moves the operational mode closer to the intrinsic region. Temperature dependent Hall effect studies of Al- and N-polar substrates were investigated in this work with regards to carrier concentration and doping efficiency, whose results can then be extrapolated to lower temperatures. Capacitance-voltage (C-V) testing was performed to further characterize the interface trap states, carrier lifetimes, and doping, while the transmission line model (TLM) was used to measure the impact of defects on metal-semiconductor contact resistivity. In this work, doping efficiency, defect structures, and electrical transport properties in AlN were characterized, with an eye on enhancing its electrical performance and practical applications.

Self-catalyzed molecular beam epitaxy on Si(111) substrates has enabled the growth and material exploration of GaAs-based heterostructure nanowires, demonstrating electron–photon conversion capabilities. GaAs, with its high carrier mobility and photoelectric efficiency, readily forms heterostructures with related compounds, making it suitable for optoelectronic applications such as solar cells, lasers, and transistors. The integration of GaAs nanowires on Si provides a promising platform for scalable device development, and the introduction of new material combinations further enhances its potential. During the nucleation stage of nanowire growth, small GaAs crystals were found to form at pinhole sites on the Si surface, establishing coherent lattice connections in three dimensions and generating high-quality epitaxial seeds with gradually varying strain. GaAs/AlGaAs nanowires grown atop these seeds retain excellent optical performance, exhibiting carrier lifetimes exceeding 1 ns and efficient photoluminescence even at around 400 K. The incorporation of dilute nitrogen or bismuth into GaAs nanowires enables precise control of bandgap and lattice parameters, allowing for lasing at telecommunication wavelengths, photon up-conversion, and the formation of quantum structures. GaInNAs and GaNAsBi nanowires extend emission into the near-infrared region while mitigating lattice mismatch with GaAs, forming quantum well structures that emit near 1.3 μm at room temperature. Moreover, wafer-scale growth of GaAs/AlGaAs core–shell nanowires on 2-inch Si wafers was achieved through a single-step process without surface pre-treatment. The Al-rich shell layers undergo natural oxidation, forming passivation films that enhance carrier lifetime and reduce visible light reflectance to below 2%. The resulting nanowires are uniform, optically luminescent, and exhibit adsorption characteristics, offering strong potential for large-area III–V heterostructure devices. Additionally, the absorption edge can be further shifted toward the infrared region by incorporating compound layers such as GaNAs within the nanowires. Furthermore, in coalesced GaAs nanowires embedded in AlOx, stress relaxation induced by oxidation led to the formation of cylindrical rolled-up membranes that retain the optical properties of the core and can be transferred. These rolled membranes exhibit white-light emission with characteristic polarization and are promising as compact, high-performance structures for nanoscale optoelectronic devices. These findings collectively demonstrate potential for advancing photoelectric conversion technologies on silicon substrates.

Copper (Cu) interconnects are an increasingly important bottleneck in integrated circuits due to energy consumption and latency caused by the notable increase in Cu resistivity as dimensions decrease, primarily due to electron scattering at surfaces. Here, we showcase the potential of two classes of metals for scaled interconnects 1) directional conductors that have low bulk resistivity and anisotropic structures that mitigate electron surface scattering, and 2) topological semimetals that utilize topologically protected surface states to suppress electron scattering. We will highlight thin films of PtCoO2 of various thicknesses, synthesized by molecular beam epitaxy (MBE) coupled with a post-deposition annealing process and the superior quality of PtCoO2 films is demonstrated by multiple characterization techniques. We will also discuss CoSi and GaPd, topological semimetals that exhibit reduced resistivity with decreasing wire dimensions, including a novel single-crystal synthesis technique. The thickness-dependent resistivity curves illustrate that PtCoO2 significantly outperforms effective Cu (Cu with TaN barriers) and Ru in resistivity below 20.0 nm with a more than 6x reduction compared to effective Cu below 6.0 nm, having a value of only 6.32 μΩ∙cm at 3.3 nm. CoSi exhibits a marked reduction in resistivity from its bulk values, but is still not competitive with Cu.

The incorporation of rare earth elements such as scandium (Sc) can transform conventional III-nitride semiconductors to be ferroelectric. This new class of ferroelectric nitride semiconductors can be seamlessly integrated with well-established gallium nitride and Si electronics with promising applications in memory and logic devices as well as high power, high frequency, and high temperature electronics. Moreover, ferroelectric nitrides exhibit significantly enhanced piezoelectric and nonlinear optical response compared to AlN, which makes it attractive for high frequency resonators and filters and nonlinear optical processes. To date, however, there still lacks a fundamental understanding of their ferroelectric properties and domain energetics. In this talk, I will present recent advances of nanoscale ferroelectric III-nitride semiconductors, including ScAlN, ScGaN, YAlN, and their alloys. I will discuss the molecular beam epitaxy, structural, optical, electrical, and ferroelectric properties. The atomic configurations and electronic properties of electric-field-induced domain walls in ferroelectric nitrides will be presented. Our studies have revealed a charged domain wall with a buckled two-dimensional hexagonal phase. Their emerging electronic and photonic device applications will also be discussed.

Germanium-tin (Ge1−x Sn x ), a group IV compound semiconductor, is a promising channel material for next-generation complementary metal-oxide-semiconductor technology due to its high carrier mobility. Furthermore, Ge1−x Sn x exhibits a direct bandgap transition under unstrained conditions when the Sn content exceeds 8%, enabling the further mobility enhancement by utilizing Γ-point electrons, which have a smaller effective mass compared to L-point electrons. However, the Sn content required for a direct transition in Ge1−x Sn x (001) becomes higher by applying biaxial compressive strain introduced during the crystal growth on Si or Ge substrates. Conversely, for Ge1−x Sn x (111), biaxial compressive strain would work to decrease the Sn content required for a direct bandgap transition [1]. Despite these potential advantages of Ge1−x Sn x (111), its characteristics remain largely unexplored. In this study, we report the formation of n-type Ge1−x Sn x (111) epitaxial layers through the ion implantation of phosphorus (P), and evaluate their electronic properties.The Ge1−x Sn x /Ge-buffer/Si(111) samples were prepared by the following procedure. After chemical cleaning of float-zone n-Si(111) substate (~1000 Ω∙cm), thermal cleaning was performed at 350 °C for 30 min under ultra-high vacuum condition in the molecular beam epitaxy (MBE) deposition chamber. Subsequently 70-nm-thick Ge-buffer and 100-nm-thick Ge0.92Sn0.08(111) layers were epitaxially grown at 300 and 150 °C using MBE, respectively. Then, P ions were implanted with an energy of 35 keV and a dose of 2.5×1014 cm−2. Finally, rapid thermal annealing (RTA) was employed for the activation at temperatures (T RTA) ranging from 300 to 600 °C for 1 min. For comparison, the Ge0.95Sn0.05/Ge(001) samples implanted with P ions with an energy of 18 keV and a dose of 4×1015 cm−2 were prepared.First, we investigated the recrystallization behavior of the Ge1−x Sn x layer by Raman scattering spectra, X-ray diffraction, and optical microscopy analyses for samples subjected to each process: deposition, ion implantation, and RTA. We found that the ion implantation caused the amorphization of the Ge1−x Sn x (111) layer surface and their recrystallization occurred after RTA at T RTA above 450 °C, whereas, for the Ge1−x Sn x (001) samples, the recrystallization occurred at T RTA above 400 °C. The temperature difference required for the recrystallization could be attributed to the lower recrystallization rate in the (111) orientation, as reported in cases of Si and Ge [2].Furthermore, we clarified that the Ge1−x Sn x layer subjected to RTA at T RTA = 450–500 °C retained an Sn content above 7% while achieving a degree of strain relaxation of 80–90%. However, RTA at T RTA above 550 °C caused the Sn content to decrease below 7%. Therefore, the optimal recrystallization temperature range without inducing the Sn precipitation is 450–500 °C.Finally, we examined the electrical conduction properties using the Hall effect measurement based on the multi-layer model [3]. The samples subjected to P ion implantation and RTA exhibited n-type conduction, with electron concentrations and Hall mobilities of 7.4×1018 cm−3 and 127 cm2/V·s for RTA at T RTA = 450 °C, and 6.1×1018 cm−3 and 137 cm²/V·s for RTA at T RTA = 500 °C, respectively. The phosphorus content in the Ge1−x Sn x layer was analyzed using secondary ion mass spectrometry (SIMS), and the effective activation rates were estimated to be 23% for both samples. This activation rate is equivalent to that of Ge1−x Sn x (100) samples, as estimated by hard X-ray photoelectron spectroscopy (HAXPES).In summary, we successfully formed n-Ge1−x Sn x (111) epitaxial layers through phosphorus (P) ion implantation. It was found that a higher recrystallization temperature is required for Ge1−x Sn x (111) compared to the (100) orientation, while achieving an equivalent activation rate. Consequently, the ion implantation method has been demonstrated to be a viable approach for developing n-Ge1−x Sn x (111) layers.The HAXPES measurement was performed at BL47XU in SPring-8 (Proposal No. 2014B0109). This work was partly supported by JST/CREST (No. JPMJCR21C2), JST/ASPIRE (No. JPMJAP2413), and JST/PRESTO (No. JPMJPR21B6).[1] W. Huang et al., J. Appl. Phys. 118, 165704 (2015).[2] L. Csepregi et al., Solid State Communications 21, 1019 (1977).[3] A. Nedoluha and K. M. Koch, Z. Phys 132, 608 (1952).

Charge balanced drift layers in power devices enable the use of highly doped drift layers to drastically reduce the on-resistance of power switches, significantly lowering the conduction losses. In conventional Si-based superjunction devices, alternate columns of n-type and p-type materials are used with carefully designed aspect ratios and net charge balance, imposing stringent process and doping control requirements. In this talk, we will present two innovative approaches implemented in Ga2O3 and GaN power diode structures which can surpass the unipolar figure of merit. First we introduce, the lateral dielectric superjunction Schottky barrier diode (SBD), where the electric field within the drift layer is modified from triangular to rectangular profile, enhancing the breakdown voltage and enabling the use of higher drift layer doping to reduce on-resistance. Next, we discuss p-NiO/n-GaN and p-NiO/p-GaN/n-GaN lateral superheterojunction structures for enhanced breakdown in lateral GaN diodes, which can be extended to transistors for enhanced breakdown and lower on-resistance. Dielectric superjunctions: A superjunction-like structure uses charge balance to push the VBR-Ron-sp trade-off beyond the material's unipolar figure of merit. The lack of p-type doping in β-Ga2O3 makes the realization of such structures very difficult. However, field flattening can be achieved in β-Ga2O3 drift layers using a high permittivity material with appropriate choice of dielectric constant, device aspect ratio and semiconductor/dielectric width. We employed analytical modeling [1] to optimize the device parameters, accounting for the appropriate dielectric and semiconductor dimensions including the aspect ratio and the dielectric constant of the highk material. Our findings reveal that device performance is intimately linked to structural dimensions and the dielectric constant of the insulator. Specifically, we observed that the dielectric superjunction SBD exhibits behavior akin to a conventional SBD, where the effective doping density in the drift layer decreases by a factor dependent on semiconductor and dielectric width, aspect ratio and the dielectric constant of the insulator. We discuss optimal design guidelines for achieving a 10 kV β-Ga2O3 SBD with a PFOM of 50 GW/cm2 . Additionally, we conducted a comparative analysis of the switching energies between the superjunction Schottky barrier diode and a conventional Schottky barrier diode. We provide design guidelines to minimize switching energies for a desired PFOM in β-Ga2O3 SBDs.The experimental demonstration is reported in the lateral geometry [2]. 500 nm of Si-doped Ga2O3 epitaxial layer with a sheet charge of 1.6×1013 cm-2 is grown using metal organic vapor phase epitaxy (MOVPE). Trenches with three different fin widths (WFin = 2, 5, 10 µm) were made and high-k dielectric BaTiO3 (BTO) with dielectric constant of 220 is deposited on the sample. A low specific on resistance of 1.65 mΩ-cm2 is observed for LAC = 5µm due to the high charge density epitaxial lateral Fins. For the SBD with LAC = 5µm and WFin = 5µm, a high average electric field of ~3 MV/cm (VBR/ LAC) is estimated across the entire length of the device. A very high Baliga's figure of merit (BFOM) of 1.35 GW/cm2 is observed for the RESURF SBD with LAC=5µm and WFin=2µm (VBR=1.49 kV and Ron-sp=1.65 mΩ-cm2), surpassing SiC unipolar FOM when considering just the conducting area. NiO/GaN superheterojunctions: This work reports the fabrication and characterization of the lateral kilo-volt class NiOx/GaN super-heterojunction (SHJ) diodes with GaN grown using ammonia molecular beam epitaxy (NH3-MBE). Si-doped GaN layer was grown on a semi-insulating Fe-doped GaN-on-sapphire template after an unintentionally doped (UID) buffer layer with charge density confirmed by high-voltage capacitance-voltage (C-V) and room temperature Hall effect measurements. After cathode contacts on n-GaN, p- NiOx was deposited via reactive magnetron sputtering to form a charge-balanced extension region. The acceptor concentration (Na) in sputtered p- NiOx was extracted via heterojunction diode capacitance-voltage (C-V) method at 10 kHz. The NiOx/GaN SHJ diode with 50- μm anode-cathode distance (LAC) SHJ diodes exhibited the highest breakdown voltage at ~2.8 kV with SU-8 passivation, showing a 5X improvement of breakdown voltage compared to its reference counterparts that were not charge-balanced. The maximum average breakdown field of SHJ diode was extracted to be >1 MV/cm across 16-μm LAC.We acknowledge funding from AFOSR MURI program, Coherent/II-VI foundation, and Department of Energy (DOE) ARPA-E OPEN 2021 program (DE-AR0001591).

Abstract Layered platinum diselenide (PtSe 2 ) grown by molecular beam epitaxy (MBE) provides a reliable and reproducible alternative to mechanical exfoliation, making it suitable for scalable device integration. In this work, we thoroughly investigate the in-plane thermal conductivity of 13-layer suspended PtSe 2 membranes. For this study, we first achieved the transfer of large-scale epitaxially grown PtSe 2 and demonstrate a highly efficient process that enables the fabrication of multiple suspended membranes in a single transfer while maintaining the structural quality of the material. Optothermal Raman Technique (ORT) is then used to investigate the in-plane thermal conductivity of the suspended PtSe 2 membranes. This approach leverages millimeter-scale transfer to conduct systematic ORT measurements, enabling statistical refined thermal conductivity of 11.92 ± 1.78 W·m -1 ·K -1 , with negligible dependence on vacuum/air environments. Finally, our results are supported by numerical simulations using a COMSOL model. This work provides significant insights into the thermal properties of PtSe 2 , paving the way for the design of high-performance electronic devices with enhanced thermal management capabilities. 

The (013)HgTe layer growth of different thicknesses by molecular beam epitaxy on complex substrates (013)CdTe/ZnTe/GaAs, with the precision control of composition and thickness by the ellipsometric method in situ, is presented in this article. The growth temperature was ∼180 °C. The HgTe layer thickness ranged from 7 to 1300 nm. Measurements of the azimuthal dependence of reflected second harmonic generation signals and the null method revealed stresses in the HgTe layers. The maximum stress of ∼123 MPa was observed in HgTe layers with a thickness from 80 up to 120 nm, which was determined as a critical thickness. At high thicknesses, the stress relaxation, which has an inversely proportional dependence on thickness, was observed. The residual stress was ∼10 MPa at the HgTe thickness of 1300 nm.

Abstract Hexagonal boron nitride (hBN) has recently been shown to host native defects exhibiting optically detected magnetic resonance (ODMR) with applications in nanoscale magnetic sensing and imaging. To advance these applications, deposition methods to create wafer-scale hBN films with controlled thicknesses are desirable, but a systematic study of the ODMR properties of the resultant films is lacking. Here we perform ODMR measurements of thin films (3-2000nm thick) grown via three different methods: metal-organic chemical vapour deposition (MOCVD), chemical vapour deposition (CVD), and molecular beam epitaxy (MBE). We find that they all exhibit an ODMR response, including the thinnest 3nm film, albeit with different characteristics. The best volume-normalised magnetic sensitivity obtained is 30 µTHz -1/2 µm 3/2 . We study the effect of growth temperature on a series of MOCVD samples grown under otherwise fixed conditions and find 800-900°C to be an optimum range for magnetic sensitivity, with a significant improvement (up to two orders of magnitude) from post-growth annealing. This work provides a useful baseline for the magnetic sensitivity of hBN thin films deposited via standard methods and informs the feasibility of future sensing applications.

Multisubband plasmon (MSP) modes in heavily doped InAs/GaSb broken-gap quantum wells grown via molecular beam epitaxy (MBE) are investigated. An eight-band k ⃗ · p ⃗ semiclassical model accurately predicts ellipsometric spectra, reflecting strong subband hybridization and nonparabolicity. In contrast, single-band plasmon models show qualitative discrepancies with experiment, even with adjusted effective masses. These findings highlight the potential of broken-gap wells for quantum technologies leveraging interband coupling and wavefunction hybridization.