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Oxygen is a ubiquitous contaminant in thin films grown in high vacuum systems, and it was hypothesized to play an important role in the properties of the p -type conductivity of transparent copper(I) iodide, CuI. We study the ambient properties of CuI deposited at various partial pressures of oxygen gas. Through a variety of experimental techniques, we find that achieving a critical oxygen partial pressure of below p(O2) = 3 × 10 − 5 mbar is essential for depositing stoichiometric and conductive CuI thin films. Notably, we relate the commonly reported copper excess to the presence of oxygen within the CuI films. Notably, we relate the commonly reported excess of copper in CuI thin films to to the presence of oxygen. Finally, we infer from transport and optical measurements that the hole transporting properties of sputtered CuI films are dominated by an abundance of VCu defects with an acceptor transition energy of 84 ± 3 meV rather than OI defects with an acceptor transition energy of 175 ± 14 meV. [ABSTRACT FROM AUTHOR]

The growing interest in hybrid devices that combine two-dimensional materials with a superconductor presents new challenges in material deposition. In this study, we demonstrate that achieving excellent superconducting properties by RF (radio frequency) sputtering does not require access to a high-end system but rather depends on the precise control of sputtering parameters and the selection of an appropriate lithographic process. We highlight the challenges and present practical solutions to deposit high-quality niobium thin films for the lithographic production of superconducting hybrid nanostructures. The influence of various deposition parameters, such as power, argon pressure, and film thickness, on the resultant superconducting characteristics can already be deduced at liquid nitrogen temperatures. Furthermore, niobium films tend to degrade when a PMMA [poly(methylmethacrylate)] resist is employed in the fabrication of superconducting nanostructures. We propose alternative and simple strategies to address this issue, which ultimately result in the restoration of the thin-film quality. [ABSTRACT FROM AUTHOR]

Ferrimagnetic materials have garnered significant attention due to their broad range of tunabilities and functionalities in spintronics applications. Among these materials, rare earth-transition metal GdFeCo alloy films have been the subject of intensive investigation due to their spin-dependent transport properties and strong spin–orbit coupling. In this report, we present self-induced spin-to-charge conversion in single-layer GdFeCo films of different thicknesses via an inverse spin Hall effect. A detailed investigation of spin dynamics was carried out using broadband ferromagnetic resonance measurements. The anisotropy constant and the effective g-factor are found to decrease with thickness, and they become nearly constant for thicknesses beyond 25 nm. A remarkably low damping constant of 0.0029 ± 0.0003 is obtained in the 43 nm-thick film, which is the lowest among all previous reports on GdFeCo thin films. Furthermore, we have demonstrated a self-induced inverse spin Hall effect, which has not been reported so far in a single-layer of GdFeCo thin films. Our analysis shows that the inverse spin Hall effect becomes increasingly dominant over the spin rectification effect with increasing film thickness. The in-plane angular-dependent voltage measurement of the 43 nm-thick film reveals a spin pumping voltage of 1.64 μV. The observation of spin-to-charge current conversion could be due to the high spin–orbit coupling element Gd in the film as well as the interface between GeFeCo/Ti and substrate/GdFeCo of the films. Our findings underscore the potential of GdFeCo as a prime ferrimagnetic material for emerging spintronic technologies. [ABSTRACT FROM AUTHOR]

Hexagonal boron nitride (h-BN) stands out among 2D materials for its insulating properties, making it promising for the integration of 2D and 3D materials. However, achieving wafer-scale growth on silicon substrates remains a significant challenge. In this study, growth strategies for depositing h-BN on Si substrates are explored utilizing the wafer scalable metalorganic chemical vapor deposition. Our investigations reveal that employing a pulsed flow mode scheme is preferable over the conventional continuous flow mode scheme in growing h-BN thin films on 150 mm Si substrates. The as-grown h-BN film on Si exhibits uniform coverage with h-BN[0001]//Si[111]. With the successful wafer-scale growth of h-BN on Si, its role in aiding the van der Waals epitaxy of III-nitrides on Si substrates and subsequent epitaxial lift-off (ELO) of III-nitrides is further exemplified. An optimized h-BN thickness for the ELO process is also determined. [ABSTRACT FROM AUTHOR]

Various biomimetic microstructures, such as porous, cracks, wrinkles, micro-pyramids, and micro-domes, are applied to improve the sensing performance of mechanical sensors. Among them, the crack-based strain sensors are widely investigated due to high sensitivity and fast response time. To clearly describe the relationship between crack morphology and sensor sensitivity, a mathematical model is developed for investigating the performance of a poly(3,4-ethylenedioxythiophene)-silicon oxide/polydimethylsiloxane (SiOx/PDMS) based crack strain sensor. First, the displacement field of a crack tip is calculated based on the theory of fracture mechanics, and the mathematical relationship between the crack depth, crack gap, and strain is obtained. The predicted crack depth of the SiOx thin film's thicknesses in 7.91 μm (SiOx/PDMS-7.91) is 2.82 μm, with the error of 3.75% compared to the experimental result. Correspondingly, the deviation of SiOx/PDMS-7.91 is 5.74% between the predicted crack gap and the experimental data. Second, above the aforementioned crack tip characteristics, the mathematical model based on crack edges contacts probability (CECP) is used to construct the relationship between the crack tip characteristics, applied stress, and device sensitivity. The maximum predicted sensitivity can reach 3562.68 compared with the experimental data of 3800.44, and the deviation is about 6.26%. Moreover, the CECP model has good universality with the other reported crack-based strain sensors. It can be concluded that crack morphology affects the distribution and quantity of conductive paths. When the strain sensor is subjected to external forces, brittle thin films generate a certain number of bumped-like elements for microcracks. The wider and deeper crack will increase the relative resistance change and the decrease of conductive paths, resulting in a rapid increase in the sensitivity of the strain sensor. [ABSTRACT FROM AUTHOR]

Magneto-optical gyrotropic Faraday and Kerr effects are studied in the BiY2Fe5O12 films with thicknesses ranging from 16 to 55 nm, in the wavelength range of 295 nm < λ < 830 nm (4.2–1.5 eV), and under magnetic fields of up to 1.2 T. It is shown that films produced by ac magnetron sputtering on the single-crystalline diamagnetic yttrium aluminum garnet substrates Y3Al5O12 (001) exhibit high structural and magneto-optical quality. The Verdet constant for diamagnetic Y3Al5O12 is determined, and the magnitude of the Kerr effect is estimated for the polished substrate. It is shown experimentally that for a substrate with diffusely reflective backside, the Kerr effect is about zero, except in the high-energy region. For all BiY2Fe5O12 films investigated, in the saturating magnetic fields of approximately 0.16–0.2 T, the value of specific Faraday rotation reaches 20 deg/μm (200 000 deg/cm), while the value of the Kerr effect reaches approximately 20 min (5.8 mrad). The critical thickness of the film–substrate interface was estimated, highlighting variations in the Kerr effect spectra associated with a decrease in the Bi content in thin films with the thicknesses of below 27 nm. [ABSTRACT FROM AUTHOR]

Spin-Hall nano-oscillators (SHNOs) are nanoscale spintronic devices that generate high-frequency (GHz) microwave signals useful for various applications, such as neuromorphic computing and creating Ising systems. Recent research demonstrated that hybrid SHNOs consisting of a ferromagnetic metal (permalloy) and lithium ferrite-based (LAFO) insulating ferrimagnetic thin films have advantages in having lower auto-oscillation threshold currents (I th) and generating larger microwave output power, making this hybrid structure an attractive candidate for spintronic applications. It is essential to understand how the tunable material properties of LAFO, e.g., its thickness, perpendicular magnetic anisotropy (K u , LAFO ), and saturation magnetization (M s , LAFO ), affect magnetic dynamics in hybrid SHNOs. We investigate the change in I th and the output power of the device as the LAFO parameters vary. We find the I th does not depend strongly on these parameters, but the output power has a highly nonlinear dependence on M s , LAFO and K u , LAFO . We further investigate the nature of the excited spin-wave modes as a function of K u , LAFO and determine a critical value of K u , LAFO above which propagating spin-waves are excited. Our simulation results provide a roadmap for designing hybrid SHNOs to achieve targeted spin excitation characteristics. [ABSTRACT FROM AUTHOR]

This work evaluates the passivation effectiveness of ultrathin nitride layers (SiNx, AlN, and TiN) deposited via atomic layer deposition on CdTe/MgCdTe double heterostructures for solar cell applications. Time-resolved photoluminescence and photoluminescence measurements revealed enhanced carrier lifetimes and reduced surface recombination, indicating improved passivation effectiveness. These results underscore the potential of SiNx as a promising passivation material to improve the efficiency of CdTe solar cells. [ABSTRACT FROM AUTHOR]

We theoretically study the evaporation-driven phase separation of a binary fluid mixture in a thin film deposited on a moving substrate, as occurs in meniscus-guided deposition for solution-processed materials. Our focus is on the limit of rapid substrate motion where phase separation takes place far away from the coating device. In this limit, demixing takes place under conditions mimicking those in a stationary film because substrate and film move at the same speed. We account for the hydrodynamic transport of the mixture within the lubrication approximation. In the early stages of demixing, diffusive and evaporative mass transport predominates, consistent with earlier studies on evaporation-driven spinodal decomposition. In the late-stage coarsening of the demixing process, the interplay of solvent evaporation, diffusive, and hydrodynamic mass transport results in several distinct coarsening mechanisms. The effective coarsening rate is dictated by the dominant mass transport mechanism and therefore depends on the material properties, evaporation rate, and time: slow solvent evaporation results in initially diffusive coarsening that for sufficiently strong hydrodynamic transport transitions to hydrodynamic coarsening, whereas rapid solvent evaporation can preempt and suppress hydrodynamic and diffusive coarsening. We identify a novel hydrodynamic coarsening regime for off-critical mixtures, arising from the interaction of the interfaces between solute-rich and solute-poor regions in the film with the solution–gas interface. This interaction induces a directional motion of solute-rich droplets along gradients in the film thickness, from regions where the film is relatively thick to where it is thinner. The solute-rich domains subsequently accumulate and coalesce in the thinner regions. [ABSTRACT FROM AUTHOR]

YxAl1 − xN in its wurtzite phase has been identified as a prospective wide bandgap semiconductor and a promising competitor of ScxAl1 − xN in application devices. Notwithstanding theoretical predictions of the high stability of YxAl1 − xN in the wurtzite structure even at high alloy concentrations, experimental studies have revealed significant challenges in achieving the requisite high concentration films. This study demonstrates that strain is an effective parameter on the growth of wurtzite YxAl1 − xN, which can be tuned by engineering growth methods, such as the introduction of different buffer layers. Conversely, difficulties have been encountered in achieving Y concentrations above x = 0.4, despite the incorporation of Y atoms into the layers, with the formation of amorphous structures occurring prior to the predicted structural phase transition to the rock salt crystal. A comprehensive grasp of the structural characteristics of YxAl1 − xN thin films offers invaluable insight that will prove to be beneficial for future research on this material system. [ABSTRACT FROM AUTHOR]

There is an important difference between piezoelectric polymer films and solid crystals for the application of piezoelectric generators. In the case of polymers, the optimal piezoelectric response imposes a large bending regime. Starting from the linear Curie's constitutive equations, we develop an analytical model under the assumption of the large bending regime resulting from bulge testing configuration. This model shows a specific non-linear piezoelectric response, which follows a power of 2 / 3 of the mechanical excitation. The piezoelectric voltage and the corresponding power are then studied experimentally as a function of the angular frequency ω of the mechanical excitation, the load resistance R , and the thickness of the film ℓ. The experimental results carried out on piezoelectric polyvinylidene fluoride (PVDF) films validate the model. [ABSTRACT FROM AUTHOR]

Strain engineering is an important way to control the physical properties of manganite thin films. Here, the effect of strain mode on the transverse thermoelectric (TTE) effect of inclined La1xCaxMnO3 (LCMO) thin films is investigated. The compressive strain enhances the electrical conductivity of the LCMO thin film, resulting in larger laser-induced voltage and faster response speed, which is suitable for high-energy pulse laser detection. Compared to that, the LCMO thin film on the STO substrate is ideal for heat-flux detection due to higher heat-flux sensitivity originating from lower conductivity. Still, it also has to withstand the loss of response speed. Moreover, it is first observed that the TTE voltage polarity of the LCMO thin film changes under different strain states. The measured results of LCMO thin films deposited LaAlO3 (LAO) substrate buffered with the SrTiO3 (STO) thin film and STO substrate buffered with the LAO thin film strongly support that the above results are indeed caused by the lattice strain. This work may be suitable for other material systems to modulate thermoelectric transport anisotropy and the TTE effect by strain. [ABSTRACT FROM AUTHOR]

Doped GeSbTe (GST)-based phase change materials are of growing interest due to their ability to enable high-temperature data retention for embedded memory applications. This functionality is achieved through Ge enrichment and addition of dopants such as N and C in stoichiometries such as GST-225, which improve the crystallization temperature and thermal phase stability. In this study, we examine the effect of these dopants on thermal conductivity using Raman thermometry. We report the temperature-dependent thermal conductivity of the amorphous and crystalline phases of Ge-rich GeSbTe (GGST) and Ge-rich GeSbTe N-doped (GGSTN) thin films. The results reveal a surprising temperature dependence of the thermal conductivity of the crystalline phase of GGST and GGSTN, a phenomenon not typically observed for GST-based materials. Additionally, enrichment of Ge and subsequent N-doping result in reduced thermal conductivity, which can benefit the power consumption of phase change memories. From a characterization perspective, Raman thermometry has been developed as a technique for simultaneous structural and thermal characterization of GST-based materials. [ABSTRACT FROM AUTHOR]

The magnetic state of an antiferromagnetic (AFM) insulator can be read and manipulated in spintronics devices using bilayers of an AFM and a conducting layer, making it useful for spintronics devices. To date, research has focused on single crystals of AFMs, which enables the study of properties related to different crystallographic surfaces. However, combining single-crystal AFMs in spintronics devices may be problematic due to substrate selectivity and deposition conditions. In this work, we study the properties of polycrystalline Fe2O3 coupled with Pt as the conducting layer, asking how the magnetoresistive behavior differs in polycrystalline AFMs. We report on the angle dependent magnetoresistance and transverse magnetoresistance properties as a function of temperature and magnetic fields, comparing Fe2O3/Pt and Fe2O3/Cu/Pt thin films, in addition to magnetometry and structural characterization. The magnetoresistance signals do not depend on the thickness or volume behavior of the Fe2O3 layer, but rather the Fe2O3/Pt interface. Angle dependent magnetoresistance measurements show ferromagnetic-like behavior but with a non-standard effect of field, while transverse measurements show a sign change with temperature. This differs from effects reported for single-crystal Fe2O3 based bilayers. Interestingly, using transverse field measurements, we find that at low temperatures, the Fe2O3/Pt interface spins develop a glass-like relaxation of the magnetic signal, which undergoes freezing as the sample is further cooled. [ABSTRACT FROM AUTHOR]

We present a novel simulation approach combined with pulsed laser experiments, spectroscopic ellipsometry, and Raman spectroscopy to comprehensively analyze phase transformation dynamics in thin films. The simulations apply to any thin film stack and incorporate critical factors, such as thin film interference, heat transfer, and temperature-dependent optical properties during heating and melting. As a case study, we investigate the picosecond laser-induced amorphization of antimony sulfide (Sb2S3) thin films, a promising alternative to traditional phase-change materials in photonic applications to validate the simulation model. The computational efficiency of our simulations enables not only the investigation of the laser-induced phase transformation but also the optimization of key process parameters and parameter fitting. The simulations identified optimal film thickness and laser fluence parameters that maximize energy efficiency, melting effectiveness, and quenching rate while ensuring high reflectivity contrast between the amorphous and crystalline states. By constructing a wide-ranging, high-resolution parameter map of the laser fluence and film thickness dependence of the melting process, we demonstrate how this model guides the understanding of phase transformation dynamics. Raman spectroscopy confirms the polycrystalline to amorphous transition of Sb2S3 and provides a semiquantitative estimate of the amorphous fraction as a function of laser fluence, which is qualitatively consistent with the simulation predictions of the model. The open-source simulation framework, experimentally validated, provides valuable insights into laser-induced amorphization dynamics in Sb2S3 and related phase-change material thin films, enabling rapid optimization of photonic devices. [ABSTRACT FROM AUTHOR]

Polyethyleneimine (PEI) is a widely used cationic polyelectrolyte. In organic electronics, it is a universal surface modifier for shifting the electrode work function (Φ) and improving charge injection into electronic devices. This effect may depend on the conformation and dipolar order of the PEI ultrathin film, but their detailed experimental evaluation has not yet been reported. Thus, we used sum-frequency generation (SFG) spectroscopy to probe the net orientation of polar groups of PEI films on glass and gold. The films were fabricated by spin-coating from alcoholic solutions or by dip-coating from aqueous solutions of various pH values, with both branched (b-PEI) and linear (l-PEI) structures. The obtained SFG spectra and atomic force microscopy (AFM) images indicated that the conformational ordering of the PEI layers increases over the period of 14 days after fabrication, being slightly more pronounced for l-PEI vs b-PEI, and for dip-coating vs spin coating fabrication. Furthermore, both the pH of the dip-coating solutions and the substrate nature influence the final morphology and order of the adsorbed films. On glass, they are optimized at an intermediate pH 5, while on gold, the greatest homogeneity is observed at pH 2 and the largest dipolar order is observed at pH 10. The pH dependence of changes in the work function of gold by PEI (|ΔΦ|) suggests that the electronic contribution is dominant. Nevertheless, the evolution of the PEI dipolar ordering was accompanied by small variations of |ΔΦ|, suggesting that it does have a significant contribution, especially at conditions for which the electronic contribution is reduced. [ABSTRACT FROM AUTHOR]

High critical current (Ic) in high magnetic fields (B) with minimal variations with respect to the orientation of the B field is demanded by many applications such as high-field magnets for fusion systems. Motivated by this, this work studies 6 vol. % BaZrO3/YBa2Cu3O7 (BZO/YBCO) multilayer nanocomposite films by stacking two 10 nm thick Ca0.3Y0.7Ba2Cu3O7 (CaY-123) spacers with three BZO/YBCO layers of thickness varied from 50 to 330 nm to make the total film thickness of 150–1000 nm. The Ca diffusion from the spacers into BZO/YBCO was shown to dramatically enhance pinning efficiency of c-axis aligned BZO nanorods, which yields high and almost thickness independent critical current density (Jc) in the BZO/YBCO multilayer nanocomposite films. Remarkably, enhanced Jc was observed in these multilayer samples at a wide temperature range of 20–80 K and magnetic fields up to 9.0 T. In particular, the thicker BZO/YBCO multilayer films outperform their thinner counterparts in both higher value and less anisotropy of Jc at lower temperatures and higher fields. At 20 K and 9.0 T, Ic is up to 654 A/cm-width at B//c in the 6% multilayer (1000 nm) sample, which is close to 753 A/cm-width at B//ab due to the intrinsic pinning. This result illustrates the critical role of the Ca cation diffusion into the YBCO lattice in achieving high and isotropic pinning in thick BZO/YBCO multilayer films. [ABSTRACT FROM AUTHOR]

We investigate the growth of Au/FexNy/MgO trilayers on GaAs(001) substrates by plasma-assisted molecular beam epitaxy. The optimization of the growth conditions made it possible to obtain the compound of stoichiometric Fe4N. Microstructural studies show that Fe4N forms 3D islands at the initial stages of growth. As the Fe4N thickness increases, a columnar growth sets in leading to a strong texturing and to the formation of grains having the same crystallographic orientation. The growth is epitaxial with the relationship GaAs (001) [110]//MgO (001) [110]//Fe4N (001) [110]//Au (012) [0–32]. A chemical analysis at the nanoscale reveals that the interfaces are rather sharp with a limited interdiffusion. Magnetic characterizations show that a trilayer containing a 1-nm-thick Fe4N layer is already ferromagnetic. The easy magnetization axis is in-plane independent of the Fe4N layer thickness (from 1 to 6 nm). This study shows the potential to use Fe4N as a spin injector for spin-optoelectronic applications. [ABSTRACT FROM AUTHOR]

Electrically induced resistive switching (RS) effects have been proposed as the basis for future non-volatile memories. In this work, 9 nm-thick BiFeO3 (BFO) epitaxial thin films were deposited on (001)-oriented SrTiO3 substrates by pulsed laser deposition and their resistive switching (RS) behaviors were investigated. A large resistive switching with ON/OFF ratio of ∼106 is observed, surpassing the performance of most resistive random access memories ever reported. The conducting filament is proposed to dominate the RS behavior in the positive voltage region, while the modulation of ferroelectric polarization is suggested to play a significant role in the negative voltage region. Our study significantly deepens the understanding of the physical origin of RS and could provide a reference for designing high-performance memories and memristors based on ultrathin ferroelectric films. [ABSTRACT FROM AUTHOR]

This study presents the detailed characterization of a magnetron-based Ar–N2 plasma discharge used to sputter a liquid Ga target for the deposition of gallium nitride (GaN) thin films. By utilizing in situ diagnostic techniques including optical emission spectroscopy and microwave interferometry, we determine different temperatures (rotational and vibrational of N2 molecules, and electronic excitation of Ar atoms) and electron density, respectively. Beyond providing insights into fundamental plasma physics, our research establishes a significant correlation between gas-phase dynamics, particularly those of gallium atoms (flux and average energy at the substrate) and deposited GaN thin film properties (growth rate and crystalline fraction). These findings underscore the role of plasma conditions in enhancing thin film quality, highlighting the importance of plasma characterization in understanding and optimizing GaN thin film growth processes. [ABSTRACT FROM AUTHOR]

Chemical and physical processes on the surfaces of amorphous solids have been the focus of many studies over the past decades. These studies have established that dynamics in a thin layer near a glass surface are often dramatically faster than those in the glass bulk. Nevertheless, recent advances also emphasize the need for new experimental techniques capable of characterizing the structure and dynamics of the near-surface regions in glassy materials at the molecular length scale. Using a quasi-adiabatic fast scanning calorimetry (FSC) technique, we have investigated softening and vaporization of pure amorphous methylbenzene films of moderately heightened kinetic stability with thicknesses ranging from 1 to 20 nm. The analysis of the FSC thermograms reveals the existence of a high fictive temperature (liquid-like) layer on the surface of the solid glass with a thickness of 3.5 ± 0.5 nm or seven molecular diameters. Furthermore, the width of the boundary between liquid-like and solid layers in the films is less than 1 nm. These preliminary findings compliment and substantiate past determinations of the mobile surface layer thicknesses obtained by introduction of nanoparticles or spectroscopic molecular probes to near-surface regions of amorphous samples. The developed FSC methodology will advance the theoretical and computational research by providing calorimetric data on the enhanced interfacial dynamics phenomenon in a variety of low-molecular-weight amorphous materials. [ABSTRACT FROM AUTHOR]

Generalized ellipsometry measurements are used to extract the complex dielectric function (ε = ε 1 + i ε 2) spectra of GdScO3 single crystals over the 0.7–8.5 eV photon energy range. GdScO3 is a wide bandgap semiconductor with a high dielectric constant, and potential applications include replacing SiO2 in silicon-based transistors and as an epitaxial substrate for thin film growth. This work presents the anisotropic optical properties for electric fields oscillating parallel to the a-, b-, and c-crystallographic axes. A direct bandgap is identified at 6.44 eV along the direction parallel to the a-axis, with additional critical points observed at 6.74 and 7.42 eV in the same direction. Additional above gap critical point transitions are found at 6.72, 7.31, and 7.96 along the direction parallel to the b-axis and 6.83 and 8.00 eV along the direction parallel to the c-axis. [ABSTRACT FROM AUTHOR]

Generalized ellipsometry measurements are used to extract the complex dielectric function (ε = ε 1 + i ε 2) spectra of GdScO3 single crystals over the 0.7–8.5 eV photon energy range. GdScO3 is a wide bandgap semiconductor with a high dielectric constant, and potential applications include replacing SiO2 in silicon-based transistors and as an epitaxial substrate for thin film growth. This work presents the anisotropic optical properties for electric fields oscillating parallel to the a-, b-, and c-crystallographic axes. A direct bandgap is identified at 6.44 eV along the direction parallel to the a-axis, with additional critical points observed at 6.74 and 7.42 eV in the same direction. Additional above gap critical point transitions are found at 6.72, 7.31, and 7.96 along the direction parallel to the b-axis and 6.83 and 8.00 eV along the direction parallel to the c-axis. [ABSTRACT FROM AUTHOR]

The use of thin films made of alloys, i.e., containing multiple metal species, can enhance their properties. However, as with single-element films, residual stress in the films can limit their performance. A model is proposed for relating the stress in alloy thin films to the processing conditions (growth rate, temperature, and sputter-gas pressure), material properties (composition, atomic and defect mobilities, and elastic moduli), and microstructure (grain size and grain growth kinetics). The model is based on stress-generating processes that occur during film growth at grain boundaries and due to energetic particle impacts. While the equations are similar to those proposed for single-element films, the alloy kinetic parameters now contain the effects of the different atomic species. The model is used to explain the growth rate and composition dependence of in situ stress evolution during the deposition for various concentrations in the tungsten–vanadium system. [ABSTRACT FROM AUTHOR]

Graphite/SiC (GSC) thin films were synthesized on silicon substrates via a spray method, depositing a Si-graphite solution on preheated silicon samples at 350 °C, followed by annealing at 800 °C for 4 h. A systematic approach was employed to ensure the effective incorporation of graphite into the SiC material during solution preparation. Various analytical techniques, including XPS, UPS, Reflection Energy Electron Loss Spectroscopy (REELS), PL, AFM, and Hall effect measurements, were employed for comparative analysis of the chemical composition, morphological, electrical, and optoelectronic properties of as-deposited and annealed GSC films. XPS analysis revealed the presence of Si—C and graphitic bonds in the as-deposited GSC, with a significant compositional shift to oxygen-rich graphite oxide/oxycarbides after annealing. REELS demonstrated increased bandgap and bulk plasmon energy due to surface oxidation, while UPS highlighted a high electronic density in the as-deposited film, diminishing after annealing. AFM revealed a tendency of as-deposited GSC grains to form smaller, sharper structures after annealing, resulting in smoother and more homogeneous surface morphology. Phase AFM confirmed graphite incorporation at grain boundaries and within the bulk, forming a composite structure. PL spectra of the as-deposited film exhibited a broad visible emission with distinct sub-peaks linked to SiC bandgap transitions and carbon-rich defects. Chromaticity diagrams indicated suitability for white LED applications. Hall effect measurements showed excellent electrical properties of the as-deposited GSC film, with high carrier density and mobility, which reduced significantly after annealing, transitioning the material to a more insulating state. These findings collectively provide a comprehensive understanding of GSC thin films' properties and their potential applications. [ABSTRACT FROM AUTHOR]

Despite the extensive research on HfO2-based thin films, the ferroelectric orthorhombic phase formation remains unclear. This work proposes a physical picture throughout the entire annealing process to describe the phase transition. Subsequently, the phase evolution at various doping and annealing temperatures is illustrated based on a kinetic model formalized from the classical nucleation theory. It is found that the formation of the ferroelectric orthorhombic phase depends not only on a modest doping concentration but also on the thermal activation of the t-to-o phase transition provided by a sufficient annealing temperature. In addition, phase transition rates correlated to the monoclinic phase formation are effectively suppressed by doping. The exploration of combined effects of annealing parameters indicates a more decisive role of the annealing temperature rather than the keeping time for induced ferroelectricity, and the doping impact becomes significant when a critical annealing temperature is reached. This work provides an understanding for exploring the kinetic effect on the phase transition in HfO2-based thin films, which helps improve ferroelectricity in doped HfO2 ferroelectric films. [ABSTRACT FROM AUTHOR]

Epitaxial films of BiAl x Fe 1 − x O 3 (xBAFO) were grown on SrTiO 3 (STO) and SrRuO 3 buffered STO substrates using pulsed laser deposition. To understand the effects of Al substitution at the Fe-site of BFO, we systematically investigated its impact on the material's crystal structure, surface morphology, ferroelectric properties, and magnetic properties. Our x-ray diffraction analysis revealed that phase-pure xBAFO films can be stabilized for Al concentrations between 0% and 35%, without the formation of secondary phases, due to the isotypic crystal structures of BiAlO 3 and BiFeO 3. This allowed the rhombohedral structure of BAFO to be preserved. We then characterized the ferroelectric properties of xBAFO (0 ≤ x ≤ 0.25) by analyzing polarization-voltage hysteresis loops, which exhibited a transition from a nearly square shape to a more slanted shape with increasing Al substitution. Additionally, piezoresponse force microscopy revealed that the domain growth mode, shape, size, dimension, and nucleation play a crucial role in the switching behavior of ferroelectric materials. Furthermore, we observed a modest enhancement in magnetization due to the modified spin ordering of Fe atoms with Al substitution. Notably, the optimal ferroelectric and magnetic properties were achieved at an Al concentration of 15%. These findings suggest that BAFO is a promising magnetoelectric material with desired functionalities for realizing BFO-based next-generation non-volatile memory devices. [ABSTRACT FROM AUTHOR]

Hafnium diboride (HfB2) is a promising candidate as a seed layer for GaN growth on Si substrates due to its excellent lattice and thermal coefficients matching with both materials. This work investigates the epitaxial growth of AlB2-type non-stoichiometric HfB2 (HfB2+δ with −0.1 < δ < 0.6) thin films on Si(111) using magnetron co-sputtering. We demonstrated that the process temperature significantly affected the surface roughness (RRMS ∼ 0.5–4 nm), film composition, and the nucleation of secondary impurity phases. Films deposited between 700 and 900 °C exhibit epitaxial growth on the Si substrate with a well-defined relationship of (0001) HfB 2 ‖ (111) Si and [ 11 2 ¯ 0 ] HfB 2 ‖ [ 1 1 ¯ 0 ] Si . Detailed x-ray diffraction and scanning transmission electron microscopy analyses reveal that impurity phases detected at high temperatures are primarily carbon-rich phases, identified as HfCx or HfCxBy. Interestingly, this secondary phase's crystal orientation follows the orientation of its surroundings. The different findings in terms of contamination (C and O) and deposition temperature offer valuable insights for further growth optimizing of high-quality epitaxial HfB2 thin films on Si(111) for future GaN-on-Si integration. [ABSTRACT FROM AUTHOR]

The recent discovery of high-temperature superfluorescence in hybrid perovskite thin films has opened new possibilities for harnessing macroscopic quantum phenomena in nanotechnology. This study aimed to elucidate the mechanism that enables high-temperature superfluorescence in these systems. The proposed model describes a quasi-2D Wannier exciton in a thin film that interacts with phonons via the longitudinal optical phonon–exciton Fröhlich interaction. We show that the super-radiant properties of the coherent state in hybrid perovskites are stable against perturbations caused by the longitudinal optical phonon–exciton Fröhlich interaction. Using the multiconfiguration Hartree approach, we derive semiclassical equations of motion for a single-exciton wavefunction, where the vibrational degrees of freedom interact with the Wannier exciton through a mean-field Hartree term. Super-radiance is effectively described by a non-Hermitian term in the Hamiltonian. The analysis was then extended to multiple excited states using the semiclassical Hamiltonian as the basic model. We demonstrate that the ground state of the model exciton Hamiltonian with long-range interactions is a symmetric Dicke super-radiant state, where the Fröhlich interaction is nullified. The additional density matrix-based consideration draws an analogy between this system and stable systems, where the conservation laws determine the nullification of the constant (momentum-independent) decay rate part. In the exciton–phonon system, nullification is associated with the absence of a momentum-independent component in the Wannier exciton–phonon interaction coupling function. [ABSTRACT FROM AUTHOR]

Laser annealing was employed to trigger the solid-state reaction of a thin Co film (2.5 nm) with undoped Si. A metastable disilicide layer was obtained after one laser pulse close to the melt threshold. Its diffraction pattern, relaxed lattice parameter, and residual resisitivity are consistent with the formation of the defective CsCl structure. The CoSi2 phase was found after prolonging the thermal treatment with additional pulses or rapid thermal annealing. Because CoSi is skipped in the phase sequence, CoSi2 layers are more uniform in thickness, have an increased superconductivity and a reduced formation temperature. This approach is compatible with the SALICIDE process and can be used to form smooth contacts in superconducting or regular transistors. [ABSTRACT FROM AUTHOR]

Ge1−xSnx thin films with a Sn content of x ≥ 0.1 present a direct bandgap, which is very interesting for the fabrication of efficient photonic devices. The monostanogermanide phase, Ni(GeSn), is promising to form ohmic contact in GeSn-based Si photonic devices. However, the formation kinetics of Ni stanogermanides and the incorporation of Sn in Ni–GeSn phases are not fully understood. In this work, Ni thin films were deposited on Ge and Ge0.9Sn0.1 layers grown in epitaxy on an Si(100) substrate using magnetron sputtering technique. In situ x-ray diffraction measurements were performed during the solid-state reaction of Ni/Ge and Ni/Ge0.9Sn0.1. 1D finite difference simulations based on the linear parabolic model were performed to determine the kinetics parameters for phase growth. The nucleation and growth kinetics of Ni germanides are modified by the addition of Sn. A delay in the formation of Ni(GeSn) was observed and is probably due to the stress relaxation in the Ni-rich phase. In addition, the thermal stability of the Ni(GeSn) phase is highly affected by Sn segregation. A model was developed to determine the kinetic parameters of Sn segregation in Ni(GeSn). [ABSTRACT FROM AUTHOR]

The effective large signal longitudinal piezoelectric coefficient (d 33 , f ∗) of piezoelectric thin films on rigid substrates has been widely investigated. Unclamped piezoelectric thin films are predicted to have a higher d 33 , f ∗ coefficient due to reduced constraints on piezoelectric strain, domain reorientation, and domain wall motion, but quantitative measurements of this coefficient have been limited. This study uses microfabrication techniques along with double-beam laser interferometry (DBLI) to accurately determine the longitudinal piezoelectric coefficient of Pb(Zr,Ti)O3 thin films in partially released piezomicroelectromechanical structures. A two-step backside release process was used: first, deep reactive ion etching to create backside vias and second, wet etching of the ZnO sacrificial layer to release the area beneath the Pb(Zr,Ti)O3 thin films. Post wet etching, optical profilometry showed concavely deformed diaphragms resulting from asymmetrical stress profiles through the diaphragm thickness. DBLI was then used to examine diaphragm deflection under an applied unipolar voltage ranging from 0 to 10 V. Devices with 50% and 75% of the area beneath the top electrode released exhibited large signal d 33 , f ∗ values of 410 ± 6 and 420 ± 8 pm/V, respectively, more than three times higher than the d 33 , f ∗ value of the clamped samples: 126 ± 13 pm/V. The reasons contributing to the large d 33 , f ∗ include (i) the change in stress levels due to the release process, (ii) the elimination of mechanical constraints from substrate clamping, and (iii) enhanced domain reorientation. These findings confirm that substrate declamping significantly boosts the piezoelectric coefficient, bringing d 33 , f ∗ closer to the bulk longitudinal piezoelectric coefficient (d33). [ABSTRACT FROM AUTHOR]

We report the effect of thickness and width on the spin wave transport and dispersion characteristics of permalloy (Py) microstripes using analytical calculations and experiments. Py waveguides with widths ranging from 2 to 4 μm were fabricated for two different thicknesses: 5 and 20 nm. Our results show a notable increase in the group velocity of spin waves with greater thickness, showing a fourfold rise as the thickness increases. Additionally, the accessible frequency range expands from 0.6 to 2.5 GHz as the thickness increases. We find that the spin wave mode frequency is affected by both thickness and width, with a frequency shift of approximately 0.2 GHz observed when the width increases from 2 to 4 μm. Moreover, spin waves decay more rapidly in thinner films, with the decay length of 20 nm-thick waveguides being four times longer than that of 5 nm-thick waveguides. Thicker and wider waveguides provide a longer decay length, facilitating the transmission of information over longer distances without significant energy loss. Our study offers an understanding of the spin wave propagation in microstrip waveguides and its potential in the development of future magnonic devices. [ABSTRACT FROM AUTHOR]

The hydrodynamics of thin films is typically described using macroscopic models whose connection to the microscopic particle dynamics is a subject of ongoing research. Existing methods based on density functional theory provide a good description of static thin films but are not sufficient for understanding nonequilibrium dynamics. In this work, we present a microscopic derivation of the thin film equation using the Mori–Zwanzig projection operator formalism. This method allows to directly obtain the correct gradient dynamics structure along with microscopic expressions for mobility and free energy. Our results are verified against molecular dynamics simulations for both simple fluids and polymers. [ABSTRACT FROM AUTHOR]

Thin-film confinement of self-assembling block polymers results in materials with myriad potential applications—including membranes and optical devices—and provides design parameters for altering phase behavior that are not available in the bulk, namely, film thickness and preferential wetting. However, most research has been limited to lamella- and cylinder-forming polymers; three-dimensional phases, such as double gyroid (DG), have been observed in thin films, but their phase behavior under confinement is not yet well understood. We use self-consistent field theory to predict the equilibrium morphology of bulk-gyroid-forming AB diblock polymers under thin-film confinement. Phase diagrams reveal that the (211) orientation of DG, often observed in experiments, is stable between nonpreferential boundaries at thicknesses as small as 1.2 times the bulk DG lattice parameter. The (001) orientation is stable between modestly B-preferential boundaries, where B is the majority block, while a different (211)-oriented termination plane is stabilized by strongly B-preferential boundaries, neither of which has been observed experimentally. We then describe two particularly important phenomena for explaining the phase behavior of DG thin films at low film thicknesses. The first is "constructive interference," which arises when distortions due to the top and bottom boundaries overlap and is significant for certain DG orientations. The second is a symmetry-dependent, in-plane unit-cell distortion that arises because the distorted morphology near the boundary has a different preferred unit-cell size and shape than the bulk. These results provide a thermodynamic portrait of the phase behavior of DG thin films. [ABSTRACT FROM AUTHOR]

In this paper, we explored the resistivity behavior of Sb7Se3 thin films on flexible mica. The films maintained their resistance characteristics through various thicknesses and bending cycles. With increasing bends, resistivity and phase transition temperature of both amorphous and crystalline states rose, while the resistance drift coefficient gradually increased. Raman and near infrared experiments confirmed the internal structural changes and bandgap enhancement after bending. Transmission electron microscopy showed enhanced crystallization and uniform element distribution after annealing. Atomic force microscopy observed cracks, explaining the property changes. Additionally, we developed a flexible Sb7Se3 thin-film resistive device with swift reversibility (∼10 ns) regardless of bending, opening new avenues for flexible information storage. [ABSTRACT FROM AUTHOR]

The present work reports the effects of 120 MeV Au9+ on structural and electronic properties of polycrystalline SnO2 films of about 170 nm thickness prepared by spin-coating. 119Sn Mössbauer measurements are used to probe the electronic properties. The observed isomer-shift values clearly indicate Sn4+ for the pristine sample and its progressive reduction to Sn2+ and eventually to the metallic Sn state at higher fluence values. These observations are corroborated by x-ray diffraction, Raman, and x-ray photo-electron spectroscopy measurements. The x-ray diffraction measurements indicate the complete amorphization of the tin oxide phase, while the recrystallization of the metallic Sn phase with irradiation. The optical bandgap is observed to vary with ion beam irradiation. The observations indicate the possibility of tuning the electronic configuration of Sn in tin oxide thin films with swift heavy ion beam irradiation, and the results are explained in terms of the thermal-spike model of swift heavy ion irradiation. [ABSTRACT FROM AUTHOR]

Stability and precision of atomic devices are closely tied to the quality and stability of the internal atmosphere of the atomic vapor cells on which they rely. Such an atmosphere can be stabilized by building the cell with low permeation materials such as sapphire or aluminosilicate glass in microfabricated devices. Recently, we have shown that permeation barriers made of Al 2 O 3 thin-film coatings deposited on standard borosilicate glass could be an alternative for buffer gas pressure stabilization. In this study, we, hence, investigate how helium permeation is influenced by the thickness, ranging from 5 to 40 nm, of such Al 2 O 3 thin films coated by atomic layer deposition. Permeation rates are derived from long-term measurements of the pressure-shifted transition frequency of a coherent population trapping (CPT) atomic clock. From thicknesses of 20 nm onward, a significant enhancement of the cell hermeticity is experienced, corresponding to two orders of magnitude lower helium permeation rate. In addition, we test cesium vapor cells filled with neon as a buffer gas and whose windows are coated with 20 nm of Al 2 O 3. As for helium, the permeation rate of neon is significantly reduced, thanks to alumina coatings, leading to a fractional frequency stability of 4 × 10 − 12 at 1 day when the cell is used in a CPT clock. These features outperform the typical performances of uncoated Cs–Ne borosilicate cells and highlight the significance of Al 2 O 3 coatings for buffer gas pressure stabilization. [ABSTRACT FROM AUTHOR]

The structural relaxation dynamics of conventionally prepared bulk glass of N,N′-bis(3-methylphenyl)-N,N′-diphenyl-benzidine (TPD) was measured by differential scanning calorimetry. The calorimetric data were quantitatively described in terms of the Tool–Narayanaswamy–Moynihan (TNM) model. The TNM parameters were evaluated using a combination of linearization and non-linear optimization methodologies: h*/R = 109.5 kK, ln(A/s) = −321, β = 0.37, x = 0.64. In addition, the TNM phenomenology was used to describe recently reported normalized thickness data of stable and aged thin TPD films measured by ellipsometry. The structural relaxation was found to proceed at a markedly higher rate in these thin films prepared by the physical vapor deposition compared to that of conventional bulk glass. This feature appears to be associated with the significantly narrower distribution of relaxation times (β ≅ 0.8) observed for stable thin film in "as-deposited" form with uniquely dense molecular packing. Interestingly, very similar attributes of the relaxation kinetics were also found in the aged thin film with a previously erased thermal history associated with the deposition. [ABSTRACT FROM AUTHOR]

Stochastic lattice-gas models provide the natural framework for analysis of the surface diffusion-mediated evolution of crystalline metal nanostructures on the appropriate time scale (often 101–104 s) and length scale. Model behavior can be precisely assessed by kinetic Monte Carlo simulation, typically incorporating a rejection-free algorithm to efficiently handle the broad range of Arrhenius rates for hopping of surface atoms. The model should realistically prescribe these rates, or the associated barriers, for a diversity of local surface environments. However, commonly used generic choices for barriers fail, even qualitatively, to simultaneously describe diffusion for different low-index facets, for terrace vs step edge diffusion, etc. We introduce an alternative Unconventional Interaction–Conventional Interaction formalism to prescribe these barriers, which, even with few parameters, can realistically capture most aspects of behavior. The model is illustrated for single-component fcc metal systems, mainly for the case of Ag. It is quite versatile and can be applied to describe both the post-deposition evolution of 2D nanostructures in homoepitaxial thin films (e.g., reshaping and coalescence of 2D islands) and the post-synthesis evolution of 3D nanocrystals (e.g., reshaping of nanocrystals synthesized with various faceted non-equilibrium shapes back to 3D equilibrium Wulff shapes). [ABSTRACT FROM AUTHOR]

A series of topological insulators (TIs) based saturable absorbers (SAs), e.g., Bi2Se3, Bi2SeTe2, and Bi4Br4, are confirmed to exhibit excellent non-linear optical response due to the topological edge states. Here, we demonstrate how a topological crystalline insulator, SnTe thin films, can be prepared on highly oriented pyrolytic graphite and gold-plated mirrors through molecular beam epitaxy. SnTe-SAs incorporated into Er-doped fiber lasers exhibit a large modulation depth of 27.2% and accomplish mode-locking at 1558 nm with a pulse width of 319 fs, indicating preeminent nonlinear optical performance among the reported TI-based SAs. This work illuminates the preparation of SnTe thin films and demonstrates the great potential of SnTe films in ultrafast optical devices. [ABSTRACT FROM AUTHOR]

This work studies the influence of the adsorbed layer on the glass transition of thin films of polysulfone. Therefore, the growth kinetics of the irreversibly adsorbed layer of polysulfone on silicon substrates was first investigated using the solvent leaching approach, and the thickness of the remaining layer was measured with atomic force microscopy. Annealing conditions before leaching were varied in temperature and time (0–336 h). The growth kinetics showed three distinct regions: a pre-growth step where it was assumed that phenyl rings align parallel to the substrate at the shortest annealing times, a linear growth region, and a crossover from linear to logarithmic growth observed at higher temperatures for the longest annealing times. No signs of desorption were observed, pointing to the formation of a strongly adsorbed layer. Second, the glass transition of thin polysulfone films was studied in dependence on the film thickness using spectroscopic ellipsometry. Three annealing conditions were compared: two with only a tightly bound layer formed in the linear growth regime and one with both tightly bound and loosely adsorbed layers formed in the logarithmic growth regime. The onset thickness and increase in the glass transition temperature increases with annealing time and temperature. These differences were attributed to the distinct conformations of the formed adsorbed layers. [ABSTRACT FROM AUTHOR]

Ge1−xSnx and Si1−x−yGeySnx alloys are promising materials for future opto- and nanoelectronics applications. These alloys enable effective bandgap engineering, broad adjustability of their lattice parameter, exhibit much higher carrier mobility than pure Si, and are compatible with the complementary metal-oxide-semiconductor technology. Unfortunately, the equilibrium solid solubility of Sn in Si1−xGex is less than 1% and the pseudomorphic growth of Si1−x−yGeySnx on Ge or Si can cause in-plane compressive strain in the grown layer, degrading the superior properties of these alloys. Therefore, post-growth strain engineering by ultrafast non-equilibrium thermal treatments like pulse laser annealing (PLA) is needed to improve the layer quality. In this article, Ge0.94Sn0.06 and Si0.14Ge0.8Sn0.06 thin films grown on silicon-on-insulator substrates by molecular beam epitaxy were post-growth thermally treated by PLA. The material is analyzed before and after the thermal treatments by transmission electron microscopy, x-ray diffraction (XRD), Rutherford backscattering spectrometry, secondary ion mass spectrometry, and Hall-effect measurements. It is shown that after annealing, the material is single-crystalline with improved crystallinity than the as-grown layer. This is reflected in a significantly increased XRD reflection intensity, well-ordered atomic pillars, and increased active carrier concentrations up to 4 × 1019 cm−3. [ABSTRACT FROM AUTHOR]

To study the effect of large area uniform garnet film on the consistency of image quality of a magneto-optical imaging system, the effect of lattice mismatch on a large area uniform domain structure of magneto-optical materials was studied. In this paper, (BiTm)3(GaFe)5O12 thin garnet films with different stress were prepared on the surface of gadolinium gallium garnet by liquid phase epitaxy. The results show that the magnetic hysteresis mechanism exists in the (BiTm)3(GaFe)5O12 thin films with tensile stress, and the domains can preferentially respond to magnetic signals in very small regions. This is mainly the phenomenon of magnetic domain partitioning caused by cracks. In addition, the non-uniform distribution of coercive force in a large range is the main cause of hysteresis. The thin films with weak compressive stress (BiTm)3(GaFe)5O12 are uniformly distributed over a large area. [ABSTRACT FROM AUTHOR]

Strain can significantly affect the electronic structure and functional properties of dilute magnetic semiconductors. As a wide bandgap transparent semiconductor, doped In2O3 has also received extensive attention for the modulation of physical properties by lattice strain due to its excellent functional properties. Here, we epitaxially grew the Cr:In2O3 thin film on the (111)-oriented 0.7Pb(Mg1/3Nb2/3)O3–0.3PbTiO3 (PMN–PT) ferroelectric single-crystal substrate. By applying an electric field to PMN–PT, multiple reversible and nonvolatile resistance states can be achieved at room temperature. Utilizing in situ XRD, different strain states corresponding to different resistance states induced by the ferroelastic domain switching of the PMN–PT were characterized. Based on first-principles calculations, the influence of lattice strain on the resistivity of the Cr:In2O3 was discussed. These results offer a route for the design of multiple-valued nonvolatile memory devices and multiple functional magneto-electric devices based on dilute magnetic semiconductors. [ABSTRACT FROM AUTHOR]

We present a detailed study on the effects of oxygen on the photoluminescence properties of CdSe/CdS quantum dots (QDs). We investigated the role of oxygen by performing confocal measurements on thin films as well as on single particles while rapidly exchanging the gaseous environment between oxygen and an inert gas atmosphere. We found that the deionization of negatively charged particles by oxygen depends on both the excitation power and the shell thickness of the QDs. For QDs with thin shells, which exhibit strong photoluminescence blinking, we observed that the presence of oxygen affects both band-edge carrier blinking and hot-carrier blinking. [ABSTRACT FROM AUTHOR]

Low-damping magnetic insulators like LiFe5O8 have gained considerable attention in recent years for their exceptional properties such as low energy loss and high gyromagnetic ratio, making them suitable in microwave and spintronic fields. However, due to factors such as crystalline quality and stress, the damping behavior of LiFe5O8 thin films falls below expectations. In this work, we utilize miscut substrate to modulate the structure and magnetic properties of LiFe5O8 films. We found that miscut angles can improve the crystalline quality of the film. However, a miscut angle of 6° resulted in a phase transition from tetragonal to orthorhombic in the LiFe5O8 phase. In particular, the out-of-plane ferromagnetic resonance linewidth of the orthorhombic LiFe5O8 (LFO) film was significantly reduced compared to that of the tetragonal LFO film on a non-miscut substrate, which could be attributed to the structural change. The orthorhombic LFO film also exhibited lower damping and a higher in-plane remanence ratio, indicating superior microwave magnetic properties. These findings suggest that miscut strain could be a viable method for improving the microwave magnetism of LFO films. [ABSTRACT FROM AUTHOR]

Herein, we report epitaxial growth of p-type Ni doped gallium chromium oxide thin film on Al2O3 substrates and studied its band alignment properties with that of the substrate. Thin films are grown using the magnetron-sputtering technique. Synchrotron-based XRD measurements, performed in the coplanar and non-coplanar geometries, confirm high-quality single domain epitaxial growth of p-type α-GaCrO3:Ni. Pendellosung oscillations around the Bragg peak and transmission electron microscopy reveal the high interfacial quality of p-type α-GaCrO3:Ni films with the substrate. Thin film, thickness ∼200 nm, shows around 70% average transmission. The values of valence band and conduction band offsets are determined to be 2.79 ± 0.2 and 0.51 ± 0.2 eV, respectively, which confirm straddling gap band alignment at the heterojunction. This type of alignment creates a threshold barrier for the selective charge carriers and is useful in enhancing the performance of a wide range of devices, including UV photodetectors, metal oxide semiconductor high electron mobility transistors, and light emitters. [ABSTRACT FROM AUTHOR]

Pristine and dysprosium-doped ZnO thin films, highly c-axis oriented, were grown on a c-Al2O3 substrate using the pulsed laser deposition technique. During the deposition process, the growth was impacted by changes in the oxygen partial pressure. The structural, optical, and compositional properties of the pristine and dysprosium-doped ZnO thin films were systematically characterized using various state-of-the-art experimental techniques. The crystallinity associated with these films was observed to be highly dependent on the oxygen partial pressure maintained during the growth process. An average optical transparency of more than ∼90% in the visible spectral range (i.e., 400–800 nm) was observed for all specimens. For doped specimens, expected intra-4fn emissions of (dysprosium) Dy3+ ions that emanated from the 4F9/2 energy state were observed in room-temperature photoluminescence spectra under direct excitation. The Jacobian-transformed wavelength-to-energy plot for Dy-doped ZnO thin films in the UV-Visible region revealed intriguing findings. Specifically, it depicted a prominent peak at 2.82 eV, indicative of the energy state of Dy3+ ions, alongside intense band-edge emission and various defect-related emissions. The intensity of these transitions was observed to depend on the oxygen partial pressure kept during deposition. An x-ray photoelectron spectroscopy analysis of the doped specimen confirmed the +3 oxidation state of dysprosium into the ZnO matrix. These results provide a promising approach for controlling the doping and growth strategy of Dy-doped ZnO thin films, thereby opening up a wide range of applications and enhancement for next-generation optoelectronic devices. [ABSTRACT FROM AUTHOR]

Ultrathin (1–4 nm) films of wide-bandgap semiconductors are important to many applications in microelectronics, and the film properties can be sensitively affected by defects especially at the substrate/film interface. Motivated by this, an in vacuo atomic layer deposition (ALD) was developed for the synthesis of ultrathin films of Ga2O3/Al2O3 atomic layer stacks (ALSs) on Al electrodes. It is found that the Ga2O3/Al2O3 ALS can form an interface with the Al electrode with negligible interfacial defects under the optimal ALD condition whether the starting atomic layer is Ga2O3 or Al2O3. Such an interface is the key to achieving an optimal and tunable electronic structure and dielectric properties in Ga2O3/Al2O3 ALS ultrathin films. In situ scanning tunneling spectroscopy confirms that the electronic structure of Ga2O3/Al2O3 ALS can have tunable bandgaps (Eg) between ∼2.0 eV for 100% Ga2O3 and ∼3.4 eV for 100% Al2O3. With variable ratios of Ga:Al, the measured Eg exhibits significant non-linearity, agreeing with the density functional theory simulation, and tunable carrier concentration. Furthermore, the dielectric constant ε of ultrathin Ga2O3/Al2O3 ALS capacitors is tunable through the variation in the ratio of the constituent Ga2O3 and Al2O3 atomic layer numbers from 9.83 for 100% Ga2O3 to 8.28 for 100% Al2O3. The high ɛ leads to excellent effective oxide thickness ∼1.7–2.1 nm for the ultrathin Ga2O3/Al2O3 ALS, which is comparable to that of high-K dielectric materials. [ABSTRACT FROM AUTHOR]