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This study introduces a method for creating Ohmic contacts to tin oxide (SnO2) by subjecting the sample surface to hydrogen plasma treatment at moderate temperatures of about 300 °C. This process generates a surface layer of metallic tin droplets, forming suitable electrical contacts. The contacts exhibit remarkable durability and demonstrate Ohmic behavior down to liquid helium temperatures. [ABSTRACT FROM AUTHOR]

Measuring the temperature dependence of material properties is a standard method for better understanding the microscopic origins for that property. Surprisingly, only a few experimental studies of thermal boundary conductance at high temperatures exist. This lack of high temperature data makes it difficult to evaluate competing theories for how inelastic processes contribute to thermal conductance. To address this, we report time domain thermoreflectance measurements of the thermal boundary conductance for TiN on diamond, silicon-carbide, silicon, and germanium between 120 and 1000 K. In all systems, the interface conductance increases monotonically without stagnating at higher temperatures. For TiN/SiC interfaces, G ranges from 330 to 1000 MW/m2-K, with a room temperature conductance of 750 MW/m2-K. The interface conductance for TiN/diamond ranges from 140 to 950 MW/m2-K. Notably, for all four interfacial systems, the conductance continues to increase with temperature even after all phonon modes in the vibrationally soft material are thermally excited. This observation suggests that inelastic processes are significant contributors to the thermal conductance in all four interfacial systems, regardless of whether the materials forming the interface are vibrationally similar or dissimilar. Our study fills a notable gap in the literature for how interfacial conductance evolves at high temperatures and tests burgeoning theories for the role of inelastic processes in interfacial thermal transport. [ABSTRACT FROM AUTHOR]

The changes in the crystal structure and ferroelectric properties of (Al0.8Sc0.2)N films sandwiched between Pt and TiN electrodes were investigated by subjecting the films to post-heat-treatment at various temperatures up to 600 °C in both H2 and Ar gases. The remanent polarization underwent slight change, whereas the coercive field strengthened by approximately 9% as a result of the post-heat-treatment up to 600 °C irrespective of the atmosphere and electrode material. This change is much smaller than that reported for ferroelectric (Hf,Zr)O2 films as well as for Pb(Zr,Ti)O3 and SrBi2Ta2O9 films for a wide temperature range from 400 to 600 °C and is almost independent of the Pt and TiN electrodes. The high stability of (Al,Sc)N films with both Pt and TiN electrodes under H2 atmosphere is highly promising to stabilize the properties through the device fabrication process. [ABSTRACT FROM AUTHOR]

We have fabricated smooth-surfaced amorphous In2O3:Sn (a-ITO) films at a high temperature of 550 °C, far above the typical crystallization threshold of 150 °C for ITO films. This achievement has been made possible by intentionally introducing N2 into the sputtering atmosphere, which maintains a low N atom incorporation of only a few atomic percent within the films. Positioned within ZONE-T of the Thornton diagram (higher-temperature region characterized by high film density), our method allows the preparation of films with superior film density about 6.96 g/cm3, substantially exceeding the density of 6.58 g/cm3 for conventional a-ITO films fabricated under ZONE-1 (low-temperature region) and approaching the bulk crystal density of In2O3 at 7.12 g/cm3. The films also feature a high carrier density of 5 × 1020 cm−3 and a remarkably low resistivity of 3.5 × 10−4 Ω cm, comparable to those of polycrystalline films. The analysis via vacuum-ultraviolet absorption spectroscopy on N and O atom densities in the plasma suggests that amorphization is primarily caused not by N atoms incorporated in the films but by those temporally adsorbed on the film surface, inhibiting crystal nucleation before eventually desorbing. Our findings will pave the way not only for broader applications of a-ITO films but also for the design of other amorphous materials at temperatures beyond their crystallization points. [ABSTRACT FROM AUTHOR]

Power Schottky barrier diodes (SBDs) face an inherent trade-off between forward conduction loss and reverse blocking capability. This limitation becomes more severe for ultra-wide bandgap (UWBG) SBDs due to the large junction field. A high Schottky barrier is usually required to suppress the reverse leakage current at the price of an increased forward voltage drop (VF). This work demonstrates a Ga2O3 junction barrier Schottky (JBS) diode that employs the embedded p-type NiO grids to move the peak electric field away from the Schottky junction, thereby allowing for the use of an ultra-low barrier TiN Schottky contact. This JBS diode concurrently realizes a low VF of 0.91 V (at forward current of 100 A/cm2) and a high breakdown voltage over 1 kV, with the VF being the lowest in all the reported vertical UWBG power diodes. Based on the device characteristics measured up to 200 °C, we further analyze the power loss of this JBS diode across a wide range of operational duty cycles and temperatures, which is found to outperform the TiN/Ga2O3 SBDs or NiO/Ga2O3 PN diodes. These findings underscore the potential of low-barrier UWBG JBS diodes for high-frequency, high-temperature power electronics applications. [ABSTRACT FROM AUTHOR]

Laser-driven tin plasmas are driving new-generation nanolithography as sources of extreme ultraviolet (EUV) radiation centered at 13.5 nm. A major challenge facing industrial EUV source development is predicting energetic ion debris produced during the plasma expansion that may damage the sensitive EUV channeling multilayer optics. Gaining a detailed understanding of the plasma dynamics and ion acceleration mechanisms in these sources could provide critical insights for designing debris mitigation strategies in future high-power EUV sources. We develop a fully kinetic model of tin-EUV sources using one-dimensional particle-in-cell simulations to study ion debris acceleration, which will be valuable for cross-validation of radiation-hydrodynamic simulations. An inverse-bremsstrahlung heating operator is used to model the interaction of a tin target with an Nd:YAG laser, and thermal conduction is included through a Monte Carlo Coulomb collision operator. While the large-scale evolution is in reasonable agreement with analogous hydrodynamic simulations, the significant timescale for collisional equilibration between electrons and ions allows for the development of prominent two-temperature features. A collimated flow of energetic ions is produced with a spectrum that is significantly enhanced at high energies compared to fluid simulations. The dominant acceleration mechanism is found to be a large-scale electric field supported mainly by the electron pressure gradient, which is enhanced in the kinetic simulations due to the increased electron temperature. We discuss the implications of these results for future modeling of tin-EUV sources and the development of debris mitigation schemes. [ABSTRACT FROM AUTHOR]

Effective cleaning of tin contamination on the collecting mirrors in extreme ultraviolet source is one of the key techniques to improve throughput and cost performance of extreme ultraviolet lithography. Hydrogen radicals produced in hydrogen plasma that is induced by wideband extreme ultraviolet radiation are expected to be utilized for in situ tin contamination cleaning in extreme ultraviolet sources. In this Letter, we clarified absolute density and cleaning ability of the hydrogen radicals produced by intense extreme ultraviolet pulse through ground state population density measurement by laser-induced fluorescence technique. The experimentally obtained radical parameters coincided well with simulation results and collisional radiative model. It was found that the extreme ultraviolet induced plasma was in quasi-steady state with abundant amount of hydrogen radicals in ground state. Further, it was found that the in situ tin contamination cleaning in extreme ultraviolet lithography source would become more practical with increase in operational parameters, such as extreme ultraviolet emission intensity, gas pressure, and radical production cross section. [ABSTRACT FROM AUTHOR]

We investigated the atomic position and the chemical state of an active Sn dopant for Sn-doped β-Ga2O3(001) using x-ray absorption near the edge structure (XANES) and hard x-ray photoelectron spectroscopy. We found that the Sn dopant had only one chemical state, which was a Sn4+ oxidation state. The bond length around the Sn dopant atom became longer due to the relaxation effect after the Sn dopant insertion. Comparison of the experimental and simulated XANES spectra showed that the octahedral Ga substitutional site in the β-Ga2O3(001) is an active Sn dopant site. [ABSTRACT FROM AUTHOR]

Two-dimensional layered metal dichalcogenides have given rise to considerable interest in electronics and optoelectronics fields because of their excellent physical and chemical properties and promising applications. Tin disulfide (SnS2) is an important member of them due to its environment-friendly and resource-rich characteristics. Here, a series of in situ electrical transport experiments and photocurrent measurements under high pressure have been performed to investigate the electrical and opto-electrical properties of 4H-SnS2. With increasing pressure, the electrical resistivity of 4H-SnS2 decrease significantly, leading to a transition from semiconducting to metallic state above 58.6 GPa. The increase in pressure results in a substantial enhancement in photoelectric activity, indicating the extensive potential of utilizing pressure as a trigger for in situ optoelectronic applications. Combined with our previous results of x-ray diffraction and optical absorption at high pressure, pressure-induced structural distortion, bandgap narrowing, metallization, and enhancement of photoelectric activity of 4H-SnS2 are tunable and reversible, which are of great significance for both fundamental research and device design. [ABSTRACT FROM AUTHOR]

The spectral emission rate of yttrium-like tin (Sn11+) is investigated as the typical ion, which has a strong emission of extreme ultra-violet (EUV) light near the wavelength of 13.5 nm. The energy level structure of the tin ion is investigated using the non-relativesitic configuration average model to calculate the population in the local thermodynamic equilibrium, and the spectral structure of the unresolved transition array that has EUV emission is investigated based on the calculated atomic data using the HULLAC code. It is shown that the broad main peak is accompanied by the tail structure for shorter and longer wavelengths, which arises from multiply and inner-shell excited levels. The emission channels that significantly contribute to the spectrum are determined from a convergence analysis. The excited states below the ionization limit with a large population are shown to have a significant contribution to the emission. [ABSTRACT FROM AUTHOR]

We demonstrate the efficient generation of extreme ultraviolet (EUV) light from laser-produced plasma (LPP) driven by 2 μm wavelength laser light as an alternative for 10 μm CO2 gas LPP currently employed in EUV lithography machines for high-volume manufacturing of semiconductor devices. High conversion efficiencies of laser light into "in-band" EUV photons up to 5.0% are achieved by homogeneously heating the plasma that is laser-generated from preshaped tin microdroplet targets. Scaling the laser pulse duration, spot size, and intensity yields a high in-band EUV energy output of up to 12.5 mJ. The EUV emission source size is studied under a similar parameter range and is shown to match typical etendues of EUV optic columns. Our findings make 2 μm LPP a particularly promising candidate to power future EUV nanolithography. [ABSTRACT FROM AUTHOR]

Advancements in state-of-the-art nanolithography technology over the past decade have been raising an ongoing demand for improvement of the power and efficiency of extreme-ultraviolet (EUV) light sources that stand at its heart. This study introduces a double-sided laser illumination scheme aimed at enhancing EUV emission from such a laser-produced Sn plasma source. Using a solid-state laser, experiments were conducted with suspended solid Sn targets of varying thicknesses, evaluating the resulting effect on EUV output intensity. A significant increase in EUV emission to the collection side was observed due to the addition of illumination of the other side, particularly for thinner targets. For targets with thicknesses of 60 and 20 nm, an increase between 50% and 150% in EUV emission was detected in comparison with single-sided illumination. Extrapolating to a long laser pulse that burns through the target, the enhancement is projected to be 17% for a 300 nm thick target. These results highlight a promising way for further improvement of output power and energy efficiency in next-generation EUV light sources. [ABSTRACT FROM AUTHOR]

The doping effect of the Sn atom in indium tin oxide (ITO) plays a crucial role in influencing the epsilon-near-zero (ENZ) behaviors and the related nonlinear optical properties. A ternary (In1−xSnx)2O3 film is fabricated by high-throughput magnetron sputtering technique. The relationship between Sn doping and second harmonic generation (SHG) enhancement is systematically interpreted through comprehensive characterization of structural and optical properties. Significantly, clear microstructural changes associated with different levels of Sn doping are identified by x-ray diffraction and Raman spectroscopy. These changes directly contribute to shifts in the ENZ wavelength (λENZ). The results indicate that the optimal region for SHG enhancement lies within 7.3–10.6 at. % Sn doping. Moreover, it is demonstrated that λENZ can be adjusted by manipulating the formation of electrically inactive defect clusters via Sn substitution at the 24d sites. This study not only provides valuable insight into the mechanism linking Sn doping and SHG enhancement of ITO but also exemplifies the high-throughput exploration of optical functional materials. [ABSTRACT FROM AUTHOR]

GeSn alloys hold great promise as high-performance, low-cost, near- and short-wavelength infrared photodetectors with the potential to replace the relatively expensive and currently market-dominant InGaAs- and InSb-based photodetectors. In this Letter, we demonstrate room-temperature GeSn pn photodetectors fabricated by a complementary metal-oxide-semiconductor compatible process, involving Sn and P ion implantation and flash-lamp annealing prior to device fabrication. The fabrication process enables the alloying of Ge with Sn at concentrations up to 4.5% while maintaining the high-quality single-crystalline structure of the material. This allows us to create Ge0.955Sn0.045 pn photodetectors with a low dark current density of 12.8 mA/cm2 and a relatively high extended responsivity of 0.56 A/W at 1.71 μm. These results pave the way for the implementation of a cost-effective, scalable, and CMOS-compatible short-wavelength infrared detector technology. [ABSTRACT FROM AUTHOR]

Miniaturized in-plane π-type thermoelectric devices composed of p-type Mg2Sn0.8Ge0.2 and n-type Bi layers were prepared by microfabrication techniques. Structural effects on thermoelectric device performance need to be evaluated and optimized to improve device performance and operation. In this study, a rational analysis of the correction of the open-circuit output voltages, output powers, and output power densities by using effective temperature differences was performed, and the effects of device geometries (e.g., the number of π junctions and the cross-sectional area ratio between p- and n-type layers) were determined by comparing different types of in-plane π-type thermoelectric devices. The results revealed that it is crucial to consider the heat transfer loss caused by thermal contact effects in the device and to optimize the structural geometries of the device. Proper structural trends and the effects of the number of p–n pairs on the device performance were observed, which indicated the reasonable device operation of microfabricated in-plane π-type thermoelectric devices. [ABSTRACT FROM AUTHOR]

This work highlights antiferroelectric (AFE) phase stabilizing effect of Bi substitution at the A-site in Pb[(Zr0.7Sn0.3)0.938Ti0.062]O3. The composition Pb0.985Bi0.01(Zr0.7Sn0.3)0.938Ti0.062O3 with 1% Bi substitution lies just outside the morphotropic phase boundary (MPB) toward the AFE side and allows an electric field driven atomic rearrangement for a disordered state. The disorder and randomness introduced through this substitution is seen to impact the electromechanical property like strain, quite drastically (Smax ∼ 0.3%). Keeping the optimal Bi inclusion and Zr: Sn as 70:30, the B-site of Pb0.985Bi0.01[(Zr0.7Sn0.3)xTi1-x]O3, is varied. The system is brought back to MPB for x = 0.933, and strain values of Smax ∼ 0.44% and a remnant strain Srem ∼ 0.27% are obtained for the optimized MPB composition Pb0.985Bi0.01[(Zr0.7Sn0.3)0.933Ti0.067]O3. [ABSTRACT FROM AUTHOR]

Activation of implanted donors into a highly-resistive, nitrogen-doped homoepitaxial β-Ga2O3 has been investigated. Nitrogen acceptors with the concentration of ∼1017 cm−3 were incorporated during epitaxial growth yielding low-doped (net donor concentration <1014 cm−3) films subsequently implanted with Si, Ge, and Sn. Upon Ohmic contact formation to the implanted regions, sheet resistance values of 314, 926, and 1676 Ω/sq were measured at room temperature for the Si-, Ge-, and Sn-implanted samples, respectively. Room temperature Hall measurements resulted in sheet carrier concentrations and Hall mobilities of 2.13 × 1014 /93, 8.58 × 1013/78, and 5.87 × 1013/63 cm2/(V s), respectively, for these three donor species. Secondary ion mass spectroscopy showed a volumetric dopant concentration of approximately 2 × 1019 cm−3 for the three species, resulting in carrier activation efficiencies of 64.7%, 40.3%, and 28.2% for Si, Ge, and Sn, respectively. Temperature-dependent Hall effect measurements ranging from 15 to 300 K showed a nearly constant carrier concentration in the Si-implanted sample, suggesting the formation of an impurity band indicative of degenerate doping. With a bulk carrier concentration of 1.3 × 1019 cm−3 for the Si implanted sample, a room temperature mobility of 93 cm2/(V s) is among the highest reported in Ga2O3 with a similar carrier concentration. The unimplanted Ga2O3:N regions remained highly resistive after the surrounding areas received implant and activation anneal. These results open the pathway for fabricating Ga2O3 devices through the selective n-type doping in highly resistive epitaxial Ga2O3. [ABSTRACT FROM AUTHOR]

In this Letter, we report a demonstration of p-channel tin monoxide (SnO) thin-film transistors (TFTs) with high field-effect mobility (μFE) exceeding 10 cm2/Vs and hysteresis-free like behavior. We demonstrate that maintaining metallic states before encapsulation is a key process to enhance μFE in p-type SnO thin-films. Sustaining this meta-stability involves the following two processes during fabrication: (1) postdeposition annealing (PDA) in two steps and (2) encapsulation in the middle of each PDA. This simple process not only suppresses creation of oxidized states such as adverse Sn4+ but also facilitates the lateral growth of crystals with improved crystallinity by interfacial energy stabilization. The resultant SnO TFT reveals a record-high μFE up to 15.8 cm2/Vs with a negligible hysteresis of 0.1 V. This study suggests a practical route to grant high μFE to p-channel SnO TFTs without any dopant or complex postdeposition treatment. [ABSTRACT FROM AUTHOR]

Two-dimensional layered metal dichalcogenides have attracted extensive attention because of their diverse physical properties and potential applications in electronics and optoelectronics. As an eco-friendly and earth abundant semiconductor, SnS2 displays limited optoelectronic applications due to its large and indirect bandgap. Pressure is a powerful tool to tune crystal structures and physical properties of materials. Here, we systematically investigate the structural stability and optical properties of 4H-SnS2 under high pressure. The crystal structure of 4H-SnS2 is stable up to 56 GPa without structural transition and layer sliding. Continuous lattice contraction is accompanied by gradual bandgap narrowing, which is reversible after releasing pressure. The continuous and reversible modulation of the crystal structure and bandgap on 4H-SnS2 suggest promising optoelectronic applications in the range of visible light based on two-dimensional layered metal dichalcogenides. [ABSTRACT FROM AUTHOR]

β-Ga2O3 is an emerging ultra-wide bandgap semiconductor, holding a tremendous potential for power-switching devices for next-generation high power electronics. The performance of such devices strongly relies on the precise control of electrical properties of β-Ga2O3, which can be achieved by implantation of dopant ions. However, a detailed understanding of the impact of ion implantation on the structure of β-Ga2O3 remains elusive. Here, using aberration-corrected scanning transmission electron microscopy, we investigate the nature of structural damage in ion-implanted β-Ga2O3 and its recovery upon heat treatment with the atomic-scale spatial resolution. We reveal that upon Sn ion implantation, Ga2O3 films undergo a phase transformation from the monoclinic β-phase to the defective cubic spinel γ -phase, which contains high-density antiphase boundaries. Using the planar defect models proposed for the γ -Al2O3, which has the same space group as β-Ga2O3, and atomic-resolution microscopy images, we identify that the observed antiphase boundaries are the {100}1/4 ⟨110⟩ type in cubic structure. We show that post-implantation annealing at 1100 °C under the N2 atmosphere effectively recovers the β-phase; however, nano-sized voids retained within the β-phase structure and a γ -phase surface layer are identified as remanent damage. Our results offer an atomic-scale insight into the structural evolution of β-Ga2O3 under ion implantation and high-temperature annealing, which is key to the optimization of semiconductor processing conditions for relevant device design and the theoretical understanding of defect formation and phase stability. [ABSTRACT FROM AUTHOR]

β-Ga2O3 is an emerging ultra-wide bandgap semiconductor, holding a tremendous potential for power-switching devices for next-generation high power electronics. The performance of such devices strongly relies on the precise control of electrical properties of β-Ga2O3, which can be achieved by implantation of dopant ions. However, a detailed understanding of the impact of ion implantation on the structure of β-Ga2O3 remains elusive. Here, using aberration-corrected scanning transmission electron microscopy, we investigate the nature of structural damage in ion-implanted β-Ga2O3 and its recovery upon heat treatment with the atomic-scale spatial resolution. We reveal that upon Sn ion implantation, Ga2O3 films undergo a phase transformation from the monoclinic β-phase to the defective cubic spinel γ -phase, which contains high-density antiphase boundaries. Using the planar defect models proposed for the γ -Al2O3, which has the same space group as β-Ga2O3, and atomic-resolution microscopy images, we identify that the observed antiphase boundaries are the {100}1/4 ⟨110⟩ type in cubic structure. We show that post-implantation annealing at 1100 °C under the N2 atmosphere effectively recovers the β-phase; however, nano-sized voids retained within the β-phase structure and a γ -phase surface layer are identified as remanent damage. Our results offer an atomic-scale insight into the structural evolution of β-Ga2O3 under ion implantation and high-temperature annealing, which is key to the optimization of semiconductor processing conditions for relevant device design and the theoretical understanding of defect formation and phase stability. [ABSTRACT FROM AUTHOR]

Corundum (AlxGa1−x)2O3 alloys have been proposed as a candidate ultrawide-bandgap oxide for a number of applications, but doping is unexplored. We examine the prospects for n-type doping with H, Si, Ge, Sn, Hf, Zr, and Ta in corundum (AlxGa1−x)2O3 alloys using first-principles calculations. All of the dopants are shallow donors in corundum Ga2O3. In the (AlxGa1−x)2O3 alloy, they transition from shallow to deep donors at Al compositions that are unique to each donor. Si and Hf remain shallow donors up to the highest Al contents in corundum (AlxGa1−x)2O3 alloys and are still shallow even as the (AlxGa1−x)2O3 bandgap exceeds 6.5 eV. Finally, we address the detrimental role of cation vacancies as compensating deep acceptors and suggest that doping in a hydrogen-rich environment under cation-rich conditions can be used to overcome this problem. [ABSTRACT FROM AUTHOR]

Corundum (AlxGa1−x)2O3 alloys have been proposed as a candidate ultrawide-bandgap oxide for a number of applications, but doping is unexplored. We examine the prospects for n-type doping with H, Si, Ge, Sn, Hf, Zr, and Ta in corundum (AlxGa1−x)2O3 alloys using first-principles calculations. All of the dopants are shallow donors in corundum Ga2O3. In the (AlxGa1−x)2O3 alloy, they transition from shallow to deep donors at Al compositions that are unique to each donor. Si and Hf remain shallow donors up to the highest Al contents in corundum (AlxGa1−x)2O3 alloys and are still shallow even as the (AlxGa1−x)2O3 bandgap exceeds 6.5 eV. Finally, we address the detrimental role of cation vacancies as compensating deep acceptors and suggest that doping in a hydrogen-rich environment under cation-rich conditions can be used to overcome this problem. [ABSTRACT FROM AUTHOR]

HfO2-based antiferroelectric-like thin films are increasingly being considered for commercial devices. However, even with initial promise, the temperature sensitivity of electrical properties such as loss tangent and leakage current remains unreported. 50 nm thick, 4 at. % Al-doped HfO2 thin films were synthesized via atomic layer deposition with both top and bottom electrodes being TiN or Pt. A study of their capacitance vs temperature showed that the Pt/Al:HfO2/Pt had a relative dielectric permittivity of 23.30 ± 0.06 at room temperature with a temperature coefficient of capacitance (TCC) of 78 ± 86 ppm/°C, while the TiN/Al:HfO2/TiN had a relative dielectric permittivity of 32.28 ± 0.14 at room temperature with a TCC of 322 ± 41 ppm/°C. The capacitance of both devices varied less than 6% over 1 to 1000 kHz from −125 to 125 °C. Both capacitors maintained loss tangents under 0.03 and leakage current densities of 10−9–10−7 A/cm2 between −125 and 125 °C. The TiN/Al:HfO2/TiN capacitor maintained an energy storage density (ESD) of 18.17 ± 0.79 J/cm3 at an efficiency of 51.79% ± 2.75% over the −125 to 125 °C range. The Pt/Al:HfO2/Pt capacitor also maintained a stable ESD of 9.83 ± 0.26 J/cm3 with an efficiency of 62.87% ± 3.00% over the same temperature range. Such low losses in both capacitors along with their thermal stability make antiferroelectric-like, Al-doped HfO2 thin films a promising material for temperature-stable microelectronics. [ABSTRACT FROM AUTHOR]

The Sn composition graded GeSn layer with Sn content increased from 11% to 14.3% was grown on a Si substrate by molecular beam epitaxy. The structural properties of the GeSn layer are investigated, and the film is gradually relaxed along the thickness, reaching approximately 71.6%. The GeSn p–i–n detectors were fabricated by using a complementary metal oxide semiconductor compatible process. The GeSn detectors demonstrated a cutoff wavelength of approximately 3.3 μm at room temperature with a dark current of 0.3 A/cm2 @ -1 V. At a wavelength of 2000 nm, the GeSn detectors had a responsivity of 110 mA/W and -3 dB bandwidth (f3 dB) about 3 GHz. These results suggest that high Sn content relax GeSn can be grown by MBE and paves the way toward the feasibility of mid-infrared GeSn photonics. [ABSTRACT FROM AUTHOR]

GeSn alloys are promising materials for light emitters monolithically grown on silicon. In this work, we demonstrate room temperature (RT) lasing in a GeSn hetero-structure with 17.2% of Sn. We report a threshold of 3.27 MW c m − 2 at 305 K with peak emission at 353 meV. We ascribe these improvements to a higher tin concentration in the GeSn active layer with lower Sn content barriers on each side and to a better thermal dissipation provided by an adapted pedestal architecture beneath the GeSn micro-disk. This outcome is a major milestone for a fully integrated group-IV semiconductor laser on Si. [ABSTRACT FROM AUTHOR]

The dielectric functions of germanium–tin alloy thin-films, deposited by molecular beam epitaxy on bulk Ge substrates, with relatively high Sn contents from 15 to 27 at. %, were measured by variable angle spectroscopic ellipsometry over the wavelength range from 0.190 to 6 μm, using a combination of ultraviolet-visible and infrared ellipsometers. The band structure critical point energies, specifically the E1 and E1+ Δ1 optical transitions, were extracted from the measurements by a method of parametric oscillator modeling and second derivative analysis. With increasing Sn content, the transitions shifted to lower energies, and for alloys with less than 20% Sn, the numerical values agreed reasonably with predictions based on deformation potential theory that accounted for film strain. For the higher Sn alloys, the critical point energies from measurements agreed less well with deformation potential theory. These results provide information on the band structure of GeSn alloys with high Sn contents, which are increasingly important for long-wave infrared devices and applications. [ABSTRACT FROM AUTHOR]

Quasi-two-dimensional organic–inorganic hybrid halide perovskite materials have attracted extensive attention in the field of optoelectronic devices owing to their unique photoelectric properties. However, lead toxicity greatly hinders their practical applications. Using environmentally friendly elements to substitute lead is an effective solution, but even worse stability and photoelectric performance pose a great challenge for further device fabrication. Here, high-performance lead-free photodetectors (PDs) are developed based on a BA2FAn-1SnnI3n+1 (n = 1, 2) film via a one-step spin coating method. The films could be stable for two to three hours in ambient conditions. The devices show the dark current of 2.1 × 10−9 (n = 1) and 2.6 × 10−9 A (n = 2), the on/off ratio of 458 (n = 1) and 1108 (n = 2), and the detectivity of 1.46 × 1013 (n = 1) and 6.23 × 1012 Jones (n = 2), which were outstanding in the reported Sn-based PDs. The excellent performance is attributed to the low Sn4+ self-doping realized by adding Sn powder and SnF2 in a precursor solution in the synthesis process and the high-performance optoelectronic properties of FA-based perovskite. This study demonstrates that BA2FAn-1SnnI3n+1 is a promising material for photovoltaic devices. [ABSTRACT FROM AUTHOR]

InP channel planar and vertical MOSFETs utilizing atomic layer deposition of a TiN/Ru gate are fabricated. The performance of the TiN/Ru gate is compared to a Ru-only gate based on the C–V characteristics of MOS (metal–oxide–semiconductor) capacitors and peak transconductance ( g m ) and subthreshold swing (SS) in planar MOSFETs. Compared to devices with the conventional Ni/Au gate metal, these have a 70 mV/dec SS [Tseng et al., in Device Research Conference (IEEE, 2019), pp. 183–184.] and a long gate length; TiN/Ru gate devices exhibit an average 68 mV/dec SS , a record low value of InP, suggesting a high quality, low-damage high-k/InP interface. A record high peak g m of 0.75 mS/μm at V D S = 0.6 V on an InP channel is achieved in a planar gate length ( L g) = 80 nm device. A vertical MOSFET shows a reasonably conformal Ru coverage of the vertical fin and a high 0.42 mS/μm peak g m for a L g = 50 nm device. The results of planar and vertical MOSFETs show that TiN/Ru gate metallization via atomic layer deposition is promising for non-planar III–V MOS devices. [ABSTRACT FROM AUTHOR]

Density functional calculations are carried out to study the symmetry and substitution-driven electronic phase transition in BaPb1−xSnxO3. Two end members, BaSnO3 and BaPbO3, are found to be insulating and metallic, respectively. In the latter case, the metallicity arises with the presence of an electron pocket, formed by Pb-s dominated conduction band edge, and a hole pocket formed by O-p dominated valence bands. While electron carriers are found to be highly mobile, the hole carriers are localized. Our study reveals that an insulating phase can be realized in the metallic cubic BaPbO3 in three ways in order to explore optoelectronic properties: first, by lowering the symmetry of the lattice to monoclinic through rotation and tilting of the PbO6 octahedra; second, by hydrostatic pressure; and third, by alloying with Sn substitution. The presence of soft phonon modes implies the plausibility of symmetry lowering structural transitions. Furthermore, unlike the earlier reports, we find that Sn substituted BaPbO3 cannot exhibit the topological insulator phase due to the absence of the band inversion. [ABSTRACT FROM AUTHOR]

Epitaxial SrRu1−xSnxO3 (0 ≤ x ≤ 1) thin films were deposited on SrTiO3 (001) substrates by sequential two-target synthesis using pulsed laser deposition to achieve stable phases in this family of quaternary perovskites. The SrRu1−xSnxO3 films exhibit a good crystalline quality, a sharp interface between film and substrate, and an atomically smooth surface. A gradual expansion of the c-axis lattice parameter was observed with Sn doping serving as a means to tune chemical pressure and magnetism. With an increase in Sn doping, the resistivity of the film increased, and the ferromagnetism decreased. These results illustrate use of lattice engineering, e.g., tuning of c-axis lattice parameter with chemical doping, to control electronic and magnetic properties of epitaxial thin films for applications in oxide electronics. [ABSTRACT FROM AUTHOR]

We report the application of a coordination polymer semiconductor, tin(II) thiocyanate [Sn(SCN)2], as an ultrathin anode interlayer in organic photovoltaics (OPVs). Sub-10 nm layers of Sn(SCN)2 with high smoothness and excellent transparency having an optical bandgap of 3.9 eV were deposited from an alcohol-based solution at room temperature without post-deposition annealing. Inserting Sn(SCN)2 as an anode interlayer in polymer:fullerene OPVs drastically reduces the recombination loss due to the exciton-blocking energy levels of Sn(SCN)2. At the optimum thickness of 7 nm, an average power conversion efficiency (PCE) of 7.6% and a maximum of 8.1% were obtained. The simple processability using common solvents gives Sn(SCN)2 a distinct advantage over the more well-known copper(I) thiocyanate (CuSCN). The electronic and optical properties of Sn(SCN)2 make it interesting for applications in large-area electronic devices. [ABSTRACT FROM AUTHOR]

While fabricating tin (Sn)-based perovskite solar cells (PSCs), it is beneficial to tune the bandgap of the perovskite absorber layer by changing the ratio of halide ions, for improved performance. However, oxidation limits the power conversion efficiency (PCE) [Jeon et al., Nat. Mater. 13, 897 (2014); Ke et al., ACS Energy Lett. 3, 1470 (2018); Yang et al., Adv. Energy Mater. 10, 1902584 (2020); Baig et al., Optik 170, 463 (2018)]. Herein, we introduced Catechin into the perovskite layer to suppress oxidation. We achieved FA0.75MA0.25SnI2Br thin films with a low Sn4+ ratio. Owing to Catechin doping, devices yielded an average PCE of 5.45% and a Champion PCE of 6.02%, higher than the average PCE of 4.29% for the device without Catechin doping. Furthermore, the stability of the doped device improved. It also exhibited dramatic performance when exposed to indoor lighting with the maximum PCE approaching 12.81% under 1000 lx. This work further advances the field of lead-free PSCs and the potential of indoor photovoltaics. [ABSTRACT FROM AUTHOR]

Oxidation of TiN is a diffusion-limited process due to the high stability of the TiN metallic state at the TiN/TiO2 junction. Hence, the TiN/TiO2/TiN device being the inability to form a suitable interfacial layer results in the exhibition of abrupt current (conductance) rise and fall during the set (potentiation) and reset (depression) processes, respectively. Interfacial engineering by depositing Ti film served as the oxygen gettering material on top of the TiO2 layer induces a spontaneous reaction to form a TiOx interfacial layer (due to the low Gibbs free energy of suboxide formation). Such an interface layer acts as an oxygen reservoir that promotes gradual oxidation and reduction during the set and reset processes. Consequently, an excellent analog behavior having a 2-bit per cell and robust epoch training can be achieved. However, a thick interfacial layer may degrade the switching behavior of the device due to the high internal resistance. This work suggests that interfacial engineering could be considered in designing high-performance analog memristor devices. [ABSTRACT FROM AUTHOR]

The development of high-performance lead-free perovskite solar cells (PSCs) is important to address the environmental concern of lead perovskite. In recent years, tin perovskite solar cells (TPSCs) have been developing quickly and emerging as a promising candidate for high-efficiency lead-free PSCs. In this Perspective, we summarize recent work of our group including the use of a low-dimensional structure, film growth kinetic control, and device engineering. In the end, the challenges in TPSCs and potential strategies toward high-efficiency TPSCs are discussed. [ABSTRACT FROM AUTHOR]

Ferroelectric Hf0.5Zr0.5O2 (HZO) films were grown by the atomic layer deposition (ALD) technique on an ALD or physical-vapor-deposited (PVD, sputtering) TiN bottom electrode (BE). The PVD TiN film showed small grains with flat surface morphology, mainly consisting of the (111) crystallographic plane. In contrast, the ALD TiN film exhibited a larger diameter and faceted grain shapes, with the (200) crystallographic surface planes. The 10-nm-thick HZO film on the ALD TiN BE showed a lower internal field, enhanced endurance (>1 × 1010 cycle at 2.5 MV/cm), and decreased leakage current than identical HZO films on the PVD TiN BE. Lower interfacial oxidation of the ALD TiN BE as a result of the smaller grain boundary area of the ALD TiN induced a lower defect density in the HZO film. The higher work function of the ALD TiN film also contributed to the lowering of the leakage current. [ABSTRACT FROM AUTHOR]

We report the electrical properties of zinc tin nitride (Zn1+xSn1-xN2) thin films grown by reactive sputtering in an ultrahigh vacuum chamber. It is demonstrated that both the Zn-rich content and low-temperature growth are beneficial for suppressing the carrier concentration. Nondegenerate thin films with a composition of Zn/(Zn+Sn) = 0.72 show the carrier concentration of 2.7 × 1017 cm−3 at 300 K and the activation energy of 0.14 eV, which are in contrast to previously formed degenerate thin films with a much higher carrier concentration. Such electrical properties are consistent with the recent first-principles calculation, suggesting that excess Zn can reduce the amount of native donor-type Sn-on-Zn (SnZn2+) defects, while low-temperature growth can decrease the concentrations of unintentional donor-type oxygen-on-nitrogen (ON+) and/or hydrogen interstitial (Hi+) impurities. These results could provide a general framework for controlling the carrier concentration in II-IV-nitride semiconductors. [ABSTRACT FROM AUTHOR]

In this study, we demonstrate intense extreme-ultraviolet optical vortices generated using laser-ablation plume as the nonlinear medium. We used two types of plumes that are known to generate intense high-order harmonics for driving lasers with Gaussian beam profiles, but through different mechanisms, namely, carbon (diatomic carbon molecules) and tin (resonance with the autoionizing state). We find that the harmonic fluxes for diatomic carbon molecules are similar for Gaussian and vortex driving fields. However, for harmonics from the autoionizing state of tin (∼26.3 eV), the enhancement factor of the resonant harmonic intensity decreases by ∼50% when using the vortex driving field. The intense extreme-ultraviolet optical vortices demonstrated in this study will be useful for many applications including a material characterization technique known as optical angular momentum dichroism as well as the spectroscopy of spin-forbidden electronic transitions. [ABSTRACT FROM AUTHOR]

The impact of different interfacial layers (ILs) on the electrical performances of Au/Ti/HfO2/Ge0.9Sn0.1 metal oxide semiconductor (MOS) capacitors is studied. Parallel angle resolved x-ray photoelectron spectroscopy measurements show that germanium diffuses into the HfO2 layer when no IL is used. This results in an increase in the tin content at the interface and a high interface state density. We demonstrate that the use of an IL prevents germanium and HfO2 intermixing and improves the electrical performance of MOS capacitors. Several ILs are studied such as alumina (Al2O3) and plasma oxidized GeSn (GeSnOx) prior to HfO2 deposition. C–V measurements correlated with simulations made by a customized analytical model indicate an interface state density of 5 × 1011 eV−1 cm−2 for the HfO2/GeSnOx/Ge0.9Sn0.1 gate stack. This result is promising for the integration of high mobility GeSn channels in CMOS devices. [ABSTRACT FROM AUTHOR]

Recently, two stable allotropes (germancite and stancite) for the group IV elements (Ge and Sn) with a staggered layered dumbell structure were proposed to be three-dimensional (3D) topological Dirac semimetals [Phys. Rev. B 93, 241117 (2016)]. A pair of Dirac points is on the rotation axis away from the time-reversal invariant momentum, and the stability of the 3D bulk Dirac points is protected by the C3 rotation symmetry. Here, we use the first principles calculations to investigate GexSny alloys which share the same rhombohedral crystal structure with the space group of D 3 d 6 . Six GexSny alloys are predicted to be energetically and dynamically stable, where (x, y) = (8, 6) and (6, 8) and the α and β phases of (10, 4) and (4, 10). Our results demonstrate that all the six GexSny alloys are topological Dirac semimetals. The different nontrivial surface states and surface Fermi arcs are identified. Our work will substantially enrich the family of 3D Dirac semimetals which are within the reach of experimental realization. [ABSTRACT FROM AUTHOR]

The simultaneous control of lattice strain, composition, and microstructure is crucial to establish high-quality, direct bandgap GeSn semiconductors. Herein, we demonstrate that multilayer growth with a gradual increase in composition is an effective process to minimize bulk and surface segregation and eliminate phase separation during epitaxy yielding a uniform Sn incorporation up to ∼18 at. %. Detailed atomistic studies using atom probe tomography reveal the presence of abrupt interfaces between monocrystalline GeSn layers with interfacial widths in the 1.5–2.5 nm range. Statistical analyses of 3-D atom-by-atom maps confirmed the absence of Sn precipitates and short-range atomic ordering. Despite the residual compressive strain of −1.3 %, the grown layers show clear room-temperature photoluminescence in the 3.0–3.5 μm wavelength range originating from the upper GeSn layer with the highest Sn content. This finding lays the groundwork to develop silicon-compatible mid-infrared photonic devices. [ABSTRACT FROM AUTHOR]

Color centers in diamonds have shown promising potential for luminescent thermometry. So far, the nitrogen-vacancy (NV) color center has demonstrated a high sensitivity for optical temperature monitoring in biological systems. However, the NV center requires microwave excitation which can cause unwanted heating, and the NV is also sensitive to non-axial magnetic fields, both of which can result in inaccurate temperature measurements. To overcome this drawback, the silicon-vacancy (SiV) and germanium-vacancy (GeV) color centers in diamonds have recently been explored and have shown good optical temperature sensitivity owing to the temperature dependent wavelength optical zero-phonon line. Here, we report optical temperature measurements using the recently discovered tin-vacancy (SnV) color center in diamond and show sensitivity better than 0.2 K in 10 s integration time. Also, we compare the relative merits of SnV with respect to SiV and GeV for luminescent thermometry. These results illustrate that there are likely to be many future options for nanoscale thermometry using diamonds. [ABSTRACT FROM AUTHOR]

Experimental studies of stopping of ion fluxes from laser-produced plasma by a low-pressure gas atmosphere are presented. A modification of the time-of-flight spectroscopy technique is proposed for the stopping cross-sectional measurements in the ion energy range of 0.1–10 keV. The application of the proposed technique is demonstrated for Sn ion stopping by H2 gas. This combination of elements is of particular importance for the development of plasma-based sources of extreme ultraviolet radiation for lithographic applications. [ABSTRACT FROM AUTHOR]

SnSe is a topical thermoelectric material with a low thermal conductivity which is linked to its unique crystal structure. We use low-temperature heat capacity measurements to demonstrate the presence of two characteristic vibrational energy scales in SnSe with Debye temperatures θD1=345(9) K and θD2=154(2) K. These hard and soft substructures are quantitatively linked to the strong and weak Sn-Se bonds in the crystal structure. The heat capacity model predicts the temperature evolution of the unit cell volume, confirming that this two-substructure model captures the basic thermal properties. Comparison with phonon calculations reveals that the soft substructure is associated with the low energy phonon modes that are responsible for the thermal transport. This suggests that searching for materials containing highly divergent bond distances should be a fruitful route for discovering low thermal conductivity materials. [ABSTRACT FROM AUTHOR]

In this paper, we employed a method that overcomes the known limitations of electron paramagnetic resonance (EPR) to monitor charge trap dynamics over a broad temperature range not normally accessible due to the lifetime broadening of the EPR lines at higher temperatures. This was achieved by measuring the decay of the EPR intensity after thermal annealing by rapid cycling back to low temperatures for the EPR measurement. This technique was used to experimentally demonstrate interesting physics in the form of a direct measurement of the hyperbolic decay 1/(1+t) of a charge trap population, which previously was only considered theoretically. The nontrivial effects of bimolecular recombination are demonstrated in the Sn2S2P6:Sb crystals, providing an explanation of the optical sensitization process observed in photorefractive Sn2P2S6:Sb used for dynamic holography. [ABSTRACT FROM AUTHOR]

To realize the advanced thin-film transistors (TFTs), high-carrier-mobility semiconductor films on insulator structures should be fabricated with low-temperature processing conditions (≤500℃C). To achieve this, we investigated the solid-phase crystallization of amorphous-GeSn films on insulating substrates under a wide range of Sn concentrations (0%-20%), film thicknesses (30-500 nm), and annealing temperatures (380-500℃C). Our results reveal that a Sn concentration close to the solid solubility of Sn in Ge (~2%) is effective in increasing the grain-size of poly-GeSn. In addition, we discovered that the carrier mobility depends on the film thickness, where the mobilities are determined by the counterbalance between two different carrier scattering mechanisms. Here, vacancy-related defects dominate the carrier scattering near the insulating substrates (≤~120 nm), and grain-size determined by bulk nucleation dominates the grain-boundary scattering of thick films (≥~200 nm). Consequently, we obtained the maximum mobilities in samples with a Sn concentration of 2% and a film thickness of 200 nm. The effect of increasing the grain-size of poly-GeSn by lowering the annealing temperature was also clarified. By combining these results, a very high carrier mobility of 320 cm²/Vs was obtained at a low temperature of 380℃C. This mobility is about 2.5 times as high as previously reported data for Ge and GeSn films grown at low temperatures (≤500℃C). Our technique therefore opens up the possibility of high-speed TFTs for use in the next generation of electronics. [ABSTRACT FROM AUTHOR]

The potential of effectively n-type doping Ga2O3 considering its large band gap has made it an attractive target for integration into transistors and solar cells. As a result amorphous GaOx is now attracting interest as an electron transport layer in solar cells despite little information on its optoelectrical properties. Here we present the opto-electronic properties, including optical band gap, electron affinity, and charge carrier density, for amorphous GaOx thin films deposited by pulsed laser deposition. These properties are strongly dependent on the deposition temperature during the deposition process. The deposition temperature has no significant influence on the general structural properties but produces significant changes in the oxygen stoichiometry of the films. The density of the oxygen vacancies is found to be related to the optical band gap of the GaOx layer. It is proposed that the oxygen deficiency leads to defect band below the conduction band minimum that increases the electron affinity. These properties facilitate the use of amorphous GaOx as an electron transport layer in Cu(In,Ga)Se2 and in Cu2O solar cells. Further it is shown that at low deposition temperatures, extrinsic doping with Sn is effective at low Sn concentrations. [ABSTRACT FROM AUTHOR]

The potential of effectively n-type doping Ga2O3 considering its large band gap has made it an attractive target for integration into transistors and solar cells. As a result amorphous GaOx is now attracting interest as an electron transport layer in solar cells despite little information on its optoelectrical properties. Here we present the opto-electronic properties, including optical band gap, electron affinity, and charge carrier density, for amorphous GaOx thin films deposited by pulsed laser deposition. These properties are strongly dependent on the deposition temperature during the deposition process. The deposition temperature has no significant influence on the general structural properties but produces significant changes in the oxygen stoichiometry of the films. The density of the oxygen vacancies is found to be related to the optical band gap of the GaOx layer. It is proposed that the oxygen deficiency leads to defect band below the conduction band minimum that increases the electron affinity. These properties facilitate the use of amorphous GaOx as an electron transport layer in Cu(In,Ga)Se2 and in Cu2O solar cells. Further it is shown that at low deposition temperatures, extrinsic doping with Sn is effective at low Sn concentrations. [ABSTRACT FROM AUTHOR]

Doping activity in both beta-phase (β-) and amorphous (a-) Sn-doped gallium oxide (Ga2O3:Sn) is investigated by X-ray absorption spectroscopy(XAS). A single crystal of β-Ga2O3:Sn grown using edge-defined film-fed growth at 1725°C is compared with amorphous Ga2O3:Sn filmsdeposited at low temperature (<300°C). Our XAS analyses indicate that activated Sn dopant atoms in conductive single crystal β-Ga2O3:Sn are present as Sn4+, preferentially substituting for Ga at the octahedral site, as predicted by theoretical calculations. In contrast, inactive Sn atoms in resistive a-Ga2O3:Sn are present in either +2 or +4 charge states depending on growth conditions. These observations suggest the importance of growing Ga2O3:Sn at high temperature to obtain a crystalline phase and controlling the oxidation state of Sn during growth to achieve dopant activation. [ABSTRACT FROM AUTHOR]

We investigated the impact of introducing an ultra-high Sn content Ge1-xSnx interlayer on the electrical properties at the metal/Ge interface. We achieved epitaxial growth of a Ge1-xSnx thin layer with an ultra-high substitutional Sn content of up to 46% on a Ge(001) substrate by considering the misfit strain between Ge1-xSnx and Ge. From the current-voltage characteristics of Al/ Ge1-xSnx/n-Ge Schottky diodes, we found an increase in the forward current density of the thermionic emission current with increasing Sn content in the Ge1-xSnx interlayer. The Schottky barrier height estimated in Al/Ge1-xSnx/n-Ge diodes decreases to 0.49 eV with an increase in the Sn content up to 46% of the Ge1-xSnx interlayer. The reduction of the barrier height may be due to the shift of the Fermi level pinning position at the metal/Ge interface with a Ge1-xSnx interlayer whose valence band edge is higher than that of Ge. This result enables the effective reduction of the contact resistivity by introducing a group-IV semiconductor alloy interlayer of Ge1-xSnx into the metal/n-Ge interface. [ABSTRACT FROM AUTHOR]